Tolcapone

The dengue virus (DENV) infects approximately 400 million people annually worldwide causing significant morbidity and mortality. Despite advances in understanding the virus life cycle and infectivity, no specific treatment for this disease exists due to the lack of therapeutic drugs. In addition, vaccines available currently are ineffective with severe side effects. Therefore, there is an urgent need for developing therapeutics suitable for effective management of DENV infection. In this study, we adopted a drug repurposing strategy to identify new therapeutic use of existing FDA approved drug molecules to target DENV2 non-structural proteins NS3 and NS5 using computational approaches. We used Drugbank database molecules for virtual screening and multiple docking analysis against a total of four domains, the NS3 protease and helicase domains and NS5 MTase and RdRp domains. Subsequently, MD simulations and MM-PBSA analysis were performed to validate the intrinsic atomic interactions and the binding affinities. Furthermore, the internal dynamics in all four protein domains, in presence of drug molecule binding were assessed using essential dynamics and free energy landscape analyses, which were further coupled with conformational dynamics-based clustering studies and cross-correlation analysis to map the regions that exhibit these structural variations. Our comprehensive analysis identified tolcapone, cefprozil, delavirdine and indinavir as potential inhibitors of NS5 MTase, NS5 RdRp, NS3 protease and NS3 helicase functions, respectively. These high-confidence candidate molecules will be useful for developing effective anti-DENV therapy to combat dengue infection.

Cryptosporidium parvum is an intestinal protozoan parasite, the causative agent of the diarrheal cryptosporidiosis in humans and animals for which fully effective treatments are yet unavailable. The C. parvum genome encodes highly streamlined metabolic pathways, lacking enzymes to synthesize any amino acids de novo. However, it possesses a standalone type A asparagine synthetase (CpAsnA) that catalyzes the ammonia/ATP-dependent synthesis of asparagine from aspartate. Here, we expressed recombinant CpAsnA and characterized its enzyme functional parameters towards aspartate. We screened 5000 bioactive compounds using a thermal shift assay (TSA) and identified 31 hits showing high binding affinity to CpAsnA. Four of the 31 TSA hits exhibited lower micromolar activity against CpAsnA enzyme activity, including XD14, SB225002, histone acetyltransferase inhibitor II (HATi-II) and tolcapone. Among the four CpAsnA inhibitors, three displayed lower micromolar in vitro efficacy against the growth of C. parvum in vitro with satisfactory selectivity indices as primary antiparasitic hits. Our data suggest that CpAsnA merits further investigation as a potential drug target in the parasite.