Cocrystal presents CDI-988 norovirus data at ICAR 2026

Cocrystal Pharma, Inc. (Nasdaq: COCP) said on April 30, 2026 that the mechanism of action and clinical progress of its oral protease inhibitor CDI-988 were presented that day at the 39th International Conference on Antiviral Research (ICAR 2026) in Prague, Czech Republic. The oral presentation, titled "First Oral Direct-Acting Antiviral CDI-988 for Norovirus Infection Prevention and Treatment: Novel Mechanism of Action and Phase 1 Study Results," was delivered by Sam Lee, Ph.D., President and co-Chief Executive Officer.

The Phase 1b study

The ongoing Phase 1b randomized, double-blind, placebo-controlled challenge study is conducted at Emory University School of Medicine. The study is designed to enroll up to 40 healthy adults, ages 18 to 49, in staged cohorts. That is small, and so far the only cohort enrolled is one that tests the virus, not the drug. The release says the first, stage 1 infectivity cohort is fully enrolled. That cohort will establish the infectivity rate of the GII.2 (Snow Mountain Virus) challenge inoculum, which the company calls a critical step in validating infectivity in the study cohorts.

Prevention and treatment cohorts will follow. In those cohorts, CDI-988 is given at 1,200 mg twice daily for five days. The primary efficacy endpoint is a reduction in the incidence of clinical symptoms. Secondary endpoints include reduction in viral shedding, disease severity, safety and pharmacokinetics. No efficacy result from this study has been reported.

In the release, Dr. Lee says: "Multiple norovirus vaccine clinical studies have been initiated over the past decade, yet none have led to an approval." He adds that CDI-988 is designed to target a highly conserved region of the 3CL protease across all known norovirus strains, including GII.4 and the re-emerging GII.17 variants, as well as all coronaviruses.

Earlier results

The release describes a completed randomized, double-blind, placebo-controlled single- and multiple-ascending dose Phase 1 study in healthy adults. CDI-988 was generally safe and well tolerated across doses up to 1,200 mg. Headache was the most common treatment-emergent adverse event, and no serious adverse events were reported. The release gives no event rates, patient numbers or comparison with placebo, and a safety study in healthy volunteers says nothing about whether the drug works against norovirus. The company says a no-observed adverse effect level of 1,000 mg/kg in GLP toxicology studies supports further clinical development in norovirus.

Preclinical studies showed favorable gastrointestinal-targeted pharmacokinetics at the site of norovirus infection. The release also says CDI-988 showed potent antiviral activity in GII.4-infected human enteronoid model systems, which are lab models without patients.

The disease and the designation

The release says norovirus is the leading cause of acute gastroenteritis across all age groups and geographic regions. It estimates 685 million cases and 200,000 deaths worldwide each year, with an approximate $60 billion economic impact. In the United States, it cites 21 million infections annually and 900 deaths.

The U.S. Food and Drug Administration has granted CDI-988 Fast Track designation for the treatment and prophylaxis of norovirus infection. The release says the designation underscores the lack of approved therapies. It is a regulatory designation, not a finding that the drug works.

Financial position

The XBRL data in the company's annual report show research and development expense of $5.1 million for the year ended December 31, 2025, compared with $12.5 million for 2024. The net loss was $8.8 million in 2025, compared with $17.5 million in 2024. Cash used in operations was $8.2 million in 2025, compared with $16.5 million in 2024.

Cash and cash equivalents were $7.0 million at December 31, 2025, compared with $9.9 million at December 31, 2024. The cash balance was smaller than the $8.2 million used in operations in 2025, and the release gives no balance after that date.

What comes next

The release says the fully enrolled stage 1 infectivity cohort will be followed by prevention and treatment cohorts. It does not give dates for those cohorts, and it does not give a date for topline data. The drug cannot be tested until the challenge virus is shown to infect volunteers, and the release's risk language lists the results of current and future studies and any adverse developments among the risks.

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