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Abbreviated Title: PLX038 and Rucaparib NIH **Protocol:** 20-C-0013 Version Date: 02/02/2023 NCT Number: NCT04209595 Title: Phase I/II trial of PLX038 (PEGylated SN38) and Rucaparib in Solid tumors and Small Cell Cancers NCI Principal Investigator: Anish Thomas, MD
Developmental Therapeutics Branch (DTB) National Cancer Institute (NCI) 10 Center Drive, Room 4-5330 Bethesda, MD 20892 Phone: 240-760-7343 E-mail: anish.thomas@nih.gov  
| Drug Name:    | PLX038 (PEGylated SN38)   | Rucaparib             |
|---------------|---------------------------|-----------------------|
| IND Number:   | 145310                    | 145310                |
| Sponsor:      | CCR, NCI                  | CCR, NCI              |
| Manufacturer: | ProLynx LLC               | Clovis Oncology, Inc. |
| Supplier:     | ProLynx LLC               | Clovis Oncology, Inc. |  
Safety Monitoring Committee (SMC): NCI SMC
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precis

Background:  
- We hypothesize that a dose-escalation strategy that incorporates tumor targeted DNAdamaging chemotherapy and DNA-damage response (DDR) inhibitors could allow safe and effective administration of DDR inhibitor-chemotherapy combination.  
- PLX038 is a PEGylated conjugate of SN38 with improved properties including increased solubility, higher exposure and longer half-life. SN-38 is the active metabolite of CPT-11 (irinotecan) that inhibits topoisomerase 1 (Top1) and causes DNA strand breakage. As a specific DNA damaging agent, SN-38 enhances cell kill in tumors deficient in the DNAdamage response and when combined with inhibitors of the DDR.  
- Rucaparib is a potent oral poly ADP ribose polymerase (PARP) inhibitor that is approved for the maintenance treatment of participants with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinumbased chemotherapy.  
- We hypothesize that the combination of PLX038 plus rucaparib is more efficacious than either agent alone.
Objectives:
- Phase I: To identify the maximum tolerated dose (MTD) of PLX038 in combination with rucaparib.  
- Phase II: To assess the efficacy with respect to clinical benefit rate (CBR) (CR+PR+SD)
for 4 months according to Response Evaluation Criteria (RECIST 1.1) of a combination of PLX038 and rucaparib in participants with small cell lung cancer and extra-pulmonary small cell carcinomas.
Eligibility:  
- Subjects with histologically confirmed solid tumors (Phase I) OR histologically or cytologically confirmed small cell lung cancer (SCLC) (Phase II) OR histologically or cytologically confirmed extra-pulmonary small cell carcinomas (Phase II).  
- Age ≥18 years - Subjects must have evaluable or measurable disease.  
- ECOG performance status ≤ 2
- Adequate organ function
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design

- This is an open label Phase I/II trial accruing initially one cohort to determine maximum tolerated dose (MTD) of combined treatment of PLX038 and rucaparib (Phase I); and to examine the safety and efficacy of PLX038 in combination with rucaparib in the following cohort (Phase II).  
- PLX038 will be administered by IV infusion on day 1 of every 21-days cycle, rucaparib will be administered PO twice daily on days 6 to 19 of every cycle.  
- Treatment will continue until progression or unacceptable toxicity. - Biomarkers of participant response to treatment will be investigated in an exploratory manner pre and post-treatment.
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| TABLE OF CONTENTS                                                                              |                                                                                                                      |                    |
|------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------|--------------------|
| PRÉCIS .                                                                                       |                                                                                                                      |                    |
| TABLE OF CONTENTS.                                                                             |                                                                                                                      |                    |
| STATEMENT OF COMPLIANCE                                                                        |                                                                                                                      |                    |
| INTRODUCTION .                                                                                 |                                                                                                                      |                    |
| 1                                                                                              | 1.1                                                                                                                  | Study Objectives . |
| Primary Objectives                                                                             |                                                                                                                      |                    |
| 1.1.1                                                                                          |                                                                                                                      |                    |
| 1.1.2                                                                                          | Secondary Objectives                                                                                                 |                    |
| Exploratory Objectives .                                                                       |                                                                                                                      |                    |
| 1.1.3                                                                                          |                                                                                                                      |                    |
| 1.2                                                                                            | Background and Rationale .                                                                                           |                    |
| 1.2.1                                                                                          | Small cell lung cancer (SCLC) and extrapulmonary small cell carcinoma. .......... 12                                 |                    |
| 1.2.2                                                                                          | SN-38 and PLX038                                                                                                     |                    |
| 1.2.3                                                                                          | Rucaparib                                                                                                            |                    |
| 1.2.4                                                                                          | Rationale for this study .                                                                                           |                    |
| 1.2.5                                                                                          | Rationale for Amendment to Change Dose-Escalation Strategy (Amendment                                                |                    |
| Version Date: 03/19/2021)                                                                      |                                                                                                                      |                    |
| 1.2.6                                                                                          | Additional Summary Safety and Efficacy Results and Rationale for Further                                             |                    |
| Changes to Dose Escalation Strategy (as of amendment version date: 04/08/2022) ............ 33 |                                                                                                                      |                    |
| 2                                                                                              | ELIGIBILITY ASSESSMENT AND ENROLLMENT.                                                                               |                    |
| 2.1                                                                                            | Eligibility Criteria .                                                                                               |                    |
| 2.1.1                                                                                          | Inclusion Criteria .                                                                                                 |                    |
| 2.1.2                                                                                          | Exclusion Criteria .                                                                                                 |                    |
| 2.1.3                                                                                          | Recruitment Strategies .                                                                                             |                    |
| 2.2                                                                                            | Screening Evaluation                                                                                                 |                    |
| 2.2.1                                                                                          | Screening activities performed prior to obtaining informed consent....................... 40                         |                    |
| 2.2.2                                                                                          | Screening activities performed after a consent for screening has been signed...... 40                                |                    |
| 2.3                                                                                            | Participant Registration and Status Update Procedures ........................................................... 41 |                    |
| 2.3.1                                                                                          | Treatment Assignment Procedures                                                                                      |                    |
| 2.4                                                                                            | Baseline Evaluation                                                                                                  |                    |
| STUDY IMPLEMENTATION .                                                                         |                                                                                                                      |                    |
| 3                                                                                              | 3.1                                                                                                                  | Study Design .     |
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abbreviated title plx038 and rucaparib

| Version Date: 02/02/2023    |                                                                                                                 |
|-----------------------------|-----------------------------------------------------------------------------------------------------------------|
| 3.1.1                       | Dose Limiting Toxicity                                                                                          |
| 3.1.2                       | Phase I Cohort                                                                                                  |
| Phase II Cohorts .          |                                                                                                                 |
| 3.1.3                       |                                                                                                                 |
| 3.2                         | Study Stopping Rules .                                                                                          |
| 3.3                         | D Drug Administration                                                                                           |
| 3.3.1                       | PLX038 .                                                                                                        |
| 3.3.2                       | Rucaparib                                                                                                       |
| Dose Delay or Modifications |                                                                                                                 |
| 3.4                         |                                                                                                                 |
| 3.4.1                       | Phase I during evaluation period                                                                                |
| 3.4.2                       | Phase I after DLT evaluation period and Phase II ........................................................... 46 |
| 3.5                         | Study Calendar .                                                                                                |
| 3.6                         | Cost and Compensation                                                                                           |
| 3.6.1                       | Costs                                                                                                           |
| 3.6.2                       | COMPENSATION .                                                                                                  |
| 3.6.3                       | Reimbursement                                                                                                   |
| 3.7                         | Criteria for Removal from Protocol Therapy and Off Study Criteria ................................. 52          |
| 3.7.1                       | Criteria for Removal from Protocol Therapy                                                                      |
| 3.7.2                       | OFF -Study Criteria                                                                                             |
| 3.7.3                       | Lost to Follow-up                                                                                               |
| 4                           | CONCOMITANT MEDICATIONS/MEASURES .                                                                              |
| 4.1                         | Prohibited Medications .                                                                                        |
| 4.1.1                       | Strong inducers or inhibitors of CYP3A4 and UGT1A1 inhibitors ........................ 53                       |
| 4.2                         | Required Medication                                                                                             |
| 4.2.1                       | G-CSF                                                                                                           |
| 4.3                         | Recommended Medication                                                                                          |
| S                           | CORRELATIVES STUDIES FOR RESERACH                                                                               |
| 5.1                         | Biospecimen Collection .                                                                                        |
| 5.2                         | Collection of Samples                                                                                           |
| 5.2.1                       | Blood                                                                                                           |
| 5.2.2                       | T Tumor samples                                                                                                 |
| 5.2.3                       | Hair follicles                                                                                                  |
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abbreviated title plx038 and rucaparib

| 5.3                                                                                                                          | Correlative Studies for Research 57                                                  |
|------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------|
| 5.3.1                                                                                                                        | Pharmacokinetic analysis 57                                                          |
| 5.3.2                                                                                                                        | The formation of γH2AX foci 57                                                       |
| 5.3.3                                                                                                                        | PARP inhibition 57                                                                   |
| 5.3.4                                                                                                                        | SLFN11 58                                                                            |
| 5.3.5                                                                                                                        | Immune Subset Analysis 58                                                            |
| 5.3.6                                                                                                                        | Circulating Tumor DNA 59                                                             |
| 5.3.7                                                                                                                        | Interference of PLX038 with coagulation assays 59                                    |
| 5.3.8                                                                                                                        | SLFN11 Expression 60                                                                 |
| 5.3.9                                                                                                                        | RNAseq and Whole Exome Sequencing 60                                                 |
| 5.3.10                                                                                                                       | Management of Results 60                                                             |
| 5.3.11                                                                                                                       | Genetic Counseling 60                                                                |
| 5.4                                                                                                                          | Sample Storage, Tracking And Disposition 61                                          |
| 5.4.1                                                                                                                        | Samples Managed by Dr. Figg's Blood Processing Core (BPC) 61                         |
| 5.4.2                                                                                                                        | Procedures for storage of participant samples in the Laboratory of Jane Trepel 62    |
| 5.4.3                                                                                                                        | Procedures for storage of participant samples in the Laboratory of Dr. Redon 62      |
| 5.4.4                                                                                                                        | Procedures for Storage of Tissue Specimens in the Laboratory of Pathology 63         |
| 5.4.5                                                                                                                        | Procedures for storage of tissue and blood samples in the Laboratory of Dr. Kumar 63 |
| 5.4.6                                                                                                                        | Procedures for Storage of PLX038 Coagulation Assay Blood Samples in the              |
| Department of Laboratory Medicine (DLM) 64 5.4.7 Protocol Completion/Sample Destruction 64 DATA COLLECTION AND EVALUATION 64 |                                                                                      |
| 6.1                                                                                                                          | Data Collection 64                                                                   |
| 6.2                                                                                                                          | Data Sharing Plans 65                                                                |
| 6.2.1                                                                                                                        | Human Data Sharing Plan 65                                                           |
| 6.2.2                                                                                                                        | Genomic Data Sharing Plan 65                                                         |
| 6.3                                                                                                                          | Response Criteria 65                                                                 |
| 6.3.1                                                                                                                        | Disease Parameters 66                                                                |
| 6.3.2                                                                                                                        | Methods for Evaluation of Measurable Disease 67                                      |
| 6.3.3                                                                                                                        | Response Criteria 68                                                                 |  
| 6.4                                                                                                                                | Toxicity Criteria                                                                                                                     |
|------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------|
| 7                                                                                                                                  | NIH REPORTING REQUIREMENTS / DATA AND SAFETY MONITORING PLAN.. 70                                                                     |
| 7.1                                                                                                                                | DEFINITIONS                                                                                                                           |
| 7.2                                                                                                                                | OHSRP Office of Compliance and Training / IRB Reporting ........................................... 70                                |
| 7.2.1                                                                                                                              | Expedited Reporting                                                                                                                   |
| 7.2.2                                                                                                                              | IRB Requirements for PI Reporting at Continuing Review ....................................... 71                                     |
| 7.3                                                                                                                                | NCI Clinical Director Reporting                                                                                                       |
| 7.4                                                                                                                                | NIH Required Data and Safety Monitoring Plan ......................................................................... 71             |
| Principal Investigator/Research Team .......................................................................................... 71 |                                                                                                                                       |
| 7.4.1                                                                                                                              |                                                                                                                                       |
| 7.4.2                                                                                                                              | Safety Monitoring Committee (SMC) ................................................................................................ 71 |
| 8                                                                                                                                  | SPONSOR PROTOCOL/SAFETY REPORTING.                                                                                                    |
| 8.1                                                                                                                                | Definitions                                                                                                                           |
| 8.1.1                                                                                                                              | A Adverse Event                                                                                                                       |
| 8.1.2                                                                                                                              | Serious Adverse Event (SAE)                                                                                                           |
| 8.1.3                                                                                                                              | Life-threatening                                                                                                                      |
| 8.1.4                                                                                                                              | Severity .                                                                                                                            |
| 8.1.5                                                                                                                              | Relationship to Study Product                                                                                                         |
| 8.1.6                                                                                                                              | Adverse Events of Special Interest (AESI)                                                                                             |
| Assessment of Safety Events                                                                                                        |                                                                                                                                       |
| 8.2                                                                                                                                |                                                                                                                                       |
| 8.3                                                                                                                                | Reporting of Serious Adverse Events                                                                                                   |
| 8.4                                                                                                                                | Waiver of Expedited Reporting to CCR .                                                                                                |
| 8.5                                                                                                                                | Safety Reporting Criteria to the Pharmaceutical Collaborators ........................................... 74                          |
| 8.6                                                                                                                                | Reporting Pregnancy                                                                                                                   |
| 8.6.1                                                                                                                              | Maternal exposure                                                                                                                     |
| 8.6.2                                                                                                                              | Paternal exposure                                                                                                                     |
| 8.7                                                                                                                                | Regulatory Reporting for Studies Conducted Under CCR-Sponsored IND .................. 75                                              |
| 8.8                                                                                                                                | Sponsor Protocol Deviation Reporting .                                                                                                |
| CLINICAL MONITORING                                                                                                                |                                                                                                                                       |
| 9                                                                                                                                  |                                                                                                                                       |
| 10                                                                                                                                 | STATISTICAL CONSIDERATIONS                                                                                                            |
| Study Objective                                                                                                                    |                                                                                                                                       |
| 10.1                                                                                                                               |                                                                                                                                       |
| 10.1.1                                                                                                                             | Primary Objectives                                                                                                                    |
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abbreviated title plx038 and rucaparib

| Version Date: 02/02/2023   |                                                                                                              |                                                                                               |
|----------------------------|--------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------|
| 10.1.2                     | Secondary Objectives                                                                                         |                                                                                               |
| 10.2                       | Sample Size Determination                                                                                    |                                                                                               |
| Populations for Analyses . |                                                                                                              |                                                                                               |
| 10.3                       |                                                                                                              |                                                                                               |
| 10.4                       | Statistical Analyses                                                                                         |                                                                                               |
| General Approach .         |                                                                                                              |                                                                                               |
| 10.4.1                     |                                                                                                              |                                                                                               |
| 10.4.2                     | Analysis of the Primary Efficacy Endpoints                                                                   |                                                                                               |
| 10.4.3                     | Analysis of the Secondary Efficacy Endpoints............................................................. 78 |                                                                                               |
| Se                         |                                                                                                              |                                                                                               |
| 10.4.4                     |                                                                                                              |                                                                                               |
| 10.4.5                     | Baseline Descriptive Statistics                                                                              |                                                                                               |
| Planned Interim Analyses . |                                                                                                              |                                                                                               |
| 10.4.6                     |                                                                                                              |                                                                                               |
| 10.4.7                     | Exploratory Analyses                                                                                         |                                                                                               |
| COLLABORATIVE AGREEMENT    |                                                                                                              |                                                                                               |
| 11                         | 1.1                                                                                                          | Cooperative Research and Development Agreement (CRADA) ................................... 79 |
| 1.2                        | Clinical Trial Agreement (CTA) .                                                                             |                                                                                               |
| 12                         | HUMAN SUBJECTS PROTECTIONS .                                                                                 |                                                                                               |
| 12.1                       | Rationale for Subject Selection                                                                              |                                                                                               |
| 12.2                       | Participation of Children                                                                                    |                                                                                               |
| 12.3                       | Evaluation of Benefits and Risks/Discomforts                                                                 |                                                                                               |
| 12.3.1                     | Benefits .                                                                                                   |                                                                                               |
| 12.3.2                     | Risks                                                                                                        |                                                                                               |
| 12.3.3                     | Assessment of Potential Risks and Benefits .                                                                 |                                                                                               |
| 12.4                       | Consent Process and Documentation                                                                            |                                                                                               |
| 13                         | REGULATORY AND OPERATIONAL CONSIDERATIONS                                                                    |                                                                                               |
| 13.1                       | Study Discontinuation and Closure                                                                            |                                                                                               |
| 13.2                       | Quality Assurance and Quality Control                                                                        |                                                                                               |
| 13.3                       | Conflict of Interest Policy.                                                                                 |                                                                                               |
| 13.4                       | Confidentiality and Privacy                                                                                  |                                                                                               |
| 14                         | PHARMACEUTICAL INFORMATION                                                                                   |                                                                                               |
| 14.1                       | PLX038 (IND 145310)                                                                                          |                                                                                               |
| SOURCE .                   |                                                                                                              |                                                                                               |
| 14.1.1                     |                                                                                                              |                                                                                               |
| 14.1.2                     | Acquisition and Accountability .                                                                             |                                                                                               |  
| 14.1.3       | Formulation and Preparation                                                                                                             |
|--------------|-----------------------------------------------------------------------------------------------------------------------------------------|
| 14.1.4       | Stability and Storage                                                                                                                   |
| 14.1.5       | Administration Procedures                                                                                                               |
| 14.1.6       | Toxicity .                                                                                                                              |
| 14.2         | Rucaparib (IND 145310) .                                                                                                                |
| 14.2.1       | SOURCE .                                                                                                                                |
| 14.2.2       | Acquisition and Accountability .                                                                                                        |
| 14.2.3       | Formulation and Preparation                                                                                                             |
| 14.2.4       | How Supplied                                                                                                                            |
| 14.2.5       | Administration .                                                                                                                        |
| 14.2.6       | T Toxicity .                                                                                                                            |
| REFERENCES . |                                                                                                                                         |
| 15           |                                                                                                                                         |
| 16           | APPENDICES                                                                                                                              |
| 16.1         | Appendix A - Performance Status Criteria ........................................................................................... 92 |
| 16.2         | Appendix B - Patient's Medication Diary ....................................................................................... 93      |
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statement of compliance

The trial will be carried out in accordance with International Conference on Harmonisation Good Clinical Practice (ICH GCP) and the following:
- United States (US) Code of Federal Regulations (CFR) applicable to clinical studies (45 CFR Part 46, 21 CFR Part 50, 21 CFR Part 56, 21 CFR Part 312, and/or 21 CFR Part 812)
National Institutes of Health (NIH)-funded investigators and clinical trial site staff who are responsible for the conduct, management, or oversight of NIH-funded clinical trials have completed Human Subjects Protection and ICH GCP Training. The protocol, informed consent form(s), recruitment materials, and all participant materials will be submitted to the Institutional Review Board (IRB) for review and approval. Approval of both the protocol and the consent form must be obtained before any participant is enrolled. Any amendment to the protocol will require review and approval by the IRB before the changes are implemented to the study. In addition, all changes to the consent form will be IRB-approved; an IRB determination will be made regarding whether a new consent needs to be obtained from participants who provided consent, using a previously approved consent form.
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introduction 1.1 study objectives

1.1.1 Primary Objectives
- Phase I: To identify the maximum tolerated dose (MTD) of PLX038 in combination with rucaparib.  
- Phase II: To assess the efficacy with respect to clinical benefit rate (CBR) (CR+PR+SD)
for 4 months according to Response Evaluation Criteria (RECIST 1.1) of a combination of PLX038 and rucaparib in participants with small cell lung cancer.  
1.1.2 Secondary Objectives
- To assess safety and tolerability of combined treatment of PLX038 and rucaparib
- To determine the progression-free survival (PFS) in Phase II - To determine overall survival (OS) in Phase II  
- To assess the clinical response rate (CRR) (CR+PR) according to Response Evaluation Criteria (RECIST 1.1) in participants with small cell lung cancer.  
1.1.3 Exploratory Objectives
- To identify pharmacodynamic markers of response including γ H2AX
- To identify predictors of response
- To assess pharmacokinetics of PLX038 and rucaparib - To preliminarily assess the clinical outcomes of participants with extrapulmonary SCLC  
- To describe and investigate the interference of PLX038 with coagulation assays
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1.2 background and rationale

PARP inhibitors are now approved for various indications and are under investigation for various tumor types. Despite promising preclinical data, chemotherapy-PARP inhibitor combinations have proved challenging in clinic. Dose limiting toxicities, specifically myelosuppression, has severely limited the ability to dose escalate both PARP inhibitors (PARPi) and chemotherapy in several clinical studies [1-7] (**Table 1**). We hypothesize that a dose-escalation strategy that incorporates tumor targeted DNA-damaging chemotherapy and DDR inhibitors could allow higher dose administration of DDR inhibitor-chemotherapy combinations. Combinations of PARP inhibitors with DNA damaging chemotherapy is likely to be most effective in high replicative (HR) stress tumors[8] and in tumors with defects in DNA repair pathways including HR stress tumors such as ovarian, breast, and prostate cancers.  
| Table 1. Trials of PARP inhibitors with topoisomerase inhibitors Combination MTD Topo 1 inhibitors PARPi   | DLT       | Ref                                              |                  |      |                    |     |
|------------------------------------------------------------------------------------------------------------|-----------|--------------------------------------------------|------------------|------|--------------------|-----|
| %                                                                                                          | of        |                                                  |                  |      |                    |     |
| MTD                                                                                                        |           |                                                  |                  |      |                    |     |
| %                                                                                                          | of        |                                                  |                  |      |                    |     |
| MTD                                                                                                        |           |                                                  |                  |      |                    |     |
| Irinotecan                                                                                                 | Olaparib  | Irinotecan 200 mg/m2 ;  q3w                      | 57%              | 6%   | Diarrhea,          | [5] |
| myelosuppression                                                                                           |           |                                                  |                  |      |                    |     |
| Olaparib 50 mg qd  days 1-21 Irinotecan 125 mg/m2 q2w                                                      | ≈69%      | ≈12%                                             | Anorexia/fatigue |      |                    |     |
| Olaparib 50 mg bid  days 1-5                                                                               |           |                                                  |                  |      |                    |     |
| Irinotecan                                                                                                 | Veliparib | Irinotecan 100 mg/m2 days 1, 8; subsequent q3w   | ≈80              | ≈10% | Diarrhea, fatigue, | [2] |
| myelosuppression                                                                                           |           |                                                  |                  |      |                    |     |
| Veliparib 40 bid days  1-14                                                                                |           |                                                  |                  |      |                    |     |
| Topotecan                                                                                                  | Olaparib  | Topotecan 1 mg/m2 on  days 1-3; subsequent q3w   | ≈40%             | 25%  | Myelosuppression   | [3] |
| Olaparib 100 mg bid  days 1-21                                                                             |           |                                                  |                  |      |                    |     |
| Topotecan                                                                                                  | Veliparib | Topotecan 0.6 mg/m2 on days 1-5;  subsequent q3w | 40%              | ≈3%  | Myelosuppression   | [4] |
| Veliparib 10 bid days  1-5                                                                                 |           |                                                  |                  |      |                    |     |  
1.2.1 Small cell lung cancer (SCLC) and extrapulmonary small cell carcinoma. Small cell lung cancer (SCLC) is the most aggressive and lethal form of lung cancer. Because of frequent chromosomal alterations, dysregulation of genes that promote replication origin firing
(e.g., MYC) and the high expression of DNA damage repair proteins, we have postulated that SCLC has high levels of endogenous replicative DNA replication forks due to various perturbations that interfere with replication [9]. SCLC represents 15% of all lung cancers, with an annual incidence of over 34,000 cases in the United States alone. SCLC is characterized by rapid doubling time, high growth fraction and early and widespread metastatic involvement [10]. Response rates to first-line chemotherapy are exceptionally high, on the order of 60% to 70%. Unfortunately, these responses are also disappointingly transient, with median PFS of <5 months [11, 12] and nearly all participants relapse within one year. Extensive-stage SCLC is generally unresponsive to chemotherapy at relapse, and fewer than 5% of participants survive for two years [10]. Treatment of SCLC as well as survival after a diagnosis of SCLC have not changed substantially in the past 30 years [13]. Due to an urgent need for effective interventions in this disease, SCLC was singled out by the NCI as a designated "recalcitrant" cancer based on incidence rate, exceptionally high lethality, and the lack of substantial therapeutic progress made over several decades [14]. At the time of diagnosis most participants (60-70%) have extensive-stage (ES) disease, defined as cancer that has spread beyond the ipsilateral lung and regional lymph nodes and cannot be included in a single radiation field [10]. The primary treatment modality for participants with ES-SCLC is systemic chemotherapy consisting of platinum and etoposide followed by prophylactic cranial irradiation in participants with a response [15]. Both topotecan and irinotecan are active in relapsed SCLC. Topotecan is Food and Drug Administration (FDA)-approved for participants with SCLC with chemotherapy-sensitive disease after failure of first-line chemotherapy. Extrapulmonary small cell carcinoma is a distinct clinicopathologic entity that can arise in a wide range of extrapulmonary sites. These tumors have been described most frequently in the bladder, prostate, esophagus, stomach, colon and rectum, gallbladder, larynx, salivary glands, cervix, and skin. They are extremely rare and management of systemic disease with chemotherapy is patterned the approach used in SCLC[16].  
Camptothecins are an active drug class in SCLC. Both irinotecan [17] and topotecan [18] are used in the first and second line setting respectively as part of standard care. Drugs that target DNA damage response (DDR), including PARP inhibitors, have shown promising activity against SCLC in pre-clinical models and in early clinical trials. Proteomic profiling of a large panel of SCLC cell lines led to the observation that PARP1, Chk1, and several other DNA repair proteins are expressed at high levels in SCLC [19]. These studies also confirmed PARP1 overexpression in participant tumors at the protein level by immunohistochemistry and at the mRNA level. Based on this finding, several PARP inhibitors were tested in pre-clinical models of SCLC. Olaparib, rucaparib, and talazoparib (BMN-673) all demonstrated striking single agent activity in a majority of SCLC cell lines tested. Furthermore, the addition of a PARP inhibitor to standard chemotherapies (e.g., cisplatin, etoposide and/or topotecan) and radiation further potentiated their effect [20]. In animal models including xenografts and participant-derived xenografts (PDXs), talazoparib has demonstrated significant anti-tumor activity as a single agent, comparable or superior to cisplatin [21]. Following these observations, several clinical trials were initiated to investigate the effects of PARP inhibition in SCLC participants. Single-agent talazoparib was tested in an expansion cohort of participants with platinum-sensitive SCLC relapse [22]. Two of 23 participants had a partial response (PR; objective response rate (ORR), 9%, with duration of response 12.0 and 15.3 weeks, respectively), and a further 4 had SD lasting at least 16 weeks (CBR, 26% ≥16 weeks). Additional studies have also evaluated the combination of PARP inhibitors and DNA damaging chemotherapy in SCLC. Based on phase 2 data showing activity of temozolomide (TMZ) in relapsed SCLC and preclinical data demonstrating activity of TMZ in combination with PARP inhibitors [23], clinical trials have tested this combination in SCLC. In one study [24], 104 relapsed SCLC participants were randomly assigned 1:1 to oral veliparib or placebo plus temozolomide. Four-month PFS and median OS did not differ between the two arms, whereas a significant improvement in ORR was observed with TMZ/veliparib. SLFN11 expression was associated with improved PFS and OS in participants receiving TMZ/veliparib. In preclinical SCLC models, PARP inhibition has been reported to down regulate key components of the DNA repair machinery and enhance the efficacy of chemotherapy [19]. PARP inhibition sensitizes cancer cells both to cytotoxic chemotherapy, such as alkylators (temozolomide, cyclophosphamide) or camptothecins (irinotecan, topotecan) and to ionizing radiation - all of which induce DNA damage requiring base excision repair (BER) [25]. PARP inhibitors are highly effective in combination with camptothecins in tumors with and without defects in homologous recombination [26-29]. The Pommier laboratory has demonstrated highly synergistic activity of olaparib in combination with camptothecins [29]. They observed that the synergistic activity is due to its catalytic PARP inhibitory activity rather than due to trapping of PARP-DNA complexes.
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1.2.2 sn-38 and plx038

SN-38 is the active metabolite of CPT-11 (irinotecan) that inhibits topoisomerase I and causes DNA strand breakage. As a specific DNA damaging agent, SN-38 enhances cell kill in tumors deficient in the DNA-damage response (DDR; e.g. BRCA1/2-deletions) and when combined with inhibitors of the DDR (e.g. PARP inhibitors). PLX038 (PEG40kDa~SN-38) is a 4-arms 40 kDa PEG
that has SN-38 attached by a slowly cleavable releasable linker to the ends of each arm; the speciesindependent in vivo release rate of SN-38 is very long - 350 hr. [30].  
For complete safety and efficacy information, refer to investigator brochure.
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1.2.2.1 preclinical efficacy studies of

Although the renal clearance of PLX038 in the mouse was too rapid to allow its use in this animal model, preclinical pharmacology studies showed high antitumor activity - comparable or better than CPT-11 - in numerous xenografts in the nude rat. An analog of PLX038 - PLX038A - was designed to mimic human pharmacokinetics of PLX038 in the mouse, and preclinical studies were performed using the BRCA1-deficient, TNBC MX-1 xenograft the mouse. Single, nontoxic doses of PLX038A completely inhibited growth of MX-1 tumors and shrank massive tumors to undetectable levels. Using PET-imaging studies of an 89Zr surrogate of PLX038, we showed that PEG40kDa~SN-38 accumulated to a very high ~15% ID in the tumor and remained there for long periods (t1/2~14 days). Hence, we envisioned that we could "pre-load" a tumor with PEG40kDa~SN-38, allow the drug to clear systemically, and then treat with a PARP inhibitor; here, only the tumor would be exposed to both drugs concomitantly, and marrow toxicity of the combination might not occur. When used in combination with sub-therapeutic QD dose PARP inhibitor, talazoparib, a single low sub-therapeutic dose of PLX038A (10% of single dose) caused complete tumor inhibition and shrinkage of large tumors. Importantly, when the same sub-therapeutic dose of PLX038A was administered as a single agent, followed by a systemic washout of drug (4-half-lives of renal elimination), administration of the same sub-therapeutic QD dose of PARP inhibitor caused complete growth inhibition. In these combination studies, we did not observe weight loss or marrow toxicity.
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1.2.2.2 preclinical toxicology of plx038

Maximum tolerated dose (MTD)/dose range finding (DRF), acute dose, 14 day and 28 day repeat intravenous (IV) PLX038 dosing studies were conducted in rats and monkeys. Based on the dosing studies, the primary target organs are the bone marrow, gastrointestinal tract and skin. The monkey was the more sensitive species.  
In rats, single IV doses up to 1,000 mg/kg and repeat weekly injections up to 800 mg/kg was welltolerated. Rats that received repeat weekly injections of 800 mg/kg had decreased thymic weight and bone marrow hypocellularity attributed to PLX038. High doses of PLX038 caused decreases in clinical chemistries and hematology, increased aPTT and PT and decreased food consumption. In monkeys, a single large IV dose of 1,000 mg/kg and repeat weekly injections of ≥ 600 mg caused lethality. Cause of death was uncertain. Bone marrow depletion with correlating changes, with or without evidence of secondary infections, were possible contributing factors to the deaths. Macroscopic multifocal red discoloration and acute inflammation of gastrointestinal organs were also noted, probably related to PLX038. In surviving monkeys, a dose-dependent increase in diarrhea was noted. All animals experienced decreases in clinical chemistries and hematology that were reversible. At autopsy, bone marrow hypocellularity, decreased thymic and spleen size were detected. Macroscopic changes in the gastrointestinal epithelium (inflammation, multifocal lesions) were also noted, thought to be caused by PLX038. In the 4-week repeat dose study in monkey, small to large cornea pigmentation was observed in monkeys in all treatment groups at the end of the dosing period. In some cornea pigmentation persisted and was still present at the end of the recovery period. Two monkeys in the low dose (200 mg/kg) group that did not have cornea staining on Day 25 developed medium pigmentation on Day 50 suggesting a possible delayed effect. Due to the observation of cornea pigmentation in all treatment groups, no no-effect-level (NOAEL) could be determined in the 4-week repeat dose study. In both rats and monkeys, histopathology revealed mild to moderate vacuolation in several tissues. 1.2.2.3 Phase 1 dose escalation of PLX038 The Phase 1 dose escalation trials are being performed in single-dose cohorts at MD Anderson, with Dr. Jaffer Ajani as PI, and Theradex Oncology as CRO. **Table 4** shows the current study enrollment through Participant 38 (including 4 screen failure patients) and describes the dose level, cancer type, and other relevant information. To date in the Phase I study D15-11073, 34 patients have received PLX038 treatment at doses ranging from 115 mg/m2to 3060 mg/m2(corresponding to ~1 to 32 mg/m2released SN38) q3w in 21-day cycles. The study is ongoing.  
Treatment emergent adverse events (TEAEs) during Study D15-11073 have been reported for all 34 safety evaluable patients as of January 2022. The most common TEAEs have been reported for the system organ classes of gastrointestinal disorders (28 patients, 82.3%), metabolism and nutrition disorders (25 patients, 89.3%) and General System Disorders/Fatigue 11 patients (32.4%). PLX038-related TEAEs during Study D15-11073 have been reported for 25 patients (73.5%) from the safety evaluable population to date. Of the 25 patients with PLX038-related TEAEs, 11 patients (32.4%) had related TEAEs that were ≥Grade 3 in severity. The most common PLX038-related TEAEs were diarrhea (16 patients), nausea (14 patients), decreased appetite (13 patients), vomiting (11 patients), fatigue (10 patients), abdominal pain (5 patients), dehydration (4 patients), hypokalemia (4 patients), neutrophil count decreased (4 patients), and colitis (3 patients). Of the 34 patients in the safety evaluable population, 16 patients (41.1%) have reported serious adverse events (SAEs) during the study. The most common SAEs reported in the study are diarrhea
(6 patients, 17.6%), abdominal pain (3 patients, 8.8%), and dehydration (3 patients, 8.8%). To date, there are 8 patients (23.5%) who have experienced serious adverse reactions (SARs) that were at least possibly related to study treatment.. Additionally, Patient 001-029 (enrolled in the 2600 mg/m2dose level), experienced Grade 3 diarrhea, which was considered a dose limiting toxicity (DLT), during Cycle 1, Day 13 that was definitely related to study therapy and resolved within 4 days of onset. Lastly, Patient 001-031 (enrolled in the 2300 mg/m2dose level)
experienced possibly related Grade 2 dehydration and definitely related Grade 3 diarrhea on Cycle 1, Day 9. On Cycle 1, Day 13 the patient experienced possibly related Grade 4 dehydration and unrelated Grade 5 embolism, which had a fatal outcome.  
| Table 2. Serious Adverse Events (N=34 Patients dosed, 16 patients affected *) Patie Dose  nt (mg/m 2) Preferred Term DLT (PT) Toxicit y Grade Serious Drug  Relationsh ip Action  Outcome of Event Taken 001- 172 GI hemorrhage No 2 - Hospitalizati Unrelated None Recovered/Resolved 002 Moderate on 001- 580 Apnea No 5 - Fatal Results in  Unrelated None Fatal 005 Death 001- 580 Cardiac arrest No 5 - Fatal Results in  Unrelated None Fatal 005 Death 001- 580 Sepsis No 4 - Life  Hospitalizati Unlikely None Recovered/Resolved 005 threatening on 001- 580 Upper GI hemorrhage No 5 - Fatal Results in  Unrelated None Fatal 005 Death 001- 387 Biliary tract infection No 4 - Life  Hospitalizati Unrelated None Recovered/Resolved 006 threatening on 001- 580 Mental status changes No 1 - Mild Hospitalizati Unrelated None Recovered/Resolved 007 on 001- 580 Peritonitis bacterial No 3 - Severe Hospitalizati Unrelated None Recovered/Resolved 007 on 001- 3060 Gastric hemorrhage No 3 - Severe Hospitalizati Unrelated None Recovered/Resolved 014 on 001- 3060 Malignant neoplasm  No 5 - Fatal Results in  Unrelated None Fatal 015 progression Death 001- 3060 Abdominal pain No 3 - Severe Hospitalizati Possible Dose  017 on Discontinue d Recovered/Resolved 001- 3060 Colitis No 3 - Severe Hospitalizati Probable None Recovered/Resolved017 on   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|  
| Patie   | Dose        |                  |                    |                              |               |                  |                   |                    |
|---------|-------------|------------------|--------------------|------------------------------|---------------|------------------|-------------------|--------------------|
| nt      | (mg/m 2)    | Preferred Term   | DLT                |                              |               |                  |                   |                    |
| (PT)    | Toxicit y   | Grade            | Serious            | Drug  Relationsh ip          | Action        | Outcome of Event |                   |                    |
| Taken   |             |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Hypoalbuminemia  | No                 | 4 - Life                     | Hospitalizati | Unrelated        | Dose              |                    |
| 017     | threatening | on               | Discontinue d      | Not Recovered/ Not  Resolved |               |                  |                   |                    |
| 001-    | 3060        | Hypokalemia      | No                 | 3 - Severe                   | Hospitalizati | Possible         | Dose              |                    |
| 017     | on          | Discontinue d    | Recovered/Resolved |                              |               |                  |                   |                    |
| 001-    | 3060        | Dehydration      | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 018     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Diarrhea         | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 018     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Sepsis           | No                 | 4 - Life                     | Hospitalizati | Unrelated        | None              | Recovered/Resolved |
| 018     | threatening | on               |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Small intestinal | No                 | 3 - Severe                   | Hospitalizati | Possible         | Dose  Discontinue |                    |
| 018     | obstruction | on               | d                  | Recovered/Resolved           |               |                  |                   |                    |
| 001-    | 3060        | Abdominal pain   | No                 | 3 - Severe                   | Hospitalizati | Probable         | None              | Recovered/Resolved |
| 019     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Dehydration      | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 019     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Diarrhea         | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 019     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Hypotension      | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 019     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 3060        | Small intestinal | No                 | 3 - Severe                   | Hospitalizati | Probable         | None              | Recovered/Resolved |
| 019     | obstruction | on               |                    |                              |               |                  |                   |                    |
| 001-    | 2800        | Colitis          | No                 | 2 -                          | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 021     | Moderate    | on               |                    |                              |               |                  |                   |                    |
| 001-    | 2800        | Diarrhea         | No                 | 2 -                          | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 021     | Moderate    | on               |                    |                              |               |                  |                   |                    |
| 001-    | 2800        | Hypokalemia      | No                 | 3 - Severe                   | Hospitalizati | Definite         | None              | Recovered/Resolved |
| 021     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 2600        | Abdominal pain   | No                 | 3 - Severe                   | Hospitalizati | Unrelated        | None              | Recovered/Resolved |
| 024     | on          |                  |                    |                              |               |                  |                   |                    |
| 001-    | 2600        | Enterocolitis    | No                 | 2 -                          | Hospitalizati | Possible         | Dose              |                    |
| 024     | Moderate    | on               | Discontinue d      | Recovered/Resolved           |               |                  |                   |                    |
| 001-    | 2600        | Lung infection   | No                 | 3 - Severe                   | Hospitalizati | Unrelated        | None              | Recovered/Resolved |
| 026     | on          |                  |                    |                              |               |                  |                   |                    |  
| Patie                                            | Dose      |                |                              |                     |               |                  |      |       |
|--------------------------------------------------|-----------|----------------|------------------------------|---------------------|---------------|------------------|------|-------|
| nt                                               | (mg/m 2)  | Preferred Term | DLT                          |                     |               |                  |      |       |
| (PT)                                             | Toxicit y | Grade          | Serious                      | Drug  Relationsh ip | Action        | Outcome of Event |      |       |
| Taken                                            |           |                |                              |                     |               |                  |      |       |
| 001-                                             | 2600      | Diarrhea       | Yes                          | 3 - Severe          | Hospitalizati | Definite         | Dose |       |
| 029                                              | on        | Discontinue d  | Recovered/Resolved           |                     |               |                  |      |       |
| 001-                                             | 2300      | Diarrhea       | Yes                          | 3 - Severe          | Hospitalizati | Definite         | Dose |       |
| 031                                              | on        | Discontinue d  | Not Recovered/ Not  Resolved |                     |               |                  |      |       |
| 001-                                             | 2300      | Embolism       | Yes                          | 5 - Fatal           | Results in    | Unrelated        | None | Fatal |
| 031                                              | Death     |                |                              |                     |               |                  |      |       |
| * Patients may have experience more than one SAE |           |                |                              |                     |               |                  |      |       |  
Three deaths have been reported to date, all of which were considered to be unrelated to study treatment. Patient 001-005 (enrolled in the 580 mg/m2 cohort) developed a fatal upper GI hemorrhage leading to cardiac arrest and apnea. Patient 001-015 (enrolled in the 3060 mg/m2 cohort) died of malignant neoplasm progression. Patient 001-031 (enrolled in the 2300 mg/m2dose level), experienced Grade 3 diarrhea (definitely related) and Grade 5 embolism (unrelated), which had a fatal outcome To date,5 patients (14.7%) have been removed from the study (dose discontinued) due to a serious adverse event (SAEs):  
| Adverse Event   | DLT              | Grade   | Serious   | Drug            | Therapy  Given   | Action Taken   |                    |
|-----------------|------------------|---------|-----------|-----------------|------------------|----------------|--------------------|
| mg/m2           | Relationship     |         |           |                 |                  |                |                    |
| 3060            | Hypokalemia      | No      | 3         | Hospitalization | Possible         | Yes            | Dose  Discontinued |
| 3060            | Abdominal Pain   | No      | 3         | Hospitalization | Possible         | Yes            | Dose  Discontinued |
| 3060            | Hypoalbuminemia  | No      | 4         | Hospitalization | Possible         | Yes            | Dose  Discontinued |
| 3060            | Small Intestinal | No      | 3         | Hospitalization | Possible         | No             | Dose               |
| Obstruction     | Discontinued     |         |           |                 |                  |                |                    |
| 2600            | Enterocolitis    | No      | 2         | Hospitalization | Possible         | Yes            | Dose  Discontinued |
| 2600            | Diarrhea         | Yes     | 3         | Hospitalization | Definite         | Yes            | Dose  Discontinued |
| 2300            | Diarrhea         | Yes     | 3         | Hospitalization | Definite         | Yes            | Dose  Discontinued |  
Of the 34 dosed patients in the safety evaluable population, 18 patients (52.9%) have reported SAEs during the study. The most common SAEs reported in the study are diarrhea (6 patients, 18.2%), abdominal pain (3 patients, 9.1%), and dehydration (3 patients, 9.1%). A total of 22 (64.7%) of 34 patients enrolled and dosed in the phase I trial experienced diarrhea. Diarrhea was less frequent at the lower doses; 4/10 (40%) patients who received lower doses (1300 mg/m2or lower) had diarrhea compared with 18/24 (75%) patients treated at higher doses (17303060 mg/m2). Severe diarrhea was more frequent at the higher doses; all instances of diarrhea were mild at the lower doses, while 13 patients had moderate-severe diarrhea at the higher doses.  
Five patients developed neutropenia, including two patients with grade 4 events. All patients with neutropenia were treated at 2600 or 3060 mg/m 2 .  
As of this report, the PLX038 dose of 3060 mg/m 2 as a single agent has been identified as the maximal administered dose in the D15-11073 study, with associated dose limiting toxicities
(DLTs) of Grade 4 neutropenia, and Grade 3 nausea, diarrhea, and small intestinal obstruction. Additionally, the intermediate doses of 2800 mg/m 2 and 2600 mg/m 2 were not tolerated as they caused Grade 3 diarrhea in the two patients treated at each dose level. In all, duration of diarrhea of Grades 1 to 3 experienced by 22 patients ranged from 1 to 35 days, lasting an average of 11 dys. The D15-11073 study continues in order to determine the recommended Phase II dose for single agent PLX038 administered on a q3w schedule.  
In addition, because of the low liver exposure of SN-38 from PLX038, the metabolite SN-38G
formed from UGT1A1 is low, with plasma SN-38-G/SN-38 = 0.3 ± 0.1. Hence, UGT1A1 activity is not expected to play a major role in disposition of PLX038; in recognition of the latter, the FDA
has allowed full-dose PLX038 treatment of participants heterozygous in UGT1A1*28. Four patients remained on study without progression of disease for more than 3 months. Of note is participant 4. Beginning 06/16/14 this participant had multiple previous treatments including CPT-11 in 2015/16. He was treated with PLX038 from December 2016 through July 2018 and had a confirmed partial response.  
06/16/14- 07/23/14: FU/Xeloda/Docetaxel->CR
l  
01/27-05/06/15: Herceptin/OxyPlt->SD
06/15-07/06/15: Xeloda->PD
10/13/15-6/29/16: Trastuzumab/FU/Irinotecan->SD
12/15/16- 07/2018: 387 mg/m 2 PLX038 (at 10/02/17-> 38% LN decrease, PR).
Table 4: Patient summaries  
| Months         |                |              |            |            |            |     |        |
|----------------|----------------|--------------|------------|------------|------------|-----|--------|
| Off-           |                |              |            |            |            |     |        |
| Date           | Dose
Cohort                | Dose         | Date of    | Reason off |            |     |        |
| Pt. No.        | UCT Status     |              |            |            |            |     |        |
| Fumor Type     | freatment/Off- | therapy      |            |            |            |     |        |
| Enrolled       | Level          | first dose   | treatment  |            |            |     |        |
| study          | Q3Wk           |              |            |            |            |     |        |
| Rectal         | Homozygous     | 15           |            |            |            |     |        |
| 01-1           | 4/15/2016      | 1            | 4/15/2016  | 11/2016    | 2.5        | PD  |        |
| W              |                |              |            |            |            |     |        |
| adenocarcinoma | mg/m2          |              |            |            |            |     |        |
| GE             | Homozygous     | 172          |            |            |            |     |        |
| 01-2           | 6/30/2016      | 2            | 6/30/2016  | 8/15/2016  | 1.5        | PD  |        |
| adene          | WT             | mg/1         |            |            |            |     |        |
| Rectal         | Homozygous     | 258          |            |            |            |     |        |
| 01-3           | 10/18/2016     | 3            | 10/18/2016 | 1/29/2016  | 1.5        | PD  |        |
| adenocarcinoma | WT             | mg/m2        |            |            |            |     |        |
| Esophageal     | Homozygous     | 387          |            |            |            |     |        |
| 01-4           | 12/14/2016     | 4            | 1/3/2017   | 7/3/2018   | 18         | PD  |        |
| Adenocarcinoma | W              | mg/          | NE due to  |            |            |     |        |
| Adenocarcinor  | early death    |              |            |            |            |     |        |
| Homozygous     | 580            |              |            |            |            |     |        |
| 01-5           | of lower       | 12/7/2017    | s          | 12/7/2017  | 12/15/2017 | 0.5 | due to |
| W              | mg/m2          |              |            |            |            |     |        |
| esophagus      | inderlying     |              |            |            |            |     |        |
| tumor          |                |              |            |            |            |     |        |
| 4/12/2018      | 387            | 4/12/2018    |            |            |            |     |        |
| 01-6           | Gastric cancer | Heterozygous | 4          | 5/24/2018  | 1.5        | PD  |        |
| mg/m2          |                |              |            |            |            |     |        |
| Pancreatic     | Homozygous     | 580          |            |            |            |     |        |
| 01-7           | 4/23/2018      | s            | 5/3/2018   | 6/8/2018   | 1          | PD  |        |
| cancer         | WT             | mg/m         |            |            |            |     |        |
| Pancreation    | 387            |              |            |            |            |     |        |
| 01-8           | Heterozygous   | 4/25/2018    | 4          | 5/9/2018   | 6/21/2018  | 1.5 | PD     |
| cancer         | mg/m2          |              |            |            |            |     |        |  
| Months           |                |              |              |               |            |             |             |       |
|------------------|----------------|--------------|--------------|---------------|------------|-------------|-------------|-------|
| OFF              | o              |              |              |               |            |             |             |       |
| Date             | Dose           | Dase         | Date of      | Reason off    |            |             |             |       |
| Pt. No.          | Tumor Type     | UGT Status   | therapy      |               |            |             |             |       |
| Inrolled         | Cohort         | Level        | first dose   | treatment/Off | treatment  |             |             |       |
| study date       | Q3Wk           |              |              |               |            |             |             |       |
| Homozygous       | 8/14/2018      | 870          | 8/14/2018    | 9/24/2018     |            |             |             |       |
| 01-9             | Colon cancer   | 6            | 1.5          | PD            |            |             |             |       |
| WT               | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | Homozygous     | 1300         |              |               |            |             |             |       |
| 01-10            | 9/27/2018      | 7            | 9/27/2018    | 1/10/2019     | 3.5        | PD          |             |       |
| Adenocarcine     | W              | mg/m2        |              |               |            |             |             |       |
| Homozygous       | 1730           |              |              |               |            |             |             |       |
| Squamous cell of | 11/26/2018     |              |              |               |            |             |             |       |
| 01-11            | 8              | 11/26/2018   | 2/18/2019    | 2.5           | PD         |             |             |       |
| esophagus        | W              | mg/m2        |              |               |            |             |             |       |
| Homozygous       |                |              |              |               |            |             |             |       |
| 01-12            | 0              | SF           |              |               |            |             |             |       |
| *28              |                |              |              |               |            |             |             |       |
| Gastric          | Heterozygous   | 2300         |              |               |            |             |             |       |
| 01-13            | 1/11/2019      | 9            | 1/17/2019    | 2/28/2019     | 1          | PD          |             |       |
| adenocarcinoma   | intermed met   | mg/m2        |              |               |            |             |             |       |
| Esophageal       | 3060           |              |              |               |            |             |             |       |
| 01-14            | Heterozygous   | 3/12/2019    | 10           | 3/14/2019     | 3/25/2019  | 0.5         | Hospice     |       |
| Cancer           | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | 3060           |              |              |               |            |             |             |       |
| 01-15            | Heterozygous   | 4/2/2019     | 10           | 4/15/2019     | 5/16/2019  | 1           | Hospicc     |       |
| Cancer           | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | Heterozygous   | 3060         |              |               |            |             |             |       |
| 01-16            | 5/16/2019      | 10           | 5/16/2019    | 8/26/2019     | 3.5        | PD          |             |       |
| Cancer           | intermed met.  | mg/m2        |              |               |            |             |             |       |
| Esophageal       | 3060           | Intercurrent |              |               |            |             |             |       |
| 01-17            | Heterozygous   | 5/30/2019    | 10           | 6/3/2019      | 7/30/2019  | 2           |             |       |
| Cancer           | mg/m/          | ilness       |              |               |            |             |             |       |
| Gastric          | Heterozygous   | 3060         | Unacceptable |               |            |             |             |       |
| 01-18            | 7/16/2019      | 10           | 1/22/2019    | 8/14/2019     | 1          |             |             |       |
| adenocarcinoma   | intermed met   | mg/m2        | toxicity     |               |            |             |             |       |
| Homozygous       | 3060           |              |              |               |            |             |             |       |
| 01-19            | adenocarcinoma | 8/29/2019    | 10           | 9/5/2019      | 1/7/2019   | 2           | PD          |       |
| WT               | mmmmmmmmmmm    |              |              |               |            |             |             |       |
| Homozygous       | 3060           |              |              |               |            |             |             |       |
| 01-20            | adenocarcinoma | 8/29/2019    | 10           | 9/6/2019      | 10/18/2019 | 1.5         | PI decision |       |
| W                | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | 2800           |              |              |               |            |             |             |       |
| 01-21            | Heterozygous   | 2/27/2020    | 11           | 3/5/2020      | 4/16/2020  | 1.5         | PD          |       |
| adenocarcinoma   | mg/m2          |              |              |               |            |             |             |       |
| Stomach          | 200            |              |              |               |            |             |             |       |
| 01-22            | Heterozygous   | 3/12/2020    | 11           | 3/16/2020     | 4/13/2020  | 1           | PD          |       |
| adenocarcinoma   | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | 2600           |              |              |               |            |             |             |       |
| 01-23            | Heterozygous   | 8/27/2020    | 12           | 8/31/2020     | 1/12/2020  | 2.5         | PD          |       |
| adenocarcinoma   | mg/m2          |              |              |               |            |             |             |       |
| 2600             | Intercurrent   |              |              |               |            |             |             |       |
| 01-24            | Colon cancer   | Heterozygous | 9/1/2020     | 12            | 9/2/2020   | 8/7/2020    | l           |       |
| mg/ml            | illness        |              |              |               |            |             |             |       |
| Esophageal       | 2600           |              |              |               |            |             |             |       |
| 01-25            | Heterozygous   | 10/2/2020    | 12           | 10/5/2020     | 1/20/2021  | 3.5         | PD          |       |
| Cancer           | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | 200            |              |              |               |            |             |             |       |
| 01-26            | 10/29/2020     | 12           | 10/29/2020   | 12/7/2020     |            |             |             |       |
| Heterozygous     | 1.5            | PI decision  |              |               |            |             |             |       |
| adenocarcinoma   | mg/m2          |              |              |               |            |             |             |       |
| Esophageal       | 2600           | Unacceptable |              |               |            |             |             |       |
| 01-27            | 12/16/2020     | 12           | 12/17/2020   | 1/5/2021      | 1          |             |             |       |
| Heterozygous     |                |              |              |               |            |             |             |       |
| Cancer           | mg/m2          | toxicity     |              |               |            |             |             |       |
| Heterozygous     | 200            |              |              |               |            |             |             |       |
| 01-28            | 1/21/2021      | 12           |              |               |            |             |             |       |
| solid tumor      | 0              | SF           |              |               |            |             |             |       |
| *28              | mg/m2          |              |              |               |            |             |             |       |
| 2600             | Unacceptable   |              |              |               |            |             |             |       |
| 01-29            | metastatic     | 2/24/2021    | 12           | 2/25/2021     | 3/12/2021  | 0.5         |             |       |
| Heterozygous     |                |              |              |               |            |             |             |       |
| adenocarcinoma   | mg/m2          | loxicity     |              |               |            |             |             |       |
| 2300             |                |              |              |               |            |             |             |       |
| 01-30            | 4/2/2021       | 9            | 3/10/2021    |               |            |             |             |       |
| solid tumor      | Heterozygous   | 0            | SF           |               |            |             |             |       |
| mg/m2            |                |              |              |               |            |             |             |       |
| 2300             |                |              |              |               |            |             |             |       |
| 01-31            | solid tumor    | Heterozygous | 4/2/2021     | 9             | 4/7/2021   | 4/19/2021   | 0.5         | Death |
| mg/m2            |                |              |              |               |            |             |             |       |
| Homozygous       | 2300           |              |              |               |            |             |             |       |
| 01-32            | solid tumor    | 7/16/2021    | 9            | 7/29/2021     | o          | WOC/SF      |             |       |
| W                | mg/m2          |              |              |               |            |             |             |       |
| Heterozygous     | 2300           |              |              |               |            |             |             |       |
| 8/20/2021        | 8/26/2021      |              |              |               |            |             |             |       |
| 01-33            | gastric        | 9            | 9/8/2021     | 0.5           | WOC        |             |             |       |
| *28              | mg/m2          |              |              |               |            |             |             |       |
| 10/14/2021       | 2000           |              |              |               |            |             |             |       |
| 01-34            | solid tumor    | 13           | 10/21/2021   | 1/11/2021     | 0.5        | PI decision |             |       |
| mg/m2            |                |              |              |               |            |             |             |       |
| Homozygous       | 2000           |              |              |               |            |             |             |       |
| 01-35            | solid tumor    | 11/3/2021    | 13           | 1/11/2021     | 12/27/2021 | 1.5         | PD          |       |
| W                | mg/m2          |              |              |               |            |             |             |       |
| Heterozygous     | 2000           |              |              |               |            |             |             |       |
| 01-36            | 11/17/2021     | 11/18/2021   |              |               |            |             |             |       |
| solid tumor      | 13             | C3D15        | on-study     |               |            |             |             |       |
| mg/m2            |                |              |              |               |            |             |             |       |
| 01-37            | 1730           | 2/3/2022     |              |               |            |             |             |       |
| solid tumor      | Heterozygous   | 2/3/2022     | 8            | C1D2          | on-study   |             |             |       |
| m/m2             |                |              |              |               |            |             |             |       |
| 1730             |                |              |              |               |            |             |             |       |
| 01-38            | Solid tumor    | 2/9/2022     | 8            | 2/10/2022     | on-study   |             |             |       |
| mg/m2            |                |              |              |               |            |             |             |       |  
| Table 5. Possibly related adverse events       |                  |                              |      |
|------------------------------------------------|------------------|------------------------------|------|
| # of                                           | # of             |                              |      |
| # of Participants with AEs, Highest CTCAE      |                  |                              |      |
| Possibly Related Adverse                       | Participants     | Participants                 |      |
| Events                                         | Affected         | Grade                        | with |
| N=16*                                          | Serious AEs      |                              |      |
| Anorexia                                       | 12               | Gr 1 (7), Gr 2 (4), Gr 3 (1) | 0    |
| Nausea                                         | 11               | Gr 1 (6), Gr 2 (4), Gr 3 (1) | 0    |
| Vomiting                                       | 8                | Gr 1 (6), Gr 2 (2)           | 0    |
| Fatigue                                        | 8                | Gr 1 (3), Gr 2 (2), Gr 3 (3) | 0    |
| Abdominal Pain                                 | 4                | Gr 1 (1), Gr 2 (2), Gr 3 (1) | 0    |
| Hypokalemia                                    | Gl (2), Gr 3 (1) |                              |      |
| 3                                              | 0                |                              |      |
| Neutropenia                                    | 1                | Gr 2 (1)                     | 0    |
| Anemia                                         | l                | Gr 1 (1)                     | 0    |
| Hypocalcemia                                   | 1                | Gr 2 (1)                     | 0    |
| Hyponatremia                                   | 1                | Gr 1 (1)                     | 0    |
| Mucositis                                      | Gr 1 (1)         | 0                            |      |
| l                                              |                  |                              |      |
| Constipation                                   | Gr 1 (1)         |                              |      |
| 1                                              | 0                |                              |      |
| Ocular Pruritus                                | 1                | Gr 1 (1)                     | 0    |
| Loss of Appetite                               | l                | Gr 1 (1)                     | 0    |
| Nasal Congestion                               | 1                | Gr 1 (1)                     | 0    |
| Rash                                           | 1                | Gr 1 (1)                     | 0    |
| Small intestinal obstruction                   | l                | Gr 3 (1)                     | l    |
| Weight loss                                    | Gr 2 (1)         | 0                            |      |
| 1                                              |                  |                              |      |
| * Patients may have experience more than 1 SAE |                  |                              |      |  
Table 6 shows pharmacokinetic (PK) parameters of various administered doses of Q3Wk PLX038 vs 350 mg/m² QWk CPT-11 and two other SN-38 prodrugs, Sacituzumab govitecan and Enz2208.  
Of note are the following:
.  
Most of the weight of PLX038 is due to the large 40 kDa PEG component; SN-38 content is only 3.5% of the total weight, and considering renal elimination of PLX038, the actual SN-38 present in vivo is only ~1% of the total weight.
.  
The MTD of pegamotecan, a related PEG-camptothecins analog was 7 g/m 2 [ 31 ] some 3fold higher than the current dose of PLX038. We thus assume we could dose-escalate 3fold higher than the current dose without PEG-related toxicity, if necessary, to reach MTD.
.  
At the current dose of 2.3 g/m 2 , the free SN-38 is equivalent to the SN-38 formed from the MTD of Q3Wk CPT-11; but, Cmax is ~50% lower, t 1/2 is 10-fold longer, and AUC is over 5-fold higher. The PK benefits of PLX038 vs CPT-11 appear favorable.  
| Table 6. Human PK parameters of SN-38 from PLX038 vs other SN-38 prodrugs A Total SN-38 B Free SN-38  delivered C SN-38 t1/2 SN-38 Cmax SN-38 C14d D SN-38 AUC E mg/m2 /cycle mg/m2 /cycle h (n ) nM (n) nM nM•h (n) PLX038 Q3W 14 4 97 ± 11.4 (4) 22 ± 6.2 (6) 1 1,660 ± 560 (4) 21 6 91 ± 3.7 (2) 14± 4.7 (3) 2 1,756 ± 1071 (2) 31 9 90 (1) 24± 13 (2) 3 2,513 (1) 46 13 85 hr 30 2 4,000 62 17 ~100 hr 46 3 6,126 82 23 ~100 hr 68 8 11,356 107 32 118 ± 31 h 186 ± 88 11.7 ± 1.3 17,820 ± 2550 CPT-11 Q3Wk F 227 23 ~12 hr 143 2,000 Sacituzumab govitecan ADC (QWk x 2, 3 wk. cycle) [32, 33] 15 14 ~20 hr 230 0.1 7,600 EZN-2208 (Q3W) 10 10 30 h 370 ~0 4,600 A PK data of 2,300 mg/m2 not yet available; estimates were simulated from lower doses assuming   |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|  
A PK data of 2,300 mg/m2not yet available; estimates were simulated from lower doses assuming  
t1/2 = 100 h for PLX038 and dose linearity of Cmax.  
B SN-38 ~3.5% by weight of PLX038. C Delivered free SN-38 is ~ ~30% of total SN-38. D C14d are estimated from given parameters (below LLOQ). E AUC0-∞ values are calculated from the models. F From label.  
1.2.3 Rucaparib Rucaparib is being developed as an antineoplastic agent. Nonclinical evaluation has demonstrated exquisite sensitivity of BRCA1 and BRCA2 homozygous mutant cell lines to rucaparib, which is attributed to PARP inhibition alone, and provides a rationale for the clinical assessment of rucaparib as monotherapy in participants with hereditary (HRD) (germline) and acquired (somatic) deficiencies of BRCA1 and BRCA2. Clinical data indicate that benefit from treatment with a PARP inhibitor includes participants with a germline BRCA or somatic BRCA mutation and may extend to participants with other HRD alterations. This supports the investigation of PARP inhibitors such as rucaparib in a broader group of tumors with HRD (inclusive of BRCA and BRCA-like, as well other than BRCA mutations involved in HRD). The first marketing authorization was granted in the United States (US) on 19 December 2016, for the treatment of patients with deleterious BRCA mutation (germline and/or -somatic) associated advanced ovarian cancer, who have been treated with 2 or more chemotherapies. Clovis voluntarily withdrew this indication in the US, Europe and GB in 2022 based on the detriment in overall survival (OS) observed for patients randomized to rucaparib versus chemotherapy. Rucaparib is currently approved in the US for:  
- The maintenance treatment of adult patients with recurrent epithelial ovarian (EOC),
fallopian tube cancer (FTC), or primary peritoneal cancer (PPC) who are in response (complete or partial) to platinum-based chemotherapy.  
- The treatment of adult patients with a deleterious BRCA mutation (germline and/or somatic)-associated metastatic castration-resistant prostate cancer (mCRPC) who have been treated with androgen-receptor-directed therapy and a taxane-based chemotherapy.
The withdrawal of the treatment indication for BRCA-mutant ovarian cancer patients did not affect the other approved rucaparib indications. For complete safety and efficacy information, refer to investigator brochure. 1.2.3.1 Overview of Clinical Findings Phase 1, 2, and 3 clinical studies have or are being conducted to evaluate oral rucaparib in cancer participants. These studies have evaluated the PK (including the effect of food), metabolism, safety, and efficacy of rucaparib following oral administration at doses ranging from 40 mg QD to 840 mg BID in participants with solid tumors. Results from a Phase 1 dose-escalation study determined 600 mg BID as the RP2D, while an MTD was not identified. Phase 2 and Phase 3 clinical studies with oral rucaparib have been or are being conducted with the 600 mg BID dose and in participants with cancer associated with HRD.
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1.2.3.2 clinical pharmacology

Assessment of rucaparib PK in cancer participants showed an approximate dose-proportional exposure after QD or BID dosing, rapid absorption with Cmax achieved within 1.5 to 6 hours. The oral bioavailability was 36%. Rucaparib was moderately bound to human plasma proteins in vitro. At a dose of 600 mg BID rucaparib, steady state was achieved after approximately 1 week. At the target clinical dose of 600 mg, a high-fat meal increased the Cmax and AUC0-24 of rucaparib by 20% and 38%, respectively, and delayed the median Tmax by approximately 2.5 hours as compared with that under fasted conditions. The effect of food on rucaparib PK is not considered to be clinically significant, thus rucaparib can be taken with or without food. Drug interactions with rucaparib as a substrate were assessed in a population PK analysis. CYP2D6 phenotypes (poor metabolizers, intermediate metabolizers, normal metabolizers, and ultra-rapid metabolizers) and CYP1A2 phenotypes (normal metabolizers and hyper inducers) did not significantly impact the steady-state exposure of rucaparib at 600 mg BID. Current smokers had overlapping rucaparib exposures as compared to nonsmokers and former smokers. Collectively, the results suggest that CYP1A2 and CYP2D6 play limited role in rucaparib metabolism in vivo, and no rucaparib dose adjustment is needed when concomitantly administered with CYP inhibitors. Concomitant treatment with proton pump inhibitors (PPIs) showed no clinically significant effect on rucaparib PK. No dose modification of rucaparib is required for participants who are receiving concomitant treatment with a PPI. Results from Study CO-338-044 indicated that rucaparib, at 600 mg BID, moderately inhibited CYP1A2, weakly inhibited CYP2C9, CYP2C19, and CYP3A, and showed no clinically significant effect on P-glycoprotein (P-gp). Caution should be exercised in the concomitant use of drugs that are substrates of the above CYP enzymes with narrow therapeutic windows. Results from the mass balance and metabolite profiling study CO-338-045 showed rucaparib excretion primarily in feces, followed by urine. M324 derived from oxidation of rucaparib was the major metabolite identified. Other metabolic pathways included N-demethylation, N-methylation, and glucuronidation. Plasma rucaparib showed a T1/2 of 24 hours.  
Preliminary PK data from prostate cancer participants (Study CO-338-052, TRITON2) are comparable with the data from ovarian cancer participants (Study CO-338-014, ARIEL3) suggesting a lack of PK difference between male and female participants.
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1.2.3.3 efficacy

The US approval of rucaparib for the treatment of women with relapsed BRCA-mutated (inclusive of germline and somatic BRCA mutations) ovarian cancer was based on pooled data for 106 participants enrolled in either Part 2A of Study CO-338-010 (n = 42) or Part 1 or Part 2 of Study CO-338-017 (ARIEL2) (n = 64) who met the following criteria: received at least 1 dose of rucaparib 600 mg; received at least 2 prior chemotherapy regimens, including at least 2 platinumbased regimens, and had a deleterious BRCA1/2 mutation (germline BRCA1/2 mutation in Study CO-338-010; germline or somatic BRCA1/2 mutation in Study CO-338-017 [ARIEL2]). In the integrated efficacy population, the investigator-assessed confirmed ORR per RECIST v1.1 was 53.8% (95% CI, 43.8-63.5), and the median duration of response was 9.2 months (range, 1.7-9.8; 95% CI, 6.6-11.6). For the secondary endpoint of investigator-assessed confirmed response per combined RECIST and GCIG CA-125 criteria, the ORR was 70.8% (95% CI, 61.1%-79.2%).  
Participants who were sensitive to their most recently administered platinum regimen had a higher ORR (65.8%; 95% CI, 54.3%-76.1%) than those who were resistant (ORR = 25.0%; 95% CI, 8.7%-49.1%) or refractory (ORR = 0%; 95% CI, 0.0-41.0%) to their most recent platinum regimen. The PFS rate at 6 and 12 months was 79.0% and 41.0%, respectively. Rucaparib efficacy in the maintenance setting was demonstrated in 564 participants randomized in Study CO-338-014 (ARIEL3). Rucaparib maintenance treatment significantly improved PFS compared with placebo in all primary analysis groups of participants with recurrent ovarian carcinoma after a complete or partial response to platinum-based therapy. The median PFS in the BRCA population was 16.6 months (95% CI, 13.4-22.9) for the rucaparib-treated participants and 5.4 months (95% CI, 3.4-6.7) for the placebo group. The median PFS in the HRD population was 13.6 months (95% CI, 10.9-16.2) for rucaparib-treated participants and 5.4 months (95% CI, 5.15.6) for the placebo group. The median PFS in the intention to treat (ITT) population was 10.8 months (95% CI, 8.3-11.4) for the rucaparib group and 5.4 months (95% CI, 5.3-5.5) for the placebo group. Overall, rucaparib as maintenance treatment reduced the risk of progression by
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abbreviated title plx038 and rucaparib

63.5% (HR 0.365 [95% CI, 0.295-0.451]; p < 0.0001) in the ITT population, demonstrating a strong treatment effect over placebo. Analysis of non-nested, non-overlapping participant subpopulations indicate that the significant improvement in PFS observed in the ITT population was not driven only by the HRD or BRCA subpopulations. Nearly half (44.6%) of the participants in the rucaparib group showed benefit at 1 year compared to 8.8% in the placebo group. At 18 and 24 months, 32.0% and 26.0%, respectively, of participants who received rucaparib were still progression-free compared to 5.8% and 2.6% in the placebo group.
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1.2.3.4 safety integrated safety analysis

Pooled safety data in the treatment setting are provided as of the 31 December 2017 visit cut-off for ovarian cancer participants in the ongoing Studies CO-338-010 (All Parts) and CO-338-017
(ARIEL2; both Parts 1 and 2), in which 565 participants with relapsed ovarian cancer received 600 mg BID rucaparib. Safety data in the maintenance setting are provided as of the 31 December 2017 visit cut-off for Study CO-338-014 (ARIEL3), in which a total of 561 participants have been treated (372 participants in the rucaparib group and 189 participants in the placebo group). Pooled safety data from the treatment setting as well as safety data in the maintenance setting are presented in Table 7.  
| Treatment Setting                                                                                                                                                   | Maintenance Setting         |            |            |            |           |         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------|------------|------------|------------|-----------|---------|
| Pooled Studies CO-338-010                                                                                                                                           | Study CO-338-014 (ARIEL3) b |            |            |            |           |         |
| and CO-338-017 (ARIEL2)*                                                                                                                                            |                             |            |            |            |           |         |
| 600 mg BID Rucaparib                                                                                                                                                | 600 mg BID Rucaparib        | Placebo    |            |            |           |         |
| Preferred Term                                                                                                                                                      | (N = 565)                   | (N = 372)  | (N = 189)  |            |           |         |
| n (%)                                                                                                                                                               | n (%)                       | n (%)      |            |            |           |         |
| All Grades                                                                                                                                                          | > Grade 3                   | All Grades | > Grade 3  | All Grades | > Grade 3 |         |
| Nausea                                                                                                                                                              | 439 (77.7)                  | 29 (5.1)   | 282 (75.8) | 14 (3.8)   | 69 (36.5) | 1 (0.5) |
| Asthenia/fatigue'                                                                                                                                                   | 422 (74.7)                  | 64 (11.3)  | 263 (70.7) | 26 (7.0)   | 84 (44.4) | 5 (2.6) |
| Vomiting                                                                                                                                                            | 259 (45.8)                  | 25 (4.4)   | 138 (37.1) | 15 (4.0)   | 29 (15.3) | 2 (1.1) |
| Anaemia/decreased hemoglobin®                                                                                                                                       | 250 (44.2)                  | 137 (24.2) | 145 (39.0) | 80 (21.5)  | 10 (5.3)  | 1 (0.5) |
| ALT/AST increased?                                                                                                                                                  | 23 (39.5)                   | 61 (10.8)  | 129 (34.7) | 38 (10.2)  | 8 (4.2)   | 0       |
| Decreased appetite                                                                                                                                                  | 219 (38.8)                  | 16 (2.8)   | 88 (23.7)  | 3 (0.8)    | 26 (13.8) | 0       |
| Constipation                                                                                                                                                        | 215 (38.1)                  | 8 (1.4)    | 141 (37.9) | 7 (1.9)    | 46 (24.3) | 2(1.1)  |
| Dysgeusia                                                                                                                                                           | 204 (36.1)                  | 1 (0.2)    | 148 (39.8) | 13 (6.9)   |           |         |
| 0                                                                                                                                                                   | 0                           |            |            |            |           |         |
| Abdominal pain                                                                                                                                                      | 186 (32.9)                  | 23 (4.1)   | 12 (30.1)  | 1 (3.0)    | 49 (25.9) | 1 (0.5) |
| 184 (32.6)                                                                                                                                                          | 121 (32.5)                  |            |            |            |           |         |
| Diarrhoea                                                                                                                                                           | 13 (2.3)                    | 2 (0.5)    | 41 (21.7)  | 2 (1.1)    |           |         |
| Thrombocytopenia/decreased platelets'                                                                                                                               | 136 (24.1)                  | 36 (6.4)   | 109 (29.3) | 20 (5.4)   | 5 (2.6)   | 0       |
| Dyspnoea                                                                                                                                                            | 127 (22.5)                  | 5 (0.9)    | 53 (14.2)  | 0          | 14 (7.4)  | 0       |
| 125 (22.1)                                                                                                                                                          | 61 (16.4)                   |            |            |            |           |         |
| Blood creatinine increased                                                                                                                                          | 3 (0.5)                     | 1 (0.3)    | 3 (1.6)    | 0          |           |         |
| Abbreviations: ALT = alanine aminotransferase; AST = aspartate aminotransferase; MedDRA = Medical Dictionary for Regulatory Activities; TEAE = treatment-           |                             |            |            |            |           |         |
| emergent adverse event.                                                                                                                                             |                             |            |            |            |           |         |
| 2 The treatment setting pooled data presented are from the 31 December 2017. cut-off date for ovarian cancer patients in the ongoing Studies CO-338-010 (All Parts) |                             |            |            |            |           |         |
| and CO-338-017 (ARIEL2; both Parts 1 and 2).                                                                                                                        |                             |            |            |            |           |         |  
Table 7: Incidence of TEAEs (All Causality; All Grades, Grade ≥ 3) Reported in ≥ 20% of Participants - Safety Population
- Combined MedDRA preferred terms In participants with ovarian cancer who received 600 mg BID rucaparib in pooled Studies CO338-010 and CO-338-017 (treatment setting), as well as in Study CO-338-014 (maintenance setting), the most common TEAEs reported were primarily mild to moderate (Grade 1-2) in severity and include gastrointestinal disorders (nausea, vomiting, diarrhea, constipation, and abdominal pain), asthenia/fatigue, decreased appetite, and dysgeusia. The most common TEAE ≥ Grade 3 include anemia/decreased hemoglobin, ALT/AST increased, neutropenia/decreased ANC, and asthenia/fatigue. Effects on cardiac channel activity in vitro and a comprehensive assessment of the effects of rucaparib on ECG parameters in cancer participants demonstrated a low risk of cardiac effects by rucaparib. The laboratory abnormalities reported in Study CO-338-014 (ARIEL3) were consistent with the TEAEs, with decreased hemoglobin, increased ALT, increased AST, and increased serum creatinine, most common in participants in the rucaparib group. Decreased platelets, neutrophils, leukocytes, lymphocytes, increased alkaline phosphatase and increased cholesterol were observed to a lesser extent. ALT/AST elevations occurred early in treatment (i.e., by Day 1 of Cycle 2) and then resolved or stabilized over time. Treatment with rucaparib was continued at either the initial 600 mg BID dose or a lower dose. Elevations in ALT/AST were generally not accompanied by a concomitant elevation in bilirubin. Continued dosing with rucaparib in the presence of Grade 3 ALT/AST elevations is permitted if there are no other signs of liver toxicity. Creatinine elevations were also observed early in treatment (i.e., by Day 1 of Cycle 2) and then stabilized with continued rucaparib treatment.
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preliminary safety analysis for prostate

Safety data are provided as of the 06 March 2018 visit cut-off for prostate cancer participants in the ongoing Study CO-338-052 (TRITON2), in which 52 participants with mCRPC received 600 mg BID rucaparib. The safety profile of rucaparib in the mCRPC participant population is consistent with the safety profile in ovarian cancer participants. The most common TEAEs reported were primarily mild to moderate (Grade 1-2) in severity and include gastrointestinal toxicities (nausea, constipation, vomiting, diarrhea), asthenia/fatigue, decreased appetite, anemia/decreased hemoglobin, ALT/AST increased, and dizziness. The most common TEAEs ≥
Grade 3 include anemia/decreased hemoglobin, ALT/AST increased, thrombocytopenia/decreased platelets, nausea, and hypophosphatemia. 1.2.3.5 Efficacy and safety update
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studies co-338-017 (ariel2) & co-338-014

The ARIEL program is evaluated rucaparib in patients with relapsed ovarian cancer. Study CO338-017 (ARIEL2) was a 2-part, single-arm, open-label, Phase 2 study of rucaparib as treatment for relapsed high-grade ovarian cancer. The primary purpose of the study was to determine a molecular signature of HRD associated with a response to rucaparib in patients with relapsed disease. Efficacy data from Part 1 (n = 204 patients) indicated that rucaparib led to clinically meaningful and durable responses in patients whose tumor contained a BRCA1/2 mutation or HRD (BRCA-like molecular signature), demonstrating that benefit from PARP inhibitor treatment extended beyond patients with a BRCA mutation. In Study CO-338-017, Part 2 (n = 287 patients), efficacy data in more heavily pretreated patients, predominantly with platinum-resistant/refractory disease, as compared to patients in Part 1, indicated the greatest activity in patients with a tBRCA mutation. However, there was greater activity in patients in Part 1 who had earlier-line platinum-sensitive disease as compared to the patients in Part 2 who were more heavily pretreated. The optimized molecular HRD signature from Study CO-338-017 was prospectively applied to the primary analysis of Study CO-338-014 (ARIEL3), an ongoing, randomized, double-blind, Phase 3 study of rucaparib versus placebo as switch maintenance treatment in patients with platinum-sensitive, relapsed, high-grade ovarian cancer (N = 564 enrolled patients).
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study co-338-043 (ariel4)

Efficacy data indicated a highly statistically significant difference in invPFS between rucaparib and placebo for each of the 3 primary efficacy analysis populations (tBRCA, HRD, and ITT). The TEAEs reported with rucaparib treatment are consistent with those previously reported in openlabel, non-randomized studies of rucaparib. The Phase 3 Study CO-338-043 (ARIEL4) evaluated rucaparib versus chemotherapy as treatment for patients with relapsed high-grade ovarian cancer associated with a deleterious BRCA1/2 mutation (N = 349 enrolled patients) and served as a confirmatory study for third-line+ treatment of BRCA-mutant ovarian cancer patients. Study CO338-043 met the primary endpoint of invPFS, demonstrating a benefit for rucaparib treatment compared with active, standard-of-care chemotherapy. The safety profile was consistent with the safety profile in currently approved maintenance and treatment indications, and the tolerability of rucaparib was comparable with standard-of-care chemotherapy. Final data analyses for Study CO-338-043 showed detrimental effect in terms of overall survival (OS) for patients randomized to rucaparib versus chemotherapy. The OS results were heavily confounded by a high rate of cross-over to rucaparib for patients initially randomized to the chemotherapy arm (close to 90% of all patients in ARIEL4 received rucaparib after randomization or crossover), as well as the post-progression subsequent treatments and was largely driven by patients with platinum-resistant disease.
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study co-338-087 (athena)

Study CO-338-087 (ATHENA) is an ongoing, randomized, double-blind, placebo-controlled Phase 3 study evaluating rucaparib as monotherapy (ATHENA-MONO) and in combination with nivolumab (vs. nivolumab; ATHENA-COMBO) as maintenance treatment following response to first-line platinum-based chemotherapy in patients with newly diagnosed ovarian cancer who have also undergone cytoreductive surgery.
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triton program

The TRITON program is evaluating rucaparib efficacy in a Phase 2 (CO-338-052 [TRITON2]) and a Phase 3 (CO-338-063 [TRITON3]) study of mCRPC. Study CO-338-052 (Phase 2) is evaluated rucaparib monotherapy for the treatment of mCRPC associated with evidence of HRD, with an emphasis on defects in BRCA1/2 and ATM genes, and an exploratory evaluation of other HRR gene mutations, in patients who have received prior AR-directed therapy and a taxane. Results from the final safety analysis of patients with mCRPC (n = 277) in Study CO-338-052 are consistent with those reported for ovarian cancer patients. Rucaparib PK exposure in prostate cancer patients is comparable to that in ovarian cancer patients (Study CO-338-014), suggesting no sex-related PK difference of rucaparib. Study CO-338-063 (Phase 3) is a randomized study evaluating rucaparib monotherapy versus physician's choice (abiraterone acetate, enzalutamide, or docetaxel) for the treatment of mCRPC patients with a BRCA1/2 or ATM mutation who have received prior treatment with AR-directed therapy but have not yet received taxane-based chemotherapy in the castration-resistant setting. Additionally, a Phase 1b Study CO-338-107 (RAMP) is ongoing to evaluate the PK, safety, tolerability, and preliminary efficacy of rucaparib in combination with other anticancer therapies in patients with mCRPC. Frequently reported TEAEs in the ovarian and prostate cancer populations included GI toxicities (eg, nausea and vomiting), myelosuppression, asthenia/fatigue, and elevated ALT/AST. These toxicities were successfully managed by treatment interruption or dose reduction and/or supportive care.
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study co-338-010

Study CO-338-010 evaluated rucaparib in patients with any solid tumor that progressed on standard treatment (Part 1; Phase 1), patients with relapsed ovarian cancer associated with a BRCA mutation (Parts 2A and 2B; Phase 2), and patients with relapsed solid tumor and a BRCA mutation (Part 3; Phase 2). In Part 1, 56 patients with advanced solid tumors received oral rucaparib at dose levels of 40 mg to 500 mg QD and 240 mg to 840 mg BID. The PK of rucaparib was approximately dose-proportional in the tested dose range. In Parts 2A and 2B, clinically meaningful and durable responses to rucaparib were observed in patients with a gBRCA1/2 mutation. In Part 3 (Phase 2), the PK of a 300 mg dose strength tablet and a total dose of 600 mg rucaparib were characterized in patients with a solid tumor with a known deleterious BRCA1/2 mutation. The effect of food on rucaparib PK was also evaluated. At the target clinical dose of 600 mg, a high-fat meal increased the Cmax and AUC0-24 by approximately 20% and 38%, respectively, and delayed the median Tmax by approximately 2.5 hours. The effect of food on rucaparib exposure was not deemed clinically significant; rucaparib may be taken with or without food.
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study co-338-081

Study CO-338-081 (RUCA-J) is an ongoing study. The Phase 1 study evaluated the safety and PK of rucaparib in patients with a previously treated solid tumor, to establish the RD in Japanese patients. The safety, tolerability, and PK of the RD in this study is being evaluated in Japanese patients who had progressed on standard treatment and had recurrent HGSOC (no gene mutation required), BRCA1/2-mutated breast cancer, or other solid tumor with evidence of a BRCA1/2 or other HRR gene mutation. At 600 mg BID, steady-state Cmax and AUC of rucaparib were slightly higher than that in Western patients, but the difference was not considered clinically significant, thus no adjustment in the starting dose is considered necessary.
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phase 1 clinical pharmacology studies

Phase 1 clinical pharmacology studies were conducted in patients with advanced solid tumors. Results from the completed DDI portion (Part 1) of Study CO-338-044 indicated that rucaparib, at 600 mg BID, moderately inhibited CYP1A2, weakly inhibited CYP2C9, CYP2C19, and CYP3A, and marginally inhibited P-gp. In Part I of Study CO-338-095 (a DDI study), rucaparib 600 mg BID caused 29% increase in Cmax and 35% increase in AUCinf of oral rosuvastatin (a BCRP substrate), and 43% and 56% increases in AUClast of the oral contraceptives ethinylestradiol and levonorgestrel, respectively. In Study CO-338-107, concomitant dosing of rucaparib with a strong CYP3A4 inducer enzalutamide showed no change in trough PK of either rucaparib or its metabolite M324 (formation is mediated by CYP3A4), indicating that CYP3A4 has no significant effect on rucaparib PK. Results from the completed mass balance and metabolite profiling portion (Part 1) of Study CO-338-045 following a single oral dose of [14C]-rucaparib showed that rucaparib was predominantly excreted in feces (71.9% of recovered 14C
radioactivity), followed by urine (17.4% of recovered 14C radioactivity). Oxidation, Ndemethylation, N-methylation, and glucuronidation were the major metabolic pathways for rucaparib, with M324, derived from oxidation of rucaparib, identified as the most abundant metabolite. In Study CO-338-078 (Part I), patients with moderate hepatic impairment showed similar Cmax but 44.6% higher AUCinf after a single oral dose of 600 mg rucaparib as compared to patients with normal hepatic function.
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1.2.4 rationale for this study

Top1 inhibitors are a class of chemotherapeutic agents that inhibit DNA replication and induce DNA strand breaks that require PARP for their repair. As such, PARP inhibition is highly synergistic in combination with Top1 Inhibitors [29]. In BRCA-wt participants, where PARP inhibitor monotherapy treatment does not demonstrate synthetic lethality, the ability to improve tumor response may be achieved with combination therapy. It is hypothesized that combining PARP inhibitors with Top1 inhibitors will result in increased efficacy in the clinic compared to either agent alone.  
While the combination of PARP inhibitor and Top1 inhibitor is expected to be synergistic, doselimiting toxicities have prevented this combination from being dosed at high doses of each drug, thereby limiting its potential clinical utility. The advantage of dosing with PLX038 compared to conventional Top1 inhibitor is the extended PK profile and prolonged local tumor exposure of SN38. Since SN-38 is cleared more quickly from normal tissues than from tumor, it is hypothesized that delayed dosing of rucaparib (i.e. starting rucaparib dosing a few days after PLX038 administration) will allow for the expected window of maximum SN-38-induced toxicity to pass in the absence of concurrent rucaparib toxicity. However, the tumor levels of SN-38 are predicted to be sustained upon subsequent rucaparib dosing, therefore maintaining the ability of both drugs to act on tumor tissue simultaneously. The primary hypothesis for the proposed study is that a tolerable combination of PLX038 plus rucaparib can be identified using a dose-escalation strategy that incorporates dose scheduling (i.e. intermittent dosing of rucaparib as opposed to continuous dosing). The secondary hypothesis is that the combination of PLX038 plus rucaparib is more efficacious than either agent alone. The hypothesis that biomarkers will predict participant response to treatment will be investigated in an exploratory manner in two ways: markers of drug sensitivity and resistance will be measured pre-treatment, and pharmacodynamic markers will be measured post-treatment. The starting dose of rucaparib (400 mg BID) is ~66% of its full dose (600 mg BID) and the starting dose of PLX038 (1,300 mg) is about 40% of its MTD (3,060 mg), a sufficiently low enough dose to ensure the safety as well as potential for enhanced efficacy. As discussed in the preclinical efficacy section of protocol **1.2.2.1** when used in combination with sub-therapeutic QD dose PARP
inhibitor, talazoparib, a single low sub-therapeutic dose of PLX038A (10% of single dose) caused tumor shrinkage in TNBC xenograft models. Administering the PARP inhibitor with a 48 hour window after PLX038 will also likely minimize overlapping AEs of myelosuppression.
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eligibility assessment and enrollment

2.1 Eligibility Criteria 2.1.1 Inclusion Criteria
- Subjects with:
➢ histologically confirmed solid tumors (Phase I)
OR
➢ histologically or cytologically confirmed SCLC (Phase II)
OR
➢ histologically or cytologically confirmed extra-pulmonary small cell carcinomas
(Phase II)
- Age ≥18 years. Because no dosing or adverse event data are currently available on the use of PLX038 in combination with rucaparib in participants <18 years of age, children are excluded from this study, but will be eligible for future pediatric trials.  
- Subjects must have progressed on or after standard first-line systemic chemotherapy and have no effective treatment options.  
- Participants must have disease that is not amenable to potentially curative resection. - Participants must have measurable disease per RECIST 1.1. See Section 6.3 for the evaluation of measurable disease.  
- Participants with asymptomatic brain metastases and treated brain metastases are eligible.  
- ECOG performance status ≤ 2 (**Appendix A**).  
- Adequate hematological function defined by:  
➢ white blood cell (WBC) count ≥ 3 × 109/L, ➢ absolute neutrophil count (ANC) ≥ 1.5 ×109/L, ➢ platelet count ≥100 × 109/L,
➢ Hgb ≥9 g/ dL
- Adequate hepatic function defined by:  
➢ a total bilirubin level ≤ 1.5 × ULN, ➢ an AST level≤2.5×ULN, (≤ 5X ULN if liver metastasis) ➢ an ALT level ≤2.5 ×ULN, (≤ 5X ULN if liver metastasis).
- Adequate renal function defined by:  
| < 1.5x institution upper limit of normal OR > 45 mL/min/1.73 m2 for participant with creatinine levels > 1.5 X institutional ULN                                                                       |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Creatinine OR Measured or calculated  creatinine clearance  (CrCl) (eGFR may also  be used in place of  CrCl) A A Creatinine clearance (CrCl) or eGFR should be calculated per institutional standard. |  
- The effects of the study treatment on the developing human fetus are unknown; thus, women of childbearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study treatment and up to 6 months after the last dose of the study drug (s). Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately.  
- Subjects must be able to understand and willing to sign a written informed consent document.  
2.1.2 Exclusion Criteria
- Participants who are receiving any other investigational agents.  
- Systemic anti-cancer treatment or major surgery within 2 weeks prior to enrollment.  
- Radiotherapy within 24 hours prior to enrollment. - Participants who require treatment with strong inhibitors or inducers of CYP3A or with UGT1A1 inhibitors during the planned period of investigational treatment with PLX038.  
- Participants with known Gilbert's syndrome.  
- Participants homozygous for the UGT1A1*28 variant allele with severely reduced UGT1A1 activity.  
- Participants with known HIV, HCV, HBV status on antiviral drugs are excluded due to the absence of previous experience with concurrent use of antiviral medications and the investigational drug product to be evaluated in the current study and possible for adverse pharmacokinetic and/or pharmacodynamic interactions.  
- History of allergic reactions attributed to compounds of similar chemical or biologic composition to PLX038 or rucaparib.  
- Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that may impair the participant's tolerance of study treatments.  
- Pregnant women are excluded from this study because PEGSN38 and rucaparib potential for teratogenic or abortifacient effects are unknown. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with PEGSN38 and rucaparib, breastfeeding should be discontinued if the mother is treated with study drugs.  
2.1.3 Recruitment Strategies
This study will be posted on the CCR website, www.clinicaltrials.gov and on NIH social media forums. Outside providers and colleagues may directly refer participants for screening into this study.
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2.2 screening evaluation

2.2.1 Screening activities performed prior to obtaining informed consent Minimal risk activities that may be performed before the subject has signed a consent include the following:
- Email, written, in person or telephone communications with prospective subjects  
- Review of existing medical records to include H&P, laboratory studies, etc.  
- Review of existing MRI, x-ray, or CT images
- Review of existing photographs or videos
- Review of existing pathology specimens/reports from a specimen obtained for diagnostic purposes.  
2.2.2 Screening activities performed after a consent for screening has been signed
The following activities will be performed only after the subject has signed the consent for study \#01-C-0129 (Eligibility Screening and Tissue Procurement for the NIH Intramural Research Program Clinical Protocols). Assessments performed at outside facilities or on another NIH protocol within the timeframes below may also be used to determine eligibility once a participant has signed the consent. Within 14 days prior to treatment unless otherwise noted below:  
- Complete medical history and physical examination, including height, weight, vital signs, and ECOG performance status.
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- ekg

- Laboratory Evaluation  
o Hematological profile: CBC with differential and platelet count; o Biochemical profile: electrolytes, BUN, creatinine, AST, ALT, total bilirubin, calcium, phosphorus, albumin, magnesium, uric acid; o PT/PTT;
o Cholesterol (fasting);
o Serum or urine pregnancy test for female participants of childbearing age (in the absence of prior hysterectomy) (7 days prior to treatment);  
o Urinalysis o Blood or buccal test for defining of UGT1A1 status by polymerase chain reaction
(PCR) (any time prior to enrollment, outside test results are acceptable)
- CT/MRI of chest, abdomen and pelvis; - Brain MRI (if clinically indicated); - Tumor evaluation / tumor measurements; - Histologic or cytologic confirmation from any certified laboratory (at any time point prior to enrollment). If there is no available documentation, biopsy will be performed to confirm the diagnosis.
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2.3 participant registration and status

Registration and status updates (e.g., when a participant is taken off protocol therapy and when a participant is taken off-study) will take place per CCR SOP ADCR-2, CCR Participant Registration & Status Updates found at: https://ccrod.cancer.gov/confluence/pages/viewpage.action?pageId=73203825. 2.3.1 Treatment Assignment Procedures  
| Number   | Name      | Description                                                                                                                                             |
|----------|-----------|---------------------------------------------------------------------------------------------------------------------------------------------------------|
| 1        | Phase I   | Subjects with solid tumors enrolled to PLX038 and rucaparib escalation  dose levels.                                                                    |
| 2        | Phase IIA | Subjects with SCLC enrolled at the MTD of PLX038 and rucaparib  after the MTD of PLX038 and rucaparib is established.                                   |
| 3        | Phase IIB | Subjects with extra-pulmonary small cell carcinomas enrolled at the  MTD of PLX038 and rucaparib after the MTD of PLX038 and  rucaparib is established. |  
| Number   | Name   | Description                              |
|----------|--------|------------------------------------------|
| 1        | Arm 1  | Escalating doses of PLX038 and rucaparib |
| 2        | Arm 2  | MTD of PLX038 and rucaparib              |
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arm assignment

Subjects in cohort 1 will be directly assigned to Arm 1. Subjects in cohorts 2 and 3 will be directly assigned to Arm 2.
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2.4 baseline evaluation

Tests done at screening do not need to be repeated on baseline if performed in designated time frame prior to start of study treatment. Within 14 days prior to first dose:
- CT/MRI of chest, abdomen and pelvis  
- Tumor evaluation / measurements - Optional tumor research biopsy - Baseline symptoms evaluation
- Concomitant medication
- Collection of available unstained slides or a block from previous biopsies/surgeries for research
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study implementation 3.1 study design

This is an open label Phase I/II trial, accruing initially one cohort to determine maximum tolerated dose (MTD) of combined treatment of PLX038 and rucaparib (Phase I); and to examine safety and efficacy of the PLX038 in combination with rucaparib in the following cohorts (Phase IIA and IIB). Up to 3 dose levels of combined treatment of PLX038 and rucaparib will be tested in Phase I
(**Table 9**) with up to 18 subjects enrolled in addition to the 8 participants treated prior to amendment version 03/19/2021. Once an MTD of combined treatment of PLX038 and rucaparib has been determined, up to 35 subjects may be evaluated at MTD in the Phase II cohorts, inclusive of those participants treated at the MTD during the Phase I if they are eligible for the phase II evaluation. Participants will receive treatment in cycles consisting of 21 (+7) days. Administration of PLX038 will be every 3 weeks by IV infusion starting on day 1 of cycle 1.  
Granulocyte-colony stimulating factors (G-CSF) should not be used within at least 24 hours of PLX038 administration. Outside of this restriction window, G-CSF may be administered as clinically indicated.  
Rucaparib will be administered on days 6 to 19 of a 21-day cycle starting at 300 mg PO BID. Treatment with PLX038 and rucaparib will continue until participant meets off treatment criteria
(Section **3.7.1**).  
Granulocyte-colony stimulating factors (G-CSF) will be given prophylactically in each cycle to prevent/treat neutropenia (for both phase 1 and phase 2). G-CSF will be administered at least 72hours after PLX038 in each cycle, with at least 14 days elapsing until the next planned chemotherapy dose. Optional biopsies may be performed at: baseline, on day 4 or 6 of Cycle 1 (prior to rucaparib dosing) and between days 7 and 14 of Cycle 1. Participants may be admitted for cycle 1 as there are PK studies planned to be performed. 3.1.1 Dose Limiting Toxicity The DLT period is one cycle, 21 days. The following events will be considered DLTs if deemed drug-related (CTCAE v5.0):  
- Grade 3 or 4 neutropenia complicated by fever ≥ 38.5°C (i.e. febrile neutropenia) and/or documented infection;
- Grade 4 neutropenia that does not resolve within 7 days - Grade 4 thrombocytopenia or grade 3 thrombocytopenia complicated with hemorrhage;
- Grade 4 anemia that does not resolve within 7 days despite optimal therapy;  
- Inability to begin subsequent treatment course within 21 days of the scheduled date, due to study drug toxicity;
- Any grade 3 non-hematologic toxicity with the following exceptions o fatigue/asthenia lasting less than 2 weeks in duration o mucositis in subjects who have not received optimal therapy for mucositis o vomiting or diarrhea lasting less than 72 hours whether treated with an optimal antiemetic or anti-diarrheal regimen or not o alkaline phosphatase changes 3.1.2 Phase I Cohort
Dose escalation will follow the classical '3+3' trial design by Fibonacci sequence with dose levels defined in **Table 9**.  
Starting dose level is Dose level 1B. If none of the first three participants in a Dose level group experiences a dose-limiting toxicity during the DLT period, another three participants will be treated at the next highest dose level. However, if one of the first three participants experiences a dose-limiting toxicity during DLT period, three more participants will be treated at the same dose level. Dose escalation continues until the final dose level meets safety criteria (< 2 DLTs in 6 participants during DLT period) or at least two participants among a Dose level group of three to six participants experience doselimiting toxicities.  
Note: If there are ≥ 2 DLTs in the Dose level 1B, we will consider amending the study with new dose levels.  
| Dose level           | PLX038 every 3 weeks, IV   | Rucaparib, PO BID   |
|----------------------|----------------------------|---------------------|
| Former dose level 1  | 1.3 g/m2                   | 400 mg, days 3-19   |
| (completed)          |                            |                     |
| Former dose level 1A | 1.3 g/m2                   | 300mg, days 5-19    |
| (completed)          |                            |                     |
| 1B                   | 580 mg/m2                  | 300mg, days 6-19    |
| 2B                   | 870 mg/m2                  | 300mg, days 6-19    |
| 3B                   | 1000 mg/m2                 | 300mg, days 6-19    |  
Table 9. Dosing schedule of PEGSN38 and rucaparib.  
PLX038 dose will be capped at 2000 mg total dose.  
G-CSF will be administered at least 72-hours after PLX038 in each cycle.  
The MTD is the dose level at which no more than 1 of 6 participants experience DLT during the DLT evaluation period, and the dose below that at which at least 2 (of 6) participants have DLT
as a result of the drug. Every subject in each dose level group of the safety run-in will be observed for at least 4 weeks after first dose of PLX038 before the subsequent subject can be treated. Subjects who do not complete the DLT observation period for reasons other than a DLT will be replaced and not included in the DLT evaluation.  
Intra-participant PLX038 and rucaparib dose escalation or de-escalation are not permitted for subjects enrolled in the Phase I during the DLT finding period.  
In case of DLT definitely attributed to one of the study drugs, participant will be taken off this drug and per PI discretion may continue treatment with the other drug alone.  
Participant will be eligible for the DLT evaluation if at least ≥ 85 percent of rucaparib scheduled doses were taken within the DLT period.  
Phase II Cohorts 3.1.3 The safety and efficacy evaluation of the combination will continue during Phase II with the PLX038 and rucaparib MTD identified during phase I. We will initially enroll 16 evaluable subjects into cohort Phase IIA (inclusive of those participants with SCLC treated at the MTD during the safety run-in). If 2 or more of the first 16 subjects have clinical benefit, then accrual would continue to a total of 25 subjects. If less than 2 subjects have clinical benefit, enrollment into this cohort will be closed.  
Simultaneously with enrollment of participants into cohort Phase IIA, up to 10 participants with extrapulmonary small cell cancers may be enrolled into cohort Phase IIB. CBR of these participants will not be included in the primary statistical analysis and will be described in an exploratory manner.  
Enrollment into phase II part of the study can commence after DLT period of 6 th subject of respective Dose level group is complete.
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3.2 study stopping rules

For safety reasons, enrollment will be temporarily halted until an expedited safety report is sent to and reviewed by the FDA and the SAE has been evaluated by the investigators for grade 5 toxicity attributable to treatment regimen occurring within 30 days of receiving investigational agents. The stopping rule has been met with two patients having grade 5 events at dose level 1A, but will be applicable to future subjects who enroll.
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3.3 drug administration 3.3.1 plx038

PLX038 will be administered as a 1-hour (-10 minutes / +30 minutes) IV infusion on Day 1 of each cycle (21 days). PLX038 vials (220 mg/vial) should be brought to room temperature before use. However, the final diluted product should ideally be used as soon as possible. Vital signs will be collected within 1 hour before PLX038 infusions, at least once during the infusions, and within 30 minutes after the completion of the infusion. To calculate the dosage, height measured at screening and weight measured at day 1 of current cycle will be used. 3.3.2 Rucaparib Rucaparib will be given orally at designated dose twice a day on days 6 to 19 of every 21-day cycle. There should be a minimum 5 day window between PLX038 and rucaparib. Rucaparib should be taken at approximately the same times each day. Doses should be taken within 2 hours of the scheduled time. In case of a missed dose (more than 2 hours late) or vomiting after taking rucaparib, participants will be instructed not to make up the missed dose. Missing of 15% of the doses for any given cycle is allowed. Participants will be recommended to have 8 mg of ondansetron taken with small meal or snack to prevent nausea and vomiting approximately 30 minutes prior to each dose of rucaparib.  
Participants will complete and return Participant's Diary (**Appendix B**).
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3.4 dose delay or modifications

In case of toxicity as defined below definitely attributed to one of the study drugs, participant will be taken off this drug and per PI discretion may continue treatment with another drug only. For participants who are on combination therapy and benefiting from treatment, since we don't know which agent is driving the response (i.e. either of the drugs alone or the combination), in the event that one drug is causing toxicities and has to be discontinued, it is reasonable to continue the other drug to see if the participant might benefit from it. 3.4.1 Phase I during evaluation period See Section 3.1.2.
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3.4.2

Phase I after DLT evaluation period and Phase II
When, at the beginning of a treatment cycle, treatment delay related to PLX038 is indicated, treatment with rucaparib must be delayed too. There should be a minimum 48-hour window between PLX038 and rucaparib.  
If, in the opinion of the investigator, a toxicity is considered to be due solely to one drug, the dose of another drug does not require modification.  
The dose of PLX038 and rucaparib may be reduced for toxicity using the following guidelines depending on the toxicities (and drug deemed to be responsible for toxicity) observed.  
| Dose level           | Rucaparib dose modifications (mg BID)   |                       |                                   |
|----------------------|-----------------------------------------|-----------------------|-----------------------------------|
| 100%                 | First dose reduction                    | Second dose reduction |                                   |
| lB                   | 300                                     | 200                   | NA (participant will be taken off |
| rucaparib treatment) |                                         |                       |                                   |
| 2B                   | 300                                     | 200                   | NA (participant will be taken off |
| rucaparib treatment) |                                         |                       |                                   |
| 3B                   | 300                                     | 200                   | NA (participant will be taken off |
| rucaparib treatment) |                                         |                       |                                   |
| Dose level           | PLX038 dose modifications (mg/m 2 )     |                       |                                   |
| 100%                 | First dose reduction                    | Second dose reduction |                                   |
| lB                   | 580                                     | 300                   | NA (participant will be taken off |
| PLX038 treatment)    |                                         |                       |                                   |
| 2B                   | 870                                     | 580                   | 300                               |
| 3B                   | 1000                                    | 870                   | 580                               |  
Table 10: Dose reductions for rucaparib and PLX038
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3.4.2.1

PLX038 toxicity management Grades 1 and 2 do not need dose adjustments For grades 3 and 4, dose should be interrupted for up to 21 days. If resolved to Grade 2 or less, reduced Dose (see Table 10) will be used during next treatment cycle. If not resolved during 21 days, participant will be taken off PLX038 treatment. Note: grade 3 nausea which resolves to grade 1 within 7 days with appropriate supportive care and grade 3/4 lymphopenia do not need dose ajustments.  
Rucaparib toxicity management 3.4.2.2 Grades 1 and 2 do not need dose adjustments For grades 3 and 4, dose should be interrupted for up to 21 days. If resolved to Grade 2 or less, reduced Dose (see Table 10) will be used during next treatment cycle. If not resolved during 21  
days, participant will be taken off PLX038 treatment. Note: grade 3 nausea which resolves to grade 1 within 7 days with appropriate supportive care and grade 3/4 lymphopenia do not need dose adjustments.  
47 Version Date: 02/02/2023  
| 3.5                           | Study Calendar   | All Subsequent    |        |       |       |
|-------------------------------|------------------|-------------------|--------|-------|-------|
| C1                            | Cycles           | 30                | Long   |       |       |
| Baseline/                     | Day 1 ¹          | Days              | Term   |       |       |
| Procedure                     | Screening        | C1D11             | Safety |       |       |
| C1D4                          | C1D6             | C1D7              | C1D8   | C1D10 | FU 12 |
| (Cycle=21+7                   | FUll,13          |                   |        |       |       |
| days 2 )                      |                  |                   |        |       |       |
| PLX038 ²                      | X                | X                 |        |       |       |
| x -                           | ↑                |                   |        |       |       |
| Rucaparib 3                   | X                |                   |        |       |       |
| Medical History               | X                |                   |        |       |       |
| Height                        | x                |                   |        |       |       |
| Histologic confirmation of    | x                |                   |        |       |       |
| disease                       |                  |                   |        |       |       |
| UGT1A1 testing                | X                |                   |        |       |       |
| EKG                           | x                |                   |        |       |       |
| Physical exam, weight and     | x                | X                 | X      |       |       |
| ECOG                          |                  |                   |        |       |       |
| Vital Signs                   | x                | x 4               | x      |       |       |
| x 14                          |                  |                   |        |       |       |
| CBC w/differential, platelets | x                | X                 | X      |       |       |
| x16                           |                  |                   |        |       |       |
| Cholesterol                   | x                |                   |        |       |       |
| PT/PTT                        | X                |                   |        |       |       |
| X                             | X                |                   |        |       |       |
| Biochemical profile 5         | X                |                   |        |       |       |
| Rdiologic Evaluation          | x                | x                 | x      | x     |       |
| Brain MRI if clinically       | X                |                   |        |       |       |
| indicated                     |                  |                   |        |       |       |  
| All Subsequent               |          |                  |                    |       |       |
|------------------------------|----------|------------------|--------------------|-------|-------|
| C1                           | 30       |                  |                    |       |       |
| Cycles                       | Long     |                  |                    |       |       |
| Baseline/                    | Day 1 1  | Days             |                    |       |       |
| Procedure                    | Term     |                  |                    |       |       |
| Screening                    | C1D11    | Safety           |                    |       |       |
| C1D4                         | C1D6     | C1D7             | C1D8               | C1D10 | FU 12 |
| (Cycle=21+7                  | FU 11,13 |                  |                    |       |       |
| days 2 )                     |          |                  |                    |       |       |
| Tumor evaluation / tumor     | x        | X                | x                  | x     |       |
| measurements 6               |          |                  |                    |       |       |
| Urinalysis                   | x        |                  |                    |       |       |
| Serum or urine pregnancy     | x¹       | X                |                    |       |       |
| test                         |          |                  |                    |       |       |
| Concomitant medications      | X        | X                |                    |       |       |
| Adverse event evaluation     | X        | X                |                    |       |       |
| Baseline symptoms            | X        |                  |                    |       |       |
| evaluation                   | X        | X                |                    |       |       |
| Tumor biopsy 7               | X        | (day 4 or day 6) | (between day 7-14) |       |       |
| Research blood for PLX038    | X        | X                | X                  |       |       |
| level 8                      |          |                  |                    |       |       |
| Research blood for rucaparib | X        | x                |                    |       |       |
| level 9                      |          |                  |                    |       |       |
| Research blood for Immune    | X        | X                | X                  |       |       |
| Subset Analysis 17           |          |                  |                    |       |       |
| Research blood for germline  | X        |                  |                    |       |       |
| DNA                          |          |                  |                    |       |       |
| Research blood for PBMC      | x        |                  |                    |       |       |
| X                            | X        | X                |                    |       |       |
| PARylation and gH2AX18       |          |                  |                    |       |       |
| Research blood for           | X        | X                |                    |       |       |
| Circulating tumor DNA 19     |          |                  |                    |       |       |  
| All Subsequent                 |           |       |        |       |             |        |
|--------------------------------|-----------|-------|--------|-------|-------------|--------|
| C1                             | Cycles    | 30    | Long   |       |             |        |
| Baseline/                      | Day 1 1   | Days  | Term   |       |             |        |
| Procedure                      | Screening | C1D11 | Safety | FU 12 |             |        |
| C1D4                           | C1D6      | C1D7  | C1D8   | C1D10 | (Cycle=21+7 | EUI,13 |
| days")                         |           |       |        |       |             |        |
| Research blood for PLX038      | X         | X     |        |       |             |        |
| coagulation studies 20         |           |       |        |       |             |        |
| Collection of archival tumor   | X         |       |        |       |             |        |
| samples for research 15        | x         | x     | x      | x     |             |        |
| Collection of hair follicles10 |           |       |        |       |             |        |
| Phone call or e-mail for       | X         |       |        |       |             |        |
| survival every 6 month         |           |       |        |       |             |        |  
Baseline and C1D1 evaluations do not need to be repeated if performed at screening or baseline in designated time frame. All evaluations 1.  
will be done within 14 days before treatment initiation on Day 1 of Cycle 1(except for pregnancy test which should be performed within 7 dys). If treatment does not start within 28 days after enrollment, screening evaluations will be repeated. For all subsequent cycles, all evaluations are to be done within 7 days of cycle treatment initiation.  
2.  
PLX038 via IV infusion on Day 1 of each cycle. Note: A cycle may vary in length (21 (+ 7) days) due to logistical reasons. PLX038 will be administered as a 1 hour (-10 minutes / +30 minutes) IV infusion.  
PO, BID on days 6-19 of every 21 days cycle. If cycle length varies, note that approximately 5 days must elapse between last dose of 3.  
PLX038 and rucaparib.  
Vital signs will be collected within 1 hour before PLX038 infusions, at least once during the infusions, and within 30 minutes after the 4.  
completion of the infusion.  
Biochemical Profile: electrolytes, BUN, creatinine, AST, ALT, total bilirubin, calcium, phosphorus, albumin, magnesium, uric acid.  
5.  
CT/MRI of chest, abdomen and pelvis at screening/baseline and every 9 (+/-1) weeks after start of study therapy. If participant is taken off 6.  
treatment for reason other than disease progression, imaging will continue during follow-up until disease progression.  
7.  
Optional tumor biopsies may be performed at baseline, on day 4 or 6 of Cycle 1 (prior to rucaparib dosing) and between days 7 and 14 of Cycle 1.  
8.  
Cycle 1 day 1: before PLX038 infusion, end of infusion (EOI) (+5 minutes), 2 (+/- 15 minutes) hours, 4 (+/- 15 minutes) hours and 24 (+/-
30 minutes) hours post EOI; cycle 1 day 6: just before starting rucaparib, cycle 2 day 1: before PLX038 infusion.  
9.  
Cycle 1 day 8 (optional): before rucaparib, 2 hours (+/- 15 minutes), 3 hours (+/- 15 minutes), 4 hours (+/- 15 minutes) and 24 hours (+/- 1 hour) post rucaparib dosing. Samples will also be collected on day 1 of all subsequent cycles before PLX038 dosing.
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3.4.2.1

10. Collected pre-treatments on C1D1, C1D6 and C1D7 (24 hours after rucaparib dosing) and C2D1 before PLX038 infusion. To minimize participant discomfort, if good quality hair follicles are not collected at baseline (C1D1) or at the second collection (C1D6), no further hair collection will be done.  
11. Follow up visit is planned to be performed at 30 (+/- 7 days) after treatment discontinuation to evaluate participant's safety.  
12. After safety FU visit, subjects will be followed every 6 months (± 1 month) for survival by phone call or e-mail. **NOTE:** if participant is taken off treatment for reason other than disease progression, we will continue to invite participant every 9 (+/-1) weeks for imaging studies. Outside scans are acceptable.  
13. If subjects are not willing to come to NIH for FU visits, they will be contacted by phone call or e-mail for adverse events (refer to 6.1 for AE collection).  
14. Sample will be collected on C1D10 +/- 3 days.  
15. Collection of available unstained slides or a block from previous biopsies/surgeries for research will be done within 14 days per 2.4.  
16. Cholesterol will be monitored at least once at the C3D1 or C4D1 timepoint or earlier in the treatment regimen.  
17. Immune Subset Analysisresearch blood will be collected at PLX038 Pre-treatment on C1D1, C1D7 (24 hours after rucaparib) and PLX038 pre-treatment C2D1 per **5.3.5**.  
18. PBMC PARylation and gH2AX research blood will be collected at C1D1 (before PLX038), C1D6 (prior to rucaparib), C1D7 (24 hours after rucaparib), C2D1 (before PLX038). Blood sample does not need to be collected if hair sample is not collected.  
19. Circulating tumor DNA research blood will be collected at PLX038 pre-treatment on C1D1, C2D1 and at disease progression. 20. PLX038 coagulation assay blood will be collection C1D1 before PLX038, C1D1 2 hours post PLX038 EOI and C2D1 before PLX038.
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3.6 cost and compensation 3.6.1

NIH does not bill health insurance companies or participants for any research or related clinical care that participants receive at the NIH Clinical Center. If some tests and procedures are performed outside the NIH Clinical Center, participants may have to pay for these costs if they are not covered by insurance company. Medicines that are not part of the study treatment will not be provided or paid for by the NIH Clinical Center. 3.6.2 Compensation N/A 3.6.3 Reimbursement This study offers subject reimbursement or payment for travel, lodging and/or meals while participating in the research. The amount, if any, is guided by NIH policies and guidelines. On this study, the NCI will cover the cost for some of the expenses. Some of the costs may be paid directly by the NIH and some may be reimbursed to the subject. Someone will work with subjects to provide more information.
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3.7 criteria for removal from

Prior to removal from study, efforts must be made to have all subjects complete a safety visit approximately 30 days following the last dose of study therapy. 3.7.1 Criteria for Removal from Protocol Therapy  
- Progressive disease
- Excessive toxicity attributed to both drugs (see sections **3.1.2** and 3.4)
- PI discretion
- Positive pregnancy test
- PLX038 and rucaparib become unavailable 3.7.2 Off -Study Criteria
- Death - Participant request to be withdrawn from study
- PI discretion
- Lost to follow up
- PI decision to end the study 3.7.3 Lost to Follow-up
A participant will be considered lost to follow-up if he or she fails to return for 3 scheduled visits and is unable to be contacted by the study site staff. The following actions must be taken if a participant fails to return to the clinic for a required study visit:  
- The site will attempt to contact the participant and reschedule the missed visits and counsel the participant on the importance of maintaining the assigned visit schedule and ascertain if the participant wishes to and/or should continue in the study.  
- Before a participant is deemed lost to follow-up, the investigator or designee will make every effort to regain contact with the participant (telephone calls and if necessary, an IRB approved certified letter to the participant's last known mailing address or local equivalent methods). These contact attempts should be documented in the participant's medical record or study file.
Should the participant continue to be unreachable, he or she will be considered to have withdrawn from the study with a primary reason of lost to follow-up.
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concomitant medications/measures

All routine and appropriate supportive care (including blood products) will be provided during this study, as clinically indicated, and in accordance with the standard of care practices. Clinical judgment should be utilized in the treatment of any AE experienced by the participant.
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4.1 prohibited medications 4.1.1 strong

Strong inducers or inhibitors of CYP3A4 and drugs that inhibit UGT1A1 should not be administered while on study treatment. UGT1A1 inhibitors include indinavir, atazanavir, nilotinib, and sorafenib (as well as certain herbal extracts). Additional guidance can be found in the following link: https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-anddrug-interactions-table-substrates-inhibitors-and-inducers\#table3-2.
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4.2 required medication 4.2.1 g-csf

Granulocyte-colony stimulating factors (G-CSF) are required to be administered prophylactically for all participants to prevent/treat neutropenia. G-CSF will be administered at least 72-hours after the dose of PLX038 in each cycle, with at least 14 days elapsing until the next planned chemotherapy dose..
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4.3 recommended medication

Participants will be recommended to take 8 mg of ondansetron with a small meal or snack to prevent nausea and vomiting approximately 30 minutes prior to each dose of rucaparib.
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correlatives studies for reserach 5.1

A description of correlative studies including a brief statement of rationale and processing information is made below.  
| Sample volume                      |                    |                                    |                      |
|------------------------------------|--------------------|------------------------------------|----------------------|
| Test/assay                         | Type of tube a     | Collection timepoint               | Location of specimen |
| (pprox.)                           |                    |                                    |                      |
| Peripheral blood                   | 1) C1D1            |                                    |                      |
| o before PLX038                    |                    |                                    |                      |
| o EOI (+5 minutes)                 |                    |                                    |                      |
| PLX038 Pharmacokinetic             | 6 mL Purple (LVV)  | 0 2 hours post EOI (+/- 15 min)    |                      |
| 5 mL                               |                    |                                    |                      |
| Analysis                           | tube               | 0 4 hours post EOI (+/- 15 min)    |                      |
| ️ 24 hours post EOI (+/- 30 min)    |                    |                                    |                      |
| 2) C1D6 (before rucaparib)         |                    |                                    |                      |
| 3) C2D1 (before PLX038)            | Blood Processing   |                                    |                      |
| 1) C1D8 (optional)                 | Core (BPC)         |                                    |                      |
| o before rucaparib                 |                    |                                    |                      |
| 0 2 hours post dosing (+/- 15 min) |                    |                                    |                      |
| 0 3 hours post dosing (+/- 15 min) |                    |                                    |                      |
| Rucaparib                          | 6 mL Purple (LVV)  | 0 4 hours post dosing (+/- 15 min) |                      |
| 5 mL                               |                    |                                    |                      |
| Pharmacokinetic Analysis           | tube               | 0 24 hours post dosing (+/- 60     |                      |
| mm)                                |                    |                                    |                      |
| 2) C2D1 (before PLX038)            |                    |                                    |                      |
| 3) C3D1 (before PLX038)            |                    |                                    |                      |
| 4) C4D1 (before PLX038)            |                    |                                    |                      |
| 1) C1D1 (before PLX038)            |                    |                                    |                      |
| 8ml CPT citrate                    | Laboratory of Jane |                                    |                      |
| Immune subset analysis             | 16 ml              | 2) C1D7 (24 hours after rucaparib) |                      |
| blue/black top tubes               | Trepel             |                                    |                      |
| 3) C2D1 (before PLX038)            |                    |                                    |                      |
| 1) Baseline                        |                    |                                    |                      |
| 3ml light blue citrate             | Blood Processing   |                                    |                      |
| Blood for germline DNA             | 3ml                | Core (BPC)                         |                      |
| tube                               |                    |                                    |                      |  
Version Date: 02/02/2023  
| Sample volume             |                           |                                    |                      |
|---------------------------|---------------------------|------------------------------------|----------------------|
| Test/assay                | Type of tube a            | Collection timepoint               | Location of specimen |
| (pprox.)                  | 1) C1D1 (before PLX038)   | Blood Processing                   |                      |
| PBMC PARylation and       | 6 mL Purple (LVV)         | 2) C1D6 (prior to rucaparib)       | Core (BPC), analysis |
| gH2AXb                    | 5ml                       | 3) C1D7 (24 hours after rucaparib) |                      |
| tube                      | to be performed by        |                                    |                      |
| 2) C2D1 (before PLX038)   | Suresh Kumar, DTB         |                                    |                      |
| 1) C1D1(before PLX038)    | Blood Processing          |                                    |                      |
| 10ml                      | cfDNA Streck tubes        | 2) C2D1(before PLX038)             |                      |
| Circulating tumor DNA     | Core (BPC)                |                                    |                      |
| 4) At progression         |                           |                                    |                      |
| 1) C1D1                   |                           |                                    |                      |
| PLX038 Coagulation        | 3ml light blue citrate    | o before PLX038                    | NIH DLM / Mayo       |
| 24 mL                     |                           |                                    |                      |
| Studies                   | tube (8 tubes)            | 0 2 hours post EOI (+/- 15 min)    | Clinic               |
| 2) C2D1 (before PLX038)   |                           |                                    |                      |
| Tumor Biopsies            |                           |                                    |                      |
| yH2AX or other DNA        | 1) C1D1                   |                                    |                      |
| 2) C1D4 or C1D6 (prior to |                           |                                    |                      |
| damage markers by         | Frozen samples¬           |                                    |                      |
| confocal                  | rucaparib)                | Laboratory of Jane                 |                      |
| microscopy/ELISA          | 3) between C1D7 and C1D14 | Trepel                             |                      |
| PARylation by poly        |                           |                                    |                      |
| (DP-ribose) assay         | Tumor sample              | Formalin samples-                  |                      |
| SLFN11 by IHC and/or      | Blood Processing          |                                    |                      |
| RNA                       | Core (BPC), analysis      |                                    |                      |
| to be performed by        |                           |                                    |                      |
| Whole exome               | Suresh Kumar, DTB         |                                    |                      |
| sequencing/RNAseq-        |                           |                                    |                      |
| bulk and or scRNA         |                           |                                    |                      |  
Version Date: 02/02/2023  
| Sample volume                                                                  | Type of tubeª                                                                                                                       |                      |
|--------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------|----------------------|
| Test/assay                                                                     | Collection timepoint                                                                                                                | Location of specimen |
| (pprox.)                                                                       |                                                                                                                                     |                      |
| Archival tumor                                                                 | Blood Processing                                                                                                                    |                      |
| Baseline                                                                       |                                                                                                                                     |                      |
| Whole exome                                                                    | Core (BPC), analysis                                                                                                                |                      |
| N/A (Archival tumor)                                                           |                                                                                                                                     |                      |
| sequencing/RNAseq                                                              | to be performed by                                                                                                                  |                      |
| Suresh Kumar, DTB                                                              |                                                                                                                                     |                      |
| Hair follicles                                                                 | 1) C1D1 (before PLX038)                                                                                                             |                      |
| yH2AX by confocal                                                              | Christophe Redon,                                                                                                                   |                      |
| 2) C1D6 (prior to rucaparib)                                                   |                                                                                                                                     |                      |
| N/A (Hair follicles)                                                           |                                                                                                                                     |                      |
| microscope/ELISA                                                               | 3) C1D7 (24 hours after rucaparib)                                                                                                  | DTB                  |
| 4) C2D1 (before PLX038)                                                        |                                                                                                                                     |                      |
| a.                                                                             | Please note that tubes and media may be substituted based on availability with the permission of the PI or laboratory investigator. |                      |
| b. Blood sample does not need to be collected if hair sample is not collected. |                                                                                                                                     |                      |
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5.2 collection of samples 5.2.1

Blood samples for PK will be collected at time points indicated in the Study Calendar 3.5. PK
blood samples will be sent and processed by the Blood Processing Core (BPC). Non-PK blood samples will be sent to and processed by the Trepel Lab.
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5.2.2 tumor samples

All possible attempts will be made to acquire archival pathologic tissue (i.e. original slides or paraffin blocks) or fresh frozen tumor (where available) for purpose of molecular studies. If a tumor block is not available, at least 20 unstained slides may be collected.  
Three optional tumor biopsies may be performed at time points indicated in Study Calendar 3.5.  
Frozen tumor samples will be procured by the Trepel lab. Tissue for formalin fixation will be sent to the Laboratory of Pathology. Formalin-fixed samples will be analyzed for disease first, leftover will be used for research. Germline DNA will be collected for accurate culling of somatic variants from the tumor sample. 5.2.3 Hair follicles Hair follicles will be collected at time points indicated in the Study Calendar 3.5. Upon delivery in Dr. Redon lab, hairs will be fixed with paraformaldehyde and analyzed under a dissection microscope to select those containing a full intact follicle and sheath.
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5.3 correlative studies for research

Blood samples for the determination of PLX038 and rucaparib plasma trough levels will be obtained from participating participants at time points indicated in Study Calendar 3.5.  
Bioanalytical measurements will be conducted by the Clinical Pharmacology Program (CPP).  
Blood samples for the determination of Rucaparib will be collected in room temperature lavendertop (EDTA) tubes.  
The PLX038 collection tubes will also be lavender-top, but be pre-chilled and contain 1M citrate buffer with 0.1% Pluronic F68, pH4.5 in a 1:10 ratio with the volume of blood drawn. Tubes can be prechilled by completely immersing blood collection tube in bag of ice. After draw, gently invert the tube 3-5 times and immediately immerse the tube into the ice. Specimen must be processed within 1 hour of draw. Page Figg lab for sample pick up at 102-11964. 5.3.2 The formation of γH2AX foci γH2AX, the phosphorylated form of histone H2A histone family member X (H2AX) at serine 139, is a marker of DNA double-strand breaks. The formation of γH2AX foci of will be evaluated on plucked hair follicles and tumor by ELISA/confocal microscope. Plucked hairs and tumor will be fluorescently stained for γ-H2AX. 5.3.3 PARP inhibition PARP inhibition will be evaluated in pharmacodynamic studies by means of a functional assay (Mesoscale Discovery) involving the analysis of poly(ADP-ribose) (PAR) formation from peripheral-blood mononuclear cells and tumor-tissue cell lysates, all normalized to the amount of PARP1 protein present.
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5.3.4 slfn11

Expression of the gene SLFN11 has been found to correlate with the activity of topoisomerase inhibitors in studies using the National Cancer Institute cell line panel (NCI60) and the Cancer Cell Line Encyclopedia (CCLE) [44, 45]. SLFN11 expression predicted sensitivity to DNA damaging chemotherapy including Top1 and Top2 inhibitors, alkylating agents, platinum derivatives, DNA synthesis and PARP inhibitors [44-46]. In experiments using cells with endogenously high and low SLFN11 expression and siRNA- and Crispr-mediated silencing, SLFN11 was found to be causative in determining cell cycle arrest and cell death in response to DNA damaging agents in cancer cells [46]. Data from the CCLE, the NCI60 and The Cancer Genome Atlas (TCGA) indicate a broad range of SLFN11 expression in lung cancers, raising the possibility that high SLFN11 expression might enrich for tumors that are more likely to respond to DNA damaging chemotherapy; conversely low SLFN11 expression may predict tumors that are likely resistant. SLFN11 is frequently inactivated in cancer cell lines and has been shown to sensitize cancer cells to anticancer drugs. In particular, elevated SLFN11 expression is associated with sensitivity to DNA-damaging agents which concurrently promote replication fork stalling and cell cycle checkpoint activation, and induce replication stress [47]. SLFN11 is highly expressed in SCLC as compared with other histologies [23]. In contrast, SLFN11 expression is low to nearly absent in lung squamous cell carcinoma and adenocarcinoma [48]. SLFN11 expression has a bimodal distribution in SCLC and may provide meaningful stratification as a predictive biomarker in clinical studies of SCLC. SLFN11 gene expression by RNA-Seq is concordant with SLFN11 protein expression by quantitative western blot. SCLC cells with high SLFN11 expression are more sensitive to DNA-damaging chemotherapy, and SLFN11 inactivation confers resistance to these agents [23]. Participants with SLFN11positive tumors treated with a combination of temozolomide and veliparib had a significantly prolonged PFS and OS compared with participants with SLFN11-negative tumors. Consistent with its role in determining chemosensitivity, SLFN11 expression is higher in tumors from SCLC
participants who respond to DNA-damaging therapy versus those who do not and is higher in tumors from treatment-naive SCLC participants than in recurrent/relapsed SCLC [48]. Recent studies have shown that SLFN11 suppression by epigenetic silencing could be causal to acquired resistance to DNA-damaging chemotherapy in SCLC [48-50]. Based on the above considerations, we hypothesize that relapsed SCLC tumors with high SLFN11 expression would be sensitive to PARP inhibitors and camptothecins. Pre-treatment SLFN11 expression in tumor samples will be assessed (IHC and RNA sequence
(Section **5.3.8**)) to assess in an exploratory manner, the potentially role of SLFN11 as a predictor of response to PLX038 plus rucaparib. 5.3.5 Immune Subset Analysis Peripheral blood will be drawn into two 8ml BD Vacutainer Cell Preparation Tubes (CPT) with Sodium Citrate per 3.5 and 5.2.  
Depending on viable PBMC number, the following immune subsets will be assessed using multiparameter flow cytometry including but not necessarily limited to CD8+ T-cells, CD4+Foxp3- T-cells, Tregs, monocyte subsets, MDSC subsets. Assessment will include functional markers, i.e. PD-1, Tim-3, CTLA-4, PD-L1, HLA-DR and/or CD40. 5.3.6 Circulating Tumor DNA Circulating tumor DNA is a promising biomarker that is being investigated in multiple tumor types. Changes in the levels of circulating tumor DNA can be used to monitor disease course, treatment responses, and recurrences. 5.3.7 Interference of PLX038 with coagulation assays On 20C0013 to date, after PLX038 infusion, 100% of patient who had post-infusions PTT checked, had new prolonged PTTs. Extensive evaluation in one patient showed that that the PTT prolongation was assay-specific and therefore did not representative of a true coagulation defect. Specifically, there was prolongation of the PTT using an assay with rabbit cephalin phospholipid with micronized silica activator but not with other PTT assays, suggesting *in vitro* assay interference but not a true *in vivo* coagulation defect such as an acquired clotting factor inhibitor. This has great significance for acutely ill patients with cancer receiving this drug, since interventions to treat an *in vivo* "inhibitor" that is a laboratory artifact would result in extended hospitalizations and unwarranted treatments with potentially toxic agents. A similar pattern has been described of a few other pegylated agents [51-54]. We hypothesize that PLX038 will interfere with PTT assays that use the micronized silica or colloidal silica dispersion activators, but not with other PTT assays, including those using kaolin, polyphenolic, or colloidal silica activators, based on the pattern described for a small few other pegylated agents and the mechanism of coagulation activation in these various assays [51-54]. We hypothesize that the remainder of the coagulation assays will be unaffected. We also hypothesize that the degree of interference will relate to the time of sampling post-dose administration, with the *in vivo* trough drug level showing less impact Pre- and post-PLX038 infusion samples will be drawn to perform coagulation assays, including PT, PTT, thrombin time, reptilase time, fibrinogen, and lupus anticoagulant, using two different instrument analyzers and various reagents. *In vitro* studies using normal donor plasma will further investigate the interference. Normal donor samples will be spiked with varying concentrations of PLX038, PEG alone and SN-38. The resulting samples will be analyzed with coagulation assays shown in **Table 11**.  
Testing will be completed at NIH Department of Laboratory Medicine and Mayo Clinic Laboratories.  
| Test   | Instrument        | Assay                      | Location of   |
|--------|-------------------|----------------------------|---------------|
| PT/INR | Stago             | STA Neoplastine CI Plus 10 | NIH           |
| IL     | RecombiPlasTin 2g | MAYO                       |               |
| PTT    | Stago             | STA-PTT Automate 5         | NIH           |  
| Test                                                                                                                                 | Instrument            | Assay            | Location of  testing   |
|--------------------------------------------------------------------------------------------------------------------------------------|-----------------------|------------------|------------------------|
| STA-C.K. Prest 5                                                                                                                     | NIH                   |                  |                        |
| STA-Cephascreen 4                                                                                                                    | NIH                   |                  |                        |
| STA-Cephascreen 10                                                                                                                   | NIH                   |                  |                        |
| STA-STACLOT dRVV Screen 2                                                                                                            | NIH                   |                  |                        |
| STA-STACLOT dRVV Screen 5                                                                                                            | NIH                   |                  |                        |
| STA-STACLOT dRVV Confirm                                                                                                             | NIH                   |                  |                        |
| PTT-LA Screen                                                                                                                        | NIH                   |                  |                        |
| Staclot LA                                                                                                                           | NIH                   |                  |                        |
| Precision BioLogic CRYOcheck LA/LA sure                                                                                              | NIH                   |                  |                        |
| IL                                                                                                                                   | HemosIL Synth ASil    | MAYO             |                        |
| HemosIL SynthAFax                                                                                                                    | MAYO                  |                  |                        |
| HemosIL APTT-SP                                                                                                                      | MAYO                  |                  |                        |
| Thrombin Time                                                                                                                        | Stago                 | STA Thrombin 2   | NIH                    |
| IL                                                                                                                                   | HemosIL Thrombin Time | MAYO             |                        |
| Reptilase time                                                                                                                       | Stago                 | STA-Reptilase    | NIH                    |
| IL                                                                                                                                   | Reptilase time        | MAYO             |                        |
| Fibrinogen                                                                                                                           | Stago                 | STA Fibrinogen 5 | NIH                    |
| IL                                                                                                                                   | Fibrinogen C          | MAYO             |                        |
| Q.F.A. Thrombin                                                                                                                      | MAYO                  |                  |                        |
| Stago = Diagnostica Stago STA-R Evolution Analyzer. IL = Instrumentation Laboratory ACL Top  700Samples for Genetic/Genomic Analysis |                       |                  |                        |
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5.3.8 slfn11 expression

SLFN11 expression will be assessed by RNA sequencing and or IHC.
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5.3.9 rnaseq and whole exome

In order to address the exploratory goal of characterizing predictive biomarkers of response, genomic analysis including but not limited to RNAseq and whole exome sequencing of tumor tissue may be performed.
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5.3.10 management of results

Subjects will be contacted if a clinically actionable gene variant is discovered. Clinically actionable findings for the purpose of this study are defined as disorders appearing in the American College of Medical Genetics and Genomics recommendations for the return of incidental findings that is current at the time of primary analysis. (A list of current guidelines is maintained on the CCR intranet: https://ccrod.cancer.gov/confluence/display/CCRCRO/Incidental+Findings+Lists. Subjects will be contacted at that time with a request to provide a sample to be sent to a CLIA certified laboratory.