This project aims to develop new therapeutic approaches for RET-positive cancers, focusing on overcoming resistance to currently available RET inhibitors. Dr. Somwar and colleagues will investigate ways to block the growth of lung cancers with altered RET in a pathway called MAPK (mitogen activated kinase), which is involved in many biological processes involving cell growth and survival. MAPK is implicated in developing resistance to RET inhibitors and finding strategies to target this pathway in combination with RET could benefit many patients who have no approved therapy options after tumor reoccurence.
Research Summary
Technical Abstract
RET fusions result from abnormal rearrangements of the kinase domain of RET with other non-essential genes and drive tumorigenesis. These oncogenic chimeric tyrosine kinases are found in approximately 2% of non-small cell lung cancer (NSCLC).Two FDA-approved selective RET inhibitors (selpercatinib and pralsetinib) have shown great response rates in lung cancer patients. However, resistance to RET inhibitors inevitably occurs, limiting therapeutic benefit. Multiple mechanisms of resistance to RET inhibitors have been described, including acquired RET solvent front mutations (G810R/S/C/V), and RET-independent mechanisms of resistance due to amplifications of other receptor tyrosine kinases (RTK) including MET, FGFR1 and ERBB2, and alterations in the RAS-MAPK pathway. Some second-generation RET inhibitors that target secondary RET mutations have been recently developed including vepafestinib (TAS0953/HM06) which is currently being tested in phase I/II clinical trials in the US and Japan for RET fusion positive lung cancer. There is a clinical need to identify mechanisms of resistance to vepafestinib and develop strategies to overcome them.
RET with solvent front mutations, amplification of MET/FGFR1/ERBB2 and RAS-MAPK pathway mutations account for >30% of all resistance mechanisms to first-generation RET drugs, and importantly, all of these alterations are expected to activate the RASMAPK pathway. Therefore, a therapeutic strategy that tackles RAS-MAPK pathway activation is expected to benefit >30% of patients who acquire resistance to first-generation RET drugs. Moreover, given that RET fusions, like all tumors arising from activated RTKs engage the RAS-MPAK pathway for oncogenesis, we believe that many treatment-naïve patients may also benefit from a therapeutic strategy that targets RET and the RAS-MAPK pathway.
Our first goal in this proposal is to simultaneously address resistance due to RAS-MAPK pathway alterations and extending the benefit of first-generation RET drugs by developing a combination therapy strategy involving RET and pan-RAS, MEK1/2 or ERK1/2 inhibitors. Our second goal is to decipher mechanisms by which the transcription factor capicua (CIC) regulate RET-driven tumorigenesis and resistance to RET inhibitors. We will perform transcriptomic, epigenic and proteomic profiling to gain insights into RET-ERK-CIC interaction. Our third goal is to identify and target resistance mechanisms to vepafestinib, so that a therapeutic strategy will be in place for when patients being treated with this drug develop resistance.
Our team includes leaders in the field of lung cancer clinical and translation research who have been at the forefront of lung cancer genomics and therapy, developing state of the art therapeutic strategies. We are well positioned to translate the findings from this study to the clinic within two years. These studies have the potential to benefit more than 30% of lung cancer patients with RET fusions.