Cocrystal Pharma Announces Last Subject Dosed in Phase 1b Human Challenge Study Evaluating CDI-988 for Norovirus Prevention and Treatment

Cocrystal completes dosing in a Phase 1b human challenge trial of norovirus candidate CDI-988, with safety data to date showing no serious adverse events.

Rhea-AI Summary

Cocrystal Pharma (COCP) has dosed the last subject in its Phase 1b randomized, double-blind, placebo-controlled human challenge study evaluating oral antiviral candidate CDI-988 for both prevention and treatment of norovirus infection.

The study at Emory University School of Medicine enrolls healthy adults aged 18–49 who are infected with the norovirus GII.2 (Snow Mountain Virus) strain and receive CDI-988 or placebo. The primary endpoint is efficacy versus placebo in reducing the incidence of clinical symptoms, with secondary endpoints including reductions in viral shedding and disease severity, and assessment of safety and pharmacokinetics. No serious adverse events have been reported to date. CDI-988 previously completed a Phase 1 trial in Australia, where it was safe and well tolerated across all doses up to 1200 mg, the dose now used in the Phase 1b study. Preliminary efficacy results are expected in late 2026 or early 2027.

Positive

• Last subject dosed in Phase 1b norovirus human challenge study of CDI-988
• No serious adverse events reported to date across CDI-988 clinical experience
• Phase 1 trial showed CDI-988 was safe and well tolerated up to 1200 mg
• Phase 1b design is randomized, double-blind, placebo-controlled in healthy adults 18–49

Negative

• Preliminary efficacy readout is not expected until late 2026 or early 2027, extending timeline to next value inflection

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Details

Market reaction after Phase 1b dosing completion: COCP +5.08%

$1.17 $1.24 Day Range

$23.89M Market Cap

Following this news, COCP has gained 5.08%, reflecting a notable positive market reaction. Our momentum scanner has triggered 2 alerts so far, indicating moderate trading interest and price volatility. The stock is currently trading at $1.24. Trading volume is elevated at 2.5x the average, suggesting notable buying interest.

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Market Context

The prior $5.0 million private placement on Aug 03 supported CDI-988 advancement and preceded a 14.6...

Analysis

The prior $5.0 million private placement on Aug 03 supported CDI-988 advancement and preceded a 14.63% 24-hour gain; this update marked completion of dosing in the same Phase 1b program.

Key Figures

Prior safe dose: 1200 mg Eligible age range: 18-49 years Preliminary results timing: Late 2026 or early 2027

Prior safe dose

1200 mg

Phase 1 dose-escalation study and ongoing Phase 1b challenge study

Eligible age range

18-49 years

Healthy subjects in the Phase 1b challenge study

Preliminary results timing

Late 2026 or early 2027

Expected preliminary efficacy results

Historical Context

2 past events · Latest: Aug 03

2 events

1. Aug 03

   Private placement

   24h Move

   +14.6%

   $5.0 million placement supported CDI-988 advancement and Phase 1b data expected in 2026

2. May 15

   Earnings report

   24h Move

   -4.8%

   CDI-988 Phase 1b cohorts were enrolling while quarterly results reported a $2.3 million loss

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

direct-acting antiviral, placebo-controlled, viral shedding, pharmacokinetic

4 terms

direct-acting antiviral medical

"first clinical trial of a direct-acting antiviral specifically targeting norovirus"

A direct-acting antiviral is a medicine that attacks specific parts of a virus to stop it from copying itself, rather than boosting the body's general immune response. Investors care because these targeted drugs can produce faster, more reliable cures, shaping treatment demand, pricing power, regulatory approval prospects, patent life and competitive dynamics in pharmaceutical markets—much like a precision tool replacing a blunt instrument in a workshop.

placebo-controlled medical

"The Phase 1b randomized, double-blind, placebo-controlled study"

"Placebo-controlled" describes a testing method where one group receives the actual treatment or intervention, while another group receives a harmless, inactive version called a placebo. This approach helps determine whether the real treatment has genuine effects beyond psychological expectations. For investors, understanding this ensures confidence that reported benefits are real and not influenced by bias or false perceptions.

viral shedding medical

"Secondary endpoints include reduction of viral shedding and disease severity"

Viral shedding is the process by which an infected person or animal releases virus particles into the environment, through actions like coughing, sneezing, breathing, or bodily fluids. It matters to investors because the amount and duration of shedding affect how contagious a disease is, the public health response, and regulatory safety assessments for vaccines or therapies; think of shedding like seeds being scattered, determining how far and easily an infection can spread.

pharmacokinetic medical

"as well as safety and pharmacokinetic profiles"

Pharmacokinetic describes how a drug moves through and leaves the body — how it is absorbed, spread to tissues, broken down and excreted — like tracking a package from pickup to delivery and disposal. For investors, these properties determine effective dose, safety risks, how often a medicine must be taken, and how reliably it works, which in turn influence clinical trial success, regulatory approval chances, production complexity and a drug’s commercial value.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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No serious adverse events reported to date

Preliminary efficacy results expected in late 2026 or early 2027

MIAMI, Fla. And BOTHELL, Wash., Sept. 09, 2026 (GLOBE NEWSWIRE) -- Cocrystal Pharma, Inc. (Nasdaq: COCP) ("Cocrystal" or the "Company"), a biotechnology company developing novel therapeutics to meet the growing global need for effective, safe antiviral treatments, today announced 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.

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. 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.

“Completion of this critical milestone brings us closer to addressing one of the most pressing unmet needs in infectious disease,” said James Sapirstein, Chief Executive Officer of Cocrystal Pharma. “Norovirus imposes an enormous burden on patients and health systems, with particular risk in settings such as hospitals, nursing homes, cruise ships, schools and military facilities. We look forward to reporting preliminary results near the end of 2026 or early 2027 and to advancing CDI-988 as a potential first-in-class oral antiviral for norovirus.”

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. The primary endpoint is efficacy versus placebo in reducing the incidence of clinical symptoms. Secondary endpoints include reduction of viral shedding and disease severity, as well as safety and pharmacokinetic profiles.

“Reaching last-subject-dosed in the first clinical trial of a direct-acting antiviral specifically targeting norovirus is a significant achievement for our team,” said Sam Lee, Ph.D., President and Chief Scientific Officer of Cocrystal Pharma. “The efficacy and safety data from this study are expected to provide a strong rationale for further clinical advancement of CDI-988.”

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. The 1200 mg dose, established as safe in the earlier Phase 1 dose-escalation study in healthy volunteers conducted in Australia, is the dose being administered to healthy volunteers who are then infected with norovirus in the ongoing Phase 1b challenge study.

About Norovirus

With an estimated 685 million global cases annually and a $60 billion worldwide economic impact, norovirus represents one of healthcare's most pressing unmet needs. In the U.S., noroviruses are responsible for an estimated 21 million infections annually, including 109,000 hospitalizations, 465,000 emergency department visits and an estimated 900 deaths. The annual burden of norovirus to the U.S. is estimated at $10.6 billion. Noroviruses are responsible for up to 1.1 million hospitalizations and 218,000 deaths annually in children in the developing world.

About Cocrystal Pharma, Inc.

Cocrystal Pharma, Inc. is 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. Cocrystal employs unique structure-based technologies to create viable antiviral drugs. For more information, visit www.cocrystalpharma.com.

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including statements regarding the advancing of CDI-988 as a potential first-in-class oral antiviral for norovirus. Words such as "believe," "may," "estimate," "continue," "anticipate," "intend," "should," "plan," "could," "target," "potential," "is likely," "will," and "expect," as they relate to the Company, are intended to identify forward-looking statements. We have based these forward-looking statements largely on our current expectations and projections about future events. Some or all of the events anticipated by these forward-looking statements may not occur. Important factors that could cause actual results to differ from those in the forward-looking statements include, but are not limited to, the risks and uncertainties arising from inflation, affordability, the possibility of a recession, increases or other developments with respect to interest rates, uncertainty surrounding the impacts arising from imposed and threatened tariffs and developments with respect thereto, and wars and geopolitical conflicts including those in Ukraine and with Iran on our Company, our collaboration partners, and on the U.S. and global economies, including manufacturing and research delays arising from raw materials and labor shortages, supply chain disruptions and other business interruptions including any adverse impacts on our ability to obtain raw materials and test animals as well as similar problems with our vendors our and our collaboration partners’ technology and software performing as expected, financial difficulties experienced by certain partners, risks arising from the research into a related virus was not done in animals and was necessarily early stage, the results of future preclinical and clinical trials, general risks arising from clinical trials, receipt of regulatory approvals, regulatory changes and potential litigation challenging initiatives and actions taken by the Trump Administration which could, among other things, result in delays in regulatory approvals or limit access to federal funding for our programs, development of effective treatments and/or vaccines by competitors, including as part of the programs financed by the U.S. government, potential mutations in a virus we are targeting which may result in variants that are resistant to a product candidate we develop, and our liquidity. Further information on our risk factors is contained in our filings with the SEC, including the “Risk Factors” in Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2025. Any forward-looking statement made by us herein speaks only as of the date on which it is made. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.

Investor Contact:
Nicolas Johnson
Russo Partners
nic.johnson@russopartnersllc.com
(303) 482-6405

Media Contact:
David Schull
Russo Partners
david.schull@russopartnersllc.com
(858) 717-2310

FAQ

What is CDI-988 and how is it intended to work against norovirus?

CDI-988 is described as the first oral antiviral drug candidate developed for norovirus acute gastroenteritis. It is designed to inhibit viral replication in all known norovirus strains, aiming to serve as both a preventive and treatment option for norovirus infections.

What are the key endpoints of the Phase 1b human challenge study?

The primary endpoint is efficacy versus placebo in reducing the incidence of clinical symptoms. Secondary endpoints include reduction of viral shedding, reduction of disease severity, and assessment of safety and pharmacokinetic profiles.

Who is being enrolled in the Phase 1b study and what virus strain is used?

The Phase 1b study enrolls healthy subjects aged 18–49 who are infected with the norovirus GII.2 (Snow Mountain Virus) strain and then orally administered CDI-988 or placebo.

What dosing information is available for CDI-988 from earlier studies?

In a prior Phase 1 dose-escalation study in healthy volunteers in Australia, CDI-988 demonstrated favorable safety and tolerability across all dose levels, including the highest dose of 1200 mg. This 1200 mg dose was established as safe and is the dose being administered in the ongoing Phase 1b challenge study.

When are results from the Phase 1b study expected?

Preliminary efficacy and safety data from the Phase 1b human challenge study of CDI-988 are expected near the end of 2026 or early 2027, as stated by the company.