The ReFRAME library as a comprehensive drug repurposing library and its application to the treatment of cryptosporidiosis

Abstract

The chemical diversity and known safety profiles of drugs previously tested in humans make them a valuable set of compounds to explore potential therapeutic utility in indications outside those originally targeted, especially neglected tropical diseases. This practice of "drug repurposing" has become commonplace in academic and other nonprofit drug-discovery efforts, with the appeal that significantly less time and resources are required to advance a candidate into the clinic. Here, we report a comprehensive open-access, drug repositioning screening set of 12,000 compounds (termed ReFRAME; Repurposing, Focused Rescue, and Accelerated Medchem) that was assembled by combining three widely used commercial drug competitive intelligence databases (Clarivate Integrity, GVK Excelra GoStar, and Citeline Pharmaprojects), together with extensive patent mining of small molecules that have been dosed in humans. To date, 12,000 compounds (∼80% of compounds identified from data mining) have been purchased or synthesized and subsequently plated for screening. To exemplify its utility, this collection was screened against Cryptosporidium spp., a major cause of childhood diarrhea in the developing world, and two active compounds previously tested in humans for other therapeutic indications were identified. Both compounds, VB-201 and a structurally related analog of ASP-7962, were subsequently shown to be efficacious in animal models of Cryptosporidium infection at clinically relevant doses, based on available human doses. In addition, an open-access data portal (https://reframedb.org) has been developed to share ReFRAME screen hits to encourage additional follow-up and maximize the impact of the ReFRAME screening collection.

Keywords: Cryptosporidium; drug discovery; drug repositioning; neglected tropical diseases; phenotypic screening.

Fig. 1.

Overlap of drug entries across all three primary data sources.

Fig. 2.

Distribution of ReFRAME entries across stages of clinical development and disease indications. CV, cardiovascular.

Fig. 3.

ReFRAME library compounds with anticryptosporidial efficacy. (A and C) The structures of oxidized phospholipid VB-201 and TrkA inhibitor ASP-7962. ASP-7962 is a best-guess structure from a phase 2 trial. (B and D) Oocyst shedding trace of mice infected with 1 × 10⁶ oocysts on day 0, then monitored for 2 wk. Line graph data are weight-adjusted mean oocyst counts ± SD (n = 8 over two separate experiments). (B and D, Insets) Bar graphs are oocyst counts ± SEM (n = 4) measured on day 7. These data were assessed with one-way ANOVA. Treatments were compared with the previously investigated compound clofazimine (CFZ) (50 mg/kg BID). AUC, area under the curve. *P < 0.05; ***P < 0.005; ****P < 0.001.