TALAPRO-3

1. Male participants at least 18 years of age at screening. Refer to Appendix 4 for reproductive criteria for male participants.

2. Histologically or cytologically confirmed adenocarcinoma of the prostate without small cell or signet cell features. If the participant does not have a prior histological diagnosis, a baseline de novo biopsy must be used to confirm the diagnosis and may also be used to support biomarker analysis.

3. Confirmation of DDR gene mutation status by prospective or historical analysis (with sponsor pre-approval) of blood (liquid biopsy) and/or de novo or archival tumor tissue using FoundationOne Liquid CDx or FoundationOne CDx.

4. Provide tumor tissue for molecular profiling analysis (archived or fresh tumor tissue) when available.

5. Unless prohibited by local regulations or ethics committee decision, consent to a saliva sample collection for retrospective sequencing of the same DDR genes tested on tumor tissue and blood (liquid biopsy), or a subset thereof, and to serve as a germline control in identifying tumor mutations.

6. Surgically or medically castrated, with serum testosterone ≤ 50 ng/dL (≤ 1.73 nmol/L) at screening. Ongoing ADT with a GnRH agonist or antagonist for participants who have not undergone bilateral orchiectomy must be initiated at least 4 weeks before randomization and must continue throughout the study.

7. Metastatic prostate cancer documented by positive bone scan (for bone disease) or metastatic lesions on CT or MRI scan (for soft tissue). Participants whose disease spread is limited to regional pelvic lymph nodes are not eligible.

Note: a finding of superscan at baseline is not allowed.

8. Prior docetaxel therapy for mCSPC (up to 6 cycles) is allowed (must be completed 2 weeks prior to randomization and all toxicities from treatment have resolved).

9. Treatment with oestrogens, cyprotoerone acetate, or androgens is allowed until randomization.

10. Other prior therapy allowed for mCSPC; ≤ 6 months of ADT and ≤ 3 months of abiraterone + prednisone or enzalutamide if required prior to randomization.

11. Participant may have received palliative radiation or surgery for symptomatic control secondary to prostate cancer, which should have been completed at least 2 weeks prior to randomization.

12. ECOG performance status 0 or 1.

13. Adequate organ function within 28 days before the first study treatment on Cycle 1 Day 1, defined by the following:

• ANC > 1500/μL, platelets > 100,000/μL, or hemoglobin > 9 g/dL (may not have received growth factors or blood transfusions within 14 days before obtaining the haematology laboratory tests at screening).

• Total serum bilirubin < 1.5 × ULN (< 3 × ULN for participants with documented Gilbert syndrome or for whom indirect bilirubin concentrations suggest an extrahepatic source of elevation).

• AST or ALT < 2.5 × ULN (< 5 × ULN if liver function abnormalities are due to hepatic metastasis).

• Albumin > 2.8 g/dL.

• eGFR > 30 mL/min/1.73 m2 by the MDRD equation

14. Life expectancy ≥ 12 months as assessed by the investigator.

15. Able to swallow the study treatment and have no known intolerance to study treatments or excipients.

16. Sexually active participants that in the opinion of the investigator are capable of ejaculating, must agree to use a condom when having sex with a partner (female or male) from the time of the first dose of study treatment through 4 months after last dose of study treatment. Must also agree for female partner of childbearing potential to use an additional highly effective form of contraception from the time of the first dose of study treatment through 4 months after last dose of study treatment when having sex with a non-pregnant female partner of childbearing potential.

17. Must agree not to donate sperm from the first dose of study treatment to 4 months after the last dose of study treatment.

18. Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.

19. Capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. 

1. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behaviour or laboratory abnormality that may increase the risk of study participation or, in the investigator’s judgment, make the participant inappropriate for the study.

2. History of seizure or any condition (as assessed by investigator) that may predispose to seizure (eg, prior cortical stroke, significant brain trauma), including any history of loss of consciousness or transient ischemic attack within 12 months of randomization.

3. Major surgery (as defined by the investigator) within 2 weeks before randomization.

4. Known or suspected brain metastasis or active leptomeningeal disease.

5. Symptomatic or impending spinal cord compression or cauda equina syndrome.

6. Any history of MDS, AML, or prior malignancy except for the following:

• Carcinoma in situ or non-melanoma skin cancer.

• A cancer diagnosed and treated ≥ 3 years before randomization with no subsequent evidence of recurrence.

• American Joint Committee on Cancer Stage 0 or Stage 1 cancer that has a remote probability of recurrence in the opinion of the investigator and the sponsor.

7. In the opinion of the investigator, any clinically significant gastrointestinal disorder affecting absorption.

8. Clinically significant cardiovascular disease, including any of the following:

• Myocardial infarction or symptomatic cardiac ischemia within 6 months before randomization.

• Congestive heart failure New York Heart Association class III or IV.

• History of clinically significant ventricular arrhythmias (eg, sustained ventricular tachycardia, ventricular fibrillation, torsade de pointes) within 1 year before screening.

• History of Mobitz II second degree or third-degree heart block unless a permanent pacemaker is in place.

• Hypotension as indicated by systolic blood pressure <86 mm Hg at screening.

• Bradycardia as indicated by a heart rate of <45 beats per minute on the screening electrocardiogram.

• Uncontrolled hypertension as indicated by systolic blood pressure > 170 mm Hg or diastolic blood pressure > 105 mm Hg at screening. However, participants can be rescreened after adequate control of blood pressure is achieved.

9. Active infection including HBV, HCV, HIV, or COVID-19.

• Active COVID-19 infection detected by viral test or based on clinical diagnosis (as assessed by investigator). Asymptomatic participants with no active COVID-19 infection detected but positive antibody tests, indicating past infection are allowed.

10. Prior ADT in the adjuvant/neoadjuvant setting, where the completion of ADT was more than 12 months prior to randomization and the total duration of ADT did not exceed 36 months.

11. Participant received treatment with systemic glucocorticoids greater than the equivalent of 10 mg per day of prednisone within 4 weeks prior to randomization, intended for the treatment of prostate cancer.

12. Any previous treatment with DNA-damaging cytotoxic chemotherapy (ie, platinum-based therapy) within 5 years prior to randomization, except for indications other than prostate cancer.

13. Prior treatment with a PARPi.

14. Prior treatment in any setting with NHT, except for enzalutamide or abiraterone/prednisone.

15. Current use of potent P-gp inhibitors within 7 days prior to randomization. For a list of potent P-gp inhibitors, and other medications which are exclusionary because of interaction with either talazoparib or enzalutamide, refer to Section 6.5.

16. Treatment with any investigational agent within 4 weeks before randomization.

17. Baseline 12-lead ECG that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results (eg, QTc interval > 450 msec, complete LBBB, signs of an acute or indeterminate age myocardial infarction, STT interval changes suggestive of myocardial ischemia, second or third degree AV block, or serious bradyarrhythmias or tachyarrhythmias). If the baseline uncorrected QT interval is > 450 msec, this interval should be rate-corrected using the Fridericia method and the resulting QTcF should be used for decision making and reporting. If QTc exceeds 450 msec, or QRS exceeds 120 msec, the ECG should be repeated 2 more times and the average of the 3 QTc or QRS values should be used to determine the participant’s eligibility. Computer-interpreted ECGs should be overread by a physician experienced in reading ECGs before excluding participants.

18. Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members. 

Research Nurse: Catherine Walmsley (x8475) Catherine.Walmsley@lthtr.nhs.uk

Administrator: Aaisha Khan (x8475)