RAS Inhibitor RMC-7977 Blocks Vascular Overgrowth of NRASQ61R Mutant Endothelial Cells.

RAS mutations occur in patients with several types of vascular anomalies, but effective treatments remain limited. To address this need, we evaluated the RAS (ON) multi-selective inhibitor RMC-7977 in human endothelial cells (ECs) expressing the NRASQ61R mutation found in kaposiform lymphangiomatosis (KLA). RMC-7977 was evaluated using in vitro and in vivo models. Doxycycline-inducible NRASWT and NRASQ61R human ECs were treated with RMC-7977 (3.12-100 nM) or vehicle. We assessed signalling pathways, proliferation, migration, morphology, and angiopoietin-2 (ANG-2) production. NRASQ61R ECs in a 3D angiogenesis assay were also treated with RMC-7977. For in vivo studies, NRASQ61R ECs were injected into flanks of nude mice on a doxycycline diet to generate xenografts. Mice received oral RMC-7977 or vehicle, and xenografts were collected after 11 days. RMC-7977 inhibited NRASQ61R-induced ERK phosphorylation and reduced proliferation, migration, spindle-like morphology, and ANG-2 production in a dose-dependent manner. RMC-7977 reduced vascular area in the angiogenesis assay. In vivo, RMC-7977 reduced xenograft weight, vascular area, and p-ERK staining. Overall, RMC-7977 suppressed NRASQ61R-mediated signalling, aberrant EC behaviour, and ANG-2 production in vitro and reduced vascular overgrowth in angiogenesis assays and mouse xenografts. Therefore, RMC-7977 may be a promising therapeutic candidate for RAS-driven vascular anomalies, including KLA.