MSD wins SC Keytruda approval, but analysts sceptical on impact

MSD has secured FDA approval for Keytruda QLEX, its subcutaneous formulation of the blockbuster cancer drug Keytruda, marking the first SC PD-1 blocker to receive clearance. This approval for 38 solid tumor indications aims to offer faster, more convenient patient administration, with MSD forecasting 30-40% adoption within two years of its late 2025 commercialization. While this innovation could help mitigate the impact of Keytruda's looming 2028 patent cliff, which threatens the drug responsible for nearly half of MSD's $29.5 billion 2024 sales, analysts caution that its convenience advantage may be limited in combination therapies requiring intravenous administration.

Analysis

MSD (MRK) has secured FDA approval for Keytruda QLEX, a subcutaneous (SC) formulation of its blockbuster oncology drug, representing the first SC PD-1 inhibitor to enter the market. This approval, covering 38 solid tumor indications, is a critical component of MSD's strategy to mitigate the impact of Keytruda's 2028 US patent expiration, which threatens a drug franchise that accounted for $29.5 billion, or nearly half of the company's total sales, in 2024. Management forecasts a 30% to 40% conversion rate from the intravenous (IV) version within two years of its late September 2025 commercial launch. However, the commercial potential of this new formulation faces significant constraints. Analysts caution that its primary benefit of convenience is negated in combination therapy settings that require other IV-administered agents like chemotherapies or antibody-drug conjugates (ADCs). Consequently, its adoption may be largely limited to patients on monotherapy or in combination with oral drugs, potentially capping its ability to fully defend the franchise's revenue post-patent cliff.

Key Decisions for Investors

• View the FDA approval as a positive but incremental step in MSD's life-cycle management strategy, as it provides a tool to defend market share but does not eliminate the fundamental revenue risk from the 2028 patent cliff.
• Monitor the adoption rate and market share of Keytruda QLEX post-launch, specifically tracking its penetration in monotherapy versus combination therapy settings to gauge its true commercial impact.
• Investors should maintain scrutiny on MSD's broader pipeline and M&A activity, as the limited utility of the SC formulation in combination regimens means the company still requires new, significant revenue drivers to offset the eventual decline of its largest asset.