Merck finalizes $9B Cidara buy to secure flu preventative

Merck & Co. (NYSE:MRK) completed its acquisition of Cidara Therapeutics on Wednesday, following a successful tender offer that values the biotechnology firm at approximately $9 billion.

The deal brings CD388, a long-acting antiviral candidate designed to prevent symptomatic influenza, into Merck’s expanding respiratory pipeline.

Merck acquired all outstanding shares for $221.50 each in cash, with roughly 86% of Cidara’s common stock tendered by the Tuesday night deadline.

The pharmaceutical giant expects the transaction to result in a $9 billion research and development charge for 2026, or roughly $3.65 per share, as it integrates Cidara as a wholly owned subsidiary and delists the company from the Nasdaq.

The strategic move highlights Chief Executive Officer Robert M. Davis’s focus on high-value business development to offset looming patent cliffs for Merck's top sellers.

By acquiring CD388, Merck gains a "strain-agnostic" asset that could offer a significant advantage over seasonal vaccines by providing durable protection for high-risk individuals.

While the merger strengthens Merck's long-term respiratory outlook, the company warned that the acquisition and subsequent development costs will negatively impact earnings per share by approximately $0.30 over the next 12 months