This is why Merck is buying a flu biotech for $9.2 billion and Wall Street is happy

Merck & Co. is acquiring Cidara Therapeutics for $9.2 billion, representing a 109% premium, to secure the late-stage antiviral flu drug CD388, projected to reach $3.1 billion in peak sales by 2040. This strategic move aims to mitigate the impact of the impending patent expiration for its top-selling cancer drug Keytruda in 2028 and the 48% decline in Gardasil sales, which collectively accounted for 59% of Merck's 2024 revenue. The acquisition, which caused Cidara's stock to surge 106% and Merck's shares to gain, aligns with Merck's stated M&A strategy to bolster its pipeline against future revenue challenges and is viewed favorably by analysts.

Analysis

Merck (MRK) is acquiring Cidara Therapeutics (CDTX) for $9.2 billion, paying a 109% premium at $221.50 per share, to secure the late-stage antiviral flu drug CD388. This strategic move directly addresses the impending patent expiration of its top-selling cancer drug Keytruda in 2028, which generated $29.5 billion in 2024. The acquisition also aims to mitigate the impact of declining Gardasil sales, which plunged 48% to $2.4 billion in H1, following increased competition in China.

CD388, currently in Phase 3 trials, demonstrated 76.1% efficacy in a Phase 2b study and is projected to achieve peak sales of $3.1 billion by 2040, with a targeted launch in 2028. This potential revenue stream is crucial, as Keytruda and Gardasil collectively represented 59% of Merck's total sales in 2024. Wall Street analysts, such as Cantor's Carter Gould, view CD388 as a meaningful offset to Keytruda's loss of exclusivity, aligning with Merck's existing infectious disease portfolio.

This acquisition aligns with Merck's stated M&A strategy, having expressed a willingness to spend up to $15 billion on deals since January 2024, including the recent $10 billion acquisition of Verona Pharma. The market reacted positively, with Cidara's stock soaring 106% and Merck's shares gaining 0.8% towards an eight-month high, reflecting optimistic investor sentiment. The deal's expected closure in Q1 next year reinforces Merck's proactive pipeline diversification efforts.

Key Decisions for Investors

• Investors should closely monitor Merck's execution of the CD388 development and commercialization, particularly its ability to meet the 2028 launch target and achieve projected peak sales, as this is critical for offsetting Keytruda's patent cliff.
• Evaluate Merck's ongoing M&A strategy and its success in diversifying its revenue streams beyond Keytruda and Gardasil, considering the significant reliance on these two drugs in 2024.
• Keep an eye on the competitive landscape for both the new flu antiviral market and the HPV vaccine market, especially in regions like China, which could impact future revenue projections for Merck's portfolio.