The University of Maryland Center of Excellence in Regulatory Science and Innovation (M-CERSI), in collaboration with the Food and Drug Administration (FDA), conducted research and outreach to solicit input from the public, including medical specialists, to better understand the use of certain bulk drug substances nominated for use in compounding by outsourcing facilities under section 503B of the Federal Food, Drug, and Cosmetic Act (the Act). In particular, we were interested in how drugs compounded with these bulk drug substances were used historically, and how they are currently used in clinical practice. The research will assist the FDA in its development of a list of bulk drug substances that outsourcing facilities can use in compounding under section 503B of the Act. Research for each bulk drug substance included a systematic literature review, interviews with medical experts and a survey of healthcare practitioners. The data on findings for the nominated substance, cantharidin, were summarized in the Cantharidin: Summary Report accessible via the UMB Digital Archive.