Conditions: Epithelial Ovarian Cancer Peritoneal Cancer Fallopian Tube Cancer
Keywords: Platinum resistant Folate-receptor alpha expression Phase 3 Antibody-drug conjugate mirvetuximab soravtansine IMGN853 Epithelial Ovarian Cancer Peritoneal Cancer Fallopian Tube Cancer MIRV FRα
Allocation: NA | Intervention model: SINGLE_GROUP
Enrollment: 106
Healthy volunteers: no

Brief summary:
This study is designed to evaluate the efficacy and safety of mirvetuximab soravtansine (MIRV) in participants with platinum-resistant high-grade serous epithelial ovarian cancer, primary peritoneal, or fallopian tube cancer, whose tumors express a high-level of Folate Receptor-Alpha (FRα). Participants will be, in the opinion of the Investigator, appropriate for single-agent therapy for their next line of therapy. All participants will receive single-agent MIRV at 6 mg/kg adjusted ideal body weight administered on Day 1 of every 3-week cycle.

Detailed description:
This study is designed to evaluate the efficacy and safety of mirvetuximab soravtansine (MIRV) in participants with platinum-resistant high-grade serous epithelial ovarian cancer, primary peritoneal, or fallopian tube cancer, whose tumors express a high-level of Folate Receptor Alpha (FRα). Participants will be, in the opinion of the Investigator, appropriate for single-agent therapy for their next line of therapy. FRα positivity will be defined by the Ventana FOLR1 (Folate Receptor 1/Folate Receptor Alpha) Assay.

Approximately 110 eligible participants will be enrolled to achieve a total of 105 efficacy evaluable participants. Efficacy evaluable participants include those who have measurable lesions per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) at baseline and received at least 1 dose of MIRV.

All participants will receive single-agent MIRV at 6 mg/kg adjusted ideal body weight (AIBW) administered on Day 1 of every 3-week cycle (Q3W).

Tumor response will be evaluated by the Investigator using RECIST v1.1. Computerized tomography (CT) or magnetic resonance imaging (MRI) scans will be collected for sensitivity analysis by blinded independent central review (BICR).

Participants will continue to receive MIRV until disease progression, unacceptable toxicity, withdrawal of consent, death, or until the Sponsor terminates the study (whichever comes first).

Tumor assessments, including radiological assessments by CT/MRI scans will be performed at Screening and subsequently every 6 weeks (± 1 week) from Cycle 1 Day 1 (C1D1) for the first 36 weeks then every 12 weeks (± 3 weeks) until disease progression, death, the start of new anticancer therapy, or participant's withdrawal of consent (whichever occurs first).

Participants who discontinue MIRV for reasons other than progressive disease (PD) will continue with tumor assessments until documentation of PD or the start of a new anticancer therapy, whichever comes first. Prior to Week 36 (from Cycle 1, Day 1), assessments should occur every 6 weeks (± 1 week) as allowed by local requirements but must occur at an interval of no more than 12 weeks. After Week 36, assessment will occur every 12 weeks (± 3 weeks) until documentation of PD or the start of new anticancer therapy.

All participants who discontinue MIRV will be followed for survival every 3 months (± 1 month) until death, lost to follow-up, withdrawal of consent for survival follow-up, or end of study (EOS) (whichever comes first). Additional survival follow-up calls may occur periodically, if needed.

Arms:
arm 1: All participants will receive single-agent mirvetuximab soravtansine (MIRV) at 6 mg/kg adjusted ideal body weight (AIBW) administered on Day 1 of every 3-week cycle (Q3W).

Interventions: intervention 1: Mirvetuximab Soravtansine
Intervention descriptions: intervention 1: Mirvetuximab Soravtansine is an antibody drug conjugate designed to target folate receptor α (FRα). It consists of the humanized anti-FRα mAb M9346A attached via a cleavable disulfide linker to the cytotoxic maytansinoid, DM4.

Protocol document:
Prot_000.pdf: 




Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
3 
SPONSOR CONTACT LIST 
 
Primary Medical Monitor 
  
Phone: 
  
Email: 
 
Clinical Scientist 
 
Phone: 
 
Email: 
 
Trial Management  
 
Phone: 
 
Email: 
 
 
 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
4 
INVESTIGATOR’S AGREEMENT 
 
I have received and read the Investigator Brochure for mirvetuximab soravtansine.  
I have read the ImmunoGen Protocol IMGN853-0417 and agree to conduct the study as outlined 
and in conformance with International Conference on Harmonisation (ICH) E6 Good Clinical 
Practice (GCP) and applicable regulatory requirements. I agree to maintain the confidentiality of 
all information received or developed in connection with this protocol. 
 
 
Printed Name of Investigator 
 
Signature of Investigator 
Date 
 
 
 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
5 
LIST OF ABBREVIATIONS 
Table 1: 
List of Abbreviations and Definitions of Terms 
Abbreviation 
Term 
ADA 
anti-drug antibodies 
ADC 
antibody drug conjugate 
ADCC 
antibody-dependent cell-mediated cytotoxicity 
ADL 
activities of daily living 
AE 
adverse event 
AIBW 
adjusted ideal body weight 
ALT 
alanine aminotransferase (SGPT) 
ANC 
absolute neutrophil count 
aPTT 
activated partial thromboplastin time 
ASCO 
American Society of Clinical Oncology 
AST 
aspartate aminotransferase (SGOT) 
BICR 
blinded independent central review 
BIRC 
blinded independent review committee 
BRCA 
breast cancer susceptibility gene 
BUN 
blood urea nitrogen 
C1D1 
Cycle 1 Day 1 
CI 
confidence interval 
CNS 
central nervous system 
CR 
complete response/remission 
CRO 
contract research organization 
CT 
computed tomography 
CTCAE  
Common Terminology Criteria for Adverse Events 
DM4 
N2’-[4-[(3-carboxypropyl)dithio]-4-methyl-1-oxo-2-sulfopentyl]-N2’-
deacetylmaytansine 
S-methyl DM4 
methylated N2’-[4-[(3-carboxypropyl)dithio]-4-methyl-1-oxo-2-
sulfopentyl]-N2’-deacetylmaytansine 
DNA 
deoxyribonucleic acid 
DOR 
duration of response 
ECG 
electrocardiogram 
ECOG 
Eastern Cooperative Oncology Group 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
6 
Abbreviation 
Term 
eCRF 
electronic case report form 
EOC 
epithelial ovarian cancer 
EORTC 
European Organisation for Research and Treatment of Cancer 
EOS 
End of Study 
EOT 
End of Treatment 
EPO 
erythropoietin 
ERB 
Ethics Review Board 
FDA 
Food and Drug Administration 
FFPE 
formalin fixed paraffin embedded 
FIH 
first-in-human 
FOLR1, FRα 
folate receptor 1/folate receptor alpha 
GI 
gastrointestinal 
GCIG 
Gynecologic Cancer Intergroup  
GCP 
Good Clinical Practice 
HIV 
human immunodeficiency virus 
IC50 
half maximal (50%) inhibitory concentration 
IC 
Investigators Choice 
ICF 
informed consent form 
ICH 
International Conference on Harmonisation  
IDMC 
Independent Data Monitoring Committee 
IEC 
Independent Ethics Committee 
IHC 
immunohistochemistry 
ILD 
interstitial lung disease 
IMGN 
ImmunoGen 
INR 
international normalized ratio 
IRB 
Institutional Review Board 
IRR 
infusion-related reaction 
ITT 
intent-to-treat 
IV 
intravenous 
mAb 
monoclonal antibody 
MedDRA 
Medical Dictionary for Regulatory Activities 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
7 
Abbreviation 
Term 
MIRV 
mirvetuximab soravtansine (IMGN853) 
MRI 
magnetic resonance imaging 
MS 
multiple sclerosis 
MTD 
maximum tolerated dose 
NCCN 
National Comprehensive Cancer Network 
NCI 
National Cancer Institute 
nM 
nanomolar 
ORR 
objective response rate 
OS 
overall survival 
PD 
progressive disease 
PE 
physical examination 
PET 
positron emission testing 
PFS 
progression-free survival 
PFS2 
time to second disease progression 
PK 
pharmacokinetics 
PLT 
platelets 
PR 
partial response/remission 
PRN 
as needed  
PRO 
patient-reported outcome 
PROC 
platinum-resistant ovarian cancer 
PS 
performance status 
PT 
prothrombin time 
Q3W 
every 3 weeks 
REC 
Research Ethics Committee 
RECIST 
Response Evaluation Criteria in Solid Tumors 
RNA 
ribonucleic acid 
RP2D 
recommended phase 2 dose 
RT 
radiotherapy 
SAE 
serious adverse event 
SAP 
statistical analysis plan 
SC 
Steering Committee 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
8 
Abbreviation 
Term 
SD 
stable disease 
SGOT 
serum glutamic oxaloacetic transaminase (AST) 
SGPT 
serum glutamic pyruvic transaminase (ALT) 
SoD 
sum of diameters 
SOC 
System Organ Class 
SOP 
standard operating procedure 
SUSAR 
suspected unexpected serious adverse reaction 
TMT 
thiol s-methyltransferase 
TEAE 
treatment-emergent adverse event 
TPR 
time point response 
ULN 
upper limit of normal 
US 
United States 
Ventana FOLRI Assay 
Ventana FOLR1 (FOLR1-2.1) CDx assay 
WBC 
white blood cell (count) 
WCBP 
woman of childbearing potential 
WHO-DD 
World Health Organization-Drug Dictionary 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
9 
PROTOCOL SYNOPSIS 
Name of Sponsor/Company: ImmunoGen, Inc. 
Name of Investigational Product: mirvetuximab soravtansine (MIRV; IMGN853) 
Name of Active Ingredient: mirvetuximab soravtansine (MIRV; IMGN853) 
Title of Study: SORAYA: A Phase 3, Single Arm Study of Mirvetuximab Soravtansine in Platinum-
Resistant, Advanced High-Grade Epithelial Ovarian, Primary Peritoneal, or Fallopian Tube Cancers 
with High Folate Receptor-Alpha Expression 
Number of Patients (planned): Approximately 110 patients  
Study Center(s): Approximately 98 centers globally 
Studied Period (months): Approximately 30 months, 
including follow-up. 
Phase of Development: 3 
Objectives: 
Primary Objective 
• 
To determine the efficacy of MIRV in patients with platinum-resistant ovarian cancer (PROC) 
and high folate receptor alpha (FRα) expression  
Key Secondary Objective 
• 
To determine the durability of response to MIRV in patients with PROC and high FRα 
expression 
Additional Secondary Objectives 
• 
To evaluate the safety and tolerability of MIRV 
• 
To characterize the clinical activity of MIRV in patients with PROC and high FRα expression 
Exploratory Objectives 
 
 
 
  
 
 
 
 
Endpoints: 
Primary Endpoint 
• 
Objective response rate (ORR), which includes best response of complete response (CR) or 
partial response (PR) as assessed by the Investigator 
Key Secondary Endpoint 
• 
Duration of response (DOR), defined as the time from initial Investigator-assessed response 
(CR or PR) until progressive disease (PD) as assessed by the Investigator  
Additional Secondary Endpoints 
• 
Treatment-emergent adverse events (TEAEs) and laboratory test results, physical examination 
or vital signs 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
10 
• 
CA-125 response determined using the GCIG criteria defined in Appendix C 
• 
Progression-free survival (PFS), defined as the time from first dose of MIRV until 
Investigator-assessed radiological PD or death, whichever occurs first  
• 
Overall survival (OS), defined as the time from first dose of MIRV until death  
Study Design Overview: 
This Phase 3 study is designed to evaluate the efficacy and safety of MIRV in patients with platinum-
resistant high-grade serous epithelial ovarian cancer, primary peritoneal, or fallopian tube cancer, 
whose tumors express a high-level of FRα, referred to throughout as PROC (platinum-resistant ovarian 
cancer). Patients will be, in the opinion of the Investigator, appropriate for single-agent therapy for 
their next line of therapy. FRα positivity will be defined by the Ventana FOLRI Assay. 
Approximately 110 eligible patients will be enrolled to achieve a total of 105 efficacy evaluable 
patients. Efficacy evaluable patients include those who have measurable lesions (per RECIST v1.1) at 
baseline and received at least 1 dose of MIRV.   
All patients will receive single-agent MIRV at 6 mg/kg adjusted ideal body weight (AIBW) 
administered on Day 1 of every 3-week cycle (Q3W). 
Tumor response will be evaluated by the Investigator using Response Evaluation Criteria in Solid 
Tumors, version 1.1 (RECIST v1.1). Computerized tomography (CT) or magnetic resonance imaging 
(MRI) scans will be collected for sensitivity analysis by blinded independent central review (BICR). 
Patients will continue to receive MIRV until disease progression, unacceptable toxicity, withdrawal of 
consent, death, or until the Sponsor terminates the study (whichever comes first).  
Tumor assessments, including radiological assessments by CT/MRI scans will be performed at 
Screening and subsequently every 6 weeks (± 1 week) from Cycle 1 Day 1 (C1D1) for the first 
36 weeks then every 12 weeks (± 3 weeks) until disease progression, death, the start of new anticancer 
therapy, or patient’s withdrawal of consent (whichever occurs first).  
Patients who discontinue MIRV for reasons other than progressive disease (PD) will continue with 
tumor assessments until documentation of PD or the start of a new anticancer therapy, whichever 
comes first. Prior to Week 36 (from Cycle 1, Day 1), assessments should occur every 6 weeks 
(± 1 week) as allowed by local requirements but must occur at an interval of no more than 12 weeks. 
After Week 36, assessment will occur every 12 weeks (± 3 weeks) until documentation of PD or the 
start of new anticancer therapy.  
All patients who discontinue MIRV will be followed for survival every 3 months (± 1 month) until 
death, lost to follow-up, withdrawal of consent for survival follow-up, or end of study (EOS) 
(whichever comes first). Additional survival follow-up calls may occur periodically, if needed.  
Study Eligibility  
Inclusion Criteria 
1. Female patients ≥ 18 years of age 
2. Patients must have a confirmed diagnosis of high-grade serous EOC, primary peritoneal 
cancer, or fallopian tube cancer  
3. Patients must have platinum-resistant disease:   
a. Patients who have only had 1 line of platinum based therapy must have received at least 
4 cycles of platinum, must have had a response (CR or PR) and then progressed between 
> 3 months and ≤ 6 months after the date of the last dose of platinum 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
11 
b. Patients who have received 2 or 3 lines of platinum therapy must have progressed on or 
within 6 months after the date of the last dose of platinum 
Note: Progression should be calculated from the date of the last administered dose of 
platinum therapy to the date of the radiographic imaging showing progression  
Note: Patients who are platinum-refractory during front-line treatment are excluded (see 
exclusion criteria) 
4. Patients must have progressed radiographically on or after their most recent line of anticancer 
therapy 
5. Patients must be willing to provide an archival tumor tissue block or slides, or undergo 
procedure to obtain a new biopsy using a low-risk, medically routine procedure for 
immunohistochemistry (IHC) confirmation of FRα positivity  
6. Patient’s tumor must be positive for FRα expression as defined by the Ventana FOLRI Assay 
7. Patients must have at least 1 lesion that meets the definition of measurable disease by 
RECIST v1.1 (radiologically measured by the Investigator) 
8. Patients must have received at least 1 but no more than 3 prior systemic lines of anticancer 
therapy, including at least 1 line of therapy containing bevacizumab, and for whom single-
agent therapy is appropriate as the next line of treatment: 
a. Adjuvant ± neoadjuvant considered 1 line of therapy 
b. Maintenance therapy (eg, bevacizumab, PARP inhibitors) will be considered part of the 
preceding line of therapy (ie, not counted independently) 
c. Therapy changed due to toxicity in the absence of progression will be considered part of 
the same line (ie, not counted independently) 
d. Hormonal therapy will be counted as a separate line of therapy unless it was given as 
maintenance 
9. Patients must have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) 
of 0 or 1 
10. Patients must have completed prior therapy within the specified times below: 
a. Systemic antineoplastic therapy within 5 half-lives or 4 weeks (whichever is shorter) prior 
to first dose of MIRV 
b. Focal radiation completed at least 2 weeks prior to first dose of MIRV 
11. Patients must have stabilized or recovered (Grade 1 or baseline) from all prior therapy-related 
toxicities (except alopecia) 
12. Patients must have completed any major surgery at least 4 weeks prior to first dose of MIRV 
and have recovered or stabilized from the side effects of prior surgery 
13. Patients must have adequate hematologic, liver and kidney functions defined as: 
a. Absolute neutrophil count (ANC) ≥ 1.5 x 109/L (1,500/μL) without G-CSF in the prior 10 
days or long-acting WBC growth factors in the prior 20 days 
b. Platelet count ≥ 100 x 109/L (100,000/μL) without platelet transfusion in the prior 10 days 
c. Hemoglobin ≥ 9.0 g/dL without packed red blood cell (PRBC) transfusion in the prior 21 
days 
d. Serum creatinine ≤ 1.5 x upper limit of normal (ULN) 
e. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3.0 x ULN  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
12 
f. Serum bilirubin ≤ 1.5 x ULN (patients with documented diagnosis of Gilbert syndrome are 
eligible if total bilirubin < 3.0 x ULN) 
g. Serum albumin ≥ 2 g/dL 
14. Patients or their legally authorized representative must be willing and able to sign the informed 
consent form (ICF) and to adhere to the protocol requirements 
15. Women of childbearing potential (WCBP) must agree to use highly effective contraceptive 
method(s) (as defined in Section 5.8.6) while on MIRV and for at least 3 months after the last 
dose 
16. WCBP must have a negative pregnancy test within the 4 days prior to the first dose of MIRV 
Exclusion Criteria  
1. Male patients 
2. Patients with endometrioid, clear cell, mucinous, or sarcomatous histology, mixed tumors 
containing any of the above histologies, or low-grade/borderline ovarian tumor 
3. Patients with primary platinum-refractory disease, defined as disease that did not respond to 
(CR or PR) or has progressed within 3 months of the last dose of first-line platinum-containing 
chemotherapy 
4. Patients with prior wide-field radiotherapy (RT) affecting at least 20% of the bone marrow 
5. Patients with > Grade 1 peripheral neuropathy per Common Terminology Criteria for Adverse 
Events (CTCAE) 
6. Patients with active or chronic corneal disorders, history of corneal transplantation, or active 
ocular conditions requiring ongoing treatment/monitoring, such as uncontrolled glaucoma, wet 
age-related macular degeneration requiring intravitreal injections, active diabetic retinopathy 
with macular edema, macular degeneration, presence of papilledema, and /or monocular vision 
7. Patients with serious concurrent illness or clinically relevant active infection, including, but 
not limited to the following: 
a. Active hepatitis B or C infection (whether or not on active antiviral therapy)  
b. Human immunodeficiency virus (HIV) infection 
c. Active cytomegalovirus infection  
d. Any other concurrent infectious disease requiring IV antibiotics within 2 weeks prior to the 
first dose of MIRV 
Note: Testing at screening is not required for the above infections unless clinically indicated 
8. Patients with a history of multiple sclerosis (MS) or other demyelinating disease and/or 
Lambert-Eaton syndrome (paraneoplastic syndrome) 
9. Patients with clinically significant cardiac disease including, but not limited to, any of the 
following: 
a. Myocardial infarction ≤ 6 months prior to first dose 
b. Unstable angina pectoris 
c. Uncontrolled congestive heart failure (New York Heart Association > class II) 
d. Uncontrolled ≥ Grade 3 hypertension (per CTCAE) 
e. Uncontrolled cardiac arrhythmias 
10. Patients with a history of hemorrhagic or ischemic stroke within 6 months prior to enrollment 
11. Patients with a history of cirrhotic liver disease (Child-Pugh Class B or C) 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
13 
12. Patients with a previous clinical diagnosis of noninfectious interstitial lung disease (ILD), 
including noninfectious pneumonitis 
13. Patients requiring use of folate-containing supplements (eg, folate deficiency) 
14. Patients with prior hypersensitivity to monoclonal antibodies (mAb) 
15. Women who are pregnant or breastfeeding 
16. Patients who received prior treatment with MIRV or other FRα-targeting agents 
17. Patients with untreated or symptomatic central nervous system (CNS) metastases 
18. Patients with a history of other malignancy within 3 years prior to enrollment  
Note: patients with tumors with a negligible risk for metastasis or death (eg, adequately 
controlled basal-cell carcinoma or squamous-cell carcinoma of the skin, or carcinoma in situ of 
the cervix or breast) are eligible 
19. Prior known hypersensitivity reactions to study drugs and/or any of their excipients 
Prohibited Concomitant Medications:  
Any non-study anticancer agents, including but not limited to antineoplastic agents, biologics, mAbs, 
and hormonal therapy, or palliative RT during study treatment. 
Investigational Product, Dosage and Mode of Administration:  
Patients will receive MIRV 6 mg/kg AIBW Q3W.  
Duration of Study Participation:  
The duration of study participation for each patient extends from the signing of the ICF until the final 
follow-up study visit, termination from study, death, or withdrawal of consent.  
Study Committees: 
An Independent Data Monitoring Committee (IDMC) will not be utilized in this open-label, single-arm 
study of MIRV. 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
14 
Table 2: 
Schedule of Assessments 
Procedure 
Pre-
screening 
Screening 
Cycle 1 
C=3 weeks 
C2+ 
C3 
EOT 
30-Day  
Follow-up 
Survival  
Follow-up 
D1 
D8 
D1 
D8 
≤ 7d from 
discon. 
30 (+14) days 
from last dose 
Every 3 months 
(±1 month) 
from EOT 
Pre-screening Informed 
Consent 
● 
 
 
 
 
 
 
 
 
Informed Consent 
 
●a 
 
 
 
 
 
 
 
Eligibility 
 
●a 
 
 
 
 
 
 
 
Demographics 
 
●a 
 
 
 
 
 
 
 
Medical History 
 
●a 
 
 
 
 
 
 
 
Confirm Disease 
Diagnosis/Current Stage  
 
●a 
 
 
 
 
 
 
 
12-Lead ECG 
 
●b 
●b 
 
 
 
 
 
 
Coagulation  
(PT or INR/aPTT)  
 
●c 
 
 
 
 
 
 
 
Urinalysis  
 
●c 
 
 
 
 
 
 
 
FFPE archived tumor tissue 
and/or new biopsyd 
● 
 
 
 
 
 
 
 
 
Physical Examinatione 
 
●c 
●f 
 
● 
 
● 
● 
 
Weight 
 
●c 
● 
 
● 
 
● 
● 
 
Vital signsg 
 
●c 
● 
 
● 
 
● 
● 
 
ECOG PS  
 
●c 
●f 
 
● 
 
● 
● 
 
Hematology and Chemistryh 
 
●c 
●f 
 
● 
 
● 
● 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
15 
Procedure 
Pre-
screening 
Screening 
Cycle 1 
C=3 weeks 
C2+ 
C3 
EOT 
30-Day  
Follow-up 
Survival  
Follow-up 
D1 
D8 
D1 
D8 
≤ 7d from 
discon. 
30 (+14) days 
from last dose 
Every 3 months 
(±1 month) 
from EOT 
Blood sample for 
Biomarkers 
● 
● 
 
 
 
 
 
 
 
Pregnancy Testi 
 
●i 
●f 
 
● 
 
 
● 
 
Ophthalmic Examj 
 
●c 
Every other cycle from time 
treatment-emergent  
eye disorder first reported 
 
●j 
●j 
 
Ocular Symptom 
Assessmentk 
 
●c 
● 
 
● 
 
● 
● 
 
Radiologic Tumor 
Assessmentl 
 
●a 
Every 6 (±1) weeks from C1D1 
for first 36 weeks, then every 
12 (±3) weeks 
 
●m 
●m 
 
CA-125n 
 
●c 
Collect at each radiologic 
tumor assessment (± 4 days) 
 
●m 
●m 
 
MIRV administration  
 
 
● 
 
● 
 
 
 
 
Record AE/SAEs and 
concomitant medications 
●o 
● 
Collected continuously while patients are on study 
 
Blood sample for PKp 
 
 
● 
● 
●p 
● 
● 
●p 
 
Blood samples for 
immunogenicityq 
 
 
● 
 
● 
 
● 
●  
 
Survival Phone screen, 
including new anticancer 
therapyr 
 
 
 
 
 
 
 
 
● 
Abbreviations: AE = adverse event; aPTT = activated partial thromboplastin time; C = cycle; CA = cancer antigen; D = day; ECOG = Eastern Cooperative 
Oncology Group; ECG = electrocardiogram; EOT = End of Treatment; FFPE = formalin-fixed-paraffin-embedded; INR = international normalized ratio; PK = 
pharmacokinetics; PT = prothrombin time; SAE = serious adverse event. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
16 
Note: A patient’s BRCA mutational status (germline or somatic mutation in tumor tissue) will be collected as part of her medical history if available. Patients 
without a known mutation will be classified as unknown. 
a Must be within 28 days before C1D1 unless otherwise specified. 
b ECG assessment may be performed predose at C1D1 if not performed previously up to 28 days prior to first dose of MIRV. 
c Must be within 14 days before C1D1. 
d Testing for FRα expression is required for all patients. Those who do not have archival tumor tissue to submit will be required to undergo procedures to obtain 
a new biopsy using a low-risk, medically routine procedure during the Pre-screening period to confirm eligibility. If the archival tumor tissue does not meet 
FRα criteria, a new biopsy tumor sample may be submitted and used to confirm this criterion. 
e Complete physical examination (PE) is required at Screening and the 30-Day Follow-up visit. At all other study visits while on MIRV, patients will have 
symptom-directed PEs. 
f ECOG, PE, pregnancy test for WCBP, and hematology and chemistry labs (if all parameters are within normal range) do not need to be repeated at C1D1 if 
performed within the previous 4 days during Screening. 
g Vital signs (BP and body temperature) will be measured before start of infusion; post infusion vital signs should be collected as clinically indicated for 
potential infusion-related reaction. 
h Hematology and chemistry labs may be performed up to 4 days prior to D1 of each cycle, and as clinically indicated while on treatment, with results reviewed 
before each MIRV administration. In the event of severe toxicity, laboratory tests must be repeated as clinically necessary until the toxicity resolves or 
stabilizes to baseline level. 
i For women of childbearing potential (WCBP), a urine or serum pregnancy test must be performed within the 4 days prior to D1 of each cycle, and at the 30-
Day Follow-up visit. It is recommended to perform monthly pregnancy tests for 3 months after the last dose of MIRV. Additional testing may be performed in 
accordance with institutional requirements or local regulation. 
j Baseline ophthalmic exams will be performed by an ophthalmologist within 14 days before C1D1 and will include the following: visual acuity (with/without 
corrective lens; whichever best reflects the patient’s usual functioning), slit lamp examination, intraocular pressure measurement, and indirect fundoscopy. All 
patients who have an ophthalmic exam on study treatment (post-baseline) due to emergence of visual signs or symptoms will have a complete 
ophthalmological examination performed at EOT visit or 30-Day Follow-up visit. 
k Ocular symptoms assessment will be performed by the treating physician or other qualified individual before the start of each cycle. For patients reporting 
> CTCAE Grade 1 ocular symptoms, treatment will be held until the patient is evaluated by an ophthalmologist for a complete examination. 
l Radiologic tumor assessment by CT/MRI scan. The same method of radiographic assessment used at Screening must be used at all subsequent radiographic 
assessments. 
m If a patient discontinues before documentation of PD, a tumor assessment and CA-125 will be assessed at the EOT or 30-Day Follow-up visit, if not 
performed within the previous 6 weeks. Tumor assessments and CA-125 will continue to be performed every 12 (± 3) weeks until PD is documented per 
RECIST 1.1 or the patient starts new anticancer therapy. Patients who discontinue MIRV for reasons other than progressive disease (PD) will continue with 
tumor assessments until documentation of PD or the start of a new anticancer therapy, whichever comes first. Prior to Week 36 (from Cycle 1, Day 1), 
assessments should occur every 6 weeks (± 1 week) as allowed by local requirements but must occur at an interval of no more than 12 weeks. After Week 36, 
assessment will occur every 12 weeks (± 3 weeks) until documentation of PD, death, the start of new anticancer therapy, or patient’s withdrawal of consent 
(whichever occurs first). 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
17 
n CA-125 will be measured at the time of every tumor assessment (± 4 days) (responses will be confirmed according to GCIG criteria Appendix C). 
o Only AEs/SAEs which are considered related to a study procedure (ie blood draw or fresh tumor biopsy) will be captured during the Pre-screening period, ie 
from the time of signing the Pre-screening consent (if one is utilized) until the signing of the main study informed consent, or until the patient is determined to 
be a screen failure. 
p Blood samples for PK analysis will be taken within 1 hour after MIRV infusion on Day 1 of Cycles 1 and 3, and on Day 8 (±24 hours) of Cycles 1 and 3. 
Samples will also be collected prior to dosing on Day 1 of Cycles 2 and 4, and EOT and also at the 30-Day Follow-up, if feasible. 
q Immunogenicity will be assessed in PK samples collected prior to dosing (predose) on C1D1, C2D1, C4D1, at EOT, and 30-Day Follow-up. 
r Survival follow-up assessments will occur every 3 months (±1 month) until death, the patient is lost to follow-up or withdrawal of consent for survival follow-
up, or EOS (whichever comes first). These assessments may be conducted by telephone. Information on the start of new anticancer therapy (including start 
date, therapy type/name, and response on treatment) should be collected. Additional survival follow-up calls may occur periodically if needed for regulatory 
requests or at time of database lock for either primary or final analysis. 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
18 
TABLE OF CONTENTS 
SPONSOR SIGNATURE PAGE ....................................................................................................2 
SPONSOR CONTACT LIST ..........................................................................................................3 
INVESTIGATOR’S AGREEMENT ...............................................................................................4 
LIST OF ABBREVIATIONS ..........................................................................................................5 
PROTOCOL SYNOPSIS ................................................................................................................9 
1. 
INTRODUCTION ......................................................................................................25 
1.1. 
Target Background .....................................................................................................25 
1.2. 
Mirvetuximab Soravtansine ........................................................................................25 
1.3. 
Epithelial Ovarian Cancer ...........................................................................................26 
1.4. 
Current Therapies .......................................................................................................27 
1.5. 
Non-Clinical Studies of Mirvetuximab Soravtansine .................................................28 
1.5.1. 
Impact of FRα Expression ..........................................................................................28 
1.5.2. 
Pharmacology .............................................................................................................28 
1.5.3. 
Pharmacokinetics ........................................................................................................28 
1.5.4. 
Toxicology ..................................................................................................................29 
1.6. 
Clinical Studies of Mirvetuximab Soravtansine .........................................................29 
1.6.1. 
First-in-Human Phase 1 Clinical Trial: Study IMGN853-0401 .................................29 
1.6.2. 
Phase 3 Monotherapy Trial in Patients with Platinum-Resistant EOC, 
Peritoneal, and Fallopian Tube Cancer: Study IMGN853-0403 ................................29 
1.6.3. 
Conclusion ..................................................................................................................31 
1.7. 
Rationale for the Selection of Drug Dose Levels and Dosing Schedules ...................31 
1.7.1. 
Mirvetuximab Soravtansine ........................................................................................31 
1.8. 
Rationale for the Study Plan .......................................................................................32 
2. 
STUDY OBJECTIVES AND ENDPOINTS ..............................................................32 
2.1. 
Objectives ...................................................................................................................32 
2.1.1. 
Primary Objective .......................................................................................................32 
2.1.2. 
Key Secondary Objective ...........................................................................................32 
2.1.3. 
Additional Secondary Objectives ...............................................................................32 
2.1.4. 
Exploratory Objectives ...............................................................................................32 
2.2. 
Endpoints ....................................................................................................................33 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
19 
2.2.1. 
Primary Endpoint ........................................................................................................33 
2.2.2. 
Key Secondary Endpoint ............................................................................................33 
2.2.3. 
Additional Secondary Endpoints ................................................................................33 
2.2.4. 
Exploratory Endpoints ................................................................................................33 
3. 
STUDY POPULATION .............................................................................................33 
3.1. 
Criteria for Selection of Patient Population ................................................................33 
3.1.1. 
Inclusion Criteria ........................................................................................................33 
3.1.2. 
Exclusion Criteria .......................................................................................................35 
4. 
INVESTIGATIONAL PLAN .....................................................................................36 
4.1. 
Study Design ...............................................................................................................36 
4.1.1. 
Overview and Schema ................................................................................................36 
4.1.2. 
Dose and Schedule for Mirvetuximab Soravtansine ..................................................37 
5. 
STUDY TREATMENT ..............................................................................................37 
5.1. 
Mirvetuximab Soravtansine ........................................................................................37 
5.1.1. 
Mirvetuximab Soravtansine Packaging ......................................................................38 
5.1.2. 
Mirvetuximab Soravtansine Accountability ...............................................................38 
5.1.3. 
Mirvetuximab Soravtansine Study Treatment Compliance ........................................38 
5.2. 
Assignment of Patient Number ...................................................................................38 
5.2.1. 
Enrolled Patient Definition .........................................................................................39 
5.2.2. 
Patient Assignment to Dosing Regimens ...................................................................39 
5.3. 
Blinding Methods .......................................................................................................39 
5.4. 
Study Treatment Administration ................................................................................39 
5.4.1. 
Premedication for Study Treatment ............................................................................39 
5.4.2. 
Prophylactic use of Eye Drops ...................................................................................39 
5.4.2.1. 
Corticosteroid Eye Drops ...........................................................................................39 
5.4.2.2. 
Lubricating Artificial Tears ........................................................................................39 
5.4.3. 
Preparation and Administration of Mirvetuximab Soravtansine ................................40 
5.4.3.1. 
Calculation for Adjusted Ideal Body Weight .............................................................40 
5.5. 
Dose Modification Guidelines ....................................................................................41 
5.5.1. 
Treatment Criteria .......................................................................................................41 
5.5.1.1. 
Mirvetuximab Soravtansine-Related Adverse Events ................................................42 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
20 
5.5.1.2. 
Mirvetuximab Soravtansine Dose Reduction Dose Levels ........................................43 
5.5.1.3. 
Monitoring and Management of Nausea and Vomiting .............................................43 
5.5.1.4. 
Monitoring and Management of Diarrhea ..................................................................44 
5.5.2. 
Ocular Disorders .........................................................................................................44 
5.5.2.1. 
Monitoring and Preventive Measures .........................................................................44 
5.5.2.2. 
Management and Dose Modification Guidelines .......................................................44 
5.5.3. 
Monitoring of Noninfectious Pneumonitis .................................................................46 
5.5.4. 
Management of Electrolytes Imbalance .....................................................................48 
5.5.5. 
Potential Infusion-related Reactions ...........................................................................48 
5.5.6. 
Discontinuation of Mirvetuximab Soravtansine Due to Toxicity...............................50 
5.6. 
Discontinuation of the Patients from the Study or Study Treatment ..........................50 
5.6.1. 
End of Treatment ........................................................................................................50 
5.6.2. 
End of Study ...............................................................................................................50 
5.6.3. 
Withdrawal of Consent ...............................................................................................50 
5.6.4. 
Lost to Follow-up .......................................................................................................51 
5.7. 
Period of Observation .................................................................................................51 
5.8. 
Concomitant Medications and Procedures .................................................................52 
5.8.1. 
Antiemetic and Antidiarrheal Medications .................................................................52 
5.8.2. 
Folate-Containing Supplements ..................................................................................52 
5.8.3. 
Antineoplastic Therapy ...............................................................................................52 
5.8.4. 
Hematopoietic Growth Factors ...................................................................................52 
5.8.5. 
Anticoagulants ............................................................................................................52 
5.8.6. 
Methods of Contraception ..........................................................................................52 
5.8.7. 
Other Concomitant Medications .................................................................................53 
5.8.8. 
Medications that are CYP3A or MDR1 Substrates or CYP3A Substrates 
with Narrow Therapeutic Index ..................................................................................53 
5.9. 
Overdose and Medication Error ..................................................................................54 
5.9.1. 
Overdose .....................................................................................................................54 
5.9.2. 
Medication Error .........................................................................................................54 
6. 
PHARMACOKINETIC, IMMUNOGENICITY, AND BIOMARKER 
ASSESSMENTS.........................................................................................................54 
6.1. 
Pharmacokinetic Assessments – Mirvetuximab Soravtansine ...................................54 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
21 
6.2. 
Immunogenicity Assessments – Mirvetuximab Soravtansine ....................................55 
6.3. 
Evaluation of FRα Expression in Tumor Tissue ........................................................55 
6.4. 
Potential Predictive Markers of Drug Response .........................................................56 
6.4.1. 
Blood Biomarkers .......................................................................................................56 
6.4.2. 
Tumor Biomarkers ......................................................................................................56 
7. 
STUDY PROCEDURES ............................................................................................56 
7.1. 
Informed Consent .......................................................................................................56 
7.2. 
Inclusion and Exclusion Criteria ................................................................................57 
7.3. 
Confirmation of Disease Diagnosis ............................................................................57 
7.4. 
BRCA Mutation Status ................................................................................................57 
7.5. 
Demographic/Medical History ...................................................................................57 
7.6. 
Physical Examination, Weight, and Height ................................................................57 
7.7. 
Vital Signs ..................................................................................................................58 
7.8. 
Electrocardiogram (ECG) ...........................................................................................58 
7.9. 
Ocular Symptom Assessment and Ophthalmic Examination .....................................58 
7.9.1. 
Ocular Symptom Assessment .....................................................................................58 
7.9.2. 
Ophthalmic Examination ............................................................................................58 
7.10. 
Laboratory Assessments .............................................................................................58 
7.10.1. 
Clinical Laboratory Panels .........................................................................................59 
7.11. 
Pregnancy Screen ........................................................................................................59 
7.12. 
Eastern Cooperative Oncology Group Performance Status ........................................59 
7.13. 
Tumor Response Assessment .....................................................................................60 
7.13.1. 
Radiological Imaging ..................................................................................................60 
7.13.2. 
CA-125 .......................................................................................................................60 
8. 
ASSESSMENT OF SAFETY .....................................................................................60 
8.1. 
Recording Adverse Events and Serious Adverse Events ...........................................60 
8.1.1. 
Definition of Adverse Events .....................................................................................61 
8.1.1.1. 
Adverse Event .............................................................................................................61 
8.1.1.2. 
Serious Adverse Event ................................................................................................62 
8.1.1.3. 
Adverse Events of Special Interest .............................................................................62 
8.1.2. 
Classification of Adverse Events ................................................................................63 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
Confidential and Proprietary 
ImmunoGen, Inc. 
22 
8.2. 
Adverse Events ...........................................................................................................64 
8.2.1. 
Reporting Serious Adverse Events .............................................................................64 
8.2.1.1. 
Reporting of Disease Progression ...............................................................................65 
8.2.2. 
Reporting a Pregnancy ................................................................................................65 
9.
STUDY ACTIVITIES ................................................................................................66 
9.1. 
Screening Visit ............................................................................................................66 
9.1.1. 
Standard of Care Assessments ....................................................................................66 
9.2. 
End of Treatment Visit ...............................................................................................66 
9.3. 
Follow-up Assessments ..............................................................................................67 
9.3.1. 
30-Day Follow-up Visit ..............................................................................................67 
9.3.2. 
Response Follow-up ...................................................................................................67 
9.3.3. 
Survival Follow-up .....................................................................................................67 
10.
STATISTICAL METHODS .......................................................................................67 
10.1. 
Sample Size ................................................................................................................68 
10.2. 
Pharmacokinetic Analyses ..........................................................................................68 
10.3. 
Safety Analyses ..........................................................................................................68 
10.4. 
Efficacy .......................................................................................................................69 
10.4.1. 
Primary Efficacy Analysis ..........................................................................................69 
10.4.1.1. 
Objective Response Rate ............................................................................................69 
10.4.2. 
Key Secondary Efficacy Endpoint ..............................................................................69 
10.4.3. 
Additional Secondary Efficacy Endpoints ..................................................................69 
10.5. 
Interim Analysis ..........................................................................................................69 
11.
QUALITY CONTROL AND ASSURANCE ............................................................70 
11.1. 
Recording of Data and Data Quality Assurance .........................................................70 
12.
ETHICAL CONSIDERATIONS AND ADMINISTRATIVE
PROCEDURES ..........................................................................................................70 
12.1. 
Ethical and Regulatory ...............................................................................................70 
12.1.1. 
Institutional Review Board or Independent Ethics Committee Approval ..................70 
12.1.2. 
Patient Information and Consent ................................................................................71 
12.2. 
Investigators and Study Administrative Structure ......................................................71 
12.3. 
Patient Confidentiality ................................................................................................72 
12.4. 
Study Monitoring ........................................................................................................72 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
23 
12.5. 
Study Committees .......................................................................................................73 
12.5.1. 
Steering Committee ....................................................................................................73 
12.5.2. 
Independent Data Monitoring Committee ..................................................................73 
12.6. 
Case Report Forms and Study Reports .......................................................................73 
12.7. 
Protocol Adherence ....................................................................................................74 
12.8. 
End of Study ...............................................................................................................74 
12.9. 
Study Termination ......................................................................................................74 
12.10. 
Site Termination .........................................................................................................75 
12.11. 
Access to Source Documentation ...............................................................................75 
12.12. 
Audits and Inspections ................................................................................................75 
12.13. 
Data Generation and Analysis ....................................................................................76 
12.14. 
Retention of Data ........................................................................................................76 
12.15. 
Financial Disclosure ...................................................................................................76 
12.16. 
Insurance Compensation .............................................................................................76 
12.17. 
Publication and Disclosure Policy ..............................................................................76 
13. 
LIST OF REFERENCES ............................................................................................77 
APPENDIX A. EASTERN COOPERATIVE ONCOLOGY GROUP (ECOG) 
PERFORMANCE STATUS SCALE .........................................................................81 
APPENDIX B. RESPONSE DEFINITIONS (RECIST 1.1) ......................................................82 
APPENDIX C. GYNECOLOGIC CANCER INTERGROUP (GCIG) CRITERIA FOR 
EVALUATION OF CA-125 ......................................................................................88 
APPENDIX D. LIST OF CONCOMITANT MEDICATIONS REQUIRING 
CAREFUL MONITORING .......................................................................................91 
APPENDIX E. ADJUSTED IDEAL BODY WEIGHT (AIBW) CALCULATION ..................92 
 
LIST OF TABLES 
Table 1: 
List of Abbreviations and Definitions of Terms ...........................................................5 
Table 2: 
Schedule of Assessments ............................................................................................14 
Table 3: 
Dose Modifications for Mirvetuximab Soravtansine-Related Adverse Events ..........42 
Table 4: 
Mirvetuximab Soravtansine Dose Reduction Dose Levels ........................................43 
Table 5: 
Management of Ocular Symptoms .............................................................................45 
Table 6: 
Management of Noninfectious Pneumonitis ..............................................................47 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
Confidential and Proprietary 
ImmunoGen, Inc. 
24 
Table 7: 
Management Guidelines for Potential Infusion-Related Reactions ............................49 
Table 8: 
Pharmacokinetics Sampling Time Points ...................................................................55 
Table 9: 
Clinical Laboratory Tests ...........................................................................................59 
Table 10: Adverse Event Severity ..............................................................................................63 
Table 11: Adverse Event Causal Relatedness .............................................................................64 
LIST OF FIGURES 
Figure 1: 
Mirvetuximab Soravtansine Structure ........................................................................26 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
25 
1. 
INTRODUCTION 
1.1. 
Target Background 
Folate receptor alpha (FRα) is a glycosylphosphatidylinositol-anchored cell surface protein 
encoded by the folate receptor 1 (FOLR1) gene. FRα internalizes folate, which is an essential 
cofactor for one-carbon transfer reactions that are required for DNA and RNA synthesis, cell 
growth and proliferation. Marked upregulation of FRα occurs during neonatal development and 
in cancer, suggesting that the receptor functions primarily under conditions of high folate 
demand. In contrast, normal adult tissues generally lack FRα expression and employ alternative 
transporters such as folate receptor β, reduced folate carrier and proton-coupled folate transporter 
for folate uptake (Weitman 1992, Mantovani 1994, Elnakat 2004, Kelemen 2006, and 
Investigator Brochure).  
Published studies have demonstrated FRα overexpression by immunohistochemistry (IHC) in 
various epithelial tumors, particularly the serous and endometrioid histologic subtypes of ovarian 
and endometrial cancers (Scorer 2010, Garin-Chesa 1993, Kalli 2008, Crane 2012, Dainty 2007, 
Jones 2008, Ab 2015, and Allard 2007). IHC results obtained from patients screened or enrolled 
in the Phase 1 Study IMGN853-0401 and Phase 3 Study IMGN853-403 are generally consistent 
with the literature (Investigator Brochure). Assessment of the FRα distribution in the PROC 
expansion cohort of IMGN853-0401 demonstrated that approximately 40% of patients have high 
expression.  
Several additional studies have further validated FRα as a target in serous epithelial ovarian 
cancer (EOC). First, quantitative polymerase chain reaction studies show ubiquitous FRα mRNA 
expression in serous EOC (Hanker 2012, Hoskins 1998, Hough 2001) and high levels of FRα 
mRNA correlate with poor response to chemotherapy and decreased disease-free survival 
(Chen 2012). Second, both Kalli et al and Crane et al have demonstrated that recurrent tumors 
retain FRα expression comparably to primary tumors as shown by serial biopsy sampling and 
IHC (Kalli 2008, Crane 2012). Third, studies with FRα-specific imaging agents have 
demonstrated real-time FRα expression at primary and metastatic tumor sites (Fisher 2008, 
Gaillard 2018, Garcia 2013, Garin-Chesa 1993, and van Dam 2011). Finally, a truncated form of 
FRα has been detected in ascites and blood of EOC patients (Basal 2009, Mantovani 1994), 
further confirming expression in this disease and suggesting that the receptor may serve as a 
circulating biomarker. Collectively, these data suggest that FRα is a promising target in solid 
tumors, particularly EOC. 
1.2. 
Mirvetuximab Soravtansine 
Because of its tumor-specific expression and capacity to internalize small and large molecule 
ligands, FRα has emerged as a promising target for antibody drug conjugate (ADC) therapy. 
ADCs combine the specificity of mAb to tumor antigens with the extraordinary cytotoxicity of 
maytansine derivatives, which are potent anti-microtubule agents that target proliferating cells. 
MIRV is an ADC designed to target FRα. It consists of the humanized anti-FRα mAb M9346A 
attached via a cleavable disulfide linker to the cytotoxic maytansinoid, DM4 (Figure 1). 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
Confidential and Proprietary 
ImmunoGen, Inc.
26 
Figure 1: 
Mirvetuximab Soravtansine Structure
DM4 is ~2% by weight relative to mAb. 
Due to the nature of the conjugation process, the number of DM4 molecules attached to the mAb 
ranges from 1 to 7 molecules per Ab, with an average of 3 or 4 DM4 molecules per Ab. 
Conjugation of the maytansinoid to the tumor-targeting Ab ensures that the cytotoxic component 
remains inactive in the circulation. Release of the cytotoxic payload requires binding, 
internalization, and degradation of the Ab. The released payload then kills the cell by inducing 
G2-M arrest and cell death. Cellular processing of maytansinoid conjugates can also generate 
lipophilic catabolites that cross cell membranes and kill neighboring cells (Erickson 2006). 
In vitro, MIRV binds cell surface FRα with high apparent affinity (≤ 0.1 nM) and shows potent 
(IC50 ≤ 1 nM) and selective cytotoxicity against tumor cells expressing FRα. Cytotoxic effects of 
MIRV in vitro is related to the level of cell-surface expression of FRα (Ab 2015). MIRV 
additionally demonstrates significant activity against FRα positive xenografts, with partial and 
complete remissions observed in ovarian models (Ab 2015). Together with the selective 
upregulation of FRα in solid tumors, these results provide the rationale for exploring the clinical 
utility of MIRV.
1.3.
Epithelial Ovarian Cancer
Ovarian cancer is a lethal disease with 22,530 new cases and 13,980 deaths expected in 2019 in 
the US (SEER Cancer Statistics Factsheet 2019). The estimated number of new EOC cases in the 
EU (EU27) in 2012 was 44,149 with 29,758 deaths (EUCAN Cancer Fact Sheet: Ovary 2019). 
The overall 5-year survival for EOC patients is only 44% (Cannistra 2004, Baldwin 2012).
Recent studies indicate that ovarian, peritoneal, and fallopian tube cancers are not distinct 
entities, but represent a spectrum of diagnoses that originate in the Mullerian tissue. Primary 
fallopian tube carcinoma and peritoneal cancers are now included in the ovarian cancer staging 
classification (Cobb 2015, Grant 2010, Naumann 2011, O’Shannessy 2013), and are considered 
to be part of EOC with the same treatment and outcomes.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
27 
Despite considerable improvements in primary therapy, 80% of the patients with advanced EOC 
are expected to relapse during or after treatment with platinum-containing regimens 
(Armstrong 2019). Disease recurring within 6 months of platinum-based chemotherapy is 
classified as platinum resistant, whereas, disease recurring longer than 6 months after therapy is 
termed platinum sensitive.  
While PARP inhibitors (eg, olaparib and rucaparib) were initially approved as single-agent 
treatment for EOC patients with BRCA mutations (~15% of EOC) who received ≥ 2 prior 
regimens (Moore 2019), their greatest benefit appears to be as maintenance therapy, both in the 
recurrent platinum-sensitive (Mirza 2016) and front-line settings (Gonzalez-Martin 2019, Moore 
2018), with the greatest treatment effect in patients with BRCA mutations or other mechanisms 
of homologous recombination deficiency. 
Like PARP inhibitors, bevacizumab is also approved for EOC in combination with 
chemotherapy and as continued monotherapy in the maintenance setting. While bevacizumab is 
approved in combination with chemotherapy in the platinum-resistant setting, many patients 
receive it earlier in their disease course based on the approvals in the front-line and recurrent 
platinum-sensitive settings. For those who do receive it in the platinum-resistant setting, 
bevacizumab combinations are limited to patients who have received no more than 2 prior 
chemotherapy regimens and are not at risk for bowel perforations (recto-sigmoid involvement, 
bowel involvement and/or history of bowel obstruction) (Aghajanian 2012, Pujade-Lauraine 
2014). 
Those patients with PROC who have received prior bevacizumab, either in the platinum-resistant 
or in the platinum-sensitive setting, have few options. They typically receive subsequent single-
agent chemotherapy. Unfortunately, response rates to single-agent chemotherapy are modest 
(~10 to 15%) and DOR is typically 4 to 8 months (Cannistra 2010, Matsuo 2010). Similarly, OS 
is poor (median ~11 to 14 months) (Naumann 2011, Pujade-Lauraine 2014). Because PROC 
remains a significant unmet medical need, the National Comprehensive Cancer Network 
(NCCN) guidelines recommend that platinum-resistant patients participate in clinical trials 
(NCCN Guidelines 2019). 
The ORR with single-agent chemotherapy in this setting is ~12% in the AURELIA study and 
more recently in the CORAIL study, with additional studies reporting an ORR of 5% to 15% in 
similar populations of PROC (Gaillard 2018, Cannistra 2010, Pujade-Lauraine 2014, Pujade-
Lauraine 2019).  
1.4. 
Current Therapies 
Patients with PROC who have either received bevacizumab or are ineligible for bevacizumab are 
generally treated with single-agent chemotherapy, leading to the poor outcomes described above 
(Section 1.3). The single-agent chemotherapies most commonly used include paclitaxel, 
pegylated liposomal doxorubicin, and topotecan.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
28 
1.5. 
Non-Clinical Studies of Mirvetuximab Soravtansine 
1.5.1. 
Impact of FRα Expression 
Studies assessing the potency and specificity of MIRV were conducted on a panel of FRα-
positive cell lines with a wide range of FRα expression, as well as on FRα-negative cell lines. 
These studies revealed a positive correlation between the level of FRα expression on the cell 
surface, the amount of maytansinoid catabolites generated, and the degree of sensitivity of the 
cells to MIRV in vitro. MIRV is not active against low and negative FRα expressing cells. 
1.5.2. 
Pharmacology 
Results of nonclinical pharmacology studies demonstrate the following: 
• FRα has limited normal tissue expression and marked expression in solid tumors, 
particularly cancers of the ovary and endometrium (Investigator Brochure). In vitro 
studies demonstrated that MIRV binds cell surface FRα with high apparent affinity 
(≤ 0.1 nM) and shows potent (IC50 ≤ 1 nM) and selective cytotoxicity against cells 
expressing FRα. MIRV-mediated cytotoxicity involves binding, internalization, and 
degradation of MIRV, which releases DM4. DM4 can be methylated to yield S-
methyl-DM4. Both DM4 and S-methyl-DM4 can inhibit tubulin polymerization and 
microtubule assembly, causing cell death. The lipophilic molecules S-methyl DM4 
and DM4 can also diffuse to neighboring cells and induce bystander killing.  
• In vitro cytotoxicity studies suggest that cells sensitive to MIRV express higher levels 
of FRα and release 10- to 100-fold more cytotoxic maytansinoid than cells resistant to 
MIRV.  
• MIRV retains the inherent activities of its Ab moiety, M9346A, including binding 
affinity (apparent affinity ≤ 0.1 nM) and selectivity for FRα, capacity for uptake, 
internalization and degradation by FRα-positive target cells, and ability to induce Ab-
dependent cell-mediated cytotoxicity (ADCC) in vitro.  
• MIRV demonstrates significant activity against FRα-positive xenografts. Partial 
and/or complete regressions in xenograft models of EOC were seen at doses of MIRV 
well below its maximum tolerated dose (MTD).  
1.5.3. 
Pharmacokinetics 
Nonclinical studies with MIRV cross-reactive (monkey) and non-cross-reactive (mouse) species 
were conducted to define pharmacokinetics (PK) parameters and to determine the stability of the 
linker and impact of conjugation on Ab clearance. An additional PK study with free DM4 was 
conducted in monkey. PK studies demonstrated the stability of MIRV in circulation after IV 
administration, with a distribution phase lasting about 24 hours followed by a slower terminal 
elimination phase. The data indicated that the PK of MIRV were approximately dose 
proportional within the ranges evaluated (1 to 10 mg/kg). These studies are further detailed in the 
Investigator Brochure.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
29 
1.5.4. 
Toxicology 
MIRV was evaluated for toxicity after a single IV injection in cross-reactive (monkey) and non-
cross-reactive (mouse) species. Results of these studies supported the first-in-human (FIH) study 
exploring the safety and tolerability of MIRV when administered once every 3 weeks to patients 
with advanced solid tumors. Potential risks suggested by these studies as well as clinical 
experience with other maytansinoid ADCs include hematologic abnormalities, electrolyte 
alterations, injection site reactions, infusion reactions, immunogenicity, hepatic abnormalities, 
and peripheral neuropathy. Toxicology studies are further detailed in the Investigator Brochure. 
1.6. 
Clinical Studies of Mirvetuximab Soravtansine 
1.6.1. 
First-in-Human Phase 1 Clinical Trial: Study IMGN853-0401 
The first-in-human (FIH), Phase 1 study evaluated the safety, PK and pharmacodynamics of 
single-agent MIRV in patients with EOC and other FRα-positive tumors. The recommended 
Phase 2 dose (RP2D) for single-agent MIRV administered Q3W was determined to be 6.0 mg/kg 
AIBW. Data from this study are detailed in the Investigator Brochure.  
The initial antitumor activity observed with MIRV monotherapy in Study IMGN853-0401, 
particularly in those patients with PROC, no more than 3 prior lines of therapy and FRα medium 
or high expression per the “PS2+” scoring method [defined by 2+ intensity staining of tumor 
cells with medium ≥50% to <75% of tumor cells and high ≥75% of tumor cells] suggested the 
potential for a significant improvement over single-agent chemotherapy. In the 36 patients with 
PROC who had received no more than 3 prior lines of therapy, and had FRα medium or high 
expression, MIRV was associated with a confirmed Investigator-assessed ORR of 47%, median 
DOR of 5.8 months, and median PFS of 6.7 months, comparing favorably with results seen with 
single-agent chemotherapy. Similarly, in the subset of 27 patients with FRα-high expression, the 
confirmed Investigator-assessed ORR was 44%, with median DOR of 7.8 months and median 
PFS of 6.7 months. 
Safety data suggested that MIRV was well tolerated, with a safety profile primarily consisting of 
low-grade gastrointestinal (GI) AEs and blurred vision related to corneal keratopathy. The 
treatment-emergent adverse events (TEAEs) were manageable with standard medical care and/or 
dose modification, with a low rate (10%) of patients discontinuing MIRV due to a treatment-
related TEAE.  
1.6.2. 
Phase 3 Monotherapy Trial in Patients with Platinum-Resistant EOC, 
Peritoneal, and Fallopian Tube Cancer: Study IMGN853-0403 
IMGN853-0403 was a Phase 3 study with the objective to evaluate the safety and efficacy of 
single-agent MIRV versus Investigators Choice (IC) chemotherapy in patients with PROC, 
primary peritoneal cancer, or fallopian tube cancer, and whose tumor was FRα-positive (medium 
or high expression) by the Ventana IHC assay using a "10x" scoring method (see Investigator 
Brochure). The study was designed to compare the efficacy of MIRV to that of approved single-
agent selected standard of care chemotherapy (paclitaxel, PLD, or topotecan) in patients with 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
30 
PROC who have received no more than 3 prior systemic treatment regimens and for whom 
single-agent chemotherapy is appropriate as the next line of therapy. 
A total of 366 patients were randomized and assigned to MIRV or IC chemotherapy groups (248 
and 118, respectively) and were included in the intent-to-treat (ITT) analysis. A total of 352 
patients received at least 1 dose of MIRV or IC chemotherapy (243 and 109, respectively). All 
patients in the MIRV group received a dose of 6 mg/kg AIBW Q3W, while the patients in the IC 
chemotherapy groups received single-agent chemotherapy.  
The primary endpoint was PFS by a blinded independent review committee (BIRC), which was 
assessed using the Hochberg procedure in the entire study population and in the FRα-high 
population. The Hochberg procedure enables the simultaneous testing of 2 overlapping 
populations. Under this statistical analysis plan, if the p-value of the primary endpoint in either 
population is greater than 0.05, the p-value in the other population needs to be less than or equal 
to 0.025 to achieve statistical significance. The primary endpoint, PFS, did not reach statistical 
significance in either the overall ITT population (p-value = 0.897; HR = 0.981) or in the pre-
specified FRα-high population (p-value = 0.049; HR = 0.693).  
This was the first study to evaluate available chemotherapy specifically in patients with high 
FRα expression. An examination of efficacy in the prespecified FRα-high population (by the 10x 
scoring method) showed clinically meaningful advantage for those patients randomized to MIRV 
versus IC chemotherapy across all endpoints. MIRV treatment in PROC patients with high FRα 
expression resulted in an ORR (by BIRC) of 24% (95% CI: 17.2, 31.5) compared with 10% 
(95% CI: 4.1, 19.3) for patients randomized to IC chemotherapy (p-value = 0.014), median PFS 
of 4.8 months (95% CI: 4.11, 5.68) versus 3.3 months (95% CI: 1.97, 5.59) for patients 
randomized to IC chemotherapy (p-value = 0.049; HR = 0.693), median OS in patients 
randomized to MIRV was not reached (95% CI: 12.58, not estimable) versus 11.8 months (95% 
CI: 9.20, not estimable) for patients randomized to IC chemotherapy (p-value = 0.033; HR = 
0.618). OS results are not confounded by an imbalance in subsequent anti-cancer therapy. The 
median DOR using response evaluation criteria in solid tumors (RECIST) v1.1 per BIRC in the 
FRα-high population in patients randomized to MIRV was 5.7 months (95% CI: 4.17, -) versus 
4.2 months (95% CI: 3.22, 8.71) for patients randomized to IC chemotherapy. Consistent with 
the observed tumor shrinkage, CA-125 responses per the Gynecologic Cancer InterGroup 
(GCIG) criteria occurred in 53% of FRα response-evaluable patients treated with MIRV versus 
25% in the IC chemotherapy group. Analysis of time to second disease progression (PFS2) 
suggests that the clinical benefit observed with MIRV does not diminish the efficacy of 
subsequent therapy (patient randomized to MIRV median 10.1 months [95% CI: 9.03, 11.20] 
versus 8.4 months [95% CI: 7.10, 9.46] for patients randomized to IC chemotherapy [p-value < 
0.001; HR = 0.557]). 
Exploratory post-hoc analyses using the "PS2+" scoring method (see Section 1.1) demonstrated 
an even stronger treatment effect for MIRV in the high FRα subset defined by this method 
(Moore 2019). 
The efficacy and safety of MIRV from this Phase 3 study were supported by patient-reported 
outcome (PRO) data, which showed a larger proportion of patients with a ≥ 15 point 
improvement in the European Organization for Research and Treatment of Cancer (EORTC)-


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
31 
QLQ-OV28 Abdominal/GI symptom subscale from baseline to Week 8/9 compared to IC 
chemotherapy (32% vs 13.7% respectively, p=0.011). 
The MIRV safety profile was predominantly characterized by low-grade nausea (51%), diarrhea 
(40%), and blurred vision (40%). These TEAEs are generally managed and mitigated with 
antiemetics, antidiarrheals, and lubricating/steroid eye drops. In the MIRV group, there were 
fewer ≥ Grade 3 TEAEs, and fewer TEAEs leading to dose reduction or delay and treatment 
discontinuation (46%, 37%, and 12%, respectively) compared with the IC chemotherapy group 
(61%, 45%, and 19%, respectively). While myelosuppression is an important safety issue with 
PLD and Topo, MIRV is associated with less myelosuppression compared to IC chemotherapy, 
with lower rates of neutropenia (7% vs. 39% all grade; 0% vs. 21% Grade 3+), 
thrombocytopenia (11% vs. 16% all grade; 0% vs. 4% Grade 3+) and anemia (14% vs. 29% all 
grade; 2% vs. 11% Grade 3+). Similarly, neurotoxicity is an important safety issue with Pac; 
MIRV, an ADC with the tubulin-directed payload DM4, is associated with less peripheral 
neuropathy than Pac (15% vs. 28% Grade 2+) and less alopecia (3% vs. 22% all grades). The 
safety profile of MIRV in the high FRα subset is consistent with that observed in the overall 
MIRV safety population. 
For MIRV the mean half-life (t½,) was 115.1 hour (4.8 days), with little evidence of accumulation 
(mean accumulation ratio of 1.102).  
There was no apparent relationship between patients testing positive for anti-drug antibodies 
(ADA) and MIRV exposure.  
Please see the Investigator Brochure for information on Study IMGN853-0403.  
1.6.3. 
Conclusion 
The available safety and efficacy data from the 455 patients treated with single-agent 
mirvetuximab soravtansine in previous clinical studies are consistent with a positive risk benefit 
assessment. The potential benefit of the anti-tumor activity demonstrated by mirvetuximab 
soravtansine in patients with FRα high platinum resistant ovarian cancer, a population with high 
unmet need, outweighs the risks associated with the well tolerated safety profile, as summarized 
above. 
1.7. 
Rationale for the Selection of Drug Dose Levels and Dosing 
Schedules 
1.7.1. 
Mirvetuximab Soravtansine 
The selection of the Phase 3 dose of 6 mg/kg AIBW IV Q3W was based on data obtained from 
Study IMGN853-0401, a FIH study designed to establish the MTD and determine the RP2D of 
MIRV when administered IV as a single-agent in adult patients with FRα-positive solid tumors 
who have relapsed or are refractory to standard therapies. The appropriateness of this dose and 
regimen in patients with PROC was further supported by the results of the Phase 3 study 
IMGN853-0403. For more information please see the Investigator Brochure.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
32 
1.8. 
Rationale for the Study Plan 
The design of this study is based on data obtained from both the Phase 1 study (IMGN853-0401) 
and the Phase 3 study (IMGN853-0403), which showed a potential for a clinically meaningful 
ORR and DOR for MIRV when considering what would be expected with available single-agent 
therapies in this PROC population (eg, 12% ORR in the Aurelia and CORAIL studies [Pujade-
Lauraine 2014, Gaillard 2018]). While the prior Phase 3 study did not reach statistical 
significance in the entire population (patients with medium and high FRα expression), those 
patients with high FRα expression showed promising results that, in conjunction with the Phase 1 
study results, provide the rationale for conducting this trial. 
This single arm Phase 3 study is designed to evaluate the efficacy and safety of MIRV 
administered at 6 mg/kg AIBW Q3W in patients with bevacizumab pretreated, platinum-resistant 
high-grade serous EOC, primary peritoneal, or fallopian tube cancer, whose tumors express a 
high level of FRα. Patients will be, in the opinion of the Investigator, appropriate for single-
agent- therapy for their next line of therapy. FRα positivity (high FRα) will be defined by the 
Ventana FOLRI Assay. Please see the Investigator Brochure for details regarding scoring 
methodology used for patient selection. 
2. 
STUDY OBJECTIVES AND ENDPOINTS 
2.1. 
Objectives 
2.1.1. 
Primary Objective 
• To determine the efficacy of MIRV in patients with PROC and high FRα expression  
2.1.2. 
Key Secondary Objective 
• To determine the durability of response to MIRV in patients with PROC and high 
FRα expression  
2.1.3. 
Additional Secondary Objectives 
• To evaluate the safety and tolerability of MIRV 
• To characterize the clinical activity of MIRV in patients with PROC and high FRα 
expression 
2.1.4. 
Exploratory Objectives 
 
 
 
 
 
  
 
 




Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
34 
3. Patients must have platinum-resistant disease:   
a. Patients who have only had 1 line of platinum based therapy must have received at 
least 4 cycles of platinum, must have had a response (CR or PR) and then progressed 
between > 3 months and ≤ 6 months after the date of the last dose of platinum 
b. Patients who have received 2 or 3 lines of platinum therapy must have progressed on 
or within 6 months after the date of the last dose of platinum 
Note: Progression should be calculated from the date of the last administered dose of 
platinum therapy to the date of the radiographic imaging showing progression  
Note: Patients who are platinum-refractory during front-line treatment are excluded (see 
exclusion criteria) 
4. Patients must have progressed radiographically on or after their most recent line of 
anticancer therapy 
5. Patients must be willing to provide an archival tumor tissue block or slides, or undergo 
procedure to obtain a new biopsy using a low-risk, medically routine procedure for 
immunohistochemistry (IHC) confirmation of FRα positivity  
6. Patient’s tumor must be positive for FRα expression as defined by the Ventana FOLRI 
Assay 
7. Patients must have at least 1 lesion that meets the definition of measurable disease by 
RECIST v1.1 (radiologically measured by the Investigator) 
8. Patients must have received at least 1 but no more than 3 prior systemic lines of 
anticancer therapy, including at least 1 line of therapy containing bevacizumab, and for 
whom single-agent therapy is appropriate as the next line of treatment: 
a. Adjuvant ± neoadjuvant considered 1 line of therapy 
b. Maintenance therapy (eg, bevacizumab, PARP inhibitors) will be considered part of 
the preceding line of therapy (ie, not counted independently) 
c. Therapy changed due to toxicity in the absence of progression will be considered part 
of the same line (ie, not counted independently) 
d. Hormonal therapy will be counted as a separate line of therapy unless it was given as 
maintenance 
9. Patients must have an Eastern Cooperative Oncology Group Performance Status (ECOG 
PS) of 0 or 1 
10. Patients must have completed prior therapy within the specified times below: 
a. Systemic antineoplastic therapy within 5 half-lives or 4 weeks (whichever is shorter) 
prior to first dose of MIRV 
b. Focal radiation completed at least 2 weeks prior to first dose of MIRV 
11. Patients must have stabilized or recovered (Grade 1 or baseline) from all prior therapy-
related toxicities (except alopecia) 
12. Patients must have completed any major surgery at least 4 weeks prior to first dose of 
MIRV and have recovered or stabilized from the side effects of prior surgery 
13. Patients must have adequate hematologic, liver and kidney functions defined as: 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
35 
a. Absolute neutrophil count (ANC) ≥ 1.5 x 109/L (1,500/μL) without G-CSF in the 
prior 10 days or long-acting WBC growth factors in the prior 20 days 
b. Platelet count ≥ 100 x 109/L (100,000/μL) without platelet transfusion in the prior 10 
days 
c. Hemoglobin ≥ 9.0 g/dL without packed red blood cell (PRBC) transfusion in the prior 
21 days 
d. Serum creatinine ≤ 1.5 x upper limit of normal (ULN) 
e. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3.0 x ULN  
f. Serum bilirubin ≤ 1.5 x ULN (patients with documented diagnosis of Gilbert 
syndrome are eligible if total bilirubin < 3.0 x ULN) 
g. Serum albumin ≥ 2 g/dL 
14. Patients or their legally authorized representative must be willing and able to sign the 
informed consent form (ICF) and to adhere to the protocol requirements 
15. Women of childbearing potential (WCBP) must agree to use highly effective 
contraceptive method(s) (as defined in Section 5.8.6) while on MIRV and for at least 3 
months after the last dose 
16. WCBP must have a negative pregnancy test within the 4 days prior to the first dose of 
MIRV 
 
3.1.2. 
Exclusion Criteria 
1. Male patients 
2. Patients with endometrioid, clear cell, mucinous, or sarcomatous histology, mixed tumors 
containing any of the above histologies, or low-grade/borderline ovarian tumor 
3. Patients with primary platinum-refractory disease, defined as disease that did not respond 
to (CR or PR) or has progressed within 3 months of the last dose of first-line platinum-
containing chemotherapy 
4. Patients with prior wide-field radiotherapy (RT) affecting at least 20% of the bone 
marrow 
5. Patients with > Grade 1 peripheral neuropathy per Common Terminology Criteria for 
Adverse Events (CTCAE) 
6. Patients with active or chronic corneal disorders, history of corneal transplantation, or 
active ocular conditions requiring ongoing treatment/monitoring, such as uncontrolled 
glaucoma, wet age-related macular degeneration requiring intravitreal injections, active 
diabetic retinopathy with macular edema, macular degeneration, presence of papilledema, 
and /or monocular vision 
7. Patients with serious concurrent illness or clinically relevant active infection, including, 
but not limited to the following: 
a. Active hepatitis B or C infection (whether or not on active antiviral therapy)  
b. Human immunodeficiency virus (HIV) infection 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
36 
c. Active cytomegalovirus infection  
d. Any other concurrent infectious disease requiring IV antibiotics within 2 weeks prior 
to the first dose of MIRV 
Note: Testing at screening is not required for the above infections unless clinically 
indicated 
8. Patients with a history of multiple sclerosis (MS) or other demyelinating disease and/or 
Lambert-Eaton syndrome (paraneoplastic syndrome) 
9. Patients with clinically significant cardiac disease including, but not limited to, any of the 
following: 
a. Myocardial infarction ≤ 6 months prior to first dose 
b. Unstable angina pectoris 
c. Uncontrolled congestive heart failure (New York Heart Association > class II) 
d. Uncontrolled ≥ Grade 3 hypertension (per CTCAE) 
e. Uncontrolled cardiac arrhythmias 
10. Patients with a history of hemorrhagic or ischemic stroke within 6 months prior to 
enrollment 
11. Patients with a history of cirrhotic liver disease (Child-Pugh Class B or C) 
12. Patients with a previous clinical diagnosis of noninfectious interstitial lung disease (ILD), 
including noninfectious pneumonitis 
13. Patients requiring use of folate-containing supplements (eg, folate deficiency) 
14. Patients with prior hypersensitivity to monoclonal antibodies (mAb) 
15. Women who are pregnant or breastfeeding 
16. Patients who received prior treatment with MIRV or other FRα-targeting agents 
17. Patients with untreated or symptomatic central nervous system (CNS) metastases 
18. Patients with a history of other malignancy within 3 years prior to enrollment  
Note: patients with tumors with a negligible risk for metastasis or death (eg, adequately 
controlled basal-cell carcinoma or squamous-cell carcinoma of the skin, or carcinoma in 
situ of the cervix or breast) are eligible 
19. Prior known hypersensitivity reactions to study drugs and/or any of their excipients 
Prospective approval of protocol deviations to recruitment and enrollment criteria, also known as 
protocol waivers or exemptions, is not permitted. 
4. 
INVESTIGATIONAL PLAN 
4.1. 
Study Design 
4.1.1. 
Overview and Schema 
This Phase 3 study is designed to evaluate the efficacy and safety of MIRV in patients with 
platinum-resistant high-grade serous EOC, primary peritoneal, or fallopian tube cancer, whose 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
37 
tumors express a high level of FRα. Patients will be, in the opinion of the Investigator, 
appropriate for single-agent- therapy. FRα expression will be defined by the Ventana FOLRI 
Assay. 
Approximately 110 patients who have provided informed consent and meet study entry criteria 
will be enrolled to achieve a total of 105 efficacy evaluable patients. Efficacy evaluable patients 
include those who have measurable lesions (per RECIST v1.1) at baseline and received at least 1 
dose of MIRV.  
Enrolled patients will receive single-agent MIRV at 6 mg/kg AIBW administered Q3W.  
Tumor response will be evaluated by the Investigator using RECIST v1.1. CT or MRI scans will 
be collected for sensitivity analysis by a BICR. 
Patients will continue to receive MIRV until PD, unacceptable toxicity, withdrawal of consent, 
death, or until the Sponsor terminates the study (whichever comes first).  
Tumor assessments, including radiological assessment by CT/MRI scan, will be performed at 
Screening and subsequently every 6 weeks (± 1 week) from C1D1 for the first 36 weeks then 
every 12 weeks (± 3 weeks) until PD, death, the start of new anticancer therapy, or patient’s 
withdrawal of consent, whichever occurs first.  
Patients who discontinue MIRV for reasons other than progressive disease (PD) will continue 
with tumor assessments until documentation of PD or the start of a new anticancer therapy, 
whichever comes first. Prior to Week 36 (from Cycle 1, Day 1), assessments should occur every 
6 weeks (± 1 week) as allowed by local requirements but must occur at an interval of no more 
than 12 weeks. After Week 36, assessment will occur every 12 weeks (± 3 weeks) until 
documentation of PD or the start of new anticancer therapy.  
All patients who discontinue study drug will be followed every 3 months (± 1 month) until death, 
lost to follow-up, withdrawal of consent for survival follow-up, or EOS, whichever comes first.  
There will be no interim analysis. 
4.1.2. 
Dose and Schedule for Mirvetuximab Soravtansine 
MIRV will be administered at 6 mg/kg on Day 1 of every 3-week cycle (Q3W). 
5. 
STUDY TREATMENT 
5.1. 
Mirvetuximab Soravtansine 
The investigational study drug, MIRV, will be provided by ImmunoGen, at a protein 
concentration of 5.0 mg/mL in an aqueous pH 5.0 buffered solution. See the Investigator 
Brochure for complete list of excipients. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
38 
5.1.1. 
Mirvetuximab Soravtansine Packaging 
MIRV will be provided in a 20 mL glass, single-use Type I vial. The container closure for the 
Type I glass vials will consist of a 20 mm ETFE-coated serum stopper (Flurotec®) with a 20 mm 
aluminum TruEdge® seal with blue Flip-off® top.  
Refer to the Pharmacy Manual for labeling information. 
5.1.2. 
Mirvetuximab Soravtansine Accountability 
Specific details regarding storage and handling of MIRV can be found in the Pharmacy Manual. 
Accountability and shipping documents for MIRV must be maintained by the Principal 
Investigator (PI) or designee (eg, the study pharmacist). The Investigator or designee must 
maintain an accurate record of all MIRV received, stored, dispensed, destroyed, and used in an 
Investigational Product Dispensing/Accountability Log or equivalent. These records must always 
be available for inspection, and a copy will be supplied to ImmunoGen on request. Information 
recorded on the Accountability Log will include dates and quantities of drug received, dates and 
quantities of drug dispensed, patient number and initials to whom drug is administered, lot 
number of drug administered, the recorder’s initials, and dates and quantities of drug destroyed 
or returned. Upon receipt, vials should be visually inspected for vial integrity (ie, cracks or leaks) 
and a record of any damaged or suspect drug should be kept on the Accountability Log. 
Upon completion of the study, all MIRV dispatched to a site must be accounted for and unused 
supplies destroyed according to the site’s Standard Operating Procedures (SOPs) or returned to 
depot (refer to Pharmacy Manual). The original drug reconciliation records shall be maintained 
at the site and a copy collected and sent to ImmunoGen or designee once a representative of the 
company has confirmed the drug accountability.  
Drug accountability will be monitored. 
5.1.3. 
Mirvetuximab Soravtansine Study Treatment Compliance 
MIRV supplied for the study may not be used for any purpose other than the study or 
administered other than as described in this protocol.  
If necessary, MIRV from different drug lots may be mixed in a single-dose administration. 
Under no circumstances is the Investigator allowed to release study drug supplies to any 
physician not named in the Food and Drug Administration (FDA) Form 1572 (or equivalent) to 
administer these supplies to a patient not enrolled in this study. If investigational supplies are to 
be dispensed from any facility other than that supervised directly by the PI (ie, hospital 
pharmacy, satellite pharmacy), it is the responsibility of the PI to ensure that all study drug is 
stored and administered as described (refer to Pharmacy Manual for instructions). 
5.2. 
Assignment of Patient Number 
Patient numbers are assigned in sequential order as patients sign the pre-screening informed 
consent to participate.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
39 
5.2.1. 
Enrolled Patient Definition 
Patients who have consented to the study and have received at least 1 dose of study treatment, 
are considered enrolled. Patients who are issued a patient number, but who do not successfully 
complete the screening process and are not treated will be considered screen failures. Patient 
numbers for patients who screen fail will not be re-issued. 
5.2.2. 
Patient Assignment to Dosing Regimens 
All patients will receive MIRV 6 mg/kg AIBW Q3W.  
5.3. 
Blinding Methods 
Not applicable as this is an open-label, single-arm study. 
5.4. 
Study Treatment Administration 
5.4.1. 
Premedication for Study Treatment 
All patients must receive 325 to 650 mg of acetaminophen/paracetamol (PO or IV), 10 mg IV 
dexamethasone, and 25 to 50 mg diphenhydramine (IV or PO) (equivalent drugs of similar drug 
classes is also acceptable) approximately 30 min before each infusion of MIRV. If individual 
patients require more intensive treatment to prevent infusion-related reactions (IRRs), 
investigators may modify the regimen accordingly. An antiemetic medication (eg, 5-HT3 
serotonin receptor antagonists such as palonosetron, granisetron or ondansetron or appropriate 
alternatives) is recommended before each MIRV dose and may be used any time at the discretion 
of the treating physician. 
5.4.2. 
Prophylactic use of Eye Drops 
5.4.2.1. 
Corticosteroid Eye Drops 
All patients will be mandated to use corticosteroid eye drops as prescribed by the treating 
physician unless the risk outweighs the benefit as per the ophthalmologist/physician. All patients 
will be instructed to self-administer 1% prednisolone (Pred Forte® or generic equivalent) 6 times 
daily on Days -1 to 4 and QID on Days 5 to 8 of each cycle during the study. For individual 
patients who cannot tolerate the preservative contained in 1% prednisolone, other corticosteroid 
eye drops may be substituted (eg, difluprednate 0.05%; Durezol®) and administered on Days -1 
to 8 of each cycle at a frequency prescribed by the ophthalmologist.  
5.4.2.2. 
Lubricating Artificial Tears 
Patients will be mandated to use preservative-free, lubricating artificial tears on a daily basis (as 
directed by the product label or the treating physician). Patients should be advised to wait at least 
15 minutes after corticosteroid eye drop administration before instilling lubricating eye drops.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
40 
5.4.3. 
Preparation and Administration of Mirvetuximab Soravtansine 
5.4.3.1. 
Calculation for Adjusted Ideal Body Weight 
The total dose of MIRV is calculated based on each patient’s AIBW using the following 
formula: 
Adjusted Ideal Body Weight (AIBW)  
AIBW = IBW1 + 0.4 (Actual weight – IBW1) 
Where: 
Ideal Body Weight (IBW)  
IBW1 (female) = 0.9H1-92 
1H=height in cm; W=weight in kg) 
The weight used for calculation should be obtained before study drug administration on C1D1 
(-14 days) and thereafter should only be modified for significant (≥ 10%) changes in body 
weight (not influenced by weight gain or loss attributed to fluid retention).  
5.4.3.1.1. Preparation 
MIRV is an experimental anticancer drug, and, as with other potentially toxic compounds, 
caution should be exercised when handling this compound. It is recommended that gloves and 
protective garments be worn during preparation. The desired amount of drug should be 
withdrawn from the vial(s) and diluted using 5% dextrose to a final concentration as outlined in 
the Pharmacy Manual.  
Note: MIRV is incompatible with saline (0.9% sodium chloride). Therefore, dilutions 
should be made using 5% dextrose. Infusion bags must be labeled with the protocol number, 
patient number, storage temperature, dose, and volume of MIRV filtered into the bag, or labeled 
according to institutional protocol. Once the solution is prepared, the infusion bag should be 
stored at room temperature protected from direct sunlight, and the infusion must be completed 
within eight hours of preparation. Please refer to Pharmacy Manual for further details. 
If necessary, MIRV from different drug lots may be mixed in a single-dose administration. 
5.4.3.1.2. Administration 
MIRV is administered at 6 mg/kg AIBW as an IV infusion following preparation as outlined in 
the Pharmacy Manual. Details on required and compatible infusion materials are also included in 
the Pharmacy Manual.  
At C1D1 MIRV should be administered at a rate of 1 mg/min; after 30 min, the rate can be 
increased to 3 mg/min if well tolerated. If well tolerated after 30 min at 3 mg/min, the MIRV 
infusion rate may be increased to 5 mg/min. Subsequent infusions may be delivered at the 
tolerated rate. Therefore, the overall length of infusion will vary depending on dose and patient 
tolerability. After infusion, the IV line should be flushed with 5% dextrose as needed (PRN) to 
ensure delivery of the full dose.  




Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
42 
5.5.1.1. 
Mirvetuximab Soravtansine-Related Adverse Events 
Dose modifications for MIRV-related AEs are described in Table 3.  
Table 3: 
Dose Modifications for Mirvetuximab Soravtansine-Related Adverse Events 
Severity Grade 
(CTCAE v5.0) 
Dose Modifications for MIRV a 
Hematological  
Neutropenia 
Grade 2 and Grade 3  
Hold drug until ANC is ≥ 1.5 x109/L (1500 /µL) and 
resume at the same dose level  
Grade 4 
Hold drug until ANC is ≥ 1.5 x109/L (1500 /µL) and 
then resume at one lower dose level 
Febrile neutropenia Grade 3 or 4 
(with a single temperature reading ≥ 38.3°C or a 
sustained temperature of > 38°C for > 1 hour 
Hold drug until ANC is ≥ 1.5 x109/L (1500 /µL) and 
then resume at one lower dose level 
Thrombocytopenia 
 
Grade 2 and Grade 3  
Hold drug until PLT count is ≥ 100 x 109/L 
(100,000/µL) and resume at same dose level  
Grade 3 associated with clinically significant 
bleeding that requires transfusion therapy and 
Grade 4 
Hold drug until PLT count is ≥ 100 x 109/L 
(100,000/µL) and then resume at one lower level 
Non-hematological 
Nausea and Vomiting 
Grade 3 (despite use of optimal antiemetics) 
Hold drug until resolved to ≤ Grade 1, then resume 
at one lower level 
Grade 4  
Permanently discontinue 
Diarrhea 
Grade 3 (despite use of optimal anti-diarrheal 
treatment) 
Hold drug until resolved to ≤ Grade 1, then resume 
at one lower level 
Grade 4 
Permanently discontinue 
Ocular Disorders  
Refer to Section 5.5.2  
Noninfectious Pneumonitis 
Refer to Section 5.5.3 
Infusion-related Reactions 
Refer to Section 5.5.5 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
43 
Table 3: 
Dose Modifications for Mirvetuximab Soravtansine-Related Adverse Events 
(Continued) 
Severity Grade 
(CTCAE v5.0) 
Dose Modifications for MIRV a 
All Other Non-hematological Toxicities  
(except AEs related to underlying disease, Grade 3 fatigue, isolated symptomatic Grade 3 biochemistry 
laboratory abnormalities that last for < 7 days including electrolyte abnormalities that respond to 
medical intervention) 
Grade 3  
Hold drug until resolved to ≤ Grade 1, then resume 
at one lower level 
For any Grade 3 hepatic toxicity that does not 
resolve to baseline within seven days, an abdominal 
CT scan must be performed to assess whether it is 
related to disease progression. 
≥ Grade 3 Cardiac events (excluding Grade 3 
hypertension)  
Permanently discontinue 
Grade 4 non-hematological toxicities 
Permanently discontinue 
Abbreviations: CTCAE = common terminology criteria for adverse events; ANC = absolute neutrophil count; PLT = 
platelets; CT = computed tomography; AE = adverse event. 
a Failure to meet retreatment criteria within 1 cycle (21 days) after the missed dose due to insufficient recovery from 
a treatment-related toxicity will result in treatment discontinuation unless otherwise specified in the management 
guidance for a particular toxicity.  
5.5.1.2. 
Mirvetuximab Soravtansine Dose Reduction Dose Levels 
MIRV dose reduction will be as described in Table 4.  
Table 4: 
Mirvetuximab Soravtansine Dose Reduction Dose Levels 
If the patient was receiving MIRV at: 
Dose should be reduced to: 
6.0 mg/kg AIBW 
5.0 mg/kg AIBW 
5.0 mg/kg AIBW 
4.0 mg/kg AIBW 
4.0 mg/kg AIBW 
Permanently discontinue 
Reduction of MIRV below 4.0 mg/kg will not be permitted. Dose re-escalation is not permitted.  
Abbreviations: AIBW = adjusted ideal body weight; MIRV = mirvetuximab soravtansine. 
5.5.1.3. 
Monitoring and Management of Nausea and Vomiting 
Treatment-related nausea (46% all grade; 1% Grade 3+) and vomiting (16% all grade; 
1% Grade 3+) have been reported in patients treated with MIRV, despite premedication with 
dexamethasone. Therefore, it is recommended that an antiemetic (eg, 5-HT3 serotonin receptor 
antagonists such as palonosetron, granisetron or ondansetron) medication is provided before each 
MIRV dose (Section 5.8.1). Additional antiemetics may be used any time at the discretion of the 
treating physician, according to institutional or other practice guidelines American Society of 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
44 
Clinical Oncology (ASCO), ESMO, and NCCN. Patients should be advised to contact their 
treating physician at the first sign of vomiting or worsening nausea.  
5.5.1.4. 
Monitoring and Management of Diarrhea 
Mild to moderate diarrhea has been reported in patients treated with MIRV. Patients should be 
advised to contact their treating physician at the first sign of diarrhea. Patients may then be 
treated according to standard institutional practice. One suggested regimen would be the 
administration of loperamide 2 mg at the first sign of loose stool, with repeat dosing every 
two hours until symptoms resolve (Wadler 1998). 
5.5.2. 
Ocular Disorders 
Changes in visual acuity resulting from reversible keratopathy have been reported in other 
studies of DM4-containing immunoconjugates that use the SPDB linker (Younes 2012). Patients 
receiving MIRV in the Phase 1 and 3 trials (IMGN853-0401, IMGN853-0403) reported ocular 
AEs consistent with reversible keratopathy/corneal epitheliopathy.  
5.5.2.1. 
Monitoring and Preventive Measures 
In early dose escalation of Study 0401, a relationship was observed between MIRV plasma 
exposure and likelihood of an ocular event and response. Exposure-response modeling suggested 
that a dose of 6.0 mg/kg AIBW provided adequate exposure for response while also maintaining 
overall exposure within a range that decreased the potential for ocular AEs. Due to the 
observation of ocular disorders consistent with reversible keratopathy/corneal epitheliopathy in 
patients treated with MIRV, ocular function will be carefully monitored. Ocular symptom 
assessments will be performed at baseline and at Day 1 of every cycle thereafter (Table 2). 
Complete ophthalmologic exams will be performed in all patients at baseline and every other 
cycle thereafter if there is a TEAE reported. 
Patients are advised to avoid using contact lenses while on MIRV. Baby shampoo and a soft 
cloth should be used to clean the eyes, and a warm compress at bedtime may be used to decrease 
any possible inflammation on the eyelid’s surface. Please refer to Section 5.4.2.1 and 
Section 5.4.2.2 for details on the prophylactic use of steroid eye drops and lubricating artificial 
tears. The use of UVA/UVB sunglasses is recommended in full daylight during the study. The 
use of temporary lower punctal plugs to increase lubrication of the eyes is optional if lubricating 
artificial tears and corticosteroid eye drops are not sufficient. If patients report signs or 
symptoms of ocular disorders, including, but not limited to, blurred vision or eye irritation, the 
management and dose modification guidelines outlined in Table 5 should be followed.  
5.5.2.2. 
Management and Dose Modification Guidelines 
If a patient develops ocular symptoms of any grade, the patient is required to have a complete 
examination by an ophthalmologist. If a patient develops ≥ CTCAE Grade 2 ocular symptoms, 
treatment with MIRV must be interrupted. Treatment should not be interrupted solely for Grade 
2 ocular signs (eg, Grade 2 keratopathy) unless they are also associated with Grade 2 ocular 
symptoms. Treatment with MIRV may resume if ocular symptoms improve to Grade 1 or 
baseline within 28 days of the next scheduled MIRV dose (refer to Table 5 for details). If ocular 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
45 
symptoms last longer than 28 days, resumption of MIRV, with or without dose reduction, may be 
considered for those patients who have experienced clinical benefit if agreed upon between the 
Sponsor and the Investigator. Subsequent eye examinations will be scheduled to occur in every 
other cycle going forward, from the time that the AE was initially reported, and at either the EOT 
visit or 30-Day Follow-up Visit after treatment discontinuation, even if the results of the 
patient’s ocular exam shows no obvious clinical findings. Management of treatment-emergent 
ocular AEs with inflammatory characteristics should include corticosteroid eye drops and/or 
other measures as indicated by an ophthalmologist. 
Table 5: 
Management of Ocular Symptoms 
Severity Grade 
(CTCAE v5.0) 
Management 
Guidelines for MIRV Dose 
Modifications 
Grade 1  
Complete eye exam as outlined in Schedule 
of Assessments (Table 2) 
Monitor for worsening symptoms 
Continue MIRV dosing 
Grade 2 
Complete eye exam as outlined in Schedule 
of Assessments (Table 2) 
Repeat complete exam as clinically 
indicated  
Patients should have weekly symptomatic 
ocular assessments by the Investigator until 
the symptoms resolve to Grade 1 or 
baseline or are deemed to be irreversible by 
the Investigator 
Hold MIRV dosing until AE has 
resolved to Grade 1 or better  
Patients with ocular symptoms 
lasting < 14 days may be allowed 
to resume MIRV at the same dose 
level 
Patients with ocular symptoms 
lasting ≥ 14 days but no more than 
28 days may resume MIRV at one 
lower dose level  
Recurrence of Grade 2 toxicity on 
subsequent cycles despite best 
supportive care will require a 
MIRV dose reduction of one dose 
level 
Grade 3  
Complete eye exam as outlined in Schedule 
of Assessments (Table 2). Repeat complete 
exam as clinically indicated 
Patients should have weekly symptomatic 
ocular assessments by the Investigator until 
the symptoms resolve to Grade 1 or 
baseline or are deemed to be irreversible by 
the Investigator 
Hold MIRV dosing  
Patients may be allowed to resume 
MIRV at a lower dose after AE has 
resolved to Grade 1 or better within 
28 days 
Recurrence of Grade 3 toxicity on 
subsequent cycles despite best 
supportive care will require a 
MIRV dose reduction of one dose 
level 
Grade 4  
Complete eye exam as outlined in Schedule 
of Assessments (Table 2). Repeat complete 
exam as clinically indicated 
Patients should have weekly symptomatic 
ocular assessments by the Investigator until 
Permanently discontinue MIRV 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
46 
Severity Grade 
(CTCAE v5.0) 
Management 
Guidelines for MIRV Dose 
Modifications 
the symptoms resolve to Grade 1 or 
baseline or are deemed irreversible by the 
Investigator 
Abbreviations: AE = adverse event; CTCAE = common terminology criteria for adverse events; MIRV = 
mirvetuximab soravtansine. 
5.5.3. 
Monitoring of Noninfectious Pneumonitis 
Noninfectious pneumonitis has been observed after the administration of MIRV. Noninfectious 
pneumonitis may result in fatigue, shortness of breath, cough, or respiratory distress. Drug-
induced pneumonitis may be immediately life threatening. If a patient presents with signs or 
symptoms consistent with pneumonitis and/or other clinically meaningful signs or symptoms of 
pulmonary toxicity, the patient should be immediately evaluated. Patients are advised to notify 
their treating physician immediately if they experience new or worsening shortness of breath, 
cough, or respiratory distress. Patients who are asymptomatic may continue dosing of MIRV 
with close monitoring. 
The management and treatment guidelines outlined in Table 6 should be followed. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
47 
Table 6: 
Management of Noninfectious Pneumonitis 
CTCAE 
v5.0 
Grade 
CTCAE v5.0 
Definition 
Medical Management of 
Pneumonitis 
Guidelines for Dose 
Modificationsa 
Grade 1 
Asymptomatic; 
clinical or 
diagnostic 
observations 
only; 
intervention not 
indicated 
• 
Radiologic assessments (CT scan 
and/or chest x-ray) should be 
performed as clinically indicated. 
• 
Monitor for pulmonary 
symptoms. 
• 
Continue dosing in 
asymptomatic patients 
and monitor closely.  
Grade 2 
Symptomatic; 
medical 
intervention 
indicated; 
limiting 
instrumental 
ADL 
• 
Radiologic assessments (CT scan 
and/or chest x-ray) should be 
performed as clinically indicated. 
• 
Patient must be evaluated by a 
pulmonary specialist.  
• 
Treatment with corticosteroids 
may be indicated as 
recommended by a pulmonary 
specialist and/or institutional 
guidelines. 
• 
Hold dosing until 
symptoms resolve to  
≤ Grade 1. 
• 
MIRV may be resumed 
at same dose level or 
one dose level lower 
after discussion with the 
Sponsor. 
Grade 3 
Severe 
symptoms; 
limiting self-
care ADL; 
oxygen 
indicated 
• 
Radiologic assessments (CT scan 
and/or chest x-ray) should be 
performed as clinically indicated.  
• 
Patient must be evaluated by a 
pulmonary specialist.  
• 
Treatment with corticosteroids 
until resolution of symptoms may 
be indicated as recommended by 
a pulmonary specialist and/or 
institutional guidelines.  
• 
Bronchoscopy with lavage and/or 
biopsy when clinically feasible 
should be performed.  
• 
The pneumonitis event must be 
followed until resolution. 
• 
Permanently discontinue 
MIRV.  
Grade 4 
Life-threatening 
respiratory 
compromise; 
urgent 
intervention 
indicated (eg, 
tracheotomy or 
intubation) 
Abbreviations: ADL = activities of daily living; AE = adverse event; CT = computed tomography; MIRV = 
mirvetuximab soravtansine. 
a Failure to meet retreatment criteria within 1 cycle (21 days) after the missed dose due to insufficient recovery from 
a treatment-related toxicity will result in treatment discontinuation unless otherwise specified in the management 
guidance for a particular toxicity.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
48 
5.5.4. 
Management of Electrolytes Imbalance 
Prompt attention should be given to the correction of potential electrolytes imbalance, especially 
hypokalemia and hypomagnesemia. 
5.5.5. 
Potential Infusion-related Reactions 
Some patients treated with IV infusions of therapeutic drugs have experienced concurrent 
infusion-related reactions (IRR) (see CTCAE Version 5.0). The signs and symptoms may vary 
and include for example, headache, fever, facial flushing, pruritus, myalgia, nausea, chest 
tightness, dyspnea, vomiting, erythema, abdominal discomfort, diaphoresis, shivers, 
lightheadedness, hypotension, palpitations, and somnolence. Anaphylaxis might occur at any 
time during an infusion. Before any infusion is started, appropriate medical personnel, 
medication (eg, epinephrine, inhaled beta agonists, antihistamines, and corticosteroids), and 
other required resources to treat anaphylaxis must be readily available. In general, Investigators 
should manage acute allergic or hypersensitivity reactions according to Institutional practices. 
General guidelines for the management of acute IRRs and for subsequent retreatment are 
provided in Table 7. Delayed IRRs may occur; therefore, patients should be advised to seek 
immediate medical treatment if symptoms newly develop and/or recur after discharge from 
clinic. 
Patients who experience ≥ Grade 2 IRR during or immediately after administration of MIRV will 
have blood drawn for determination of drug concentration and ADAs to MIRV. The sample 
should be obtained within three hours of the onset of the reaction and one week later. Such 
patients should undergo all scheduled efficacy and safety evaluations. 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
49 
Table 7: 
Management Guidelines for Potential Infusion-Related Reactions  
Infusion Reaction 
CTCAE v5.0 Severity 
Grade 
Management 
Grade 1: Mild, transient 
reaction 
• 
Maintain infusion rate unless progression of symptoms to ≥ Grade 2; if 
symptoms worsen, refer to guidelines below. 
• 
Promethazine (or equivalent) 150 mg PO per day (Q4h) PRN for nausea  
• 
Diphenhydramine (or equivalent) 25-50 mg PO or IV PRN 
• 
Methylprednisolone (or equivalent) 125 mg IV PRN 
Grade 2: Moderate  
• 
Interrupt infusion and disconnect infusion tubing from patient 
• 
Promethazine (or equivalent) 150 mg PO per day (Q4h) PRN for nausea 
• 
Diphenhydramine (or equivalent) 25-50 mg PO or IV PRN 
• 
Acetaminophen (or equivalent) 650 mg PO PRN 
• 
Methylprednisolone (or equivalent) 125 mg IV PRN 
• 
After recovery from symptoms, resume the infusion at 50% of the 
previous rate and if no further symptoms appear, gradually increase rate 
until infusion is completed. 
• 
For subsequent dosing in future cycles, patients should be pre-medicated 
with Dex (or equivalent) 8 mg PO BID the day before drug 
administration and acetaminophen (or equivalent) 650 mg PO and 
diphenhydramine (or equivalent) 25-50 mg PO 30-60 min before dosing.  
Grade 3: Severe, 
prolonged reaction not 
rapidly responsive to 
symptomatic 
medication and/or brief 
interruption of infusion; 
recurrence of 
symptoms after initial 
improvement; 
hospitalization 
indicated for clinical 
sequelae 
OR 
Grade 4: Life-
threatening 
consequences, urgent 
intervention indicated 
• 
Immediately stop infusion and disconnect infusion tubing from patient. 
• 
Administer diphenhydramine (25-50 mg) IV (or equivalent) 
• 
Administer IV steroids (methylprednisolone (or equivalent) up to 
0.5mg/kg Q 6h) to treat ongoing reaction and prevent recurrence 
• 
Administer bronchodilators (nebulized albuterol/salbutamol, 2.5-5 mg in 
3 mL of saline or equivalent) as medically indicated 
• 
Administer normal saline as medically indicated 
• 
Administer epinephrine (0.2-0.5 mL of a 1:1000 dilution (0.2-0.5 mg) 
SQ or IM) as medically indicated. Epinephrine should only be used if all 
other treatment methods fail to manage the IRR. 
• 
Advise patient to seek emergency treatment and notify 
Investigator/clinic if the infusion-related symptoms recur after discharge 
from clinic. 
• 
Report as an SAE (see Section 8.1.1.2). 
• 
Permanently discontinue study medication treatment 
Abbreviations: BID = twice a day; CTCAE = common terminology criteria for adverse events; Dex = 
dexamethasone; IM = intramuscular; IRR = infusion-related reaction; IV = intravenously; PO = orally; PRN = as 
needed; SAE = serious adverse event; SQ = subcutaneous.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
Confidential and Proprietary 
ImmunoGen, Inc. 
50 
5.5.6. 
Discontinuation of Mirvetuximab Soravtansine Due to Toxicity 
MIRV should be discontinued in the case of the following treatment-related events: 
•
Grade ≥ 3 cardiac event (excluding Grade 3 hypertension) (Section 5.5.1.1)
•
Grade ≥ 3 pneumonitis event (Section 5.5.3)
•
Non-hematologic events of Grade 4 severity (Section 5.5.1.1)
•
Ocular events of Grade 4 severity (Section 5.5.2.2)
•
Failure to meet re-treatment criteria within 1 cycle (21 days) after the missed dose
due to insufficient recovery from a treatment-related toxicity unless otherwise
specified in the management guidance for a particular toxicity. In such cases,
continuation of MIRV may be considered for those patients who have experienced
clinical benefit if agreed upon between the Sponsor and the Investigator.
5.6. 
Discontinuation of the Patients from the Study or Study Treatment
5.6.1. 
End of Treatment
Patients will continue to receive MIRV until they present with PD per RECIST 1.1, as assessed 
by study Investigator, unacceptable toxicity, withdraw consent, or death, whichever comes first, 
or until the Sponsor terminates the study. Study treatment and/or participation in the study may 
be discontinued at any time at the discretion of the Investigator. The following may be reasons 
for the Investigator to remove a patient from the study drug: 
•
The patient suffers an intolerable AE
•
Noncompliance, including failure to appear at one or more study visits
•
The patient was erroneously included in the study
The reason for treatment discontinuation must be captured in the clinical trial database. Any AEs 
experienced up to the point of discontinuation and 30 days thereafter must be documented. All 
serious adverse events (SAEs), and those AEs assessed by the Investigator as at least possibly 
related to study drug should continue to be followed until they resolve or stabilize, whichever 
comes first. Patients will continue to be followed for OS, after discontinuing study drug 
(Section 9.3.3).  
5.6.2. 
End of Study 
Discontinuation from participation in the study will be documented in the clinical trial database. 
Reasons for EOS include withdrawal of consent, lost to follow-up, death, or study termination by 
Sponsor.  
5.6.3. 
Withdrawal of Consent 
The patient or legally authorized representative acting on behalf of the patient is free to withdraw 
consent to study treatment and/or participation in the study at any time irrespective of the reason. 
The Investigator must make every effort (eg, telephone, email, letter) to determine the primary 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
51 
reason for this decision and record this information. Study treatment must be discontinued, and 
no further assessments conducted. Further attempts to contact the patient are not allowed unless 
safety findings require communication or follow-up. If the patient or legally authorized 
representative withdraws consent for disclosure of future information, the Sponsor may retain 
and continue to use any data collected before withdrawal of consent. All biological samples that 
have been already collected will be retained and analyzed at a later date. The patient or legally 
authorized representative may request destruction of any samples, and the Investigator must 
document this in the site study records. The SAP will specify how early withdrawals from 
treatment will be accounted for in the analyses of efficacy endpoints. Patients who have 
withdrawn from the study cannot be re-treated in the study and their inclusion and patient 
number must not be reused. 
5.6.4. 
Lost to Follow-up 
A study patient will be considered lost to follow-up if the patient repeatedly fails to return for 
scheduled visits and is unable to be contacted by the study site. The Investigator should make all 
efforts to contact the patient and to determine the patient’s health status, including at least her 
vital status (in accordance with applicable regulations related to privacy and confidentiality). A 
patient should not be considered lost to follow-up until due diligence has been completed and 
documented. The following actions must be taken if a patient fails to return to the clinic for a 
required study visit: 
• The site must attempt to contact the patient and reschedule the missed visit as soon as 
possible and counsel the patient on the importance of maintaining the assigned visit 
schedule and ascertain whether or not the patient wishes to and/or should continue in 
the study. 
• In cases in which the patient is deemed lost to follow-up, the Investigator or designee 
must make every effort to regain contact with the patient (where possible, 3 telephone 
calls and, if necessary, a certified letter to the patient’s last known mailing address or 
local equivalent methods). These contact attempts should be documented in the 
patient’s medical record. 
Should the patient continue to be unreachable, he/she will be considered to have withdrawn from 
the study with a primary reason of lost to follow-up. 
5.7. 
Period of Observation 
For purposes of this study, the period of safety observation extends from the time of informed 
consent until the 30-Day Follow-up visit unless additional follow-up safety information is 
requested as described in Section 9.3. Short-term follow-up for patients who discontinue study 
drug without documented PD will be followed per RECIST 1.1 every 6 weeks (± 1 week) from 
C1D1 for the first 36 weeks then every 12 weeks (± 3 weeks) until PD, until the patient starts 
new anticancer treatment, the patient dies, or the patient withdraws consent, whichever comes 
first. All patients will be followed every 3 months (± 1 month) for survival until death, lost to 
follow-up, withdrawal of consent for survival or until EOS, whichever comes first. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
52 
5.8. 
Concomitant Medications and Procedures 
All concomitant medications and supportive therapy taken within four weeks of Cycle 1, Day 1 
and through 30 days after last study treatment must be recorded in the clinical database.  
5.8.1. 
Antiemetic and Antidiarrheal Medications 
An antiemetic (eg, 5-HT3 serotonin receptor antagonists such as palonosetron, granisetron or 
ondansetron) medication is recommended before each MIRV dose; additional antiemetics and/or 
antidiarrheal (eg, loperamide) medications may be used any time at the discretion of the treating 
physician. 
5.8.2. 
Folate-Containing Supplements 
Folate-containing supplements should not be taken during the study. 
5.8.3. 
Antineoplastic Therapy 
All non-study related antineoplastic therapy, including but not limited to cytotoxic, 
immunotherapy, and VEGF-targeted therapy, is prohibited while on study drug.  
5.8.4. 
Hematopoietic Growth Factors 
Patients receiving recombinant erythropoietin (EPO) or darbepoetin-α before study start may 
continue to receive pretreatment doses.  
The use of erythropoietic and granulocyte growth factors in accordance with ASCO guidelines 
may be implemented at the discretion of the treating physician. 
5.8.5. 
Anticoagulants 
The use of anticoagulant agents is allowed. Please see Section 5.8.8 if using apixaban and 
rivaroxaban due to CYP3A interaction potential. 
5.8.6. 
Methods of Contraception 
Women of childbearing potential must agree to use highly effective contraceptive method(s) 
while on study drug and for at least 3 months after the last dose of MIRV. A woman of 
childbearing potential is a woman who is considered fertile, following menarche and until 
becoming post-menopausal unless permanently sterile. Permanent sterilization methods include 
hysterectomy, bilateral salpingectomy and bilateral oophorectomy. 
The following birth control methods may be considered highly effective (failure rate of less than 
1% per year): 
• Combined (estrogen and progesterone) hormonal contraception associated with 
inhibition of ovulation 
− Oral 
− Intravaginal 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
53 
− Transdermal 
• Progesterone-only hormonal contraception associated with inhibition of ovulation: 
− Oral 
− Injectable 
− Implantable 
• Intrauterine device (IUD) 
• Intrauterine hormone-releasing system (IUS) 
• Bilateral tubal occlusion 
• Vasectomized partner  
• Sexual abstinence 
Abstinence (relative to heterosexual activity) can be used as the sole method of contraception if 
it is consistently employed as the patient’s preferred and usual lifestyle and if considered 
acceptable by local regulatory agencies and Institutional Review Board/Independent Ethics 
Committee (IECs /IRBs). Periodic abstinence (eg, calendar, ovulation, symptom-thermal, post-
ovulation methods, etc) and withdrawal are not acceptable methods of contraception.  
If a contraceptive method listed above is restricted by local regulations/guidelines, then it does 
not qualify as an acceptable method of contraception for patients participating at sites in this 
country/region. 
Patients should be informed that taking the study medication may involve unknown risks to the 
fetus (unborn baby) if pregnancy were to occur during the study. To participate in the study 
WCBP must adhere to the contraception requirement (described above) from the day of study 
medication initiation (or 14 days before the initiation of study medication for oral contraception) 
through the duration of study treatment and for at least 3 months after the last dose of MIRV. If 
there is any question that a WCBP will not reliably comply with the requirements for 
contraception, that patient should not be entered into the study. 
5.8.7. 
Other Concomitant Medications 
Medications for the treatment of AEs or cancer symptoms (eg, packed red blood cells and pain 
medications), are allowed. Prophylactic use of steroids and/or antihistamines will be considered 
if needed. Additionally, medications (not addressed above) used to treat underlying medical 
conditions at study entry including antiemetics and antidiarrheals will be allowed to continue.  
5.8.8. 
Medications that are CYP3A or MDR1 Substrates or CYP3A Substrates with 
Narrow Therapeutic Index 
In vitro metabolism studies demonstrated that DM4 is predominantly metabolized by thiol s-
methyltransferase (TMT) to form S-methyl DM4, which is further metabolized into sulfoxide-
methyl-DM4. As S-methyl DM4 has been shown to be primarily metabolized by CYP3A, its 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
54 
exposure could potentially be increased in the presence of strong CYP3A inhibitors. Drinking 
greater than one serving (250 mL) of grapefruit juice per day should be avoided. 
Both DM4 and S-methyl DM4 are substrates for MDR1 efflux transporter. Their exposure could 
potentially increase in the presence of MDR1 efflux transporter. In vitro metabolism data also 
indicates that DM4 is a time-dependent inhibitor of CYP3A4.The risk of a significant in vivo 
drug-drug interaction caused by inhibition of CYP3A4 or MDR1 is unknown. Treatment of 
patients with concomitant medications that are inhibitors of MDR1, sensitive substrates of 
CYP3A or are CYP3A substrates with a narrow therapeutic index should be used with caution 
and carefully monitored (Appendix D).  
5.9. 
Overdose and Medication Error 
5.9.1. 
Overdose 
There is no known treatment/antidote available for MIRV. Supportive measures should be 
instituted if an instance arises in which a patient suffers an overdose of study drug. 
5.9.2. 
Medication Error 
The Sponsor must be notified within 24 hours of any error leading to the administration of either 
10% more or 10% less than the intended dose; in such cases, the event must be reported in the 
clinical trial database. If an error resulted in a SAE, a Serious Adverse Event form must be 
submitted within 24 hours of the event (see Section 8.2.1). 
6. 
PHARMACOKINETIC, IMMUNOGENICITY, AND 
BIOMARKER ASSESSMENTS 
6.1. 
Pharmacokinetic Assessments – Mirvetuximab Soravtansine 
The PK properties of MIRV and key metabolites will be evaluated following IV administration, 
as outlined in Table 2 and Table 8. Plasma samples will be collected to determine the 
concentration of MIRV (conjugate, total Ab, free DM4, S-methyl DM4 and possibly other 
metabolites). 
Blood samples for PK analysis will be taken at the following timepoints:  






Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
57 
they will sign the main study ICF and proceed with remaining screening procedures per the 
Schedule of Assessments. In some cases, the pre-screening ICF and main study ICF may be 
merged into a single ICF based on site-specific guidelines or preference. 
7.2. 
Inclusion and Exclusion Criteria 
The inclusion and exclusion criteria are assessed during Screening (within 28 days before the 
first dose of MIRV on Cycle 1, Day 1). All screening evaluations must be completed and 
reviewed to confirm that potential patients meet all eligibility criteria. The Investigator will 
maintain a screening log to record details of all participants screened and to confirm eligibility or 
record reasons for screening failure, as applicable. Procedures conducted as part of the patient’s 
routine clinical management and obtained before signing an ICF may be utilized for screening or 
baseline purposes provided the procedure met the protocol-specified criteria and were performed 
within the timeframe defined in the Schedule of Assessments (Table 2). A patient is considered 
enrolled when they have received their first dose of MIRV (Section 5.2.1). 
7.3. 
Confirmation of Disease Diagnosis 
At Screening, disease diagnosis, and current disease status are confirmed from information in the 
source record (Table 2). 
7.4. 
BRCA Mutation Status 
The BRCA mutation status from prior testing (information in the source record) will be recorded 
(Table 2). Patients with a BRCA mutation (germline mutation or somatic mutation in tumor 
tissue) are classified as positive and patients who were tested and shown to not have a BRCA 
mutation will be classified as negative. Patients without known BRCA mutation status in the 
source record are classified as unknown. If a patient with unknown status is tested and is found 
to have a BRCA mutation, this patient is considered BRCA mutation positive in analyses. 
7.5. 
Demographic/Medical History 
The age, sex, race and ethnicity of the patient are to be recorded during Screening for all patients 
who consent to the study (Table 2). 
During the Screening period, a complete medical history will be compiled for each patient. The 
history will include the background and progress of the patient’s primary malignancy and 
include a description of all prior therapies for the primary malignancy. 
7.6. 
Physical Examination, Weight, and Height 
Physical examination (PE), height (Screening only) and weight must be performed as indicated 
in the Schedule of Assessments (Table 2). A complete PE, including assessments of general 
appearance, skin, head (eyes, ears, nose, and throat), neck, lungs, heart, abdomen, back, lymph 
nodes, extremities, and neurological system, will be completed at Screening and at the 30-Day 
Follow-up Visit. Directed PEs will be completed at additional time points as specified in the 
Schedule of Assessments. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
58 
7.7. 
Vital Signs 
Vital signs include BP and body temperature. These signs are measured as outlined in Table 2. 
7.8. 
Electrocardiogram (ECG) 
A standard, single 12-lead ECG will be performed within 28 days prior to first dose.  
7.9. 
Ocular Symptom Assessment and Ophthalmic Examination 
7.9.1. 
Ocular Symptom Assessment 
Ocular symptom assessment will be performed before the start of each cycle by the treating 
physician or other qualified individual. For patients reporting > CTCAE Grade 1 ocular 
symptoms, study drug will be held until the patient is evaluated by an ophthalmologist for a 
complete examination. The ocular symptom assessment will also be performed at EOT and the 
30-Day Follow-up visit. 
7.9.2. 
Ophthalmic Examination 
An ophthalmic examination will be performed at Screening (within 14 days prior to first dose of 
study drug) by an ophthalmologist and will include the following: distant visual acuity, best 
corrected visual acuity, slit lamp examination, intraocular pressure measurement, and indirect 
fundoscopy. Patients who experience ocular TEAEs while on study will have a complete 
ophthalmologic exam performed at the emergence of the symptoms and at every other cycle 
thereafter. All patients who have an ophthalmic exam on study treatment (post-baseline) will 
have a complete ophthalmologic exam performed at the EOT visit or 30-Day Follow-up visit 
(Table 2). 
7.10. 
Laboratory Assessments 
Local laboratories will be used for the analysis of scheduled hematology, biochemistry, 
coagulation, and other tests collected as part of safety monitoring. Screening labs (Table 9) will 
be performed within 14 days of first dose. Repeat testing on Cycle 1, Day 1 is not required if 
tests were obtained within 4 days of dosing and are within acceptable ranges. Repeat testing will 
be performed as outlined in the Schedule of Assessments (Table 2) and as clinically indicated.  
Note that before each administration of study drug, laboratory results must be reviewed to 
evaluate for potential toxicity.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
59 
7.10.1. 
Clinical Laboratory Panels 
A list of clinical laboratory tests may be found in Table 9. 
Table 9: 
Clinical Laboratory Tests 
Hematology 
Serum Chemistry 
Urinalysis 
(Screening only) 
Coagulation 
(Screening only) 
• 
Hematocrit 
• 
Hemoglobin 
• 
WBC (with 5-part 
differential)  
• 
Platelet count 
• 
Albumin 
• 
Alkaline 
phosphatase 
• 
ALT 
• 
AST 
• 
BUN or Urea 
• 
Calcium 
• 
Chloride 
• 
Creatinine 
• 
Glucose 
• 
Magnesium 
• 
Phosphorus 
• 
Potassium  
• 
Sodium 
• 
Total bilirubin 
• 
pH 
• 
Ketones 
• 
Protein 
• 
Glucose 
• 
Occult blood 
• 
Leukocyte esterase 
• 
Nitrite 
• 
PT or INR 
• 
aPTT 
Abbreviations: ALT = alanine aminotransferase; aPTT = activated partial thromboplastin time; AST = aspartate 
aminotransferase; BUN = blood urea nitrogen; INR = international normalized ratio; PT = prothrombin time; WBC 
= white blood cell count.  
7.11. 
Pregnancy Screen 
All WCBP will complete a serum beta-human chorionic gonadotropin (β-hCG) or urine 
pregnancy test within 4 days before the first dose of study drug and urine or serum pregnancy 
tests within 4 days of each study drug administration and at the 30-Day Follow-up visit. It is 
recommended to perform monthly pregnancy tests for 3 months after the last dose of MIRV. 
Additional testing may be performed in accordance with institutional requirements or local 
regulation. Pregnancy tests must be negative for the patient to be enrolled and to continue to 
receive the study drug (Table 2). 
If a patient becomes pregnant or suspects pregnancy while participating in this study, the 
Investigator and Sponsor must be informed immediately (Section 8.2.2) and the patient will be 
withdrawn from study drug. See Section 8.2.2 for more details.  
7.12. 
Eastern Cooperative Oncology Group Performance Status 
ECOG PS (Appendix A) will be assessed during Screening and at other times specified in the 
Schedule of Assessments (Table 2). An assessment is not necessary on Day 1 of Cycle 1 if the 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
60 
Screening assessment was obtained within the prior 4 days. ECOG is also assessed at EOT and 
30 day follow up visit. 
7.13. 
Tumor Response Assessment 
7.13.1. 
Radiological Imaging 
Radiologic tumor evaluation by CT or MRI of chest, abdomen, and pelvis will be performed 
within 28 days before first dose of study drug and every 6 weeks (±1 week) from C1D1 for the 
first 36 weeks on study and every 12 weeks (± 3 weeks) thereafter (Table 2). Patients who 
discontinue study treatment for reasons other than progressive disease (PD) will continue with 
tumor assessments until documentation of PD or the start of a new anticancer therapy, whichever 
comes first. Prior to Week 36 (from Cycle 1, Day 1), assessments should occur every 6 weeks 
(± 1 week) as allowed by local requirements but must occur at an interval of no more than 
12 weeks. After Week 36, assessment will occur every 12 weeks (± 3 weeks) until 
documentation of PD or the start of new anticancer therapy. The same method of radiographic 
assessment used at Screening must be used at all subsequent radiographic evaluations. Copies of 
all imaging scans must be obtained and sent to a central imaging vendor designated by 
ImmunoGen as outlined in the Imaging Manual. The central imaging vendor will assess the 
quality of the images. The imaging vendor will be responsible for the formation and management 
of the blinded independent central review (BICR) which will be used as a sensitivity analysis of 
ORR and DOR by investigator. 
Tumor response will be assessed by the Investigator using RECIST v1.1 (Eisenhauer 2009). 
Response as determined by the Investigator will be recorded in the clinical trial database.  
The central imaging vendor will ensure that the central radiologists remain blinded to the local 
assessment from the Investigator and other unblinding information. This and all other imaging 
procedures will be documented in an independent review charter agreed upon between 
ImmunoGen and the imaging vendor before initiation of any BICR reviews. 
Note: It is very important that the same method of radiologic assessment be used 
throughout the study and that the same lesions are followed.  
7.13.2. 
CA-125 
Serum CA-125 assessments will be performed within 14 days prior to the first dose of study 
drug, and at each radiologic tumor assessment (± 4 days) (Table 2). CA-125 should be assessed 
by the same laboratory throughout the study.  
8. 
ASSESSMENT OF SAFETY 
8.1. 
Recording Adverse Events and Serious Adverse Events 
Adverse Events (AEs), including those attributed to study procedures, will be documented in the 
clinical trial database and monitored continuously throughout the study from the time of 
informed consent until 30 days after the patient’s last study treatment. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
61 
Only AEs/SAEs which are considered related to a study procedure (ie blood draw or fresh tumor 
biopsy) will be captured during the pre-screening period, ie from the time of signing of the pre-
screening informed consent (if one is utilized) until the time of signing of the main study 
informed consent, or until the patient is determined to be a screen failure. All AEs and SAEs, 
regardless of causality, will be captured after the main study ICF has been signed. 
SAEs will continue to be followed by ImmunoGen Pharmacovigilance until resolution, 
stabilization or return to baseline. Beyond this defined reporting period, any unsolicited SAE 
assessed as related to the study drug by the Investigator and reported to ImmunoGen will be 
collected and processed. Additional information obtained after database lock, will reside solely 
in the safety database. 
The Investigator should follow and provide updates for all AEs until clinical recovery is 
complete, laboratory values return to normal, the patient stabilizes, or death occurs, to ensure the 
safety of the patients. This may mean that observations continue beyond the last planned visit per 
protocol and that additional investigations may be requested by the Sponsor. 
8.1.1. 
Definition of Adverse Events 
8.1.1.1. 
Adverse Event 
An AE is any noxious, pathologic, or unintended change in anatomical, physiologic, or 
metabolic function as indicated by physical signs, symptoms, or laboratory changes occurring in 
any phase of a clinical study, whether or not considered study drug-related. This includes an 
exacerbation of a pre-existing condition. AEs include: 
• Worsening (change in nature, severity, or frequency) of conditions present at the 
onset of the study 
• Intercurrent illnesses 
• Drug interactions 
• Events related to or possibly related to concomitant medications 
• Abnormal laboratory values (this includes significant shifts from baseline within the 
range of normal that the Investigator considers to be clinically important) 
• Clinically significant abnormalities in PE, vital signs, and weight 
Note that PD should not be reported as an AE unless it is considered to be drug-related by the 
Investigator. 
All AEs, including AEs attributed to study procedures, occurring from the time of study 
informed consent until 30 days after last study treatment must be reported in the clinical 
database, regardless of the severity or relationship to study drug. Only AEs which are considered 
related to a study procedure (ie blood draw or fresh tumor biopsy) will be captured during the 
pre-screening period, ie from the time of signing the pre-screening consent (if one is utilized) 
until the signing of the main study informed consent, or until the patient is determined to be a 
screen failure. The Investigator should treat patients with AEs appropriately and observe them at 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
62 
suitable intervals until the events stabilize, return to baseline or resolve. AEs may be discovered 
through observation or examination of the patient, questioning of the patient, complaint by the 
patient, or by abnormal clinical laboratory values. 
In addition, AEs may also include laboratory values that become significantly out of range. Such 
abnormal laboratory values or test results constitute AEs if they induce clinical signs or 
symptoms, are considered clinically significant (eg, cause study drug discontinuation or 
constitutes in and of itself an SAE, or require therapy), and should be recorded in the clinical 
database under the signs, symptoms or diagnosis associated with them. In the event of an out-of-
range value, the laboratory test should be repeated until it returns to normal or baseline or can be 
explained and the patient’s safety is not at risk.  
8.1.1.2. 
Serious Adverse Event 
An SAE is any AE occurring at any dose that results in any of the following outcomes: 
• Death 
• Is life-threatening 
• Requires inpatient hospitalization 
• Requires prolongation of existing hospitalization 
• A persistent or significant disability or incapacity or substantial disruption of the 
ability to conduct normal life functions 
• A congenital anomaly or birth defect 
• Important medical events that may not result in death, be life-threatening, or require 
hospitalization may be considered an SAE when, based upon appropriate medical 
judgment, they may jeopardize the patient and may require medical or surgical 
intervention to prevent one of the outcomes listed in this definition. Examples of such 
medical events include allergic bronchospasm requiring intensive treatment in an 
emergency room or at home, blood dyscrasias or convulsions that do not result in 
inpatient hospitalization 
Note that hospitalization is defined as admission to treat a clinical AE. The following events 
would not be considered hospitalizations for SAE reporting purposes: 23-hour hold for 
observation, admission to a hospice facility or nursing home, respite care, outpatient surgery, 
social admission (eg, a homeless patient) or admission not associated with a precipitating clinical 
AE (eg, elective or pre-planned surgery, or in-patient administration of subsequent 
chemotherapy, etc). 
8.1.1.3. 
Adverse Events of Special Interest 
There are no AEs of special interest (serious or nonserious) associated with MIRV.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
63 
8.1.2. 
Classification of Adverse Events 
All AEs will be evaluated according to the NCI CTCAE v5.0 (effective 27 November 2017). If 
the AE is not listed in the CTCAE v5.0, it should be graded based on the description given in 
Table 10. 
Table 10: 
Adverse Event Severity 
Severity 
Definition 
Grade 1 (Mild) 
No limitation of usual activities. 
Grade 2 (Moderate) 
Some limitation of usual activities. 
Grade 3 (Severe) 
Inability to carry out usual activities. 
Grade 4 (Life-threatening) 
Immediate risk of death. 
Grade 5 (Fatal) 
Resulting in death. 
Relationship of an AE or SAE to study medication is to be determined by the Investigator based 
on the definitions in Table 11. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
64 
Table 11: 
Adverse Event Causal Relatedness 
Relationship to Product(s) 
Definition 
Not Related 
No relationship between the event, including laboratory test 
abnormality, and the administration of study drug. There is no temporal 
relationship and there is unambiguous evidence supporting another 
cause.  
Unlikely Related 
A clinical event, including laboratory test abnormality, with a temporal 
relationship to study drug administration which makes a causal 
relationship improbable, and in which other drugs, chemicals or 
underlying disease provide plausible explanations.  
Possibly Related 
A clinical event, including laboratory test abnormality, with a 
reasonable time sequence to administration of study drug, but which 
could also be explained by concurrent disease or other drugs or 
chemicals. Information on study drug withdrawal may be lacking or 
unclear.  
Probably Related 
A clinical event, including laboratory test abnormality, with a 
reasonable time sequence to administration of study drug, unlikely to 
be attributed to concurrent disease or other drugs or chemicals, and 
which follows a clinically reasonable response on withdrawal of study 
drug. The association of the clinical event, including laboratory test 
abnormality, must also have some biologic plausibility, at least on 
theoretical grounds. 
Definitely Related 
A clinical event, including laboratory test abnormality occurring in a 
plausible time relationship to study drug administration, and which 
cannot be explained by concurrent disease or other drugs or chemicals. 
The response to withdrawal of the study drug should be clinically 
plausible. The event must be definitive pharmacologically or 
phenomenologically, using a satisfactory re-challenge procedure if 
necessary.  
8.2. 
Adverse Events 
8.2.1. 
Reporting Serious Adverse Events 
Any SAE, regardless of relationship to study medication, which occurs in a patient from the time 
of study informed consent until 30 days after the last study treatment, must be recorded by the 
clinical site on an SAE report form. Only SAEs which are considered related to a study 
procedure (ie blood draw or fresh tumor biopsy) will be captured during the pre-screening 
period, ie from the time of signing the pre-screening consent (if one is utilized) until the signing 
of the main study informed consent, or until the patient is determined to be a screen failure. The 
SAE must also be recorded in the clinical trial database, including the Investigator’s assessment 
regarding the relationship of the SAE to the study drug. The Investigator will promptly supply all 
information requested by the Sponsor (or contract research organization [CRO]) regarding the 
SAE.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
65 
The Investigator must submit the SAE Report Form to ImmunoGen Pharmacovigilance (or 
designee). This form must be completed and submitted within 24 hours of the Investigator’s 
learning of the event using the contact information printed on the SAE form and contained 
within the SAE form completion instructions. Follow-up information must also be submitted 
using a new SAE Report Form. 
When reporting SAEs, the following additional points should be noted:  
• The underlying diagnosis or syndrome should be reported as the primary SAE term, 
rather than the signs or symptoms (signs and symptoms may be described in the 
narrative). 
• An event term of “Death” should not be reported as an SAE, but rather be recorded as 
an outcome of a specific SAE term. Initially, the event term of “death” can be used 
until the actual cause of death is known. If an autopsy was performed, the autopsy 
report should be provided. 
It is the responsibility of the Sponsor to ensure that each Investigator receives a copy of any 
suspected unexpected serious adverse reaction (SUSAR) report (CIOMS/MedWatch) regarding 
the study drug and that the report is submitted to the appropriate national regulatory agencies.  
The Investigator (or Sponsor or contracted designee) must promptly report all SUSARs to the 
IRB/IEC for review in accordance with national regulations. IRB/IEC notification of the SUSAR 
may take the form of a submission of a copy of the CIOMS/MedWatch report or other format 
accepted by the IRB/IEC. A copy of the CIOMS/MedWatch report and notification to IRB/IEC 
should be retained in the site’s study files.  
In addition to CIOMS/MedWatch reports, the Sponsor will also notify (through annual updates 
to the Investigator Brochure) the Investigators and IRBs/IECs of all deaths that occur during the 
study, irrespective of relationship to study medication. 
8.2.1.1. 
Reporting of Disease Progression 
Disease progression is an anticipated occurrence in oncology drug development and is not an AE 
unto itself.  
Progression of disease should not be reported as an SAE term; any serious medical 
event/condition that results from progression of underlying disease, if untoward, should be 
reported as the SAE.  
Progression of disease with a fatal outcome does not need to be reported as an AE term. The 
applicable protocol CRF page(s) pertaining to death should be appropriately completed however, 
as disease progression. 
8.2.2. 
Reporting a Pregnancy 
Pregnancy and lactation are exclusion criteria. Women of child bearing potential, defined as a 
sexually mature woman who has not undergone surgical sterilization or who has not been 
naturally postmenopausal for at least 12 consecutive months (ie, who has had menses any time in 
the preceding 12 consecutive months) must agree to use highly effective contraceptive methods 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
66 
(as defined in Section 5.8.6) while on study drug and for at least 3 months after the last dose of 
MIRV. In addition, it is recommended that patients undergo monthly pregnancy test for at least 
3 months after the last dose of MIRV. 
The Sponsor must be immediately notified in the event of a pregnancy occurring during the 
study and through 30 days after a patient’s last dose of study drug. If a patient becomes pregnant 
the patient will be withdrawn from study drug. Pregnancy is not an AE unto itself and therefore 
should not be reported as an AE. 
All pregnancies will be recorded on a Pregnancy Report and submitted according to the contact 
information on the form and in the completion guidelines. 
Pregnancies, with the permission of the mother, will be followed to completion or termination 
using the designated sections of the Pregnancy report form. 
Any SAE, occurring during the pregnancy to the mother or fetus, would require that a study SAE 
form also be completed/submitted. 
9. 
STUDY ACTIVITIES 
All study visits and assessments that must be performed during the study and follow-up are 
included in Table 2. 
9.1. 
Screening Visit 
The Investigator is responsible for keeping a record of all patients screened for entry into the 
study, including those who are subsequently excluded. The reason(s) for exclusion must be 
recorded.  
9.1.1. 
Standard of Care Assessments 
In some cases, clinical assessments performed before obtaining informed consent may be used to 
qualify the patient for the study if performed within the screening window. These include 
radiologic tumor assessment, PEs, laboratory results, urinalysis, or other assessments which may 
be considered part of standard of care. In these cases, repeat assessments may not be necessary 
before enrollment, unless individual parameters require further study or confirmation and are 
clinically appropriate.  
Note that safety blood tests, and PE do not need to be repeated if normal and conducted within 4 
days prior to C1D1. 
9.2. 
End of Treatment Visit 
Patients may voluntarily withdraw from the study drug at any time for any reason, and without 
prejudice to further treatment. In addition, patients may be withdrawn by the Investigator if they 
do not feel the patient is deriving clinical benefit or because the patient is experiencing 
unacceptable toxicity. The reasons for which a patient may be prematurely discontinued are 
listed in Section 5.6. The clinical trial database will capture reasons for withdrawal. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
67 
Patients who withdraw or are removed from the study treatment will have an EOT visit within 7 
days of the decision to discontinue study drug. Patients will undergo assessments as outlined in 
Table 2.  
9.3. 
Follow-up Assessments 
9.3.1. 
30-Day Follow-up Visit 
A 30-Day Follow-up visit will occur 30 days (+14 days) after last dose of MIRV and should 
occur prior to the start of new anticancer therapy.  
In some cases, nonserious AE observations may continue beyond the safety visit. All ocular AEs 
will be followed until resolution, stabilization, or return to baseline. In these instances, additional 
information may be requested by ImmunoGen to adequately categorize the nature of the toxicity. 
All SAEs will be followed until they resolve, stabilize or return to baseline, regardless of time 
from last dose or last visit. 
9.3.2. 
Response Follow-up 
Patients who discontinued MIRV for reasons other than PD will continue with tumor 
assessments until documentation of PD or the start of a new anticancer therapy, whichever 
comes first. Prior to Week 36 (from Cycle 1, Day 1), assessments should occur every 6 weeks 
(± 1 week) as allowed by local requirements but must occur at an interval of no more than 
12 weeks. After Week 36, assessment will occur every 12 weeks (± 3 weeks) until 
documentation of disease progression or the start of new anticancer therapy. 
9.3.3. 
Survival Follow-up 
All patients who discontinue MIRV for any reason will be followed for survival after disease 
progression as per Investigator, or after start of a new anticancer therapy. Survival status will be 
assessed every 3 months (± 1 month) until death, lost to follow-up, withdrawal of consent for 
survival follow-up or until EOS, whichever comes first. Additional survival follow-up calls may 
occur periodically if needed. 
10. 
STATISTICAL METHODS 
This is a Phase 3 study designed to evaluate the ORR of MIRV in patients with high FRα 
expressing, high-grade PROC. 
All patients who have received at least 1 dose of MIRV will comprise the Safety Analysis 
Population.  
The Efficacy Evaluable Population will include all patients who have received at least 1 dose of 
MIRV and have measurable lesions at baseline (per RECIST v1.1). The primary efficacy 
analysis of ORR and all other efficacy analyses will be based on the Efficacy Evaluable 
Population. 
The safety analysis will be based on Safety Analysis Population. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
68 
All statistical analyses will be performed using SAS statistical software Version 9.4 or later, 
unless otherwise noted. For categorical variables, the number (n) and percent of each category 
within a parameter will be presented. For continuous variables, the sample size (n), mean, 
median, and standard deviation, as well as the minimum and maximum values, will be presented. 
Missing data will not be imputed unless otherwise stated. There will be a detailed description of 
patient disposition, patient demographics, and baseline characteristics. 
A SAP will fully describe the planned analyses for this trial and will be finalized prior to 
database lock.  
10.1. 
Sample Size 
Primary endpoint is confirmed ORR per Investigator assessment. 
A sample size of 105 efficacy evaluable patients achieves 91% power to detect a difference in 
ORR of 12% (24% vs. 12%) using a 1-sided binomial test. The target significance level (1-sided 
α level) is 0.025. The actual significance level achieved by this test is 0.0242. These results 
assume that the ORR is 12% under the null hypothesis and 24-% under the alternative 
hypothesis. 
Patients who have received at least 1 dose of MIRV but are not efficacy evaluable will be 
included in Safety Analysis Population. However, these patients will not be included in the 
Efficacy Evaluable Population and will be replaced for the purpose of sample size determination. 
A total of approximately 110 patients will be enrolled to achieve 105 efficacy evaluable patients. 
10.2. 
Pharmacokinetic Analyses 
PK parameters will not be calculated due to the sparse sampling scheme in this study. Summary 
statistics of the concentration at each time point (nominal time) will be presented. Graphical 
presentation of the data may also be completed using nominal time.  
10.3. 
Safety Analyses 
Safety analyses will be based on the Safety Analysis Population. 
AEs and concomitant medication will be listed.  
AEs will be coded using the latest Medical Dictionary for Regulatory Activities (MedDRA) 
version and summarized per system organ class (SOC) and preferred term (PT). 
Concomitant medications will be coded using the World Health Organization-Drug Dictionary 
(WHO-DD; 01 September 2019 or later version). A dictionary listing of all unique concomitant 
medications used in the study will be provided. 
All hematology, blood chemistry, and vital signs will be listed per patient for each assessment 
and descriptive statistics will be tabulated for select criteria. Changes from baseline in 
hematology, blood chemistry, and vital signs will be summarized by treatment. Shifts in 
hematology and blood chemistry from Baseline values will be summarized. Plasma also will be 
evaluated for the presence of ADA.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
69 
10.4. 
Efficacy 
Unless stated otherwise in the SAP, efficacy analyses will be performed on the Efficacy 
Evaluable Population. 
10.4.1. 
Primary Efficacy Analysis 
10.4.1.1. Objective Response Rate 
The primary endpoint is ORR, which includes best response of CR or PR. 
The primary endpoint of ORR (objective response = CR + PR) will be estimated along with a 
95% CI by the Clopper-Pearson method based on the efficacy evaluable population.  
The primary analysis of ORR will be conducted after all efficacy evaluable patients have:  
• undergone at least 4 post-baseline tumor assessments, or 
• experienced radiological disease progression, or  
• died or had clinical progression within 105 days of first dose of study drug, or 
• withdrawn from study for other reasons 
10.4.2. 
Key Secondary Efficacy Endpoint 
The key secondary endpoint of Investigator-assessed DOR will be estimated using Kaplan-Meier 
method for survival function estimate.  
The initial analysis of DOR will be conducted at the time of primary analysis of ORR. An 
updated analysis of DOR will be conducted 12 months after the primary analysis of ORR, at the 
end of the study. 
10.4.3. 
Additional Secondary Efficacy Endpoints 
The additional secondary endpoints of Investigator-assessed PFS and OS will be estimated using 
Kaplan-Meier method for survival function estimate.  
10.5. 
Interim Analysis 
There are no planned interim analyses for this study. Efficacy data generated in the MIRV 
program in patients with FRα high expression (by the PS2+ scoring method), includes a 44% 
Investigator-assessed ORR in the 27 patients in IMGN853-0401 and a 38% Investigator-assessed 
ORR in the 116 patients in IMGN853-0403 (Moore 2019). In addition, an analysis of patients 
derived from both Study 0401 and Study 0403 who are eligible for this study (n=70), revealed an 
ORR by investigator of 31.4% with a DOR of 7.8 months. Thus, an interim analysis for futility 
in the current study in the same or a very similar population is not warranted. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
70 
11. 
QUALITY CONTROL AND ASSURANCE 
11.1. 
Recording of Data and Data Quality Assurance 
Data will be documented in various source documents (eg, the patient medical chart) and then 
manually entered into the clinical trial database. Clinical sites will be monitored by ImmunoGen 
or its designee to ensure the accuracy of data against source documents. If necessary, the study 
site will be contacted for corrections or clarifications. 
Adverse events will be coded using the latest MedDRA version. Concomitant medications will 
be coded using the (WHO-DD; 01 September 2019 or later version. Training will occur at an 
Investigator meeting or at the site initiation visit or both. Remote web-based training may be 
provided. Instruction manuals (eg, laboratory manuals and pharmacy manuals) will be provided 
to aid consistency in data collection and reporting across sites. 
This clinical study will be conducted according to ICH-GCP E6 (R2) guidelines. Quality 
oversight shall be maintained through proactive and continual risk assessment and mitigation at 
the operational level. GCP quality assurance audits will be conducted as needed as continued 
compliance oversight.  
12. 
ETHICAL CONSIDERATIONS AND ADMINISTRATIVE 
PROCEDURES 
12.1. 
Ethical and Regulatory 
This clinical study will be conducted by the Sponsor, the Investigator, delegated Investigator 
staff and sub-Investigator(s), in accordance with the protocol, the Declaration of Helsinki, the 
International Conference on Harmonisation (ICH) Harmonised Tripartite Guideline for GCP, and 
all applicable local regulatory requirements. 
This clinical study will be recorded in a free, publicly accessible, internet-based registry, no later 
than 21 days after the first patient enrollment, in compliance with applicable regulatory 
requirements and with ImmunoGen public disclosure commitments. 
12.1.1. 
Institutional Review Board or Independent Ethics Committee Approval 
Before initiation of the study, the Investigator must provide the Sponsor with a copy of the 
written IRB/IEC approval of the protocol, the main study ICF and the pre-screening ICF (latter 
ICF is applicable for sites requesting permission to pre-screen for FRα positivity (high FRα) 
before performing any additional study related tests). This approval must refer to the ICF(s) and 
to the study title, study number, and version and date of issue of the study protocol, as given by 
the Sponsor on the cover page of the protocol. 
Status reports must be submitted to the IRB/IEC at least once per year or as per institutional 
guidelines. The IRB/IEC must be notified of completion of the study and a final report must be 
provided to the IRB/IEC. A copy of these reports will be sent to the study clinical monitor or 
designee. The Investigators must maintain an accurate and complete record of all submissions 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
71 
made to the IRB/IEC, including a list of all reports and documents submitted. AEs, which are 
subject to expedited reporting to the FDA or other regulatory agencies (SUSARs), must be 
submitted promptly to the IRB/IEC. 
12.1.2. 
Patient Information and Consent 
An ICF that includes information about the study will be prepared and given to the patient, or the 
patient’s legally authorized representative(s). The ICF will contain all FDA and ICH required 
elements and be approved by an IRB/IEC. The ICF must be in a language understandable to the 
patient or the patient’s legally authorized representative(s). Before enrolling in the clinical study, 
the nature, scope, and possible consequences of the clinical study will be explained to the patient 
or the patient’s legally authorized representative(s) in a form understandable to him or her. After 
the patient has been given ample time to read and ask questions regarding the ICF and has been 
informed that participation is voluntary, the patient or the patient’s legally authorized 
representative(s) must give consent in writing. If the patient or the patient’s legally authorized 
representative(s) is unable to read, oral presentation and explanation of the written ICF and 
information to be supplied must take place in the presence of an impartial witness. Consent must 
be confirmed orally and by the personally dated signature of the patient or by the patient’s 
legally authorized representative(s). The witness and the person conducting the informed consent 
discussions must also sign and personally date the informed consent document. The informed 
consent process must be recorded and dated in the patient’s source document. 
A copy of the signed and dated consent document(s) must be given to the patient or the patient’s 
legally authorized representative(s). The original signed and dated consent document will be 
retained by the Investigator. Patient confidentiality will be maintained as outlined in 
Section 12.3. 
The Investigator must not undertake any measures specifically required solely for the clinical 
study until valid informed consent has been obtained. 
A model of the pre-screening and the main study ICF will be provided to the sites separately for 
this protocol. The main study consent can be used to confirm a patient’s consent to all study 
procedures and all study-specific screening tests. The pre-screening ICF can be used to pre-
screen patients for FRα status before performing any additional study related tests. If a patient is 
eligible based on FRα expression level, the patient will be provided the main study consent and 
only after signing the main study ICF will additional study-specific screening tests be performed. 
Alternatively, the patient can be consented on both pre-screening and main study ICF at the same 
time; and FRα testing and study-specific screening assessments can be carried out in parallel.  
Patients must be consented to the most current version of the ICF during their participation in the 
study.  
12.2. 
Investigators and Study Administrative Structure 
Before initiation of the study, the Investigators must provide the Sponsor with a completed Form 
FDA 1572 or equivalent form. Study medications must be administered only under the 
supervision of the Investigators listed on this form. Curriculum vitae must be provided for the 
Investigators and sub-investigators listed on Form FDA 1572 or equivalent form. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
72 
The Investigator must ensure that all persons assisting with the study are adequately informed 
about the protocol, any amendments to the protocol, the study treatments, and their study related 
duties and functions. The Investigator must maintain a list of sub-investigators and other 
appropriately qualified persons to whom he or she has delegated significant study related duties. 
12.3. 
Patient Confidentiality 
Patient names will not be supplied to the Sponsor. If the patient name appears on any documents, 
it must be redacted before a copy of the document is supplied to the Sponsor. Study findings 
stored on a computer will be stored in accordance with local data protection laws. Patient blood 
and tissue samples, and radiographic images sent to outside laboratories and/or CROs are 
identified by study patient number only to ensure maintenance of confidentiality. The patient 
consent form will state publications resulting from this study will not refer to patient name or 
include any other information that might disclose the identity of the patient. The patients will be 
told that representatives of the Sponsor, a designated CRO, the IRB/IEC, or regulatory 
authorities may inspect their medical records to verify the information collected, and that all 
personal information made available for inspection will be handled in strictest confidence and in 
accordance with local data protection laws. The Investigator will maintain a personal patient 
identification list (patient numbers with the corresponding patient names) to enable records to be 
identified. 
12.4. 
Study Monitoring 
Sponsor or its designee will monitor the conduct of the trial on a regular basis throughout the 
duration of the study, according to the monitoring plan and in compliance with ICH-GCP E6 
(R2). Monitoring of the study will serve to ensure: (a) The rights and well-being of human 
subjects are protected; (b) The reported trial data are accurate, complete, and verifiable from 
source documentation; and (c) The conduct of the trial is in compliance with the currently 
approved protocol/amendment(s), with GCP, and with applicable regulatory requirement(s). 
The study monitor will train site personnel on the conduct of the trial. The monitor will assess 
the trial site’s compliance with the protocol and will periodically review and verify a sample of 
the patient data recorded on CRFs against source documentation. The study monitor will also 
review documents that provide evidence of the proper consent and eligibility of enrolled patients, 
the compliant conduct of study procedures, the administration and disposition of investigational 
product(s), the reporting of serious adverse events and adverse reactions, and the continued 
maintenance of trial records. 
The Investigator will allocate adequate time to support such monitoring activities. The 
Investigator will also ensure that the monitor is given reasonable remote and/or on-site access to 
study-related documents, source documents (regardless of media) and study-related facilities (eg, 
investigational pharmacy, etc). Queries may be raised if any datum is unclear or contradictory. 
The Investigator and site personnel must address all queries in a timely manner. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
73 
12.5. 
Study Committees 
12.5.1. 
Steering Committee 
A Steering Committee (SC) will be comprised of lead Investigators from North America and 
Europe. The purpose of the SC is to provide overall guidance regarding design of the study, 
conduct and execution of the trial. This includes (but is not limited to) safety, efficacy, 
enrollment and contribution to scientific input for publications. Responsibilities of the SC and 
communication flow between ImmunoGen and the SC will be included in the SC charter 
document.  
12.5.2. 
Independent Data Monitoring Committee 
An IDMC will not be utilized in this study. Sponsor will monitor safety in accordance with ICH-
GCP E6 (R2) guidelines. 
12.6. 
Case Report Forms and Study Reports 
Electronic case report forms (eCRFs) are provided for each patient. All forms must be filled out 
by authorized study personnel. The Investigator is required to sign/e-sign the eCRF after all data 
have been captured for each patient. If corrections are made after review and signature by the 
Investigator, he or she must be made aware of the changes, and his or her awareness documented 
by re-signing the eCRF Critical Documents 
Before ImmunoGen initiates the study at a given site, it is the responsibility of the Investigator to 
ensure that the following documents are made available to ImmunoGen or their designee: 
• Curricula vitae of Investigator and sub-Investigator(s) (current, dated and signed or 
supported by an official regulatory document) 
• Signed and dated agreement of the final protocol 
• Signed and dated agreement of any amendment(s), if applicable 
• Approval/favorable opinion from the IRB/IEC clearly identifying the document and 
document revision reviewed, including but not limited to, the protocol, any protocol 
amendments, Investigator Brochure, Patient Information/ICF, and any other written 
information to be provided regarding patient recruitment procedures 
• Copy of IRB/IEC approved Patient Information/ICF/any other written 
information/advertisement 
• List of IRB/IEC Committee members/constitution or equivalent compliance statement 
• Study and Financial agreement(s) 
• Completed Form FDA 1572 or equivalent form 
• Completed Financial Disclosure Form 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
74 
Additional documents such as laboratory reference ranges and certifications will be collected 
during the study. Ongoing regulatory approvals and notifications, as required, must also be made 
available to ImmunoGen. 
12.7. 
Protocol Adherence 
Each Investigator must adhere to the protocol as detailed in this document and agree that any 
changes to the protocol must be approved by ImmunoGen’s authorized representative in writing 
before seeking approval, where necessary, from the IRB/IEC, Research Ethics Committee 
(REC), or Ethics Review Board (ERB). Each Investigator will be responsible for allowing only 
those patients who have met protocol eligibility criteria to be enrolled. 
Modifications to the protocol should not be made without agreement of the Investigators and 
ImmunoGen. Changes to the protocol will require written IRB/IEC, REC, or ERB 
approval/favorable opinion before implementation, except when the modification is needed to 
eliminate an immediate hazard(s) to patients. The IRB/IEC/REC/ERB may provide expedited 
review and approval/favorable opinion for minor change(s) in ongoing studies that have the 
approval/favorable opinion of the IRB/IEC/REC/ERB. ImmunoGen will submit all protocol 
modifications to the appropriate regulatory authorities in accordance with the governing 
regulations. 
When immediate deviation from the protocol is required to eliminate an immediate hazard(s) to 
patients, the Investigator will contact ImmunoGen, if circumstances permit, to discuss the 
planned course of action. Any departures from the protocol must be fully documented in the 
source documentation. 
Prospective waivers or exemptions are not permitted.  
12.8. 
End of Study 
EOS will occur 12 months after the primary analysis for ORR. If patients are still receiving 
clinical benefit from MIRV at EOS, either the study will be amended to allow those patients to 
continue to receive study treatment with limited data collection (eg SAEs, dosing information) 
until they are no longer benefiting or patients will be given the option to roll-over to a long-term 
extension study.  
12.9. 
Study Termination 
If the Sponsor, an Investigator, or Clinical Study Monitor discovers conditions arising during the 
study that indicate that the clinical investigation should be halted due to an unacceptable patient 
risk, the study must be terminated after appropriate consultation between ImmunoGen and the 
Investigators. In addition, a decision on the part of ImmunoGen to suspend or discontinue 
development of the study drug may be made at any time.  
Within 15 days of premature closure, ImmunoGen must notify the competent authorities and 
IECs/IRBs of any member state where the study is being conducted, providing the reasons for 
study closure. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
75 
12.10. 
Site Termination 
If ImmunoGen, an Investigator, or regulatory authorities discover conditions during the study 
that indicate that the study or related activities at a particular center should be terminated, this 
action may be taken after appropriate consultation between ImmunoGen and the Investigator. 
Conditions that may warrant study or center termination include but are not limited to: 
• Discovery of an unexpected, serious, and/or unacceptable risk to patients enrolled in 
the study 
• Decision on the part of ImmunoGen to suspend or discontinue testing, evaluation, or 
development of the clinical program 
• Unacceptable benefit-risk relationship of the investigational product 
• Recommendations of a regulatory body 
• Investigator failure to comply with applicable regulatory authority requirements or 
protocol requirements 
• Submission of knowingly false information from the center to ImmunoGen or 
regulatory authorities 
Study or center termination and follow-up will be performed in compliance with the conditions 
set forth in 21 CFR § 312 and in compliance with the principles set forth in International 
Conference on Harmonisation (ICH) Good Clinical Practices (GCP). 
12.11. 
Access to Source Documentation 
According to the ICH-GCP, the monitoring team must check the clinical trial database entries 
against the source documents. The ICF will include a statement by which the patient allows the 
Sponsor’s duly authorized personnel, the IRB/IEC, and the regulatory authorities to have direct 
access to original medical records which support the data in the clinical trial database (eg, 
patient's medical file, appointment books, original laboratory records, etc). These personnel, 
bound by professional secrecy, must maintain the confidentiality of all personal identity or 
personal medical information (according to confidentiality and personal data protection rules). 
12.12. 
Audits and Inspections 
Regulatory authorities, the IEC/IRB, or the Sponsor may request access to all source documents, 
CRFs, and other study documentation for on-site audit or inspection. Direct access to these 
documents must be guaranteed by the Investigator, who must provide support at all times for 
these activities. Monitoring and auditing procedures that comply with local regulations and 
current GCP guidelines will be followed. On-site review of the clinical trial database for 
completeness and clarity, crosschecking with source documents, and clarification of 
administrative matters will be performed. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
76 
12.13. 
Data Generation and Analysis 
The clinical trial database will be developed and maintained by a CRO or other vendors as 
designated by ImmunoGen. ImmunoGen or its designee will be responsible for performing study 
data management activities and analyses. 
12.14. 
Retention of Data 
Essential documents will be retained until the following requirements are met: 
• a minimum of two years (or longer, if required by local/regional regulation) has 
elapsed after an approval of a marketing application which was supported by this 
study, or 
• there are no pending or contemplated marketing applications, or 
• at least two years have elapsed since the formal discontinuation of clinical 
development of the investigational product, or  
• the record retention policies and guidelines for countries in which the study is being 
conducted are followed (whichever is longer) 
It is the responsibility of the Sponsor to inform the Investigator or institution as to when these 
documents no longer need to be retained. 
12.15. 
Financial Disclosure 
The Investigator must disclose any financial interests in the Sponsor as described in 21 CFR Part 
54 before beginning this study and for 12 months after the study has been completed. The 
appropriate form will be provided to the Investigator by the Sponsor, which will be signed and 
dated by the Investigator, before the start of the study. If financial interests change at any time 
during the study, an updated financial disclosure form is required. 
All financial details relating to the Investigators’ participation in this study are provided in the 
separate contract between the institution and ImmunoGen. 
12.16. 
Insurance Compensation 
The Sponsor certifies that it has taken out a liability insurance policy covering all clinical trials 
under its sponsorship. This insurance policy is in accordance with local laws and requirements. 
The insurance of the Sponsor does not relieve the Investigator and the collaborators from any 
obligation to maintain their own liability insurance policy. An insurance certificate will be 
provided to the IECs/IRBs or regulatory authorities in countries requiring this document. 
12.17. 
Publication and Disclosure Policy 
The information obtained during the conduct of this clinical study is confidential, and disclosure 
to third parties other than those noted below is prohibited. All information concerning the 
product as well as any matter concerning the operation of the Sponsor, such as clinical 
indications for the drug, its formula, methods of manufacture and other scientific data relating to 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
Confidential and Proprietary 
ImmunoGen, Inc. 
77 
it, that have been provided by the Sponsor and are unpublished, are confidential and must remain 
the sole property of the Sponsor. The Investigator will agree to use the information only for the 
purposes of carrying out this study and for no other purpose unless prior written permission from 
the Sponsor is obtained. 
Information obtained during the conduct of this study will be used by ImmunoGen in connection 
with the development of the study drug. The study Investigator is obliged to provide 
ImmunoGen with complete test results and all data developed in this study. The Sponsor has full 
ownership of the original case report forms completed as part of the study. This information may 
be disclosed to other physicians who are conducting similar studies and to the global health 
authorities as deemed necessary by the Sponsor. Patient-specific information may be provided to 
other appropriate medical personnel related to the care of that patient only with patient's prior 
consent.  
The Investigator and any other clinical personnel associated with this study will not publish the 
results of the study, in whole or in part, at any time, unless they have consulted with 
ImmunoGen, provided ImmunoGen a copy of the draft document intended for publication, and 
obtained ImmunoGen’s written consent for such publication. All information obtained during the 
conduct of this study will be regarded as confidential. ImmunoGen will use the information for 
registration purposes and for the general development of the drug. 
13.
LIST OF REFERENCES
Ab O, Whiteman KR, Bartle LM, et al. IMGN853, a folate receptor-α (FRα)-targeting antibody-
drug conjugate, exhibits potent targeted antitumor activity against FRα-expressing tumors. Mol 
Cancer Ther. 2015;14(7):1605-13. 
Aghajanian C, Blank SV, Goff BA, et al. OCEANS: a randomized, double-blind, placebo-
controlled phase III trial of chemotherapy with or without bevacizumab in patients with 
platinum-sensitive recurrent epithelial ovarian, primary peritoneal, or fallopian tube cancer. 
J Clin Oncol. 2012;30(17):2039-45. 
Allard JE, Risinger JI, Morrison C, et al. Overexpression of folate binding protein is associated 
with shortened progression-free survival in uterine adenocarcinomas. Gynecol Oncol. 
2007;107(1):52-7. 
Armstrong DK, Alvarez RD, Bakkum-Gamez JN, et al. NCCN guidelines insights: Ovarian 
Cancer, Version 1.2019. J Natl Compr Canc Netw. 2019;17(8):896-909. 
Baldwin LA, Huang RW, Miller T, et al. Ten-year relative survival for epithelial ovarian cancer. 
Obstet Gynecol. 2012;120(3)612-8. 
Basal E, Eghbali-Fatourechi GZ, Kalli KR, et al. Functional folate receptor alpha is elevated in 
the blood of ovarian cancer patients. PLoS One. 2009;4(7):e6292. 
Cannistra SA. Cancer of the ovary. N Engl J Med. 2004;351(24):2519-29. 
Cannistra SA. Evaluating new regimens in recurrent ovarian cancer: how much evidence is good 
enough? J Clin Oncol. 2010;28(19):3101-3. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
78 
Chen YL, Chang MC, Huang CY, et al. Serous ovarian carcinoma patients with high alpha-folate 
receptor had reducing survival and cytotoxic chemo-response. Mol Oncol. 2012;6(3):360-9.  
Cobb LP, Gaillard S, Wang Y, et al. Adenocarcinoma of mullerian origin: review of 
pathogenesis, molecular biology, and emerging treatment paradigms. Gynecol Oncol Res Pract. 
2015;2:1-16. 
Crane LMA, Arts JG, van Oosten M, et al. The effect of chemotherapy on expression of folate 
receptor-alpha in ovarian cancer. Cellular Oncol (Dordr). 2012;35(1):9-18. 
Dainty LA, Risinger JI, Morrison C, et al. Overexpression of folate binding protein and 
mesothelin are associated with uterine serous carcinoma. Gynecol Oncol. 2007;105(3):563-70. 
Eisenhauer E, Therasse P, Bogaerts J, et al. New response criteria in solid tumors: revised 
RECIST guideline (version 1.1). Eur J Cancer. 2009;45(2):228-47. 
Elnakat H, Ratnam M. Distribution, functionality and gene regulation of folate receptor 
isoforms: implications for targeted therapy. Adv Drug Deliv Rev. 2004;56(8):1067-84. 
Erickson HK, Park PU, Widdison WC, et al. Antibody-maytansinoid conjugates are activated in 
targeted cancer cells by lysosomal degradation and linker-dependent intracellular processing. 
Cancer Res. 2006;66(8):4426-33. 
EUCAN. Cancer Fact Sheet: Ovary. https://gco.iarc.fr/today/data/factsheets/cancers/25-Ovary-
fact-sheet.pdf. Effective March 2019. Accessed August 2019. 
Fisher RE, Siegel BA, Edell SL, et al., Exploratory study of 99mTc-EC20 imaging for 
identifying patients with folate receptor-positive solid tumors. J Nucl Med. 2008;49(6):899-906. 
Gaillard S, Ghamande SA, Pardo B, et al. Phase III trial of Lurbinectedin versus PLD or 
Topotecan in platinum-resistant ovarian cancer patients: Results of CORAIL trial. Ann Oncol. 
2018;29(suppl_8):viii332-viii358. 
Garcia A, Singh H. Bevacizumab and ovarian cancer. Ther Adv Med Oncol. 2013;5(2):133-41. 
Garin-Chesa P, Campbell I, Saigo PE, Lewis JL Jr, Old LJ, Rettig WJ. Trophoblast and ovarian 
cancer antigen LK26. Sensitivity and specificity in immunopathology and molecular 
identification as a folate-binding protein. Am J Pathol. 1993;142(2):557-67. 
Gonzalez-Martin A, Pthuri B, Vergote I, et al. Niraparib in patients with newly diagnosed 
advanced ovarian cancer [published online September 28, 2019]. N Engl J Med. 
doi:10.1056/NEJMoa1910962. 
Grant DJ, Moorman PG, Akushevich L, et al. Primary peritoneal and ovarian cancers: an 
epidemiological comparative analysis. Cancer Causes Control. 2010;21(7):991-998.  
Hanker LC, Loibl S, Burchardi N, et al. The impact of second and sixth line of therapy on 
survival of relapsed ovarian cancer after primary taxane/platinum-based therapy. Ann Oncol. 
2012;23(10):2605-12. 
Hoskins P, Eisenhauer E, Beare S, et al. Randomized phase II study of two schedules of 
topotecan in previously treated patients with ovarian cancer: a National Cancer Institute of 
Canada Clinical Trials Group study. J Clin Oncol. 1998;16(6):2233-7. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
79 
Hough CD, Cho KR, Zonderman AB, Schwartz DR, Morin PJ. Coordinately up-regulated genes 
in ovarian cancer. Cancer Res. 2001;61(10):3869-76. 
Jones MB, Neuper C, Clayton A, et al. Rationale for folate receptor alpha targeted therapy in 
“high risk” endometrial carcinomas. Int J Cancer. 2008;123(7):1699-703. 
Kalli KR, Oberg AL, Keeney GL, et al. Folate receptor alpha as a tumor target in epithelial 
ovarian cancer. Gynecol Oncol. 2008;108(3):619-26. 
Kelemen LE. The role of folate receptor alpha in cancer development, progression and treatment: 
cause, consequence or innocent bystander? Int J Cancer. 2006;119(2):243-50. 
Mantovani LT, Miotti S, Menard S, et al. Folate binding protein distribution in normal tissues 
and biological fluids from ovarian carcinoma patients as detected by the monoclonal antibodies 
MOv18 and MOv19. Eur J Cancer. 1994;30A(3):363-9. 
Matsuo K, Yvonee GL, Lynda DR, Sood AK. Overcoming platinum resistance in ovarian 
carcinoma. Expert Opin Investig Drugs. 2010;19(11):1339-54.  
Mirza MR, Monk BJ, Herrstedt J, et al. Niraparib maintenance therapy in platinum-sensitive, 
recurrent ovarian cancer. N Engl J Med. 2016;375:2154-64. DOI: 10.1056/NEJMoa1611310. 
Moore K, Colombo N, Scambia G, et al. Maintenance olaparib in patients with newly diagnosed 
advanced ovarian cancer. N Engl J Med. 2018;379(26):2495-505. 
Moore K, Oza A, Colombo N, et al. FORWARD I (GOG 3011): A phase III study of 
mirvetuximab soravtansine, a folate receptor alpha (FRa)-targeting antibody-drug conjugate 
(ADC), versus chemotherapy in patients (pts) with platinum-resistant ovarian cancer (PROC). 
Ann Oncol. 2019;30(Suppl 5):v403–v434. 
Moore KN, Secord, AA, Geller MA, et al. Niraparib monotherapy for late-line treatment of 
ovarian cancer (QUADRA): a multicentre, open-label, single-arm, phase 2 trial. Lancet Oncol. 
2019;20(5):636-48. 
Naumann WR, Coleman RL. Management strategies for recurrent platinum-resistant ovarian 
cancer. Drugs. 2011;71(11):1397-1412.  
National Cancer Institute. Surveillance, Epidemiology, and End Results Program (SEER). 
Cancer Stat Facts: Ovarian. https://seer.cancer.gov/statfacts/html/ovary.html. Accessed 2019. 
NCCN Clinical Practice Guidelines in Oncology. Epithelial Ovarian Cancer/Fallopian Tube 
Cancer/Primary Peritoneal Cancer & Less Common Histopathologies. Version 2.2019. 
https://www.nccn.org/professionals/physician_gls/pdf/ovarian.pdf. Published September 17, 
2019. Accessed October 2019. 
O’Shannessy DJ, Jackson SM, Twine NC, et al. Gene expression analyses support fallopian tube 
epithelium as the cell of origin of epithelial ovarian cancer. Int J Mol Sci. 2013;14(7):13687-
13703. 
Pujade-Lauraine E, Hilpert F, Weber B, et al. Bevacizumab combined with chemotherapy for 
platinum-resistant recurrent ovarian cancer: the AURELIA open-label randomized phase III trial. 
J Clin Oncol. 2014;32(13):1302-8. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
80 
Pujade-Lauraine E, Fujiwara K, Ledermann JA, et al. Avelumab alone or in combination with 
pegylated liposomal doxorubicin versus pegylated liposomal doxorubicin alone in platinum-
resistant or refractory epithelial ovarian cancer: Primary and biomarker analysis of the phase III 
JAVELIN Ovarian 200 trial. Late breaking abstract presented at: 50th Annual Meeting of the 
Society of Gynecologic Oncology; March 16-19, 2019; Honolulu, HI. 
Rustin GJ, Quinn M, Thigpen T, et al. Re: New guidelines to evaluate the response to treatment 
in solid tumors (ovarian cancer). J Natl Cancer Inst. 2004;96(6):487-8. 
Scorer P, Lawson N, Quinn A. Scorer P, Lawson N, Quinn A. A Full Immunohistochemical 
Evaluation of a Novel Monoclonal Antibody to Folate Receptor – alpha (FR-a). Novocastra 
Journal of Histopathology, reAGENTS. 2010;3:8-12.  
van Dam GM, Themelis G, Crane LM, et al. Intraoperative tumor-specific fluorescence imaging 
in ovarian cancer by folate receptor-α targeting: first in-human results. Nat Med. 
2011;17(10):1315-9. 
Wadler S, Benson A, Engelking C, et al. Recommended guidelines for the treatment of 
chemotherapy-induced diarrhea. J Clin Oncol. 1998;16(9):3169-78. 
Weitman SD, Lark RH, Coney LR et al. Distribution of the folate receptor GP38 in normal and 
malignant cell lines and tissues. Cancer Res. 1992;52(12):3396-401.  
Younes A, Kim S, Romaguera J, et al. Phase I multidose-escalation study of the anti-CD19 
maytansinoid immunoconjugate SAR3419 administered by intravenous infusion every 3 weeks 
to patients with relapsed/refractory B-cell lymphoma. J Clin Oncol. 2012;30(22):2776-82. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
81 
APPENDIX A. EASTERN COOPERATIVE ONCOLOGY GROUP 
(ECOG) PERFORMANCE STATUS SCALE 
GRADE 
SCALE  
0 
Fully active, able to carry out all pre-disease performance without restriction. 
(Karnofsky 90-100) 
1 
Restricted in physically strenuous activity but ambulatory and able to carry out work 
of a light or sedentary nature, eg, light housework, office work. (Karnofsky 70-80) 
2 
Ambulatory and capable of all self-care but unable to carry out work activities. Up 
and about more than 50% of waking hours. (Karnofsky 50-60) 
3 
Capable of only limited self-care, confined to bed or chair more than 50% of 
waking hours. (Karnofsky 30-40) 
4 
Completely disabled. Cannot carry on any self-care. Totally confined to bed or chair. 
(Karnofsky 10-20) 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
82 
APPENDIX B. RESPONSE DEFINITIONS (RECIST 1.1) 
(Eisenhauer 2009) 
DEFINITIONS 
Baseline: Baseline is defined as the most recent assessment performed before the first dose of 
study treatment. Baseline assessments must be performed within the period defined in the 
protocol eligibility criteria. 
Measurable Lesions: Except for lymph nodes (described below), measurable lesions are defined 
as those that can be accurately measured in at least one dimension (longest diameter to be 
recorded) as ≥ 10 mm with CT scan (if CT scans have slice thickness greater than 5 mm, the 
minimum size of a measurable lesion is twice the slice thickness).  
• To be considered pathologically enlarged and measurable, a lymph node must be 
≥ 15 mm in short axis when assessed by CT scan (CT scan slice thickness 
recommended to be no greater than 5 mm). At baseline and in follow-up, only the 
short axis will be measured and recorded. 
• MRI may be substituted for contrast-enhanced CT for lesions at some anatomical 
sites, but not for lesions in the lungs. The minimum size for measurability is the same 
as for CT (10 mm) as long as the scans are performed with slice thickness of 5 mm 
and no gap. If MRI is performed with thicker slices, the size of a measurable lesion at 
baseline should be twice the slice thickness. In the event there are inter-slice gaps, 
this also needs to be considered in determining the size of measurable lesions at 
baseline. 
Non-measurable Lesion: all other lesions (or sites of disease) including small lesions (longest 
diameter <10 mm or pathological lymph nodes with ≥ 10 to < 15 mm short axis), are considered 
non-measurable.  
• Lymph nodes that have a short axis < 10mm are considered non-pathological and are 
not to be recorded or followed.  
• Bone lesions, leptomeningeal disease, ascites, pleural/pericardial effusions, 
lymphangitis cutis/pneumonitis, inflammatory breast disease, and abdominal masses 
(not followed by CT or MRI), are considered as non-measurable. 
Target Lesions: All measurable lesions up to a maximum of two lesions per organ and five 
lesions in total, representative of all involved organs, are to be identified as target lesions and 
measured and recorded at baseline.  
• Target lesions are to be selected on the basis of their size (lesions with the longest 
diameter) to represent all involved organs, and to be those that lend themselves to 
reproducible repeated measurements.  
• It may be the case that on occasion, the largest lesion does not lend itself to 
reproducible measurement in which circumstance the next largest lesion which can be 
measured reproducibly should be selected. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
83 
• Target lesions will be measured at each assessment (longest axis for non-nodal 
lesions, shortest axis for measurable malignant nodal lesions). 
Non-target Lesions: All other lesions (or sites of disease) including all non-measurable lesions 
(including pathological lymph nodes with ≥ 10 to < 15 mm short axis) and all measurable lesions 
over and above the five target lesions are to be identified as non-target lesions and recorded at 
baseline.  
• Measurements of these lesions are not required, but the presence, absence, 
unequivocal progression of each is to be recorded throughout follow-up.  
• Lymph nodes that have a short axis < 10 mm are considered non-pathological and are 
not to be recorded or followed. 
Special Considerations 
Clinical Examination of Lesions: Superficial or visible lesions that cannot be assessed by CT 
scan or MRI will only be considered for response assessment if these lesions are biopsy-proven 
metastatic lesions and ≥ 10 mm in diameter. These lesions will be considered non-measurable 
and thus non-target for response assessment. 
Cystic Lesions: Cystic lesions thought to represent cystic metastases can be considered as 
measurable lesions if they meet the definition of measurability described above. However, if 
non-cystic lesions are present in the same patient, these are preferred for selection as target 
lesion.  
Bone Lesions: Bone scan, positron emission testing (PET) scan or plain films are not considered 
adequate imaging techniques to measure bone lesions. However, these techniques can be used to 
confirm the presence or disappearance of bone lesions. 
• Lytic bone lesions or mixed lytic-blastic lesions, with identifiable soft tissue 
components, that can be evaluated by cross-sectional imaging techniques such as CT 
or MRI can be considered as measurable lesions if the soft tissue component meets 
the definition of measurability described above. 
• Blastic bone lesions are non-measurable. 
Lesions with Prior Local Treatment: Lesions situated in a previously irradiated area, or in an 
area subjected to other locoregional therapy, are usually not considered measurable; however, if 
they meet the following criteria, they may be considered for study: 
• there has been prior documented progression in the lesion by at least 2 sequential CT 
or MRI scans performed after the completion of radiation, or  
• histopathological evidence of progression 
Additionally, if such lesions meet the criteria for measurability, they may be considered target 
lesions. 
 
 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
84 
Imaging Methods 
The same method of assessment and the same technique used to characterize each identified and 
reported lesion at baseline should be used during each follow-up assessment. Imaging-based 
evaluation is preferred to evaluation by clinical examination unless the lesion(s) being followed 
cannot be imaged but are assessable by clinical exam (referring to biopsy-proven visible 
lesions(s) at the vaginal apex).  
Chest X-ray: Lesions that are identified on chest X-ray must be confirmed and followed by CT 
scan. If there is/are pre-existing chest lesion(s) before the baseline tumor assessment, a chest X-
ray is not necessary to assess those lesions. The pre-existing chest lesion(s) must be assessed at 
baseline and followed by CT scans. 
Conventional CT or MRI: This guideline has defined measurability of lesions on CT scan based 
on the assumption that CT slice thickness is 5 mm or less. If CT scans have slice thickness 
greater than 5 mm, the minimum size for a measurable lesion is twice the slice thickness. MRI is 
also acceptable in certain situations (eg, for body scan) except for lung.  
CA-125: Tumor marker CA-125 alone cannot be used to assess response or determine 
progression; however, it will be followed. CA-125 assessments will be performed as indicated in 
Table 2. Patients whose CA-125 is above the upper normal limit at baseline will need to have 
their values normalize to ≤ upper normal limit, in addition to complete disappearance of 
measurable or evaluable disease, to be considered in complete response. 
Other methods of assessment, PET-CT, ultrasound and FDG-PET should not be used for 
response assessment in this study. 
Time Point Assessments 
Radiologic tumor evaluation by CT or MRI of chest, abdomen, and pelvis will be performed 
within 28 days before first dose of study drug and every 6 weeks (±1 week) from C1D1 for the 
first 36 weeks on study and every 12 weeks (± 3 weeks) thereafter. 
At baseline, tumors and lymph nodes are classified and documented as target or non-target per 
the definitions provided above. It is possible to record multiple non-target lesions involving the 
same organ as a single item (eg, ‘multiple liver metastases’).  
At all post-baseline evaluations, the baseline classification (target, non-target) is to be maintained 
and lesions are to be documented and described in a consistent fashion over time (eg, recorded in 
the same order on source documents and CRFs). 
For target lesions, measurements should be taken and recorded in metric notation. All tumor 
measurements must be recorded in millimeters. 
At each assessment, a sum of the diameters (longest for non-nodal lesions, short axis for nodal 
lesions) for all target lesions will be calculated and reported. The baseline sum of the longest 
diameters (SLD) will be used as reference to further characterize any objective tumor regression 
in the measurable dimension of the disease. The lowest SLD (nadir) since, and including, the 
baseline value will be used as reference for evaluating progression. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
85 
After baseline, the actual size of the target lesion should be documented, if possible, even if the 
lesions become very small. If in the opinion of the radiologist, the lesion has likely disappeared, 
0 mm should be recorded. If the lesion is present but too small to measure, an indicator of “too 
small to measure” will be provided on the CRF (a default value of 5 mm will be imputed during 
analysis).  
Non-target lesions are to be assessed qualitatively (present, resolved, or unequivocal 
progression) and new lesion, if any, are to be documented separately. 
At each evaluation, a time point response is to be determined for target lesions, non-target 
lesions, new lesions and overall. 
Time Point Response Criteria 
Target Lesion Time Point Response (TPR) 
Complete Response 
(CR) 
Disappearance of all target lesions. All pathological lymph nodes (whether 
target or non-target) must have reduction in short axis to < 10mm.  
Partial Response (PR) 
At least 30% decrease in the sum of diameters (SoD of target lesions, taking 
as reference the baseline SoD 
Progressive Disease 
(PD) 
At least a 20% increase in the SoD of target lesion, taken as reference the 
smallest (nadir) SoD since and including baseline. In addition to the relative 
increase of 20%, the SoD must also demonstrate an absolute increase of at 
least 5 mm. 
Stable Disease (SD) 
Neither sufficient shrinkage to qualify for PR nor sufficient increase to 
qualify for PD. 
Not Applicable (N/A) 
No target lesions identified at baseline 
Unable to Evaluate 
(UE) 
One or more target lesions are not imaged and the remainder of the SoD 
compared with the nadir SoD does not meet the criteria for PD 
If the target lesion for a patient meets the criteria for both PR and PD at a given time point, the target 
lesion response is PD. 
If the nadir SoD is 0 (ie, the patient had a prior target lesion CR), the re-appearance of any prior target 
lesions to any degree constitutes PD. 
Non-Target Lesion TPR 
Complete Response 
(CR) 
Disappearance of all non-target lesions and normalization of tumor marker 
level if tumor marker at baseline is above the upper normal limit. All lymph 
nodes must be non-pathological in size (< 10 mm short axis)  
Non-CR/Non-PD 
Persistence of one or more non-target lesion(s) and/or maintenance of CA-
125 above the normal limits if CA-125 at baseline is above the upper 
normal limit 
Progressive Disease 
(PD) 
Unequivocal progression of non-target lesions. Unequivocal progression 
should not normally trump target lesion status. It must be representative of 
overall disease status change, not a single lesion increase. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
86 
Not Applicable (N/A) 
No non-target lesions identified at baseline 
Unable to Evaluate 
(UE) 
One or more non-target lesions are not imaged and the remaining non-target 
lesions do not meet the criteria for PD 
If the target lesion for a patient meets the criteria for both PR and PD at a given time point, the target 
lesion response is PD. 
If the nadir SoD is 0 (ie, the patient had a prior target lesion CR), the re-appearance of any prior target 
lesions to any degree constitutes PD. 
New Lesion TPR 
Yes 
Lesion present at follow-up visit either for the very first time or re-
appearing (ie, lesion was present at baseline, disappeared at a follow-up 
visit and re-appeared later). 
No 
No new lesions present at follow-up 
Unable to Evaluate 
(UE) 
Patient non assessed or incompletely assessed for new lesion 
Determining Overall TPR 
Target Lesion TPR 
Non-Target TPR 
New Lesions TPR 
Overall TPR 
CR 
CR or NA 
No 
CR* 
CR 
Non-CR/non-PD 
No 
PR* 
CR 
UE 
No 
PR* 
PR 
Non-PD or NA or UE 
No 
PR* 
SD 
Non-PD or NA or UE 
No 
SD 
UE 
Non-PD 
No 
UE 
PD 
Any 
No or Yes or UE 
PD 
Any 
PD 
No or Yes or UE 
PD 
Any 
Any 
Yes 
PD 
NA 
CR 
No 
CR* 
NA 
Non-CR/non-PD 
No 
Non-CR/non-PD 
Non-PD 
Non-PD 
UE 
UE 
CR, complete response; PR, partial response; SD, stable disease; PD, progressive disease; UE, unable 
to evaluate; NA, not applicable (no such lesions at Screening); Any, CR, PR, SD, PD, NA or UE. 
The overall response at a given time point does not depend upon the overall response assigned at any 
prior time point. 
*Patients with an overall response of CR or PR must have a repeat tumor assessment performed no less 
than 4 weeks after the criteria for response are first met. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
87 
Confirmation - The main goal of confirmation of objective response is to avoid overestimating 
the observed response rate. For patients with an overall response of PR or CR a given time point, 
changes in tumor measurements must be confirmed by repeat assessments that should be 
performed no less than 4 weeks after the criteria for response are first met. However, the 
presence or absence of confirmation is not considered when assigning a time point response. 
Best Overall Response - Best overall response, incorporating confirmation requirements, will be 
derived during statistical analysis from the series of time point responses and need not be 
considered when assigning response at any time point. 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
88 
APPENDIX C. GYNECOLOGIC CANCER INTERGROUP (GCIG) 
CRITERIA FOR EVALUATION OF CA-125 
(Rustin 2004) 
On the basis of the available data and extensive discussions among the cooperative groups within 
the GCIG, it is recommended that the following definition of response be used in ovarian cancer 
trials so that response can be measured by either RECIST or CA-125 criteria. If the response is 
evaluable by both criteria, then the date of response will be the date of the earlier of the two 
events. 
Definition of response: 
• ≥ 50% reduction in CA-125 levels from baseline 
• the response must be confirmed and maintained for at least 28 days 
• the pretreatment sample must be ≥ 2.0 times the ULN and within two weeks before 
starting treatment 
• the date of response corresponds to the date when the CA-125 level is first reduced by 
50%  
To calculate CA-125 responses accurately, the following rules apply:  
• Intervening samples and the 28-day confirmatory sample must be less than or equal to 
(within an assay variability of 10%) the previous sample 
• Variations within the normal range of CA-125 levels will not interfere with the 
response definition.  
Evaluation of Progression 
Progression or Recurrence based on serum CA-125 levels will be defined on the basis of a 
progressive serial elevation of serum CA-125, according to the following criteria:  
a. Patients with elevated CA-125 pretreatment and normalisation of CA-125 must show 
evidence of CA-125 greater than, or equal to, two times the upper normal limit on 
two occasions at least one week apart, or  
b. Patients with elevated CA-125 pretreatment, which never normalises must show 
evidence of CA-125 greater than, or equal to, two times the nadir value on two 
occasions at least one week apart, or  
c. Patients with CA-125 in the normal range pretreatment must show evidence of 
CA125 greater than, or equal to, two times the upper normal limit on two occasions at 
least one week apart.  
Elevated values must be confirmed by two separate measurements obtained at least one week 
apart. CA-125 progression will be assigned the date of the first measurement that meets the 
criteria as noted. Patients are not evaluable by CA-125 if they have received mouse antibodies 
(unless the assay used has been shown not to be influenced by HAMA [Taylor 2005 and Rustin 
2005]) or if there has been medical and/or surgical interference with their peritoneum or pleura 
during the previous 28 days.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
89 
A patient may be declared to have progressive disease on the basis of either the objective 
RECIST criteria or the CA-125 criteria. The date of progression will be the date of the earlier of 
the two events if both are documented. 
Definition of progression after first-line therapy in ovarian cancer as proposed by the 
GCIG  
GCIG 
subcategorized 
group 
RECIST Measurable/non-measurable 
disease 
 
CA-125 
A 
Compared to baseline (or lowest sum 
while on study if less than baseline), a 
20% increase in sum of longest diameters 
(RECIST definition) 
or 
Any new lesions (measurable or non-
measurable) 
Date PD: date of documentation of 
increase or new lesions 
A
N
D 
/ 
O
R 
CA-125 ≥ 2 x ULN 
documented on two 
occasions # 
Date of PD: first date of 
the CA-125 elevation to  
≥ 2x nadir value 
 
B 
As for A 
CA-125 ≥ 2 x nadir value 
on two occasions # 
Date of PD: first date of 
the CA-125 elevation to  
≥ 2x nadir value 
B 
As for A 
As for A 
GCIG groups A, B & C defined above.  
# Repeat CA-125 any time, but normally not less than 1 week after the first elevated CA-125 level. CA-125 levels 
sampled after patients received mouse antibodies (unless the assay used has been shown not to be influenced by 
HAMAa,b) or if there has been medical and/or surgical interference with their peritoneum or pleura during the 
previous 28 days, should not be taken into account. 
a Taylor PT, Haverstick D. J Natl Cancer Inst 2005, 97:151, Re: new guidelines to evaluate the response to 
treatment in solid tumors [ovarian cancer].  
b Rustin GJS. J Natl Cancer Inst 2005, 97:152, Re: new guidelines to evaluate the response to treatment in solid 
tumors [ovarian cancer]. 
 
Timing of CA-125 assessments: 
The GCIG recommends that CA-125 measurements be taken at specific time intervals.  
• The first sample would be collected within two weeks before treatment is started 
• CA-125 assessments will be performed as indicated in Table 2.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
90 
• For each patient, the same assay method must be used and the assay must be tested in 
a quality-control scheme. Patients are not evaluable by CA-125 if they have received 
mouse antibodies or if there has been medical and/or surgical interference with their 
peritoneum or pleura during the previous 28 days.  
This CA-125 response definition has been produced to evaluate relapse therapy. If assessing 
therapy that includes two treatment modalities for relapse (eg, surgery and chemotherapy), any 
CA-125 response results from both treatments. CA-125 cannot distinguish between the effects of 
each treatment. To calculate response rates in protocols, an ITT analysis should be used that 
includes all patients with an initial CA-125 level of at least twice the ULN as eligible and 
evaluable. In addition to calculating response rates in protocols, it is advisable to record those 
patients who have both a CA-125 response and whose CA-125 level falls to within the normal 
range.  


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
91 
APPENDIX D. LIST OF CONCOMITANT MEDICATIONS REQUIRING 
CAREFUL MONITORING 
CYP Enzymes 
Sensitive Substrates 
Substrates with Narrow 
Therapeutic Range 
CYP3A 
Alfentanil, aprepitant, budesonide, buspirone, 
conivaptan, darifenacin, darunavir, dasatinib, 
dronedarone, eletriptan, eplerenone, 
everolimus, felodipine, indinavir, fluticasone, 
lopinavir, lovastatin, lurasidone, maraviroc, 
midazolam, nisoldipine, quetiapine, 
saquinavir, sildenafil, simvastatin, sirolimus, 
tolvaptan, tipranavir, triazolam, vardenafil 
Alfentanil, astemizole, 
cisapride, cyclosporine, 
dihydroergotamine, ergotamine, 
fentanyl, pimozide, quinidine, 
sirolimus, tacrolimus,  
terfenadine 
Ref: FDA drug development resources: 
(http://www fda.gov/drugs/developmentapprovalprocess/developmentresources/druginteractionslabeling/ucm09366
4.htm#classSub). 


Mirvetuximab Soravtansine (IMGN853) 
Dated 28 August 2020 
Protocol Number IMGN853-0417 
 
 
Confidential and Proprietary 
ImmunoGen, Inc. 
92 
APPENDIX E. ADJUSTED IDEAL BODY WEIGHT (AIBW) 
CALCULATION 
 
Adjusted Ideal Body Weight (AIBW) 
AIBW = IBW1 + 0.4 (Actual weight – IBW1) 
 
Ideal Body Weight (IBW) 
IBW1 (female) = 0.9H1-92 
 
(1H=height in cm; W=weight in kg) 

SAP_001.pdf: 




Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
3
TABLE OF CONTENTS 
SPONSOR SIGNATURE PAGE ....................................................................................................2 
LIST OF ABBREVIATIONS ..........................................................................................................6 
1.
INTRODUCTION ........................................................................................................8 
1.1. 
Background ...................................................................................................................8 
2.
STUDY DESIGN .........................................................................................................8 
2.1. 
Protocol Objectives .......................................................................................................8 
2.1.1. 
Primary Objective .........................................................................................................8 
2.1.2. 
Secondary Objectives ...................................................................................................8 
2.1.2.1. 
Key Secondary Objectives: ...........................................................................................8 
2.1.2.2. 
Additional Secondary Objectives: ................................................................................8 
2.1.2.3. 
Exploratory Objectives .................................................................................................8 
2.1.3. 
Study Endpoints ............................................................................................................9 
2.1.3.1. 
Primary Endpoint ..........................................................................................................9 
2.1.3.2. 
Key Secondary Endpoint ..............................................................................................9 
2.1.3.3. 
Exploratory Endpoints ..................................................................................................9 
2.2. 
Study Overview ..........................................................................................................10 
2.2.1. 
Study Population .........................................................................................................10 
2.2.2. 
Power and Sample Size ..............................................................................................10 
2.2.3. 
Treatment Randomization and Blinding .....................................................................11 
2.2.4. 
Assessment Schedule ..................................................................................................11 
2.3. 
Interventions ...............................................................................................................11 
2.3.1. 
Clinical Trial Material ................................................................................................11 
3.
GENERAL ANALYTICAL CONSIDERATIONS ...................................................11 
3.1. 
Data Sources ...............................................................................................................11 
3.2. 
Definition of Baseline .................................................................................................11 
3.3. 
Missing Data ...............................................................................................................11 
3.4. 
Multiple Assessments for the Same Assessment Time Point .....................................13 
3.5. 
Multiple Study Centers ...............................................................................................13 
3.6. 
Covariate Adjustment in Primary Analysis ................................................................13 
3.7. 
Sample Size Reassessment .........................................................................................13 
3.8. 
Interim Analyses .........................................................................................................13 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
4 
3.9. 
Timing of Final Analysis ............................................................................................13 
3.10. 
Test Sizes ....................................................................................................................14 
3.11. 
Hypothesis Testing and Multiple Comparisons ..........................................................14 
3.11.1. 
Primary Endpoint ........................................................................................................14 
3.11.2. 
Secondary Endpoints ..................................................................................................14 
3.12. 
Analysis Populations ..................................................................................................14 
3.12.1. 
Screened ......................................................................................................................14 
3.12.2. 
Safety Population ........................................................................................................15 
3.12.3. 
Efficacy Evaluable Population ...................................................................................15 
3.12.4. 
CA-125-Evaluable Population ....................................................................................15 
3.12.5. 
PK Analysis Population ..............................................................................................15 
3.13. 
Data Display Characteristics .......................................................................................15 
4. 
PATIENT ACCOUNTABILITY ...............................................................................16 
4.1. 
Patient Characteristics ................................................................................................16 
4.1.1. 
Demography ...............................................................................................................16 
4.1.2. 
Baseline Height, Weight, and AIBW .........................................................................16 
4.1.3. 
Medical History ..........................................................................................................16 
4.1.4. 
Disease Characteristics, Prior Therapy, and Gene Mutations ....................................16 
4.2. 
Patient Disposition ......................................................................................................17 
4.2.1. 
Screened and Treated Patients ....................................................................................17 
4.2.2. 
Patient Disposition ......................................................................................................17 
4.2.3. 
Protocol Deviations and Population Inclusions ..........................................................17 
5. 
EFFICACY ANALYSES ...........................................................................................18 
5.1. 
Efficacy Outcomes ......................................................................................................18 
5.1.1. 
Best Overall Response ................................................................................................18 
5.1.1.1. 
ORR ............................................................................................................................18 
5.1.1.2. 
DOR ............................................................................................................................18 
5.1.1.3. 
Time to Response .......................................................................................................19 
5.1.2. 
PFS ..............................................................................................................................19 
5.1.3. 
OS ...............................................................................................................................20 
5.1.4. 
GCIG CA-125 Response ............................................................................................20 
5.2. 
Primary Efficacy Outcome Analysis ..........................................................................20 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
5 
5.3. 
Secondary Efficacy Analyses .....................................................................................20 
5.3.1. 
Key Secondary Efficacy Analysis ..............................................................................20 
5.3.2. 
Additional Secondary Efficacy Analyses ...................................................................20 
5.4. 
Efficacy Analysis on Subgroups of Patients ...............................................................21 
5.5. 
Additional Sensitivity Analyses .................................................................................21 
5.6. 
Other Efficacy-related Summaries .............................................................................21 
6. 
SAFETY ANALYSES ...............................................................................................22 
6.1. 
Exposure .....................................................................................................................22 
6.2. 
AEs .............................................................................................................................22 
6.2.1. 
Fresh Biopsy Patient AE .............................................................................................25 
6.2.2. 
Infusion-related Reactions ..........................................................................................25 
6.3. 
Clinical Laboratory Results ........................................................................................25 
6.4. 
Vital Signs ..................................................................................................................26 
6.5. 
ECGs ...........................................................................................................................27 
6.6. 
Concomitant Medications ...........................................................................................27 
6.7. 
Concomitant Procedures .............................................................................................28 
6.8. 
Ophthalmic Examinations ..........................................................................................28 
6.9. 
Ocular Symptom Assessments ...................................................................................29 
6.10. 
Corticosteroid and Lubricating Eye Drop Compliance ..............................................29 
6.11. 
Transfusions ................................................................................................................29 
6.12. 
Physical Examination .................................................................................................29 
6.13. 
ECOG PS ....................................................................................................................29 
7. 
IMMUNOGENICITY ................................................................................................29 
8. 
BIOMARKERS ..........................................................................................................29 
9. 
PHARMACOKINETICS ...........................................................................................30 
10. 
REFERENCES ...........................................................................................................30 
 
LIST OF TABLES 
Table 1: 
History of Protocol Amendments .................................................................................8 
Table 2: 
Analysis Populations ..................................................................................................14 
Table 3: 
PFS Definitions ...........................................................................................................19 
Table 4: 
Classification of Vital Signs .......................................................................................27 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
6
LIST OF ABBREVIATIONS 
Abbreviation or 
Specialist Term  
Explanation 
ADA 
Anti-drug antibodies 
AE 
Adverse event 
AIBW 
Adjusted ideal body weight 
ALT 
Alanine aminotransferase 
AST 
Aspartate aminotransferase 
BICR 
Blinded Independent Central Review 
BOR 
Best overall response 
BRCA 
Breast cancer susceptibility gene 
C1D1 
Cycle 1 Day 1 
CA-125 
Cancer antigen 125 
CI 
Confidence interval 
CR 
Complete response 
CTCAE 
Common Terminology Criteria for Adverse Events 
DOR 
Duration of response 
ECG 
Electrocardiogram 
ECOG PS 
Eastern Cooperative Oncology Group Performance Status 
EOC 
Epithelial ovarian cancer 
EOS 
End of Study 
FRα 
Folate receptor alpha 
GCIG 
Gynecologic Cancer Intergroup 
IMGN 
ImmunoGen 
LOQ 
Limit of Quantitation 
MedDRA 
Medical Dictionary for Regulatory Activities 
MIRV 
mirvetuximab soravtansine 
ORR 
Objective response rate 
OS 
Overall survival 
PD 
Progressive disease 
PFS 
Progression-free survival 
PK 
Pharmacokinetics 
PR 
Partial response 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
7 
Abbreviation or 
Specialist Term  
Explanation  
PROC 
Platinum resistant ovarian cancer 
PT 
Preferred term 
Q3W  
Every 3 weeks  
RECIST  
Response Evaluation Criteria in Solid Tumors  
RMST 
Restricted mean survival time 
SAE  
Serious adverse event  
SAP  
Statistical analysis plan  
SMQ 
Standard MedDRA Query 
SOC 
System organ class 
TBILI 
Total bilirubin 
TEAE  
Treatment-emergent adverse event  
TTR 
Time to response 
ULN  
Upper limit of normal  
WHO Drug  
World Health Organization Drug Dictionary 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
8
1.
INTRODUCTION
1.1. 
Background
This Statistical Analysis Plan (SAP) is based on Amendment 2 of Protocol IMGN853-0417, 
dated 28August2020.  
A brief history of protocol amendments is presented in Table 1. 
Table 1: 
History of Protocol Amendments 
Version 
Approval Date 
Salient Changes (if any)* 
Original Protocol 
23October2019 
N/A 
Amendment 1 
18December2019 
Increased sample size from 91 to 105 
Amendment 2 
28August2020 
N/A 
*Changes expected to require accommodation in analysis plan.
This SAP will govern the analysis of study data. The plan for the primary efficacy analysis and 
all other analyses may be modified prior to final database lock. Any deviations from the SAP 
will be documented as such in the study report.  
2.
STUDY DESIGN
2.1. 
Protocol Objectives 
2.1.1. 
Primary Objective 
•
To determine the efficacy of mirvetuximab soravtansine (MIRV) in patients with
platinum resistant ovarian cancer (PROC) and high folate receptor-α (FRα)
expression.
2.1.2. 
Secondary Objectives
2.1.2.1. 
Key Secondary Objectives: 
•
To determine the durability of response to MIRV in patients with PROC and high
FRα expression.
2.1.2.2. 
Additional Secondary Objectives: 
•
To evaluate the safety and tolerability of MIRV.
•
To further characterize the clinical activity of MIRV in patients with PROC and high
FRα expression.
2.1.2.3. 
Exploratory Objectives 




Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
10 
2.2. 
Study Overview 
This study is designed to evaluate the efficacy and safety of MIRV in women with PROC and 
high FRα expression.  
Eligible patients will receive MIRV 6 mg/kg AIBW Q3W until disease progression, 
unacceptable toxicity, withdrawal of consent, death, or until the Sponsor terminates the study 
(whichever comes first).  
Tumor assessments, including radiological assessments by CT/MRI scans will be performed at 
Screening and subsequently every 6 (±1) weeks from C1D1 for the first 36 weeks then every 12 
(±3) weeks until disease progression, death, the initiation of subsequent anticancer therapy, or 
patient’s withdrawal of consent, whichever occurs first. CT/MRI scans will be collected for 
sensitivity analysis by blinded independent central review (BICR). 
Patients who discontinue MIRV for reasons other than progressive disease (PD) will continue 
with tumor assessments until documentation of PD or the start of new anticancer therapy, 
whichever comes first.  
All patients who discontinue MIRV will be followed for survival every 3 months (±1 month) 
until death, lost to follow-up, withdrawal of consent for survival follow-up, or End of Study 
(EOS), whichever comes first.  
2.2.1. 
Study Population 
All patients must have confirmed diagnosis of high-grade serous EOC, primary peritoneal 
cancer, or fallopian tube cancer. Patients must also have the following: 
• Patients must have at least 1 lesion that meets the definition of measurable disease by 
RECIST v1.1 (radiologically measured by the Investigator). 
• Patients must have received at least 1 but no more than 3 prior systemic lines of 
anticancer therapy, including at least 1 line of therapy containing bevacizumab, and 
for whom single-agent therapy is appropriate as the next line of treatment. 
• Patient’s tumor must be positive for FRα expression as defined by the Ventana 
FOLR1 (FOLR-2.1) CDx assay. 
See Protocol IMGN853-0417, Section 3.1 for a complete list of the inclusion/exclusion criteria. 
2.2.2. 
Power and Sample Size  
The primary endpoint of this study is ORR as assessed by the investigator. The study is designed 
to test the null hypothesis that the ORR is 12% (Eisenhauer 2009, Pujade-Lauraine 2014). The 
ORR will be estimated using the efficacy evaluable population as defined in Section 3.12.3. 
Approximately 110 patients will be enrolled so that a total of 105 patients will be efficacy 
evaluable. A sample size of 105 efficacy evaluable patients achieves 90% power to detect a 
difference in ORR of 12% (24% vs 12%) using a one-sided binomial test. The target significance 
level (one-sided α level) is 0.025. The actual significance level achieved by this test is 0.0242. 
These results assume that the ORR is 12% under the null hypothesis and 24% under the 
alternative hypothesis. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
11 
2.2.3. 
Treatment Randomization and Blinding 
Randomization and blinding are not applicable in this single-arm, open-label study.  
2.2.4. 
Assessment Schedule 
See Protocol IMGN853-0417, Table 2 for study schedule of assessments. 
2.3. 
Interventions 
2.3.1. 
Clinical Trial Material 
MIRV will be administered at 6 mg/kg AIBW as an IV infusion following preparation as 
outlined in the Pharmacy Manual on day 1 of every 3-week cycle.  
The protocol provides additional details in Protocol IMGN853-0417, Section 5.4. 
3. 
GENERAL ANALYTICAL CONSIDERATIONS 
3.1. 
Data Sources 
Data will be captured using validated, electronic data capture (EDC) systems. Data will be 
documented in various source documents (eg, the patient medical chart) and then manually 
entered into the clinical trial database. Protocol IMGN853-0417, Section 11 provides additional 
details regarding data recording and handling. 
3.2. 
Definition of Baseline 
Study Day 1 (ie, Cycle 1 Day 1) will be designated as the first day a patient receives MIRV. The 
baseline value is defined as the last non-missing value on or before the date of first dose of 
MIRV.  
3.3. 
Missing Data 
Partial dates are allowed in the clinical database for subsequent anti-cancer therapy start date, 
adverse event (AE) onset and resolution dates, concomitant medication start and stop dates, and 
concomitant procedure dates. An entry for the year is required in the clinical database for each of 
these dates. Only the month and day may be entered as unknown. Prior anticancer systemic 
therapy start and stop dates and subsequent anticancer therapy stop date allows for unknown 
dates in the clinical database. Dates from these forms will be reported in listings as collected. 
Every effort will be made to query missing dates.  
For records with missing AE onset date, the following procedure will be employed for use in 
determining whether the AE is treatment emergent: 
• AE onset dates with missing day and non-missing month will be assumed to occur on 
the first day of the non-missing month, except for AEs occurring in the first month of 
dosing, in which case the date will be the first day of dosing. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
12 
• AE onset dates with missing month will be assumed to occur on the first day of the 
non-missing year (ie, January 1), except for AEs occurring in the first year of dosing, 
in which case the date will be the first day of dosing.  
For records with a missing medication start and/or stop date, the following procedure will be 
employed for use in determining whether the medication is prior or concomitant: 
• Medication start dates with a missing day and non-missing month will be assumed to 
occur on the first day of the non-missing month, except for medications occurring in 
the first month of dosing, in which case the date will be the first day of dosing. 
• Medication start dates with missing month will be assumed to occur on the first day 
of the non-missing year (ie, January 1), except for medications occurring in the first 
year of dosing, in which case the date will be the first day of dosing.  
• Medications that are not ongoing and have a medication stop date with a missing day 
and non-missing month will be assumed to occur on the last day of the non-missing 
month. 
• Medications that are not ongoing and have a medication stop date with a missing 
month will be assumed to occur on the last day of the non-missing year (ie, 
December 31). 
For records with a missing procedure date, the following procedure will be employed for use in 
determining whether the procedure is prior or concomitant: 
• Procedure dates with a missing day and non-missing month will be assumed to occur 
on the first day of the non-missing month, except for procedures occurring in the first 
month of dosing, in which case the date will be the first day of dosing. 
• Procedure dates with missing month will be assumed to occur on the first day of the 
non-missing year (ie, January 1), except for procedures occurring in the first year of 
dosing, in which case the date will be the first day of dosing.  
For records with a missing prior anti-cancer systemic therapy start and/or stop date, and/or 
disease progression date from prior therapy, the following procedure will be employed for use in 
calculating the platinum-free interval (PFI):  
• If the stop date of prior platinum therapy is completely missing OR only the year is 
available, the PFI will be set as missing. 
• If both year and month of stop date of prior platinum therapy are available and only 
day is missing, the stop date will be imputed by the first day of the month. 
• If the disease progression date from prior platinum therapy is completely missing OR 
only the year is available, the PFI will be set as missing. 
• If both year and month of disease progression date from prior platinum therapy are 
available and only day is missing, the date of disease progression will be imputed by 
the last day of the month. 
For records with a missing subsequent anti-cancer therapy start date, the following procedure 
will be employed for use in deriving efficacy variables such as PFS and BOR. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
13 
• The start date of subsequent anti-cancer therapy will be imputed by the earliest 
possible date that is not contradicting with any other available data in the database. 
For records with a partial death date, the following procedure will be employed for use in 
deriving time to event variables (PFS, OS, DOR). 
• The death date will be imputed by the earliest possible date that is not contradicting 
with any other available data in the database. 
All other data will be reported as they are collected. No imputation methods will be used to 
replace missing data unless otherwise stated in this document.  
3.4. 
Multiple Assessments for the Same Assessment Time Point 
In the case of multiple observations at a specific visit, the first non-missing measurement will be 
used for analysis, unless multiple study assessments are expected (eg, pre-dose vs post-dose). 
When multiple study assessments are expected, the first non-missing measurement for the visit 
and assessment time point will be used for analysis. 
3.5. 
Multiple Study Centers 
No adjustment for study center is planned.  
3.6. 
Covariate Adjustment in Primary Analysis 
No covariate adjustment will be made. 
3.7. 
Sample Size Reassessment 
Not applicable. 
3.8. 
Interim Analyses 
No interim analysis is planned for this study. 
3.9. 
Timing of Final Analysis 
To allow for reasonable duration on treatment to achieve a confirmed response, the final analysis 
for ORR will be conducted after all efficacy evaluable patients (defined in Section 3.12.3) have:  
• undergone at least 4 post-baseline tumor assessments, or 
• experienced radiological disease progression, or  
• died or had clinical progression within 105 days of first dose of MIRV, or 
• withdrawn from study for other reasons 
It is estimated that the final analysis will be conducted approximately 6 months after the last 
patient is enrolled. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
14
3.10. 
Test Sizes 
For the primary endpoint of ORR, the null hypothesis that ORR is 12% will be tested against 
1-sided Type I error (α) of 0.025. This study will reject the null hypothesis if the lower bound of 
95% (2-sided) confidence interval (CI) for ORR is greater than 12%.
3.11. 
Hypothesis Testing and Multiple Comparisons 
3.11.1. 
Primary Endpoint 
In this single-arm study, hypothesis testing for the primary endpoint of ORR is performed using 
a confidence interval approach. Instead of reporting a p-value, 95% CI will be reported. Multiple 
comparison is not applicable. 
3.11.2. 
Secondary Endpoints 
The secondary endpoints of DOR, GCIG CA-125 response rate, PFS, and OS will be evaluated 
to further characterize the efficacy of MIRV. No formal hypothesis testing will be performed on 
secondary endpoints. 
3.12. 
Analysis Populations 
Six (6) analysis populations will be defined for use with various analyses. Table 2 illustrates the 
relationship between each population and the analyses for which the data from the population 
will be used. Baseline and patient disposition analyses will be conducted on efficacy evaluable 
population only if there is at least 5% difference between safety population and efficacy 
evaluable population. 
Table 2: 
Analysis Populations 
Analysis Population 
Analysis 
Reason for 
Screen 
Failure 
Baseline 
Patient 
Disposition 
Efficacy 
Safety 
PK 
Analysis 
Screened 
X 
Safety 
X 
X 
X 
Efficacy Evaluable by 
Investigator 
X 
Efficacy Evaluable by 
BICR 
X 
CA-125 Evaluable 
CA-125 only 
PK Analysis Population 
X 
3.12.1. 
Screened 
The Screened population includes all patients entered into the clinical database who have signed 
an informed consent.  


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
15 
3.12.2. 
Safety Population 
All patients who received at least 1 dose of MIRV will be included in the Safety population. 
3.12.3. 
Efficacy Evaluable Population 
The Efficacy Evaluable population is defined as all patients in the Safety population who have 
measurable disease at baseline.  
• Efficacy evaluable population for efficacy measurements based on investigator’s 
assessment (ORR, DOR, PFS per investigator): this population includes all patients in 
the safety population who have measurable disease at baseline per investigator. 
• Efficacy evaluable population for efficacy measurements based on BICR assessment 
(ORR, DOR, PFS per BICR): this population includes all patients in the safety 
population who have measurable disease at baseline per BICR. 
3.12.4. 
CA-125-Evaluable Population 
The CA-125-Evaluable population is defined as all patients in the Safety population whose 
pretreatment sample is ≥ 2.0 times the upper limit of normal (ULN), within 2 weeks prior to first 
dose of MIRV, and who have at least 1 post-baseline CA-125 evaluation.  
3.12.5. 
PK Analysis Population 
The PK analysis population is defined as all patients who have at least one non-missing PK 
concentration data point.  
3.13. 
Data Display Characteristics 
Data displays produced for this study will include summary tables, data listings, and figures.  
Data listings will report the data reported in the clinical database or derived for each patient. 
Data will be ordered by patient number, and date/time of assessment if applicable. When 
expedient, additional levels of ordering hierarchy may reflect subsets of assessments within 
patient. Data listings will not display patient initials. 
Summary tables will display summary statistics calculated for the analysis population, unless 
described otherwise.  
The summary statistics displayed will be a function of the type of data associated with the 
summarized assessment. Unless stated otherwise, continuous data will be summarized with the 
number of non-missing values, mean, standard deviation, minimum, median, and maximum. 
Categorical data will be summarized with the number of non-missing values and the numbers of 
values equal to each of the possible values. Percentages of patients with each of the possible 
values will be calculated from the number of patients in the corresponding analysis population, 
unless stated otherwise. Some continuous variables may also be grouped into categorical levels 
and evaluated in frequency tables. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
16 
4. 
PATIENT ACCOUNTABILITY 
4.1. 
Patient Characteristics 
Patient characteristics will be summarized and listed for the Safety population. These summaries 
will also be produced for the Efficacy Evaluable population if more than 5% of patients in the 
Safety population are excluded from the Efficacy Evaluable population. 
4.1.1. 
Demography 
Data collected about the following patient characteristics at the screening visit will be 
summarized as follows: 
• Age is collected in the clinical database at the time of patient registration. As this is a 
global study, there are certain regions where local regulations prohibit the collection 
of a complete date of birth. Therefore, age will not be recalculated for analysis 
purposes. The collected age will be used for summarization. 
• Sex 
− Childbearing potential (female only, yes/no) 
• Ethnicity 
• Race 
All demography data, including informed consent date, will be listed. 
4.1.2. 
Baseline Height, Weight, and AIBW 
Baseline height, weight, and AIBW will be summarized and presented in a listing. 
4.1.3. 
Medical History 
Medical history will be coded using Medical Dictionary for Regulatory Affairs (MedDRA) 
(Version 24.0) and graded using Common Terminology Criteria for Adverse Events (CTCAE) 
Version 5.0, associating lower-level terms with preferred terms (PTs) and system organ classes 
(SOCs) by the primary hierarchy. Medical histories will be summarized as the number and 
percentage of patients who reported at least 1 medical history event; and number and percentage 
of patients who reported at least 1 medical history event in each SOC. Within each SOC, tables 
will display the number and percentage of patients reporting at least 1 medical history event as 
designated by PT. All medical history information will also be listed. 
4.1.4. 
Disease Characteristics, Prior Therapy, and Gene Mutations 
Listings of all collected data related to disease characteristics and prior therapy will be provided. 
A summary of the following elements will also be provided: 
• ECOG performance status (0/1) 
• Primary diagnosis (epithelial ovarian cancer, fallopian tube cancer, primary peritoneal 
cancer, other) 
• Histology 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
17 
• Disease stage at initial diagnosis 
• Histologic grade 
• Prior radiotherapy (yes/no) 
• Prior systemic therapy 
− The number of prior systemic therapies is defined as the number of distinct 
treatment regimens. 
• Prior cancer related surgery (yes/no) 
• Prior exposure to doxorubicin (yes/no), topotecan (yes/no), taxanes (yes/no) 
• Prior exposure to PARP inhibitors (yes/no/uncertain) 
− If patient participated in a double-blind randomized trial comparing PARP 
inhibitor to placebo and the actual treatment was unknown, patient will be 
summarized under ‘uncertain’ category. 
• Any BRCA mutations (yes [BRCA1, BRCA2]/no) 
• Primary platinum-free interval (months, ≤12 months vs >12 months) 
− Defined as time from last dose of 1st line platinum therapy to the date of disease 
progression and/or relapse following 1st line therapy. 
• Platinum-free interval (months, ≤3 months vs >3-6 months, vs >6 months) 
− Defined as time from last dose of latest line platinum therapy to the date of 
disease progression and/or relapse following that line of therapy. 
4.2. 
Patient Disposition 
4.2.1. 
Screened and Treated Patients 
The number and percentage of patients who were screened, treated (Safety population), not 
treated (screen failure), and reason for screen failure will be summarized overall, and by 
geographic region, country, and site. 
4.2.2. 
Patient Disposition  
A summary of patient disposition will summarize, for the Safety population, the number of 
patients treated and the reason for treatment and study discontinuation. This summary will also 
be produced for the Efficacy Evaluable population by Investigator if more than 5% of patients in 
the Safety population are excluded from the Efficacy Evaluable population. 
Percentage of patients who withdrew for each reason on the End-of-Treatment and End-of-Study 
forms will be calculated using all members of the relevant population for the denominator. 
The number and percentage of Safety population included in each analysis population defined in 
Section 3.12 will be presented. This table will be produced for all patients at all sites, pooled. 
4.2.3. 
Protocol Deviations and Population Inclusions 
Protocol deviations will be captured in a protocol deviation log. A summary of the number of 
patients with any protocol deviation will be provided for the Safety population.  


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
18 
Major protocol deviations will also be summarized in these categories: 
• Patients entered the study even though they did not satisfy the entry criteria. 
• Patients received incorrect dose. 
• Major deviations that affect safety and/or efficacy endpoints assessments. 
• Major deviations due to Covid-19 pandemic. 
• Deviations that impact the principles of ICH GCP regarding patient rights, safety, and 
well-being. 
• Other important deviations not otherwise described that may significantly affect a 
subject’s rights, safety, or well-being. 
5. 
EFFICACY ANALYSES 
The main efficacy analyses will use data from the Efficacy Evaluable population based on 
investigator’s assessment. Sensitivity analyses will be performed with BICR assessment.  
5.1. 
Efficacy Outcomes 
5.1.1. 
Best Overall Response 
Best overall response (BOR) for a patient is the best response designation as assessed by the 
Investigator recorded between the date of first dose of MIRV and the date of objectively 
documented PD per RECIST Version 1.1, the date of the start of new anti-cancer therapy, or the 
date of study discontinuation, whichever occurs first. When an analysis cutoff date is 
implemented, only radiological assessments occurring on or prior to the cutoff date will be used 
for analysis. Patients with an overall response of CR or PR must have a repeat tumor assessment 
performed no less than 4 weeks (28 days) after the criteria for response are first met. When stable 
disease is the best overall response, it must meet the minimum duration of 35 days (6 weeks – 
1-week window = 35 days from the date of first dose of MIRV). The confirmatory scan is valid 
following treatment discontinuation if the patient has not started a new anti-cancer therapy.  
5.1.1.1. 
ORR 
The ORR will be calculated as the number of patients with a confirmed BOR of CR or PR 
divided by the number of patients in the Efficacy Evaluable population. Patients without at least 
1 post-baseline RECIST assessment will be treated as non-responders (ie, these patients will 
contribute to the denominator, but not the numerator). 
5.1.1.2. 
DOR 
DOR is defined as the time from the date of the first response (CR or PR), whichever occurs 
first, to the date of PD or death from any cause, whichever occurs first. DOR is only defined for 
patients who have a confirmed BOR of CR or PR.  
Per the BOR definition, patients with an overall response of CR or PR must have a repeat tumor 
assessment performed no less than 4 weeks after the criteria for response are first met. The first 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
19
date at which a CR or PR response was noted will be used to calculate DOR, not the date of the 
confirmatory tumor assessment. 
Patients who started a new anti-cancer therapy prior to documented PD or death will be censored 
at the last radiological assessment prior to initiation of new anti-cancer therapy. Patients who did 
not have PD or death will be censored at the date of their last radiological assessment. Patients 
who had PD or death after missing 2 or more consecutive radiological assessments (PD or death 
date - last radiological assessment date +1 ≥ 105 days) will be censored at the date of their last 
radiological assessment before the missing radiological assessment. When an analysis cutoff date 
is implemented, only data (deaths or radiological assessments) occurring on or before the cutoff 
date will be used for analysis. 
5.1.1.3. 
Time to Response 
Time to response (TTR) is defined as the time from the date of first dose of MIRV until the date 
of the first observed CR or PR. TTR is only defined for patients who have a confirmed BOR of 
CR or PR. 
5.1.2. 
PFS 
PFS is defined as the time from the date of first dose of MIRV until the date of PD or death from 
any cause, whichever occurs first. PFS is defined based on radiological assessments and 
determined by the Investigator. Clinical progression is not considered a progression endpoint.  
Table 3 summarizes the rules to be used for PFS. When an analysis cutoff date is implemented, 
only data (deaths and radiological assessments) occurring on or prior to the cutoff date will be 
used for analysis. 
Table 3: 
PFS Definitions 
Situation 
Date of PFSa Event or Censoring 
Outcome 
No post-baseline radiological assessments, 
and patient did not die within 105 days of 
first dose 
Date of first dose 
Censored 
No post-baseline radiological assessments, 
and patient died within 105 days of first dose 
Date of death 
Death 
Death 
Date of death 
Death 
Radiological Progression 
Date of first radiological assessment 
indicating progression (ie, OR = PD). 
Progression 
New anti-cancer therapy prior to PD or death 
(including palliative radiotherapy during 
study treatment) 
Date of last radiological assessment 
prior to the start of the new anticancer 
therapy 
Censored 
No death or PD 
Date of last radiological assessment 
Censored 
PD or death after missing 2 or more 
consecutive radiological assessments (PD or 
death date - last radiological assessment date 
+1 ≥ 105 days)
Date of last adequate radiological 
assessment showing no PD 
Censored 
Abbreviations: OR = overall response; PD = disease progression; PFS = progression-free survival. 
a Includes radiographic progression only. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
20
5.1.3. 
OS 
OS is defined as the time from the date of first dose until the date of death from any cause. 
Patients who are alive or lost to follow-up at the analysis are censored at the last known date at 
which they were known to be alive. When an analysis cutoff date is implemented, only deaths 
occurring on or before the cutoff date are counted as OS events. Patients whose date of death or 
the last date at which the patient was known to be alive (eg, after the data cutoff date) will be 
censored at the analysis cutoff date. 
5.1.4. 
GCIG CA-125 Response 
A GCIG CA-125 response is defined as a ≥ 50% reduction in CA-125 levels from baseline. The 
response must be confirmed and maintained for at least 28 days. The CA-125 response will be 
conducted using the CA-125-Evaluable population. The date of response corresponds to the date 
when the CA-125 level is first reduced by 50%. The summary table for CA-125 will include the 
number (percentage) of patients in the CA-125-Evaluable population, and that number will then 
be used as the denominator for CA-125 response rate.  
5.2. 
Primary Efficacy Outcome Analysis 
The primary endpoint of ORR will be calculated based on the Efficacy Evaluable population and 
its 95% exact CI will be estimated using the Clopper-Pearson method. 
5.3. 
Secondary Efficacy Analyses 
5.3.1. 
Key Secondary Efficacy Analysis 
The key secondary endpoint of DOR will be summarized in patients with a confirmed BOR of 
CR or PR only. 
The distribution of DOR will be summarized using the Kaplan-Meier method. DOR rates will be 
reported at 3-month intervals (eg, 3 months, 6 months, etc.). Median DOR will be estimated from 
the 50th percentile of the corresponding Kaplan-Meier estimates. 95% CIs for the 3-month 
intervals and median DOR will also be provided.  
5.3.2. 
Additional Secondary Efficacy Analyses 
The following additional efficacy endpoints will be summarized. 
•
PFS
•
OS
•
TTR
•
GCIG CA-125 response
PFS and OS will be summarized using the Efficacy Evaluable population. Their distribution will 
be estimated using the Kaplan-Meier method. PFS and OS rates will be reported at 3-month 
intervals (eg, 3 months, 6 months, etc.). Median PFS and OS will be estimated the 50th percentile 
of the corresponding Kaplan-Meier estimates. The 95% CI for the 3-month intervals and median 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
21 
times will also be provided. Additionally, the restricted mean survival time (RMST) will also be 
reported at 3-month intervals (eg, 3 months, 6 months, etc.).  
The median follow-up time and its 95% CI will be estimated using reverse Kaplan-Meier method 
on OS. 
GCIG CA-125 response rate will be calculated using the CA-125 Response-Evaluable 
population and its 95% exact CI will be estimated using the Clopper-Pearson method. 
TTR will be summarized in patients with a confirmed BOR of CR or PR only with the simple 
summary statistics. 
5.4. 
Efficacy Analysis on Subgroups of Patients 
Efficacy endpoints (ORR, DOR, PFS, OS, and GCIG CA-125 response rate) will be analyzed 
with the following subgroups of patients: 
• Number of prior lines of therapy (1 vs 2 vs 3) 
• Prior exposure to PARPi (yes vs no vs uncertain) 
− If patient participated in a double-blind randomized trial comparing PARP 
inhibitor to placebo and the actual treatment was unknown, patient will be 
summarized under ‘uncertain’ category. 
• ADA status 
The summaries for ORR and GCIG CA-125 response include the response rate and its 95% exact 
CI. 
The summaries for time to event variables (DOR, PFS, and OS) include the number and 
percentage of events, median and its 95% CI. 
5.5. 
Additional Sensitivity Analyses 
Analysis of ORR, DOR, and PFS as assessed by BICR will be performed as sensitivity analysis 
using the same methods described in the previous sections. 
5.6. 
Other Efficacy-related Summaries 
Listings of efficacy-related data for will include the following: 
• All lesion assessments (target lesion, non-target lesion, new lesion) 
• New anti-cancer therapy 
• Investigator’s RECIST assessments 
• CA-125 results 
• Derived parameters for CA-125 response, BOR, PFS, DOR, and OS 
• Censoring for time-to-event variables 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
22 
6. 
SAFETY ANALYSES 
The main safety summary tables will use data from the Safety population. Listings will be 
provided for patients in the Safety population.  
6.1. 
Exposure 
Summary tables will be provided with the following information. 
Exposure to MIRV will be summarized with descriptive statistics for the number of doses 
received, the number of cycles received, duration of dosing (weeks), total cumulative dose (mg), 
absolute dose intensity (mg/kg/dose, calculated as total cumulative dose [mg])/number of valid 
drug administration records /AIBW [kg]). 
The number of infusions with dose decreased, and dose delayed will also be summarized. 
A listing will be provided with the information from all MIRV administration case report forms 
(CRFs) over the treatment period. 
6.2. 
AEs 
AEs will be documented on the AE CRF and monitored continuously throughout the study from 
the time of informed consent until 30 days after the patient’s last MIRV or until the event has 
resolved, stabilized, or returned to baseline. AEs attributed to study procedures, including those 
events that occur prior to the first dose, should also be documented on the AE CRF.  
AE data are available to ImmunoGen from 2 sources, the clinical database and the serious 
adverse event (SAE) forms. While reconciliation will be performed, the production of data 
summaries and listings will be based on the data collected on the clinical database.  
Pre-treatment AEs are defined as AEs with an onset date prior to the first dose of MIRV. TEAEs 
are defined as AEs with an onset date on or after the first dose of MIRV, and within 30 days of 
the last dose of MIRV or prior to the start of a new anti-cancer treatment, whichever occurs first. 
Medical history conditions that exist before the initiation of MIRV but worsen in severity during 
the study will also be recorded on the AE CRF as an AE and will be included as treatment-
emergent in the summary tables and listings.  
The adverse events will be coded using MedDRA (Version 24.0), associating lower-level terms 
with PT and SOC by the primary hierarchy. The tables will display the counts and percentages of 
patients who reported at least 1 TEAE in each SOC represented in the AE data. Within each 
SOC, the tables will display the counts and percentages of patients reporting at least 1 TEAE as 
designated by the PT.  
AEs are graded using CTCAE Version 5.0. AE summaries may include summaries for all AEs 
and by the maximum CTCAE grade for the item being summarized (ie, SOC or PT). In these 
cases, the outputs will include a row for All Grades as well as rows for the 5 potential CTCAE 
grades, Grade 1 (Mild), Grade 2 (Moderate), Grade 3 (Severe), Grade 4 (Life threatening or 
disabling), or Grade 5 (Death). AEs missing a severity grade will not be included in the Grade 1-
5 rows of the tables. An AE reported by a patient more than once will be represented in the most 
severe category. TEAEs will be categorized as MIRV-related if “Possibly Related”, “Probably 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
23 
Related”, or “Definitely Related” is selected by investigator. AEs missing relationship to MIRV 
will be included in the Related TEAE tables and listings. 
The following summary tables will be produced:  
• An overall summary of safety will summarize the numbers of patients with TEAEs of 
each grade and the number of patients who died during the study or within 30 days of 
last dose. 
• All TEAEs. 
• Serious TEAEs. 
• Non-Serious TEAEs (ie, TEAEs excluding SAEs). 
• Grade 3 or higher TEAEs. 
• TEAEs leading to drug withdrawal. This subset includes TEAEs with an action taken 
of drug permanently discontinued. 
• Related TEAEs leading to drug withdrawal. This subset includes TEAEs related to 
MIRV with an action taken of drug permanently discontinued. 
• TEAEs related to MIRV.  
• Serious, related TEAEs. 
• TEAEs leading to dose modifications (dose reduction or dose delay). 
− TEAEs leading to dose reduction. 
− TEAEs leading to dose delay. 
− TEAEs leading to dose reduction or dose delay. 
• Related TEAEs leading to dose modification (dose reduction or dose delay). 
− Related TEAEs leading to dose reduction. 
− Related TEAEs leading to dose delay. 
− Related TEAEs leading to dose reduction or dose delay. 
• Deaths on study treatment or within 30 days of the last dose. This table includes all 
deaths during study treatment or within 30 days of the last dose, regardless of cause 
of death. 
• TEAEs leading to death. This table includes all TEAEs with CTCAE Grade 5. 
• Related TEAEs leading to death. This table includes all TEAEs related to MIRV with 
CTCAE Grade 5. 
The following listings will be produced:  
• All pre-treatment AEs will be listed. 
• All AEs, sorted chronologically by patient. This listing includes SOC, PT, onset and 
end dates, and other relevant information. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
24 
• Serious TEAEs, sorted chronologically within patient. 
• TEAEs leading to drug withdrawal. This subset includes TEAEs with an action taken 
of drug permanently discontinued. 
• TEAEs leading to dose reduction or dose delay. 
• TEAEs related to MIRV.  
• Serious TEAEs related to MIRV.  
• TEAEs resulting in death. This listing includes TEAEs with a CTCAE grade of Grade 
5 (death). 
• All deaths, with an indication of whether the death occurred on study or within 
30 days of the last dose. 
The following groupings of TEAEs will be generated as part of the focused analysis of safety: 
• Ocular TEAEs. 
− A list of PTs for ocular AEs will be provided and finalized by the Sponsor before 
the final database lock. 
• Peripheral neuropathy TEAEs. 
− A list of PTs for peripheral neuropathy AEs will be provided and finalized by the 
Sponsor before the final database lock. 
• Pneumonitis. 
For each of the focused safety analysis groups, the following summary tables will be produced: 
• TEAEs by SOC, PT, and maximum CTCAE grade. 
• Related TEAEs by SOC, PT, and maximum CTCAE grade. 
• Serious TEAEs by SOC, PT, and maximum CTCAE grade. 
• Related serious TEAEs by SOC, PT, and maximum CTCAE grade. 
• TEAEs leading to discontinuation. 
• TEAEs leading to dose reduction or dose delay. 
• TEAEs leading to dose reduction. 
• TEAEs leading to dose delay. 
• Related TEAEs leading to discontinuation. 
• Related TEAEs leading to dose reduction or dose delay. 
• Related TEAEs leading to dose reduction. 
• Related TEAEs leading to dose delay. 
Additionally, a table will be produced which contains the following for each of the focused 
safety analysis groups: 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
25 
• The number of patients with at least 1 TEAE in each group, presented by treatment 
arm. 
• Time to first onset of each group of TEAEs. 
• Action taken with MIRV with respect to each group of TEAEs. 
For the focused safety analysis, the following listings will be produced: 
• Ocular TEAEs. 
• Peripheral neuropathy TEAEs. 
• Pneumonitis TEAEs. 
6.2.1. 
Fresh Biopsy Patient AE 
Summary of adverse events, not necessarily TEAEs, experienced within 7 days of fresh biopsy 
will be generated by SOC, PT, and CTCAE grade. A listing of AEs experienced within 7 days of 
biopsy will also be generated for patients who have undergone fresh biopsy. 
6.2.2. 
Infusion-related Reactions 
Both broad and narrow standard MedDRA query (SMQ) for hypersensitivity will be performed. 
A summary table of all TEAEs matching broad or narrow SMQ will be generated by SOC, PT, 
and CTCAE grade. A listing will also be generated. 
6.3. 
Clinical Laboratory Results 
Laboratory test results (including hematology, coagulation, serum chemistry, and urinalysis) and 
abnormal laboratory values will be presented in data listings. 
CTCAE Version 5.0 laboratory grades will also be presented. CTCAE grades will be derived 
based on laboratory results and will not factor in clinical evaluations. 
Shift tables summarizing the changes from baseline in severity of laboratory grades will be 
provided for laboratory parameters graded according to CTCAE Version 5.0. Grade 3 or higher 
laboratory values will be summarized based on the worst grade observed during MIRV treatment 
or within 30 days of last dose.  
Clinically significant values in liver function tests (LFTs) will be summarized by the following 
categories, using the maximum value while on MIRV. The denominator for the summaries will 
be the number of patients who had at least 1 non-missing value during treatment. The categories 
for each test are not mutually exclusive: 
• Aspartate aminotransferase (AST) 
− > 3 × ULN 
− > 5 × ULN 
− > 10 × ULN 
− > 20 × ULN 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
26 
• Alanine Aminotransferase (ALT) 
− > 3 × ULN 
− > 5 × ULN 
− > 10 × ULN 
− > 20 × ULN 
• AST or ALT 
− > 3 × ULN 
− > 5 × ULN 
− > 10 × ULN 
− > 20 × ULN 
• Total bilirubin (TBILI) 
− > ULN 
− > 2 × ULN 
• Alkaline phosphatase (ALP) 
− > 1.5 × ULN 
• (AST or ALT) and TBILI (concurrent) 
− AST or ALT > 3 × ULN and TBILI > 1.5 × ULN 
− AST or ALT > 3 × ULN and TBILI > 2 × ULN 
• (AST or ALT) and ALP and TBILI (concurrent) 
− AST or ALT > 3 × ULN and ALP < 2 × ULN and TBILI > 2 × ULN 
Here, concurrent means that all the associated LFTs must be from the same visit. In addition, 
worst postbaseline grade for LFTs will be summarized. Because baseline values of LFTs are 
already taken into account in CTCAE V5.0, shift table from baseline to worst postbaseline grade 
will not be generated for LFTs. 
Results from pregnancy tests will be provided in listings.  
6.4. 
Vital Signs 
Vital signs (including temperature, pulse rate, systolic blood pressure, diastolic blood pressure, 
and respiratory rate) will be collected throughout the study. Pulse rate and respiratory rate are 
optional. 
Vital signs results will be classified into 4 or 5 categories (low, borderline low, normal, 
borderline high, or high) according to Table 4 below. Shift tables based on this classification will 
be summarized from baseline to the last post-baseline visit value. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
27 
Table 4: 
Classification of Vital Signs 
Vital Sign 
Low 
Borderline 
Low 
Normal 
Borderline 
High 
High 
Heart Rate (beats per 
minute) 
< 50 
50-59 
60-90 
91-99 
≥ 100 
Systolic BP (mmHg) 
< 80 
- 
80-120 
121-139 
≥ 140 
Diastolic BP (mmHg) 
< 60 
- 
60-80 
81-89 
≥ 90 
Respiratory Rate 
(breaths per minute) 
< 12 
- 
12-20 
21-24 
≥ 25 
Temperature (°C) 
< 35.0 
35.0-36.4 
36.5-37.2 
37.3-37.9 
≥ 38.0 
6.5. 
ECGs 
ECGs are collected at screening visit only. All ECG results will be presented in data listings. If a 
different correction for QT is captured in the CRF, that QTc will be reported in the listing for 
that patient with QTcF.  
6.6. 
Concomitant Medications 
All medications and supportive therapy taken within 4 weeks prior to Cycle 1 Day 1 and through 
30 days after last study treatment must be recorded on the appropriate CRF. The identity of all 
medications, dosage, route of administration, frequency, duration of administration, and 
indication for use will be recorded in the appropriate sections of the CRF. 
Prior medications are defined as medications with a stop date prior to the first dose of MIRV.  
Concomitant medications are defined as medications which are taken during the course of study 
treatment and within 30 days of the last dose of MIRV, as follows:  
• Medications started before the first dose of MIRV, but with a stop date after the first 
dose of MIRV and within 30 days of the last dose of MIRV will be considered 
concomitant medications.  
• Medications started before the first dose of MIRV that are ongoing will be considered 
concomitant medications. 
• Medications started after the first dose of MIRV and within 30 days of the last dose of 
MIRV or before the start of a new anti-cancer treatment, whichever occurs first, are 
considered concomitant medications.  
• Medications started before the first dose of MIRV, but with a stop date after the first 
dose of MIRV and within 30 days of the last dose of MIRV or prior to the start of a 
new anti-cancer treatment, whichever occurs first, will be considered concomitant 
medications.  
Prior and concomitant medications will be coded using the March 2021 version of World Health 
Organization drug dictionary (WHO Drug). Summary tables will be provided for prior and 
concomitant medications.  


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
28 
Summary tables will be organized to display the anatomical main class of each coded medication 
(ATC Level 1 term) and, within that, the pharmacological subgroup (ATC Level 3 term) of the 
coded medication. The summary table will display number and percentage of patients who 
reported using at least 1 medication in each represented pharmacological subgroup. If a patient 
has more than 1 medication in the subgroup, the patient will be counted only once. 
A complete listing of medications will be generated by patient. The listing will indicate which 
medications are prior and which are concomitant. The listing will display entries from the 
concomitant medications form, ordered within patient by start date. The listing will display the 
recorded term from the CRF and the WHO Drug anatomical main class (ATC Level 1 term) and 
pharmacological subgroup (ATC Level 3 term). 
6.7. 
Concomitant Procedures 
All procedures within 4 weeks of Cycle 1 Day 1 and through 30 days after last study treatment 
must be recorded on the appropriate CRF.  
Prior procedures are defined as occurring before the first dose of MIRV (by procedure date).  
Concomitant procedures are defined as procedures with a procedure date on or after the first dose 
of MIRV, and within 30 days of the last dose of MIRV, as follows:  
• Procedures are defined as concomitant procedures with a procedure date on or after 
the first dose of MIRV, and within 30 days of the last dose of MIRV or prior to the 
start of a new anti-cancer treatment, whichever occurs first.  
Prior and concomitant procedures will be coded using MedDRA (Version 24.0), associating 
lower-level terms with PT and SOC by the primary hierarchy. Summary tables will be provided 
for prior and concomitant procedures. The tables will display number and percentage of patients 
who reported at least 1 procedure in each SOC represented in the CRF data. Within each SOC, 
the tables will display number and percentage of patients reporting at least 1 concomitant 
procedure as designated by PT. 
A complete listing of procedures will be generated. The listing will indicate which procedures 
are prior and which are concomitant. The listing will display entries from the concomitant 
procedures form, ordered within patient by date of procedure. The listing will display the 
recorded term from the CRF and the SOC and PT.  
6.8. 
Ophthalmic Examinations 
Ophthalmic Examinations are collected at the Screening, End-of-Treatment, and 30-Day Follow-
up Visits. Results of the ophthalmic examinations will be presented in data listings.  
Worst decline in both eye best corrected visual acuity (BCVA) grade will be summarized. Shift 
of both eye BCVA from baseline to worst post baseline will be summarized using the following 
categories: ≥20/40, <20/40 to ≥20/200, and <20/200. 
Shift of intraocular pressure (mmHg) from baseline to highest post baseline value will be 
summarized using the following categories: ≤22 and >22. 
Cataract shift from baseline to maximum on treatment CTCAE grade will be summarized based 
on data collected on the ocular symptom assessments CRF. 


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
Confidential and Proprietary 
29
6.9. 
Ocular Symptom Assessments 
Results of the ocular assessments will be presented in data listings. 
6.10. 
Corticosteroid and Lubricating Eye Drop Compliance 
All compliance information collected on the CRF will be presented in data listings. 
6.11. 
Transfusions 
All transfusions recorded on the CRF will be presented in data listings. 
6.12. 
Physical Examination 
Physical examination results will be presented in data listings. 
6.13. 
ECOG PS 
ECOG PS results will be presented in data listings. Baseline ECOG PS will be summarized in 
disease characteristics table (Section 4.1.4). 
7. 
IMMUNOGENICITY
 Patients will be grouped into 
five categories based on ADA status before and post the first dose of MIRV:  
•
Treatment-emergent ADAs: Patients who had a baseline-negative ADA result who
developed ADAs at any time after initial administration of drug.
•
Treatment-enhanced ADAs: Patients who had a baseline positive ADA result in
whom the assay signal was enhanced (greater than baseline titer by ≥ 4 folds) at any
time after initial drug administration.
•
Treatment-unaffected ADA: Patients who had a baseline-positive ADA result in
whom the assay signal was not enhanced (negative or not greater than baseline titer
by ≥ 4 folds) at any time after initial drug administration.
•
Seronegative: a patient who tests negative at all visits.
If a titer is below LLQ, it will be imputed as half of LLQ. 
Efficacy endpoints ORR and DOR will be analyzed by the above ADA status group. 
TEAE by SOC and PT will be summarized for the above ADA status group. 
8.
BIOMARKERS
The exploratory biomarker analyses for this study will be covered by a separate, independent 
analysis plan.  


Statistical Analysis Plan – Protocol IMGN853-0417 
mirvetuximab soravtansine 
 
 
Confidential and Proprietary 
30 
9. 
PHARMACOKINETICS 
Plasma concentration data collected in this study will be listed and summarized for the PK 
analysis population. Mean and 95% CI, standard deviation, geometric mean, coefficient of 
variation (CV, expressed as percentage), median, Q1, Q3, min, and max will be reported by visit. 
Data points that are below the lower limit of quantitation will be excluded from the analyses. 
10. 
REFERENCES 
Eisenhauer, E.A., Therasse, P., Bogaerts, J, et al. New response evaluation criteria in solid 
tumours: Revised RECIST guideline (version 1.1), Eur J Cancer. 2009;45(2):228-247. 
Pujade-Lauraine E, Hilpert F, Weber B et al. Bevacizumab combined with chemotherapy for 
platinum-resistant recurrent ovarian cancer: The AURELIA open-label randomized phase III 
trial. J Clin Oncol. 2014;32(13):1302-1308.