Cocrystal Pharma Picks Novel Oral Protease Inhibitor CDI-988 As Norovirus Lead

By Amit Chowdhry • Aug 11, 2023

Cocrystal Pharma – a clinical-stage biopharmaceutical company dedicated to developing novel small-molecule antiviral therapeutics – recently announced the selection of its novel, oral, broad-spectrum 3CL protease inhibitor CDI-988 as a potential oral therapy for norovirus. The randomized, double-blind, placebo-controlled Phase 1 study of CDI-988 is approved by Australia Human Research Ethics Committees (HREC). The study is designed to access the safety, tolerability, and pharmacokinetics of CDI-988.

Without approved treatments or vaccines, norovirus represents a significant unmet medical need. It is considered a highly contagious infection and is the most common cause of acute gastroenteritis, accounting for nearly one in five cases. And according to the Centers for Disease Control and Prevention (CDC), an estimated 685 million cases and 200,000 deaths are attributed to norovirus each year worldwide, with an estimated societal cost of $60 billion. Nearly 200 million cases are reported among children under five years of age, leading to an estimated 50,000 child deaths every year. Among 30 known human norovirus genotypes, nearly 60% of outbreaks are attributable to genogroup II, genotype 4 (GII.4) strains, which have caused periodic human pandemics since 1996.

CDI-988 was explicitly designed and developed as a broad-spectrum antiviral inhibitor using Cocrystal’s proprietary structure-based drug discovery platform technology. And it targets a highly conserved region in the active site of coronaviruses, noroviruses, and other 3CL viral proteases.

Cocrystal previously picked CDI-988 to investigate as an oral treatment for COVID-19 and is approved to conduct a Phase 1 study in Australia, following approval by that country’s Human Research Ethics Committee (HREC). And in recent preclinical in vitro studies, CDI-988 showed potent broad-spectrum antiviral activity against a panel of pandemic GII.4 norovirus proteases and a favorable pharmacokinetic property targeting the gastrointestinal tract.


“In preclinical testing CDI-988 showed significant activity against seven different pandemic strains of norovirus, and we are enthusiastic about developing this compound as a dual broad-spectrum antiviral inhibitor. CDI-988 further validates our proprietary structure-based drug-discovery platform technology and contributes to our robust product pipeline. Our approach is to develop an effective targeted oral treatment for acute and chronic gastroenteritis caused by norovirus, as well as for potential use in addressing future pandemic norovirus outbreaks.”

— Sam Lee, PhD, Cocrystal President and co-CEO

“Given the recent increase in norovirus cases and the lack of approved treatments or vaccines, we continue to see a significant opportunity for our broad-spectrum antiviral CDI-988. There has been a sharp rise in norovirus outbreaks worldwide since 1996 with the emergence of the GII.4 strain. Already in 2023, 13 outbreaks on cruise ships have been reported, the largest number of such infections in a decade.”

— James Martin, Cocrystal CFO and co-CEO