Project Summary Chromosomal rearrangements that generate fusion proteins of echinoderm microtubule-associated protein-like 4 (EML4) and anaplastic lymphoma kinase (ALK), known as EML4-ALK fusions, occur in 3-5% of non-small cell lung cancer (NSCLC) cases. ALK is a validated therapeutic target for ALK rearranged NSCLC patients with four ALK tyrosine kinase inhibitors (TKIs), crizotinib, alectinib, ceritinib and brigatinib, currently approved by the food and drug administration (FDA) for the treatment of ALK rearranged lung cancers. All currently approved ALK inhibitors, as well as those in clinical development, are ATP competitive kinase inhibitors, which carry resistance liabilities. Several mechanisms of resistance to ALK inhibitors have already been described and include both secondary mutations as well as activation of bypass signaling. Therefore, the development of non-TKI based strategies for treatment of ALK rearranged cancers is urgently needed as a complementary therapeutic approach. Here, we propose to explore a fundamentally new approach to abrogating ALK function based on the use of small molecules that can selectively promote its degradation. In particular, we will exploit a recently described approach involving the development of bivalent small molecules called `selective degraders' (also known as PROTACs or degronimids) that induce ubiquitination and subsequent proteosomal degradation of targets of interest. We will build our selective degraders using a dual warhead strategy, with ligands that recruit E3 ligases, such as cereblon (CRBN) or Von Hippel-Lindau (VHL), on one end and ALK binders on the other. Our multidisciplinary research team with expertise in medicinal chemistry and drug development (Gray, Co-PI), and cancer biology and lung cancer translational research (Jänne, Co-PI), has successfully discovered the first small molecule ALK degraders (shown in preliminary data). The goal of this proposal is to develop optimized small molecule degraders of ALK (Aim 1), evaluate their potential to overcome or prevent known mechanisms of resistance (Aim 2), and establish the efficacy of optimized degraders in preclinical murine models (Aim 3). Successful completion of these aims will demonstrate that a new class of compounds may be used to therapeutically target ALK-positive NSCLC, and will provide well-validated compounds that may eventually be translated to clinical trials.