Preliminary data from an open-label Phase 1b/2 clinical trial, KEYNOTE-365, evaluating Merck’s (NYSE: MRK) Keytruda (pembrolizumab), combined with various agents, in patients with metastatic castration-resistant prostate cancer (mCRPC) showed a treatment effect across three cohorts. The results are being presented at the ASCO GU Cancers Symposium in San Francisco.
Cohort A: Keytruda + AstraZeneca’s (NYSE: AZN) Lynparza (olaparib): Prostate specific antigen (PSA) response rate was 12% (n=5/41). Median time to PSA progression was 15.3 weeks in patients with measurable disease. The disease control rate (DCR) (responders + stable cancer) was 29% (n=12/41). 49% (n=21/41) of patients experienced a serious or life-threatening treatment-related adverse events, the most common being anemia (27%).
Cohort B: Keytruda + docetaxel and prednisone: PSA response rate was 31% (n=22/72). Median time to PSA progression: 24.1 weeks. DCR: 57% (n=41/72). 36% (n=26/72) experienced a serious, life-threatening or fatal treatment-related adverse event. Two patients died from pneumonitis (lung tissue inflammation).
Cohort C: Keytruda + Pfizer (NYSE: PFE) and Astellas Pharma’s ( OTCPK:ALPMY) Xtandi (enzalutamide): PSA response rate: 26% (n=18/69). Median time to PSA progression: 18.4 weeks. DCR: 33% (n=23/69). 41% (n=28/69) of patients experienced a serious or life-threatening treatment-related adverse event, the most common being a rash (10%).
Merck is initiating three new pivotal prostate cancer trials: KEYLYNK-010 (Keytruda + Lynparza), KEYNOTE-921 (Keytruda + docetaxel and prednisone) and KEYNOTE-621 (Keytruda + Xtandi).
Source:: Daily times