Abstract 1263: Comprehensive genomic profiling to identify biomarkers predictive of response to immunotherapy

Abstract Background: Immune-oncology (I-O) drugs show promise across multiple tumor types, and several biomarkers (BM) predict responsiveness to I-O therapy. In this descriptive study of clinical lab experience (2018-2021), we investigated the prevalence of genomic BMs associated with sensitivity and resistance to I-O drugs across solid tumors. Methods: The GEM ExTra® assay was used to exome-sequence 2,359 paired samples at 180X and 400X coverage for germline and tumor DNA respectively. Reportable alterations were single base substitutions, indels, copy number alterations, fusions, alternate transcripts, as well as tumor mutational burden (TMB) and microsatellite instability (MSI) status. For I-O sensitive BMs we recorded MSI-High status, TMB-High (> 10 mut/Mb) status, and mutations in POLE/POLD1, MLH1, MSH2/3/6, PMS1/2, PD-L1/-L2, CTLA4, CD28, ARID2, and PBRM1. For I-O resistance BMs, IDO1 amplification and mutations in B2M, JAK1/2, IDO1, KRAS and STK11 were tallied. Results: I-O sensitive BMs varied from 0% to 58% (results in Table 1 for selected tumor types). Overall, TMB-High was in 6% of samples and MSI-High in 3%; all MSI-High were also TMB-High. In the 46% of renal cell carcinoma samples with I-O-sensitive BMs, PBRM1 mutation was common (94%). In 3 TMB-High endometrial samples, POLE/POLD1 was mutated, indicative of an ultra-mutated phenotype. Of note, 35% of colorectal cancer and 8% of melanoma samples with I-O sensitive mutations also had loss-of-function mutations in JAK1/2 and B2M, suggestive of I-O resistance. In non-small cell lung cancer, co-mutation of STK11 and KRAS, suggesting inferior response to I-O therapy, was present in 4% of samples with I-O BMs. IDO1 amplification was present in less than 1% of entire cohort. Conclusions: Our study found I-O sensitive BMs in common and in rare aggressive cancers. The GEM ExTra assay can stratify cancer patients for likely responsiveness to immunotherapy. Table 1. Immune-oncology sensitive biomarkers observed across select tumors Solid tumor type % of samples with signature All (n = 2,360) 13% Melanoma (n = 50) 54% Other skin cancers (n = 13) 62% Renal cell carcinoma (n = 200) 46% Urothelial (n = 86) 22% Endometrial (n = 88) 20% Gastro-intestinal (n = 360) 12% Sarcoma (n = 90) 11% Prostate (n = 151) 6% Lung (n = 100) 4% Breast (n = 297) 2% Central nervous system (n = 60) 0% Citation Format: Pawan Noel, David W. Hall, Sameer S. Udhane, Min Wang, Fadel S. Alyaqoub, Szabolcs Szelinger, Audrey A. Ozols, Janine R. LoBello, Frederick L. Baehner, Gargi D. Basu. Comprehensive genomic profiling to identify biomarkers predictive of response to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1263.