CIRCLE is a comprehensive resource offering access to data on pharmacological chaperones (PCs) used in the treatment of rare conformational diseases, enriched with chemical information. CIRCLE also provides information on rare conformational diseases, along with their associated pharmaceutical targets. For each target, disease associated-missense variants from the UniProt database, further annotated with chemical, structural, and physical features, are made available. Additionally, the outcomes of efficacy tests—conducted through in vitro assays and/or clinical trials—on individual variants have been systematically compiled from the literature.