Nicotinamide-based Sirtuin 2 inhibitors as anti-HCMV agents

Human cytomegalovirus (HCMV) is a prevalent herpesvirus pathogen and remains a significant cause for mortality and morbidity in immunocompromised individuals and newborns. Like all viruses, HCMV uses host cellular proteins to facilitate virus replication and spread. Sirtuin 2 (SIRT2) is an NAD⁺-dependent deacetylase with a variety of substrates, including α-tubulin, where acetylation can alter function and stability. We have previously developed small molecule inhibitors targeting SIRT2 and in the current study, we show that two new compounds inhibit SIRT2 activity and also inhibit HCMV replication. The combination of these SIRT2 inhibitors with standard antivirals such as ganciclovir or letermovir resulted in a generally additive profile. Using indirect immunofluorescence, we determined that SIRT2 and SIRT1 expression was reduced over time in compound treated and untreated cells. We also observed SIRT2 and SIRT1 expression was increased in HCMV infected cells, compared to surrounding uninfected cells, regardless of compound treatment. GAPDH expression was stable over time and did not increase in HCMV infected cells, indicating a possible sirtuin-specific mechanism for upregulation of SIRT2 and 1 expression in infected cells. Further investigation is required to better understand the underlying anti-HCMV mechanism of action for our SIRT2 inhibitors and how HCMV infection impacts SIRT2 expression.