Efficacy and safety of ZX-7101A, an inhibitor of influenza cap-dependent endonuclease, in adults with uncomplicated influenza: a randomized, double-blind, placebo-controlled phase 2/3 trial.

Objectives: To evaluate the efficacy and safety of ZX-7101A: an inhibitor of influenza viral cap-dependent endonuclease, in adults with uncomplicated influenza and explore treatment-emergent resistance.

Methods: We conducted a randomized, double-blind, placebo-controlled, adaptive-design phase 2 and phase 3 studies (ZX-7101A-202) in adults with uncomplicated influenza. Eligible patients were randomized 1:1:1 to receive a single dose of 40 or 80 mg ZX-7101A or placebo, stratified by body weight and baseline composite symptom score. The primary efficacy endpoint was time to alleviation of influenza symptoms (TTAS) in intention-to-treat infected population.

Results: The phase 2 trial suggested significantly shorter TTAS for ZX-7101A compared with placebo: the median TTAS of 40 or 80 mg ZX-7101A groups were 34.7 hours (95% CI, 22.8-43.4; p 0.005) and 45.8 hours (95% CI, 32.0-66.3; p 0.020), compared with 63.6 hours (95% CI, 43.9-93.4) in the placebo group. In the phase 3 trial, the TTAS of both ZX-7101A dose groups was significantly shortened relative to the that of placebo group: the median TTAS was shortened to 48.4 hours (95% CI, 40.5-55.6) for 40 mg group and 39.4 hours (95% CI, 35.8-49.3) for 80 mg group, compared with 62.9 hours (95% CI, 56.4-69.3) for placebo group (p 0.003 and p < 0.001, respectively). In the safety population, ZX-7101A treatment was associated with fewer adverse events, with 41.8% (100/239) in the 40 mg group, 44.2% (106/240) in the 80 mg group, and 53.8% (129/240) in the placebo group. The majority of adverse events were mild or moderate. Emergence of resistance to ZX-7101A through I38T amino acid substitution was detected in 5/278 (1.8%) patients.

Discussion: ZX-7101A was an effective treatment for influenza with a single dose of either 40 mg or 80 mg, with more rapid alleviation of influenza symptoms vs. placebo. No safety concerns were identified with single dose treatment of ZX-7101A.