BI-3406

The SOS1 inhibitor BI-3406 enhanced the efficacy of trametinib and prevented trametinib resistance by targeting spheroid-initiating cells in KRAS-mutated LUAD and COAD cell lines that lacked PIK3CA comutations. Our findings demonstrate that vertical inhibition of RTK/RAS signaling is an effective strategy to prevent therapeutic resistance in KRAS-mutated cancers, but therapeutic efficacy is dependent on both the specific KRAS mutant and underlying comutations. Thus, selection of optimal therapeutic combinations in KRAS-mutated cancers will require a detailed understanding of functional dependencies imposed by allele-specific KRAS mutations.

Finally, we showed that GTP-bound RAS level underwent rebound even in BI3406-sensitive PDOs with no change of KRAS downstream effector genes, thus suggesting upregulation of guanine nucleotide exchange factor as potential cellular adaptation mechanisms to SOS1 inhibition. Taken together, our results show that high SOS1/SOS2 protein expression ratio predicts sensitivity to SOS1 inhibition and support further clinical development of SOS1-targeting agents in CRC.

Single agent SOS1 inhibition had no significant effect in the DhhCre;Nf1 mouse model of plexiform neurofibroma, but pharmacokinetics (PK)-driven combination of selumetinib with BI-3406 significantly improved tumor parameters. Significance Statement Interfering with the RAS-MAPK cascade upstream of MEK, together with MEK inhibition, augment effects of MEK inhibition on neurofibroma volume and tumor macrophages in a preclinical model system. This study emphasizes the critical role of the RAS-MAPK pathway in controlling tumor cell proliferation and the tumor microenvironment in benign neurofibromas.

A set of immuno-oncology reagents, including anti-PD-1/L1, CSF-1R inhibitor (ABSK021) and CD73 inhibitor (ABSK051) were also tested in combination with ABSK071 in vivo using mouse syngeneic models. ABSK071 demonstrated much stronger inhibitory activity than sotorasib and adagrasib against a variety of cell lines harboring KRASG12C, as well as significantly better in vivo anti-tumor efficacy in xenograft models that were less sensitive to sotorasib. Synergistic effects on cell growth inhibition were observed in vitro with ABSK071 in combination with several agents including cetuximab, afatinib, AZD4547, TNO-155, RMC-4630 and BI3406... ABSK071 is a next-generation KRASG12C inhibitor with greater activity and anti-tumor efficacy in vitro and in vivo. It also demonstrated broad synergistic effects with a large set of targeted agents and immuno-oncology agents, indicating its strong potential in combinatory therapy in treating a wider range of KRASG12C-dependent cancers.

The synthesis used the 6- and 7-OH groups of a quinazoline core as anchor points to connect lenalidomide. SOS1 degrader P7 demonstrated superior activity in inhibiting CRC PDO growth with an IC 5 times lower than that of SOS1 inhibitor BI3406. In summary, we developed new SOS1 degraders and demonstrated SOS1 degradation as a feasible therapeutic strategy for KRAS-mutant CRC.

Toxicological investigations revealed that 13c had a lower risk of sudden cardiac death than BI-3406. Overall, 13c has been under evaluation in preclinical trials.

We investigated the anti-tumor efficacy of two KRAS inhibitors BI-3406 (KRAS::SOS1 inhibitor) and sotorasib (KRAS G12C inhibitor) alone or in combination with MEK1/2 inhibitor trametinib and/or PI3K inhibitor buparlisib in seven PDAC cell lines. As well as directly involved in RAF/MEK/ERK pathway and PI3K/AKT pathway affect cell survival. Our current study confirmed inhibition of KRAS and its downstream pathways as a potential novel therapy for PDAC and provides fundamental data for in vivo evaluations.

We describe a comprehensive TME-based stratification of iCCA. Cross-species analysis establishes murine models that align closely to human iCCA for the preclinical testing of combination strategies.

The approved and investigational agents were selected to target specific genetic variants and pathways: KRAS G12C covalent inhibitors (sotorasib and MRTX-1257), RAS pathway inhibitors (BAY-293, BI-3406 and TNO-155), BRAF V600E/K inhibitors (dabrafenib and encorafenib), ABCB1 substrates (paclitaxel, doxorubicin, 5-FU, AZD-1775, and SN-38), and ABCB1 non-substrates (gemcitabine and trametinib)...This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261201500003I.

The most successful combination was TNO-155 plus ipatasertib which resulted in more than 1-log of cell kill in 9 of 20 lines including the 5 KRAS G12C mutant lines. Venetoclax in combination with the RAS pathway inhibitors was active in 4 of the 5 KRAS G12C lines as was the combination of sapanisertib and TNO-155...This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261200800001E.

Our study suggests that pre-existing heterogeneous subclones with epigenetic plasticity contribute to escaping direct KRAS inhibition in pancreatic cancer and provides a new avenue to overcome such resistance by combining KRAS inhibitors with BET inhibitors.

Novel SOS1-directed inhibitors with a broader anticancer coverage such as BAY-293 and BI-3406 inhibit KRAS through the hindrance of SOS1-KRAS interactions...The present investigation tested the cytotoxicity of BAY-293 combinations against a series of Osimertinib-resistant primary NSCLC cell lines using MTT tests and calculation of combination indices according to the Chou-Talalay method...The administration of pan-KRAS inhibitors alone may be limited in vivo by toxicity to normal tissues but made feasible by its use as part of suitable drug combinations. This study shows that BAY-293 combinations are active against NSCLC cells not further amenable to mutated EGFR-directed targeted therapy and results likewise hold relevance for pancreatic and colon cancer.

We identified many secondary KRAS mutations causing resistance to sotorasib, adagrasib or both, in vitro. The differential activities of these two inhibitors depending on the secondary mutations suggest sequential use in some cases. Additionally, switching to BI-3406 plus trametinib might be a useful strategy to overcome acquired resistance due to the secondary Y96D/S mutation.

Combination with the upstream EGFR inhibitor afatinib shows in vivo efficacy against KRAS mutant colorectal tumor cells, demonstrating the utility of BI-3406 to probe SOS1 biology. These findings challenge the dogma that large molecules are required to disrupt challenging PPIs. Instead, a "foot in the door" approach, whereby single atoms or small functional groups placed between key PPI interactions, can lead to potent inhibitors even for challenging PPIs such as SOS1-KRAS.

Importantly, BI-3406 attenuates feedback reactivation induced by MEK inhibitors and thereby enhances sensitivity of KRAS-dependent cancers to MEK inhibition. Combined SOS1 and MEK inhibition represents a novel and effective therapeutic concept to address KRAS-driven tumors.