Yarchoan M, et al. - In patients with MMRp colorectal cancer (CRC) who had received at least two prior lines of therapy in the metastatic setting, researchers tested the safety and efficacy of GVAX/cyclophosphamide (Cy) in combination with the programmed cell death protein 1 (PD1) inhibitor pembrolizumab. For this investigation, 17 patients were recruited. The results of this open label, single-arm, phase 2 study indicated that GVAX/Cy plus pembrolizumab is well tolerated in advanced MMRp CRC, leading to CEA responses but not radiographic responses. In this small cohort, progression-free survival and overall survival compare favorably to historical controls. CEA responses in MMRp CRC have not been observed with PD1 monotherapy, suggesting that GVAX can modulate the antitumor immune response.