Despite an initial response to the newly approved RET inhibiting drugs, most RET-positive lung cancers become resistant to these drugs and the cancers relapse. Dr. Watanabe’s project will provide anti-relapse therapeutic strategies for RET-positive lung cancer that target newly identified “drug-tolerant persisters (DTPs)”. DTPs are a small population of cancer cells that do not respond to these drugs and therefore start growing, leading to the relapse of these cancers. The role of DTPs in RET-positive lung cancer is not well understood. Dr. Watanabe proposes therapeutic strategies, such as targeting the Wnt and Hippo signaling pathway to overcome the DTP adaptability and prevent relapse before these cells arise.
Despite advances in the development of RET inhibitors, patients with RET fusions eventually progress. Immunotherapy has been inefficient in patients harboring RET fusions. However, RET fusion proteins themselves may be immunogenic and give rise to an immune response. Dr. Reuben hypothesizes that RET fusions give rise to immunogenic antigens which can be effectively recognized and targeted by engineered T-cells. This project will identify which antigens can elicit an immune response. This information will be used to engineer customized T-cells to gain the ability to recognize those cancer cells that produce these RET fusion proteins. The ultimate goal is to offer new therapeutic alternatives by expanding the possibility of immunotherapy treatment in the overwhelming majority of NSCLC patients harboring RET fusions.
Two possible pathways that seem to be important for resistance to RET inhibitors are the EGFR and MET signaling pathways. Conventional methods of detecting EGFR or MET resistance may not identify many cases where both pathways are involved. In this study, Dr. Patil will use several different laboratory techniques to better detect and define EGFR and MET resistance. He anticipates that the EGFR and MET pathways can be blocked by a newer drug called amivantamab, which is a bi-specific antibody that specifically targets both EGFR and MET.
There is an urgent need to identify new agents or combination therapies to benefit patients whose tumors have developed resistance to current RET inhibitors. Currently, the true extent of RET-dependent (resistance mutations in the RET gene) versus RET-independent mechanisms of resistance is unknown. Dr. Heymach’s team will study mechanisms and biomarkers of RET-independent drug resistance and test different drug combinations to overcome RET inhibitor resistance.
Many RET-positive cancers become resistant to targeted therapy for reasons not clearly based on genetic changes alone. Dr. Drilon predicts that other causes of resistance include (1) chemical changes (in the “epigenome”) that turn cancer-causing genes on or off and (2) changes in how these cancers look under the microscope (“histology”) that affect cancer behavior. Because these changes affect cell states rather than mutations, this resistance is potentially reversible, defining a key opportunity to maintain, restore, and extend sensitivity to potent and specific RET inhibitors.