Poster 6368: “Discovery of potent, orally bioavailable, SOS1 inhibitors for KRAS-driven tumors”
Abstract
KRAS is an oncogene implicated in a wide variety of tumors (~21% of solid tumors harbor KRAS mutations). KRAS interaction with Guanidine Exchange Factors (GEFs) is crucial for its activation, with SOS1 being the predominant GEF. SOS1 inhibition is thus expected to be an effective strategy for targeting the downstream signaling pathway, resulting in anti-proliferative activity in RAS-driven cancers. We have identified multiple potent and selective SOS1 inhibitors, demonstrating significant reduction of GEF activity in a dose-dependent manner. The lead compounds show anti-proliferative activity across a panel of WT and mutant KRAS cell lines, and are synergistic with MAPK pathway inhibitors including KRASG12C inhibitor Sotorasib. Correspondingly, significant reduction in PD biomarkers, pERK and pAKT is demonstrated in KRAS mutant cell lines. PK-PD correlation is also established in a tumor bearing mice model, with dose-dependent reduction of both pERK and pAKT. The lead compound shows good ADME properties, and is orally bioavailable, making it amenable for further in vivo profiling.
Poster 6369: “Discovery of potent, orally bioavailable, brain penetrant RAD51 inhibitor as an anti-cancer agent”
Abstract
Proliferating cells undergo DNA damage, and this is more pronounced in cancer cells due to their high rate of proliferation. Cancer cells are thus more dependent on the DNA damage repair pathway for their survival. Double-strand breaks (DSBs) are amongst the most severe type of DNA damage and are predominantly repaired by homologous recombination (HR) in an error-free manner. RAD51 is a pivotal recombinase for DSB repair by the HR pathway. Binding of RAD51 with BRCA2 followed by its nuclear translocation, is one of the key repair mechanisms for RAD51 mediated DSB repair. We have identified novel and potent RAD51 inhibitors disrupting the RAD51:BRCA2 interaction, which can address BRCA2 WT patient population. Upon induction of exogenous DNA damage, our compounds inhibit nuclear RAD51 foci formation and demonstrate sustained γH2AX accumulation in the nucleus, suggesting persistent DNA damage. Our orally bioavailable & brain penetrant lead compound shows anti-proliferative activity in multiple BRCA2 WT cancer cell lines across various indications, and excellent synergy when combined with PARP1 inhibitors such as Olaparib. Further, in a wound healing assay, treatment with our lead compound inhibits cell migration in a dose-dependent manner. TNBC patients with extensive brain metastasis have limited treatment options. Thus, a brain penetrant RAD51 inhibitor could provide a novel treatment option in this setting.
