Abstract 4026: JDQ443, a covalent inhibitor of KRASG12C with a novel binding mode, shows broad antitumor activity in KRASG12C preclinical models as a single agent and in combination with inhibitors of SHP2, MEK or CDK4/6

Background: Oncogenic mutations occurring in the KRAS component of the RAS/MAPK pathway slow nucleotide cycling between its active (GTP-bound) and inactive (GDP-bound) states, shifting it towards the active state and increasing oncogenic signaling. Among these mutations, the glycine-to-cysteine mutation of amino acid 12 (KRASG12C), found in ~13% of non-small cell lung cancer (NSCLC) and ~4% of colorectal cancer (CRC), can be specifically targeted and irreversibly locked in the inactive state by covalent modification of Cys12. We have previously reported the discovery and preclinical profile of JDQ443, a selective, oral, covalent inhibitor of KRASG12C that binds under the Switch II loop. Here, we report its antiproliferative and antitumor activity against panels of cancer cell lines as well as cell- (CDX) and patient-derived (PDX) tumor xenografts. Methods: JDQ443 antiproliferative activity was assessed by a high-throughput cell viability assay in a large panel of KRASG12C (n=17) and non-G12C (n=233) cell lines. Single-agent antitumor activity was assessed against a panel of KRASG12C CDX models from NSCLC (LU99, H2122, H2030, and HCC44), pancreatic (Mia PaCa-2), and esophageal (KYSE410) cancer cell lines, plus one non-G12C lung line (H441; KRASG12V). JDQ443 in vivo activity against a panel of KRASG12C NSCLC (n=10) and CRC (n=9) PDX models was assessed either as a single agent or in combination with TNO155 (SHP2 inhibitor [i]), trametinib (MEKi), or ribociclib (CDK4/6i). In vivo combination studies with TNO155 were also performed in CDX models (LU99, H2030, HCC44, and KYSE410). Results: In vitro, JDQ443 demonstrated potent antiproliferative activity selectively towards KRASG12C cell lines. Dose-dependent tumor growth inhibition/regression was observed for all KRASG12C CDX models, but not for the H441 KRASG12V model, and was independent of once-daily (QD) or twice-daily (BID) dosing. Single-agent antitumor activity (best average response, duration of reduction in tumor doubling time) was observed across both PDX panels and was improved by all three combination treatments. The JDQ443/TNO155 combination improved single-agent activity across CDX models, with comparable antitumor benefit maintained at QD or BID TNO155 schedules in two of three models (LU99 and KYSE410). Combination with TNO155 allowed a reduced dose of JDQ443 to achieve similar target occupancy and antitumor activity versus JDQ443 alone. Conclusions: JDQ443 demonstrates significant activity again