New pyridobenothiazolone derivatives display nanomolar pan‐serotype anti‐DENV activity

Dengue virus (DENV) serotypes 1–4 are mosquito-borne flaviviruses that are responsible for significant morbidity and mortality worldwide, particularly in tropical and subtropical regions. Although two vaccines have been approved, their unbalanced efficacy across serotypes poses potential risks for specific populations. There are currently no approved antiviral treatments for DENV, resulting in a clear medical need, especially in endemic countries. In this study, a medicinal chemistry optimization of the pyridobenzothiazolone (PBTZ) derivative 2 was conducted, which resulted in the synthesis of a new series of PBTZ analogues. Compounds 15 and 19 exhibited nanomolar EC50 values against all four DENV serotypes. While new PBTZ analogues did not inhibit DENV polymerase as the first series of PBTZ analogues did, they displayed anti-DENV activity across all time points during time-of-addition assays and demonstrated the capacity to influence the infectivity of newly produced virions without affecting viral RNA synthesis. Compound 19 exhibited an EC50 of 50 nM against DENV-2 and a selectivity index of >2074, representing the most potent PBTZ analogue reported to date, with a significant improvement of over 30-fold compared to the initial hit 2. In vitro pharmacokinetic studies conducted on compound 19 disclosed a promising profile, but with still some suboptimal values.