TLDR
- Merck is acquiring Cidara Therapeutics for $221.50 per share in cash, valuing the deal at up to $9.2 billion
- Cidara’s stock jumped nearly 100% in premarket trading following the announcement
- The acquisition centers on Cidara’s experimental long-acting antibody drug CD388 for universal flu prevention
- CD388 showed 76% protection against influenza in mid-stage clinical trials and received FDA breakthrough therapy designation
- The deal could be announced as soon as Friday, November 14, 2025, after Merck beat competing pharmaceutical companies
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Merck is finalizing a deal to acquire Cidara Therapeutics for $221.50 per share in cash. The transaction values the biotechnology company at up to $9.2 billion.
Cidara Therapeutics, Inc., CDTX
The deal could be announced as soon as Friday, November 14, 2025. Multiple sources confirmed the agreement late Thursday evening.
Cidara’s stock responded dramatically to the news. Shares surged nearly 100% in premarket trading, reaching approximately $208 per share. The company’s market capitalization had been around $3.3 billion before the acquisition talks became public.
Merck $MRK is close to a deal to buy flu biotech Cidara Therapeutics $CDTX at a premium to its roughly $3.3B market cap, per FT.
Cidara’s lead flu antibody CD388 is in phase 3 with FDA breakthrough status. A takeover would help Merck backfill Keytruda before 2028 patent loss. pic.twitter.com/u2nPxNWt2S
— Wall St Engine (@wallstengine) November 13, 2025
Merck competed with at least one other pharmaceutical company for Cidara. The competing bidder was still in the running late Thursday before Cidara accepted Merck’s offer.
The acquisition focuses on Cidara’s experimental drug CD388. This long-acting antibody drug targets universal flu prevention.
Clinical Trial Results Drive Valuation
CD388 demonstrated up to 76% protection against influenza in mid-stage clinical trials. The drug represents a non-vaccine approach to flu prevention.
Unlike traditional flu shots that require annual administration, CD388 is designed as a single-dose treatment. The drug could provide season-long protection for high-risk patients.
The FDA granted CD388 breakthrough therapy designation last month. This designation accelerates the development and review process for drugs treating serious conditions or unmet medical needs.
The breakthrough status specifically applies to preventing influenza A and B in people at high risk of severe illness. This regulatory recognition likely increased Cidara’s attractiveness to potential buyers.
Deal Structure and Payment Terms
The $221.50 per share price represents an all-cash offer. However, the deal may also include milestone-based payments.
These additional payments would be triggered when specific clinical trial targets are met. The exact structure of these milestone payments has not been disclosed.
The total deal value of $9.2 billion includes both the upfront cash payment and potential milestone payments. This represents a substantial premium over Cidara’s previous market value.
Cidara Therapeutics declined to comment on the reports. Merck did not immediately respond to requests for comment from Reuters.
The acquisition adds a potentially transformative flu prevention therapy to Merck’s pipeline. CD388 could offer an alternative to traditional vaccines for high-risk populations.
