A Study of Vobramitamab Duocarmazine in Participants With Metastatic Castration Resistant Prostate Cancer and Other Solid Tumors

Inclusion Criteria:

• Part 1 only: Histologically confirmed adenocarcinoma of the prostate withoutevidence of neuroendocrine differentiation, signet cell, or small cell features.

• Part 2 only: Histologically confirmed SCC or the anus, melanoma, HNSCC, squamousNSCLC, or SCLC.

• Part 1 only: Received 1 prior ARAT for metastatic or non-metastatic,castration-sensitive or castration-resistant prostate cancer. A second ARAT regimenof <60 days used as bridging to lutetium-177 is permitted. Up to 3 total prior linesof therapy for mCRPC are permitted..

• Part 2 only: At least 1 prior line of systemic therapy for unresectable ormetastatic disease and no more than 2 prior lines of cytotoxic chemotherapy.Participants with HNSCC or melanoma must have received prior PD-1 or PD-L1 inhibitorfor advanced or metastatic disease.

• All participants must have ≥ 1 metastatic lesion, according to RECIST 1.1 or PCWG3criteria, that is present on magnetic resonance imaging (MRI), computed tomography (CT), or bone scan obtained ≤ 28 days prior to initiation of study treatment.

• All participants must have tumor progression, according to disease-specificcriteria, following their most recent anti-cancer therapy.

• All participants must have and available archival or formalin-fixedparaffin-embedded (FFPE) tumor tissue sample for participants with metastasis tointernal organs

• All participants have acceptable physical condition and laboratory values.

• All participants of childbearing potential must agree to use highly effectivemethods of birth control.

• All participants must not be pregnant, planning to be pregnant, or breastfeeding.

Exclusion Criteria:

• Any underlying medical or psychiatric condition impairing participant's ability toreceive, tolerate, or comply with the planned treatment or study procedures.

• Part 1 only: Received >1 prior taxane-containing regimen for prostate cancer. Asecond taxane regimen of <60 days used as bridging for lutetium-177 is permitted.

• Part 1 only: Received >3 total prior therapies for mCRPC

• Part 1 only: Participants with known BRCA or ATM mutation (germline or somatic) arenot eligible unless they received prior treatment with a PARP inhibitor whereavailable, indicated and tolerated.

• Another hematologic or solid tumor ≥ stage 1 malignancy that completed surgery, lastdose of radiotherapy, or last dose of systemic anti-cancer therapy ≤ 2 years fromfirst dose of study treatment. Participants who had curative therapy fornon-melanomatous skin cancer or for localized malignancy are eligible.

• Untreated, symptomatic central nervous system (CNS) metastasis.

• Prior treatment with any B7-H3 targeted agent for cancer,

• Contradictions to the use of corticosteroid treatment

• Prior stem cell, tissue, or solid organ transplant.

• Part 1 only: Use of products that have published anti-prostate cancer activity orare known to decrease PSA.