MK-2400-01A Substudy: A Phase 1/2, Open-label Umbrella Substudy of MK-2400-U01 Master Protocol to Evaluate the Safety and Efficacy of Ifinatamab Deruxtecan-based Treatment Combinations or Ifinatamab Deruxtecan Alone in Participants With Metastatic Castration-resistant Prostate Cancer (mCRPC) (IDeate-Prostate02)

Primary

• Efficacy Phase: Number of Participants Who Experience One or More Dose-Limiting Toxicities (DLTs) - Combination Arms Only

  The following events if considered drug related by the Investigator, will be considered a DLT: Grade 4 nonhematologic toxicity (not based on laboratory value); Grade 4 hematologic toxicity lasting ≥7 days, except thrombocytopenia; Grade 4 thrombocytopenia of any duration; Grade 3 thrombocytopenia associated with clinically significant bleeding; Nonhematologic AEs ≥Grade 3 with exceptions; Grade 3 or Grade 4 non-hematologic laboratory values if requires medical intervention, leads to hospitalization, persists for \>1 week, or results in a Drug-induced Liver Injury with exceptions; Grade 3 or 4 febrile neutropenia; Study intervention - related toxicities that lead to discontinuation of study treatment during Cycle 1; Prolonged delay (\>2 weeks) in initiating Cycles 2 due to treatment-related toxicity; Missing \>25% of study intervention doses as a result of treatment-related AE during Cycle 1; Grade 5 toxicity.

  Time frame: Up to approximately 21 days

• Efficacy Phase: Number of Participants Who Experienced an Adverse Event (AE)

  An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

  Time frame: Up to approximately 54 months

• Efficacy Phase: Number of Participants Who Discontinued Study Intervention Due to an AE

  An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

  Time frame: Up to approximately 24 months

• Efficacy Phase: Prostate-Specific Antigen (PSA) response rate

  PSA response is defined per prostate cancer working group (PCWG) criteria as a reduction in the PSA level of 50% or more from baseline measured at consecutive assessments at least 3 weeks apart.

  Time frame: Up to approximately 54 months

• Safety Lead-in Phase: Number of Participants Who Experience One or More Dose-Limiting Toxicities (DLTs) - Combination Arms Only

  The following events if considered drug related by the Investigator, will be considered a DLT: Grade 4 nonhematologic toxicity (not based on laboratory value); Grade 4 hematologic toxicity lasting ≥7 days, except thrombocytopenia; Grade 4 thrombocytopenia of any duration; Grade 3 thrombocytopenia associated with clinically significant bleeding; Nonhematologic AEs ≥Grade 3 with exceptions; Grade 3 or Grade 4 non-hematologic laboratory values if requires medical intervention, leads to hospitalization, persists for \>1 week, or results in a Drug-induced Liver Injury with exceptions; Grade 3 or 4 febrile neutropenia; Study intervention - related toxicities that lead to discontinuation of study treatment during Cycle 1; Prolonged delay (\>2 weeks) in initiating Cycles 2 due to treatment-related toxicity; Missing \>25% of study intervention doses as a result of treatment-related AE during Cycle 1; Grade 5 toxicity.

  Time frame: Up to approximately 21 days

• Safety Lead-in Phase: Number of Participants Who Experienced an Adverse Event (AE) - Combination Arms Only

  An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

  Time frame: Up to approximately 21 days

• Safety Lead-in Phase: Number of Participants Who Discontinued Study Intervention Due to an AE - Combination Arms Only

  An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

  Time frame: Up to approximately 21 days