In the discovery cohort (n = 16), the median number of nonsynonymous mutations was 302 in patients with durable clinical benefit (DCB) (partial or stable response lasting >6 months) versus 148 with no durable benefit (NDB) (Mann-Whitney P = 0.02) (Fig. 1A). Seventy-three percent of patients with high nonsynonymous burden (defined as above the median burden of the cohort, 209) experienced DCB, compared with 13% of those with low mutation burden (below median) (Fisher’s exact P = 0.04). Both confirmed objective response rate (ORR) and progression-free survival (PFS) were higher in patients with high nonsynonymous burden...The validation cohort included an independent set of 18 NSCLC samples from patients treated with pembrolizumab...The rates of DCB and PFS were again significantly greater in patients with a nonsynonymous mutation burden above 200, the median of the validation cohort.