KEYNOTE-365 cohort B updated results: Pembrolizumab (pembro) plus docetaxel and prednisone in abiraterone (abi) or enzalutamide (enza)-pretreated patients (pts) with metastatic castrate-resistant prostate cancer (mCRPC).

• DOI: 10.1200/jco.2020.38.6_suppl.103
• Publication Date: 2020-02-19T16:59:57Z
• Authors: Michael Paul Koli...; Gwenaelle Gravis; Loic Mourey; Josep M. Piulats; Srikala S. Sridhar; Emanuela Romano; William R. Berry; Howard Gurney; Margitta Retz; Leonard Joseph Ap...; Martin Boegemann; Johann S. De Bono; Anthony M. Joshua; Urban Emmenegger; Henry Jacob Conter; Brigitte Laguerre; Helen Wu; Charles Schloss; Christian Heinric...; Evan Y. Yu
• Keywords: 03 medical and health sciences; 0302 clinical medicine; Neoplasms. Tumors. Oncology. Including cancer and carcinogens; RC870-923; Diseases of the genitourinary system. Urology; RC254-282; 3. Good health

103 Background: KEYNOTE-365 (NCT02861573) is a phase 1b/2 study to evaluate pembro in combination with other agents in mCRPC. Here we report updated results from cohort B (pembro + docetaxel and prednisone). Methods: Cohort B enrolled pts who failed or were intolerant to ≥4 wk of abi or enza in the prechemotherapy mCRPC state and whose disease progressed within 6 mo of screening as determined by PSA progression or radiologic bone/soft tissue progression. Pts received pembro 200 mg IV + docetaxel 75 mg/m2 IV Q3W and prednisone 5 mg orally twice daily. Primary end points were safety, PSA response rate (confirmed PSA decrease >50%), and ORR per blinded independent central review (BICR). Results: Of 104 treated pts, 72 discontinued, primarily due to progression (55%). Median age was 68 y (range 50-86), 24% were PD-L1+, 25% had visceral disease, and 50% had measurable disease. Median follow-up was 13 mo for all pts (n=104) and 19 mo for pts who had ≥27 wk of follow up (n=72). See table for efficacy outcomes. Treatment-related AEs occurred in 100 pts (96%); most frequent (≥30%) were alopecia, diarrhea, and fatigue (39% each). Grade 3-5 treatment-related AEs occurred in 42 pts (40%). Five pts died of AEs; 2 deaths were from treatment-related AEs (pneumonitis). Conclusions: With additional follow-up, pembro + docetaxel and prednisone continued to show activity in pts with mCRPC who failed previous antihormonal therapy. Safety of the combination was consistent with the known profiles of the individual agents and will be further evaluated in a phase 3 study (KEYNOTE-921). Clinical trial information: NCT02861573. [Table: see text]