The US Food and Drug Administration (FDA) granted the drug Breakthrough Therapy designation to Cidara Therapeutics’ investigational influenza prophylactic, CD388, for the prevention of influenza A and B in high-risk adults and adolescents.
This new status builds upon a previously awarded Fast Track designation by the US regulatory agency. The designation is specifically for individuals at higher risk of complications due to underlying immunodeficiency, those for whom vaccines are contraindicated, or those who remain at severe risk despite vaccination.
“This Breakthrough Therapy designation underscores the importance of CD388 as a potential new non-vaccine prophylactic for seasonal influenza,” said Jeffrey Stein, Ph.D., president and CEO of Cidara. He noted that current vaccines may not adequately protect everyone, leaving immunocompromised individuals, the elderly, and those with chronic conditions vulnerable. “As a long-acting prophylactic drug, CD388’s activity does not rely on an immune response, making it a potential prevention option for these high-risk individuals.”
Clinical Data
The FDA’s decision is grounded in positive results from the Phase IIb NAVIGATE trial (NCT06609460). In this study, CD388 demonstrated a statistically significant prevention of seasonal influenza in healthy, unvaccinated adults. Top-line data was released in June 2025, with more detailed results expected at scientific conferences later in October.
Bolstering its development path, the Phase III ANCHOR trial (NCT07159763) evaluating CD388’s safety and efficacy was initiated in September 2025, six months ahead of schedule. Based on FDA feedback, the trial’s scope has been expanded to include generally healthy adults over 65, in addition to other high-risk populations with comorbidities or compromised immune systems.
The Breakthrough Therapy designation is a crucial FDA initiative designed to expedite the development and review of drugs for serious conditions when preliminary evidence suggests a substantial improvement over available therapies. Benefits include eligibility for a priority review, a rolling submission process for the Biologic License Application (BLA), and intensive guidance from senior FDA managers to streamline the path to potential approval.
CD388 is a drug-Fc conjugate (DFC) developed using Cidara’s proprietary Cloudbreak platform. It is designed as a long-acting antiviral that directly inhibits viral proliferation, aiming to provide universal prevention of both seasonal and pandemic influenza with a single dose. Its mechanism of action, independent of the patient’s immune system, positions it as a critical tool for populations that do not respond robustly to traditional vaccines.
Further Development
The program has also received substantial financial backing. Cidara secured a funding award from the US Biomedical Advanced Research and Development Authority (BARDA) worth up to $339 million to support expanded manufacturing and clinical development of CD388.
The company plans to advance CD388 through additional Phase II and III studies with BARDA’s support, exploring its efficacy across diverse populations and pandemic strains, in addition to establishing US-based manufacturing.
Cidara anticipates advancing CD388 through the ongoing Phase III ANCHOR trial and subsequently submitting a biologics license application (BLA) to the US FDA, bringing this promising prophylactic one step closer to patients in need.
