Genomic correlates of response to immune checkpoint blockade in microsatellite-stable solid tumors

Tumor mutational burden correlates with response to immune checkpoint blockade in multiple solid tumors, though in microsatellite stable tumors this association is weak and of limited clinical utility. Here, we uniformly analyzed whole exome sequencing (WES) of 249 tumors and matched normal tissue from patients with clinically annotated outcomes to immune checkpoint therapy, including radiographic response, across multiple cancer types to examine additional tumor genomic features that contribute to selective response. Our analyses identified genomic correlates of response beyond mutational burden, including somatic events in individual driver genes, certain global mutational signatures, and specific HLA-restricted neoantigens. However, these features were often inter-related, highlighting the complexity of identifying genetic driver events that generate an immunoresponsive tumor environment. This study lays a path forward in analyzing large clinical cohorts in an integrated and multifaceted manner to enhance our ability to discover clinically meaningful predictive features of response to immune checkpoint blockade.