An Expert Report on GP-681 (Suraxavir Marboxil): A Novel Antiviral Agent for Influenza

1. Executive Summary

GP-681, also known as Suraxavir Marboxil, is an orally administered prodrug antiviral agent developed for the treatment of acute uncomplicated influenza. Its active metabolite, GP1707D07, targets the polymerase acidic (PA) protein of the influenza virus, specifically inhibiting its cap-dependent endonuclease activity, a critical step in viral replication.[1] Clinical development, primarily conducted by Jiangxi Qingfeng in China, has progressed through Phase 3 trials.[4]

Phase 2 and Phase 3 studies have demonstrated that a single oral dose of Suraxavir Marboxil (notably 40 mg) significantly reduces the time to alleviation of influenza symptoms (TTAS) and accelerates viral load decline in patients with acute uncomplicated influenza, predominantly influenza B in the Phase 2 trial and a mix including influenza A subtypes in Phase 3.[1] The single-dose regimen presents a notable advantage for patient compliance and ease of administration in an acute setting.

The pharmacokinetic profile of GP1707D07 is characterized by a relatively long half-life (58-76 hours), supporting the single-dose efficacy, and primary metabolism via CYP3A4.[3] While co-administration with strong CYP3A4 inhibitors like itraconazole increases exposure to GP1707D07, initial studies suggest this may not warrant clinical dose adjustments, though this implies a wide therapeutic window.[2] The drug is predominantly excreted in feces.[3] Suraxavir Marboxil has shown a good safety and tolerability profile, with adverse events generally mild to moderate and comparable to placebo; diarrhea is the most commonly reported adverse event.[1] A low incidence of acquired drug resistance, specifically the PA I38T mutation in influenza A subtypes, has been observed in Phase 3 trials.[5]