PLX2853 in Combination With Abiraterone Acetate and Prednisone and in Combination With Olaparib in Subjects With Metastatic Castration-Resistant Prostate Cancer (mCRPC)

Phase 1

Terminated

Interventions: Drug: PLX2853 20 mg
Drug: Abiraterone acetate
Drug: Olaparib
Drug: PLX2853 40 mg
Drug: Prednisone
Drug: PLX2853 80 mg

Brief Summary: The purpose of this research study is to evaluate safety, pharmacokinetics, pharmacodynamics and preliminary efficacy of the investigational drug PLX2853 in subjects with Metastatic Castration-Resistant Prostate Cancer (mCRPC)

Recruitment & Eligibility

Inclusion Criteria

Age ≥18 years at the time of signing informed consent.
Histologically confirmed adenocarcinoma of the prostate with tumor tissue available for molecular analyses.
Eastern Cooperative Oncology Group Performance Status 0 to 1.
Adequate organ function as demonstrated following laboratory values.
Fertile male subjects with female sexual partners must agree to use a highly effective method of birth control during the study and for 90 days after the last dose of study drug.
Except as specified above for organ function, all drug-related toxicity from previous cancer therapy (including ongoing Abiraterone Acetate + Prednisone therapy if applicable) must be resolved (to Grade ≤1 or baseline per National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0) prior to study treatment administration (Grade 2: alopecia, hot flashes, decreased libido, or neuropathy is allowed).
Willingness and ability to provide written informed consent prior to any study-related procedures and to comply with all study requirements.

Exclusion Criteria

Prior exposure to a bromodomain inhibitor.
History of autoimmune hemolytic anemia or autoimmune thrombocytopenia.
Clinically significant cardiac disease.
Inability to take oral medication or significant nausea and vomiting, malabsorption, or significant small bowel resection that, in the opinion of the Investigator, would preclude adequate absorption.
Active known second malignancy with the exception of any of the following:
- Adequately treated basal cell carcinoma or squamous cell carcinoma of the skin.
- Adequately treated Stage I cancer from which the subject is currently in remission and has been in remission for ≥2 years.
- Any other cancer from which the subject has been disease-free for ≥3 years.
Subject is participating in any other therapeutic clinical study (observational or registry studies are allowed).
Presence of any other medical, psychological, familial, sociological, or geographic condition potentially hampering compliance with the study protocol or would interfere with the study endpoints or the subject's ability to participate in the study in the judgment of the Investigator.
Receipt of any anti-cancer therapy prior to Cycle 1 Day 1 with less than protocol defined wash-out with the exception of Abiraterone Acetate (for subjects enrolling into Abiraterone Acetate Combination) and GnRH therapy.

Arm && Interventions

Group	Intervention	Description
Phase 1b PLX2853 (20 mg) + Olaparib	PLX2853 20 mg	Phase 1b dose escalation
Phase 1b PLX2853 (40 mg) + Abiraterone Acetate + Prednisone	Abiraterone acetate	Phase 1b dose escalation
Phase 1b PLX2853 (40 mg) + Olaparib	Olaparib	Phase 1b dose escalation
Phase 1b PLX2853 (40 mg) + Olaparib	PLX2853 40 mg	Phase 1b dose escalation
Phase 1b PLX2853 (20 mg) + Olaparib	Olaparib	Phase 1b dose escalation
Phase 1b PLX2853 (40 mg) + Abiraterone Acetate + Prednisone	Prednisone	Phase 1b dose escalation
Phase 1b PLX2853 (40 mg) + Abiraterone Acetate + Prednisone	PLX2853 40 mg	Phase 1b dose escalation
Phase 1b PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	Abiraterone acetate	Phase 1b dose escalation
Phase 1b PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	Prednisone	Phase 1b dose escalation
Phase 2a PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	Abiraterone acetate	Phase 2a dose expansion
Phase 1b PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	PLX2853 80 mg	Phase 1b dose escalation
Phase 2a PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	Prednisone	Phase 2a dose expansion
Phase 2a PLX2853 (80 mg) + Abiraterone Acetate + Prednisone	PLX2853 80 mg	Phase 2a dose expansion

Primary Outcome Measures

Name	Time	Method
Phase 1b (Both Arms): Incidence of TEAEs That Are Related to Treatment	From time of first dose of PLX2853 and combination agent(s) until 30 days from end of treatment (an average of 103 days)	Treatment-emergent adverse events are those reported after study drug has been administered.
Determination of Maximum Tolerated Dose	From time of first dose of PLX2853 and combination agent(s) through completion of Cycle 1 (21 days)	To be evaluated in both PLX2853 + AA + pred and PLX2853 + olap group; If DLTs observed in 2 or more subjects the dose will be considered intolerable and MTD will have been reached.
Number of Participants With Dose-Limiting Toxicities	From time of first dose of PLX2853 and combination agent(s) through completion of Cycle 1 (21 days)	Dose limiting toxicity defined as clinically significant adverse events or laboratory abnormalities occurring during first cycle of study drug administration that are possibly related to study drug and that meet specific criteria defined in the protocol

Secondary Outcome Measures

Name	Time	Method

Locations (8): University of Chicago
🇺🇸
Chicago, Illinois, United States
Sarah Cannon Research Institute
🇬🇧
London, United Kingdom
Carolina Urologic Research Center
🇺🇸
Myrtle Beach, South Carolina, United States
Columbia University Medical Center
🇺🇸
New York, New York, United States
Virginia Cancer Specialist
🇺🇸
Fairfax, Virginia, United States
Karmanos Cancer Institute
🇺🇸
Detroit, Michigan, United States
Tennessee Oncology/ Sarah Cannon
🇺🇸
Nashville, Tennessee, United States
University of Wisconsin
🇺🇸
Madison, Wisconsin, United States