Abstract 4388: Novel small molecule on state inhibitor for GTP bound pan-KRAS (G12) mutations

Abstract Introduction: KRAS is part of the RAS family of small GTPases. They act as molecular switches by cycling between an active GTP-bound (ON) state and an inactive GDP-bound (OFF) state in response to extracellular signals. KRAS is frequently mutated in nearly 30% of cancers, with the G12, G13, and Q61 hotspots being the most common [1]. Among these, G12 mutations account for 83% of KRAS mutations, being one of the most prevalent drivers of cancers [2]. Active KRAS triggers effector pathways like MAPK and PI3K, promoting cellular proliferation and survival. Oncogenic KRAS remains constitutively active due to defective GTP hydrolysis [3]. Therefore, inhibitors that target the “ON” state can effectively interrupt the signaling pathways that promote cancer cell growth and survival. Recently pan-KRAS tricomplex inhibitor, which inhibits KRAS ON state, has entered the clinic. Therefore, targeting the KRAS in ON state could be of high clinical value in cancers with defects in G12 mutations and in overcoming resistance. In this regard, we are developing a series of novel pan-KRAS ON state inhibitors. Methods: Fragment screening with SPR and structure-based drug design were used to identify novel pan-KRAS (G12) mutant “ON” state inhibitors. Over 20 scaffolds were synthesised and screened using the AlphaLISA and Nucleotide exchange assay. Binding was assessed using thermal shift assay. To assess in vitro potency and to drive the structure-activity relationship, an AlphaLISA assay that measures the disruption of active KRAS:C-Raf interaction and for the inactive GDP bound state Nucleotide exchange assay was used. The cell-based activity of these inhibitors was assessed by measuring the pERK levels and 2D/3D cell proliferation assays. PK-PD assessment was performed in A427 lung cancer and AGS gastric cancer xenograft models in mice. Results: Based on in vitro screening, we identified a novel series of potent pan-KRAS ON inhibitors targeting (G12) mutations. These early hit compounds demonstrated differential anti-proliferative activity between wild type and G12 mutant KRAS cell lines under 2D and 3D culture conditions. Accordingly, significant reductions in PD biomarker, pERK was demonstrated in KRAS mutant cell lines. PK-PD correlation was also established in a tumor bearing mice models, showing dose-dependent reductions in pERK level. The early data with these compounds show good ADME properties, and oral bioavailability, making them suitable for in vivo profiling and further SAR exploration. Conclusion: Our findings highlight the potential of these novel pan-KRAS ON state inhibitors as promising therapy approach for cancers harbouring KRAS (G12) mutations. Further SAR optimization, mechanistic studies, in vivo studies and toxicity evaluations are warranted to fully establish their efficacy and safety. Citation Format: Chandru Gajendran, Naveen M. Sadhu, Ramachandraiah Gosu, Mohammed Zainuddin, Dhanalakshmi Sivanandhan, Sridharan Rajagopal. Novel small molecule on state inhibitor for GTP bound pan-KRAS (G12) mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4388.