The main objective of the trial is to evaluate the safety and tolerability of xaluritamig in combination with darolutamide or abiraterone.

Inclusion Criteria:

• Participants must have histological, pathological, and/or cytological confirmation of adenocarcinoma of the prostate. Mixed histologies (eg, adenocarcinoma with neuroendocrine component) are not permitted.

• Participants must have at the time of diagnosis:

  • De novo (synchronous) mHSPC, defined as metastatic disease with no prior diagnosis of localized prostate cancer, AND started ADT (LHRH agonist/antagonist or orchiectomy) with or without ARPI (defined as abiraterone OR darolutamide) as SOC, first treatment with ADT should be no longer than 12 weeks before screening. Prior docetaxel treatment is not permitted.

• Participants must have at the time of diagnosis:

  • High-volume metastatic disease defined as presence of visceral metastasis or metastases, and/or ≥ 4 bone metastases with at least one outside of the vertebral column and pelvis.

• Documented metastatic disease either by a positive bone scan, or for soft tissue or visceral metastases, either by contrast enhanced abdominal/pelvic/chest computed tomography (CT) or magnetic resonance imaging (MRI) scan.

• No documented PSA progression following the initial PSA nadir after starting ADT.

Exclusion Criteria:

• Prior history of central nervous system (CNS) metastases. Note: Participants with asymptomatic and clinically stable dural metastases are eligible.
• Unresolved toxicities from prior anti-tumor therapy (excluding those related to ongoing ADT and ARPI) not having resolved to Common Terminology Criteria for Adverse events (CTCAE) version 5.0 grade 1 or baseline, with the exception of alopecia or toxicities that are stable and well-controlled AND there is an agreement to allow inclusion by both the investigator and the sponsor.
• Autoimmune disease requiring systemic immunosuppression within the past 2 years.
• Participant with symptoms and/or clinical signs and/or radiographic signs that indicate an acute and/or uncontrolled active or systemic infection within 7 days prior to the first dose of study treatment.
• Prior six-transmembrane epithelial antigen of the prostate 1 (STEAP1)-targeted therapy.
• Prior radioligand therapy (RLT), poly-adenosine diphosphate ribose polymerase (PARP) inhibitor, cytotoxic chemotherapy, aminoglutethimide or ketoconazole for prostate cancer, or any prior systemic biologic therapy, including immunotherapy for prostate cancer.
• Prior enzalutamide or apalutamide within 15 days prior to enrolment.
• Requirement for chronic systemic corticosteroid therapy (prednisone dose greater than 10 mg per day or local equivalent) or any other immunosuppressive therapies (including anti TNFα therapies) unless stopped (with adequate tapering) within 7 days prior to dosing.
• Prior radiotherapy to all metastatic sites of disease. Radiotherapy to some sites of metastatic disease for palliation will be permitted.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request.

Data sharing requests relating to this trial will be considered beginning 18 months after the trial has ended and either 1) the product and indication have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this trial.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen trial/trials in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors. If not approved, a Data Sharing Independent Review Panel will arbitrate and make the final decision. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.