Overcoming Resistance Mechanisms to Anaplastic Lymphoma Kinase Inhibitors

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Project Summary Non-small cell lung cancers (NSCLC) harboring oncogenic anaplastic lymphoma kinase (ALK) gene rearrangements (i.e., ‘ALK+’) comprise a distinct molecular subset of lung cancer with marked sensitivity to ALK tyrosine kinase inhibitors (TKIs). While ALK TKIs are initially highly effective, acquired drug resistance remains a fundamental challenge that limits clinical benefit and causes disease relapse in most patients. We and others have characterized mechanisms of resistance, in particular so-called “on-target” resistance mediated by secondary acquired ALK kinase domain mutations that can be overcome with more potent next-generation (2nd- or 3rd-generation) inhibitors. In recent years, the standard treatment paradigm for patients diagnosed with advanced ALK+ lung cancers has shifted from sequential therapy using the 1st-generation ALK TKI crizotinib followed by next-generation TKIs, to initial therapy using a next-generation ALK TKI upfront. Our preliminary data indicate that off-target (i.e., ALK-independent) resistance mechanisms are prevalent following next-generation ALK TKIs. Yet, the spectrum of off-target resistance mechanisms and strategies to overcome these remain poorly understood, presenting a barrier to the development of treatment options for these patients. The overarching objective of the proposed research is to identify and develop complementary, mechanism-informed and mechanism-agnostic approaches for overcoming off-target resistance to next-generation ALK TKIs. We will use comprehensive genomic and non-genomic assessment of an expanded cohort of patient tumor specimens to determine the clinical spectrum of off-target resistance mechanisms after first-line use of next-generation ALK TKIs, and we will develop new methods for identifying patients with bypass-mediated resistance most likely to benefit from rationally designed combination therapies. Using ALK TKI-resistant tumor cell lines derived from patient biopsies, we will screen for epigenetic mechanisms that drive resistance independent of canonical bypass signaling pathways, with initial studies focused on defining the role of the transcriptional co-activator p300/CBP as a novel driver of off-target ALK TKI resistance and therapeutic target. These efforts will enable patient-specific, mechanism-informed therapeutic strategies. In parallel, we will develop a mechanism-agnostic approach that leverages ALK as a tumor-specific “neoantigen” whose expression is maintained in resistant tumors. Using T cell-based functional screens, we will identify ALK-reactive T cell receptors (TCRs) that are capable of recognizing resistant ALK+ NSCLCs. This will provide the foundation for engineering ALK TCR adoptive cellular therapy as a TKI-orthogonal, immune-based approach for overcoming resistance. Collectively, the proposed studies will provide a comprehensive understanding of resistance to next-generation ALK TKIs and pave the way for the development of new therapeutic strategies that can effectively overcome most of off-target resistance in the clinic, ultimately improving and prolonging the lives of patients with advanced ALK+ lung cancers.