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Merck's Strategic Moves Continue
- Jana Chisholm
- Nov 26, 2025
- 2 min read
This week, following up on our recent post about Merck's strategic moves, we had Eyes On their recent bid for Cidara Therapeutics. This time, the acquisition is made to diversify their portfolio further, adding an antiviral asset for Influenza prophylaxis. This asset, CD 388, could provide a new class of prophylaxis, outside of the current vaccines area.
Cidara Therapeutics’s flagship influenza antiviral, which Johnson & Johnson discontinued last year, will cost Merck & Co. $9.2 billion. Merck is paying $221.50 in cash for each share of Cidara, a biotech company that has been conducting a phase 3 study on its antiviral, known as CD 388. The $105.99 share price that Cidara’s stock closed at the previous day is more than doubled by Merck’s offer from last week.
A non-vaccine option for preventing the flu is being developed: CD 388. The prophylaxis belongs to the class of drug-Fc conjugates, which are made up of several copies of a powerful small molecule neuraminidase inhibitor coupled to a customised Fc fragment of a human antiobody.
The highest dose of CD388, 450 mg, provided 76% protection against seasonal influenza in unvaccinated individuals compared to placebo, according to a phase 2b experiment published by Cidara in June. Lower doses, 300 mg and 150 mg, provided 61% and 58% protection, respectively.Since then, Cidara has moved the highest dose into phase 3 with funding from the Biomedical Advanced Research and Development Authority (BARDA) of the Department of Health and Human Services (HHS) that could total up to $339 million. According to the company, that financial agreement comprised confirmed cash of $58 million spread over two years, which was intended to assist Cidara develop its first commercial supply chain and boost domestic manufacture for CD388 in the United States.
Cidara, which had lost its Big Pharma partner Janssen in April 2024 due to the Johnson & Johnson unit’s wind-down of all infectious disease and vaccine R&D, benefited from the BARDA financing. In an agreement that included the possibility of development, regulatory, and commercial milestone payments, Cidara gave Janssesn $85 million up front in order to reclaim its asset. According to Merck, which describes CD388 as a possibly first-in-class, long-acting antiviral intended to prevent influenza in people at higher risk of complications, Janssen’s loss is Merck’s gain.
Merck’s agreement coincides with Robert F. Kennedy Jr.’s HHS’s growing mistrust of mRNA flu shots. Drug-Fc conjugates are not vaccinations or monoclonal antibodies, as Cidara has emphasised several times this year. The biotech noted that instead, they are low molecular weight biologics designed to operate as long-acting small molecule inhibitors.
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