The purpose of this phased Notice of Funding Opportunity (NOFO) is to create a pipeline to accelerate the development and early validation of predictive tools and/or biomarkers to inform individual-level treatment selection among two or more existing therapeutics for depression. This phased inter-agency program will be milestone-based and provide support from multi-disciplinary teams to address scientific, technical, clinical, regulatory, and commercialization requirements. In the first phase (UG3), investigators are expected to identify potential tools and/or biomarker(s) that can predict whether a patient will differentially respond to one well-established depression treatment versus another. This could be accomplished using secondary analysis of data from completed clinical trials or using real-world clinical data, or by conducting small, efficient pilot feasibility studies to assess promising new tools or biomarkers to predict individual treatment response to a specific therapeutic for depression. In the second phase (UH3), investigators will conduct independent, prospective clinical trials to initially validate the utility of the tool/biomarker for predicting differential response to established treatments for depression. The overall goal of this NOFO is to support the testing of various tools/biomarkers as predictors of response to well-established depression treatments and halt the development of those tools that do not meet sufficient performance characteristics to justify further testing. Ultimately, tools that are successful in early-stage studies could be further evaluated for future use in decision-making in clinical practice settings.