Cidara Therapeutics has regained control of CD388, a promising drug-Fc conjugate aimed at providing universal prevention against influenza. This move follows Janssen Pharmaceuticals' strategic decision to exit infectious disease development, returning the asset to Cidara. CD388, which combines an approved virus-targeting small molecule with the Fc portion of a human antibody, is now advancing into a Phase 2b clinical trial.
From Collaboration to Reacquisition
In November 2021, Cidara entered into a collaboration agreement with Janssen to develop CD388. Cidara received an upfront payment of $27 million, with the potential for an additional $753 million in R&D funding and milestone payments. Cidara was responsible for the clinical development of CD388 through Phase 2a. After positive results from Phase 1 and 2a studies, Janssen initially decided to exercise its opt-in rights to take over late-stage development. However, Janssen's subsequent decision to exit infectious disease led to the divestiture of its clinical portfolio, including CD388.
Jeffrey Stein, Ph.D., President & CEO of Cidara, noted that Cidara's prior work on CD388, including holding the IND and controlling the drug supply, positioned them uniquely to continue its development. With financial backing from RA Capital Management, Bain Capital Life Sciences, BVF Partners, and Canaan Partners, Cidara successfully reacquired CD388.
Strategic Divestiture and Focus on CD388
To fully commit to the CD388 program, Cidara divested its interests in rezafungin (Rezzayo), an approved antifungal. This strategic move ensured that all capital and human resources would be focused on advancing CD388. According to Stein, the capital raise and Janssen deals were contingent on the divestiture of rezafungin.
CD388: A Novel Approach to Flu Prevention
CD388 represents a new modality for universal influenza prevention. Unlike vaccines, which require an immune response to an antigen, CD388 is designed to protect individuals from all strains of influenza with a single dose. The drug consists of the Fc domain of a human antibody conjugated to multiple copies of zanamivir, a potent small molecule inhibitor.
Zanamivir, marketed by GSK as Relenza, is an approved drug for influenza prevention and treatment but has limitations due to its poor drug properties and the need for inhaled administration. Cidara's drug-Fc conjugate approach aims to overcome these limitations by:
- Amplifying zanamivir's potency through multiple copies on the Fc portion.
- Enabling intramuscular or subcutaneous injection.
- Mitigating drug interactions and off-target toxicities by preventing penetration into human cells.
Manufacturing Advantages
Cidara's drug-Fc conjugate approach offers manufacturing advantages compared to monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs). CD388 can be manufactured at a cost of goods closer to that of a small molecule than a mAb. Unlike ADCs, which involve complex, multi-step manufacturing processes, CD388 production is streamlined, with all processes executed under the same roof.
Phase 2b Clinical Trial
Cidara initiated its international Phase 2b clinical study in September 2024. The trial aims to enroll and dose 5,000 unvaccinated subjects in the U.S. and U.K. to study the safety and efficacy of CD388 as a pre-exposure prophylaxis of influenza during the current flu season. Three different single-doses (plus placebo) will be tested, and patients will be monitored throughout the flu season.
