Abstract 5599: NXP900, a novel YES1/SRC kinase inhibitor currently in clinical development, blocks YAP1 signaling in NSCLC cell lines

Abstract Background: Most kinase inhibitors exert their anticancer effects by targeting the ATP binding site, either binding and locking an active or inactive kinase conformation, with targeting inactive conformation typically leading to a superior selectivity profile1. NXP900 (eCF506), a highly-potent SRC family kinase (SFK) inhibitor has previously demonstrated high SFK selectivity and the capability to lock the native “closed” conformation (type 1.5), resulting in inhibition of both enzymatic and scaffolding activities2 (IC50 of 0.47 nM against YES1). Conversely, multi-kinase inhibitors dasatinib and bosutinib target the “open” conformation (type 1), thus promoting SFK association with signalling partners3. The aim of this study was to examine the signaling pathways targeted by NXP900, including the Hippo pathway, and unravel potential synergy mechanism of NXP900 with existing targeted therapies against NSCLC. Materials and methods: Cell confluence and viability were determined by automated image analysis of confluence and Presto Blue assay, respectively. NSCLC cells were treated with NXP900 for 24 hours prior to fixation and subsequent immunostaining with anti-YAP, anti-YES1, phalloidin and Hoechst. Images were analysed using ImageJ software. mRNA abundance of SRC, YES1, YAP1, NF2/MERLIN, Cyclin D were quantified utilising TaqMan RT-PCR. Results: NXP900 inhibited cancer cell proliferation of NSCLC cell lines. NXP900 showed dose-dependent decreases in YAP1 and YES1 nuclear localization across all cell lines and prevented SRC phosphorylation. Conclusions: NXP900 prevents YAP1 nuclear localization and cell cycle progression in a panel of NSCLC cell lines, decreasing expression of total YAP1 and YES1. Our data suggests that NXP900, currently in a Phase1 dose escalation study, is an attractive and translatable combination partner that could synergize with existing targeted therapies against NSCLC when the Hippo pathway is dysregulated. 1 C. C. Ayala-Aguilera, T. Valero, A. Lorente-Macias, D. J. Baillache, S. Croke, A. Unciti-Broceta, J Med Chem, 2022, 65, 1047-1131. 2 C. Temps, D. Lietha, E. R. Webb, X. F. Li, J. C. Dawson, M. Muir, K. G. Macleod, T. Valero, A. F. Munro, R. Contreras-Montoya, J. R. Luque-Ortega, C. Fraser, H. Beetham, C. Schoenherr, M. Lopalco, M. J. Arends, M. C. Frame, B. Z. Qian, V. G. Brunton, N. O. Carragher and A. Unciti-Broceta, Cancer Res, 2021, 81, 5438. 3 M. Higuchi, K. Ishiyama, M. Maruoka, R. Kanamori, A. Takaori-Kondo and N. Watanabe, Cell Rep, 2021, 34, 08876. Citation Format: Boback Kaghazchi, Inigo Lanzagorta Calvillo, Ben King, Enrique Poradosu, Neil O Carragher, Asier Unciti-Broceta. NXP900, a novel YES1/SRC kinase inhibitor currently in clinical development, blocks YAP1 signaling in NSCLC cell lines [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 5599.