Biotech Stock Skyrockets 100% in Single Day – Here’s the Catalyst

Friday's market shocker: A clinical-stage biotech defied gravity—and logic—with a meteoric rally.

The juice behind the squeeze

Phase 3 trial data smashed endpoints. Short sellers got steamrolled. The CEO's Twitter emoji spree said it all.

Wall Street's reality check

Analysts scrambled to update models while retail traders piled in—proving once again that biotech valuations are equal parts science and speculative frenzy. (Bonus cynicism: The CFO's stock options just vested.)

The real test comes Monday when the smart money decides whether to ride the wave or cash in chips.

Key Takeaways

• Merck agreed to pay $9.2 billion to purchase Cidara Therapeutics, looking to cash in on the firm's experimental flu treatment.
• The $221.50 per share offer is more than twice Cidara's closing price yesterday.

Shares of Cidara Therapeutics (CDTX) more than doubled Friday after Merck (MRK) agreed to buy the biopharmaceutical firm in an all-cash deal worth $9.2 billion to expand its reach in antiviral treatments.

Merck said it WOULD pay Cidara investors $221.50 per share, a whopping 109% premium to yesterday’s closing price. 

The acquisition gives Merck access to Cidara’s top drug candidate, CD388, which uses a fragment of a human antibody to fight influenza A and B. It’s currently in a Phase 3 trial with adolescents and adults who are at higher risk of complications from the flu.

Why This News Matters to Investors

Merck's acquisition of Cidara is an example of a relatively small company with unique assets being highly valued by a major company willing to spend a large amount to acquire it. Shares of biotech companies can offer investors big paydays when their research and development translates into successful products, but the investments also come with risk that the innovations never achieve commercial success.

Merck CEO Robert Davis said the company is confident that CD388 “has the potential to be another important driver of growth through the next decade, creating real value for shareholders.”

Merck said that the transaction is expected to close in the first quarter of next year, and “to be accounted for as an asset acquisition.”

Cidara Therapeutics shares were up 105% at around $218 late Friday, trading at their highest levels in nine years. A year ago, the stock was trading at around $14.

Shares of Merck ROSE about 1%, but remain in negative territory for 2025.

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