A Clinical Study of Ifinatamab Deruxtecan (I-DXd) in People With Metastatic Prostate Cancer (MK-2400-001)

• Ifinatamab deruxtecan (Drug), also known as I-DXd, MK-2400, DS-7300a: Administered via intravenous (IV) infusion every 3 weeks (q3w) until disease progression, unacceptable adverse events (AEs), or other cessation of treatment
• Docetaxel (Drug): Administered via IV infusion q3W until disease progression, unacceptable adverse events (AEs), or other cessation of treatment
• Prednisone (Drug), also known as Prednisone acetate, Prednisolone, Prednisolone acetate: Oral tablet administered once per day or per approved product label
• Rescue Medication (Drug), also known as 5-HT3 receptor antagonist, NK-1 receptor antagonist, Corticosteroid: Before administering each dose of I-DXd, premedication is required for prevention of nausea and vomiting with a 2 or 3 drug combination regimen (eg, corticosteroids with either a 5-HT3 receptor antagonist or an NK-1 receptor antagonist and other drugs as indicated) per approved product label

Primary outcomes

• Overall Survival (OS) [Up to approximately 36 months]: OS is defined as the time from randomization to death due to any cause.
• Radiographic Progression Free Survival (rPFS) [Up to approximately 36 months]: rPFS is defined as the time from randomization to the first documented disease progression per prostate cancer working group (PCWG)-modifed Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 by blinded independent central review (BICR) or death due to any cause, whichever occurs first.

Secondary outcomes

• Time to First Subsequent Therapy (TFST) [Up to approximately 36 months]: TFST is defined as the time from randomization to initiation of the first subsequent anticancer therapy or death, whichever occurs first.
• Objective Response Rate (ORR) [Up to approximately 36 months]: The ORR is defined as a confirmed complete response (CR) or partial response (PR) per PCWG-modified RECIST 1.1 as assessed by BICR.
• Duration of Response (DOR) [Up to approximately 36 months]: For participants who demonstrate confirmed CR or PR, DOR is defined as the time from the first documented evidence of CR or PR until disease progression per PCWG-modified RECIST 1.1 as assessed by BICR or death due to any cause, whichever occurs first.
• Time to Pain Progression (TTPP) [Up to approximately 36 months]: TTPP is defined as the time from randomization to pain progression based on the brief pain inventory-short form (BPI-SF) Item 3 "worst pain in 24 hours" and opiate analgesic use (AQA score).
• Time to Prostate-specific Antigen (PSA) Progression [Up to approximately 36 months]: Time to PSA progression is defined as the time from randomization to PSA progression. The PSA progression date is defined as the first date that 1) ≥25% increase and ≥2 ng/mL above the nadir which is confirmed by a second value≥3 weeks later if there is PSA decline from baseline, 2) ≥25% increase and ≥2 ng/mL increase from baseline beyond 12 weeks if there is no PSA decline from baseline.
• PSA Response Rate [Up to approximately 36 months]: PSA response rate is defined as the proportion of participants in the analysis population who have a PSA reduction of ≥50% from baseline with a consecutive confirmation assessment at least 3 weeks later per PCWG criteria.
• Time to First Symptomatic Skeletal-Related Event (SSRE) [Up to approximately 36 months]: Time to first SSRE is defined as the time from randomization to the first occurrence of any of the following symptomatic skeletal-related events: 1. use of EBRT to prevent or relieve skeletal symptoms, 2. new symptomatic pathologic bone fracture (vertebral or non-vertebral), 3. spinal cord compression, 4. a tumor-related orthopedic surgical intervention.
• Number of Participants Who Experienced at Least One Adverse Event (AE) [Up to approximately 36 months]: 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.
• Number of Participants Who Discontinue Study Treatment Due to an Adverse Event (AE) [Up to approximately 36 months]: 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.

Sex: Male, ages: 18 Years to any

Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

* Has histologically- or cytologically-confirmed adenocarcinoma of the prostate without small cell histology
* Has prostate cancer progression while on androgen deprivation therapy (ADT) (or post bilateral orchiectomy) within 6 months prior to Screening
* Has current evidence of distant metastatic disease (M1 disease) documented by either bone lesions on bone scan and/or soft tissue disease by computed tomography (CT)/magnetic resonance imaging (MRI)
* Has received prior treatment with 1 or 2 androgen receptor pathway inhibitors (ARPIs) and progressed during or after at least 8 weeks of treatment
* Has provided tumor tissue from a core or excisional biopsy from soft tissue not previously irradiated and obtained after disease progression on the most recent prior therapy
* Has recovered from adverse events (AEs) due to previous anticancer therapies

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

* Is unable to swallow tablets/capsules
* Has any of the following indicators of interstitial lung disease (ILD)/pneumonitis:

  1. Has any history of ILD/pneumonitis that required steroid use, except for a history of radiation pneumonitis that did not require steroids
  2. Has current ILD/pneumonitis
  3. Has a clinical or radiographic suspicion of ILD for which the diagnosis of ILD cannot be ruled out
* Has clinically severe pulmonary compromise resulting from intercurrent pulmonary illnesses
* Has uncontrolled or significant cardiovascular disease
* Has received prior treatment with a taxane-based chemotherapy agent for metastatic castration-resistant prostate cancer (mCRPC)
* Has had prior discontinuation of an antibody drug conjugate (ADC) that consists of an exatecan derivative (eg, trastuzumab deruxtecan) due to treatment-related toxicities
* Has a "superscan" bone scan

203 more sites not listed.

• Medical Director, Study director, Merck Sharp & Dohme LLC