Targeting ABL1/2 And DDR1 Tyrosine Kinases for Treating NRAS-Mutant Melanoma

Abstract The melanoma incidence continues to rise, and despite new treatments, the disease remains deadly if it has metastasized. Patients with BRAF-mutant melanoma are treated with immune-checkpoint blockade (ICB) and/or with targeted therapy (inhibitors of the MAPK pathway-BRAF, MEK; BRAFi, MEKi). In contrast, NRAS- mutant melanomas, which are understudied and more aggressive, are more difficult to treat as they are not responsive to BRAFi, and MEKi are only modestly effective due to intrinsic and acquired resistance, and thus, are not FDA-approved for this subtype. While tumor-infiltrating lymphocyte (TIL) therapy is an exciting new option, it is expensive, requires hospitalization, has significant side-effects, and is not curative. Thus, less toxic, oral therapies are urgently needed for patients with NRAS-mutant melanomas who cannot tolerate or are refractory to ICB or TIL therapy. We found that ABL1/2 and/or DDR1 tyrosine kinases are activated, and drive MEKi insensitivity in all NRAS-mutant melanoma cell lines examined regardless of the identity of additional primary or acquired mutations. Moreover, ABL1/2 and DDR1 drive BRAF/CRAF stability, homodimerization and subsequent ERK reactivation, and promote melanoma secretion of cytokines. Importantly, targeting ABL1/2 and DDR1 reverses and prevents intrinsic and acquired MEKi resistance, in vivo, in multiple animal models, with no evidence of toxicity. Based on our exciting preliminary data, the central hypothesis of this proposal is that ABL1/2 and DDR1 prevent MEKi sensitivity by impacting cooperating intracellular and extracellular signaling pathways. Our translational goal is to develop new strategies to increase survival for treatment- refractory patients. To test our hypothesis, Aim 1 will define mechanisms by which ABL1/2 and DDR1 promote MEKi insensitivity. Biochemical, molecular biological, and cell biological approaches will be used to test the hypothesis that ABL1/2 and DDR1 promote MEKi resistance by inducing RAF stabilization/dimerization, as well as cytokine secretion that induces an immunosuppressive tumor microenvironment. Aim 2 will define the efficacy of targeting these pathways using xenograft, PDX and GEM models. Successful completion of these studies will allow us to plan a Phase I clinical trial to test the safety and initial efficacy of repurposing ABL/DDR1 anti-leukemia drugs in combination with MEKi and/or RAFi for treatment-refractory NRAS-mutant melanomas.