Monaco, Kelli-Ann, Delach, Scott, Yuan, Jing, Mishina, Yuji, Fordjour, Paul, Labrot, Emma, Parikh, Salonee, Jaskelioff, Mariela, Mathews Griner, Lesley, McKay, Daniel, Aspesi Jr, Peter, Ambrose, Jessi, Mapa, Felipa, Fuller, John, Crawford, Kenneth, Pardee, Gwynn, Widger, Stephania, Hammerman, Peter, Engelman, Jeffrey, Stuart, Darrin, Cooke, Vesselina and Caponigro, Giordano (2020) LXH254, a Potent and Selective ARAF-Sparing Inhibitor of BRAF and CRAF for the Treatment of MAPK-Driven Tumors. Clinical cancer research. ISSN 1557-3265; 1078-0432

Abstract

Purpose: Targeting RAF for anti-tumor therapy in RAS-mutant tumors holds promise. Herein we describe in detail novel properties of the type II RAF inhibitor LXH254. Experimental Design: LXH254 was profiled in biochemical, in vitro, and in vivo assays including examining the activities of the drug in a large panel of cancer-derived cell lines, and a comprehensive set of in vivo models. In addition, activity of LXH254 was assessed in cells where different sets of RAF paralogs were ablated, or that expressed kinase-impaired and dimer-deficient variants of ARAF. Results: We describe an unexpected paralog selectivity of LXH254, which is able to potently inhibit BRAF and CRAF, but has less activity against ARAF. LXH254 was active in models harboring BRAF alterations, including atypical BRAF alterations co-expressed with mutant K/NRAS, and NRAS mutants, but had only modest activity in KRAS mutants. In RAS mutant lines loss of ARAF, but not BRAF or CRAF, sensitized cells to LXH254. ARAF-mediated resistance to LXH254 required both kinase function and dimerization. Higher concentrations of LXH254 were required to inhibit signaling in RAS-mutant cells expressing only ARAF relative to BRAF or CRAF. Moreover, specifically in cells expressing only ARAF, LXH254 caused paradoxical activation of MAPK signaling in a manner similar to dabrafenib. Lastly, in vivo, LXH254 drove complete regressions of isogenic variants of RAS mutant cells lacking ARAF expression, while parental lines were only modestly sensitive. Conclusions: LXH254 is a novel RAF-inhibitor able to inhibit dimerized BRAF and CRAF as well as monomeric BRAF while largely sparing ARAF.

Item Type:	Article
Date Deposited:	18 Mar 2021 00:45
Last Modified:	18 Mar 2021 00:45
URI:	https://oak.novartis.com/id/eprint/42986