A Study of Pasritamig Versus Placebo in Late Line Metastatic Castration-resistant Prostate Cancer (mCRPC) (KLK2-comPAS)

• Biological: Pasritamig
• Other: Placebo
• Drug: Best Supportive Care (BSC)

Inclusion Criteria

• Histologically confirmed adenocarcinomacancer arising from mucus-producing glands in organs of the prostate
• Metastatic castration-resistant prostate cancer (mCRPC): Disease that is metastatic either to bone, any lymph nodea small lump or mass of tissue in your body, or both without clear evidence of metastasiswhen the cancer has spread to other parts of the body, also known as mets to visceral organs at the time of screeningtesting for cancer or conditions that can lead to cancer before symptoms appear, also known as cancer screening
• PSA greater than or equal to (>=) 2 nanogram per milliliter (ng/mL) at screening
• In the opinion of the investigator, the next best treatment option is a clinical trial
• Participants should have had all life-prolonging therapies for which they are clinically eligible in the opinion of the investigator and to which they have access. Prior therapies could have been given in any disease setting (not limited to mCRPC). In particular, prior treatment specifications include receipt of the following:

Androgen-receptor pathway inhibitor (ARPI): Must have progressed on at least 1 ARPI and unlikely to benefit from retreatment with another ARPI

Taxanes: Should have received at least 2 previous taxane-based regimens. If a participant has received only 1 taxane regimen, the participant is eligible if:

1. Cabazitaxel is not available
2. The participant’s physician deems the participant unsuitable to receive a second taxane regimen due to toxicity riskthe possibility that something bad will happen or prior intolerance Note: a taxane-based regimen consists of at least 2 cycles of a taxane (either as a single agent or in combination with other therapies) administered within the same 2-month period.

Radioligand therapy: Should have been previously treated with at least 1 dosethe amount of medication taken of Prostate-specific membrane antigen (PSMA)-targeted lutetium radioligand therapy (eg, lutetium Lu-177 vipivotide tetraxetan), unless one of the following applies:

1. PSMA-targeted lutetium radioligand therapy is unavailable, not accessible, or not clinically indicated.
2. The participant’s physician deems the participant unsuitable to receive PSMA-targeted lutetium radioligand therapy.

Polyadenosine diphosphate-ribose polymerase inhibitors (PARPi): Should have been previously treated with PARPi, if the participant has a known germline or somatic BRCA mutation and treatment is available

• Prior orchiectomyremoval of one or both testicles, also known as orchidectomy or medical castration (receiving ongoing ADT with a GnRH analog [agonist or antagonist]) prior to the first dose of study treatment and must continue this therapy throughout the treatment phase
• Eastern Cooperative Oncologythe study, diagnosis and treatment of cancer Group (ECOG) performance status of 0 to 2
• Participants are eligible if they have the following values:

A) eGFR >= 30 milliliters per minute (mL/min) B) Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) less than or equal to (<=) 5 times the Upper Limit of Normal (ULN) C) Serum total bilirubin <= 3 * ULN D) Absolute neutrophil count (ANC) >= 1.0 *10^9/per liter (L) E) Hemoglobin >= 8.0 grams per deciliter (g/dL) F) Platelet count >= 75 * 109/L