Keytruda Sales Growth Faces Biosimilar Competition

Merck's (MRK) oncology flagship Keytruda has been driving steady revenue growth for the company, accounting for over 55% of its total pharmaceutical sales. The PD-L1 inhibitor has recorded sales worth $16.40 billion in the first half of 2026, up almost 4.2% year over year.

Keytruda's strong global uptake in earlier-stage indications and higher demand in metastatic indications have driven sales growth. The drug's recent label expansions, including its use in combination with Pfizer's (no mention) Padcev in muscle-invasive bladder cancer, have broadened its patient base and supported sales.

However, Keytruda is expected to face significant biosimilar competition around 2028-2029, which may lead to a sharp decline in sales. Merck is working on strategies to drive the drug's long-term growth, including innovative immuno-oncology combinations.