Cocrystal Pharma’s Drug Candidate CC-42344 Shows Strong Antiviral Power Against 2024 H5N1 Avian Flu
Cocrystal’s CC-42344 shows strong antiviral activity against H5N1 avian flu, outperforming Tamiflu in new study.
Breaking News
May 30, 2025
Simantini Singh Deo

Cocrystal Pharma, Inc. recently announced promising results from a virology study showing that its new influenza drug candidate, CC-42344, has strong antiviral effects against the highly pathogenic H5N1 avian influenza A virus. This particular strain of the H5N1 virus was confirmed in a dairy cow in Texas on March 25, 2024, and has since spread widely among U.S. dairy cattle, with a few human cases reported. There is concern that the virus could mutate to allow human-to-human transmission, potentially leading to a pandemic. CC-42344 is an investigational drug designed to treat both pandemic and seasonal influenza infections. It works by targeting a highly conserved active site on the PB2 protein of the influenza virus, blocking the virus’s ability to replicate.
Sam Lee, PhD, President and co-CEO of Cocrystal Pharma, stated, “We are excited to share these H5N1 results that further validate our structure-based drug discovery platform technology and strengthen our position in developing treatments for influenza infection. These important antiviral data along with the favorable safety profile observed in a Phase 1 study support further clinical evaluation of CC-42344 for pandemic and seasonal flu.”
James Martin, CFO and co-CEO of Cocrystal Pharma, added, “We are developing a therapeutic candidate with the potential to address the multibillion-dollar influenza market. Influenza is a major global health concern that may become more challenging to treat as highly pathogenic avian viruses emerge and become resistant to approved antivirals. On average, in the U.S. about 8% of the population contracts influenza each season and influenza is responsible for an estimated $11.2 billion in direct and indirect costs annually.”
Earlier, Cocrystal Pharma shared structural and laboratory data demonstrating how CC-42344 interacts with the H5N1 PB2 protein. The recent study tested CC-42344’s antiviral activity against the H5N1 avian strain influenza A/Texas/37/2024, using Tamiflu® as a comparison. Results showed that CC-42344 was highly effective, with an EC50 of 0.003 µM, making it about 1,000 times more potent than Tamiflu, which had an EC50 of 2.69 µM. CC-42344 is being developed as an oral treatment for avian and seasonal influenza A infections and has so far shown a favorable safety and tolerability profile in initial studies.