BME PhD Dissertation Defense: Alanna M. Farrell Colón

Title: "Drug-induced endothelial barrier dysfunction: Mechanisms and modeling of BCR-ABL tyrosine kinase inhibitor vascular toxicity"

Advisory Committee: Christopher S. Chen, PhD, MD – BME (Research Advisor) Jeroen Eyckmans, PhD – BME (Chair) Shannon Stott, PhD – BME Iris Z. Jaffe, PhD, MD – Tuft’s Medical School Richard Travers, PhD, MD – Tuft’s Medical School

Abstract: Chronic Myeloid Leukemia (CML) treatment has been transformed by BCR-ABL tyrosine kinase inhibitors (TKIs), yet several agents within this drug class are associated with significant vascular toxicities, including pleural effusion, pulmonary edema, pulmonary arterial hypertension, and arterial occlusive disease. Vascular toxicity profiles vary substantially across BCR-ABL TKIs, suggesting that distinct off-target effects contribute to endothelial dysfunction. The direct effects of these agents on endothelial barrier integrity and the mechanisms underlying vascular toxicity remain incompletely understood. To address this, we leveraged a human engineered microvessel (hEMV) model and complementary endothelial assays to first characterize class-wide vascular toxicity across clinically relevant BCR-ABL TKIs and then interrogated the mechanisms underlying drug-induced endothelial barrier dysfunction. hEMVs revealed substantial heterogeneity in vascular toxicity across seven clinically relevant BCR-ABL TKIs and identified dasatinib as inducing the most pronounced endothelial barrier dysfunction. Subsequent mechanistic investigation demonstrated that dasatinib-induced dysfunction is associated with disruption of adherens junction organization, focal adhesion architecture, actin cytoskeletal organization, and Src/FAK and RhoA/ROCK signaling, supporting a model in which dasatinib disrupts Src- and ROCK-dependent coordination between endothelial adhesions and the actin cytoskeleton. Importantly, selective ROCK2 inhibition with belumosudil mitigated multiple manifestations of dasatinib-induced endothelial leak in engineered human microvessels and in vivo. Collectively, this work establishes hEMVs as a translationally relevant platform for studying drug-induced vascular toxicity, provides mechanistic insight into dasatinib-induced endothelial dysfunction, and identifies selective ROCK2 inhibition as a potential therapeutic mitigation strategy.