Cidara has begun dosing in ANCHOR, a global Phase 3 trial of CD388, a single 450 mg subcutaneous dose intended to prevent seasonal influenza, with planned enrollment of roughly 6,000 participants beginning in the Northern Hemisphere. The study includes adults and adolescents, with at least 10% immunocompromised, a balanced cohort of high-risk individuals with comorbidities, and—following FDA feedback—generally healthy adults aged 65 and older. An interim analysis after the Northern Hemisphere season will reassess powering and determine expansion into the Southern Hemisphere. The company signals that one successful Phase 3 could support a BLA for high-risk populations and reports over $500 million in cash to fund the program through completion.
The core development is a pivot from vaccine-dependent prevention toward a long-acting drug-Fc conjugate that directly inhibits viral proliferation and does not rely on host immune response. Phase 3 is randomized, double-blind, and placebo-controlled, positioning CD388 as an additive option rather than a vaccine replacement in the study design. This follows positive top-line Phase 2b data in healthy, unvaccinated adults and aligns with the FDA’s receptiveness to broader enrollment in older adults. The one-time, pre-season administration and strain-agnostic mechanism are central to the value proposition if efficacy holds across variable circulating strains and seasons.
Strategically, Cidara is aiming for operational simplicity and regulatory clarity: a single pivotal with adaptive sample-size re-estimation to manage seasonal incidence uncertainty, broad high-risk inclusion to support a meaningful label, and a practical dosing model that fits pharmacy or clinic workflows. It’s also a hedge against vaccine limitations—waning immunity, mismatch, non-response in the immunocompromised—and against adherence frictions that challenge multi-dose or booster-based approaches. The tension is twofold: placebo control rather than active comparison may limit direct positioning versus vaccines for payers and public health programs, and season-to-season variability in attack rates could pressure effect size estimates, necessitating the interim recalibration.
For sites and CROs, the study’s design reduces visit burden to a single dose plus surveillance and adjudication of lab-confirmed influenza, but it tightens activation timelines around season onset and demands robust symptom capture and testing logistics. Global hemispheric deployment and an interim-based resizing create operational complexity that will reward networks with flexible resourcing and rapid lab turnaround. Vendors enabling near-real-time case ascertainment and decentralized symptom reporting can materially de-risk missed endpoints. Regulators will focus on subgroup performance—especially immunocompromised participants and older adults—safety across comorbidity clusters, and durability through an entire season.
The near-term watch items are the Northern Hemisphere interim readout, event rates versus assumptions, and any safety signals specific to high-risk cohorts. If efficacy is consistent across subgroups and seasons, the case for a single-pivotal BLA strengthens, but regulators could still require post-marketing commitments or additional data in populations not fully powered by the interim. Commercially, pricing and payer coverage against low-cost vaccines remain open questions; demonstrating additive value for non-responders and those declining vaccination will be critical. Manufacturing scalability and distribution through retail or specialty channels will need to be proven well ahead of a potential launch. The broader signal for the sector is clear: long-acting, season-length prophylaxis is moving from RSV into influenza, and sponsors with adaptive, hemispheric designs will be better positioned to navigate incidence volatility and secure decisive registrational datasets.
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.
