Farnesyltransferase inhibitor LB42708 disables oncogenic RAS signaling and overcomes gefitinib resistance in NSCLC via FTase α-subunit and RAS degradation.

RAS mutations are among the most common oncogenic drivers in human cancers, particularly in non-small cell lung cancer (NSCLC). Direct targeting of RAS proteins remains difficult due to the lack of suitable drug-binding pockets on their surfaces. LB42708 is a potent and selective farnesyltransferase (FTase) inhibitor that disrupts RAS farnesylation and downstream signaling. This study evaluates the anti-tumor effects of LB42708 in KRAS- and HRAS-mutant NSCLC cells, as well as gefitinib-resistant PC9 (PC9GR) cells. LB42708 significantly inhibits the proliferation, migration, invasion, stemness, and clonal growth of RAS-mutant NSCLC cells, while inducing apoptosis and cell cycle arrest. The inhibitory effects are further validated in patient-derived organoids and xenograft models. Mechanistically, LB42708 suppresses FTase activity, reduces RAS protein levels through proteasome-dependent degradation, and induces caspase-3–mediated degradation of the shared α-subunit of FTase and geranylgeranyltransferase-1 (GGTase-1). Combination treatment with LB42708 and the AKT inhibitor AZD5363 (capivasertib) produces synergistic anti-tumor activity in RAS-mutant NSCLC. Moreover, LB42708 enhances the sensitivity of PC9GR cells to gefitinib. Collectively, these findings demonstrate that LB42708, alone or in combination with AZD5363 or gefitinib, represents as a promising therapeutic candidate for NSCLC harboring RAS mutations or resistant to tyrosine kinase inhibitors (TKIs).