The Role of Pyrazolopyridine Derivatives on Different Steps of Herpes Simplex Virus Type-1 Replicative Cycle.

Herpes simplex virus type-1 (HSV-1) infection causes several disorders, and acyclovir is used as a reference compound. However, resistant strains are commonly observed. Herein, we investigate the effects of -heterocyclic compounds (pyrazolopyridine derivatives), named , , and , on HSV-1 in vitro replication. We show that the 50% effective concentration (EC) values of the compounds , , and were 1.00 ± 0.10, 1.00 ± 0.05, and 0.70 ± 0.10 µM, respectively. These compounds presented high 50% cytotoxic concentration (CC) values, which resulted in a selective index (SI) of 1000, 1000, and 857.1 for , , and , respectively. To gain insight into which step of the HSV-1 replication cycle these molecules would impair, we performed adsorption and penetration inhibition assays and time-of-addition experiments. Our results indicated that and affected viral adsorption, while interfered with the virus replication during its α- and γ-phases and decreased ICP27 content during initial and late events of HSV-1 replication. In addition, we also observed that caused a strong decrease in viral gD content, which was reinforced by in silico calculations that suggested interacts preferentially with the viral complex between a general transcription factor and virion protein (TFIIBc-VP16). In contrast, and interact preferentially in the proteins responsible for the viral adsorption process (nectin-1 and glycoprotein). Thus, our results suggest that the 1-pyrazolo[3,4-]pyridine derivatives inhibit the HSV-1 replicative cycle with a novel mechanism of action, and its scaffold can be used as a template for the synthesis of promising new molecules with antiviral effects, including to reinforce the presented data herein for a limited number of molecules.