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. For example, the predominant strain of the 2009 swine influenza pandemic was resistant to Tamiflu.

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 A strains of the influenza virus and to have a high barrier to resistance due to the way they target the virus’s 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/B

In collaboration with

Influenza A/B Inhibitor
Discovery Phase complete
Preclinical Phase in progress
Phase 1 Phase not started
Phase 2a Phase not started
Phase 2b Phase not started
Phase 3 Phase not started
Pandemic Influenza A CC-42344 PB2 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 lead molecule, binds to a highly conserved PB2 site of influenza polymerase complex and exhibits a novel mechanism of action which inhibits replication. CC-42344 has shown excellent antiviral activity against influenza A strains, including avian pandemic strains and Tamiflu® resistant strains, and shows favorable pharmacokinetic and drug resistance profiles. CC-42344 is currently being evaluated in preclinical IND-enabling studies for the treatment of influenza.

Influenza A/B Inhibitor

We are developing another class of influenza antivirals targeting influenza polymerase complex (PB1:PB2:PA) for the treatment of influenza A and B infections. We are currently improving antiviral potency and drug-like properties of the influenza A/B dual inhibitors.

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.

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 upfront 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.