Merck acquires flu specialist Cidara Therapeutics for USD 9.2 billion

Cidara Therapeutics, a portfolio company of Arctic Aurora LifeScience, has agreed to be acquired by the large pharmaceutical company Merck for $9.2 billion. This represents a 109% premium over Cidara’s last closing stock price.

Cidara’s lead drug candidate, CD388, is currently undergoing phase 3 trials for the prevention of influenza infections in individuals at a higher risk of disease complications. Flu is a well-known disease that affects many people every year. The primary strategy for preventing it is to get a flu shot before the start of each flu season. However, as the flu virus is highly susceptible to mutation, vaccine manufacturers must adapt their products every year. Additionally, current vaccines are only 40–60% effective in the general population and provide weaker protection for high-risk groups and the elderly.

In contrast, CD388 is an antiviral drug that targets a conserved part of the virus, so it does not need to be changed every year. It is connected to an antibody fragment with modifications that ensure a longer half-life and a potentially more durable effect that lasts for the whole flu season. The company is currently targeting high-risk patients and the elderly, achieving up to 76% protection in phase 2 trials earlier this year.

This acquisition would be a good strategic fit for Merck, given their existing strong presence in infectious diseases, particularly HIV and RSV. Furthermore, the patent for their primary cancer drug, Keytruda, is due to expire at the end of 2028. As Keytruda generates approximately USD 30 billion in revenues — almost half of Merck’s total sales — the company is actively working to replenish its commercial and development pipeline before Keytruda revenues start to decline. The acquisition of Cidara therefore fits well into this strategy.