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PROSTATE: METASTATIC: 2nd line or greater: Pembro/Vibostolimab: KEYNOTE-365 ARM G

Phase Ib/II Trial of Pembrolizumab (MK-3475) Combination Therapies in Metastatic Castration-Resistant Prostate Cancer (mCRPC) (KEYNOTE-365)

Merck Prostate KEYNOTE 365 ARM G
Study Title

Phase Ib/II Trial of Pembrolizumab (MK-3475) Combination Therapies in Metastatic Castration-Resistant Prostate Cancer (mCRPC) (KEYNOTE-365)

Site Link
Disease Setting
Line Of Therapy
2nd line or greater
Investigational Agent
Pembrolizumab Vibostolimab coformulation
Drug Class
PD-1 inhibitor + Anti-TIGIT
Dan Vaena, MD
Merck Sharp and Dohme
Key Eligibility Criteria
Key Eligibility Criteria Details
  • Has histologically- or cytologically-confirmed adenocarcinoma of the prostate without small cell histology
  • Must provide a core or excisional biopsy from soft tissue or bone biopsy within 1 year of screening and after developing mCRPC. Participants with bone metastasis only must provide an archival tumor tissue specimen.
  • Has prostate cancer progression within 6 months prior to screening, as determined by the investigator, by means of one of the following: PSA progression as defined by a minimum of 2 rising PSA levels with an interval of ≥1 week between each assessment where the PSA value at screening should be ≥2 ng/mL; radiographic disease progression in soft tissue based on RECIST criteria with or without PSA progression; radiographic disease progression in bone defined as the appearance of 2 or more new bone lesions on bone scan with or without PSA progression. 
  • Has ongoing androgen deprivation with serum testosterone <50 ng/dL (<2.0 nM)
  • Patients receiving bone resorptive therapy must be on stable doses
  • ECOG PS 0-1
  • Has received docetaxel for mCRPC. Prior treatment with 1 other chemotherapy for mCRPC is allowed. Up to 2 second-generation hormonal manipulations (eg, abiraterone acetate, enzalutamide, apalutamide, darolutamide or other next-generation hormonal agents [NHA]) are allowed. Participants who received prior ketoconazole for metastatic disease may be enrolled. If docetaxel chemotherapy is used more than once (eg, once for metastatic hormone-sensitive and once for mCRPC), it will be considered as 1 therapy. Prior docetaxel for metastatic hormone-sensitive prostate cancer (mHSPC) is allowed if ≥4 weeks have elapsed from the last dose of docetaxel prior to Day 1 of Cycle 1
  • No immunodeficiency or systemic steroid use
  • No active autoimmune disease within 2 years
  • No known HIV/HBV/HCV
  • No known CNS mets
  • No superscan bone scan
  • No symptomatic ascites or pleural effusion
  • Primary
    • Percentage of patients with PSA decrease of >/= 50%
    • AEs
    • ORR
  • Secondary
    • DCR
    • OS
    • DOR
    • ORR by PCWG3-modified RECIST
    • Time to PSA progression
    • Radiographic PFS
    • Composite response rate (PFS, PSA)
Assessment Frequency
Assessment Frequency 2

Assessment Frequency Link
Dosing Frequency
Control Agents
Study Protocol