KRAS inhibition is an effective therapy for appendiceal adenocarcinoma

Background Appendiceal adenocarcinoma (AA) is a rare cancer with limited treatment options. KRAS is the most commonly mutated gene in AA and a promising therapeutic target, but its preclinical and translational relevance in AA remains unclear.

We evaluated KRASG12D–specific (MRTX1133) and pan-KRAS inhibitor (RMC-6236) in KRASmut organoid and orthotopic PDX models of AA. Tumor-intrinsic and microenvironmental responses were characterized using multi-omics profiling. Clinical outcomes were also assessed in six heavily pre-treated AA patients treated with KRAS inhibitors.

MRTX1133 was highly effective for KRASG12D organoids (IC50=4.1 nM); both KRASG12D and KRASG12V organoids were sensitive to RMC-6236 (IC50=4.4 nM vs 0.5 nM, respectively). In orthotopic PDX models of peritoneal carcinomatosis from AA, MRTX1133 significantly reduced tumor growth in the KRASG12D model TM00351, and RMC-6236 reduced tumor growth in KRASG12V model AAPDX-16. Pathologic evaluation showed dramatically reduced tumor cellularity, proliferation, and pERK expression as well as induction of apoptosis. Gene Sets Enrichment Analysis (GSEA) revealed significant downregulations of ‘E2F targets (NES=-1.9, p-adj=0.06) and the newly developed ‘RAS/ERK (NES=-2.3, p-adj=0.06)’ gene set, consistent with the observed decrease in cell proliferation. There was marked upregulation of EMT (NES=2.7, FDR<0.001) and TGF-β signaling (NES=2.3, FDR=0.004) in remaining tumor cells, suggesting these pathways could confer resistance. scRNA-seq analysis of TME showed dramatic shifts in cancer-associated fibroblasts (CAFs), with KRAS inhibition driving a shift from normal fibroblasts to inflammatory CAFs, and upregulation of interferon alpha and gamma pathways, suggesting that KRAS inhibition can activate innate immune response in the setting of peritoneal metastases. In a cohort of 6 heavily pre-treated patients with AA treated with KRAS inhibitors (1 G12D, 3 G12C, 2 pan-KRAS), all had biochemical response based on CEA/Ca19-9 or ctDNA and clinical benefit by RECIST criteria (1 CR, 1 PR, 4 SD).

While effective suppression of RAS/ERK signaling by KRAS inhibitors reduces tumor growth, adaptive activation of EMT and TGF-β pathways may mediate resistance in KRASmut AA. Additionally, KRAS inhibition remodels TME and may enhance innate immune signaling. These findings support continued clinical development of KRAS inhibitors in AA and provide a rationale for combination strategies targeting resistance pathways and stromal remodeling. Competing Interest Statement Dr. John Paul Shen: Grant/Research support/ Collaboration: Natera, Inc; BostonGene; Revolution Medicine; Summit Therapeutics Consulting / Stock ownership: Engine Biosciences, NaDeNo Nanoscience Patent: Siegel D, Schweer J, Abagyan R, Shen JP. SMALL MOLECULE FOR TREATMENT OF CANCER OF THE APPENDIX. Filed July 17, 2023, PCT/US2023/027939 Dr. David Hong: Grant/Research support/ Collaboration: 280 Bio, AbbVie, Adaptimmune, Adlai-Nortye, Amgen, Astelles, Astra-Zeneca, Bayer, BeiGene USA, BioBridge, Biomea Fusion, Bristol-Myers Squibb, Deciphera, E.R. Squibb & Sons LLC, Eisai, Eli Lilly, Endeavor, Erasca, Exelixis Inc., F. Hoffmann-LaRoche, Genentech, Immunogenesis, Incyte Inc., Merck, Mirati, NCI-CTEP, Novartis, Pfizer, Quanta Therapeutics, Revolution Medicines, STCube Pharmaceuticals, VM Oncology, and Yiling Pharmaceutical. Travel, accommodations, or expense support: American Association of Cancer Research (AACR), American Society of Clinical Oncology (ASCO), Bayer, BeiGene USA Inc., Genmab, Medscape, Mirati Therapeutics Inc., Pfizer, Society for the Immunotherapy of Cancer (SITC), and Telperian. Consulting, speaker, or advisory role: 280 Bio, Acuta Capital Partners LLC, Alpha Insights, Amgen, Bayer, Boxer Capital, Children's Oncology Group, COR2ed, Cowen Group Inc, Crossbridge Bio, Ecor1 Capital, Erasca, Gerson Lehrman Group Inc., Group H, Guidepoint, Immunogenesis, Jansen Pharmaceuticals, Kestrel Therapeutics, Medacorp, Medscape, Orbi Capital, Pfizer, Revolution Medicines, T-Knife, Travistock Group, WebMD, and Yiling Pharmaceutical. Ownership interests: Molecular Match (Advisor), OncoResponse (Founder, Advisor), Telperian (Founder, Advisor), and CrossBridge Bio (Advisor). Dr. Michael J. Overman: Consulting/advisory role: Bristol Myers Squibb, Roche/Genentech, Gritstone Bio, MedImmune, Novartis, Array BioPharma, Janssen, Pfizer, 3D Medicines, Merck, Eisai, Simcere; Research funding: Bristol Myers Squibb, Merck, Roche, MedImmune.