ROS1 is a proto-oncogene that encodes the receptor tyrosine kinase ROS1, which can be aberrantly activated by gene rearrangement to drive tumor cell proliferation, survival, and metastasis. In non-small cell lung cancer (NSCLC), ROS1 rearrangements are detected in 1% to 3% of patients; at the time of diagnosis, 20% to 30% of these patients present with accompanying central nervous system (CNS) metastases. The tyrosine kinase inhibitors (TKIs) crizotinib, entrectinib, lorlatinib and repotrectinib have been used to treat ROS1-positive patients, but have been limited by the emergence of ROS1 resistance mutations, progression of disease in the CNS, or treatment-related adverse events (AEs) associated with off-target kinase inhibition. Novel ROS1 inhibitor NUV-520 (NVL-520) was designed to address these challenges. Across a panel of 335 wild-type kinases, NUV-520 (NVL-520) was highly selective for ROS1; it only inhibited one kinase, ALK, by >50% within 10-fold of its IC50 for ROS1. In recombinant enzyme assays, NUV-520 (NVL-520) inhibited the kinase activity of ROS1 and ROS1 G2032R with Kiapp < 10 nM in the presence of 1 mM ATP. The activity of NUV-520 (NVL-520) against the G2032R mutation is notable. G2032R, referred to as the solvent front mutation, is a frequent acquired resistance mutation to crizotinib and confers resistance to entrectinib and lorlatinib. NUV-520 (NVL-520) also selectively inhibited ROS1 in cells. It inhibited the growth of Ba/F3 cells driven by expression of the CD74-ROS1 fusion with either wild-type kinase domain or drug-resistance mutations G2032R, D2033N, S1986F, or L2026M at IC50 values < 10 nM and with selectivity over structurally related tropomyosin receptor kinase B (TRKB). Avoiding TRKB inhibition is preferred, as TRKB-related CNS adverse events have been reported for CNS-active dual TRK/ROS1 inhibitors entrectinib and repotrectinib. In vivo, NUV-520 (NVL-520) induced regression at well-tolerated doses in patient-derived xenograft (PDX) models of SDC4-ROS1 and CD74-ROS1 G2032R. Furthermore, NUV-520 (NVL-520) was active in a mouse orthotopic brain model of CD74-ROS1 G2032R, reducing tumor size and prolonging survival. In conclusion, NUV-520 (NVL-520) offers a distinct preclinical profile; it is a brain-penetrant and TRKB-sparing small-molecule inhibitor of ROS1 with activity against the frequent drug-resistance mutation G2032R, as well as D2033N, S1986F, and L2026M.

Citation Format: Henry E. Pelish, Anupong Tangpeerachaikul, Nancy E. Kohl, James R. Porter, Matthew D. Shair, Joshua C. Horan. NUV-520 (NVL-520) is a brain-penetrant and highly selective ROS1 inhibitor with antitumor activity against the G2032R solvent front mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1465.