Will the FDA's Nod for Subcutaneous Keytruda Ease Merck's Headwinds?

Merck (MRK) has received FDA approval for Keytruda Qlex, a subcutaneous formulation of its blockbuster PD-L1 inhibitor, Keytruda, offering significantly faster administration and equivalent efficacy to the intravenous version. This approval is a critical strategic move for Merck, whose Keytruda IV faces patent expiration in 2028, as the SC version carries new patents extending protection and enables patient transition to mitigate generic erosion for its primary revenue driver. With a commercial launch expected this month and an EMA committee recommendation for European approval, this development is crucial for Merck to manage Keytruda's lifecycle and sustain revenue growth amidst declining sales of its second-largest product, Gardasil.

Analysis

Merck has secured a critical strategic victory with the FDA's approval of Keytruda Qlex, the subcutaneous (SC) formulation of its flagship PD-L1 inhibitor. This approval is pivotal for the company's long-term outlook as it directly addresses the impending patent expiration of the intravenous (IV) version in 2028. By offering a new formulation with its own patent protection, Merck has established a clear pathway for life cycle management, aiming to transition patients to the SC version to mitigate future revenue erosion from generics. The commercial case for Keytruda Qlex is compelling; its administration time of as little as one minute, compared to over 30 minutes for the IV form, offers significant convenience for patients and operational efficiencies for healthcare providers, likely driving strong adoption. This development is especially crucial given Keytruda's outsized contribution to Merck's financials, accounting for over 48% of total revenue and generating over $15 billion in the first half of 2025 alone. The positive recommendation from the EMA's committee for European approval further supports the global potential of this strategy. However, this success is set against the backdrop of a significant 48% year-over-year sales decline for Gardasil, the company's second-largest product, due to persistent weak demand in China, which amplifies the company's reliance on the Keytruda franchise.

Key Decisions for Investors

• The FDA approval of the subcutaneous Keytruda formulation significantly de-risks Merck's 2028 patent cliff, strengthening the long-term durability of its primary revenue stream and supporting a more bullish outlook on the stock.
• Investors should closely monitor the initial commercial launch and adoption rates of Keytruda Qlex, as the speed and success of converting patients from the IV to the SC version will be a leading indicator of the strategy's effectiveness.
• While the Keytruda development is a major positive, the sharp and ongoing decline in Gardasil sales represents a material headwind and increases the company's concentration risk, a factor that must be weighed against the enhanced outlook for the Keytruda franchise.