Cocrystal Pharma completes dosing in norovirus challenge study of CDI-988

Cocrystal Pharma, Inc. announced on September 9, 2026 that the last subject has been dosed in its Phase 1b norovirus challenge study (NCT07198139) evaluating CDI-988 as both a preventive and treatment for norovirus infections.¹ The company said CDI-988 is the first oral antiviral drug candidate developed for norovirus acute gastroenteritis and is designed to inhibit viral replication in all known norovirus strains.¹

The drug had earlier moved through a separate stage of testing. CDI-988 completed a Phase 1 clinical trial in Australia, with data showing CDI-988 was safe and well tolerated in humans, with no serious adverse events reported.¹ In the current study, the Phase 1b randomized, double-blind, placebo-controlled study was conducted at Emory University School of Medicine and enrolled healthy subjects ages 18-49, who were infected with the norovirus GII.2 (Snow Mountain Virus) strain and orally administered CDI-988 or placebo.¹

The trial design specifies that the primary endpoint is efficacy versus placebo in reducing the incidence of clinical symptoms, while secondary endpoints include reduction of viral shedding and disease severity, as well as safety and pharmacokinetic profiles.¹

On dosing, the release noted CDI-988 previously demonstrated favorable safety and tolerability in a Phase 1 study across all dose levels, including the highest dose of 1200 mg administered, and that 1200 mg dose is the one being administered to healthy volunteers who are then infected with norovirus in the ongoing Phase 1b challenge study.¹

Cocrystal said preliminary efficacy results are expected in late 2026 or early 2027.¹ The company describes itself as a clinical-stage biotechnology company discovering and developing novel antiviral therapeutics that target the replication process of noroviruses, influenza viruses, coronaviruses (including SARS-CoV-2), and hepatitis C viruses.¹