Small Molecule Inhibition of MERTK Is Efficacious in Non–Small Cell Lung Cancer Models Independent of Driver Oncogene Status

Treatment of non–small cell lung cancer (NSCLC) has been transformed by targeted therapies directed against molecular aberrations specifically activated within an individual patient's tumor. However, such therapies are currently only available against a small number of such aberrations, and new targets and therapeutics are needed. Our laboratory has previously identified the MERTK receptor tyrosine kinase (RTK) as a potential drug target in multiple cancer types, including NSCLC. We have recently developed UNC2025—the first-in-class small molecule inhibitor targeting MERTK with pharmacokinetic properties sufficient for clinical translation. Here, we utilize this compound to further validate the important emerging biologic functions of MERTK in lung cancer pathogenesis, to establish that MERTK can be effectively targeted by a clinically translatable agent, and to demonstrate that inhibition of MERTK is a valid treatment strategy in a wide variety of NSCLC lines independent of their driver oncogene status, including in lines with an EGFR mutation, a KRAS/NRAS mutation, an RTK fusion, or another or unknown driver oncogene. Biochemically, we report the selectivity of UNC2025 for MERTK, and its inhibition of oncogenic downstream signaling. Functionally, we demonstrate that UNC2025 induces apoptosis of MERTK-dependent NSCLC cell lines, while decreasing colony formation in vitro and tumor xenograft growth in vivo in murine models. These findings provide further evidence for the importance of MERTK in NSCLC, and demonstrate that MERTK inhibition by UNC2025 is a feasible, clinically relevant treatment strategy in a wide variety of NSCLC subtypes, which warrants further investigation in clinical trials. Mol Cancer Ther; 14(9); 2014–22. ©2015 AACR.