The National Institutes of Health (NIH) has announced a funding opportunity for preclinical proof of concept studies targeting rare diseases under the R21 Exploratory/Developmental Research Grant mechanism. This initiative aims to support efficacy studies in established preclinical models for therapeutic agents, including small molecules and biologics, with the goal of advancing projects toward Investigational New Drug (IND) applications. The funding is particularly significant as it addresses the unmet medical needs of approximately 30 million individuals in the U.S. affected by rare diseases, enhancing the likelihood of progressing novel therapies to clinical trials. The total funding available is up to $1,200,000 for FY26, with a maximum budget of $275,000 per two-year project. Interested applicants must submit their letters of intent by May 1, 2025, and can find more information by contacting NIH Grants Information at grantsinfo@nih.gov or visiting the opportunity's webpage at https://grants.nih.gov/grants/guide/rfa-files/RFA-TR-25-002.html.