Germline DNA damage response gene mutations as predictive biomarkers of immune checkpoint inhibitor efficacy

BackgroundImpaired DNA damage response (DDR) can affect immune checkpoint inhibitors (ICI) efficacy and lead to heightened immune activation. We assessed the impact of pathogenic or likely pathogenic (P/LP) germline DDR mutations on ICI response and toxicity.Materials and methodsA retrospective analysis of 131 cancer patients with germline DNA testing and ICI treatment was performed.ResultsNinety-two patients were DDR-negative (DDR-), and 39 had ≥1 DDR mutation (DDR+). DDR+ patients showed higher objective response rates (ORRs) compared to DDR- in univariate and multivariable analyses, adjusting for age and metastatic disease (62% vs. 23%, unadjusted OR = 5.41; 95% CI, 2.41-12.14; adjusted OR 5.94; 95% CI, 2.35-15.06). Similar results were seen in mismatch repair (MMR), DDR pathways with intact MMR (DDR+MMRi), and homologous recombination (HR) subgroups versus DDR- (adjusted OR MMR = 24.52; 95% CI 2.72-221.38, DDR+MMRi = 4.26; 95% CI, 1.57-11.59, HR = 4.74; 95% CI, 1.49-15.11). DDR+ patients also had higher ORRs with concurrent chemotherapy (82% vs. 39% DDR-, p=0.03) or concurrent tyrosine kinase inhibitors (50% vs. 5% DDR-, p=0.03). No significant differences in immune-related adverse events were observed between DDR+ and DDR- cohorts.ConclusionP/LP germline DDR mutations may enhance ICI response without significant additional toxicity.