New Pyridobenothiazolone Derivatives Display Nanomolar Pan-Serotype Anti-Dengue Virus 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. Herein, a medicinal chemistry optimization of the pyridobenzothiazolone (PBTZ) derivative 2 is conducted, which results in the synthesis of a new series of PBTZ analogues. Compounds 15 and 19 exhibit nanomolar EC₅₀ values against all four DENV serotypes. While new PBTZ analogues do not inhibit DENV polymerase as the first series of PBTZ analogues do, they display anti-DENV activity across all time points during time-of-addition assays and demonstrate the capacity to influence the infectivity of newly produced virions without affecting viral RNA synthesis. Compound 19 exhibits 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 disclose a promising profile, but with still some suboptimal values.