A Study of Pasritamig (JNJ-78278343) in Combination With Other Agents for Metastatic Prostate Cancer

Part 1: Number of Participants With Dose Limiting Toxicity (DLT)

Timeframe: Up to 21 days after first dose of combination agent

DLTs are specific adverse events and are defined as any of the following: high grade non-hematologic toxicity or hematologic toxicity.

Part 1 and Part 2: Number of Participants with Adverse Events (AEs) by Severity

Timeframe: Up to 2 years 11 months

An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study. Severity will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0 with the exception of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome events, which will be graded by American Society for Transplantation and Cellular Therapy (ASTCT) guidelines. Severity scale ranges from grade 1 (mild) to grade 5 (death). Grade 1= mild, Grade 2= moderate, Grade 3= severe, Grade 4= life-threatening and Grade 5= death related to adverse event.

Overall Response Rate (ORR)

Timeframe: Up to 2 years 11 months

ORR is defined as the percentage of participants who have a partial response (PR) or better without evidence of bone progression according to Prostate Cancer Working Group 3 (PCWG3) criteria.

Prostate Specific Antigen (PSA) Response Rate

Timeframe: Up to 2 years 11 months

PSA response rate is defined as the percentage of participants with a confirmed decline of PSA of 50 percent (%) or more from baseline.

Radiographic Progression-free Survival (rPFS)

Timeframe: Up to 2 years 11 months

rPFS is defined time from the date of first dose of pasritamig until the date of objective disease progression or death, whichever comes first.

Time to Response (TTR)

Timeframe: Up to 2 years 11 months

TTR is defined for the responders as the time from the date of first dose of to the date of first documented response that is subsequently confirmed.

Duration of Response (DOR)

Timeframe: Up to 2 years 11 months

DOR is defined for participants who achieved response (PR or better) as the time between the date of initial documentation of response (PR or better) to the date of first documented evidence of progressive disease, as defined in the PCWG3, or death due to any cause, whichever occurs first.

Part 2H Metastatic hormone-sensitive prostate cancer (mHSPC) Participants : Composite Progression-Free Survival (PFS)

Timeframe: Up to 2 years 11 months

Composite PFS is defined as time from start of treatment to the date of first occurrence of investigator determined disease progression (Response Evaluation Criteria in Solid Tumors \[RECIST\] or bone progression), pain, PSA progression, death or last disease assessment.