This phase II trial tests whether pegylated SN-38 conjugate PLX038 (PLX038) works to shrink tumors in patients with ovarian, primary peritoneal, and fallopian tube cancers that has spread from where it first started (primary site) to other places in the body (metastatic). PLX038 may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth.

PRIMARY OBJECTIVE:

I. To estimate the overall tumor response rate (overall response rate [ORR], that is, complete response [CR] + partial response [PR], according to Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST v1.1] of PLX038 in the setting of metastatic platinum resistant high grade serous ovarian cancer.

SECONDARY OBJECTIVES:

I. To estimate the progression-free survival and overall survival of treatment with PLX038.

II. To describe and assess tolerability of PLX038. III. Measure PLX038 induced tumor TOP1-deoxyribonucleic acid (DNA) covalent complexes (TOP1cc) in pretreatment and Cycle 1 Day 8 biopsies to confirm persistent stabilization of TOP1cc and evaluate association with tumor response rate.

CORRELATIVE RESEARCH:

I. Measure TOP1cc in circulating tumor cells and evaluate association with TOP1cc in tumor tissue and tumor response rate.

II. Assess homologous repair status and association with tumor response. III. Assess expression of SN-38 transports by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and association with tumor response.

IV. Assess pharmacokinetics of SN-38 and SN-38G as well as their association with gastrointestinal (GI) toxicity.

V. Assess the gut microbiota and evaluate association with GI toxicity profile.

OUTLINE:

Patients receive PLX038 intravenously (IV) over 1 hour on day 1 of each cycle. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity. Patients also undergo computed tomography (CT), biopsy, as well as blood and stool sample collection during screening and on the trial.

After completion of study treatment, patients are followed up at 30 days and every 6 months for up to 5 years.

Inclusion Criteria:

• Age >= 18 years NOTE: Because no dosing or adverse event data are currently available on the use of PLX038 in patients < 18 years of age, children are excluded from this study, but will be eligible for future pediatric trials
• Histological confirmed high grade serous ovarian cancer consistent with ovarian, fallopian tube, or primary peritoneal carcinoma (NOTE: Any of these diseases are referred to in this protocol as "ovarian cancer")
• Recurrent high grade serous ovarian cancer that was initially platinum sensitive (i.e., had at least one platinum-free interval of at least 6 months before progression) is now platinum resistant
• No more than one prior line of therapy for platinum resistant disease. NOTE: Prior poly adenosine diphosphate-ribose polymerase (PARP) inhibitor therapy is allowed
• Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1
• Disease that is amenable to two biopsies
• Life expectancy greater >= 12 weeks
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1 or 2
• Hemoglobin >= 8.0 g/dL (obtained =< 28 days prior to registration)
• Absolute neutrophil count (ANC) >= 1500/mm^3 (obtained =< 28 days prior to registration)
• Platelet count >= 100,000/mm^3 (obtained =< 28 days prior to registration)
• Total bilirubin >= 1.5 x upper limit of normal (ULN) (obtained =< 28 days prior to registration)
• Alanine aminotransferase (ALT) and aspartate transaminase (AST) =< 3 x ULN (=< 5 x ULN for patients with liver involvement) (obtained =< 28 days prior to registration)
• Calculated creatinine clearance >= 45 ml/min using the Cockcroft-Gault formula (obtained =< 28 days prior to registration)
• Negative pregnancy test done =< 7 days prior to registration, for persons of childbearing potential only
• Provide written informed consent
• Willing to return to enrolling institution for follow-up (during the Active Monitoring Phase of the study)
• Willingness to provide mandatory blood specimens for correlative research
• Willingness to provide mandatory tissue specimens for correlative research

Exclusion Criteria:

• Any of the following because this study involves an agent that has known genotoxic, mutagenic and teratogenic effects:

  • Pregnant persons
  • Nursing persons
  • Persons of childbearing potential who are unwilling to employ adequate contraception

• Histology other than high grade serous carcinoma

• Prior treatment restrictions

  • Chemotherapy =< 4 weeks prior to registration
  • Immunotherapy =< 4 weeks prior to registration
  • Radiotherapy =< 4 weeks prior to registration
  • Any other investigational therapy =< 4 weeks prior to registration

• History of prior or concurrent malignancy =< 2 years prior to registration

  • Exceptions: If natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen

• Uncontrolled intercurrent illness including, but not limited to:

  • Myocardial infarction within 6 months of study entry
  • New York Heart Association (NYHA) class III or IV heart failure
  • Uncontrolled dysrhythmias or poorly controlled angina
  • History of serious ventricular arrhythmia (ventricular tachycardia [VT] or ventricular fibrillation [VF]) and/or factors that predispose to arrhythmia (e.g., heart failure, hypokalemia, family history of long QT syndrome)

• Known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, Exception: Patients should have a clinical risk assessment of cardiac function using the New York Heart Association functional classification. To be eligible for this trial, patients should be class IIB or better Exception: Patients who have received prior doxorubicin (Doxil) are eligible if asymptomatic with QTc =< 480msec (Fridericia) and NYHA class IIB or better

• Known human immunodeficiency virus (HIV) Exception: Patients on effective anti-retroviral therapy with undetectable viral load =< 6 months prior to registration are eligible for this trial

• Known hepatitis

  • Exception: For patients with evidence of chronic hepatitis B virus infection the HepB viral load must be undetectable on suppressive therapy, if indicated, to be eligible
  • Exception: Patients with a history of hepatitis C virus infection must have been treated and cured. Patients with HCV infection who are currently on treatment are eligible if they have an undetectable HCV viral load

• Receiving any other investigational agent

• History of clinically significant gastrointestinal bleeding, colitis, or gastrointestinal perforation

• Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens

• Requirement for anticoagulation treatment that increases international normalized ratio (INR) or activated partial thromboplastin time (APTT) above the normal range (Exceptions: low dose deep vein thrombosis [DVT] or line prophylaxis allowed)

• Known central nervous system (CNS) disease Exception: Patients with treated brain metastases are eligible if follow-up brain imaging after CNS directed therapy shows no evidence of progression. Patients with new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determined that immediate CNS specific treatment is not required and is unlikely to be required during the 1st cycle of therapy

• Known Gilbert's syndrome or homozygous for the UGT1A1*28 variant allele or other relevant alleles with severely reduced UGT1A1 activity

• Patients who require treatment with UGT1A1 inhibitors during the planned period of investigational treatment with PLX038

Staining will be read independently by two individuals blinded to treatment, who will score each sample for the percentage of cells that are positive for >8 nucleoplasmic TOP1ccs.