Project Summary/Abstract Migraine is a debilitating pain condition and ranks globally in the top five for years lived with disability. Approximately 15% of the general US population experiences migraine, with women afflicted approximately twice as often as men. Migraine is currently diagnosed by a qualifying recurrence of symptoms, including aura, formally codified by the International Classification of Headache Disorders. However, the lack of established, explicitly quantitative biomarkers for migraine, especially causal biomarkers, is widely viewed as a critical impediment to optimizing and developing therapeutic strategies, and to advancing understanding of migraine pathophysiology. Our preliminary data suggest that such causal plasma-based biomarkers exist and can be identified. In addition, formally diagnosed migraine may present with or without aura and a diversity of other symptoms, all equally qualifying for migraine, suggesting heterogeneity in migraine etiology. Thus, a second but equally important goal for a quantitative migraine biomarker, especially a causal biomarker, is to resolve possible subclasses of migraine, which may be used in treatment decisions. We propose an investigation that is responsive to PAR-19-315 through a goal of identifying and validating plasma-based biomarkers diagnostic of migraine and its potential subclasses. During the R61 phase of the research, we will measure a comprehensive panel of >1300 plasma metabolites and 92 vascular related proteins among three groups of women from the Women’s Genome Health Study (WGHS): those with active migraine, non-migraine headache, and no headache symptoms. In these data, we will use state-of-the-art statistical modeling to identify plasma-based metabolite and protein signatures of migraine that formally discriminate individuals with active migraine from those never reporting headache and also those reporting non-migraine headache as well as among sub-classes of migraine defined by specific migraine symptoms, e.g. aura. Using existing genetic data, we will apply a genetic instrumental variable method termed “Mendelian Randomization” to assess whether these metabolite signatures may have causal effects on migraine. During the R33 phase, we will develop and apply a validated assay(s) targeting the metabolite(s) and/or protein(s) identified in the R61 to perform an initial validation study our biomarker signature within a new cohort of men and women recruited for this project. We anticipate that findings from the proposed research have the potential to help refine the analysis of response in clinical trials, optimize current prophylactic strategies, suggest new therapeutics, and resolve uncertainty in assignment of diagnostic aura status and other potential sub-classes of migraine.