OBJECTIVES/GOALS: Contrary to current dogma, prior work has suggested that in humans, SNP-determined endothelial cell reduction in CD39 expression associates with a diminished risk for venous thromboembolism. Our objective was to examine the impact of endothelial cell (EC) CD39 expression on arterial thrombosis that replicates human data. METHODS/STUDY POPULATION: We generated a novel CD39 cell-specific conditional knockout mouse line for endothelial cells (EC-cKO: Tie2-Cre+; cd39flox/flox versus WT: Tie2-Cre-; cd39flox/flox). We validated the knockout of expression of CD39 on EC using FACS analysis and measured EC CD39 activity using the Kinase Glo ATP hydrolysis assay on magnetically sorted EC. We then used a standard FeCl3 carotid injury model to evaluate time to arterial thrombosis in vivo by measuring time to occlusion tracked via a Doppler flow probe on the exposed vessel. RESULTS/ANTICIPATED RESULTS: FACS analysis revealed a specific 97% knockout of CD39 expression on EC (p<0.001) but not on other cells within the vasculature. There was also significant reduction in ATP hydrolysis (81%; p=0.019) in EC-cKO mouse EC versus WT. We next examined the time to arterial thrombosis. EC-specific conditional knockout of CD39 exhibited a significant prolongation in time to thrombosis compared to WT (WT: 8.28 minutes +/- 0.82; EC-cKO: 11.92 minutes +/- 1.34; p=0.024). Analysis of carotid blood-flow revealed that EC-cKO and WT mice had similar baseline blood flow velocity (p=0.51), but after vessel injury with FeCl3, EC-cKO mice exhibited a 16% increase maximal flow velocity relative to baseline compared to WT (p<0.001), as well as a 19% increase at 2-minutes post-injury in comparison to EC-WT mice (p<0.001). DISCUSSION/SIGNIFICANCE: Our findings demonstrate that CD39 activity plays a role in modulating arterial thrombosis and blood-flow regulation within the vasculature. These findings exemplify the therapeutic potential of modulating endothelial CD39 activity, as well as the potential for using SNPs within the gene coding for CD39 as a cardiovascular disease marker.