Rabies, a viral encephalitis caused by rabies virus (RABV), is 100% fatal upon the onset of symptoms. Effective post-exposure prophylaxis (PEP) measures are available, but they are often difficult to access in low-income countries. WHO estimates about 59,000 deaths due to rabies globally, and the majority are contributed by developing countries. Hence, developing drugs for the treatment of post-symptomatic rabies is an urgent and unmet demand. It is worth noting that previous efforts regarding antiviral strategies, such as small-interfering RNA, antibodies and small-molecule inhibitors, against the rabies virus have failed to show efficacy in pre-clinical studies, especially when the virus has reached the central nervous system (CNS). Therefore, drug repurposing seems to be an alternative tool for the development of new anti-rabies drugs. We validated and used a high-throughput, FITC-conjugated antibody-based flow cytometry assay to expedite the identification of repurposable new drug candidates against the RABV. The assay was validated using ribavirin and salinomycin as reference compounds, which showed EC50 values of 10.08 µM and 0.07 µM, respectively. We screened a SelleckChem library comprising 3035 FDA-approved compounds against RABV (CVS-11) at 10 µM concentration. Five compounds (clofazimine, tiamulin, difloxacin, harringtonine and homoharringtonine) were active against RABV, with greater than 90% inhibition. Homoharringtonine (HHT) identified in the present study is active against laboratory-adapted RABV (CVS-11) and clinical isolates of RABV, with an average EC50 of 0.3 µM in both BHK-21 and Neuro-2a cell lines and exhibits post-entry inhibition.

Malaria, a life-threatening mosquito-borne disease caused by Plasmodium parasites, continues to pose a significant global health burden. Despite notable progress in combating the disease in recent years, malaria remains prevalent in many regions, particularly in Southeast Asia and most of sub-Saharan Africa, where it claims hundreds of thousands of lives annually. Flavonoids, such as the baicalein class of compounds, are known to have antimalarial properties. In this study, we rationally designed and synthesized a series of baicalein derivatives and identified a lead compound, FNDR-10132, that displayed potent in vitro antimalarial activity against Plasmodium falciparum (P. falciparum), both chloroquine-sensitive (60 nM) and chloroquine-resistant (177 nM) parasites. FNDR-10132 was evaluated for its antimalarial activity in vivo against the chloroquine-resistant strain Plasmodium yoelii N67 in Swiss mice. The oral administration of 100 mg/kg of FNDR-10132 showed 44% parasite suppression on day 4, with a mean survival time of 13.5 ± 2.3 days vs. 8.4 ± 2.3 days of control. Also, FNDR-10132 displayed equivalent activity against the resistant strains of P. falciparum in the 200–300 nM range. This study offers a novel series of antimalarial compounds that could be developed into potent drugs against chloroquine-resistant malarial parasites through further chemistry and DMPK optimization.