# Dual Inhibition of PB2 and JAK2 for Influenza: A Strategy Combining Antiviral and Host-Directed Immune Modulation

## TL;DR

A new drug called PB05 can both fight influenza viruses and reduce harmful inflammation, offering a dual approach to treating severe flu.

## Contribution

The development of PB05, a dual-target inhibitor that simultaneously targets viral PB2 and host JAK2 to combat influenza and inflammation.

## Key findings

- PB05 showed strong antiviral activity against influenza A viruses with nanomolar EC50 values.
- PB05 reduced pro-inflammatory cytokines like IL-6 and IL-1β by inhibiting JAK–STAT signaling.
- In mice, PB05 lowered lung viral titers and reduced inflammation and tissue damage.

## Abstract

Influenza virus infection remains a major global health burden, with severe disease outcomes driven not only by viral replication but also by excessive host inflammatory responses. Current antiviral therapies predominantly target viral components and fail to adequately control virus-induced hyperinflammation. In this study, we report a dual-target therapeutic strategy integrating direct antiviral activity with host-directed immunomodulation. Using a molecular hybridization approach, we designed and synthesized several dual-target inhibitors simultaneously targeting the influenza virus PB2 cap-binding subunit and host JAK2 kinase. Among them, PB05 emerged as the most promising candidate and was systematically evaluated in vitro and in vivo. PB05 exhibited potent broad-spectrum antiviral activity against influenza A viruses, with nanomolar EC50 values. Mechanistic studies demonstrated that PB05 directly binds to the PB2 cap-binding domain, thereby disrupting viral cap-snatching and RNA synthesis. In parallel, PB05 inhibited JAK–STAT signaling by suppressing STAT2 phosphorylation and downstream ISRE-mediated transcription, leading to a marked reduction in pro-inflammatory cytokine production, including IL-6, IL-1β, and IFN-β, in infected or stimulated immune cells. In a lethal influenza A/PR/8/34 (H1N1) mouse model, oral administration of PB05 at 100 mg/kg (twice daily) markedly decreased lung viral titers, attenuated pulmonary tissue damage and edema, and moderated excessive inflammatory responses. Collectively, these findings identify PB05 as a dual PB2/JAK2 inhibitor that effectively couples antiviral efficacy with immunomodulatory activity, promoting a therapeutic strategy for the treatment of severe influenza and other viral diseases associated with excessive inflammation.