Cipla and Qilu partner to bring Keytruda biosimilar to U.S., intensifying looming competition for Merck's top drug

What happened

Merck's dominant oncology franchise faces a new named competitor as India's Cipla and China's Qilu Pharmaceutical announced an exclusive U.S. licensing partnership for a Keytruda biosimilar. The partnership adds a concrete entrant to the expected wave of biosimilar competition that Merck has already flagged for 2028–2029, when Keytruda's primary compound patent expires and potential U.S. biosimilars could launch as early as December 2028. Keytruda generated $31.68 billion in 2025 sales, representing 49% of Merck's total revenue, so any acceleration or broadening of biosimilar threats directly pressures the company's post-2028 earnings bridge. The master report's base case assumes biosimilar erosion begins in the 2028–2029 window, and this announcement does not alter that timeline but confirms that multiple manufacturers are actively preparing to enter the market. Merck's defensive strategy—including subcutaneous Keytruda approvals and portfolio diversification via acquisitions—remains critical as the competitive landscape for its core franchise becomes more crowded.

Implication

The announcement does not change the fundamental timeline for Keytruda's U.S. exclusivity, but it adds a named competitor to the watchlist and could modestly increase the probability of earlier or more aggressive biosimilar entry if patent challenges accelerate. Merck's valuation already reflects a significant Keytruda cliff, and the stock's current WAIT rating with implied value around $125 remains appropriate, though the risk-reward skew may tilt slightly negative if more biosimilar partnerships surface. Investors should monitor for any signals that biosimilar developers are targeting earlier launch dates or challenging patents, as that would compress the timeframe for Merck's pipeline and acquisitions to offset revenue erosion. The company's recent BD moves—including Verona, Cidara, and Terns—are direct responses to this competitive reality, and their successful integration and launch will be pivotal in maintaining investor confidence. Until Merck demonstrates that new growth pillars can scale at a pace that counteracts Keytruda's decline, the stock is likely to remain range-bound with a downward bias on competitive headlines like this one.

Thesis delta

No fundamental change to the investment thesis, but this news marginally increases the visibility and credibility of near-term biosimilar competition for Keytruda. The base case already assumes biosimilar entry in the 2028–2029 window, so the primary impact is on sentiment and the monitoring of competitive intensity. The WAIT rating stands, but investors should place higher weight on early signs of biosimilar commercialization activity.