Cidara completed enrollment of 6,000 participants in its Phase 3 ANCHOR trial of CD388, a single 450 mg subcutaneous dose intended to prevent seasonal influenza in high‑risk adults and adolescents, with an interim analysis slated for Q1 2026 to validate powering and decide whether to add Southern Hemisphere enrollment. The study is running in the US and UK and, if successful, is positioned as a single‑trial package for a potential BLA in the represented high‑risk populations.
The core development is operational: locking enrollment ahead of the Northern Hemisphere peak gives the program maximal exposure to circulating influenza during a single season, while preserving flexibility to expand if attack rates undercut event accrual. CD388, a drug‑Fc conjugate antiviral from Cidara’s Cloudbreak platform, is being tested as a non‑vaccine prophylaxis option for groups with impaired or inconsistent vaccine responses, including the immunocompromised, those with comorbidities, and older adults. The company reported positive Phase 2b data earlier this year and initiated ANCHOR in September; CD388 holds FDA Fast Track designation.
Strategically, the design signals a pragmatic response to seasonality risk. Sponsors in respiratory prophylaxis increasingly build adaptive features to hedge against mild seasons that jeopardize statistical power. Targeting high‑risk cohorts amplifies expected absolute risk reduction, improves the chance of clinically persuasive endpoints such as lab‑confirmed influenza and influenza‑related complications, and aligns with regulator and payer focus on populations with clear unmet need. Positioning a one‑time prophylactic dose also aims to sidestep adherence challenges seen with daily antivirals used for prophylaxis, though it shifts scrutiny to durability and resistance dynamics across an entire season.
For sites, the operational lift concentrates in a narrow window: rapid baseline assessments, vaccination status capture, and tight surveillance for influenza‑like illness with prompt PCR confirmation to preserve endpoint integrity. Expect heavy reliance on ePRO symptom diaries, rapid diagnostic logistics, and centralized adjudication to maintain data quality during peak seasonal surges. If the interim calls for Southern Hemisphere expansion, CROs and vendors will need to pivot quickly to activate networks in Australia, New Zealand, and Latin America, with lab capacity and cold‑chain planning adjusted for mid‑year start‑ups. A 450 mg subcutaneous dose suggests large‑volume administration; sites may need on‑body injectors or extended chair time, affecting throughput and staffing during the busiest months. On the commercial side, a non‑vaccine prophylactic for the immunocompromised could pressure formulary and coverage committees to consider seasonal, procedure‑like reimbursement models, separate from vaccine pathways.
The next inflection is the Q1 2026 interim. Key watch items include observed attack rates, event accrual sufficiency, and any sample‑size re‑estimation or geographic expansion. Efficacy thresholds will be assessed against standard vaccination plus usual care, with particular attention to reduction in medically attended influenza and hospitalizations in the highest‑risk subgroups. Safety and tolerability of a single large SC dose, injection‑site reactions, and immunogenicity will be closely parsed, as will signals of antiviral resistance. If ANCHOR delivers a clean efficacy and safety profile, a single‑trial BLA becomes credible for the studied populations, but success will still hinge on manufacturing scale, seasonal distribution logistics, and alignment with ACIP and payer guidance. In the near term, the severity of the current flu season may prove as determinative for timelines as the molecule itself.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
