PROJECT SUMMARY / ABSTRACT Extension of the funding for this K01 award will support completion of a critical career development goal of a junior investigator in cardiovascular epidemiology and pharmacogenomics, with special emphasis on the role of catechol-O-methyltransferase (COMT) in cardiovascular disease (CVD) and preventive treatment. The extension is warranted because of delays resultING from the COVID-19 pandemic. Despite significant strides in prevention and management, CVD remains a leading cause of death in the United States. Pharmacogenomics, the study of how an individual?s genome affects their treatment response, has expanded our understanding of the pathophysiology and treatment of CVD. However, gene-drug interactions have been difficult to assess in epidemiologic and clinical studies, in part because of the large sample sizes required for genome-wide association studies of these interactions and lack of strong candidate genes. COMT, which encodes a key enzyme in degradation of catecholamines including epinephrine, norepinephrine and catechol estrogen, is a strong candidate gene with plausible physiological links to both CVD and drug metabolism. Through this K01 we demonstrated COMT genetic effects on CVD risk with aspirin and estrogen replacement in the Multiethnic Study of Atherosclerosis, supporting our earlier findings in the Women?s Health Study. Given the widespread use of aspirin for prevention of CVD, it is imperative that we understand the generalizability, mechanism and impact of the COMT locus itself and drugs that may share common molecular pathways and networks with it. This translational research proposal addresses these gaps by conducting a clinical trial to examine effects of native aspirin on platelet function as a function of COMT genotype. As an emerging genetic locus with pleiotropic CVD and drug interaction effects, COMT is an excellent model system to probe the multiple molecular pathways and networks involved in cardiovascular function, disease and treatment and thus guide the development of novel strategies to attenuate CVD risk, and a promising example in which to develop personal expertise in cardiovascular epidemiology, systems biology, clinical trials, and other key career development milestones.