Marwan Fakih, Patricia Marinello, M. Lee, R. Kim, Mustapha Tehfe, L. Wong, J. Chaves, E. G. Chiorean, Petr Kavan, Carlos Alberto Mayo, J.J. Li, K. Spencer, and Jeremy S. Kortmansky
Background Pembro, a PD-1 inhibitor, confers durable benefit in many tumor types but has limited efficacy in non–microsatellite instability–high (MSI-high)/pMMR mCRC. Chemotherapies that include 5-fluorouracil (5-FU), oxaliplatin and irinotecan, which are commonly used to treat mCRC, may modulate intrinsic tumor immunogenicity and sensitize tumors to immunotherapy agents. In the phase 1b KEYNOTE-651 study (NCT03374254), pembro + mFOLFOX7 (cohort B) or pembro + FOLFIRI (cohort D) was evaluated in patients with non–MSI-high/pMMR mCRC. Methods Patients were ≥18 years with non–MSI-high/pMMR mCRC, Eastern Cooperative Oncology Group performance status 0/1, and no prior systemic chemotherapy for stage IV mCRC (cohort B) or 1 prior therapy including a fluoropyrimidine + oxaliplatin-based regimen (cohort D). Patients received pembro 200 mg every 3 weeks (Q3W) + mFOLFOX7 (oxaliplatin [85 mg/m2]; leucovorin [400 mg/m2]; 5-FU [2400 mg/m2]) Q2W (cohort B) or pembro 200 mg Q3W + FOLFIRI (irinotecan [180 mg/m2]; leucovorin [400 mg/m2]; 5-FU [2400 mg/m2]) Q2W (cohort D). Primary objectives were safety/tolerability and establishment of the recommended phase 2 dose (RP2D); the secondary objective was objective response rate. Results At data cutoff (Feb 18, 2019), 15 patients in cohort B and 16 in cohort D started treatment; median follow-up was 6.8 months (cohort B) and 5.7 months (cohort D). Treatment was discontinued in 4 patients (27%) in cohort B (adverse event [AE], n = 1 [7%]; PD, n = 3 [20%]) and 9 patients (56%) in cohort D (AEs, PD, patient withdrawal; n = 3 [19%] each). There was 1 dose-limiting toxicity in cohort D: grade 3 small-intestinal obstruction. See RP2Ds for cohorts B and D in the Methods section. All patients had ≥1 treatment-related AE (TRAE). Grade 3 TRAEs occurred in 8 patients each in cohort B (53%) and cohort D (50%), most commonly anemia and neutropenia (13% each) in cohort B and neutropenia, diarrhea, fatigue, and leukopenia (13% each) in cohort D. There were no grade 4-5 TRAEs. Efficacy results will be presented. Conclusions Pembro in combination with mFOLFOX7 or FOLFIRI was safe and tolerable in patients with mCRC. Clinical trial identification NCT03374254; Release date: December 15, 2017. Editorial acknowledgement Jacqueline Kolston, PhD, of the ApotheCom pembrolizumab team (Yardley, PA, USA); Funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Legal entity responsible for the study Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA, and Array BioPharma. Funding Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA, and Array BioPharma. Disclosure R. Kim: Advisory / Consultancy, Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (institution): BMS; Advisory / Consultancy, Speaker Bureau / Expert testimony: Lilly; Research grant / Funding (institution): Eisai. J. Kortmansky: Research grant / Funding (institution): Merck; Research grant / Funding (institution): Roche. L. Wong: Research grant / Funding (institution): Astellas Pharma Global Development, Inc./Astellas US, Inc.; Research grant / Funding (institution): BeiGene, Ltd; Research grant / Funding (institution): Exelixis, Inc.; Research grant / Funding (institution): Merck; Research grant / Funding (institution): NovoCure, Inc.; Research grant / Funding (institution): Pierre Fabre Medicament; Research grant / Funding (institution): PledPharma AB; Research grant / Funding (institution): SynCore Biotechnology Co., Ltd.; Research grant / Funding (institution): Halozyme, Inc.; Research grant / Funding (institution): Pharmacyclics, Inc.; Research grant / Funding (institution): TESARO; Research grant / Funding (institution): EMD Serono; Research grant / Funding (institution): Array. M. Tehfe: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Merck; Honoraria (self), Advisory / Consultancy, Research grant / Funding (self): Celgene; Honoraria (self): Ipsen; Advisory / Consultancy: BMS; Advisory / Consultancy: Takeda; Advisory / Consultancy: AstraZeneca; Honoraria (self), Advisory / Consultancy: Taisho. J.J. Li: Full / Part-time employment: Merck & Co., Inc. M. Lee: Shareholder / Stockholder / Stock options, Full / Part-time employment: Merck & Co., Inc. C. Mayo: Full / Part-time employment: Merck & Co., Inc. P. Marinello: Shareholder / Stockholder / Stock options, Full / Part-time employment: Merck & Co., Inc. E. Chiorean: Advisory / Consultancy: Ipsen; Advisory / Consultancy: Eisai; Advisory / Consultancy: Halozyme; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Seattle Genetics; Advisory / Consultancy: Array; Advisory / Consultancy: Five Prime; Research grant / Funding (institution): Boehringer Ingelheim; Research grant / Funding (institution): Celgene; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): AstraZeneca; Travel / Accommodation / Expenses: Halozyme; Research grant / Funding (institution): Merck; Research grant / Funding (institution): BMS; Research grant / Funding (institution): Ignyta/Roche; Research grant / Funding (institution): Stemline; Research grant / Funding (institution): Macrogenetics. All other authors have declared no conflicts of interest.