Influenza is a severe respiratory illness caused by either the influenza A or B virus that results in outbreaks of disease mainly during the winter months.

Currently approved antiviral treatments for influenza are partially effective and prone to viral resistance. Strains of flu virus that are resistant to approved treatments, osteltamivir (Tamiflu®), zanamavir (Relenza™) and Xofluza®, have appeared and in some cases are predominant.

To learn more about influenza, please visit the information page at the Center for Disease Control and Prevention (CDC).


We are developing novel, broad-spectrum influenza antivirals that are specifically designed to be effective against all significant pandemic and seasonal influenza A strains of the influenza virus and to have a high barrier to resistance due to the way they target the virus’ replication machinery. Our uniquely developed molecules target the influenza polymerase, an essential replication enzyme with several highly essential regions common to multiple influenza strains, including pandemic strains.

Program Discovery Preclinical Phase 1 Phase 2a Phase 2b Phase 3
Influenza A CC-42344 PB2 Inhibitor
Discovery Phase complete
Preclinical Phase complete
Phase 1 Phase in progress
Phase 2a Phase not started
Phase 2b Phase not started
Phase 3 Phase not started
Influenza A/B

In collaboration with

Influenza A/B Inhibitor
Discovery Phase complete
Preclinical Phase complete
Phase 1 Phase complete
Phase 2a Phase complete
Phase 2b Phase complete
Phase 3 Phase complete

CC-42344 - Influenza A PB2 Inhibitor

CC-42344, our novel, broad-spectrum, orally administered antiviral investigational candidate for a potential treatment of pandemic and seasonal influenza A infection.  It binds to a highly conserved PB2 site of influenza A polymerase complex and exhibits a novel mechanism of action which inhibits replication. We began enrolling subjects in a Phase 1 study with CC-42344 for the treatment of pandemic and seasonal influenza A in the first quarter of 2022.  The study is being conducted in Australia and is designed to assess the safety, tolerability and pharmacokinetics of CC-42344 with results expected in 2022.

In vitro testing showed CC-42344’s excellent antiviral activity against influenza A strains, including pandemic and seasonal strains, as well as against strains resistant to Tamiflu® and Xofluza®, while also demonstrating favorable pharmacokinetic and safety profiles. CC-42344 inhibits the first step in influenza A’s viral replication by binding to a highly conserved PB2 site of the influenza polymerase complex that is essential to replication. We discovered CC-42344 using our proprietary structure-based drug discovery platform technology.

Influenza A/B Inhibitor

We are engaged in an exclusive license and collaboration agreement with Merck Sharp & Dohme Corp. (“Merck”) to discover and develop certain proprietary influenza A/B antiviral agents.  This class of influenza antivirals targets influenza polymerase complex (PB1:PB2:PA) for the treatment of influenza A and B infections.

Under the terms of the agreement, Merck will fund all research and development for the program, including clinical development, and will be responsible for worldwide commercialization of any products derived from the collaboration. Cocrystal was paid a $4 million license fee and is eligible to receive payments related to designated development, regulatory and sales milestones with the potential to earn up to $156 million, plus undisclosed royalties on product sales.