Study Comparing AAA817+ARPI Versus Standard of Care in Adult Participants With PSMA-positive mCRPC

Key Inclusion Criteria:

• Signed informed consent must be obtained prior to participation in the study.

• Participants must be adults ≥ 18 years of age.

• Participants must have an ECOG performance status of 0 to 2.

• Participants must have histological, and/or cytological confirmation ofadenocarcinoma of the prostate. Participants with mixed histology (neuroendocrine)are not eligible.

• Participants who have received taxane-based chemotherapy in mHSPC setting areeligible if they are deemed appropriate for chemotherapy, ARPI change or AAA617 asthe next line of therapy in the opinion of the Investigator. Note: Participants whohave received taxane-based chemotherapy for mCRPC are excluded.

• Participants must not have received taxane-based chemotherapy in mCRPC setting (allowed in mHSPC setting).

• Participants must have PSMA-PET positive disease using a PSMA imaging agent that isapproved as per protocol.

• Participant must have been diagnosed with mCRPC with documented progressive diseasewhile on treatment with ARPI in mHSPC or earlier setting as their last treatment (and did not progress on more than one ARPI).

• Participants with deleterious or suspected deleterious germline or somatichomologous recombination repair (HRR) gene-mutated metastaticcastration-resistant prostate cancer, as per local testing, may be enrolled ifthey had prior exposure to PARPi.

Key Exclusion Criteria:

• Previous anti-cancer treatment with any approved or investigationalradiopharmaceuticals (for example, [177Lu]Lu-PSMA, [177Lu]-DOTA, or Radium- 223.)

• Previous treatment with any external beam radiotherapy including hemi-body radiationwithin 6 weeks of randomization (within 2 weeks for radiotherapy of localizedmetastases).

• Any prior PARP inhibitor or other systemic anticancer therapy administered formetastatic castration-resistant prostate cancer (mCRPC). Any other approved orinvestigational systemic therapy (including chemotherapy, immunotherapy,biologics, or monoclonal antibodies) is prohibited within 28 days or 5half-lives (whichever is shorter) before randomization.

Note: Prior ARPI administered in the mHSPC setting or earlier may continue until C1D1.

Other protocol-defined inclusion/exclusion criteria may apply.