Safety, Pharmacokinetics, and Preliminary Efficacy of VIR-5500 (AMX-500) in Prostate Cancer

The study will be conducted in 4 parts and will commence with dose escalation of VIR-5500 as a monotherapy (Part 1), followed by combination escalation (Part 3a), monotherapy dose expansion (Part 2) and combination dose expansion (Part 4a). * Part 1 (Monotherapy Dose Escalation): Single-agent VIR-5500 dose escalation * Part 2 (Monotherapy Dose Expansion): Single-agent VIR-5500 dose expansion * Part 3 (Combination Dose Escalation): VIR-5500 plus another therapeutic agent dose escalation Part 3a (Combination Dose Escalation): VIR-5500 in combination with an androgen receptor signaling inhibitor (ARSI) * Part 4 (Combination Dose Expansion): VIR-5500 plus another therapeutic agent dose expansion Part 4a (Combination Dose Expansion): VIR-5500 in combination with an androgen receptor signaling inhibitor (ARSI)

Inclusion Criteria: Applicable to Parts 1 and 2 1. Have metastatic disease, defined by ≥ 1 metastatic lesion that is present on baseline computed tomography (CT), magnetic resonance imaging (MRI), or bone scan imaging 2. Have documented progressive mCRPC based on ≥ 1 of the criteria (per PCWG3) * PSA level ≥ 1 ng/mL that has increased on ≥ 2 successive occasions ≥ 1 week apart * Nodal or visceral progression as defined by RECIST v1.1 with PCWG3 modifications * Appearance of ≥ 2 new lesions in bone scan 3. Have been treated with ≥ 1 second-generation androgen-signaling inhibitor, including abiraterone, apalutamide, darolutamide, and/or enzalutamide 4. Have been treated with ≥ 1 prior taxane regimens (e.g., docetaxel, cabazitaxel) 5. Are deemed unsuitable for standard of care Applicable to Part 2, 3a and Part 4a, 1. Have metastatic CRPC, defined by ≥ 1 metastatic lesion that is present on baseline CT, MRI, or bone scan imaging that has documented progressive disease (PD) based on ≥ 1 of the following criteria (per PCWG3): * PSA level ≥ 1 ng/mL that has increased on ≥ 2 successive occasions ≥ 1 week apart * Nodal or visceral progression as defined by RECIST v1.1 with PCWG3 modifications * Appearance of ≥2 new lesions in bone scan 2. Participants with metastatic hormone sensitive prostate cancer (mHSPC) or with biochemical recurrent prostate cancer (BRPC) may also participate in select cohorts of this clinical trial. Exclusion Criteria: 1. Presence of dominant histopathological features representative of sarcomatoid, spindle cell, or neuroendocrine small cell components 2. Has acute or chronic infections 3. Has a concomitant medical or inflammatory condition that may increase the risk of toxicity to VIR-5500 (AMX-500), per the Investigator 4. Has lesions in proximity of vital organs 5. Has known active CNS metastases and/or carcinomatous meningitis The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.