King Keytruda, Merck’s PD-1 inhibitor, has maintained its position as the world’s top-selling pharmaceutical product in 2025. The immuno-oncology drug generated nearly $32 billion in sales last year, securing its place at the top even as GLP-1 drugs continue to grow rapidly.
Keytruda is approved for over 40 indications and saw a 7% increase in sales from the previous year, reaching $31.68 billion. However, competition from GLP-1 drugs—primarily those developed by Eli Lilly and Novo Nordisk—is intensifying. Eli Lilly’s tirzepatide brands Mounjaro and Zepbound together reached $36.51 billion in combined revenue in 2025, while Novo Nordisk’s semaglutide franchise, including Ozempic, Wegovy, and Rybelsus, brought in $36.19 billion.
Unlike Keytruda, which faces patent expirations starting in 2028 that will open it up to biosimilar competition, GLP-1 products are expected to see further growth. According to IQVIA's January 2026 report, 2025 was described as the “year of consolidation” for obesity treatments as clinical evidence and market readiness aligned to support expansion. IQVIA predicts that 2026 will be a “year of acceleration,” especially with new weight-loss pills entering the market from leading companies like Lilly and Novo.
Merck is preparing for future challenges by developing an under-the-skin version of Keytruda called Keytruda Qlex. Approved by the FDA in September 2025, this subcutaneous injection contributed $40 million to last year’s sales. Merck executives anticipate continued growth for Keytruda until it loses exclusivity and project peak annual sales of $35 billion by 2028.
“We continue to think we are going to see 30% to 40% adopted as you get out to 2028,” said CEO Robert Davis during Merck’s full-year earnings call on February 3rd. “We will drive that as high as we can.”
Eli Lilly's Mounjaro achieved sales of $22.965 billion in 2025—a nearly double increase compared to the previous year—and became the industry’s second best-selling drug. The company also reported significant growth with Zepbound (for chronic weight management), which saw a year-on-year increase of 175%, reaching $13.542 billion in revenue.
Lilly is working on expanding into oral obesity treatments with orforglipron pending regulatory review expected this April. Ken Custer, executive vice president of Lilly cardiometabolic health, commented on the success of oral formulations: “It validates our belief that there’s a substantial number of people with overweight and obesity who’ve been sitting on the sidelines waiting for an oral option.”
Novo Nordisk's Ozempic dropped behind Mounjaro with $20.1 billion in sales but still experienced a modest rise over last year (10%). Including Wegovy and Rybelsus, Novo's semaglutide portfolio generated roughly $36.19 billion overall.
Novo has attributed some commercial challenges to compounded versions of semaglutide produced by independent manufacturers during periods when demand outpaced supply capacity. Dave Moore, executive vice president for U.S operations at Novo Nordisk said earlier this year that compounders were “having an impact and it is growing faster than we had anticipated.” Additionally, CEO Maziar Mike Doustdar noted declining U.S drug prices due to pricing agreements such as those made through TrumpRx.
With FDA approval granted for oral Wegovy at the end of last year—reportedly prescribed more than three thousand times within its first week—Novo hopes this formulation will help regain momentum despite lingering skepticism among analysts about its long-term prospects.
In immunology therapies outside oncology or diabetes/obesity spaces, Sanofi and Regeneron’s Dupixent led with sales totaling $17.806 billion (a yearly growth rate of 26%). Patent protections remain strong until at least 2031 while new approvals—including treatment options for chronic spontaneous urticaria and bullous pemphigoid—have expanded Dupixent's reach further into dermatological conditions.
RegeneronCSO George Yancopoulos stated during their January earnings call that efforts are underway to improve Dupixent formulations: prolonging dosing intervals or enhancing efficacy remains a priority as late-stage trials continue across several indications.
AbbVie also features prominently among top earners after successfully navigating Humira’s loss-of-exclusivity period (“patent cliff”). Its IL-23 blocker Skyrizi posted revenues of $17.562 billion—a nearly fifty percent jump over last year—as AbbVie shifted focus following increased biosimilar competition against Humira beginning in early 2024.
While Skyrizi has grown strongly since initial FDA approval for plaque psoriasis in April 2019—and subsequent extensions into Crohn’s disease (June 2022) and ulcerative colitis (June 2024)—analysts have raised concerns about future competitive pressures from other drugs such as Johnson & Johnson's Tremfya but expect Skyrizi will retain dominant market share moving forward.
Also contributing significantly was AbbVie’s JAK inhibitor Rinvoq ($8.3 billion; up nearly forty percent), ranking ninth among best-selling medicines worldwide last year.
