Cidara Therapeutics has received Breakthrough Therapy designation from the US Food and Drug Administration (FDA) for its investigational drug CD388, developed for the prevention of influenza A and B in adults and adolescents at increased risk of flu complications. The designation comes in addition to Fast Track status previously granted by the FDA.

The agency’s decision recognises early evidence that CD388 may provide substantial improvement over existing preventive options for high-risk groups, including individuals with immune deficiency, those for whom vaccines are less effective, and people for whom vaccination is contraindicated.

Jeffrey Stein, president and chief executive officer, Cidara Therapeutics, said: “This Breakthrough Therapy designation, in addition to the previously awarded Fast Track designation, underscores the importance of CD388 as a potential new non-vaccine prophylactic for seasonal influenza. Individuals who have chronic medical conditions, advanced age, or are immune compromised may not be adequately protected by current vaccines, leaving them at higher risk for infection and complications from flu.

“As a long-acting prophylactic drug, CD388’s activity does not rely on an immune response, making it a potential prevention option for high-risk individuals as well as those for whom vaccines are contraindicated. We look forward to advancing CD388 through our ongoing Phase 3 Anchor trial and submission of a Biologic License Application.”

Breakthrough Therapy designation is intended to expedite the development and review of medicines that treat serious or life-threatening conditions and show potential for substantial improvement over available therapies. Benefits include eligibility for priority review, rolling submission of application sections and greater engagement with senior FDA officials during development.

The designation was based on results from the Phase 2b Navigate study, which demonstrated statistically significant prevention of seasonal influenza in healthy, unvaccinated adults aged 18–64. Top line data from the trial were announced in June 2025, with additional findings scheduled for presentation at scientific meetings later this month.

Cidara has already initiated the Phase 3 Anchor study to assess the safety and efficacy of CD388 in populations at high risk for complications of influenza. The trial began six months ahead of schedule and will include both generally healthy adults over 65 and other high-risk groups with specific comorbidities or immune compromise.

Cidara’s Cloudbreak platform is designed to create drug-Fc conjugate (DFC) therapeutics that combine the precision of targeted small molecules with the durability and immune engagement of antibodies. CD388 represents one of the first DFCs to reach late-stage clinical development.