Tagraxofusp (SL-401) in Patients With Chronic Myelomonocytic Leukemia (CMML)
Phase: PHASE1
Conditions: Myelofibrosis, Chronic Myelomonocytic Leukemia
Sponsor: Stemline Therapeutics, Inc.

Tagraxofusp (SL-401) in Patients with Chronic Myelomonocytic Leukemia 
(CMML) 
Study Product:
Tagraxofusp (SL-401)
Protocol Number:
STML-401-0314
IND Number:
114513
Issue Date:
30 September 2021
Sponsor:
Stemline Therapeutics, Inc.
750 Lexington Avenue-11th Floor
New York, NY 10022
Telephone: 646-502-2310
Medical Monitor:
Phone:
Email:
Sponsor Signatory:
Office:
Email:
CONFIDENTIAL – PROPRIETARY INFORMATION
The confidential information in this document is the property of Stemline Therapeutics, Inc. It is understood that this 
information will not be disclosed to any third party, in any form, without prior written authorization from Stemline 
Therapeutics, Inc.
Amendment 9 (Final): 30 September 2021
1
CONFIDENTIAL
NCT #: NCT02268253

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein)
Stemline Therapeutics, Inc.
Protocol STML-401-0314
Amendment 9 (Final): 30 September 2021
2
CONFIDENTIAL
INVESTIGATOR PROTOCOL AGREEMENT
Tagraxofusp (SL-401) in Patients with Chronic Myelomonocytic Leukemia 
(CMML) 
I hereby agree to:
x
Conduct the study as outlined in this protocol with reference to national/local regulations
and current International Council for Harmonisation (ICH) / Good Clinical Practice
(GCP) guidelines.
x
Discuss and agree upon any modification to the protocol with Stemline Therapeutics,
Inc., or representatives hereof.
x
Fully co-operate with monitoring and auditing and allow access to all documentation by
authorized individuals representing Stemline Therapeutics, Inc., or Health authorities.
Protocol Version (Date):
Amendment 9 (30 September 2021)
To be signed by Principal Investigator:
Print 
Name
Signature
Date
Institution
To be signed by Stemline Therapeutics, Inc.:
Print 
Name
Signature
Date
Title
	


Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
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CONFIDENTIAL 
Table of Contents 
1 
Protocol Overview .................................................................................................................................. 9 
2 
Protocol Synopsis ................................................................................................................................. 11 
3 
Abbreviations and Definitions .............................................................................................................. 18 
4 
Background Information ...................................................................................................................... 22 
4.1 
Myeloproliferative Neoplasms and Myelodysplastic Syndrome/Myeloproliferative Neoplasms22 
4.1.1 
Chronic Myelomonocytic Leukemia .......................................................................... 23 
4.2 
Targeting Cancer Stem Cells ..................................................................................................... 26 
4.3 
IL-3 Receptor (IL-5Į2YHUH[SUHVVLRQLQ+HPDWRORJLF0DOLJQDQFLHs ................................... 27 
4.4 
Tagraxofusp ............................................................................................................................... 27 
4.5 
Rationale for the Current Study ................................................................................................. 29 
5 
Design of Study .................................................................................................................................... 30 
5.1 
Description of the Type/Design of Study to be Conducted and Purpose ................................... 30 
5.2 
Data Safety Review Committee ................................................................................................. 32 
5.3 
Data Collection and Study Completion ..................................................................................... 32 
6 
Study Objectives ................................................................................................................................... 32 
6.1.1 
Stage 3A ..................................................................................................................... 32 
7 
Populations to be Studied ..................................................................................................................... 32 
7.1 
Patient Selection Criteria ........................................................................................................... 33 
7.1.1 
Inclusion Criteria ........................................................................................................ 33 
7.1.2 
Exclusion Criteria ....................................................................................................... 34 
7.2 
Replacement of Patients ............................................................................................................. 36 
8 
Treatment of Subjects ........................................................................................................................... 36 
8.1 
Tagraxofusp Description and Storage ........................................................................................ 36 
8.2 
Study Treatment Administration Schedule ................................................................................ 36 
8.2.1 
Tagraxofusp Premedication, Dose Preparation and Administration .......................... 37 
8.2.1.1 
Premedication ........................................................................................... 37 
8.2.1.2 
Tagraxofusp Dosage Preparation ............................................................. 37 
8.2.1.3 
Inpatient and Outpatient Setting for Dose Administration....................... 37 
8.2.2 
Patient Monitoring Procedures During the Tagraxofusp Dosing Period .................... 38 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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8.2.3 
Dose Delays/Modifications and Management Procedures for Toxicities Associated 
with Tagraxofusp ........................................................................................................ 39 
8.2.3.1 
Capillary Leak Syndrome and Associated Symptoms ............................. 39 
8.2.3.2 
Chills, Anaphylaxis, and Hypersensitivity Reactions .............................. 39 
8.2.3.3 
Transaminase (AST/ALT) Elevations ...................................................... 40 
8.2.3.4 
%RG\7HPSHUDWXUH 38°C ....................................................................... 40 
8.2.3.5 
Serum Creatinine > 1.8 mg/dL ................................................................. 40 
8.2.3.6 
Tachycardia, Bradycardia, or Hypertension ............................................. 40 
8.2.3.7 
Tumor Lysis Syndrome ............................................................................ 40 
8.2.3.8 
Cytokine Release Syndrome .................................................................... 40 
8.2.3.9 
Other Toxicities ........................................................................................ 41 
8.2.3.10 
Dose Modifications/Delays and Management Procedures for Other 
Toxicities Associated with Tagraxofusp .................................................. 41 
8.3 
Treatment Discontinuation ......................................................................................................... 42 
8.3.1 
Criteria for Treatment Discontinuation ...................................................................... 42 
8.3.2 
Procedures and Follow-up after Treatment Discontinuation ...................................... 43 
9 
Schedules of Events: Stage 2 ................................................................................................................ 43 
10 Schedules of Events: Stage 3A ............................................................................................................. 50 
11 Study Procedures .................................................................................................................................. 56 
11.1 Patient Selection ......................................................................................................................... 56 
11.2 Medical History ......................................................................................................................... 56 
11.3 Prior and Concomitant Medication ............................................................................................ 56 
11.4 ECOG Performance Status......................................................................................................... 56 
11.5 Physical Examination ................................................................................................................. 57 
11.6 Vital Signs .................................................................................................................................. 57 
11.7 Electrocardiograms .................................................................................................................... 57 
11.8 Imaging Studies ......................................................................................................................... 57 
11.9 Cardiac Function: MUGA/2-D Echocardiogram ....................................................................... 58 
11.10 Clinical Laboratory Tests ........................................................................................................... 58 
11.10.1 Urine or Serum Pregnancy Test ................................................................................. 58 
11.11 Vision Assessment ..................................................................................................................... 58 
11.12 Tumor Assessments ................................................................................................................... 59 

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Protocol STML-401-0314 
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11.12.2 Bone Marrow Examinations Including Biological / Target / Correlative Studies...... 60 
11.13 Immunogenicity Studies ............................................................................................................ 60 
11.14 Translational Studies/Exploratory assessments ......................................................................... 60 
12 Concomitant Medications ..................................................................................................................... 61 
12.1 Recommended Medications per Institutional Guidelines/Practices ........................................... 61 
12.2 Allowed Medications/Therapies ................................................................................................ 61 
12.3 Prohibited Medications/Therapies ............................................................................................. 62 
13 Adverse Events and Safety Evaluation ................................................................................................. 62 
13.1 Definitions .................................................................................................................................. 63 
13.1.1 
Adverse Event (AE) ................................................................................................... 63 
13.1.2 
Serious Adverse Event (SAE) .................................................................................... 64 
13.2 Period of Observation ................................................................................................................ 65 
13.3 Pre-existing Conditions .............................................................................................................. 65 
13.4 Pregnancy ................................................................................................................................... 65 
13.5 Documentation and Reporting of Adverse Events by Investigator ............................................ 66 
13.6 Assessment of Causal Relationship to Tagraxofusp .................................................................. 67 
13.7 Grading of Adverse Event Severity ........................................................................................... 68 
14 Statistical Analysis ............................................................................................................................... 69 
14.1 General Considerations .............................................................................................................. 69 
14.2 Determination of Sample Size ................................................................................................... 69 
14.2.1 
Stage 2 (Patients with CMML Previously Enrolled and Patients with MF) .............. 69 
14.2.2 
Stage 3A in Patients with CMML .............................................................................. 70 
14.3 Demographics and Baseline Characteristics .............................................................................. 71 
14.4 Analyses of Safety Data ............................................................................................................. 71 
14.5 Analyses of Efficacy Data.......................................................................................................... 72 
14.6 Pharmacokinetic and Immunogenicity Analyses ....................................................................... 72 
14.7 Blinding...................................................................................................................................... 72 
15 Emergency Procedures ......................................................................................................................... 72 
15.1 Emergency Contact .................................................................................................................... 72 
15.2 Emergency Identification of Investigational Products ............................................................... 72 
15.3 Emergency Treatment ................................................................................................................ 72 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
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CONFIDENTIAL 
16 Ethical and Regulatory Considerations ................................................................................................ 73 
16.1 Good Clinical Practice ............................................................................................................... 73 
16.2 Delegation of Investigator Responsibilities ............................................................................... 73 
16.3 Patient Information and Informed Consent ................................................................................ 73 
16.4 Confidentiality ........................................................................................................................... 74 
16.5 Protocol Amendments ................................................................................................................ 74 
16.6 IRB/EC Approval and Reporting ............................................................................................... 74 
16.7 Closure of the Study ................................................................................................................... 75 
16.8 Record Retention ....................................................................................................................... 75 
16.9 Liability and Insurance............................................................................................................... 75 
16.10 Financial Disclosure ................................................................................................................... 76 
16.11 Study Monitoring and Auditing ................................................................................................. 76 
16.12 Study Monitoring and Source Data Verification ....................................................................... 76 
16.12.1 Study Documentation ................................................................................................. 77 
16.12.2 Site Audits .................................................................................................................. 77 
16.13 Documentation and Use of Study Findings ............................................................................... 78 
16.13.1 Documentation of Study Findings .............................................................................. 78 
16.13.2 Use of Study Findings ................................................................................................ 78 
17 References ............................................................................................................................................ 80 
18 Appendices ........................................................................................................................................... 87 
18.1 Disease-specific Response Criteria ............................................................................................ 87 
18.2 ECOG Performance Status......................................................................................................... 95 
18.3 CLS Management Guidance ...................................................................................................... 96 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
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CONFIDENTIAL 
List of Tables in the Text 
Table 1: 
Dose Modifications for Other Tagraxofusp-Related Nonhematological Toxicity ................ 41 
Table 2: 
Stage 2: Schedule of Events for Screening and Cycles 1-4 ................................................... 44 
Table 3: 
Stage 2: Study Events Schedule for Cycle 5 and Beyond in Stage 2 .................................... 47 
Table 4: 
Stage 3A: Study Events Schedule for Screening and Cycles 1-4 for Patients with 
CMML ................................................................................................................................... 51 
Table 5: 
Stage 3A: Study Events Schedule for Cycle 5 and Beyond for Patients with CMML .......... 54 
Table 6: 
Stage 2: Revised IWG-MRT and ELN Response Criteria for MF ....................................... 87 
Table 7: 
Stage 2: Modified IWG Response Criteria for Altering Natural History of MDS 
(Including CMML) ................................................................................................................ 90 
Table 8: 
Stage 3A: 2015 MDS/MPN Response Criteria (Savona 2015) ............................................. 91 
Table 9 
Eastern Cooperative Oncology Group Performance Status Scale, with Equivalent 
Karnofsky Performance Status Scores .................................................................................. 95 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
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CONFIDENTIAL 
List of Figures in the Text 
Figure 1: 
Schematic of Tagraxofusp Construction ............................................................................... 28 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
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1 
Protocol Overview 
Tagraxofusp injection (Elzonris; formerly SL-401, DT388IL3), a CD123-directed cytotoxin, is a 
recombinant fusion protein comprised of human interleukin-3 (IL-3) and truncated diphtheria 
toxin (DT) that targets the alpha chain of the IL-3 receptor, or CD123 (Mani 2018). Tagraxofusp 
was granted breakthrough therapy designation for the treatment of blastic plasmacytoid dendritic 
cell neoplasm (BPDCN), a myeloid malignancy, in August 2016 and was approved by the United 
States (US) Food and Drug Administration (FDA) for the treatment of BPDCN in adults and 
pediatric patients, 2 years and older, in December 2018 (Jen 2020). 
The current study, Study STML-401-0314 (Study 0314), was initially designed as a 2-stage, 
non-randomized, open-label, multicenter study of tagraxofusp in patients with subtypes of 
advanced, high risk myeloproliferative neoplasms. The candidate patients for the study were 
comprised of: patients with chronic myelomonocytic leukemia (CMML); patients with 
myelofibrosis (MF), which includes those diagnosed with primary myelofibrosis (PMF) and 
those who transformed to MF from polycythemia vera (post-PV MF) or essential 
thrombocythemia (post-ET MF); patients with chronic eosinophilic leukaemia; and patients with 
mastocytosis (includes cutaneous mastocytosis [CM], systemic mastocytosis [SM] (comprised of 
indolent systemic mastocytosis [ISM], smoldering systemic mastocytosis [SSM], systemic 
mastocytosis with associated haematological non-mast cell disease [SM-AHNMD], aggressive 
systemic mastocytosis [ASM] mast cell leukemia [MCL]), and mast cell sarcoma). 
The primary objective of Stage 1 of this study, which is now complete, was to establish the 
maximum tolerated dose (MTD) or the maximum tested dose (MTeD) at which multiple 
dose limiting toxicities (DLTs) are not observed. In Stage 1, 9 patients (5 with CMML and 
4 with MF) received tagraxofusp at doses of 7, 9, or 12 mcg/kg via intravenous infusion on 
Days 1-3 every 21 days for Cycles 1-4, every 28 days for Cycles 5-7, and every 42 days for 
Cycles 8 and beyond. No MTD was identified, and the MTeD was 12 mcg/kg (the recommended 
phase 2 dose). As Stage 1 is complete, details regarding conduct of this stage have been removed 
from the protocol. 
Stage 2 intended to further characterize the safety profile of tagraxofusp, initially in the same 
4 candidate patient populations and then subsequently only in populations treated in Stage 1 
(CMML and MF). Preliminary assessment of clinical activity associated with tagraxofusp in 
patients with CMML or MF was also an objective of Stage 2.  Enrollment in Stage 2 is closed.  
However, both CMML and MF patients who are already enrolled may continue study 
participation in Stage 2. 
In the ongoing Stage 3a of this study, patients with CMML will receive tagraxofusp at the 
recommended phase 2 dose, 12 mcg/kg, on the same schedule as Stage 1. 
As of July 2021, 36 patients have been enrolled, comprising 20 patients with CMML-1 and 
16 with CMML-2; median age was 69 years (range 42–81), and 75% of patients were male. 
Twenty-three patients (64%) had either high- or intermediate-risk genetics based on CPSS, 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
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CONFIDENTIAL 
GFM, MMM, or ELN risk stratification systems.  Prior therapies included HMA in 16 patients 
(43%), allogeneic stem cell transplantation (allo-SCT) in 3 (8%), and other in 12 (32%); 
7 patients (19%) were high-risk and treatment naive. Overall, 16 patients (44%) had baseline 
palpable splenomegaly; in 12 of these patients, VSOHHQVL]HZDVFPEHORZOHIWFRVWDOPDUJLQ
Overall, 4 of 36 (11%) patients achieved bone marrow morphological complete responses 
(BMCRs), 1 of whom was bridged to allo-SCT; all 4 patients had splenomegaly at baseline. It is 
noteworthy that 2 of the 4 BMCRs, were observed in patients with high-risk genetic features. 
Fifteen patients (42%) with baseline splenomegaly had spleen responses; 9 patients (60%) had a 
UHGXFWLRQLQVSOHHQVL]HLQFOXGLQJZLWKVSOHQRPHJDO\RIFPDWEDVHOLQH 
Based on these preliminary results and increasing scientific and clinical knowledge on CMML, 
the protocol has been amended to add Stage 3A in patients with CMML. The Myelodysplastic 
Syndrome/ Myeloproliferative Neoplasm (MDS/MPN) 2015 criteria (Savona 2015) represent the 
current consensus criteria for evaluation of clinical benefit in patients with MDS/MPN, beyond 
those specified in the IWG response criteria for MDS (Cheson 2006), however, these criteria are 
not specific to CMML. Thus, in Stage 3A, the endpoints indicated in the MDS/MPN 2015 
criteria will be individually evaluated to enable a prospective definition of a primary efficacy 
endpoint, specifically in CMML, that will provide the primary evidence of efficacy for 
regulatory decision-making.  The hematology community has recognized that a lack of a stable 
disease (SD) category in the 2015 MDS/MPN IWG criteria creates considerable uncertainty in 
the categorization of patients on any CMML study.  Therefore, a SD category, defined as those 
patients not belonging to any of the defined categories in the 2015 criteria, has been added as a 
response category. 
Stage 3A will enroll 2 populations of patients with CMML, previously untreated patients who 
are not expected to benefit from HMAs (previously untreated patients; approximately 
20 patients) and patients who are primary or secondary failures to first-line therapy (first-line 
failure patients; approximately 20 patients), as defined in the inclusion criteria for Stage 3A 
(Section 7.1.1). In addition, central analysis of CD123 expression will be performed by flow 
cytometry and immunohistochemistry to evaluate the presence of CD123 expressing cells and 
the relationship between CD123 expression and clinical response.  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
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CONFIDENTIAL 
2 
Protocol Synopsis 
Name of Finished Product: 
Elzonris (tagraxofusp-erzs) Injection solution (1mg/ml) / Tagraxofusp for Injection lyophilized powder for solution 
(1 mg/vial) 
Name of Active Ingredient: 
Tagraxofusp (SL-401) 
Study Title: 
Tagraxofusp in Patients with Chronic Myelomonocytic Leukemia (CMML)  
Study Number: 
STML-401-0314 
Study Phase: 
2 
Protocol Overview: 
The current study was initially designed as a 2-stage, non-randomized, open-label, multicenter study of tagraxofusp 
in patients with subtypes of advanced, high risk myeloproliferative neoplasms. The candidate patients for the study 
were comprised of patients with CMML, MF, chronic eosinophilic leukemia, or mastocytosis. 
The primary objective of Stage 1 of this study, which is now complete, was to establish the maximum tolerated dose 
(MTD) or the maximum tested dose (MTeD) at which multiple dose-limiting toxicities (DLTs) were not observed. 
In Stage 1, 9 patients (5 with CMML and 4 with MF) received tagraxofusp at doses of 7, 9, or 12 mcg/kg via 
intravenous (IV) infusion on Days 1-3 every 21 days for Cycles 1-4, every 28 days for Cycles 5-7, and every 
42 days for Cycles 8 and beyond. No MTD was identified, and the MTeD was 12 mcg/kg (the recommended phase 
2 dose). As Stage 1 is complete, details regarding conduct of this stage have been removed from the protocol. 
Stage 2 intended to further characterize the safety profile of tagraxofusp, initially in the same 4 candidate patient 
populations and then subsequently only in populations treated in Stage 1, CMML and MF. Preliminary assessment 
of clinical activity associated with tagraxofusp in patients with CMML or MF was also an objective of Stage 2.  As 
Stage 2 is complete, study details regarding the conduct of this stage have been removed. 
Ongoing CMML and MF patients enrolled during Stage 2 will receive tagraxofusp at the recommended phase 2 
dose, 12 mcg/kg, on the same schedule as Stage 1. 
As of July 2021, 36 patients have been enrolled, comprising 20 patients with CMML-1 and 16 with CMML-2; 
median age was 69 years (range 42–81) and 75% were male. Twenty-three (64%) patients had either high-or 
intermediate-risk genetics based on CPSS, GFM, MMM, or ELN risk stratification systems.  Prior therapies 
included HMA in 16 patients (43%), allogeneic stem cell transplantation (allo-SCT) in 3 (8%), and other in 
12 (32%); 7 patients (19%) were high-risk and treatment naive. Overall, 16 patients (44%) had baseline palpable 
splenomegaly; in 12 of these patients, VSOHHQVL]HZDVFPEHORZOHIWFRVWDOPDUJLQ2YHUDOORI
patients achieved bone marrow morphological complete responses (BMCRs), 1 of whom was bridged to allo-SCT; 
all 4 patients had splenomegaly at baseline. Notably, 2 of the 4 BMCRs were observed in patients with high-risk 
genetic features. Fifteen patients (42%) with baseline splenomegaly had spleen responses; 9 patients (60%) had a 
UHGXFWLRQLQVSOHHQVL]HLQFOXGLQJZLWKVSOHQRPHJDO\RIFPDWEDVHOLQH 
Based on these preliminary results and increasing scientific and clinical knowledge on CMML, the protocol has 
been amended to add Stage 3A in patients with CMML. The Myelodysplastic Syndrome/ Myeloproliferative 
Neoplasm (MDS/MPN) 2015 criteria (Savona 2015) represent the current consensus criteria for evaluation of 
clinical benefit in patients with MDS/MPN, beyond those specified in the International Working Group (IWG) 
response criteria in MDS (Cheson 2006), however, these criteria are not specific to CMML. Thus, in Stage 3A, the 
endpoints indicated in the MDS/MPN 2015 criteria will be individually evaluated to enable a prospective definition 
of a primary efficacy endpoint, specifically in CMML, that will provide the primary evidence of efficacy for 
regulatory decision-making.  The hematology community has recognized that a lack of a stable disease (SD) 
category in the 2015 MDS/MPN IWG criteria creates considerable uncertainty in the categorization of patients on 
any CMML study.  Therefore, a SD category, defined as those patients not belonging to any of the defined 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
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CONFIDENTIAL 
categories in the 2015 criteria, has been added as a response category. 
Stage 3A will enroll 2 populations of patients with CMML, previously untreated patients who are not expected to 
benefit from HMAs (previously untreated patients; approximately 20 patients) and patients who are primary or 
secondary failures to first-line therapy (first-line failure patients; approximately 20 patients), as defined in the 
inclusion criteria for Stage 3A (Section 7.1.1). Enrollment in Stage 2 is closed; however, patients with CMML and 
MF who are already enrolled may continue study participation in Stage 2. 
Study Population: 
Stage 3A will include patients with CMML as follows: 
x 
Patients with 2016 WHO-defined CMML, including those with  
- 
CMML-1 or CMML-2 who are refractory/resistant/intolerant to HMAs, or hydroxyurea (HU), or 
intensive chemotherapy; and  
- 
Treatment naïve CMML-1 or CMML-2 with molecular features associated with a poor prognosis.  
Study Design: 
This is a non-randomized, open-label, multicenter study divided into multiple stages.  
Stage 3A (CMML): 
Stage 3A is a 2-arm, non-randomized, open-label multicenter study stage in patients with CMML intended to 
identify clinically important responses that connote clinical benefit and potential endpoints to inform the design of a 
pivotal Stage 3B in patients with CMML (to be added under the auspices of a separate amendment), as well as 
gather data on the expression of CD123 on dendritic cells and monocytes in CMML. Additionally, monocyte subsets 
will be enumerated by flow cytometry.  
In Stage 3A, patients will be administered tagraxofusp at a dose of 12 mcg/kg as a 15-minute IV infusion once daily 
on days 1 to 3 of a 21-day cycle (C1 to C4) and then on days 1 to 3 of a 28-day cycle (C5 and beyond). The dosing 
period may be extended for dose delays up to D10 of each cycle.  
Study Centers: 
The study will be conducted at approximately 30 study centers in North America and Europe. 
Inclusion Criteria: 
Patients meeting all of the following criteria may be considered for enrollment: 
Objectives: 
Stage 3A: Objectives of Stage 3a in patients with CMML are: 
x 
To characterize the safety profile of tagraxofusp.  
x 
To obtain preliminary evidence of response to tagraxofusp therapy as assessed by the MDS/MPN 2015 
criteria (Savona 2015), with the addition of a stable disease category, and to obtain data relative to 
additional clinical parameters that may be used in determination of therapeutic benefit. 
The MDS/MPN 2015 criteria (Savona 2015) represent the current consensus criteria for evaluation of clinical 
benefit in patients with CMML, beyond those specified in the IWG-MDS 2006 criteria. Thus, as an inherent 
component of the design of Stage 3A, responses to treatment are assessed using the MDS/MPN 2015 criteria.  
The purpose of Stage 3A is to evaluate the clinical benefit derived from individual components, or variations 
thereof, of the MDS/MPN 2015 criteria that may allow for a prospective definition of a primary efficacy endpoint, 
that will provide the primary evidence of efficacy for regulatory decision-making in the planned confirmatory cohort 
(Stage 3B; to be added under the auspices of a separate amendment).  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
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CONFIDENTIAL 
1. The patient is  18 years old. 
2. The patient has a life expectancy of > 6 months. 
3. The patient has an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-2. 
4. The patient has adequate baseline organ function, including cardiac, renal, and hepatic function: 
x 
/HIWYHQWULFXODUHMHFWLRQIUDFWLRQ/9() institutional lower limit of normal as measured by 
multigated acquisition scan (MUGA) or 2-dimensional (2-D) echocardiogram (ECHO) within 
28 days prior to start of therapy and no clinically significant abnormalities on a 12-lead 
electrocardiogram (ECG). 
x 
6HUXPFUHDWLQLQH 1.5 mg/dL. 
x 
6HUXPDOEXPLQ JG/RU 32 g/L) in the absence of receipt of IV albumin within the 
previous 72 hours. 
x 
%LOLUXELQ 1.5 mg/dL. 
x 
Aspartate transaminase (AST) and alanine transaminasH$/7 2.5 times the upper limit of 
normal (ULN). 
x 
&UHDWLQHSKRVSKRNLQDVH&3. 2.5 times the ULN. 
x 
Absolute neutrophil count (ANC)  0.5×109/L. 
5. 
If a woman of child-bearing potential (WOCBP), the patient has a negative serum or urine pregnancy test 
within 1 week prior to tagraxofusp treatment (intervals shorter than 1 week are acceptable, if required by 
institutional guidelines). 
6. 
The patient (either male or female) agrees to use acceptable contraceptive methods for the duration of 
time in the study, and to continue to use acceptable contraceptive methods for 1 week after the last 
tagraxofusp infusion. 
7. 
The patient has signed informed consent prior to initiation of any study-specific procedures or treatment. 
8. 
The patient is able to adhere to the study visit schedule and other protocol requirements, including 
follow-up for response assessments. 
9. 
Patient has a 2016 WHO-defined diagnosis of CMML SHUVLVWHQWPRQRF\WRVLV 1×109/L for at least 
3 PRQWKVZLWKRWKHUFDXVHVH[FOXGHGDQGPRQRF\WHV 10% of WBC in peripheral blood, no criteria and 
no previous history of chronic myeloid leukemia (CML), essential thrombocythemia (ET), polycythemia 
vera (PV), and acute promyelocytic leukemia; if eosinophilic, neither PDGFRA, PDGFRB, FGFR1 
rearrangements nor PCM1-JAK2 translocation; < 20% blasts in peripheral blood and bone marrow 
aspirate; > 1 following criteria: dysplasia in > 1 myeloid lineage, acquired clonal cytogenetic or 
molecular abnormality in hematopoietic cells). 
10. 
 Patient has 2016 WHO-defined CMML-1 (2-4% blasts in peripheral blood and/or 5-9% blasts in bone 
marrow) and CMML-2 (5-19% blasts in peripheral blood and/or 10-19% blasts in bone marrow, and/or 
presence of Auer rods) (Arber 2016). 
11. 
Patient is refractory/resistant/intolerant, as defined for the purposes of this study (in the absence of a 
standard definition for CMML) below, to HMAs, or HU, or intensive chemotherapy, including: 
x 
Resistance/intolerance to HU is defined as: 
- Uncontrolled myeloproliferation (platelets >400 x 109/L and WBC >10 x 109/L after 3 months 
of at least 2 g/day of HU); or 
- Myelosuppression at a clinically relevant dose; or 
- Presence of unacceptable HU-related non-hematological toxicities, such as mucocutaneous 

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manifestations, gastrointestinal symptoms, pneumonitis or fever at any dose of HU. 
x 
Conventional definition for HMA failure is defined for the purposes of this study (in the 
absence of a standard definition for CMML) as: 
- Disease progression following at least 4 to 6 cycles of 5-azacitidine or decitabine; or 
- Relapse after achieving response; or 
- Intolerance to 5-azacitidine or decitabine at the prescribed dose. 
OR 
x 
Patient is classified as high-risk based on the presence of morphological features, as described by 
the 2016 WHO prognostic system (Arber 2016), and the clinical and molecular features described 
in molecularly-integrated prognostic systems, such as the Group Français des Myélodysplasies 
(GFM), Mayo Molecular Model (MMM), and the CMML-specific prognostic model (CPSS-Mol) 
(Woo 2020) and thus is not expected to benefit from HMAs.  
12. Patient is ineligible for an immediate allo-SCT. 

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Investigational Product, Dose, and Mode of Administration: 
Tagraxofusp Injection is a biologic fusion protein comprised of recombinant human interleukin-3 (IL-3) genetically 
fused to truncated diphtheria toxin (DT) protein. Tagraxofusp targets the IL-3 receptor (IL-3R), which is 
overexpressed on the cancer stem cells (CSC) and bulk of various leukemias and hematopoietic malignancies 
relative to normal hematopoietic stem cells and other hematopoietic cells.  
Tagraxofusp is prepared in liquid or lyophilized formulations; study sites may be provided with either of the 
following:  
x 
Tagraxofusp Injection is a preservative-free, sterile, clear, colorless solution supplied in single-dose glass 
vials containing 1 mL of sterile tagraxofusp solution (1 mg/vial) that should be stored in a freezer between -
25°C and -15°C (-13°F and 5°F).   
x 
Tagraxofusp for Injection (lyophilized powder), 1.0 mg is supplied in single-use, sterile, 2 mL glass vials 
packaged in labeled, single-vial cartons (study drug) and should be stored between 2°C and 8°C (36°F – 
46°F). 
Patients will receive 12 mcg/kg of tagraxofusp by IV infusion once daily for 3 consecutive days (or 3 doses over a 
period not to exceed 10 days if postponement is required to allow for toxicity resolution) of a cycle in the absence of 
progressive disease (PD) or other withdrawal criteria.  
A treatment cycle is 21 days in C1-4 and 28 days in C5 and beyond. 
The total per-patient dose is calculated based on patient body weight in kg at baseline (C1D1). This dose will be 
recalculated if there is a 10% or greater change from baseline in body weight. 
The first cycle of tagraxofusp must be administered in the inpatient setting, with hospitalization beginning the day of 
the first infusion of tagraxofusp (or a prior day) and ending approximately 24 hours after the last infusion of 
tagraxofusp. Subsequent cycles of tagraxofusp can be administered in the inpatient setting or in a suitable outpatient 
ambulatory care setting that is equipped for intensive monitoring of patients with hematopoietic malignancies 
undergoing treatment, per the Investigator’s discretion, institutional guidelines and capabilities. Patients will be 
monitored for at least 1 hour (or longer at the Investigator’s discretion) following the administration of each infusion 
of tagraxofusp in Cycle 2 and beyond. 
Patients with evidence of ongoing disease control during treatment (without evidence of clinically significant PD or 
intolerable toxicity) may receive repeated cycles of tagraxofusp even if an overall response, in the judgment of the 
Investigator, is not attained. 
Patients will receive the following pre-medications 60 minutes (㼼15 minutes) before each tagraxofusp infusion: 
x 
Acetaminophen 650 mg by mouth (PO) (or equivalent dose of paracetamol)  
x 
Diphenhydramine 50 mg IV (or an equivalent dose of another H1-histamine antagonist) 
x 
Methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid) 
x 
Famotidine 20 mg IV (or an equivalent dosage of another H2-histamine antagonist) 
During the dosing period for each cycle, individual tagraxofusp infusions may be delayed to allow for toxicity 
resolution, as detailed in Protocol Section 8.2.3. 

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Concomitant Medications: 
Recommended Medications Per Institutional Guidelines/Practices: 
The following types of prophylactic therapies/regimens may be administered, if indicated per institutional 
guidelines/practices or warranted for clinical management:  
x 
Antibacterial: ciprofloxacin, levofloxacin, or an equivalent antibiotic. 
x 
Antifungal: fluconazole, voriconazole, or an equivalent antifungal. 
x 
Antiviral: acyclovir, valacyclovir, or an equivalent antiviral.  
Allowed Medications/Therapies: 
All patients may receive supportive care measures as clinically indicated, including prophylactic antibiotics, 
antihistamines, antiemetics, albumin, fluids (hydration), and supportive measures. Patients may receive growth 
factor support and/or blood product transfusions as per the discretion of their physician. 
Albumin 25 g IV daily should be administered if serum albumin is < 3.0 g/dL during days when treatment is 
withheld or in the immediate post-treatment period. (Refer to Appendix Section 18.3 for albumin administration 
requirements in the setting of elements of capillary leak syndrome (CLS).) 
Corticosteroid therapy is permitted and is governed by parameters detailed in Section 12.3 (Prohibited 
Medications/Therapies).  
Granulocyte-colony stimulating factor (G-CSF) is permitted only for the treatment of febrile neutropenia. Following 
a febrile neutropenic event, G-CSF prophylaxis may be considered if there is evidence of response and the 
Investigator determines that ongoing tagraxofusp treatment is associated with a potentially favorable risk-benefit 
profile (such a determination should be made in consultation with the Medical Monitor). 
Prohibited Medications/Therapies: 
Prior to discontinuation of tagraxofusp, patients may not receive the following anticancer/ antimyeloproliferative 
agents: JAK inhibitors (ruxolitinib, fedratinib, and others), interferon-Į, thalidomide, lenalidomide, cytotoxic 
chemotherapy agents (including 2-chlorodeoxyadenosine and other purine analogs), hypomethylating agents (5-aza, 
decitabine and others), tyrosine kinase inhibitors (including those which inhibit the BCR-ABL kinase such as 
imatinib), hydroxyurea (HU), and investigational anti-cancer agents. 
Patients may not receive additional disease-modifying or cytoreductive agents such as danazol or anagrelide. 
Patients may not receive erythroid- or platelet-stimulating growth factors.  
Hydroxyurea is prohibited during study participation except for cycle 1; short-term treatment with HU beyond cycle 
1 with approval of the Medical Monitor is permitted.  
Ongoing corticosteroid therapy at doses of > 20 mg/day prednisone (or equivalent) for > 7 days is not permitted; 
however transient increases in corticosteroid doses in the setting of infections or other “stress” settings are allowed. 
Assessments: 
Assessments for safety, efficacy, and biological/correlative effects will be performed according to the schedules 
outlined in Section 9 (Stage 2) and Section 10 (Stage 3A). 
Safety Assessments: 
Safety will be assessed throughout the duration of the study; safety assessments will include physical examinations, 
vital sign measurements, clinical laboratory evaluations, and adverse event (AE) reporting. Blood samples for 
immunogenicity assessments will be collected. 
Efficacy Assessments: 
Efficacy assessments will include bone marrow (aspirate and biopsy), peripheral blood (complete blood count 
[CBC] and differential with percent monocytes, neutrophils, neutrophil precursors, immature myeloid cells, and 
blasts), hepatosplenomegaly by MRI or CT, other extramedullary disease (e.g., cutaneous disease, disease-related 

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serous effusions), symptom score analysis by the Myeloproliferative Neoplasm Symptom Assessment Form Total 
Symptom Score (MPN-SAF TSS), cytogenetic burden, molecular response, reduced dependence on transfusion, 
reduced risk of infection, and survival status. Refer to Appendix Section 18.1 for detailed response criteria 
established for CMML. 
Biological/Target/Correlative Studies: 
Plasmacytoid dendritic cells (pDCs) and CD123 expression will be assessed centrally on all bone marrow and 
peripheral blood samples by flow cytometry and immunohistochemistry prior to the start of and during treatment. 
Additionally, various monocyte subsets will be monitored in CMML. 
Exploratory assessments for CMML patients will include peripheral blood for the evaluation of cytokine IL-10, 
CD14+/CD16-, CYTOF (Mass cytometry), and next generation sequencing (NGS) at selected sites prior to the start 
of and during treatment. 
Immunogenicity Studies: 
Blood samples will be collected for the detection of tagraxofusp reactive antibodies. 
Statistical Methods:  
Analyses will be performed on all patients that received any quantity of tagraxofusp (i.e., all treated patients). The 
baseline value for a given variable is defined as the last measurement for the variable prior to the first infusion of 
tagraxofusp. Day 1 for each individual patient is defined as the date the patient receives their first infusion of 
tagraxofusp. 
Safety assessments include DLTs, AEs, serious adverse events (SAEs), physical examinations, vital sign 
measurements, ECGs, clinical laboratory evaluations, and reasons for treatment discontinuation due to toxicity. 
Treatment-emergent AEs through 30 days after the last tagraxofusp infusion will be summarized by Medical 
Dictionary for Regulatory Activities (MedDRA™) Version 13.1 (or higher) System Organ Class and preferred term. 
The incidences and percentages of patients experiencing each AE preferred term will be summarized with 
descriptive statistics. AEs will also be summarized by National Cancer Institute Common Terminology Criteria for 
Adverse Events (NCI CTCAE), Version 4.03 (or higher), grade and by causality (relationship to study drug). DLTs, 
Grade 3-4 AEs, SAEs, and AEs resulting in dose modification or treatment discontinuation will also be summarized 
by preferred term.  
Laboratory results will be classified according to NCI CTCAE, Version 4.03. Laboratory results not corresponding 
to an NCI CTCAE term will not be graded. Incidences of laboratory abnormalities will be summarized with 
descriptive statistics. 
Vital signs, physical examination results, and ECGs will be summarized with descriptive statistics. 
Efficacy assessments include objective response rate (ORR), complete response (CR) rate, specific components of 
the response criteria for each indication, duration of response (DOR), progression-free survival (PFS), and overall 
survival (OS). All efficacy outcomes will be presented by subgroups defined by disease. Data from Stage 2 will be 
analyzed with descriptive statistical methods to provide estimates of rates of response. Stage 3A data will be 
analyzed with descriptive and correlation methods, with results intended to assist in the design of the confirmatory 
Stage 3B. Bayesian methods may also be used to determine likely values of response parameters, with Stage 2 
results providing prior information for calculation of credible intervals based on Stage 3A data. Complete details of 
efficacy analyses will be provided in the Statistical Analysis Plan (SAP). 
 

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3 
Abbreviations and Definitions 
Abbreviation 
Definition 
2-D 
2-Dimensional 
AE 
Adverse Event 
ALL 
Acute Lymphoid Leukemia 
allo-SCT 
Allogeneic Stem Cell Transplantation 
ALP 
Alkaline Phosphatase 
ALT 
Alanine Transaminase 
AML 
Acute Myeloid Leukemia 
ANC 
Absolute Neutrophil Count 
aPTT 
Activated Partial Thromboplastin Time 
AST 
Aspartate Transaminase 
BP 
Blood Pressure 
BPDCN 
Blastic Plasmacytoid Dendritic Cell Neoplasm 
BUN 
Blood Urea Nitrogen 
C 
Cycle 
CBC 
Complete Blood Count 
CEL 
Chronic Eosinophilic Leukemia 
CFR 
Code of Federal Regulations 
CI 
Clinical Improvement 
CLS 
Capillary Leak Syndrome 
CML 
Chronic Myeloid Leukemia 
CMML 
Chronic Myelomonocytic Leukemia  
CNL 
Chronic Neutrophilic Leukemia 
CNS 
Central Nervous System 
CPK 
Creatine Phosphokinase 
CR 
Complete Response / Remission 
CSC 
Cancer Stem Cell 
CT 
Computed Tomography 
CTCAE 
Common Terminology Criteria for Adverse Events 
DLT 
Dose-Limiting Toxicity 
DNA 
Deoxyribonucleic Acid 
DOR 
Duration of Response 
DSRC 
Data Safety Review Committee 
DT 
Diphtheria Toxin 

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Abbreviation 
Definition 
DT388IL3 
Diphtheria Toxin Interleukin-3 Fusion Protein 
EC 
Ethics Committee 
ECG 
Electrocardiogram 
ECHO 
Echocardiogram 
ECOG 
Eastern Cooperative Oncology Group 
eCRF 
Electronic Case Report Form 
EHA 
European Hematology Association 
ELISA 
Enzyme-linked Immunosorbent Assay 
ELN 
European LeukemiaNet 
EMA 
European Medicines Agency 
EMH 
Extramedullary Hematopoiesis 
ET 
Essential Thrombocythemia 
FDA 
Food and Drug Administration 
FGFR 
Fibroblast Growth Factor Receptor 
FISH 
Fluorescence In Situ Hybridization 
GCP 
Good Clinical Practice 
G-CSF 
Granulocyte-colony Stimulating Factor 
GM-CSF 
Granulocyte Macrophage-colony Stimulating Factor 
GVHD 
Graft Versus Host Disease 
Hb 
Hemoglobin 
HIPAA 
Health Insurance Portability and Accountability Act 
HIV 
Human Immunodeficiency Virus 
HMA 
Hypomethylating agent 
HSC 
Hematopoietic Stem Cell 
HU 
Hydroxyurea 
ICF 
Informed Consent Form 
ICH 
International Council for Harmonisation 
IL-3 
Interleukin-3 
IL-3R 
Interleukin-3 Receptor 
IL-5Į 
Alpha Subunit of the Human Interleukin-3 Receptor 
INR 
International Normalized Ratio 
IRB 
Institutional Review Board 
IV 
Intravenous 
IWG 
International Working Group 
IWG-MRT 
International Working Group-Myeloproliferative Neoplasms Research 

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Abbreviation 
Definition 
and Treatment  
JAK 
Janus Kinase 
JAKi 
JAK inhibitor 
JMML 
Juvenile Myelomonocytic Leukemia 
LDH 
Lactate Dehydrogenase 
LVEF 
Left Ventricular Ejection Fraction 
MCL 
Mast Cell Lymphoma 
MDS 
Myelodysplastic Syndrome 
MedDRA™ 
Medical Dictionary for Regulatory Activities 
MF 
Myelofibrosis 
MPD 
Myeloproliferative Disorder 
MPN 
Myeloproliferative Neoplasm 
MPN-SAF TSS 
Myeloproliferative Neoplasm Symptom Assessment Form Total 
Symptom Score 
MPN-U 
Myeloproliferative Neoplasm, Unclassifiable 
MRI 
Magnetic Resonance Imaging 
MTD 
Maximum Tolerated Dose 
MTeD 
Maximum Tested Dose 
MUGA 
Multigated Acquisition Scan 
NCI 
National Cancer Institute 
ORR 
Objective Response Rate 
OS 
Overall Survival 
PB 
Peripheral Blood 
PD 
Progressive Disease 
pDC 
Plasmacytoid Dendritic Cell 
PDGFRD 
Platelet-derived Growth Factor Receptor-alpha 
PDGFRE 
Platelet-derived Growth Factor Receptor-beta 
pET 
Post-essential Thrombocythemia  
PFS 
Progression-free Survival 
PK 
Pharmacokinetics 
PMF 
Primary Myelofibrosis 
PR 
Partial Response / Remission 
pRBC 
Packed Red Blood Cell 
PS 
Performance status 
PT 
Prothrombin Time 

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Abbreviation 
Definition 
PV 
Polycythemia Vera 
R/R 
Relapsed/Refractory 
RBC 
Red Blood Cell 
RS 
Ring Sideroblasts 
SAE 
Serious Adverse Event 
SAP 
Statistical Analysis Plan 
SM 
Systemic Mastocytosis 
SM-AHNMD 
Systemic Mastocytosis with Associated Haematological Non-Mast Cell 
Disease 
SSM 
Smoldering Systemic Mastocytosis 
TEAE 
Treatment-emergent Adverse Event 
TLS 
Tumor Lysis Syndrome 
ULN 
Upper Limit of Normal 
US 
United States 
WBC 
White Blood Cell 
WHO 
World Health Organization 
WOCBP 
Woman of Childbearing Potential 
 

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4 
Background Information 
4.1 
Myeloproliferative Neoplasms and Myelodysplastic Syndrome/Myeloproliferative 
Neoplasms 
In 2008, World Health Organization (WHO)-appointed experts replaced the historical term 
‘myeloproliferative disorders’ (MPD) with the term ‘myeloproliferative neoplasm’ (MPN) in 
alignment with the enhanced knowledge about the molecular biology of these diseases. The 2016 
edition of the WHO-classification recognizes MPNs to comprise of several subtypes: chronic 
myeloid leukemia (CML), polycythaemia vera (PV), essential thrombocythemia (ET), primary 
myelofibrosis (PMF) and several ‘atypical’ subtypes, which include chronic neutrophilic 
leukaemia (CNL), chronic eosinophilic leukemia, not otherwise specified (CEL), and 
myeloproliferative neoplasm, unclassifiable (MPN-U). The various MPN subtypes have 
traditionally been distinguished from one another by clinicopathological features and, in some 
cases, the disease-defining genetic aberrations. In clinical practice, since most patients present 
with neutrophilia, it is important to establish the presence or absence of BCR-ABL1 
rearrangement, which defines CML.  
The BCR-ABL1-negative MPNs are a group of clonal myeloid malignancies characterized by 
excessive accumulation of one or more myeloid cell lineages and an inherent ability to transform 
to acute myeloid leukemia (AML). In tandem with the 2016 WHO edition, revised diagnostic 
criteria for the various subtypes were also developed to enable better diagnostic work-up and 
help distinguish MPN from secondary/reactive erythrocytosis or thrombocytosis in challenging 
cases.  
An important tenet of the 2016 WHO-classification is that in myelodysplastic syndrome 
(MDS)/MPN, the dysplastic and proliferative features must be present at the time of initial 
diagnosis, with the sole exception of MDS/MPN with ring sideroblasts (RS) and thrombocytosis. 
Patients with other subtypes, including chronic myelomonocytic leukemia (CMML), may present 
in earlier phases in which the full disease phenotype has not fully developed. Indeed, a recent 
publication has proposed broadening the category of CMML to encompass variants in which 
monocytosis develops after a prior diagnosis of a myeloid malignancy, a category which is not 
included in the 2016 WHO classification (Valent 2019). The MDS/MPN subtypes are typically 
identified by the type of myeloid subset that predominates in the peripheral blood (PB). For 
example, CMML and juvenile myelomonocytic leukemia (JMML) are characterized by a unique 
expansion of peripheral blood monocytes, while atypical CML is associated with highly 
dysplastic granulocyte predominance. Multiparameter flow cytometry helps to characterize 
patients with CMML who have a specific expansion of ‘classical’ monocytes (CD14hi/CD16neg), 
albeit with varying degrees of differentiation and proliferation which, in turn, result in the 
remarkable clinical heterogeneity, in contrast to the genetic landscape, which is relatively 
homogeneous with four well defined mutations (ASXL1, NRAS, RUNX1, and SETBP1) which 
exert a prognostic impact on the patients. Patients with MDS/MPNs often present with 

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neutrophilia and have clinical features consistent with features of ineffective hematopoiesis 
(anemia, infections, bleeding), constitutional symptoms and splenomegaly associated with 
myeloproliferation.  
A recent study (Zhang 2019) suggests that once CML, JMML, and the JAK2/MPL/CALR-
associated MPNs are excluded, many of the chronic myeloid malignancies appear to share 
genetic and epigenetic features and it is possible that they should be considered collectively for 
risk stratification, treatment, and clinical studies. 
4.1.1 
Chronic Myelomonocytic Leukemia 
The annual incidence of CMML is estimated at 1,100 cases per year in the United States (US), 
with a median age of 70 years and a male predominance. The diagnosis of CMML is based upon 
laboratory, morphological and clinical parameters. Recurrent somatic mutations are noted in 
> 90% of the patients and clonal cytogenetic abnormalities in > 30%. A cardinal feature of 
CMML is the PB monocytosis (> 1×109/L), with monocytes accounting for > 10% of white 
blood cells (WBC). Clinical presentation includes dysplastic features such as cytopenias and 
excess of blasts, or proliferative features such as high WBC count ( 13×109/L) and 
splenomegaly; rarely skin and lymph node infiltration and serous membrane effusions can occur.  
CMML is divided by the 2016 WHO diagnostic criteria into three groups based upon blast 
percentage:  
x CMML-0 with < 2% blasts in PB and < 5% blasts in the bone marrow, 
x CMML-1 with 2% to 4% blasts in PB and/or 5% to 9% blasts in bone marrow and 
x CMML-2 with 5% to 19% blasts in PB and/or 10% to 19% in bone marrow, and/or 
presence of Auer rods.  
The so-called ‘proliferative type’ CMML (leukocyte count  13×109/L) and ‘dysplastic type’ 
CMML (< 13×109/L) are distinguished solely by leukocyte count; however, mutational patterns 
may help to distinguish between the two types. For example, mutations involving the 
JAK2/RAS/MAPK signaling pathways tend to be more common in patients with the 
‘proliferative type’ CMML.  
Cytogenetic abnormalities include trisomy 8, monosomy 7, del(7q) and rearrangements with a 
12p breakpoint; however, del(5q) is almost never found. As previously mentioned, PB 
monocytosis with monocytes accounting for > 10% of WBCs is the hallmark of CMML. 
Morphologically, these monocytes demonstrate an abnormal appearance with bizarre nuclei and 
cytoplasmic granules. In some patients, blood cells identified as monocytes are later recognized 
to be dysplastic and immature granulocytes endowed with immunosuppressive properties, i.e. so-
called para- myeloid cells. Islands of CD123high cells have been commonly described in the bone 
marrow of patients with CMML (Niyongere 2019). Using a multiparameter flow cytometry 
assay, an excess of CD123+ mononucleated cells that are lineage-negative, CD45+, CD11c-, 
CD33-, HLA-DR+, BDCA-2+, BDCA-4+ in the bone marrow of 32/159 (20%) patients were 

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detected in a recent study and characterized as plasmacytoid dendritic cells (pDCs) (Lucas 2019). 
Furthermore, an excess of pDCs correlates with regulatory T cell accumulation and an increased 
risk of acute leukemia transformation. These results demonstrate the FLT3-independent 
accumulation of clonal pDCs in the bone marrow of CMML patients with mutations affecting the 
RAS pathway, which is associated with a higher risk of progressive disease (PD).  
Multiple prognostic scoring systems, based on monocyte counts, genetic lesions, clinical features 
and risk to transform to AML have been proposed and validated (Itzykson 2018). As illustration, 
Itzykson et al proposed a prognostic score based on ASXL1 mutations, age, hemoglobin, WBC, 
and platelet counts that defined three prognostic groups with varied overall survival (OS) 
(Itzykson 2013). 
Splenomegaly is a major source of morbidity in approximately 30%-50% of patients with 
CMML and is associated with abdominal discomfort, left subcostal pain and early satiety, as well 
as serious risk of splenic rupture and splenectomy sequelae (Padron 2014, Pophali 2018). The 
effectiveness of splenectomy in alleviating many of the symptoms of CMML was demonstrated 
in a study of patients with CMML where splenectomy was medically necessary. In this study, 
85% of patients who underwent a splenectomy achieved durable resolution of symptoms. 
However, splenectomy was also associated with perioperative morbidity and mortality rates of 
43% and 13%, respectively (Pophali 2018). 
The management of patients with CMML is often a challenge with a small subset of patients 
having an indolent course with median survival in excess of 10 years, whilst others progress 
rapidly to AML. Allogeneic stem cell transplantation (allo-SCT) remains the only treatment 
modality associated with long term remissions and long-term OS benefit (10-year OS rate of 
40%). Factors associated with favorable outcomes appear to be CMML risk group (CMML-0 vs. 
CMML-1 vs. CMML-2), pre-transplant hematocrit, cytogenetic risk category, co-morbidity 
index, and age (Germing 2004). Splenomegaly at the time of allo-SCT was reported to be 
associated with poorer OS post-transplant (Park 2013). 
At present, there are no satisfactory non-transplant treatment options, and the only US FDA-
approved therapies are two hypomethylating agents (HMAs), azacitidine and decitabine. While 
these agents may transiently improve cytopenias in patient with CMML with dysplastic features, 
treatment outcomes are less favorable in patients with CMML with proliferative features (Padron 
2014, Padron 2016, Pardanani 2019). Azacitidine was approved in 2004 for the treatment of 
patients with several MDS subtypes, including CMML. In the pivotal study, the objective 
response rate (ORR) for the entire MDS population (N=89) was 16% and in the 2 supportive 
studies (N=72 and N=48) was 14% and 19%, respectively. The ORR for the CMML 
subpopulation (n=19; approximately 8-9% of enrolled MDS patients) ranged between 11% and 
20%. Decitabine was approved in 2006 for the treatment of patients with all MDS subtypes, 
including CMML. In the pivotal study, the ORR for the entire MDS population (N=89) was 17% 
and in the 2 supportive studies (N=66 and N=98) was 26% and 24%, respectively. The ORR for 
the CMML subpopulation (n=28; approximately 10-11% of enrolled MDS patients) ranged 

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between 17% and 27% across the three studies. In a 2010 update to the original package insert, 
results from an additional single-arm clinical study were included and were consistent with 
results of the controlled study (16% ORR in 99 patients, including 11 patients with CMML). It is 
of interest that European Medicines Agency (EMA) approved azacitidine, but not decitabine, for 
the treatment of non-proliferative (dysplastic) CMML only, in 2008. 
Cytoreductive agents such as hydroxyurea (HU) or cytarabine can reduce leukocytosis and, very 
rarely, splenomegaly in CMML with proliferative features, but usually worsen cytopenias and 
have modest impact on disease-associated symptoms (Padron 2014). Subsequent to the HMA 
approvals in MDS, additional clinical studies of these agents in CMML have demonstrated ORR 
centered at approximately 30-40% (range ~25% to 75%) upon initial exposure to HMAs, but 
responses were generally not sustained (Alfonso 2017, Moyo 2017, Patnaik 2016, Padron 2014, 
Coston 2019), with complete response (CR) rates of approximately 15%, and median OS of 12 to 
37 months (see Table 8 in Appendix Section 18.1) (Patnaik 2016). Clinical studies with a variety 
of cytotoxic drugs and targeted therapies have generally been disappointing and therapy was 
associated with significant toxicities (Patnaik 2016). 
Given these results, there is a need for additional therapies for patients with CMML, and 
especially those who have been previously treated with or are not expected to derive benefit from 
treatment with an HMA. Moreover, it has been recommended that “every CMML patient be 
considered for clinical trials irrespective of risk stratification or treatment history because of 
limited prospective clinical data and the disease’s aggressive natural history.” (Padron 2014). 
Historically (including in the current study), given CMML’s original classification as an MDS, 
clinical studies enrolling CMML patients had responses measured via the International Working 
Group (IWG) response criteria for MDS. However, it was subsequently observed that 
approximately 50% of patients with CMML predominantly present with myeloproliferative, 
rather than myelodysplastic features (Loghavi 2018). 
An international consortium of thought leaders recommended new response criteria to measure 
treatment response in MDS/MPN, including CMML, to capture measures of clinical benefit 
relating to CMML with proliferative features (Savona 2015) (see Table 8 in Appendix18.1 for 
full response criteria). These revisions were justified by the authors, who indicated that “the 
molecular and clinical heterogeneity and absence of uniform response criteria by which to 
assess meaningful therapeutic benefit make developing and comparing new therapies a 
challenge. Novel agents that target biological features important in MDS/MPN are in 
development; testing the effectiveness of these agents requires a harmonized assessment 
approach designed specifically for MDS/MPN”. 
One publication reports a retrospective validation of the revised criteria by outcome analysis of 
79 patients with CMML. In this analysis, response status between the IWG 2006 criteria and 
newer MDS/MPN criteria was concordant in 86% of cases, and both sets of response criteria led 
to similar predictive power for OS. Notably, the more stringent definition of progression by the 

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MDS/MPN criteria was described by the authors as ‘relevant’, as 6 patients who had PD per the 
IWG 2006 criteria at first assessment finally achieved response, whereas no patients with 
progression per overlap-MDS/MPN achieved response (Duchmann 2017). 
The 2018 European Hematology Association/European LeukemiaNet (EHA/ELN) expert panel 
for CMML recommends PB and bone marrow aspirate (cytology) assessment as mandatory; 
bone marrow biopsy is considered useful for the diagnosis as it allows the assessment of 
cellularity, description of stroma, of fibrosis, and detects the rare association of mast cells (in 
patients with concomitant systemic mastocytosis [SM] and CMML). Suggested 
immunohistochemistry and flow cytometry immunophenotyping include CD34 and the 
monocytic markers CD68, CD163, CD14, and CD16. CD14+/CD16- monocytes are considered 
‘classical’ and are proposed as biomarkers to monitor response to therapy. Cytogenetic analysis 
and the assessment of 4 genes -ASXL1, NRAS, RUNX1, and SETBP1 were considered mandatory. 
The panel also recommends that while the MDS/MPN 2015 criteria require additional validation 
in CMML, it is preferable to use the IWG 2006 criteria for monitoring response to treatment. For 
patients with splenomegaly, the panel recommended an imaging technique (ultrasound, 
computed tomography [CT] or magnetic resonance imaging [MRI]) rather than physical 
examination alone. Symptom burden has not been studied specifically in CMML and the use of 
Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF 
TSS) as an initial tool for symptom assessment is reasonable.  
4.2 
Targeting Cancer Stem Cells 
Cancer stem cells (CSCs) possess the capacity to self-renew in addition to generating the 
heterogeneous cancer cells that comprise the tumor (Jordan 2006). CSCs are defined by the 
ability to divide and give rise to DQHZVWHPFHOOVHOIဨUHQHZDOWKHDELOLW\WRJLYHULVHWRWKH
differentiated cells of an organ, and the genetic constraints on expansion of the cell population. 
Though challenging, useful CSC models have now been developed in myeloid malignancies. 
Recent studies propose how CSCs can be identified, and these, in turn, have helped garner a 
greater biological understanding and develop novel treatments that have the potential to destroy 
these quiescent chemoresistant cells. The notion of how CSCs adapt as a response to therapeutic 
pressures, cross-talks with the tumor microenvironment and drive interactions with the cancer 
ecosystem, which includes immune cells, fibroblasts and other extracellular components, is now 
recognized (Prager 2019). Taken collectively, CSCs significantly contribute to tumor 
heterogeneity, metastasis and resistance (Desai 2019). As illustration, canonical cell surface 
markers and functional approaches such as the reactive oxygen species production helped 
identify how BCL-2 inhibition is critical in diverse myeloid malignancies (Konopleva 2006, 
Lagadinou 2013). Recent work has also identified how CD123+/CD47+ leukemia stem cells 
(LSCs) are correlated with AML cell sensitivities and how CD123 may serve as a biomarker for 
chemoresistance (Yan 2019, Arai 2019). Furthermore, xenograft models of high-risk MDS 
demonstrate how autologous CD123 chimeric antigen receptor T cells may be useful as 
therapeutic options on the basis of CD123 expression on LSCs, making them a suitable cancer 

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target in these patients (Stevens 2019). In this context overexpression of CD123 has been 
observed in several other myeloid cell lines, including those derived from patients with blastic 
plasmacytoid dendritic cell neoplasm (BPDCN) and CMML (Frankel 2014; Economides 2019, 
Lucas 2019). 
4.3 
IL-3 Receptor (IL-5Į Overexpression in Hematologic Malignancies 
The alpha subunit of the human interleukin-3 receptor (IL-ĮUHFHSWRU ,/-5ĮDOVRFDOOHG
multi-colony stimulating factor) is a type I transmembrane glycoprotein belonging to the 
cytokine receptor superfamily; all the members of this superfamily are characterized by a 
conserved region homologous to the fibronectin type III domain. The IL-5LVDKHWHURGLPHURIĮ
(CD123) and ȕFKDLQV (the ȕFKDLQLVVKDUHGE\interleukin-3 (IL-3), IL-5, and granulocyte 
macrophage-colony stimulating factor [GM-CSF] receptors). The receptor, found on pluripotent 
progenitor cells, induces tyrosine phosphorylation within the cell and promotes proliferation and 
differentiation within the hematopoietic cell lines. 
IL-3R is overexpressed on myeloid leukemic blasts and CSCs relative to normal hematopoietic 
stem cells (Jordan 2000; Jordan 2006; Tehranchi 2010). CD34+/38- CSCs strongly express 
IL-3R, whereas IL-3R is virtually undetectable on normal CD34+/38- hematopoietic stem cells 
(HSCs) (Jordan 2000; Jordan 2006). The differential expression of IL-3R between malignant and 
normal stem cells provides a potential opportunity for a therapeutic window in which to target 
CSCs with an IL-3R-targeted therapy (e.g., tagraxofusp), while minimizing toxicity to normal 
bone marrow including normal HSCs. 
In addition to AML, IL-3R has also been shown to be differentially expressed on other 
hematological cancers, including blastic plasmacytoid dendritic cell neoplasm (BPDCN), MDS, 
CML, acute lymphoid leukemia (ALL), hairy cell leukemia, Hodgkin’s disease, and certain 
aggressive non-Hodgkin’s lymphomas (e.g., follicular cell, mantle cell, and Burkitt’s 
lymphomas) (Tehranchi 2010; Aldinucci 2005; Munoz 2001; Aldinucci 2002; Black 2003; 
Frolova 2010). Moreover, IL-3R is also overexpressed on CSCs of multiple hematologic 
malignancies, including CML, MDS, and T-cell ALL (Jordan 2006; Florian 2006; Lhermitte 
2006).  
A higher percentage of IL-3R-expressing CSCs within a patient’s tumor relates to poor outcome 
(Vergez 2011). In particular, AML patients with IL-3R-expressing CSCs that comprise  3.5% 
of their entire leukemia have a worse prognosis than patients with IL-3R-expressing CSCs that 
comprise < 3.5% of their entire leukemia (van Rhenen 2005). Interestingly, IL-3R-rich pDCs 
have been found to be increased in the bone marrow of patients with CMML (Lucas 2019). 
4.4 
Tagraxofusp 
Tagraxofusp (Elzonris; formerly known as SL-401, DT388IL3), a CD123-directed cytotoxin, is a 
recombinant fusion protein comprised of human IL-3 and truncated diphtheria toxin (DT) that 
targets the IL-3R. Tagraxofusp was granted breakthrough therapy designation for the treatment 

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of BPDCN in August 2016 and was approved by the US FDA for the treatment of BPDCN in 
adults and pediatric patients, 2 years and older, in December 2018. 
Tagraxofusp is a 524-amino acid recombinant fusion protein expressed in Escherichia coli from 
a hybrid gene composed of the deoxyribonucleic acid (DNA) sequence of a truncated DT 
payload genetically fused to the DNA sequence of human IL-3 (Figure 1). The tagraxofusp 
protein consists of an N-terminal methionine, followed by the first 388 amino acids of DT 
comprising the catalytic and translocation domains. This truncated DT fragment is joined at the 
C-terminus through a 2-amino acid linker to the full amino acid sequence for human IL-3. The 
protein is engineered such that the IL-3 domain replaces the native receptor-binding domain of 
DT and is thereby able to target tagraxofusp to cells that express CD123. 
Figure 1: 
Schematic of Tagraxofusp Construction 
Abbreviations: DT=diphtheria toxin; IL-3=interleukin-3 
The IL-3 domain of tagraxofusp binds to cell surface IL-3R and triggers receptor-mediated 
endocytosis of tagraxofusp into endosomes (Gesner 1988, Rapoport 1996). In the acidic 
environment of the early endosomes and lysosomes, the DT domain of tagraxofusp undergoes 
nicking in the loop between the catalytic and translocation domains by cellular proteases such as 
trypsin and furin (Drazin 1971, Tsuneoka 1993, Gordon 1995). The DT translocation domain 
undergoes a conformational change, during which its hydrophobic helices insert into the 
endosomal membrane to form a pore, facilitating the passage of the DT catalytic domain into the 
cytosol (Boquet 1976, Donovan 1981, Kagan 1981) in a process aided by multiple host cell 
cytosolic proteins (Ratts 2003, Ratts 2005). Upon exposure to the reducing environment of the 
cytosol, the DT catalytic domain dissociates from the DT translocation and IL-3 domains 
(Collier 1971). In the cytosol, the DT catalytic domain of tagraxofusp catalyzes the transfer of 
adenosine diphosphate-ribose from nicotinamide adenine dinucleotide to a diphthamide residue 
on EF-2 (Honjo 1968), leading to irreversible inhibition of protein synthesis and ultimately 
apoptosis (Kochi 1993).
Tagraxofusp drug product is prepared as liquid or lyophilized formulations.  The study site may 
be provided with either of the following: 

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x Tagraxofusp Injection is a preservative-free, sterile, clear, colorless solution supplied in 
single-dose glass vials containing 1 mL of sterile tagraxofusp solution (1 mg/vial) that 
should be stored in a freezer between -25°C and -15°C (-13°F and 5°F).   
x Tagraxofusp for Injection (lyophilized powder), 1.0 mg is supplied in single-use, sterile, 
2 mL glass vials packaged in labeled, single-vial cartons (study drug) and should be 
stored between 2°C and 8°C (36°F – 46°F). 
Overall, tagraxofusp was generally well-tolerated in the clinical development program, and no 
evidence of cumulative toxicity with tagraxofusp has been seen. The most common 
treatment-emergent adverse events (TEAEs) with tagraxofusp include liver transaminase 
elevations; manifestations of capillary leak syndrome (CLS), including hypoalbuminemia, 
edema, and weight increases; hematologic abnormalities, primarily thrombocytopenia and 
anemia; nausea and other gastrointestinal symptoms; and constitutional symptoms. 
Refer to the Investigator’s Brochure for complete information on tagraxofusp. 
4.5 
Rationale for the Current Study 
Certain subtypes of MPNs and MDS/MPNs represent clonal proliferations arising from 
malignant myeloid stem cells with propensity to overexpress IL-3R, rendering them potentially 
susceptible to tagraxofusp. MPNs are associated with considerable morbidity and mortality, and 
risk of transformation to AML. The substantial IL-3R expression on mast cells and eosinophils 
suggests that tagraxofusp may have the potential to diminish tumor bulk in addition to relevant 
underlying stem cell populations. The visible presence of pDC nodular infiltrates in the bone 
marrow of a subset of CMML patients suggests a potential role of supporting dendritic cells 
within some of these neoplasia; preclinical data from other myeloid malignancies has indicated 
that targeting of these IL-3R expressing supporting cell populations may augment tagraxofusp 
antineoplastic effects observed against malignancies characterized by IL-3R expression 
(Chauhan 2014). 
CD123 expression has been detected on CMML blasts, CMML monocytes, and LSCs in both 
MPNs and CMML (Shen 2015, Krishnan 2018). In one study of 20 CMML patient samples, 
CD123 was found to be expressed at higher levels on blasts and monocytes compared to 
lymphocytes, which showed low to no expression (Krishnan 2018). Moreover, CD123 
expression on both blasts and monocytes was higher in CMML-1 and CMML-2 patients relative 
to CMML-0 patients (Krishnan 2018). Another study assessing 118 CMML bone marrow 
samples by a validated multi-color flow cytometry immunophenotyping assay found that CD34+ 
blasts exhibited increased expression of CD123 in 64% of CMML patients compared to 3% of 
control patients (Shen 2015). 
CD123 is also expressed on neoplastic pDCs in the tumor microenvironment of CMML 
(Facchetti 2016, Lucas 2019, Vermi 2004, Brunetti 2017, Ji 2014, Naresh 2010, Vermi 2011). 
These pDCs have been shown to share mutations with, and belong to, the malignant CMML 
clone (Lucas 2019). In particular, pDCs have been shown to share RAS pathway mutations with 

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the CMML clone, which are associated with poor prognosis including a significant increase in 
the cumulative risk of AML transformation (Lucas 2019). Notably, RAS pathway mutations are 
associated with a higher fraction of pDCs in the bone marrow (> 5%) of patients with CMML 
and clinically manifest as proliferative disease (Lucas 2019, Ricci 2010). Consistent with these 
findings, pDCs have been identified in the spleen of some patients with CMML, and it has been 
suggested that pDCs could serve as a therapeutic target in patients with CMML (Lucas 2019, 
Pophali 2018). 
Initially in this study, patients with CMML and MF as well as mastocytosis, or advanced 
symptomatic CEL were eligible for enrollment. The primary objective of Stage 1 was to 
establish the MTD or the MTeD at which multiple DLTs were not observed. In Stage 2, further 
characterization of the safety and initial assessment of clinical activity at the recommended phase 
2 dose were intended in patients with MF and CMML. 
In Stage 1, 9 patients (5 with CMML and 4 with MF) received tagraxofusp at doses of 7, 9, or 
12 mcg/kg via IV infusion on days 1-3 every 21 days for Cycles 1-4, every 28 days for Cycles 5-
7, and every 42 days for Cycles 8 and beyond. In Stage 2, patients with CMML and MF received 
tagraxofusp at the recommended phase 2 dose, 12 mcg/kg, on the same schedule as Stage 1. 
As of July 2021, 36 patients have been enrolled, comprising 20 patients with CMML-1 and 
16 with CMML-2; median age was 69 years (range 42–81), and 75% of patients were male. 
Twenty-three patients (64%) had either high- or intermediate-risk genetics based on CPSS, 
GFM, MMM, or ELN risk stratification systems.  Prior therapies included HMA in 16 patients 
(43%), allogeneic stem cell transplantation (allo-SCT) in 3 (8%), and other in 12 (32%); 
7 patients (19%) were high-risk and treatment naive. Overall, 16 patients (44%) had baseline 
palpable splenomegaly; in 12 of these patients, VSOHHQVL]HZDVFPEHORZOHft costal margin. 
Overall, 4 of 36 (11%) patients achieved bone marrow morphological complete responses 
(BMCRs), 1 of whom was bridged to allo-SCT; all 4 patients had splenomegaly at baseline. It is 
noteworthy that 2 of the 4 BMCRs, were observed in patients with high-risk genetic features. 
Fifteen patients (42%) with baseline splenomegaly had spleen responses; 9 patients (60%) had a 
UHGXFWLRQLQVSOHHQVL]HLQFOXGLQJZLWKVSOHQRPHJDO\RIFPDWEDVHOLQH 
Based on preliminary clinical activity observed in the current study and increasing scientific and 
clinical knowledge of CMML, the protocol was amended (Amendment 7) to add Stage 3A for 
patients with CMML. Enrollment in Stage 2 was closed; however, patients with CMML or MF 
already enrolled were allowed to continue study participation in Stage 2.   
5 
Design of Study 
5.1 
Description of the Type/Design of Study to be Conducted and Purpose 
This is a non-randomized, open-label, multicenter study, divided into multiple stages.  
Chronic Myelomonocytic Leukemia and MF patients consented and enrolled with Amendment 6 
or prior, who are currently on active treatment or in survival follow-up, will continue to be 

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followed according to the schedule of events in Amendment 6. These patients will not be 
reconsented under Amendment 7 or beyond.  
Stage 3A (CMML): 
Stage 3A is a 2-arm, non-randomized, open-label multicenter study stage in patients with CMML 
intended to identify clinically important responses that connote clinical benefit and potential 
endpoints to inform the design of a pivotal Stage 3B in patients with CMML (to be added under 
the auspices of a separate amendment), as well as gather data on CD123 expression on pDCs and 
monocytes in CMML. 
Stage 3A will enroll 2 populations of patients with CMML, those with CMML-1 or CMML-2 
who are refractory/resistant/intolerant to HMAs, or HU, or intensive chemotherapy; and patients 
with treatment naïve CMML-1 or CMML-2 with molecular features associated with a poor 
prognosis. 
In Stage 3A, patients will be administered tagraxofusp at a dose of 12 mcg/kg as a 15-minute IV 
infusion once daily on Day 1 to 3 of a 21-day cycle (C1 to C4) and then on Day 1 to 3 of a 
28-day cycle (C5 and beyond). The dosing period may be extended for dose delays up to Day 10 
of each cycle.  
Efficacy assessments will include bone marrow (aspirate and biopsy), peripheral blood (complete 
blood count [CBC] and differential with percent monocytes, neutrophils, neutrophil precursors, 
immature myeloid cells, and blasts), hepatosplenomegaly by MRI or CT, other extramedullary 
disease (e.g., cutaneous disease, disease-related serous effusions), symptom score analysis by the 
MPN-SAF TSS, cytogenetic burden, molecular response, reduced dependence on transfusion, 
reduced risk of infection, and survival status. 
Safety will be assessed throughout the duration of the study; safety assessments will include 
physical examinations, vital sign measurements, ECGs, clinical laboratory evaluations, adverse 
event (AE) reporting (including DLTs, AEs, SAEs), and reasons for treatment discontinuation 
due to toxicity.  
Blood samples for immunogenicity assessments will be collected for the detection of tagraxofusp 
reactive antibodies. 
Plasmacytoid dendritic cells (pDCs) and CD123 expression will be assessed centrally on all bone 
marrow and peripheral blood samples by flow cytometry and immunohistochemistry prior to the 
start of and during treatment. Additionally, leukocyte populations will be monitored in CMML. 
Exploratory assessments for CMML patients will include peripheral blood for the evaluation of 
cytokine IL-10, CD14+/CD16-, CYTOF (Mass cytometry), and NGS sequencing at selected sites 
prior to the start of and during treatment. 

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5.2 
Data Safety Review Committee 
A Data Safety Review Committee (DSRC), which will include investigators and representatives 
from the Sponsor, will convene periodically to review data from Stages 2 and 3A of the study. 
The DSRC will also convene in the event of identification of unexpected AEs, or AEs occurring 
at a frequency or severity not previously anticipated or following deaths on-study which are 
considered treatment related and/or not related to the underlying disease and sequelae. 
5.3 
Data Collection and Study Completion 
When sufficient information is available to enable assessment of the primary endpoint and 
selected secondary endpoints, data collection may cease. The Study Completion date for the 
entire study will be the date beyond which study data are no longer entered into the primary 
database and the database is locked.  
6 
Study Objectives 
6.1.1 
Stage 3A 
Objectives of Stage 3A in patients with CMML are: 
x To characterize the safety profile of tagraxofusp.  
x To obtain preliminary evidence of response to tagraxofusp therapy as assessed by the 
MDS/MPN 2015 criteria (Savona 2015), with the addition of a stable disease category, 
and to obtain data relative to additional clinical parameters that may be used in 
determination of therapeutic benefit. 
The MDS/MPN 2015 criteria (Savona 2015) represent the current consensus criteria for 
evaluation of clinical benefit in patients with CMML, beyond those specified in the IWG-MDS 
criteria (Cheson 2006). Thus, as an inherent component of the design of Stage 3A, responses to 
treatment are assessed using the MDS/MPN 2015 criteria.  The hematology community has 
recognized that a lack of a stable disease (SD) category in the 2015 MDS/MPN IWG criteria 
creates considerable uncertainty in the categorization of patients on any CMML study.  
Therefore, a SD category, defined as those patients not belonging to any of the defined 
categories in the 2015 criteria, has been added as a response category. 
The purpose of Stage 3A is to evaluate the clinical benefit derived from individual components, 
or variations thereof, of the MDS/MPN 2015 criteria that may allow for a prospective definition 
of a primary efficacy endpoint, that will provide the primary evidence of efficacy for regulatory 
decision-making in the planned confirmatory cohort (Stage 3B; to be added under the auspices of 
a separate amendment).  
7 
Populations to be Studied 
Stage 3A will include patients with CMML as follows: 
x Patients with 2016 WHO-defined CMML, including those with  

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- CMML-1 or CMML-2 who are refractory/resistant/intolerant to HMAs, or HU, or 
intensive chemotherapy; and  
- Treatment naïve CMML-1 or CMML-2 with molecular features associated with a 
poor prognosis.  
7.1 
Patient Selection Criteria 
7.1.1 
Inclusion Criteria 
Patients meeting all of the following criteria may be considered for enrollment: 
1. The patient is  18 years old. 
2. The patient has a life expectancy of > 6 months. 
3. The patient has an Eastern Cooperative Oncology Group (ECOG) performance status 
(PS) of 0-2. 
4. The patient has adequate baseline organ function, including cardiac, renal, and hepatic 
function: 
x Left ventricular ejection fraction (LVEF)  institutional lower limit of normal as 
measured by multigated acquisition scan (MUGA) or 2-dimensional (2-D) 
echocardiogram (ECHO) within 28 days prior to start of therapy and no clinically 
significant abnormalities on a 12-lead electrocardiogram (ECG). 
x Serum creatinine  1.5 mg/dL. 
x Serum albumin  3.2 g/dL (or  32 g/L) in the absence of receipt of IV albumin 
within the previous 72 hours. 
x Bilirubin  1.5 mg/dL. 
x Aspartate transaminase (AST) and alanine transaminase (ALT)  2.5 times the upper 
limit of normal (ULN). 
x Creatine phosphokinase (CPK)  2.5 times the ULN. 
x Absolute neutrophil count (ANC)  0.5×109/L. 
5. If a woman of child-bearing potential (WOCBP), the patient has a negative serum or 
urine pregnancy test within 1 week prior to tagraxofusp treatment (intervals shorter than 
1 week are acceptable, if required by institutional guidelines). 
6. The patient (either male or female) agrees to use acceptable contraceptive methods for 
the duration of time in the study, and to continue to use acceptable contraceptive methods 
for 1 week after the last tagraxofusp infusion. 
7. The patient has signed informed consent prior to initiation of any study-specific 
procedures or treatment. 
8. The patient is able to adhere to the study visit schedule and other protocol requirements, 
including follow-up for response assessments. 

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9. Patient has a 2016 WHO-GHILQHGGLDJQRVLVRI&00/SHUVLVWHQWPRQRF\WRVLVî/
IRUDWOHDVWPRQWKVZLWKRWKHUFDXVHVH[FOXGHGDQGPRQRF\WHVRI:%&LQ
peripheral blood, no criteria and no previous history of CML, ET, PV, and acute 
promyelocytic leukemia; if eosinophilic, neither PDGFRA, PDGFRB, FGFR1 
rearrangements nor PCM1-JAK2 translocation; < 20% blasts in peripheral blood and 
bone marrow aspirate; > 1 following criteria: dysplasia in > 1 myeloid lineage, acquired 
clonal cytogenetic or molecular abnormality in hematopoietic cells). 
10. Patient has 2016 WHO-defined CMML-1 (2-4% blasts in peripheral blood and/or 5-9% 
blasts in bone marrow) and CMML-2 (5-19% blasts in peripheral blood and/or 10-19% 
blasts in bone marrow, and/or presence of Auer rods) (Arber 2016). 
11. Patient is refractory/resistant/intolerant, as defined for the purposes of this study (in the 
absence of a standard definition for CMML) below, to HMAs, or HU, or intensive 
chemotherapy, including:  
x Resistance/intolerance to HU is defined as: 
- Uncontrolled myeloproliferation, (platelets > 400×109/L and WBC > 10×109/L 
after 3 months of at least 2 g/day of HU); or 
- Myelosuppression at a clinically relevant dose; or 
- Presence of unacceptable HU-related non-hematological toxicities, such as 
mucocutaneous manifestations, gastrointestinal symptoms, pneumonitis or fever 
at any dose of HU. 
Conventional definition for HMA failure is defined for the purposes of this study 
(in the absence of a standard definition for CMML) as: 
- Disease progression following at least 4 to 6 cycles of 5-azacitidine or decitabine; 
or 
- Relapse after achieving response; or 
- Intolerance to 5-azacitidine or decitabine at the prescribed dose. 
OR 
Patient is classified as high-risk based on the presence of morphological features, as 
described by the 2016 WHO prognostic system (Arber 2016), and the clinical and 
molecular features described in molecularly-integrated prognostic systems, such as the 
Groupe Français des Myélodysplasies (GFM), Mayo Molecular Model (MMM), and the 
CMML VSHFLILFSURJQRVWLFPRGHO&366ဨ0RO (Woo 2020) and thus is not expected to 
benefit from HMAs.  
12. Patient is ineligible for an immediate allo-SCT.  
 
7.1.2 
Exclusion Criteria 
Patients meeting any of the following criteria are not eligible for enrollment in any study stage: 

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1. Patient has persistent clinically significant toxicities Grade  2 from previous therapies, 
including cytotoxic chemotherapy, targeted therapies, biological therapies, or 
immunotherapies, not readily controlled by supportive measures (excluding alopecia, 
nausea, and fatigue). 
2. Patient has received treatment with any disease-related therapy, including radiation 
therapy within 14 days of study entry. 
3. Patient has received an allo-SCT within 3 months of study entry. 
4. Patient has received treatment with another investigational agent within 14 days of study 
entry or concurrent treatment with another investigational agent. 
5. Patient has previously received treatment with tagraxofusp or has a known 
hypersensitivity to any components of the drug product. 
6. Patient has an active malignancy and/or cancer history (excluding myeloproliferative 
disorders and concomitant myeloid malignancies as specified in the inclusion criteria) 
that can confound the assessment of the study endpoints. Patients with a past cancer 
history (within 2 years of entry) and/or ongoing active malignancy or substantial potential 
for recurrence must be discussed with the Sponsor before study entry. Patients with the 
following neoplastic diagnoses are eligible: non-melanoma skin cancer, carcinoma in situ 
(including superficial bladder cancer), cervical intraepithelial neoplasia, or organ-
confined prostate cancer with no evidence of progressive disease. 
7. Patient has clinically significant cardiovascular disease (e.g., uncontrolled or any New 
York Heart Association Class 3 or 4 congestive heart failure, uncontrolled angina, history 
of myocardial infarction, unstable angina, or stroke within 6 months prior to study entry, 
uncontrolled hypertension or clinically significant arrhythmias not controlled by 
medication). 
8. Patient has uncontrolled, clinically significant pulmonary disease (e.g., chronic 
obstructive pulmonary disease, pulmonary hypertension) that, in the Investigator’s 
opinion, would put the patient at significant risk for pulmonary complications during the 
study. 
9. Patient has known active or suspected disease involvement of the central nervous system 
(CNS). If suspected due to clinical findings, CNS disease should be ruled out with 
relevant imaging and/or examination of cerebrospinal fluid. 
10. Patient is receiving immunosuppressive therapy, with the exception of corticosteroids as 
specified in the inclusion criteria and tacrolimus, for treatment or prophylaxis of graft-
versus-host disease (GVHD). If the patient has been on immunosuppressive treatment or 
prophylaxis for GVHD, the treatment(s) must have been discontinued at least 14 days 
prior to study drug and there must be no evidence of Grade  2 GVHD. 
11. Patient has uncontrolled intercurrent illness including, but not limited to, uncontrolled 
infection, disseminated intravascular coagulation, or psychiatric illness that would limit 
compliance with study requirements. 
12. Patient is pregnant or breast feeding.  
13. Patient has known human immunodeficiency virus (HIV). 

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14. Patient has evidence of active or chronic Hepatitis B or Hepatitis C infection. 
15. Patient is oxygen-dependent. 
16. Patient has any medical condition that in the Investigator’s opinion places the patient at 
an unacceptably high risk for toxicities. 
17. Patient requires corticosteroid therapy at a dose of > 20 mg daily for > 7 days or has had 
changes to their steroid regimen within 28 days of screening. 
18. Patient has 2016 WHO-defined transformation to leukemia. 
19. Patient has AML M4 (French-American-British subtype; myelomonocytic). (Note: if this 
is suspected, the NPM1 gene must be assessed to determine eligibility). 
7.2 
Replacement of Patients 
At the discretion of the Sponsor, additional patients may be enrolled to provide sufficient patient 
data for analysis after a patient prematurely withdraws from the study. 
8 
Treatment of Subjects 
8.1 
Tagraxofusp Description and Storage 
Tagraxofusp Injection is a biologic fusion protein comprised of recombinant human IL-3 
genetically fused to truncated DT protein. Tagraxofusp targets the IL-3R, which is overexpressed 
on the CSCs and bulk of various leukemias and hematopoietic malignancies relative to normal 
hematopoietic stem cells and other hematopoietic cells.  
Tagraxofusp is prepared in liquid or lyophilized formulations; study sites may be provided with 
either of the following:  
• 
Tagraxofusp Injection is a preservative-free, sterile, clear, colorless solution supplied in 
single-dose glass vials containing 1 mL of sterile tagraxofusp solution (1mg/vial) that should be 
stored in a freezer between -25°C and -15°C (-13°F and 5°F).   
• 
Tagraxofusp for Injection (lyophilized powder), 1.0 mg is supplied in single-use, sterile, 
2 mL glass vials packaged in labeled, single-vial cartons (study drug) and should be stored 
between 2°C and 8°C (36°F – 46°F). 
Documentation stating the product’s expiry date will be provided with each shipment. 
8.2 
Study Treatment Administration Schedule 
Patients will receive 12 mcg/kg of tagraxofusp by IV infusion once daily for 3 consecutive days 
(or 3 doses over a period not to exceed 10 days if postponement is required to allow for toxicity 
resolution) of a cycle in the absence of PD or other withdrawal criteria.  
A treatment cycle is 21 days in C1-4 and 28 days in C5 and beyond. 
The total per-patient dose is calculated based on patient body weight in kg at baseline (C1D1). 
This dose will be recalculated if there is a 10% or greater change from baseline in body weight. 

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The first cycle of tagraxofusp must be administered in the inpatient setting, with hospitalization 
beginning the day of the first infusion of tagraxofusp (or a prior day) and ending approximately 
24 hours after the last infusion of tagraxofusp. Subsequent cycles of tagraxofusp can be 
administered in the inpatient setting or in a suitable outpatient ambulatory care setting that is 
equipped for intensive monitoring of patients with hematopoietic malignancies undergoing 
treatment, per the Investigator’s discretion, institutional guidelines, and capabilities. Patients will 
be monitored for at least 1 hour (or longer at the Investigator’s discretion) following the 
administration of each infusion of tagraxofusp in Cycle 2 and beyond. 
Patients with evidence of ongoing disease control during treatment (without evidence of 
clinically significant PD or intolerable toxicity) may receive repeated cycles of tagraxofusp even 
if an overall response, in the judgment of the Investigator, is not attained.  
Refer to Section 8.2.1 for details regarding required pre-medication, patient monitoring 
procedures, and dose modification procedures for the management of tagraxofusp-related 
toxicity.  
8.2.1 
Tagraxofusp Premedication, Dose Preparation and Administration 
8.2.1.1 Premedication 
Patients will receive the following premedication 60 minutes (±15 minutes) before each 
tagraxofusp infusion: 
x Acetaminophen 650 mg by mouth (PO) (or equivalent dose of paracetamol). 
x Diphenhydramine 50 mg IV (or equivalent dose of another H1-histamine antagonist). 
x Methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid). 
x Famotidine 20 mg IV (or an equivalent dosage of another H2-histamine antagonist). 
8.2.1.2 Tagraxofusp Dosage Preparation 
Tagraxofusp is administered as a 15-minute IV infusion. Tagraxofusp is prepared for 
administration by the pharmacy. The total per-patient dose is calculated based on the patient’s 
baseline body weight in kg (at baseline, C1D1) including one decimal place (mcg/kg dose × 
patient weight in kg [example: 12 mcg/kg × 70.3 kg]). (The dose will be recalculated if there is a 
10% or greater change from baseline in body weight.) Additional dose preparation instructions 
and required supplies are described in detail within the Pharmacy Manual. 
8.2.1.3 Inpatient and Outpatient Setting for Dose Administration 
The first cycle of tagraxofusp must be administered in the inpatient setting, with hospitalization 
beginning the day of the first infusion of tagraxofusp (or a prior day) and ending approximately 
24 hours after the last infusion of tagraxofusp. Subsequent cycles of tagraxofusp can be 
administered in the inpatient setting or in a suitable outpatient ambulatory care setting that is 
equipped for intensive monitoring of patients with hematopoietic malignancies undergoing 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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treatment, per the Investigator’s discretion and institutional guidelines and capabilities. Patients 
will be monitored for at least 1 hour (or longer at the Investigator’s discretion) following each 
tagraxofusp infusion in Cycle 2 and beyond. 
8.2.2 
Patient Monitoring Procedures During the Tagraxofusp Dosing Period 
During each cycle, testing and procedures that may result in withholding of a scheduled 
tagraxofusp infusion, (largely based on unresolved manifestations of fluid retention and/or other 
relevant acute toxicities during daily dosing), include findings from clinical examination 
including but not limited to vital signs, and clinical laboratory parameters, detailed below, and as 
indicated in the applicable Schedules of Events (Table 2 and Table 3 for Stage 2; Table 4 and 
Table 5 for Stage 3A). 
Vital Signs: Blood pressure, heart rate, respiration rate, body temperature, and pulse oximetry are 
to be measured during screening and during the dosing period (usually Days 1, 2, and 3) 
immediately prior to infusion, immediately after completion of infusion, and 30 and 60 minutes 
post-infusion; and at subsequent time points in each cycle as indicated in the applicable 
Schedules of Events (Table 2 and Table 3 for Stage 2; Table 4 and Table 5 for Stage 3A). 
Diagnostic Tests: 
x During the dosing period prior to tagraxofusp infusion (usually Days 1, 2, 3) and at 
subsequent time points in each cycle as indicated in the applicable Schedules of Events 
(Table 2 and Table 3 for Stage 2; Table 4 and Table 5 for Stage 3A): CBC with 
differential, platelets, sodium, potassium, chloride, bicarbonate, blood urea nitrogen 
(BUN), creatinine, glucose, total protein, albumin, calcium, phosphorus, uric acid, total 
bilirubin, ALT, AST, alkaline phosphatase, lactate dehydrogenase (LDH), prothrombin 
time (PT) or International Normalized Ratio (INR), aPTT (activated partial 
thromboplastin time). Additional evaluation of albumin or ALT/AST during days 
subsequent to treatment days may be indicated in situations where abnormalities 
(albumin decrease, ALT/AST increase) are noted subsequent to treatment. 
x 6HUXPDOEXPLQPXVWEH 3.2 g/dL prior to first dose of tagraxofusp in Cycle 1.  During 
tagraxofusp dosing, serum albumin muVWEHJG/,IVHUXPDOEXPLQLVUHGXFHGE\
 0.5 g/dL from the albumin value measured prior to tagraxofusp dosing initiation for the 
current cycle, withhold tagraxofusp infusion and administer 25g IV albumin.  Interrupt 
tagraxofusp dosing until seruPDOEXPLQLVJG/$1'QRWPRUHWKDQ g/dL lower 
than the value measured prior to dosing initiation for the current cycle.    
x For temperature  38°C, draw blood culture × 2, and collect urine for urinalysis and 
culture. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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8.2.3 
Dose Delays/Modifications and Management Procedures for Toxicities Associated with 
Tagraxofusp 
During the dosing period for each cycle, individual tagraxofusp infusions may be delayed for up 
to 10 days to allow for toxicity resolution.  
If dosing is resumed within a cycle, any subsequent doses in that cycle must be administered 
within the first 10 days of that cycle; thus, patients may receive fewer than the prescribed 
number of doses during a given study cycle. Tagraxofusp may be resumed after the resolution of 
Grade 3/4 toxicities as per Table 1.  
8.2.3.1 Capillary Leak Syndrome and Associated Symptoms 
CLS is associated with vascular endothelial injury related to fusion protein administration and 
may occur 3 – 8 days after initiation of treatment.  
Patients may exhibit symptoms of hypotension, fluid overload, evidenced by weight gain or 
edema, nausea, and anorexia, shortness of breath and, at times, confusion and muscle injury. 
Findings may include hypoalbuminemia, reductions in blood oxygen saturation, and evidence 
of pulmonary edema on chest x-ray. These symptoms may present individually or as part of 
CLS.  
Refer to Appendix Section 18.3 for management of patients with signs of CLS. 
8.2.3.2 Chills, Anaphylaxis, and Hypersensitivity Reactions 
Withhold tagraxofusp infusion for chills, anaphylaxis and hypersensitivity reactions.  
Chills associated with tagraxofusp administration may be treated with meperidine 12.5-50 mg IV 
or morphine sulphate 1-2 mg IV (or equivalent doses of other opiates). Anaphylaxis and 
hypersensitivity reactions associated with rash, fever, urticaria, bronchospasm, and/or 
angioedema will be treated with 100 mg IV methylprednisolone (or an equivalent corticosteroid) 
and 25-50 mg IV diphenhydramine (or equivalent dose of another H1-histamine antagonist). 
More severe symptoms will also be treated with 0.3 mL epinephrine (1:1000) IV once. Patients 
with anaphylactic (Grade 4) reactions or Grade  3 hypersensitivity reactions should not receive 
additional infusions of tagraxofusp.  
In the setting of Grade 1-2 hypersensitivity reactions, administration of subsequent tagraxofusp 
infusions may be attempted provided that any systemic symptoms of the prior Grade 1-2 
hypersensitivity reaction resolved within 24 hours with appropriate supportive measures. 
Premedication for patients with prior Grade 1-2 hypersensitivity reactions should include the 
agents specified in Section 8.2.1; additional premedication may be provided at the Investigator’s 
discretion and should be discussed with the Medical Monitor or designee. Please consult 
Section 13.7 concerning recommended optimal reporting of tagraxofusp-related hypersensitivity 
reactions. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Blood (serum) samples (10 mL, for immunogenicity) will be collected anytime during the study 
when clinical manifestations are observed suggesting either an infusion related reaction or drug 
hypersensitivity.  
8.2.3.3 Transaminase (AST/ALT) Elevations 
In settings in which transaminases (AST/ALT) are elevated to > 5uULN, no subsequent 
tagraxofusp will be administered for the duration of the cycle.  
8.2.3.4 Body Temperature  38°C 
For temperature  38°C, draw blood culture × 2, and collect urine for urinalysis and culture, as 
clinically indicated. Tagraxofusp may be administered pending resolution, provided that an 
appropriate evaluation for infectious etiologies has been undertaken, and provided that the 
Investigator determines that there is minimal likelihood of uncontrolled systemic infection 
including sepsis; this assessment may occur on the same day as the temperature elevation, or on 
subsequent days. 
8.2.3.5 Serum Creatinine > 1.8 mg/dL 
Withhold tagraxofusp infusion until serum creatinine resolves to  1.8 mg/dL. Dosing may 
resume upon recovery of serum creatinine if this occurs within the first 10 days of a cycle. 
8.2.3.6 Tachycardia, Bradycardia, or Hypertension 
Withhold tagraxofusp infusion for patients with a heart rate  130 bpm or heart rate  40 bpm or 
systolic BP  160 mmHg until resolution. 
8.2.3.7 Tumor Lysis Syndrome 
Treatment with cytotoxic cancer therapies in the setting of high tumor burden may cause rapid 
tumor lysis syndrome (TLS) and associated metabolic disturbances which can result in 
hyperkalemia, hyperuricemia, hyperphosphatemia and hypocalcemia. A low incidence of TLS 
has been reported with tagraxofusp. The Sponsor advises continued awareness of the possibility 
of acute and potentially life-threatening TLS in patients with high disease burden.  
Serum chemistries to carefully monitor for potential laboratory or clinical TLS are included in 
the daily laboratory tests during tagraxofusp infusion. In the event of evidence of TLS, local 
standards should be followed to monitor and treat TLS. For example, IV hydration (3 L/24 hr in 
adults) in addition to other measures to maintain high urine output, hypouricemic agents, and 
additional interventions to correct electrolyte abnormalities may be given at the discretion of the 
Investigator. 
8.2.3.8 Cytokine Release Syndrome 
Cytokine release syndrome results from an excessive immune response with elevated circulating 
cytokines that can cause symptoms ranging from flu-like symptoms, confusion, and rigors to a 
potentially fatal sepsis syndrome with circulatory collapse. The Sponsor recommends vigilance 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Protocol STML-401-0314 
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CONFIDENTIAL 
and appropriate clinical management that may include, hydration, steroids, and/or anti-IL-6 
agents at the Investigator’s discretion. 
8.2.3.9 Other Toxicities 
Hold dose for clinically significant Grade 3/4 toxicities for the current cycle, with the exception 
of the following Grade 3 toxicities, if deemed appropriate by the Investigator: 
x Arthralgia 
x Myalgia 
x Fever responding to treatment with no active infection 
x Nausea and/or vomiting, or diarrhea associated with suboptimal prophylaxis and/or 
treatment 
x Reversible clinical chemistry abnormalities (refer to Sections 8.2.3.3 and 8.2.3.5 for 
details regarding liver transaminases, and creatinine, respectively, and Appendix 
Section 18.3 for details regarding albumin). 
Refer to Section 8.2.3.10.1 for further instruction regarding dose delay. 
8.2.3.10 Dose Modifications/Delays and Management Procedures for Other Toxicities 
Associated with Tagraxofusp 
8.2.3.10.1 Nonhematological Toxicity 
Table 1 summarizes the dose modification guidelines for tagraxofusp-related nonhematological 
toxicities (other than those identified in Section 8.2.3.1 through Section 8.2.3.8).  
Table 1: 
Dose Modifications for Other Tagraxofusp-Related Nonhematological Toxicity 
CTCAE Grade 
Tagraxofusp Dose Delays 
Any Grade 1-2 toxicities 
x 
No dose delay 
Grade 3 with resolution to Grade  1 or 
baseline by last day of cycle 
x 
No dose delay 
Grade 3 without resolution to Grade  1 
or baseline by last day of cycle 
x 
Delay the start subsequent cycle by up to 14 days.  
- 
If after 14 days the toxicity resolves to Grade  1 or baseline, no 
dose adjustment required and the cycle may start. 
- 
If after 14 days the toxicity has not resolved, monitor weekly until 
resolution; discuss additional dosing and schedule with the Medical 
Monitor. 
Grade 4 (excluding transient [ 14 days] 
asymptomatic transaminase or CPK 
elevations) with resolution to Grade  1 
or baseline by last day of cycle 
x 
The cycle may start. 
Grade 4 without resolution to Grade  1 
or baseline by last day of cycle 
x 
Delay the start subsequent cycle by up to 14 days.  
x 
If after 14 days the toxicity resolves to Grade  1 or baseline, 
resume dosing.  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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CTCAE Grade 
Tagraxofusp Dose Delays 
x 
If after 14 days the toxicity has not resolved, monitor weekly until 
resolution; discuss additional dosing and schedule with the Medical 
Monitor 
 
Note that delays in start of subsequent cycles greater than 3 weeks will be acceptable only after 
discussion with the Medical Monitor regarding the potential risk/benefit of further treatment. 
8.2.3.10.2 Hematological Toxicity 
Patients with neutropenia or thrombocytopenia as a consequence of their disease do not require 
treatment interruptions for myelosuppression. Dose modifications in these patients should be 
considered on a case-by-case basis and discussed with the Medical Monitor. The following 
guidelines can be used for these patients:  
x Patients with a response and pre-cycle counts of neutrophils > 1000/L and platelets 
> 50,000/L who have sustained low counts of neutrophils < 500/L and/or platelets 
< 20,000/L for more than 2 consecutive weeks in the current cycle, may receive a 
subsequent cycle of tagraxofusp, at the Investigator’s discretion.  
x If there are persistent blasts in the peripheral blood or > 5% blasts in the bone marrow, 
continue treatment regardless of neutrophil and platelet count and give supportive care as 
needed.  
x If no evidence of leukemia in the bone marrow, consider holding (postponing) therapy 
until recovery of neutrophils to  1000/L and platelets  50,000/L, then resume 
tagraxofusp according to guidelines mentioned above. 
8.3 
Treatment Discontinuation 
8.3.1 
Criteria for Treatment Discontinuation 
Tagraxofusp treatment may be discontinued for any of the following reasons:  
x Patient withdrawal of consent. 
x Occurrence of unacceptable toxicity, including DLT. 
x Tagraxofusp-related anaphylaxis or Grade  3 hypersensitivity reaction. 
x Disease recurrence/progression. 
x Intercurrent illness that prevents further administration of tagraxofusp. 
x Patient non-compliance. 
x Occurrence of pregnancy. 
x Investigator’s decision. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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The reason for tagraxofusp discontinuation and the date of discontinuation should be recorded in 
the electronic case report form (eCRF). 
8.3.2 
Procedures and Follow-up after Treatment Discontinuation 
The evaluation during which the Investigator determines that tagraxofusp will be discontinued 
should be considered the End-of-Treatment Evaluation; all tests and procedures for the End-of-
Treatment Evaluation, as per the applicable Schedule of Events (Table 2 and Table 3 for Stage 2; 
Table 4 and Table 5 for Stage 3A) are to be performed. In addition, patients should be followed 
for a minimum of 30 days after the last infusion of tagraxofusp for assessment of AEs (including 
potential new AEs and potential change/resolution of existing AEs).  
If the patient is determined to have a response at the time of discontinuation, tumor assessments 
should continue to be performed as described in Section 11.12 until in the judgment of the 
Investigator, there is evidence of relapsed or progressive disease. Beyond the End-of-Treatment 
Evaluation and 30-day follow up (safety/AE assessment), it is requested that subsequent follow-
up occur approximately every 90 days after the last study drug dose for ascertainment of survival 
status.  
If the patient discontinues tagraxofusp treatment and also withdraws consent for collection of 
future information, no further evaluations should be performed and no additional data should be 
collected as part of the study. The Sponsor will only retain and use any data collected before 
withdrawal of consent. 
Please see Section 5.3 for recommendations concerning ongoing follow-up of patients alive with 
or without evidence of PD at the time of Study Completion/assessment of primary and critical 
secondary endpoints. 
9 
Schedules of Events: Stage 2 
The schedules of events for patients with MF in Stage 2 enrolled under Amendments 7 and 8 are 
presented in Table 2 and Table 3.  Enrollment in Stage 2 is closed, but CMML and MF patients 
who are already enrolled may continue receiving treatment. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Table 2: 
Stage 2: Schedule of Events for Screening and Cycles 1-4 
Tests and Observations 
Day -28 to 0 
Days 1-3  
(Up to Day 10 if Infusion(s) 
Held) 
Tagraxofusp Treatment 
Cycle 1 Day 
8±3(1) 
Day 21±3(2) 
Day 28±3, Then Every 
7±3 days (Only If Delayed 
End of Cycle: for Toxicity 
Resolution) 
Screening 
Pre-Infusion 
Tagraxofusp 
Infusion 
End of Cycle(2) 
Informed consent form3 
X 
 
 
 
 
 
Inclusion/exclusion criteria4 
X 
 
 
 
 
 
Medical history 
X 
 
 
 
 
 
ECOG performance status 
X 
X 
(Infusion 1, C1) 
 
 
X 
X 
Physical examination including assessment of 
hepatomegaly and splenomegaly 
X 
 
 
X 
X 
 
Pregnancy test5 
X 
 
 
 
 
 
Vital signs and weight6 
X 
X 
X 
X 
X 
X 
12-lead ECG7 
X 
X 
(MF Only: 
Infusion 1) 
(C1, C2) 
X 
(MF Only: 
Infusion 1)  
C1, C2) 
 
 
 
MUGA scan or 2-D Echocardiogram8 
X 
 
 
 
 
 
Hematology9 
X 
X 
 
X 
X 
X 
Serum chemistry10 
X 
X 
 
X 
X 
X 
Coagulation parameters: PT/INR, aPTT11 
X 
X 
 
X 
X 
X 
Urinalysis12 
X 
 
 
X 
X 
X 
Peripheral blood for flow cytometry 
X 
X 
(Infusion 1) 
 
X 
 
 
Bone marrow aspiration/biopsy13 
X 
 
 
 
X  
C1 and C414 
 
MRI or CT scan of abdomen15 
X 
 
 
 
X  
C1 and C414 
 
Pharmacokinetic sampling (patient with MF only)16 
 
X 
(Infusion 1) 
 
 
 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Tests and Observations 
Day -28 to 0 
Days 1-3  
(Up to Day 10 if Infusion(s) 
Held) 
Tagraxofusp Treatment 
Cycle 1 Day 
8±3(1) 
Day 21±3(2) 
Day 28±3, Then Every 
7±3 days (Only If Delayed 
End of Cycle: for Toxicity 
Resolution) 
Screening 
Pre-Infusion 
Tagraxofusp 
Infusion 
End of Cycle(2) 
(C1, C2) 
Immunogenicity sampling17 
 
X 
(Infusion 1) 
 
 
X 
 
Cytogenetic and molecular genetic testing 
X 
 
 
 
X 
C1 and C4 
 
Administration of premedications18 
 
X 
 
 
 
 
Tagraxofusp administration19 
 
 
X 
 
 
 
MPN-SAF TSS evaluation20 
X 
 
 
 
X 
 
Tumor response assessment21 
X 
 
 
 
X 
C1 and C4 
 
Vision assessment 
X 
 
 
 
X 
 
Prior/concomitant medications and therapies 
X 
X 
X 
X 
X 
X 
AE and SAE monitoring 
X 
X 
X 
X 
X 
X 
AE = adverse event; aPTT = activated partial thromboplastin time; CT = computed tomography; ECG = electrocardiogram; ECOG = Eastern Cooperative Oncology Group; 
INR = international normalized ratio; IV = intravenous; MPN-SAF TSS = Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score; MUGA = multigated 
acquisition; PK = pharmacokinetics; PT = prothrombin time; SAE = serious adverse event. 
1 
Day 8 visit is required for C1 only and must be performed at the site.  
2 
The end-of-cycle evaluations (Day 21 or thereafter) may also serve as the pre-infusion evaluations for the subsequent cycles; with the exception of vital signs, these 
assessments do not need to be duplicated on successive days unless there is an abnormality or other clinically relevant reason for repeat evaluation.  
3 
Refer to protocol Section 16.3 for details. 
4 
Refer to protocol Section 7 (study populations) for details. 
5 
Urine or serum pregnancy test must be performed within 1 week prior to treatment for WOCBP. 
6 
Height will be measured at screening only; weight does not need to be measured more than once per day, and should be measured pre-infusion on treatment days. Vital signs 
should be performed after patient is sitting for 3 to 5 minutes. During dosing period, vital signs should be taken immediately prior to infusion, at 0 (i.e., immediately after 
completion of infusion), and at 30 and 60 minutes post-infusion. 
7 
All patients will have a 12-lead ECG performed at the screening visit. For MF patients only, during the days when patients are undergoing PK sampling (Cycles 1 and 2, 
Infusion 1), an ECG will be performed at 3 distinct time points (triplicates) within 5 minutes (±5 minutes) prior to each PK sample collection pre-infusion and at 30 and 
60 minutes post-infusion. 
8 
A MUGA scan or 2-D ECHO to quantify LVEF must be completed within 28 days prior to start of first cycle of study drug.  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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9 
To be collected prior to tagraxofusp infusion if during dosing period. Hematology includes WBC count with differential, RBC count, hematocrit, Hb, platelet count and 
immature myeloid cells (including blasts + myelocytes +metamyelocytes + promyelocytes + nucleated red blood cells). 
10 To be collected prior to tagraxofusp infusion if during dosing period. Serum chemistry incudes electrolytes and additional parameters (equivalent to Chem-20): ALT, albumin, 
ALP, AST, bicarbonate, bilirubin, BUN, calcium, magnesium, chloride, creatinine, glucose, LDH, phosphate, potassium, sodium, total protein, uric acid, and CPK. See 
Appendix Section 18.3 for administration of albumin if serum albumin decreases to < 3.0 g/dL (< 30 g/L) during treatment days or in the immediate post-treatment period. 
11 In lieu of PT, INR may be measured.  
12 Urinalysis includes appearance, color, pH, specific gravity, ketones, leukocytes, protein, glucose, bilirubin, urobilinogen, and occult blood. Dipstick is acceptable. 
13 Morphology and WBC differential/blast count on aspirate. Baseline must be performed within 28 days prior to the first administration of tagraxofusp. Subsequent bone 
marrow aspirates and biopsies will be performed at the end of C1, C4, and then every 12 weeks (±7 days). Bone marrow evaluation should also be performed at End of 
Treatment including patients who discontinue study therapy prior to completion of C4; if a bone marrow evaluation was performed within 4 weeks prior to the end of 
treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated.  
14 Bone marrow and imaging studies are to be repeated at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter.  
15 A baseline MRI or CT scan must be performed within 28 days prior to the first administration of tagraxofusp. Subsequent imaging studies will be performed at the end of C1 
and C4 and then every 12 weeks (±7 days) until there is evidence of relapsed or progressive disease. Abdominal scan is required; evaluation of chest/pelvis may be obtained at 
the Investigator’s discretion. Scan must include measurement of spleen and liver volume. Imaging studies should also be performed at End of Treatment, including patients 
who discontinue study therapy prior to completion of C4; if a imaging was performed within 4 weeks prior to the end of treatment, a repeat evaluation does not need to be 
performed at this time, unless clinically indicated. Whenever clinically feasible, it is strongly requested that the same imaging modality (MRI or CT) at both baseline and 
subsequent timepoints be utilized for any given patient throughout their evaluation on-study. 
16 Peripheral blood (plasma) samples (6 mL each) will be collected from patients with MF only immediately prior to the start of the infusion of tagraxofusp, then at 0 (i.e., upon 
completion of infusion), 15, 30, 45, 60, 90 120, 180, and 240 minutes after completion of the infusion during Infusions 1 (i.e., Day 1) in C1 and C2.  
17 Peripheral blood (serum) samples (10 mL) will be collected for the detection of tagraxofusp reactive antibodies on Day 1 (pre-infusion) and Day 21 (the end of cycle 
collection may also serve as the pre-infusion collection for the subsequent cycle).  
18 Premedications administered 60 minutes (±15 minutes) before tagraxofusp treatment: Diphenhydramine 50 mg IV (or an equivalent dose of another H1-histamine antagonist); 
acetaminophen 650 mg orally (or equivalent dose of paracetamol); methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid); famotidine 20 mg IV (or 
an equivalent dose of another H2-histamine antagonist). 
19 Following treatment with premedication, tagraxofusp will be administered as a 15-minute infusion once daily for the first 3 consecutive days of a 21-day cycle. Individual 
tagraxofusp infusions may be delayed to allow for toxicity resolution, but all 3 infusions should be completed within 10 days. 
20 Patients with MF should complete the MPN-SAF TSS (10-question evaluation concerning symptoms/well-being during the prior week) during screening and in every 
treatment cycle, prior to receiving therapy on the subsequent cycle. The MPN-SAF TSS should also be completed at End of Treatment. 
21 Tumor assessments are to be performed during screening, at the end of C1 and C4, then every 12 weeks (±7 days) and at End of Treatment. These include the IWG-
MRT/ELN 2013 consensus report for MF and the IWG MDS 2016 consensus report for CMML.These are detailed in Section 11.12 and Section 18.1.  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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Table 3: 
Stage 2: Study Events Schedule for Cycle 5 and Beyond in Stage 2 
Procedures 
Cycle 5 and Beyond 
Cycles 5 
and 
Beyond2 
12 Weeks 
(i.e., every 
3 cycles) 
±7 Days 
End-of-
treatment 
Safety: 
Through 
30 Days 
After Last 
Infusion 
Survival: 
Every 
90 Days 
After Last 
Infusion 
Days 1-3 (Up to Day 10 if 
Infusion(s) Held) 
Tagraxofusp Treatment 
Day 
28±31 
 
 
 
Pre-Infusion 
Infusion 
End of Cycle1 
 
 
Concomitant medications/therapies  
X 
 
X 
 
 
X 
 
 
AE and SAE monitoring 
X 
X 
X 
 
X 
X 
X 
 
ECOG performance status 
 
 
X 
 
 
X 
 
 
Physical examination including assessment of 
hepatomegaly and splenomegaly 
 
 
X 
 
 
X 
 
 
Vital signs and weight3 
X 
X 
X 
 
 
X 
 
 
Hematology4 
X 
 
X 
 
 
X 
 
 
Serum chemistry5 
X 
 
X 
 
 
X 
 
 
Coagulation parameters: PT/INR, aPTT6 
X 
 
X 
 
 
X 
 
 
Urinalysis7 
 
 
X 
 
 
 
 
 
Peripheral blood for flow cytometry 
X 
(Infusion 1) 
 
 
 
 
X 
 
 
Bone marrow aspiration/biopsy8 
 
 
 
 
X9 
X 
 
 
MRI or CT scan of abdomen10 
 
 
 
 
X9 
X 
 
 
Immunogenicity sampling11 
 
 
X 
 
 
X 
X 
X12 
Cytogenetic and molecular genetic testing 
 
 
 
 
X 
X 
 
 
Administration of premedications13 
X 
 
 
 
 
 
 
 
Administration of Tagraxofusp14 
 
X 
 
 
 
 
 
 
MPN-SAF TSS evaluation15 
 
 
X 
 
 
X 
 
 
Vision assessment 
 
 
X 
 
 
X 
 
 
Tumor response assessment16 
 
 
 
 
X10 
X 
 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
 
Amendment 9 (Final): 30 September 2021 
48 
CONFIDENTIAL 
Procedures 
Cycle 5 and Beyond 
Cycles 5 
and 
Beyond2 
12 Weeks 
(i.e., every 
3 cycles) 
±7 Days 
End-of-
treatment 
Safety: 
Through 
30 Days 
After Last 
Infusion 
Survival: 
Every 
90 Days 
After Last 
Infusion 
Days 1-3 (Up to Day 10 if 
Infusion(s) Held) 
Tagraxofusp Treatment 
Day 
28±31 
 
 
 
Pre-Infusion 
Infusion 
End of Cycle1 
 
 
Long-term follow-up12 
 
 
 
 
 
 
X 
X 
AE = adverse event; aPTT = activated partial thromboplastin time; CT = computed tomography; ECG = electrocardiogram; ECOG = Eastern Cooperative Oncology Group; INR = 
international normalized ratio; MPN-SAF TSS = Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score; PT = prothrombin time; SAE = serious adverse 
event. 
1 
The end-of-cycle evaluations (Day 28 or thereafter) may also serve as the pre-infusion evaluations for the subsequent cycles; with the exception of vital signs, these do not 
need to be duplicated on successive days unless there is an abnormality or other clinically relevant reason for repeat evaluation. 
2 
Disease evaluation via bone marrow aspirate/biopsy and/or imaging studies (when relevant) will occur every 12 weeks (±7 days). The frequency of bone marrow evaluation 
may be reduced (obtained less frequently) if peripheral blood, clinical and/or  imaging assessments indicate clinical stability, as per the Investigator’s discretion in 
consultation with the Medical Monitor. The frequency of imaging assessments may also be reduced if clinical/laboratory findings indicate stability, as per the Investigator’s 
discretion in consultation with the Medical Monitor.  
3 
Height will be measured at screening only; weight does not need to be measured more than once per day, and should be measured pre-infusion on treatment days. Vital signs 
should be performed after patient is sitting for 3 to 5 minutes. If during dosing period, vital signs should be taken immediately prior to infusion, at 0 (i.e., immediately after 
completion of infusion), and at 30 and 60 minutes post-infusion. 
4 
To be collected prior to tagraxofusp infusion if during dosing period. Hematology includes WBC count with differential, RBC count, hematocrit, hemoglobin, platelet count 
and immature myeloid cells (including blasts + myelocytes +metamyelocytes + promyelocytes + nucleated red blood cells). 
5 
To be collected prior to tagraxofusp infusion if during dosing period. Serum chemistry incudes electrolytes and additional parameters (equivalent to Chem-20): ALT, albumin, 
alkaline phosphatase, AST, bicarbonate, bilirubin, BUN, calcium, magnesium, chloride, creatinine, glucose, LDH, phosphate, potassium, sodium, total protein, uric acid, and 
CPK. See Section 18.3 for administration of albumin if serum albumin decreases to < 3.0 g/dL (< 30 g/L) during treatment days or in the immediate post-treatment period. 
6 
In lieu of PT, INR may be measured. 
7 
Urinalysis includes appearance, color, pH, specific gravity, ketones, leukocytes, protein, glucose, bilirubin, urobilinogen, and occult blood. Dipstick is acceptable. 
8 
Morphology and WBC differential /blast count on aspirate. In general, bone marrow aspirates and biopsies and peripheral blood samples will be performed at the end of C1 
and C4 and then every 12 weeks (±7 days) thereafter. Bone marrow evaluation should also be performed at End of Treatment; if a bone marrow evaluation was performed 
within 4 weeks prior to the end of treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated.  
9 
Bone marrow and imaging studies are to be repeated at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter. 
10 Imaging studies will be performed at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter until there is evidence of relapsed or progressive disease. Abdominal 
scan is required; evaluation of chest/pelvis may be obtained at the Investigator’s discretion. Scan must include measurement of spleen and liver volume. Subsequent to Week 
24, for patients receiving ongoing therapy (or those who discontinue therapy but are without evidence of PD and continue to be evaluated in ongoing follow-up) the frequency 
of imaging studies may be reduced (obtained less frequently) if peripheral blood and/or clinical assessments indicate clinical stability, as per the Investigator’s discretion, in 
consultation with the Medical Monitor. Imaging studies should also be performed at End of Treatment; if imaging studies were performed within 4 weeks prior to the end of 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
 
Amendment 9 (Final): 30 September 2021 
49 
CONFIDENTIAL 
treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated. Whenever clinically feasible, it is strongly requested that the same 
imaging modality (MRI or CT) at both baseline and subsequent timepoints be utilized for any given patient throughout their evaluation on-study. 
11 Peripheral blood (serum) samples (10 mL) will be collected for the detection of tagraxofusp reactive antibodies at the completion of every cycle and at specified points 
thereafter. 
12 Patients will be followed for survival approximately every 90 days, until assessment of the primary objective for the study is complete for all treated patients; please consult 
the appropriate protocol section for description of situations in which survival and other data may be collected following study completion. Patients who undergo SCT will be 
followed for the occurrence of veno-occlusive disease as part of long-term follow-up. A blood sample for immunogenicity studies will be collected at least 16 weeks to up to 
20 weeks after the last tagraxofusp dose. 
13 Premedications administered 60 minutes (±15 minutes) before tagraxofusp treatment: Diphenhydramine 50 mg IV (or an equivalent dose of another H1-histamine antagonist); 
acetaminophen 650 mg orally (or equivalent dose of paracetamol); methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid); famotidine 20 mg IV (or 
an equivalent doses of another H2-histamine antagonist). 
14 Following treatment with premedication, tagraxofusp will be administered as a 15-minute infusion once daily for the first 3 consecutive days of a 28-day cycle. Individual 
tagraxofusp infusions may be delayed to allow for toxicity resolution, but all 3 infusions should be completed within 10 days. 
15 Patients with MF should complete the MPN-SAF TSS (10-question evaluation concerning symptoms/well-being during the prior week) with every treatment cycle, prior to 
receiving therapy on the subsequent cycle. The MPN-SAF TSS should also be completed at End of Treatment. 
16 Tumor response assessments are to be conducted every 12 weeks (±7 days) and at End of Treatment, detailed in Section 11.12 and Section 18.1. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
 
Amendment 9 (Final): 30 September 2021 
50 
10 
Schedules of Events: Stage 3A 
The schedules of events for patient with CMML in Stage 3A are presented in Table 4 and 
Table 5. 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
51 
CONFIDENTIAL 
Table 4: 
Stage 3A: Study Events Schedule for Screening and Cycles 1-4 for Patients with CMML 
Procedures 
Day -28 to 0 
Days 1-3  
(Up to Day 10 if Infusion(s) 
Held) 
Tagraxofusp Treatment 
Cycle 1 
Day 8±31 
Day 21±32 
Day 28±3, Then Every 
7±3 days (Only if Delayed 
End of Cycle: for Toxicity 
Resolution) 
Screening 
Pre-Infusion 
Tagraxofusp 
Infusion 
End of Cycle2 
Informed consent form3 
X 
 
 
 
 
 
Inclusion/exclusion criteria3 
X 
 
 
 
 
 
Medical history  
X 
 
 
 
 
 
12-lead ECG 
X 
 
 
 
 
 
ECOG performance status 
X 
X 
(Infusion 1, C1) 
 
 
X 
X 
Physical examination, including assessment for 
hepatomegaly and splenomegaly 
X 
 
 
X 
X 
 
Pregnancy test4 
X 
 
 
 
 
 
Vital signs and weight5 
X 
X 
X 
X 
X 
X 
MUGA scan or 2-D Echocardiogram6 
X 
 
 
 
 
 
Hematology7 
X 
X 
 
X 
X 
X 
Serum chemistry8 
X 
X 
 
X 
X 
X 
Coagulation parameters: PT/INR, aPTT9 
X 
X 
 
X 
X 
X 
Peripheral blood for flow cytometry 
X 
X 
(Infusion 1) 
 
X 
 
 
Peripheral blood for IL-10 testing 
 
X 
(Infusion 1, C1) 
 
 
X 
C1 and C4 
 
Peripheral blood for translational studies (select centers) 
 
X 
(Infusion 1, C1) 
 
 
X 
C1 and C4 
 
Bone marrow aspiration/biopsy10 
X 
 
 
 
X  
C1 and C411 
 
MRI or CT for assessment of hepatomegaly and 
splenomegaly 12 
X 
 
 
 
X  
C1 and C411 
 
Immunogenicity sampling13 
 
X 
(Infusion 1) 
 
 
X 
 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
52 
CONFIDENTIAL 
Procedures 
Day -28 to 0 
Days 1-3  
(Up to Day 10 if Infusion(s) 
Held) 
Tagraxofusp Treatment 
Cycle 1 
Day 8±31 
Day 21±32 
Day 28±3, Then Every 
7±3 days (Only if Delayed 
End of Cycle: for Toxicity 
Resolution) 
Screening 
Pre-Infusion 
Tagraxofusp 
Infusion 
End of Cycle2 
Cytogenetic and molecular genetic testing 
X 
 
 
 
X 
C1 and C4 
 
Administration of premedications14 
 
X 
 
 
 
 
Tagraxofusp administration15 
 
 
X 
 
 
 
MPN-SAF TSS evaluation16 
X 
 
 
 
X 
 
Baseline/tumor response assessment17 
X 
 
 
 
X 
C1 and C411 
 
Vision assessment 
X 
 
 
 
X 
 
Prior/concomitant medications/therapies (including 
concomitant platelet and RBC transfusions) 
X 
X 
X 
X 
X 
X 
AE and SAE monitoring 
X 
X 
X 
X 
X 
X 
AE = adverse event; aPTT = activated partial thromboplastin time; CT = computed tomography; ECG = electrocardiogram; ECOG = Eastern Cooperative Oncology Group; 
INR = international normalized ratio; MPN-SAF TSS = Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score; MUGA = multigated acquisition; PT = 
prothrombin time; SAE = serious adverse event. 
1 
Day 8 visit is required for C1 only and must be performed at the site.  
2 
The end-of-cycle evaluations (Day 21 or thereafter) may also serve as the pre-infusion evaluations for the subsequent cycles; with the exception of vital signs, these 
assessments do not need to be duplicated on successive days unless there is an abnormality or other clinically relevant reason for repeat evaluation.  
3 
Refer to protocol Section 16.3 (Patient Information and Informed Consent) and Section 7 (Populations to be Studied) for details. 
4 
Urine or serum pregnancy test must be performed within 1 week prior to treatment for WOCBP. 
5 
Height will be measured at screening only; weight does not need to be measured more than once per day, and should be measured pre-infusion on treatment days. Vital signs 
should be performed after patient is sitting for 3 to 5 minutes. During dosing period, vital signs should be taken immediately prior to infusion, at 0 (i.e., immediately after 
completion of infusion), and at 30 and 60 minutes post-infusion. 
6 
A MUGA scan or 2-D ECHO to quantify LVEF must be completed within 28 days prior to start of first cycle of study drug.  
7 
To be collected prior to tagraxofusp infusion if during dosing period. Hematology includes WBC count with differential, RBC count, hematocrit, Hb, platelet count, and 
immature myeloid cells (including blasts + myelocytes +metamyelocytes + promyelocytes + nucleated red blood cells) (for safety assessments as well as efficacy assessments 
at the end of each cycle in between bone marrow assessments). 
8 
To be collected prior to tagraxofusp infusion if during dosing period. Serum chemistry incudes electrolytes and additional parameters (equivalent to Chem-20): ALT, albumin, 
ALP, AST, bicarbonate, bilirubin, BUN, calcium, magnesium, chloride, creatinine, glucose, LDH, phosphate, potassium, sodium, total protein, uric acid, and CPK. See 
Appendix Section 18.3 for administration of albumin if serum albumin decreases to < 3.0 g/dL (< 30 g/L) during treatment days or in the immediate post-treatment period. 
9 
In lieu of PT, INR may be measured.  
10 Morphology and WBC differential/blast count on aspirate. Baseline must be performed within 28 days prior to the first administration of tagraxofusp. Subsequent bone 
marrow aspirates and biopsies will be performed at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter. Bone marrow evaluation should also be performed at 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
53 
CONFIDENTIAL 
End of Treatment including patients who discontinue study therapy prior to completion of C4; if a bone marrow evaluation was performed within 4 weeks prior to the end of 
treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated.  
11 Bone marrow aspirate and imaging studies are to be repeated at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter. 
12 A baseline MRI or CT scan must be performed within 28 days prior to the first administration of tagraxofusp. Subsequent imaging studies will be performed at the end of C1 
and C4 and then every 12 weeks (±7 days) until there is evidence of relapsed or progressive disease. Abdominal scan is required; evaluation of chest/pelvis may be obtained at 
the Investigator’s discretion. Scan must include measurement of spleen and liver volume. Subsequent to Week 24, for patients receiving ongoing therapy (or those who 
discontinue therapy but are without evidence of PD and continue to be evaluated in ongoing follow-up) the frequency of imaging studies may be reduced (obtained less 
frequently) if peripheral blood and/or clinical assessments indicate clinical stability, as per the Investigator’s discretion, in consultation with the Medical Monitor. Imaging 
should also be performed at End of Treatment, including patients who discontinue study therapy prior to completion of C4; if a imaging was performed within 4 weeks prior 
to the end of treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated. Whenever clinically feasible, it is strongly requested that the 
same imaging modality (MRI or CT) at both baseline and subsequent timepoints be utilized for any given patient throughout their evaluation on-study. 
13 Peripheral blood (serum) samples (10 mL) will be collected for the detection of tagraxofusp reactive antibodies on Day 1 (pre-infusion) and Day 21 (the end of cycle 
collection may also serve as the pre-infusion collection for the subsequent cycle).  
14 Premedications administered 60 minutes (±15 minutes) before tagraxofusp treatment: Diphenhydramine 50 mg IV (or an equivalent dose of another H1-histamine antagonist); 
acetaminophen 650 mg orally (or equivalent dose of paracetamol); methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid); famotidine 20 mg IV (or 
an equivalent dose of another H2-histamine antagonist). 
15 Following treatment with premedication, tagraxofusp will be administered as a 15-minute infusion once daily for the first 3 consecutive days of a 21-day cycle. Individual 
tagraxofusp infusions may be delayed to allow for toxicity resolution, but all 3 infusions should be completed within 10 days. 
16 Patients complete the MPN-SAF TSS (10-question evaluation concerning symptoms/well-being during the prior week) during screening and with every treatment cycle, prior 
to receiving therapy on the subsequent cycle. The MPN-SAF TSS should also be completed at End of Treatment. 
17 Tumor assessments will be performed during screening, at the end of C1 and C4, then every 12 weeks (±7 days) and at End-of-Treatment per the 2015 MDS/MPN criteria, as 
detailed in Section 11.12 and Section 18.1. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
54 
CONFIDENTIAL 
Table 5: 
Stage 3A: Study Events Schedule for Cycle 5 and Beyond for Patients with CMML 
Procedures 
Cycle 5 and Beyond 
Cycles 5 and 
Beyond2 
12 Weeks 
(i.e., every 
3 cycles) 
±7 Days 
End-of-
treatment 
Safety: 
Through 
30 Days 
After Last 
Infusion 
Survival: 
Every 
90 Days 
After Last 
Infusion 
Days 1-3 (Up to Day 10 
if Infusion(s) Held) 
Tagraxofusp Treatment 
Day 
28±31 
Pre-Infusion 
Infusion 
End of Cycle1 
Concomitant medications/therapies (including 
platelet and RBC transfusions)  
X 
 
X 
 
X 
 
 
AE and SAE monitoring 
X 
X 
X 
X 
X 
X 
 
ECOG performance status 
 
 
X 
 
X 
 
 
Physical examination including assessment of 
hepatomegaly and splenomegaly 
 
 
X 
 
X 
 
 
Vital signs and weight3 
X 
X 
X 
 
X 
 
 
Hematology4 
X 
 
X 
 
X 
 
 
Serum chemistry5 
X 
 
X 
 
X 
 
 
Coagulation parameters: PT/INR, aPTT6 
X 
 
X 
 
X 
 
 
Peripheral blood for flow cytometry 
X 
(Infusion 1) 
 
 
 
X 
 
 
Bone marrow aspiration/biopsy7 
 
 
 
X8 
X 
 
 
MRI or CT for assessment of hepatomegaly and 
splenomegaly 9 
 
 
 
X8 
X 
 
 
Immunogenicity sampling10 
 
 
X 
 
X 
X 
X11 
Cytogenetic and molecular genetic testing 
 
 
 
X 
X 
 
 
Administration of premedications12 
X 
 
 
 
 
 
 
Administration of Tagraxofusp13 
 
X 
 
 
 
 
 
MPN-SAF TSS evaluation14 
 
 
X 
 
X 
 
 
Vision assessment 
 
 
X 
 
X 
 
 
Tumor response assessment15 
 
 
 
X8 
X 
 
 
Long-term follow-up11 
 
 
 
 
 
X 
X 
AE = adverse event; aPTT = activated partial thromboplastin time; CT = computed tomography; ECG = electrocardiogram; ECOG = Eastern Cooperative Oncology Group; 
INR = international normalized ratio; MPN-SAF TSS = Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score; PT = prothrombin time; SAE = serious 
adverse event. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
55 
CONFIDENTIAL 
1 
The end-of-cycle evaluations (Day 28 or thereafter) may also serve as the pre-infusion evaluations for the subsequent cycles; with the exception of vital signs, these 
assessments do not need to be duplicated on successive days unless there is an abnormality or other clinically relevant reason for repeat evaluation. 
2 
Disease evaluation via bone marrow aspirate/biopsy and/or imaging studies (when relevant) will occur every 12 weeks (±7 days). The frequency of bone marrow evaluation 
may be reduced (obtained less frequently) if peripheral blood, clinical and/or imaging assessments indicate clinical stability, as per the Investigator’s discretion in consultation 
with the Medical Monitor. The frequency of imaging assessments may also be reduced if clinical/laboratory findings indicate stability, as per the Investigator’s discretion in 
consultation with the Medical Monitor.  
3 
Height will be measured at screening only; weight does not need to be measured more than once per day, and should be measured pre-infusion on treatment days. Vital signs 
should be performed after patient is sitting for 3 to 5 minutes. If during dosing period, vital signs should be taken immediately prior to infusion, at 0 (i.e., immediately after 
completion of infusion), and at 30 and 60 minutes post-infusion. 
4 
To be collected prior to tagraxofusp infusion if during dosing period. Hematology includes WBC count with differential, RBC count, hematocrit, hemoglobin, platelet count, 
and immature myeloid cells (including blasts + myelocytes +metamyelocytes + promyelocytes + nucleated red blood cells) (for safety assessments as well as efficacy 
assessments at the end of each cycle in between bone marrow assessments).  
5 
To be collected prior to tagraxofusp infusion if during dosing period. Serum chemistry incudes electrolytes and additional parameters (equivalent to Chem-20): ALT, albumin, 
alkaline phosphatase, AST, bicarbonate, bilirubin, BUN, calcium, magnesium, chloride, creatinine, glucose, LDH, phosphate, potassium, sodium, total protein, uric acid, 
chloride, and CPK. See Appendix Section 18.3 for administration of albumin if serum albumin decreases to < 3.0 g/dL (< 30 g/L) during treatment days or in the immediate 
post-treatment period. 
6 
In lieu of PT, INR may be measured. 
7 
Morphology and WBC differential /blast count on aspirate. In general, bone marrow aspirates and biopsies will be performed at the end of C1 and C4 and then every 
12 weeks (±7 days) thereafter. Bone marrow evaluation should also be performed at End of Treatment; if a bone marrow evaluation was performed within 4 weeks prior to the 
end of treatment, a repeat evaluation does not need to be performed at this time, unless clinically indicated.  
8 
Bone marrow aspirate and imaging studies are to be repeated at the end of C1 and C4 and then every 12 weeks (±7 days) thereafter. 
9 
Imaging studies will be performed at the end of C1 and C4 and then every 12 weeks (±7 days) until there is evidence of relapsed or progressive disease. Abdominal scan is 
required; evaluation of chest/pelvis may be obtained at the Investigator’s discretion. Scan must include measurement of spleen and liver volume. Imaging studies should also 
be performed at End of Treatment; if imaging was performed within 4 weeks prior to the end of treatment, a repeat evaluation does not need to be performed at this time, 
unless clinically indicated. Whenever clinically feasible, it is strongly requested that the same imaging modality (MRI or CT) at both baseline and subsequent timepoints be 
utilized for any given patient throughout their evaluation on-study. 
10 Peripheral blood (serum) samples (10 mL) will be collected for the detection of tagraxofusp reactive antibodies at the completion of every cycle and at specified points 
thereafter. 
11 Patients will be followed for survival approximately every 90 days, until assessment of the primary objective for the study is complete for all treated patients; please consult 
the appropriate protocol section for description of situations in which survival and other data may be collected following study completion. Patients who undergo SCT will be 
followed for the occurrence of veno-occlusive disease as part of long-term follow-up. A blood sample for immunogenicity studies will be collected at least 16 weeks to up to 
20 weeks after the last tagraxofusp dose. 
12 Premedications administered 60 minutes (±15 minutes) before tagraxofusp treatment: Diphenhydramine 50 mg IV (or an equivalent dose of another H1-histamine antagonist); 
acetaminophen 650 mg orally (or equivalent dose of paracetamol); methylprednisolone 50 mg IV (or an equivalent dose of another corticosteroid); famotidine 20 mg IV (or 
an equivalent doses of another H2-histamine antagonist). 
13 Following treatment with premedication, tagraxofusp will be administered as a 15-minute infusion once daily for the first 3 consecutive days of a 28-day cycle. Individual 
tagraxofusp infusions may be delayed to allow for toxicity resolution, but all 3 infusions should be completed within 10 days. 
14 Patients should complete the MPN-SAF TSS (10-question evaluation concerning symptoms/well-being during the prior week) with every treatment cycle, prior to receiving 
therapy on the subsequent cycle. The MPN-SAF TSS should also be completed at End of Treatment. 
15 Tumor response assessments are to be conducted every 12 weeks (±7 days) and at End of Treatment, detailed in Section 11.12, and Section 18.1. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
56 
11 
Study Procedures 
11.1 
Patient Selection 
Patients with CMML who meet the inclusion/exclusion criteria will be recruited for enrollment 
into the study. Patients will be advised of the clinical protocol by the Investigator. If the patient 
is interested and is potentially eligible for participation in the study, he/she will be provided with 
the informed consent form (ICF) to review and sign. The ICF includes a detailed explanation of 
the study design and the potential risks and benefits of treatment. Patients who agree to 
participate in the study will be provided with a copy of the signed consent form; the original 
signed consent document will be filed in the patient’s medical record. Only eligible and 
consenting patients will be entered into the study. No study procedures will be performed until 
the patient’s written informed consent is obtained. 
Patients will be screened by the Investigator or study nurse/coordinator prior to study entry. All 
patients enrolled on the study will be entered into a patient registration log at each site. Each 
screened patient will be assigned a sequential patient/study identification number with digits 
indicating site number and patient study number (e.g., XX-YYY, where XX denotes site number 
and YYY denotes patient study number as assigned at screening). Original screening records and 
source documents should be kept for all patients, including those who fail to meet the study 
eligibility requirements and any completed eCRFs should be retained for monitoring and 
auditing. Each patient’s data obtained from subsequent evaluations should be recorded and 
evaluated in the source documents and eCRF. Prior to treatment, the Investigator will re-confirm 
patient eligibility criteria and assignment of the correct patient study number. 
11.2 
Medical History 
Medical history includes current and past medical conditions and smoking history, date of MPN 
diagnosis, history of infections related to primary disease, prior treatment, response to prior 
treatment, and date of relapse, if applicable. Information concerning any prior malignancy 
diagnoses with particular focus on cytotoxic therapies received for prior malignancies (e.g., 
dates/duration of anthracycline for prior breast cancer) is to be collected whenever feasible. 
11.3 
Prior and Concomitant Medication 
Medications taken within 28 days prior to the first study drug dose and throughout the study are 
to be collected and recorded. For patients with CMML, all transfusions (pRBC and platelets) 
within 8 weeks prior to the first tagraxofusp dose also are to be recorded. For patients with MF, 
all transfusions (pRBC and platelets) within 12 weeks prior to the first tagraxofusp dose are to be 
recorded.  
11.4 
ECOG Performance Status 
See Section 18.2 for the ECOG-PS scoring guide. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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11.5 
Physical Examination 
Physical examination includes evaluation by body system, weight, and height (screening only) 
performed at screening, and at subsequent time points as indicated in the applicable Schedules of 
Events (Table 2 and Table 3 for Stage 2; Table 4 and Table 5 for Stage 3A). Note that physical 
examination includes assessment for hepatomegaly and splenomegaly by palpation, with 
findings records as centimeters below the right costal margin and left costal margin, respectively. 
Of note, a spleen response by palpation must be confirmed by imaging studies to show reduction 
in spleen volume (or liver volume in splenectomized patients; refer to the response criteria 
outlined in Appendix 18).  
11.6 
Vital Signs 
Vital signs include temperature, heart rate, respiration rate, pulse oximetry, and blood pressure. 
Collection should occur after the patient has been sitting for 3-5 minutes. Vital signs are to be 
measured at the time points indicated in the applicable Schedules of Events (Table 2 and Table 3 
for Stage 2; Table 4 and Table 5 for Stage 3A). 
11.7 
Electrocardiograms 
All patients will have a 12-lead ECG performed during screening. 
For patients with MF in Stage 2, during days when pharmacokinetic (PK) samples are drawn 
(C1 and C2, Infusion 1), an ECG will be performed at 3 distinct time points (triplicates) 
within 5 minutes (±5 minutes) prior to selected PK sample collections as follows: pre-infusion, 
and at 30 and 60 minutes post-infusion. An ECG should be performed after the patient is supine 
for 5 minutes.  
11.8 
Imaging Studies 
After all other entry criteria have been met for an individual patient, a baseline spleen (and liver) 
volume assessment by MRI or CT scan is required and should be performed within 28 days prior 
to the first administration of tagraxofusp. Subsequent imaging studies will be performed as 
indicated in the applicable Schedules of Events (Table 2 and Table 3 for Stage 2; Table 4 and 
Table 5 for Stage 3A). An abdominal scan is required; evaluation of chest/pelvis may be 
obtained at the Investigator’s discretion.  
MRI is the preferred modality as it provides an objective measure of spleen (and liver) volume 
and does not expose study subjects to ionizing radiation. CT may be used where MRI is not 
available or suitable for study subjects. Imaging studies will be reviewed locally.  
Whenever clinically feasible, it is strongly requested that the same imaging modality at both 
baseline and subsequent time points be utilized for any given patient throughout their evaluations 
on-study.  

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
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11.9 
Cardiac Function: MUGA/2-D Echocardiogram 
A MUGA scan or 2-D ECHO to quantify LVEF must be completed during screening within 
28 days prior to start of first cycle of study drug. A minimum LVEF is stipulated as a criterion 
for study inclusion (see Section 7.1.1). 
11.10 Clinical Laboratory Tests 
The following assessments should be done at the time points indicated in the applicable 
Schedules of Events (Table 2 and Table 3 for Stage 2; Table 4 and Table 5 for Stage 3A) and 
processed by the local laboratory. 
x Hematology: Scheduled hematology assessments should at minimum include WBC count, 
differential WBC (lymphocytes, monocytes, basophils, eosinophils, and neutrophils), RBC 
count, hematocrit, Hb, platelet count and immature myeloid cells (including blasts + 
myelocytes + metamyelocytes + promyelocytes + nucleated red blood cells) (for safety 
assessments as well as for efficacy assessments at the end of each cycle in between bone 
marrow assessments). 
x Serum albumin: May be a component of the serum chemistry panel. See Appendix 
Section 18.3 for administration of albumin if serum albumin decreases to < 3.0 g/dL during 
treatment days or in the immediate post-treatment period. 
x Serum chemistry and electrolytes: ALT, albumin, alkaline phosphatase (ALP), AST, 
bicarbonate, bilirubin (total, direct, and indirect), BUN, calcium, chloride, CPK, creatinine, 
glucose, LDH, magnesium, phosphate, potassium, sodium, total protein, and uric acid. 
x Coagulation parameters: PT and/or INR and aPTT. 
x Urinalysis (MF patients only): Appearance, color, pH, specific gravity, ketones, leukocytes, 
protein, glucose, bilirubin, urobilinogen, and occult blood. 
Detailed instructions for collecting, processing, storing, and shipping the samples are provided in 
the Laboratory Manual.  
11.10.1 Urine or Serum Pregnancy Test 
A urine or serum pregnancy test will be performed locally within 1 week prior to treatment for 
WOCBP. The pregnancy test should be performed at the clinical research site and processed by 
the local laboratory. 
11.11 Vision Assessment 
All patients will be questioned regarding any changes from baseline in visual acuity and/or color 
vision. Patients who have experienced any  Grade 2 study drug-related changes in vision 
(National Cancer Institute [NCI] Common Terminology Criteria for Adverse Events [CTCAE], 
v4.03, Grade) will have an ophthalmologic consultation and/or examination performed. In the 
event any abnormalities are detected, the patient will be followed up as per the recommendations 

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of the consulting ophthalmologist. Management of treatment-related ocular disorders with 
inflammatory characteristics should include corticosteroid eye drops and/or other measures, as 
indicated by an ophthalmologist. In the setting of persistent study drug-related ocular disorders 
 Grade 2, consultation with the study’s Medical Monitor is required. 
11.12 Tumor Assessments 
Tumor assessments must be performed at baseline within 28 days prior to the first administration 
of tagraxofusp, and on the scheduled specified in Table 2 and Table 3 for Stage 2 and Table 4 
and Table 5 for Stage 3A. 
Response assessment is performed by means of the following:  
x MF (Stage 2): The IWG-MRT/ELN 2013 criteria (see Table 6 in Appendix 
Section 18.1).  
x CMML (Stage 2): The IWG MDS 2006 criteria (see Table 7 in Appendix Section 18.1). 
x CMML (Stage 3A): MDS/MPN 2015 criteria (see Table 8 in Appendix Section 18.1).  
After Baseline, tumor response assessments are performed at the end of C1 and C4 and then 
every 12 weeks (±7 days) thereafter, at End-of-Treatment, and at other timepoints if clinically 
warranted. 
11.12.1 Cytogenetic and Molecular Genetic Testing 
Cytogenetic testing should be done on bone marrow aspirate samples and 20 metaphases 
assessed, when possible. Peripheral blood can be used for the analysis in patients with high 
circulating blast counts. The number of metaphases counted and analyzed, and abnormal 
karyotype will be collected in the CRF. 
Molecular genetic testing by next-generation sequencing (NGS) will be done on peripheral blood 
or bone marrow aspirate samples and will be analyzed for the following mutations: 
x Patients with MF: JAK2V617F, CALR, and MPL. For ‘triple-negative’ MF patients, 
complementary clonal markers, such as ASXL1, EZH2, IDH1, IDH2, and SRSF2 are 
recommended; additional clonal markers such as TP53, TET2, DNMT3A, and CBL are 
useful for risk-stratification. 
x Patients with CMML: TET2, ASXL1, DNMT3A, EZH2, IDH1, IDH2, BCOR, SRSF2, 
U2AF1, SF3B1, ZRSR2, CBL, KRAS, NRAS, NF1, JAK2, RUNX1, SETBP1, NPM1, and 
FLT3 are recommended by the ELN/EHA 2018 guidelines for patients being considered 
for active treatments, including stem cell transplant. Of these genes, an analysis of the 
following 4 genes is considered mandatory for risk assessment according to accepted risk 
scoring systems: ASXL1, NRAS, RUNX1, and SETBP1.  
Detailed instructions for collecting, processing, storing, and shipping the samples are provided in 
the Laboratory Manual.  

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11.12.2 Bone Marrow Examinations Including Biological / Target / Correlative Studies 
Bone marrow aspirate and biopsy samples will be collected during screening within 28 days 
prior to the first administration of tagraxofusp and at the end of C1 and C4 and then every 12 
weeks (±7 days) thereafter, and at End-of-Treatment. Plasmacytoid dendritic cells (pDCs) and 
CD123 expression will be assessed by flow cytometry and immunohistochemistry in all bone 
marrow samples by a central laboratory. 
Consult the Laboratory Manual regarding information on the collection, handling, labeling, and 
shipping of samples. 
11.13 Immunogenicity Studies 
Peripheral blood samples (10 mL) will be collected (serum red top tube, no additive) for the 
detection and characterization of tagraxofusp reactive antibodies according to the schedule 
provided below.  
x C1-4: Day 1 (pre-infusion) and Day 21 (± 3 days). 
x C5 and beyond: End of cycle (D28 [± 3 days]). 
x End-of-Treatment. 
x 30 days after last infusion. 
x At least 16 weeks and to up to 20 weeks after last infusion. 
x If there are clinical manifestations suggesting either an infusion related reaction or drug 
hypersensitivity, an immunogenicity sample should be obtained, as indicated in 
Section 8.2.3.2. 
Detailed instructions for collecting, processing, storing, and shipping the samples will be 
provided in the Laboratory Manual. 
11.14 Translational Studies/Exploratory assessments 
x Flow cytometry: Cells expressing high levels of CD123 have been described in the 
bone marrow of CMML patients and an excess of CD123 expressing pDCs has been 
shown to correlate with regulatory T cell accumulation and an increased risk of acute 
leukemia transformation (Lucas 2019). Additionally, CD14+/CD16- monocytes have 
been indicated to be a specific biomarker that distinguish CMML from confounding 
diagnoses (Selimoglu-buet 2015). pDCs in addition to leukocyte populations (MF) 
and monocyte subsets (CMML) will be assessed centrally in bone marrow and 
peripheral blood by flow cytometry. Samples will be collected at the following time 
points: 
o Screening or C1D1 (pre-infusion) 
o All Cycles: Day 1 

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o C1: Day 8 
o End of Treatment 
x Cytokine IL-10: It has been observed that CMML patients with decreased IL-10 
expression have poor overall survival when compared to patients with elevated 
expression of IL-10 (Niyongere 2019), which suggests that cytokine IL-10 can be a 
prognostic marker of overall survival (Niyongere 2019). Peripheral blood samples 
will be collected for the detection of the cytokine IL-10 for CMML patients at the 
following time points. 
o C1: Day 1 (pre-infusion) and Day 21 (± 3 days) 
o C4: End of cycle (Day 21 [± 3 days]). 
x In addition to central laboratory analysis of CD123 and monocyte cell populations, an 
exploratory analysis of CD14+/CD16- flow cytometry, CYTOF (Mass cytometry), 
next generation sequencing in CMML patients will be examined at selected sites at 
the following time points: 
o C1: Day 1 (pre-infusion) and Day 21 (end of cycle) 
o C4: Day 21 (end of cycle) 
Detailed instructions for collecting, processing, storing, and shipping the samples will be 
provided in the Laboratory Manual.  
12 
Concomitant Medications 
12.1 
Recommended Medications per Institutional Guidelines/Practices 
It is recommended that patients receive the following types of prophylactic therapies/regimens 
per institutional guidelines/practices:  
x Antibacterial: ciprofloxacin, levofloxacin, or an equivalent antibiotic. 
x Antifungal: fluconazole, voriconazole, or an equivalent antifungal. 
x Antiviral: acyclovir, valacyclovir, or an equivalent antiviral. 
12.2 
Allowed Medications/Therapies 
Refer to Section 8.2.1.1 for premedications to be administered with tagraxofusp. 
All patients may receive supportive care measures as clinically indicated, including prophylactic 
antibiotics, antihistamines, antiemetics, albumin, fluids (hydration), and supportive measures. 
Patients may receive growth factor support and/or blood product transfusions as per the 
discretion of their physician. 

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Albumin 25 g IV daily should be administered if serum albumin is < 3.0 g/dL during days when 
treatment is withheld or in the immediate post-treatment period. (Refer to Section 18.3 for 
albumin administration requirements in the setting of elements of CLS.)  
Corticosteroid therapy is permitted and is governed by parameters detailed in Section 12.3 
(Prohibited Medications/Therapies).  
Granulocyte-colony stimulating factor (G-CSF) is permitted only for the treatment of febrile 
neutropenia. Following a febrile neutropenic event, G-CSF prophylaxis may be considered if 
there is evidence of response and the Investigator determines that ongoing tagraxofusp treatment 
is associated with a potentially favorable risk-benefit profile (such a determination should be 
made in consultation with the Medical Monitor). 
12.3 
Prohibited Medications/Therapies 
Prior to discontinuation of tagraxofusp, patients may not receive the following anticancer/ 
antimyeloproliferative agents: JAKi (ruxolitinib, fedratinib, and others), interferon-Į, 
thalidomide, lenalidomide, cytotoxic chemotherapy agents (including 2-chlorodeoxyadenosine 
and other purine analogs), hypomethylating agents (5-aza, decitabine and others), tyrosine kinase 
inhibitors (including those which inhibit the BCR-ABL kinase such as imatinib), HU, and 
investigational anti-cancer agents. 
Patients may not receive additional disease-modifying or cytoreductive agents such as danazol or 
anagrelide. Patients may not receive erythroid- or platelet-stimulating growth factors.  
Hydroxyurea is prohibited during study participation except for cycle 1; Short-term treatment 
with HU beyond cycle 1 with approval of the Medical Monitor is permitted.  
Ongoing corticosteroid therapy at doses of > 20 mg/day prednisone (or equivalent) for > 7 days 
is not permitted; however transient increases in corticosteroid doses in the setting of infections or 
other “stress” settings are allowed.  
13 
Adverse Events and Safety Evaluation 
The AE reporting period for a patient treated in the study begins with provision of consent and is 
continuous through 30 days after the last tagraxofusp infusion. All AEs that occur in treated 
patients during the AE reporting period must be reported to the Sponsor or designee, whether or 
not the event is considered related to tagraxofusp. Any known untoward event that occurs 
beyond the AE reporting period (30 days after the last tagraxofusp infusion) that the Investigator 
assesses as related to tagraxofusp should also be reported as an AE. 
All patients should be monitored for at least 1 hour (or longer at the Investigator’s discretion) 
following the administration of each tagraxofusp infusion. The Investigator or designated 
medical staff responsible for study conduct and safety evaluations, should be available during the 
administration of tagraxofusp and follow-up to assess, treat, or report as necessary any AE or 
SAE that may occur. 

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13.1 
Definitions 
All observed or volunteered AEs regardless of suspected causal relationship to tagraxofusp will 
be reported as described below. 
13.1.1 
 Adverse Event (AE) 
An AE is any untoward medical occurrence in a study patient who is administered a medicinal 
product (drug or biologic); the event may or may not have a causal relationship with the 
medicinal product. Examples of AEs include, but are not limited to the following: 
x Clinically significant symptoms and signs including: 
- Worsening of signs and symptoms of the disease under study; disease progression 
without worsening of signs and symptoms as assessed by bone marrow aspiration or 
other methods should not be reported as AEs. 
- Signs and symptoms resulting from drug overdose, abuse, misuse, withdrawal, 
sensitivity, dependency, interaction, or toxicity. 
- All possibly related and unrelated illnesses, including the worsening of a preexisting 
illness. 
- Injury or accidents. Note that if a medical condition is known to have caused the 
injury or accident (hip fracture from a fall secondary to dizziness), the medical 
condition (dizziness) and the outcome of the accident (hip fracture from a fall) should 
be reported as 2 separate AEs. 
x Abnormalities in physiological testing or physical examination findings that require 
clinical intervention or further investigation (beyond ordering a repeat confirmatory test). 
x Laboratory abnormalities that meet any of the following (Note: merely repeating 
abnormal test, in the absence of any of the below conditions, does not constitute an AE. 
Any abnormal test result that is determined to be an error does not require reporting as an 
AE): 
- Test result that is associated with accompanying symptoms 
- Test result that requires additional diagnostic testing or medical/surgical intervention 
- Test result that leads to significant additional concomitant drug treatment or other 
therapy 
- Test result that is considered to be an AE by the Investigator or Sponsor 
Note that veno-occlusive disease occurring post-SCT and any changes in visual acuity and/or 
color vision will be followed as AEs of special interest. 

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13.1.2 
Serious Adverse Event (SAE) 
An AE that meets one or more of the following criteria/outcomes is classified as serious: 
x Results in death; 
x Is life-threatening (at immediate risk of death); 
x Requires admittance to the hospital or prolongation of existing hospitalization; 
x Results in persistent or significant disability/incapacity; 
x Results in congenital anomaly/birth disfigurements among the offspring of the patients;  
x Events with medical significance or needing medical intervention to prevent the 
occurrence of any of the above events. 
Medical judgment should be exercised in deciding whether expedited reporting is appropriate in 
other situations, such as important medical events that may not be immediately life-threatening 
or result in death or hospitalization, but may jeopardize the patient or may require intervention to 
prevent one of the other outcomes listed in the definition above. Serious also includes any other 
event that the Investigator or Sponsor judges to be serious, or which is defined as serious. 
AEs associated with in-patient hospitalization, or prolongation of an existing hospitalization, are 
considered serious. Any initial admission, even if the duration is less than 24 hours is considered 
serious. In addition, any transfer within the hospital to an acute/intensive care unit is considered 
serious. However, the following hospitalizations should not be considered serious: 
x Hospitalization or prolonged hospitalization in the absence of precipitating clinical AEs, 
as follows: 
- Admission for treatment of preexisting condition not associated with the development 
of a new AE or with a worsening of the preexisting condition 
- Administrative admission (e.g., for a yearly physical examination) 
- Protocol-specified admission during the study (e.g., admission for tagraxofusp 
treatment) 
- Preplanned treatments or surgical procedures 
- Admission exclusively for the administration of blood products 
Progress of the disease under study (including signs and symptoms of progression) should not be 
reported as an SAE unless the outcome is fatal during the study or within the safety reporting 
period. If the disease under study has a fatal outcome during the study or within the safety 
reporting period, then the event leading to death must be recorded as an AE and as an SAE of 
CTCAE Grade 5 intensity. Disease progression is NOT an SAE; however some sequelae of 
disease progression (i.e., pain, thrombocytopenia) may be reported as AEs or SAEs (generally 
not related to investigational therapy). 

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The onset date of an SAE is defined as the date on which the event initially met serious criteria 
(e.g., the date of admission to a hospital). The end date is the date on which the event no longer 
met serious criteria (e.g., the date the patient was discharged from a hospital). 
13.2 
Period of Observation 
Clinical signs and symptoms, and AEs (regardless of relationship to study drug) will be collected 
for treated patients continuously from provision of consent to 30 days following the last infusion 
of tagraxofusp. All SAEs and AEs judged to be related to study drug will be collected throughout 
the AE reporting period. 
Conditions that the patient experienced prior to the provision of consent should be recorded in 
the patient medical history section of the eCRF. All the AEs should be followed-up at the 
Investigator’s discretion until the symptoms dissipate or become stable even if AEs continue 
beyond the period of observation. AEs unresolved at the end of the observation period will be 
considered “ongoing” with an undetermined outcome; however, if after the period of observation 
completes but prior to the completion of the study, additional outcome information becomes 
available, it will be reported. The severity of the signs, symptoms, or AEs should be determined 
using the CTCAE, v4.03. A complete CTCAE list can be downloaded at 
http://evs.nci.nih.gov/ftp1/CTCAE/About.html. 
All clinically meaningful abnormal test results should be retested. Abnormal test results that are 
difficult to associate with the study drug should be followed until normalized or until the 
abnormity could be clearly attributed to another cause. Abnormal test results should not be 
reported as AEs unless they meet the criteria outlined in Section 13.1.1. 
13.3 
Pre-existing Conditions 
A pre-existing condition will not be reported as an AE unless the condition worsens by at least 
one CTCAE grade during the study. The pre-existing condition, however, must be recorded in 
the medical history eCRF as a pre-existing condition and all related concomitant medication 
administered for the condition recorded in the concomitant medication eCRF.  
13.4 
Pregnancy 
WOCBP and men with partners of childbearing potential must be using an adequate method of 
contraception to avoid pregnancy throughout the study and for up to 1 week after the study in 
such a manner that the risk of pregnancy is minimized. WOCBP include any female who has 
experienced menarche and who has not undergone successful surgical sterilization 
(hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or is not postmenopausal 
(defined as amenorrhea  12 consecutive months; or women on hormone replacement therapy 
with documented serum follicle-stimulating hormone level  35 mIU/mL). Even women who are 
using oral, implanted, or injectable contraceptive hormones or mechanical products, such as an 
intrauterine device or barrier methods (diaphragm, condoms, spermicides) to prevent pregnancy, 

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are practicing abstinence, or whose partner is sterile (e.g., vasectomy), should be considered to 
be of childbearing potential. 
WOCBP must have a negative serum or urine pregnancy test during screening within 1 week 
before the first study drug dose. If the pregnancy test is positive, the patient must not receive 
study therapy and must not be enrolled in the study. 
Sexually active WOCBP must use an effective method of birth control during the course of the 
study, in a manner such that the risk of failure is minimized. 
Prior to study enrollment, WOCBP must be advised of the importance of avoiding pregnancy 
during study participation and the potential risk factors for an unintentional pregnancy. This 
information will be included in the ICF that must be signed by the patient.  
In addition, all WOCBP or fertile men with partners of childbearing potential should be 
instructed to contact the Investigator immediately if they suspect they or their partner might be 
pregnant (e.g., missed or late menstrual period) at any time during study participation. 
If following initiation of study drug, it is subsequently discovered that a patient is pregnant or 
may have been pregnant at the time of exposure to study therapy, including during at least 1 
week after product administration, study therapy will be permanently discontinued in an 
appropriate manner. Exceptions to discontinuation may be considered for life-threatening 
conditions only after consultation with the Sponsor and Medical Monitor or as otherwise 
specified in this protocol. The Investigator must immediately notify the Sponsor and Medical 
Monitor of this event. 
Protocol-required procedures for study discontinuation and follow-up must be performed on the 
patient unless contraindicated by pregnancy (e.g., x-ray studies). Other appropriate pregnancy 
follow-up procedures should be considered if indicated. In addition, the Investigator must report 
to the Sponsor follow-up information regarding the course of the pregnancy of the 
patient/patient’s partner, including perinatal and neonatal outcome. Infants should be followed 
for a minimum of 8 weeks. 
13.5 
Documentation and Reporting of Adverse Events by Investigator 
The Investigator is to report all directly observed AEs and AEs spontaneously reported by the 
patient using concise medical terminology. In addition, each patient will be questioned about 
AEs at each clinic visit following initiation of treatment. The question asked will be “Since your 
last clinic visit have you had any health problems?” or a similar question to assess health status. 
The AE reporting period for this study begins after provision of written informed consent and 
ends 30 days after the last tagraxofusp infusion. All AEs are to be reported on the AE eCRFs.  
All AEs that occur in study patients during the AE reporting period must be reported to the 
Sponsor, whether or not the event is considered study drug-related. In addition, any untoward 

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event that occurs beyond the AE reporting period that the Investigator assesses as related to the 
investigational product should also be reported as an AE. 
Each AE is to be classified by the Investigator as serious or non-serious. This classification of 
the gravity of the event determines the reporting procedures to be followed. If a SAE occurs, 
reporting will follow local and international regulations, as appropriate. 
For any event that meets one of the SAE criteria, the Investigator must notify the Safety Contact 
within 24 hours of the knowledge of the occurrence. To report the SAE, complete the SAE form 
and email to the Safety Contact (email address listed below) within 24 hours of awareness. 
Safety Contact Information: 
E-mail: 
  
Each SAE should be followed until resolution, or until such time as the Investigator determines 
its cause or determines that, it has become stable.  
Within 24 hours of receipt of follow-up information, the Investigator must update the SAE form 
and submit any supporting documentation (e.g., patient discharge summary or autopsy reports) to 
the Safety Contact via e-mail. All SAEs are also to be recorded in the eCRF.  
The Sponsor will report AEs, which are unexpected and reported as serious and associated with 
use of the study drug, to the applicable regulatory authorities and all participating sites. For 
events that are fatal or life-threatening, unexpected, and associated with use of the investigational 
product, a 7-Day Alert Report will be submitted to the applicable regulatory authorities within 
7 calendar days of receipt of the SAE information. For all other events that are serious, 
unexpected, and associated with the use of the investigational medicinal product, a written report 
will be made no more than 15 calendar days from the date the Sponsor learns of the event.  
13.6 
Assessment of Causal Relationship to Tagraxofusp 
In this study, the investigational medicinal product is tagraxofusp. The relationship of an AE to 
the investigational product should be classified using the following guidelines: 
x Related: A temporal relationship exists between the event onset and administration of 
tagraxofusp. It cannot be readily explained by the patient’s clinical state, intercurrent 
illness, or concomitant therapies. In case of cessation of the dose, the event abates or 
resolves and reappears upon re-challenge.  
x Not Related: Evidence exists that the AE has an etiology other than the study drug 
(e.g., pre-existing condition, underlying disease, intercurrent illness, or concomitant 
medication). This includes events that are considered probably not or not related to 
tagraxofusp. It should be emphasized that ineffective study drug treatment should not be 
considered as causally related in the context of AE reporting (in other words, disease 
progression is not considered an AE; however some sequelae of disease progression may 
be reported as AEs and should generally be reported as AEs not related to investigational 
therapy). 

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An Investigator who is qualified in medicine and has an active license to practice in the 
geographic location where the patient is being treated must make the determination of 
relationship to the investigational product for each AE. The Investigator should decide whether, 
in his or her medical judgment, there is a reasonable possibility that the event may have been 
caused by the investigational product. The following factors for study drug relationship should 
be referenced when making a determination of “related” or “not related.” 
x The temporal sequence from study drug administration: The event should occur after the 
study drug is given. The length of time from study drug exposure to event should be 
evaluated in the clinical context of the event. 
x Underlying, concomitant, intercurrent diseases: Each report should be evaluated in the 
context of the natural history and course of the disease being treated and any other 
disease the patient may have. 
x Concomitant medication/therapy: The other medications the patient is taking or the 
treatment the patient receives should be examined to determine whether any of them 
might be recognized to cause the event in question. Transfusions of pRBCs or platelets 
after enrollment (first dose) will be captured as concomitant medication/therapy. 
x Known response pattern for this class of study drug: Clinical and/or preclinical data may 
indicate whether a particular response is likely to be a class effect. 
x Exposure to physical and/or mental stresses: The exposure to stress might induce adverse 
changes in the recipient and provide a logical and better explanation for the event. 
x The pharmacology and pharmacokinetics of the study drug: The known pharmacologic 
properties (absorption, distribution, metabolism, and excretion) of the study drug should 
be considered. 
13.7 
Grading of Adverse Event Severity 
To report AEs on the eCRFs, the Investigator will use the severity grading as described in NCI 
CTCAE, v4.03.  
Every effort should be made by the Investigator to assess the AE according to CTCAE criteria. If 
the Investigator is unable to assess severity because the term is not described in NCI CTCAE, 
Version 4.03, severity of MILD, MODERATE, SEVERE, LIFE-THREATENING, or DEATH 
may be used to describe the maximum intensity of the AE. For purposes of consistency, these 
intensity grades are defined as follows: 
x Mild (Grade 1): does not interfere with patient’s usual function 
x Moderate (Grade 2): interferes to some extent with patient’s usual function 
x Severe (Grade 3): interferes significantly with patient’s usual function 
x Life-threatening (Grade 4): results in immediate risk of patient’s death 

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x Death (Grade 5): results in patient’s death 
Note the distinction between the severity and the seriousness of an AE. A severe event is not 
necessarily a serious event. For example, a headache may be severe (interferes significantly with 
patient’s usual function) but would not be classified as serious unless it met one of the criteria for 
serious events. 
It is requested that when reporting AEs for which potentially redundant CTCAE terms exist, 
investigators utilize the more clinically-oriented terminology (for example, “anemia” is 
preferable to “hemoglobin decreased”).  
It is also requested that in the setting of a hypersensitivity reaction or suspected hypersensitivity 
reaction considered by the Investigator to be related to investigational therapy, that investigators 
report both the specific symptoms associated with the reaction (i.e., “urticaria,” ”chills,” 
“dyspnea”) and also report the appropriate term indicating the hypersensitivity reaction (“allergic 
reaction,” or “infusion-related reaction” or “anaphylaxis” if appropriate [General Disorders and 
Immune System Disorders; CTCAE v4.03]). 
14 
Statistical Analysis 
14.1 
General Considerations 
Analyses will be performed on all patients that received any quantity of tagraxofusp (i.e., all 
treated patients). The baseline value for a given variable is defined as the last measurement for 
the variable prior to the first infusion of tagraxofusp. Cycle 1 Day 1 for each individual patient is 
defined as the date the patient receives their first infusion of tagraxofusp. 
14.2 
Determination of Sample Size 
14.2.1 
Stage 2 (Patients with CMML Previously Enrolled and Patients with MF) 
An objective of Stage 2 is a preliminary assessment of response rates associated with tagraxofusp 
in CMML and MF. Because available anti-cancer agents are associated with very limited 
responses in the MPNs evaluated in this study, it is anticipated that an agent that confers a 
response rate  10% may be considered active and worthy of additional investigation.  
Initially, a sample size of 18 patients with a particular MPN was planned for enrollment in 
Stage 2. Furthermore, it was planned that in settings where there is evidence that a sufficient 
proportion of patients have experienced improvement in components of the response criteria, that 
additional investigation of tagraxofusp in a given MPN may have been considered appropriate 
based on preliminary data. 
Preliminary evidence of activity has been observed in patients with relapsed and/or refractory 
CMML and MF.  
As of July 2021, 36 patients have been enrolled, comprising 20 patients with CMML-1 and 
16 with CMML-2; median age was 69 years (range 42–81), and 75% of patients were male. 
Twenty-three patients (64%) had either high- or intermediate-risk genetics based on CPSS, 

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GFM, MMM, or ELN risk stratification systems.  Prior therapies included HMA in 16  patients 
(43%), allogeneic stem cell transplantation (allo-SCT) in 3 (8%), and other in 12 (32%); 
7 patients (19%)  were high-risk and treatment naive. Overall, 16 patients (44%) had baseline 
palpable splenomegaly; in 12 of these patients, VSOHHQVL]HZDVFPEHORZOHIWFRVWDOPDUJLQ
Overall, 4 of 36 (11%) patients achieved bone marrow morphological complete responses 
(BMCRs), 1 of whom was bridged to allo-SCT; all 4 patients had splenomegaly at baseline. It is 
noteworthy that 2 of the 4 BMCRs, were observed in patients with high-risk genetic features. 
Fifteen patients (42%) with baseline splenomegaly had spleen responses; 9 patients (60%) had a 
UHGXFWLRQLQVSOHHQVL]HLQFOXGLQJZLWKVSOHQRPHJDO\RIFPDWEDVHOLQH 
14.2.2 
Stage 3A in Patients with CMML 
The purpose of Stage 3A is to evaluate the clinical benefit derived from individual components, 
or variations thereof, of the MDS/MPN 2015 criteria that may allow for a prospective definition 
of a primary efficacy endpoint, that will provide the primary evidence of efficacy for regulatory 
decision-making in the planned confirmatory cohort (Stage 3B; to be added under the auspices of 
separate amendment). Individual evaluations will be performed for each of the two CMML 
cohorts in Stage 3A. 
Approximately 20 patients with CMML may be enrolled in each of the two cohorts in Stage 3A 
to ensure a sufficient number of patients with specific baseline disease characteristics are 
enrolled to reject a meaningless rate of clinical activity in subsets of interest. (For our purposes, a 
meaningless rate will be taken to mean that there are no responders, using the definitions below, 
in the sample for each of the following subsets.) No formal stratification will be performed; 
however approximately 8-10 patients with baseline splenomegaly (defined as  5 cm below the 
left costal margin) and approximately 8-10 patients who are transfusion-dependent at baseline 
(receipt of at least 4 transfusions within 8 weeks before the first tagraxofusp dose) will be 
included in each 20-patient cohort. This intended enrollment distribution may be adjusted, 
depending on the actual prevalence of splenomegaly and transfusion-dependence seen in the 
general patient population as the study continues to enroll. 
In this exploratory stage, the primary evidence of activity in each subset would be (1) a reduction 
in spleen volume that correlates with an improvement in symptom score or (2) conversion from 
transfusion-dependent to transfusion-independent. These occurrences on a per-patient basis 
would be considered responses within each subgroup. Clinical activity would have been 
demonstrated if at least 1 patient achieves either of these clinically important outcome responses. 
Up to 5 additional patients with either of these specific baseline characteristics may be enrolled 
in Stage 3A, to increase the confidence in the observed results, if necessary. It can be seen in the 
graph below that for any true rate of response that is  0.15, this approach would have at least 
80% power to detect at least one responder. Given at least a single responder, additional methods 
such as confidence interval estimation or formal power calculations, may be used to determine 
whether to move ahead with a confirmatory Stage 3B.  

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The operating characteristics of this approach to sample size estimation in Stage 3A may be seen 
in the following graph. This graph presents the sample size required to have either an 80%, 90%,
or 95% probability of at least 1 responder when the sample size is N, and the true probability of 
response is P.
As an example, if the true response probability were 0.15, 10 patients evaluated for a given 
response type would result in at least one response with 80% probability.
Other subsets of patients may be retrospectively identified in which treatment with tagraxofusp 
may result in clinically important outcomes, and enrichment strategies within the framework of 
this sample size may be applied, with the same objective of rejecting a meaningless rate of 
clinical activity.
14.3
Demographics and Baseline Characteristics
Demographic (e.g., gender, age, and race) and baseline characteristics (e.g., ECOG PS, height, 
weight, and prior therapy) will be summarized with descriptive statistics.
14.4
Analyses of Safety Data
Safety assessments include DLTs, AEs, SAEs, physical examinations, vital sign measurements, 
ECGs, clinical laboratory evaluations, and reasons for treatment discontinuation due to toxicity.
Treatment-emergent AEs through 30 days after the last tagraxofusp infusion will be summarized 
by Medical Dictionary for Regulatory Activities (MedDRA™) Version 13.1 (or higher) System 
Organ Class and preferred term. The incidences and percentages of patients experiencing each 
AE preferred term will be summarized with descriptive statistics. AEs will also be summarized 
by NCI CTCAE, Version 4.03 (or higher), grade and by causality (relationship to study drug). 
DLTs, Grade 3-4 AEs, SAEs, and AEs resulting in dose modification or treatment 
discontinuation will also be summarized by preferred term. 

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Laboratory results will be classified according to NCI CTCAE, Version 4.03. Laboratory results 
not corresponding to an NCI CTCAE term will not be graded. Incidences of laboratory 
abnormalities will be summarized with descriptive statistics. 
Vital signs, physical examination results, and ECGs will be summarized with descriptive 
statistics. 
14.5 
Analyses of Efficacy Data 
Efficacy assessments include ORR, CR rate, specific components of the response criteria for 
each indication, duration of response (DOR), progression-free survival (PFS), and OS. Refer to 
Appendix 18.1 for detailed response criteria established for CMML and MF. All efficacy 
outcomes will be presented by subgroups defined by disease. 
Data from Stage 2 will be analyzed with descriptive statistical methods to provide estimates of 
rates of response. Stage 3A data will be analyzed with descriptive and correlation methods, with 
results intended to assist in the design of the confirmatory Stage 3B. Bayesian methods may also 
be used to determine likely values of response parameters, with Stage 2 results providing prior 
information for calculation of credible intervals based on Stage 3A data. Complete details of 
efficacy analyses will be provided in the Statistical Analysis Plan (SAP). 
14.6 
Pharmacokinetic and Immunogenicity Analyses 
Planned PK and immunogenicity analyses will be described in separate SAPs. 
14.7 
Blinding 
This is an open-label study. 
15 
Emergency Procedures 
15.1 
Emergency Contact 
In emergencies, the Investigator should contact the Medical Monitor by telephone at the number 
listed on the title page of the protocol. 
15.2 
Emergency Identification of Investigational Products 
Since this is an open-label study, the investigational treatment will be identified on the package 
labeling. 
15.3 
Emergency Treatment 
During a patient’s participation in the study, the Investigator and/or institution should ensure that 
adequate medical care is provided to a patient for any AEs, including clinically significant 
laboratory values, related to the study. 

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16 
Ethical and Regulatory Considerations 
16.1 
Good Clinical Practice 
As the Sponsor of this clinical study, Stemline has the overall responsibility for the conduct of 
the study, including assurance that the study meets the requirements of applicable regulatory 
authorities. Stemline will maintain compliance with the FDA Code of Federal Regulations 
(CFR), ICH Guideline E6, Declaration of Helsinki, and Good Clinical Practice (GCP) guidelines. 
The study must receive approval from an Institutional Review Board (IRB)/Ethics Committee 
(EC) prior to commencement. The Investigator will conduct all aspects of this study in 
accordance with applicable national, state, and local laws of the pertinent regulatory authorities. 
The Sponsor is responsible for obtaining IRB/EC approvals, providing Investigators with 
information required to conduct the study, ensuring proper investigative site monitoring, 
verifying that appropriate patient informed consent is obtained, and ensuring that the IRB/EC 
and regulatory agencies are promptly informed of significant new information regarding the 
study. 
16.2 
Delegation of Investigator Responsibilities 
The Investigator must ensure that all persons assisting with the study are adequately informed 
about the protocol, any amendments to the protocol, the study drugs, and their study-related 
duties and functions. The Investigator should maintain a list of sub-investigators and other 
appropriately qualified persons to whom he or she has delegated significant study-related duties. 
16.3 
Patient Information and Informed Consent 
Before being admitted to the clinical study, the patient must consent to participate after the 
nature, scope, and possible consequences of the clinical study have been explained in a language 
understandable to him or her. An ICF that includes both information about the study and the 
consent form will be prepared and given to the patient. This document will contain all ICH, 
GCP, and locally required regulatory elements. The ICF must specify who informed the patient 
and be approved by the Institution’s IRB/EC. Copies of the ICF used in the study must contain 
the IRB/EC-approval stamp (if applicable) and version date. The Investigator must keep the 
original executed ICF including the patients’ signatures and the signing dates properly stored in a 
secured location at the study site with an additional copy of the ICF included with the patients’ 
medical chart and therapy records. 
After reading the informed consent document, the patient must give consent in writing. The 
written informed consent will be obtained prior to conducting any study-related procedures or 
tests. The patient’s consent must be confirmed at the time of consent by the dated signature of 
the person conducting the informed consent discussions. If the patient agrees to participate in the 
study, the patient and the Investigator must sign both copies of the ICF. A copy of the signed ICF 
must be given to the patient or the patient’s legally authorized representative. The signed ICF 

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must be available for verification by the Sponsor’s designated monitors or Regulatory Authority 
inspectors. 
The date of the signed ICF will also be noted in the patient’s medical chart. Patients should be 
informed of new information learned during the study, which may affect their decision to 
continue participation in the study. The Investigator should inform the patient’s primary 
physician about the patient’s participation in the study if the patient has a primary physician and 
if the patient agrees to the primary physician being informed. 
16.4 
Confidentiality 
The Investigator(s) and the Sponsor or its authorized representative will preserve the 
confidentiality of all patients and donors participating in the study, in accordance with GCP, 
ICH, local regulations and to the extent applicable the Health Insurance Portability and 
Accountability Act of 1996 (“HIPAA”). 
Patient names will not be supplied to the Sponsor or its authorized representative. Only the 
patient study numbers and date of birth will be recorded in the eCRF, and if the patient name 
appears on any other document (e.g., pathologist report), it must be obliterated before a copy of 
the document is supplied to the Sponsor or its authorized representative. Study findings stored on 
a computer will be stored in accordance with local data protection laws. Patients will be told that 
representatives of the Sponsor, its authorized representative, IRB/EC, 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 law. The Investigator will maintain a personal patient 
identification list (patient numbers with the corresponding patient names) to enable records to be 
identified. 
16.5 
Protocol Amendments 
Any changes that affect patient safety or welfare will be submitted to the IRB/EC and Regulatory 
Authority (where applicable) for approval prior to implementation. The Investigator and the 
Sponsor must approve all amendments. No amendment will be implemented until approved and 
signed by all parties. Exceptions to this are when the Investigator considers that the patient’s 
safety is compromised. 
16.6 
IRB/EC Approval and Reporting 
The Investigator must obtain appropriate IRB/EC approval prior to study initiation. A copy of 
the written approval from the IRB/EC and a copy of the approved ICF should be sent to the 
Sponsor or its delegate. It is also necessary to submit a list of the IRB/EC members (including 
their Institution affiliations, gender makeup, and occupations) or supply a statement from the 
IRB/EC specifying that the membership complies with applicable regulations. 
The study protocol, patient information and consent form, the Investigator’s Brochure, available 
safety information, patient recruitment materials (e.g., advertisements), information about 

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payments and compensation available to the patients and documentation evidencing the 
Investigator’s qualifications should be submitted to the IRB/EC for ethical review and approval 
according to local regulations, prior to the study start. The written approval should identify all 
documents reviewed by name and version. 
Any changes to the protocol must be approved by the Sponsor in writing unless the change is 
proposed to assure safety of the patient. In the non-emergent setting, following agreement on the 
proposed changes, an amendment to the protocol will be submitted to the IRB/EC for approval 
prior to implementation of the change. Any change made emergently must be documented in the 
patient's medical record. 
If required by legislation or the IRB/EC, the Investigator must submit to the IRB/EC: 
x Information on serious or unexpected AEs as soon as possible; 
x Periodic reports on the progress of the study. 
16.7 
Closure of the Study 
The Sponsor or its authorized representative has the right to close this study and the Investigator 
has the right to close the study at his/her site at any time. The IRB/EC must be informed, if 
required by legislation. Should the study be closed prematurely, all unused tagraxofusp will be 
reconciled with dispensing records, documented, and, if directed by the Sponsor, destroyed at the 
study site or returned for destruction after completion of accountability by the site monitor. 
16.8 
Record Retention 
The Sponsor will maintain copies of correspondences, records of shipment and disposition of 
study drug, AEs, and other records related to the clinical study and the signed Investigator 
agreements. Retained records will enable the tracing of patients who have participated in the 
study. Notes of patients who have enrolled in the study must be retained if the patient has died. 
Study documents must be retained by the Investigator for a minimum of 2 years after the last 
approval of a marketing application in an ICH region and until there are no pending or 
contemplated marketing applications in an ICH region or at least 2 years have elapsed since the 
formal discontinuation of clinical development of the investigational product. These documents 
should be retained for a longer period, however, if required by the applicable regulatory 
requirements or by an agreement with the Sponsor. It is the responsibility of the Sponsor to 
inform the Investigator when storage of these documents is no longer required. The Investigator 
should contact the Sponsor if the site’s archiving arrangements change at any time. 
16.9 
Liability and Insurance 
Liability and insurance provisions for this study are provided in the clinical trial agreement. 

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16.10 Financial Disclosure 
Prior to study initiation the Investigator will be asked to sign a clinical trial agreement. All 
Investigators also will be required to sign a Financial Disclosure Form in accordance with 21 
CFR Part 54; Financial Disclosure by Clinical Investigators prior to study initiation and at any 
time financial interest changes. 
16.11 Study Monitoring and Auditing 
All aspects of the study will be carefully monitored by the Sponsor or its designee for 
compliance to applicable government regulations with respect to current GCP and current 
standard operating procedures. Monitoring functions will be performed in compliance with 
21CFR§812.43(d) and 21CFR§812.46. Direct access to the on-site study documentation and 
medical records must be ensured. 
16.12 Study Monitoring and Source Data Verification 
The Investigator is responsible for the validity of all data collected at the site and must accept the 
various monitoring procedures employed by the Sponsor. The purpose of monitoring is to verify 
the rights and well-being of human patients are protected; that study data are accurate, complete, 
and verifiable with source data; that the study is conducted in compliance with the protocol, GCP 
and the applicable regulatory requirements. 
Sites will be monitored to identify and reconcile any differences between the completed eCRFs 
and medical records, and review Source documents for accuracy, completeness, and legibility. 
The monitor will review completed data forms and study documentation for accuracy, 
completeness, and protocol compliance. In addition, the Sponsor will evaluate any protocol 
deviations and take corrective action as necessary. 
The Sponsor will review significant new information, including unanticipated AEs and ensure 
that such information is provided to all reviewing IRBs/ECs. This information will also be 
provided to the FDA, other regulatory authorities, and Investigators worldwide in accordance 
with local regulations. The monitor’s responsibilities include site visits, participation in initial 
study sessions, review of eCRFs, source documents and results, and ensuring clear 
communication between the Investigator and the Sponsor. 
The monitor and data manager will query any missing or spurious data with the Investigator, 
which should be resolved in a timely manner. A monitoring log will be maintained recording 
each visit, the reason for the visit, the monitor’s signature, and Investigator’s or designee’s 
confirmation signature. 

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16.12.1 Study Documentation 
The Investigator must provide the Sponsor with the following documents prior to enrollment and 
maintain the currency of these documents throughout the course of the study. 
x Completed and signed Form FDA 1572 or equivalent. 
x All applicable country-specific regulatory forms. 
x Current signed and dated curricula vitae for the Investigator, sub-investigators, and other 
individuals having significant investigator responsibility who are listed on Form FDA 
1572 or equivalent, or the clinical study information form. 
x Copy of the current medical license of the principal Investigator, any sub-investigators 
and any other individuals having significant responsibility as listed in the 1572. 
x A financial disclosure form for the Principal Investigator and any other persons listed in 
the 1572. 
x Copy of the IRB/EC approval letter for the protocol and informed consent. All 
advertising, recruitment, and other written information provided to the patient must be 
approved by the IRB/EC. Written assurance of continuing approval (at least annually) as 
well as a copy of the annual progress report submitted to the IRB/EC must also be 
provided to the Sponsor. 
x Copy of the IRB/EC-approved informed consent document. 
x A list of the IRB/EC members or a Federalwide Assurance number. 
x Copy of the protocol signature page signed by the Investigator. 
x Fully executed clinical trial agreement, including budget. 
x A written document containing the name, location, certification number, and date of 
certification of each laboratory to be used for laboratory assays and those of other 
facilities conducting tests. This document should be returned along with the laboratory 
director’s curricula vitae and active medical license. List of normal laboratory values and 
units of measure for all laboratory tests required by the protocol. 
The sites will also be asked to maintain a Delegation of Authority Log, pharmacy logs, 
temperature logs, personal patient identification log and monitoring visit logs during this study. 
16.12.2 Site Audits 
For the purpose of compliance with GCP and regulatory agency guidelines, it may be necessary 
for Sponsor authorized Quality Assurance personnel and/or authorized personnel from an 
external regulatory agency to conduct an audit/inspection of an investigational site. These site 
reviews may be planned or spontaneous and occur at any stage during the study. The purpose of 
an audit is to assess the quality of data with regard to accuracy, adequacy, and consistency, and 

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to assure that studies are conducted in accordance with GCP, the protocol, and Regulatory 
Agency guidelines. 
The Investigator should promptly notify the Sponsor or its authorized representative of any 
audits by any regulatory authorities and promptly forward copies of any audit reports received to 
the Sponsor or its authorized representative. 
Electronic data systems will be in accordance with applicable aspects of 21 CFR Part 11, ICH 
Guidelines, GCP, and HIPAA. 
16.13  Documentation and Use of Study Findings 
16.13.1  Documentation of Study Findings 
Source documentation will be maintained to document the treatment and study course of a 
patient and to substantiate the integrity of the study data submitted for review to regulatory 
agencies. Source documentation for Stemline studies will include, but not be limited to, 
worksheets, hospital and/or clinic or office records documenting patient visits including study 
and other treatments or procedures, medical history and physical examination information, 
laboratory and special assessments results, drug accountability records, and medical 
consultations (as applicable). 
Laboratory and diagnostic reports including but not limited to: local laboratory hematology and 
chemistry results, bone marrow biopsy reports, bone marrow aspirate reports, ECHO readings, 
and MUGA readings may be collected by the study monitor during the course of the study. 
Every effort should be made by the site to de-identify personal patient information from these 
reports and replace it with the patient study identification number. 
16.13.2 Use of Study Findings 
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 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. The Sponsor has full ownership of the 
eCRFs completed as part of the study. 
All publications and presentations of the results of the Study are governed by the applicable 
provisions of the clinical trial agreement between the Sponsor and the institution. By signing the 
study protocol, the Investigator agrees that the results of the study may be used for the purposes 
of national and international registration, publication, and information for medical and 
pharmaceutical professionals by the Sponsor. If necessary, the authorities will be notified of the 
Investigator’s name, address, qualifications, and extent of involvement. The Investigator may not 
publish or present any information on this study without the express written approval of the 
Sponsor. Additionally, the Sponsor may, for any reason, withhold approval for publication or 

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presentation. If the Investigator is to be an author of a publication manuscript prepared by the 
Sponsor, the Sponsor will allow the Investigator 30 days for full review of the manuscript before 
publication. Such manuscript or materials should be provided for Sponsor review in accordance 
with the specifications in the clinical trial agreement. 

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17 
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18 
Appendices 
18.1 
Disease-specific Response Criteria 
Table 6: 
Stage 2: Revised IWG-MRT and ELN Response Criteria for MF 
Response categories 
Required criteria  
(for all response categories, benefit must last for t12 weeks to qualify as a response) 
CR 
Bone marrow 1: 
Age-adjusted normocellularity; < 5% blasts;  Grade 1 MF 2 and 
Peripheral blood:  Hemoglobin t 100 g/L and < ULN; neutrophil count t 1x109/L and < ULN; 
Platelet count t 100x109/L and < ULN; < 2% immature myeloid cells3 and 
Clinical: 
Resolution of disease symptoms; spleen and liver not palpable; no evidence 
of EMH 
PR 
Peripheral blood: Hemoglobin t100 g/L and < ULN; neutrophil count t1x109/L and < ULN;  
Platelet count t100x109/L and < ULN; < 2% immature myeloid cells3 and 
Clinical:  
Resolution of disease symptoms; spleen and liver not palpable; no evidence 
of EMH  
or 
Bone marrow1: 
Age-adjusted normocellularity; < 5% blasts;  Grade 1 MF2 and  
Peripheral blood: Hemoglobin t85g/L but < 100g/L and < ULN; neutrophil count t1×109/L 
and < ULN; platelet count t50×109/L but < 100×109/L and < ULN; < 2% 
immature myeloid cells3 and  
Clinical: 
Resolution of disease symptoms; spleen and liver not palpable; no evidence 
of EMH 
Clinical improvement (CI) 
The achievement of anemia, spleen or symptom response without progressive disease or 
increase in severity of anemia, thrombocytopenia or neutropenia4 
Anemia response 
Transfusion independent patients: a t 20g/L increase in hemoglobin level5 
Transfusion dependent patients: becoming transfusion independent6 
Spleen response7 
A baseline splenomegaly that is palpable 5-10cm below the LCM, becomes not palpable8 
or 
A baseline splenomegaly that is palpable > 10cm below the LCM, decreases by t 50%8 
A baseline splenomegaly that is palpable < 5cm below the LCM is not eligible for spleen 
response 
A spleen response requires confirmation by MRI or CT showing t 35% spleen volume 
reduction 
Symptom response 
A t 50% reduction in the MPN-SAF TSS9 
Progressive disease10 
Appearance of new splenomegaly that is palpable at least 5cm below the LCM  
or 
A t 100% increase in palpable distance, below LCM, for baseline splenomegaly of 5-10 cm  
or 
A 50% increase in palpable distance, below LCM, for baseline splenomegaly of > 10 cm 
or 
Leukemic transformation confirmed by a bone marrow blast count of t 20%  
or 
A peripheral blast content of t20% associated with an absolute blast count of t1x109/L that 
lasts for at least 2 weeks 
Stable disease 
Belonging to none of the above listed response categories 
Relapse 
No longer meeting criteria for at least CI after achieving CR, PR or CI,  
or 
Loss of anemia response persisting for at least 1 month  
or 

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Response categories 
Required criteria  
(for all response categories, benefit must last for t12 weeks to qualify as a response) 
Loss of spleen response persisting for at least 1 month 
Cytogenetic remission 
At least 10 metaphases must be analyzed for cytogenetic response evaluation and requires 
confirmation by repeat testing within a 6-month window 
CR: eradication of a preexisting abnormality 
PR: t 50% reduction in abnormal metaphases (partial response applies only to patients with at 
least 10 abnormal metaphases at baseline) 
Molecular remission 
Molecular response evaluation must be analyzed in peripheral blood granulocytes and requires 
confirmation by repeat testing within a 6-month window 
CR: eradication of a preexisting abnormality 
PR: t50% decrease in allele burden (partial response applies only to patients with at least 
20% mutant allele burden at baseline) 
Cytogenetic/molecular 
relapse 
Re-emergence of a pre-existing cytogenetic or molecular abnormality that is confirmed by 
repeat testing 
Adapted from Tefferi, et al. Blood 2013; 122(8):1395-98. 
EMH: extramedullary hematopoiesis (no evidence of EMH implies the absence of pathology- or imaging study-proven 
nonhematosplenic EMH). LCH: left costal margin. ULN: upper limit of normal. 
1 
Baseline and posttreatment bone marrow slides are to be interpreted at one sitting by a central review process. Cytogenetic 
and molecular responses are not required for CR assignment. 
2 
Grading of MF is according to the European classification. Thiele et al. European consensus on grading bone marrow 
fibrosis and assessment of cellularity. Haematologica 2005; 90: 1128. 
It is underscored that the consensus definition of a CR bone marrow is to be used only in those patients in which all other 
criteria are met, including resolution of leukoerythroblastosis. It should also be noted that it was a particularly difficult task 
for the working group to reach a consensus regarding what represents a complete histologic remission. 
3 
Immature myeloid cells constitute blasts + promyelocytes + myelocytes + metamyelocytes + nucleated red blood cells. In 
splenectomized patients, < 5% immature myeloid cells is allowed. 
4 
See above for definitions of anemia response, spleen response, and progressive disease. Increase in the severity of anemia 
constitutes the occurrence of new transfusion dependency or a t 20 g/L decrease in hemoglobin level from pretreatment 
baseline that lasts for at least 12 weeks. Increase in severity of thrombocytopenia or neutropenia is defined as a 2-grade 
decline, from pretreatment baseline, in platelet count or absolute neutrophil count, according to the CTCAE version 4.03. In 
addition, assignment to CI requires a minimum platelet count of t 25×109/L and absolute neutrophil count of t0.5x109/L. 
5 
Applicable only to patients with baseline hemoglobin of < 100g/L. In patients not meeting the strict criteria for transfusion 
dependency at the time of study enrollment (see as follows), but have received transfusions within the previous month, the 
pretransfusion hemoglobin level should be used as the baseline. 
6 
Transfusion dependency before study enrollment is defined as transfusions of at least 6 units of pRBCs in the 12 weeks prior 
to study enrollment, for a hemoglobin level of < 85 g/L, in the absence of bleeding or treatment-induced anemia. In addition, 
the most recent transfusion episode must have occurred in the 28 days prior to study enrollment. Response in transfusion-
dependent patients requires absence of any pRBC transfusions during any consecutive “rolling” 12-week interval during the 
treatment phase, capped by a hemoglobin level of t85g/L. 
7 
In splenectomized patients, palpable hepatomegaly is substituted with the same measurement strategy. 
8 
Spleen or liver responses must be confirmed by imaging studies where a t35% reduction in spleen volume, as assessed by 
MRI or CT, is required. Furthermore, a t35% volume reduction in the spleen or liver, by MRI or CT, constitutes a response 
regardless of what is reported with physical examination. 
9 
Symptoms are evaluated by the MPN-SAF TSS. The MPN-SAF TSS is assessed by the patients themselves and this 
includes fatigue, concentration, early satiety, inactivity, night sweats, itching, bone pain, abdominal discomfort, weight loss 
and fevers. Scoring is from 0 (absent/as good as it can be) to 10 (worst imaginable/bad as it can be) for each item. The 
MPN-SAF TSS is the summation of the individual scores (0-100 scale). Symptom response requires t50% reduction in the 
MPN-SAF TSS. 
10 Progressive disease assignment for splenomegaly requires confirmation by MRI or CT showing a t25% increase in spleen 
volume from baseline. Baseline values for both physical examination and imaging studies refer to pretreatment baseline and 
not to posttreatment measurements. 
Grading of Myelofibrosis 

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MF-0 
Scattered linear reticulin with no intersections (crossovers) corresponding to normal BM. 
MF-1 
Loose network of reticulin with many intersections, especially in perivascular areas. 
MF-2 
Diffuse and dense increase in reticulin with extensive intersections, occasionally with focal 
bundles of thick fibers mostly consistent with collagen, and/or focal osteosclerosis.1 
MF-3 
Diffuse and dense increase in reticulin with extensive intersections and coarse bundles of thick 
fibers consistent with collagen, usually associated with osteosclerosis.1 
Adapted from Arber et al, Blood 2016; 127(20): 2391-2405 
Semiquantitative grading of BM fibrosis (MF) with minor modifications concerning collagen and osteosclerosis. Fiber density 
should be assessed only in hematopoietic areas.  
1. In grades MF-2 or MF-3 an additional trichrome stain is recommended.  

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Table 7: 
Stage 2: Modified IWG Response Criteria for Altering Natural History of MDS 
(Including CMML) 
Category 
Response criteria (response must last at least 4 weeks) 
Complete remission 
Bone marrow: d5% myeloblasts with normal maturation of all cell lines(1) 
Persistent dysplasia will be noted1,2 
Peripheral blood3: Hemoglobin t11g/dL 
Platelets t100×109/L 
Neutrophils t1.0×109/L2 
Blasts 0% 
Partial remission 
All CR criteria if abnormal before treatment except: 
Bone marrow blasts decreased by t50% but still > 5% 
Cellularity and morphology not relevant 
Bone Marrow CR(2) 
Bone marrow d5% myeloblasts and decrease by t50% over pretreatment2 
Peripheral blood:  If hematologic improvement responses, they will be noted in addition to 
marrow CR2 
Stable disease 
Failure to achieve at least PR, but no evidence of progression for > 8 weeks 
Failure 
Death during treatment or disease progression characterized by worsening of cytopenias, 
increase in percentage of bone marrow blasts or progression to a more advanced MDS FAB 
subtype than pretreatment 
Relapse after CR or PR 
At least 1 of the following:  
Return to pretreatment bone marrow blast percentage 
Decrement of t50% from maximum remission/response levels in granulocytes or platelets 
Reduction in Hemoglobin concentration by t1.5 g/dL or transfusion dependence 
Cytogenetic response 
Complete: Disappearance of the chromosomal abnormality without appearance of new ones 
Partial: At least 50% reduction of the chromosomal abnormality 
Disease progression 
For patients with: 
Less than 5% blasts: t 50% increase in blasts to > 5% blasts 
5-10% blasts: t 50% increase to > 10% blasts 
10-20% blasts: t 50% increase to > 20% blasts 
20-30% blasts: t 50% increase to > 30% blasts 
Any of the following: 
At least 50% decrement from maximum remission/response in granulocytes or platelets 
Reduction in Hemoglobin by t 2 g/dL 
Transfusion dependence 
Survival 
Endpoints: 
Overall: death from any cause 
Event free: failure or death from any cause 
PFS: disease progression or death from MDS 
DFS: time to relapse 
Cause-specific death: death related to MDS 
Adapted from Cheson, et al. Blood 2006; 108(2):419-25. 
Deletions to the IWG response criteria are not shown. To convert hemoglobin from g/dL to g/L, multiply g/dL by 10. 
MDS: myelodysplastic syndromes. Hgb: hemoglobin. CR: complete remission. HI: Hematologic improvement. PR: partial 
remission. FAB: French-American-British. AML: Acute myeloid leukemia. PFS: Progression-free survival. DFS: Disease-free 
survival. 
1 
Dysplastic changes should consider the normal range of dysplastic changes (modification) (Ramos 1999) 
2 
Modification to IWG response criteria 
3 
In some circumstances, protocol therapy may require the initiation of further treatment (e.g., consolidation, maintenance) 
before the 4-week period. Such patients can be included in the response category into which they fit at the time the therapy 
is started. Transient cytopenias during repeated chemotherapy courses should not be considered as interrupting durability of 
response, as long as they recover to the improved counts of the previous course. 

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Table 8: 
Stage 3A: 2015 MDS/MPN Response Criteria (Savona 2015) 
Criteria for measurement of treatment response in adult MDS/MPN 
CR (presence of all of the following improvements)1 
x 
Bone marrow:  
- 
 5% myeloblasts (including monocytic blast equivalent in case of CMML)  
- 
Normal maturation of all cell lines and return to normal cellularity1 
- 
Osteomyelofibrosis absent or equal to “mild reticulin fibrosis” ( grade 1 fibrosis)2 
x 
Peripheral blood3 
- 
WBC  10×109 cells/L 
- 
Hgb  11 g/dL 
- 
Platelets  100×109/L;  450×109/L 
- 
Neutrophils  1.0×109/L 
- 
Blasts 0% 
- 
Neutrophil precursors reduced to  2% 
- 
Monocytes  1×109/L 
x 
Extramedullary disease: Complete resolution of extramedullary disease present before therapy (e.g. 
cutaneous disease, disease-related serous effusions), including palpable hepatosplenomegaly 
x 
Persistent low-level dysplasia is permitted given subjectivity of assignment of dysplasia1 
Note:  Provisional category of CR with resolution of symptoms is removed from the original criteria.3 
Complete cytogenetic remission 
x 
Resolution of previously present chromosomal abnormality (known to be associated with 
myelodysplastic, syndrome myeloproliferative neoplasms, or MDS/MPN), as seen on classic 
karyotyping with minimal of 20 metaphases or FISH4 
Partial remission 
x 
Normalization of peripheral counts and hepatosplenomegaly with bone marrow blasts (and blast 
equivalents) reduced by 50%, but remaining > 5% of cellularity except in cases of MDS/MPN with 
 5% bone marrow blasts at baseline 
Marrow response 
x 
Optimal marrow response: Presence of all marrow criteria necessary for CR without normalization of 
peripheral blood indices as presented above 
x 
Partial marrow response: Bone marrow blasts (and blast equivalents) reduced by 50%, but remaining 
> 5% of cellularity, or reduction in grading of reticulin fibrosis from baseline on at least 2 bone marrow 
evaluations spaced at least 2 months apart 

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Criteria for measurement of treatment response in adult MDS/MPN 
Clinical benefit 
Requires 1 of the following in the absence of progression or CR/partial response and independent of marrow 
response (response must be verified at  8 weeks) to be considered a clinical benefit. (Note: “Cord blood 
response” was corrected to “response”.) 
x 
Erythroid response 
- 
Hgb increase by  2.0 g/dL 
- 
Transfusion independence for  8 weeks for patients requiring at least 4 packed red blood cell 
transfusions in the previous 8 weeks 
- 
Only red blood cell transfusions given based on physician’s judgement for a pretreatment Hgb of 
 8.5 g/dL will count in the red blood cell TI response evaluation5 
x 
Platelet response 
- 
Transfusion independence when previously requiring platelet transfusions of at least a rate of 
4 platelet transfusions in the previous 8 weeks 
- 
Pretreatment  20×109/L: increase from < 20×109/L to > 20×109/L and by at least 100% 
- 
Pretreatment > 20×109/L but  100×109/L: absolute increase of  30×109/L5 
x 
Neutrophil response 
- 
Pretreatment  0.5×109/L, at least 100% increase and an absolute increase  0.5×109/L 
- 
Pretreatment, > 0.5×109/L and  1.0×109/L, at least 50% increase and an absolute increase 
 0.5×109/L5 
x 
Spleen response 
- 
Either a minimum 50% reduction in palpable splenomegaly of a spleen that is at least 10 cm at 
baseline or a spleen that is palpable at more than 5 cm at baseline becomes not palpable 
x 
Symptom response (improvement in symptoms as noted by decrease of  50% as per the MPN-SAF TSS 
scoring < 20 were not considered eligible for measuring clinical benefit)6 
1 
Presence of dysplastic changes, which may be interpreted within the scope of normal range of dysplastic changes, may still 
exist in the presence of CR as allowed in MDS IWG. Marrow should exhibit age-adjusted normocellularity in CR. 
2 
If there is no significant fibrosis present on the initial bone marrow biopsy, a second biopsy is not required to prove 
resolution of fibrosis. Grading of fibrosis in measurement of treatment response should be according to the European 
Consensus System (Thiele 2005). 
3 
Given the current lack of a validated tool to assess complete resolution of symptoms in MDS/MPN, “CR with resolution of 
symptoms” (a complete resolution of disease-related symptoms as noted by the MPN-SAF TSS in presence of CR) will be a 
provisional category of disease response. 
4 
Loss of cytogenetic burden of disease (via FISH or classic karyotyping) known to adversely affect prognosis is required to 
reach complete cytogenetic remission. Decrease in the cytogenetic burden of disease must be by  50% (via FISH or classic 
karyotyping) to be indicative of a partial cytogenetic response. Given variability of fluorescent probes used in FISH, 
cytogenetic normalization via FISH will depend on the performance characteristics of the specific probes used. 
5 
Resolution of abnormal peripheral blood counts must persist for at least 2 separate analyses over at least 8 weeks. In the case 
of proliferative MDS/MPN, CR will include resolution of thrombocytosis to a normal platelet count (150-450×109/L) and 
resolution of leukocytosis to WBC 10×109 cells/L but 1.5×109/L. Hemoglobin should be maintained >11 g/dL and 
platelets 100×109/L without the support of transfusions. Clinical benefit may occur when these changes occur in absence of 
other changes required for CR or marrow response. Platelet and packed red blood cell TI would be considered for clinical 
benefit, and duration of TI should be monitored. Reduction in myeloid precursors (promyelocytes, myelocytes, 
metamyelocytes, nucleated red blood cells) to less than appreciable levels ( 2-3%) and/or 1 x 109/L monocytosis in the 
absence of infection, cytokine treatment, or other reactive causes. 
6 
MPN-SAF TSS validation among patients with MDS/MPN is currently under way (R.A. Mesa, personal communication, 
2014). 
 
 

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Criteria for measurement of disease progression in adult MDS/MPN 
Combination of 2 major criteria, 1 major and 2 minor criteria, or 3 minor criteria from list 
Major criteria 
x 
Increase in blast count1 
- 
< 5% blasts:  50% increase and to > 5% blasts 
- 
5-10% blasts:  50% increase and to > 10% blasts 
- 
10-20% blasts:  50% increase and to > 20% blasts 
- 
20-30% blasts:  50% increase and to > 30% blasts 2 
x 
Evidence of cytogenetic evolution3 
- 
Appearance of a previously present or new cytogenetic abnormality in complete cytogenetic 
remission via FISH or classic karyotyping. 
- 
Increase in cytogenetic burden of disease by  50% in partial cytogenetic remission via FISH or 
classic karyotyping. 
x 
New extramedullary disease. 
- 
Worsening splenomegaly: 
Progressive splenomegaly that is defined by IWG-MRT: the appearance of a previously absent 
splenomegaly that is palpable at > 5 cm below the left costal margin or a minimum 100% increase 
in palpable distance for baseline splenomegaly of 5-10 cm or a minimum 50% increase in palpable 
distance for baseline splenomegaly of > 10 cm 
Extramedullary disease outside of the spleen to include new/worsening hepatomegaly, granulocytic 
sarcoma, skin lesions, etc. 
Minor criteria 
x 
Transfusion dependence4 
x 
Significant loss of maximal response on cytopenias  50% decrement from maximum 
remission/response in granulocytes or platelets 
x 
Reduction in Hgb by  1.5 g/dL from best response or from baseline as noted on complete blood count 
x 
Increasing symptoms as noted by increase in  50% as per the MPN-SAF TSS5 
x 
Evidence of clonal evolution (molecular)6 
1 
Blasts as measured from the bone marrow. 
2 
Patients with development of acute myeloid leukemia from MDS/MPN; 20-30% blasts may be allowed on some clinical 
trials for patients with MDS/MPN. 
3 
Increase in cytogenetic burden of disease by  50% (via FISH or classic karyotyping). Given variability of fluorescent 
probes used in FISH, cytogenetic normalization via FISH will depend on specific probes used. 
4 
Transfusion dependency is defined by a history of at least 2 units of red blood cell transfusions in the past month for a 
hemoglobin level < 8.5 g/dL that was not associated with clinically overt bleeding. Cytopenia resulting from therapy should 
not be considered in assessment of progression. 
5 
MPN-SAF TSS validation among patients with MDS/MPN is currently under way (R.A. Mesa, personal communication, 
2014). 
6 
The identification of new abnormalities using single nucleotide polymorphism arrays or sequencing or a clearly significant 
increase in mutational burden of a previously detected abnormality. Precise criteria for defining new abnormalities and what 
exactly constitutes a significant increase in mutational burden are open to interpretation; we suggest that this criterion should 
be used conservatively based on current evidence. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
94 
The hematology community has recognized that a lack of a stable disease category in the 2015 
MDS/MPN IWG criteria creates considerable uncertainty in the categorization of patients on any 
CMML study. Therefore, the stable disease category defined as those patients not belonging to 
any of the defined categories in the 2015 criteria has been added as response criteria for CMML 
patients. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
Amendment 9 (Final): 30 September 2021 
95 
18.2 
ECOG Performance Status 
The ECOG performance status scale, with corresponding Karnofsky performance status score 
equivalents, is presented in Table 9. 
Table 9 
Eastern Cooperative Oncology Group Performance Status Scale, with 
Equivalent Karnofsky Performance Status Scores 
ECOG1 
Karnofsky2 
Score 
Criterion 
% 
Criterion 
0 
Normal activity 
100 
Normal; no complaints; no evidence of 
disease 
 
 
90 
Able to carry on normal activity; minor 
signs or symptoms of disease 
1 
Symptoms but ambulatory 
80 
Normal activity with effort; some signs or 
symptoms of disease 
 
 
70 
Cares for self; unable to carry on normal 
activity or do active work 
2 
In bed < 50% of time 
60 
Requires occasional assistance but is able 
to care for most of his/her needs 
 
 
50 
Requires considerable assistance and 
frequent medical care 
3 
In bed > 50% of time 
40 
Disabled, requires special care and 
assistance 
 
 
30 
Severely disabled; hospitalization is 
indicated though death is not imminent 
4 
100% bedridden 
20 
Very sick; hospitalization is necessary 
 
 
10 
Moribund; fatal processes progressing 
rapidly 
5 
Dead 
0 
Dead 
1 
Oken MM, Creech RH, Tormey DC, Horton J, Davis TE, McFadden ET, Carbone PP. Toxicity and response criteria of the 
Eastern Cooperative Oncology Group. Am J Clin Oncol. 1982;5:649-655. 
2 
Mor V, Laliberte L, Morris JN, Wiemann M. The Karnofsky Performance Status Scale: an examination of its reliability and 
validity in a research setting. Cancer. 1984;53:2002-2007. 

Tagraxofusp (SL-401; Diphtheria Toxin Interleukin-3 Fusion Protein) 
Stemline Therapeutics, Inc. 
 
 
Protocol STML-401-0314 
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96 
CONFIDENTIAL 
18.3 
CLS Management Guidance 
Time of Presentation 
CLS 
Sign/Symptom 
Recommended Action 
Tagraxofusp Dosing 
Management 
Prior to first dose of 
tagraxofusp in Cycle 1  
Serum albumin < 3.2 g/dL  
Administer tagraxofusp when serum albumin  3.2 g/dL. 
During tagraxofusp dosing 
Serum albumin < 3.5 g/dL  
Administer 25g intravenous albumin (q12h or more 
frequently as practical) until serum albumin is  3.5 g/dL 
AND not more than 0.5 g/dL lower than the value measured 
prior to dosing initiation of the current cycle. 
Interrupt tagraxofusp 
dosing until the 
relevant CLS 
sign/symptom has 
resolved1. 
Serum albumin reduced by  0.5 g/dL 
from the albumin value measured prior 
to tagraxofusp dosing initiation of the 
current cycle 
A predose body weight that is increased 
by  1.5 kg over the previous day’s 
predose weight 
Administer 25g intravenous albumin (q12h or more 
frequently as practical), and manage fluid status as indicated 
clinically (e.g., generally with intravenous fluids and 
vasopressors if hypotensive and with diuretics if 
normotensive or hypertensive), until body weight increase 
has resolved (i.e. the increase is no longer  1.5 kg greater 
than the previous day’s predose weight). 
Edema, fluid overload and/or 
hypotension 
Administer 25g intravenous albumin (q12h, or more 
frequently as practical) until serum albumin is  3.5 g/dL. 
 
Administer 1 mg/kg of methylprednisolone (or an 
equivalent) per day, until resolution of CLS sign/symptom 
or as indicated clinically. 
 
Aggressive management of fluid status and hypotension if 
present, which could include intravenous fluids and/or 
diuretics or other blood pressure management, until 
resolution of CLS sign/symptom or as clinically indicated.  
1 Tagraxofusp administration may resume in the same cycle if all CLS signs/symptoms have resolved and the patient did not require measures to treat 
hemodynamic instability. Tagraxofusp administration should be held for the remainder of the cycle if CLS signs/symptoms have not resolved or the patient 
required measures to treat hemodynamic instability (e.g. required administration of intravenous fluids and/or vasopressors to treat hypotension) (even if 
resolved), and tagraxofusp administration may only resume in the next cycle if all CLS signs/symptoms have resolved, and the patient is hemodynamically 
stable.