PROJECT SUMMARY/ABSTRACT Standardization of data collection for analogous data collected across studies is a valuable way to streamline study design, prevent errors in CRF and EDC development, harmonize and simplify the training of clinical personnel, and facilitate drawing insight across studies for both hypothesis-based and hypothesis-free (e.g., machine learning and artificial intelligence) analysis. The NIH Common Data Elements (CDE) initiative has sought to foster and advance this approach. Congress encouraged continued progress on CDE development and provided guidance recommending NIH develop CDEs for “complex diseases with heterogeneous presentations, such as autoimmune diseases” in the U.S. Senate Committee on Appropriations Explanatory Statement for Departments of Labor, Health and Human Services, and Education, and Related Agencies Appropriations Bill, 2023 – Summary of Budget Estimates and Committee Recommendations. The National Institute of Allergy and Infectious Diseases (NIAID) Autoimmune Diseases Statistical and Clinical Coordinating Center (AD-SCCC) and Clinical Data and Safety Management Center (CDSMC) provide ongoing support for a Division of Allergy, Immunology, and Transplantation (DAIT)-sponsored program to study autoimmune diseases. Although study endpoints are generally disease-specific and must be both clinically relevant and ascertainable to that population, there are some common uses of background and concomitant medications for autoimmune disease where creation of CDEs would benefit study sponsors. Development of new CDEs and case report forms for concomitant immunosuppressive medications would facilitate the efficient capture of treatment information and would improve quality in reporting participant disposition and in the analysis of efficacy for investigational products. This supplement will support the CDSMC in developing and evaluating a Concomitant Immunosuppressive Medications CDE (CIMC) to capture glucocorticoid use in autoimmune disease in study datasets. An interdisciplinary team will review historic approaches to recording immunosuppressive medication use and then develop a candidate CIMC and test it in a simulation environment. With support from the Cancer Data Standards Registry and Repository (caDSR), the project team will ensure that any existing, relevant CDEs registered by other ICs are identified and reused, and the semantics aligned with CDEs from other NIH projects. NCI will also provide support for producing the finalized CDEs in the NIH CDE Governance Template for submission to the NIH for endorsement and subsequent loading into the NIH CDE Repository.