Background: This detailed analysis further characterizes the safety profile of talazoparib plus enzalutamide in the ongoing randomized, phase III TALAPRO-2 study in patients with metastatic castration-resistant prostate cancer (mCRPC). In both the all-comers and homologous recombination repair (HRR)-deficient populations, talazoparib plus enzalutamide significantly improved radiographic progression-free survival compared with placebo plus enzalutamide., Methods: The talazoparib plus enzalutamide safety populations in TALAPRO-2 included 398 patients from cohort 1 (all-comers, unselected for HRR gene alterations) and 198 patients from the combined HRR-deficient population (patients from the all-comers population with HRR gene alterations plus subsequently enrolled patients with HRR gene alterations; cohort 2). Patients received talazoparib 0.5 mg (0.35 mg, moderate renal impairment) and enzalutamide 160 mg once daily. Safety analyses evaluated common treatment-emergent adverse events (TEAE), their type, severity, timing, seriousness, and relationship to study treatment., Results: In the all-comers (n = 398) and HRR-deficient populations (n = 198), all-cause grade 3/4 (G3/4) TEAEs with talazoparib plus enzalutamide were reported in 71.9 % and 66.2 % of patients, respectively. Most common G3/4 hematologic TEAEs were anemia (46.7 % and 40.9 %, respectively), neutropenia (18.3 % and 18.7 %), and thrombocytopenia (7.3 % and 7.1 %). Median time to event was 3.3 and 3.3 months for G3/4 anemia, 2.3 and 2.3 months for G3/4 neutropenia, and 2.3 and 1.5 months for G3/4 thrombocytopenia. Maximum hemoglobin reduction occurred after 13 and 15 weeks of treatment. 18.8 % and 10.1 % of patients discontinued talazoparib. TEAEs were managed with dose interruption (62.1 % and 57.6 %), reduction (52.8 % and 52.0 %), hematologic supportive care (13.1 % and 10.6 %), and packed red blood cell transfusions (39.2 % and 35.9 %)., Conclusion: Talazoparib plus enzalutamide had a generally manageable safety profile in patients with mCRPC within the all-comers and the HRR-deficient populations., Gov Identifier: NCT03395197., Competing Interests: Declaration of Competing Interest Arun A. Azad reports honoraria from Aculeus Therapeutics, Amgen, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Daiichi Sankyo, Ipsen, Janssen, Merck Serono, Merck Sharp & Dohme, Novartis, Noxopharm, Pfizer, Sanofi, Telix Pharmaceuticals, and Tolmar; consulting fees from Aculeus Therapeutics, Astellas Pharma, Janssen, and Novartis; participation on advisory boards for Amgen, Arvinas, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Daiichi Sankyo, Ipsen, Janssen, Merck Serono, Merck Sharp & Dohme, Novartis, Noxopharm, Pfizer, Sanofi, Telix, and Tolmar; participation on a data safety monitoring board for OncoSec; research funding (institution unless stated otherwise) from Aptevo Therapeutics, Astellas Pharma (investigator), AstraZeneca (investigator), Bionomics, Bristol Myers Squibb, Exelixis, Gilead Sciences, GlaxoSmithKline, Hinova Pharmaceuticals, Ipsen, Janssen, Lilly, MedImmune, Merck Serono (investigator), Merck Serono (institutional), MSD, Novartis, Pfizer, Sanofi, and Synthorx; and travel, accommodations, and/or expenses from Amgen, Astellas Pharma, Bayer, Hinova Pharmaceuticals, Janssen, Merck Serono, Novartis, Pfizer, and Tolmar; and support for medical writing services from Astellas Pharma, Exelixis, and Pfizer; he is Chair of the Urologic Oncology Group for the Clinical Oncology Society of Australia, and Chair of the Translational Research Subcommittee and on the Scientific Advisory Committee for the ANZUP Cancer Trials Group. Karim Fizazi reports honoraria (institution) for participation in advisory boards and talks from Advanced Accelerator Applications/Novartis, Amgen, Astellas Pharma, AstraZeneca, Bayer, Clovis Oncology, Daiichi Sankyo, Janssen, MSD, Novartis, Pfizer, and Sanofi; and honoraria (personal) for participation in advisory boards from Arvinas, CureVac, MacroGenics, and Orion. Nobuaki Matsubara reports honoraria (personal) from Sanofi; research funding (institution) from Amgen, Astellas Pharma, AstraZeneca, Bayer, Chugai Pharma, Eisai, Janssen, Lilly, MSD, Pfizer, PRA Health Science, Roche, Seagen, Taiho, and Takeda; and travel, accommodations, and/or expenses (personal) from Pfizer. Fred Saad reports a consulting or advisory role for AbbVie, Advanced Accelerator Applications, Astellas Pharma, AstraZeneca/MedImmune, Bayer, Janssen Oncology, Knight Therapeutics, Myovant Sciences, Novartis, Pfizer, and Sanofi; honoraria from AbbVie, Advanced Accelerator Applications, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Janssen Oncology, Knight Therapeutics, Merck, Myovant Sciences, Novartis, Pfizer, and Sanofi; and research funding to their institution from Advanced Accelerator Applications, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Janssen Oncology, Merck, Novartis, Pfizer, and Sanofi. Ugo De Giorgi reports a consulting or advisory role for Amgen, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Dompé Farmaceutici, Eisai, Ipsen, Janssen, Merck KGaA, MSD, Novartis, and Pfizer; research funding (institution) from AstraZeneca, Roche, and Sanofi; and travel, accommodations, and/or expenses from Ipsen and Pfizer. Jae Young Joung declares no competing interests. Peter C. C. Fong reports a consulting or advisory role for MSD and travel, accommodations, and/or expenses from Pfizer. Robert J. Jones reports honoraria from Astellas Pharma, Bayer, Bristol Myers Squibb, Gilead Sciences, Ipsen, Janssen, Merck Serono, MSD, Pfizer, and Roche; a consulting or advisory role for Astellas Pharma, Bayer, Bristol Myers Squibb, Ipsen, Janssen, Merck Serono, MSD, Novartis, Pfizer, and Roche; research funding from Astellas Pharma, Bayer, Clovis Oncology, Exelixis, and Roche; and travel, accommodations, and/or expenses from Bayer and Janssen. Stefanie Zschäbitz reports payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, or educational events from Amgen (personal and institution), Astellas Pharma (personal and institution), Bayer (personal and institution), Bristol Myers Squibb (personal and institution), Eisai (personal), Gilead Sciences (personal), Janssen (personal), Merck Serono (personal and institution), MSD (institution), Novartis (personal), and Pfizer (personal and institution); participation on a data safety monitoring board or advisory board for Amgen (personal and institution), Bayer (personal and institution), Bristol Myers Squibb (institution), Eisai (personal), Gilead Sciences (personal), Ipsen (personal), Janssen (personal), Merck Serono (personal and institution), MSD (institution), Novartis (personal), and Pfizer (institution); research funding (institution) from Eisai; and travel, accommodations, and/or expenses from Amgen, Astellas Pharma, AstraZeneca, Bayer, Ipsen, Janssen, Merck Serono, MSD, and Pfizer. Jan Oldenburg reports payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, or educational events from Astellas Pharma, AstraZeneca, Bayer, BMS Norway, Eisai, Ipsen, Janssen-Cilag, Merck, and Roche; participation on a data safety monitoring board or advisory board for Astellas Pharma, AstraZeneca, Bayer, BMS, Eisai, Ipsen, Janssen-Cilag, Merck, and Roche; and travel, accommodations, and/or expenses from Astellas Pharma. Neal D. Shore reports a consulting or advisory role for AbbVie, Alessa Therapeutics, Akido, Amgen, Arquer, Asieris, Astellas Pharma, AstraZeneca, Bayer, Boston Scientific, Bristol Myers Squibb, CG Oncology, Clarity Pharmaceuticals, Clovis Oncology, Dendreon, Exact Imaging, Exact Sciences, FerGene, Ferring, FIZE Medical, Foundation Medicine, GenesisCare, Genentech, Guardant Health, ImmunityBio, Incyte, Invitae, Janssen, Lantheus, Lilly, Mdxhealth, Merck, Minomic, Myovant Sciences, Myriad Genetics, Nymox, Pacific Edge Biotechnology, Pfizer, Photocure, PlatformQ, ProFound, Promaxo, Propella Therapeutics, Protara, Sanofi, Sesen Bio, Specialty Networks, Telix Pharmaceuticals, Tolmar, UroGen Pharma, Vaxiion, and Vessi; providing expert testimony for Ferring; and leadership or other fiduciary role in other board, society, committee, or advocacy group with Photocure. Curtis Dunshee reports participation on advisory boards for Astellas Pharma, Bayer, Janssen, and Pfizer; and research funding from AstraZeneca, Bayer, Dendreon, Hengrui Pharmaceuticals, Janssen, Laekna Therapeutics, Myovant Sciences, and Pfizer. Joan Carles reports a consulting or advisory role for Advanced Accelerator Applications/Novartis, Astellas Pharma, AstraZeneca, Bayer, Bristol Myers Squibb, Ipsen, Johnson & Johnson, MSD Oncology, Pfizer, Roche, and Sanofi; participation in speakers’ bureaus for Astellas Pharma, Bayer, and Johnson & Johnson; research funding (institution) from AB Science, Aragon Pharmaceuticals, AROG Pharmaceuticals, Astellas Pharma, AstraZeneca AB, AVEO Pharmaceuticals, Bayer AG, Blueprint Medicines, BN ImmunoTherapeutics, Boehringer Ingelheim España SA, Bristol Myers Squibb International Corporation, Clovis Oncology, Cougar Biotechnology, Deciphera, Exelixis, Genentech, GlaxoSmithKline, Incyte, Janssen-Cilag International NV, Karyopharm Therapeutics, Laboratoires Leurquin Mediolanum, Lilly, MedImmune, Millennium Pharmaceuticals, Nanobiotix, Novartis Farmacéutica SA, Pfizer, Puma Biotechnology, Roche, Sanofi Aventis GmbH, SFJ Pharmaceuticals Group, and Teva; and travel, accommodations, and/or expenses from AstraZeneca, BMS, Ipsen, and Roche. Andre P. Fay reports honoraria from Astellas Pharma, AstraZeneca, Bristol Myers Squibb, Ipsen, Janssen, MSD, Novartis, Pfizer, and Roche; a consulting or advisory role for Bayer, Ipsen, Janssen, MSD, Novartis, Pfizer, and Roche; stock or stock options in Brazilian Information Oncology; and research funding from AstraZeneca, Bristol Myers Squibb, CAPES – CNPq, Foundation Medicine, Ipsen, MSD, and Roche; and travel, accommodations and/or expenses from Astellas Pharma, AstraZeneca, BMS, Ipsen, Janssen, MSD, Novartis, Pfizer, and Roche. Xun Lin, Liza DeAnnuntis, and Michael A. Zielinski are employees of Pfizer and may hold Pfizer stock/stock options. Nicola Di Santo is a former employee of Pfizer and may hold Pfizer stock/stock options. Neeraj Agarwal (lifetime disclosures): No personal COIs since April 15, 2021. Consultancy to Astellas Pharma, AstraZeneca, AVEO Pharmaceuticals, Bayer, Bristol Myers Squibb, Calithera, Clovis, Eisai, Eli Lilly, EMD Serono, Exelixis, Foundation Medicine, Genentech, Gilead Sciences, Janssen, Merck, MEI Pharma, Nektar, Novartis, Pfizer, Pharmacyclics, and Seattle Genetics. Research funding to institution (lifetime): Arvinas, Astellas Pharma, AstraZeneca, Bavarian Nordic, Bayer, Bristol Myers Squibb, Calithera, Celldex, Clovis, CRISPR, Eisai, Eli Lilly, EMD Serono, Exelixis, Genentech, Gilead Sciences, GlaxoSmithKline, Immunomedics, Janssen, Lava, Medivation, Merck, Nektar, Neoleukin, NewLink Genetics, Novartis, ORIC, Pfizer, Prometheus, Rexahn, Roche, Sanofi, Seattle Genetics, Takeda, Telix, and TRACON., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)