• Mark M Awad, Shengwu Liu, Igor I Rybkin, Kathryn C Arbour, Julien Dilly, Viola W Zhu, Melissa L Johnson, Rebecca S Heist, Tejas Patil, Gregory J Riely, Joseph O Jacobson, Xiaoping Yang, Nicole S Persky, David E Root, Kristen E Lowder, Hanrong Feng, Shannon S Zhang, Kevin M Haigis, Yin P Hung, Lynette M Sholl, Brian M Wolpin, Julie Wiese, Jason Christiansen, Jessica Lee, Alexa B Schrock, Lee P Lim, Kavita Garg, Mark Li, Lars D Engstrom, Laura Waters, J David Lawson, Peter Olson, Piro Lito, OuSai-Hong ISIFrom Dana-Farber Cancer Institute (M.M.A., S.L., J.D., J.O.J., K.E.L., H.F., K.M.H., B.M.W., P.A.J., A.J.A.), Massachusetts General Hospital (R.S.H., Y.P.H.), and Brigham and Women's Hospital (L.M.S., A.J.A.), Boston, and Broad Institute of , James G Christensen, Pasi A Jänne, and Andrew J Aguirre.
• From Dana-Farber Cancer Institute (M.M.A., S.L., J.D., J.O.J., K.E.L., H.F., K.M.H., B.M.W., P.A.J., A.J.A.), Massachusetts General Hospital (R.S.H., Y.P.H.), and Brigham and Women's Hospital (L.M.S., A.J.A.), Boston, and Broad Institute of MIT and Harvard (S.L., X.Y., N.S.P., D.E.R., K.M.H., A.J.A.) and Foundation Medicine (J.L., A.B.S.), Cambridge - all in Massachusetts; Henry Ford Cancer Institute, Detroit (I.I.R.); Memorial Sloan Kettering Cancer Center, New York (K.C.A., G.J.R., P.L.); Chao Family Comprehensive Cancer Center, University of California, Irvine, School of Medicine, Orange (V.W.Z., S.S.Z., S.-H.I.O.), Boundless Bio, La Jolla (J.W., J.C.), and Mirati Therapeutics, San Diego (L.D.E., L.W., J.D.L., P.O., J.G.C.) - all in California; Sarah Cannon Research Institute, Tennessee Oncology/OneOncology, Nashville (M.L.J.); the University of Colorado, Aurora (T.P.); and Resolution Bioscience, Kirkland, WA (L.P.L., K.G., M.L.).
• N. Engl. J. Med. 2021 Jun 24; 384 (25): 2382-2393.

BackgroundClinical trials of the KRAS inhibitors adagrasib and sotorasib have shown promising activity in cancers harboring KRAS glycine-to-cysteine amino acid substitutions at codon 12 (KRASG12C). The mechanisms of acquired resistance to these therapies are currently unknown.MethodsAmong patients with KRASG12C -mutant cancers treated with adagrasib monotherapy, we performed genomic and histologic analyses that compared pretreatment samples with those obtained after the development of resistance. Cell-based experiments were conducted to study mutations that confer resistance to KRASG12C inhibitors.ResultsA total of 38 patients were included in this study: 27 with non-small-cell lung cancer, 10 with colorectal cancer, and 1 with appendiceal cancer. Putative mechanisms of resistance to adagrasib were detected in 17 patients (45% of the cohort), of whom 7 (18% of the cohort) had multiple coincident mechanisms. Acquired KRAS alterations included G12D/R/V/W, G13D, Q61H, R68S, H95D/Q/R, Y96C, and high-level amplification of the KRASG12C allele. Acquired bypass mechanisms of resistance included MET amplification; activating mutations in NRAS, BRAF, MAP2K1, and RET; oncogenic fusions involving ALK, RET, BRAF, RAF1, and FGFR3; and loss-of-function mutations in NF1 and PTEN. In two of nine patients with lung adenocarcinoma for whom paired tissue-biopsy samples were available, histologic transformation to squamous-cell carcinoma was observed without identification of any other resistance mechanisms. Using an in vitro deep mutational scanning screen, we systematically defined the landscape of KRAS mutations that confer resistance to KRASG12C inhibitors.ConclusionsDiverse genomic and histologic mechanisms impart resistance to covalent KRASG12C inhibitors, and new therapeutic strategies are required to delay and overcome this drug resistance in patients with cancer. (Funded by Mirati Therapeutics and others; ClinicalTrials.gov number, NCT03785249.).Copyright © 2021 Massachusetts Medical Society.

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