MRK Pins Hopes on New PAH Drug Winrevair Amid Looming Keytruda LOE

Core Insights - Merck's Keytruda, a PD-L1 inhibitor, is the primary revenue source, contributing approximately 50% of pharmaceutical sales and driving top-line growth [1] - The company is heavily reliant on Keytruda, which is set to lose exclusivity in 2028, prompting strategies for long-term growth [2][3] - Merck is developing a subcutaneous formulation of Keytruda and diversifying its product lineup, particularly in non-oncology areas [3] Winrevair Development - Merck is optimistic about Winrevair, a newly launched pulmonary arterial hypertension (PAH) drug, to enhance revenue post-Keytruda exclusivity [4] - Winrevair received FDA approval in March 2024 based on the STELLAR study, with EU approval following in August 2024 [4] - The drug has shown significant efficacy in late-stage studies, leading to early stoppages due to overwhelming results [6][8] Regulatory Updates - The FDA has accepted Merck's supplemental biologics license application (sBLA) for Winrevair, with a decision expected on October 25, 2025 [7][10] - The ZENITH study demonstrated a meaningful reduction in morbidity or mortality events, supporting the drug's efficacy [6] Financial Performance - Winrevair generated $280 million in sales in Q1 2025, with expectations for increased revenue following a successful label update [11] - Merck's shares have decreased by 17.1% year-to-date, contrasting with a 0.6% decline in the industry [15] - The company's price/earnings ratio is currently 8.84, lower than the industry average of 15.05, indicating attractive valuation [16] Market Competition - Winrevair faces strong competition in the PAH market from United Therapeutics and Johnson & Johnson, which have established products and significant sales [11][12]