Semaglutide (Novo Nordisk)

iStock, Veronika Oliinyk Merck’s Keytruda will soon lose exclusivity, just as weight-loss giants Eli Lilly and Novo Nordisk press in with their blockbuster GLP-1s. King Keytruda, Merck’s blockbuster PD-1 inhibitor, has kept its throne as pharma’s best-selling drug for one more year. The cornerstone immuno-oncology therapy—which has amassed more than 40 indications—brought in nearly $32 billion in 2025. That was enough to fend off a class of competitors that are quickly gaining ground: GLP-1s. This ascendant drug class has exploded in popularity in recent years, driven largely by its ability to help patients lose weight. Indeed, with their stratospheric growth, these obesity drugs have set a new standard for mega-blockbuster products. While Keytruda technically held the top sales spot, Eli Lilly’s tirzepatide brands Mounjaro and Zepbound together made $36.51 billion, eclipsing the cancer powerhouse not even four years into the market. The same is true for Novo Nordisk’s semaglutide franchise, which includes Ozempic and Wegovy, as well as the older-generation injection Rybelsus. These three products last year brought in $36.19 billion, likewise outpacing Keytruda. Unlike Keytruda, which is facing near-term loss-of-exclusivity threats, GLP-1s have much more growth ahead of them. In a January 2026 report , analytics firm IQVIA said 2025 was the “year of consolidation” for the obesity space, with clinical evidence, policy, supply chain and market readiness coming together to set the stage for future growth. 2026, IQVIA continued, will be the “year of acceleration” for these drugs, especially as Lilly and Novo—the undisputed market leaders—usher in an era of weight-loss pills, which the firm suggested will mark a “major inflection point in obesity medication accessibility and patient preference.” Here, BioSpace dives into pharma’s five best-selling products in 2025, looking at the ascent of GLP-1s and the sustaining power of Keytruda, but also at heavy-hitters in the immunology space—relatively understated in terms of headlines, but definitely not in terms of revenue. Merck’s Keytruda Continues Reign as GLP-1s Close In 2025 sales: $31.7 billion YoY change: 7% For the third year, Merck’s cancer blockbuster Keytruda has beaten out all other pharmaceutical products on the market. Last year, the PD-1 inhibitor brought in $31.68 billion across its more than 40 indications , representing a 7% year-on-year increase. Keytruda faces some stiff competition from Eli Lilly’s tirzepatide franchise. In the third quarter, Keytruda’s earnings were $8.1 billion , while Lilly’s products together made $11.4 billion . Keytruda is approaching a key turning point in its lifecycle, however, with several crucial patents set to expire in 2028 , opening it up to biosimilar competition. Several drugmakers are already moving their copycat formulations through clinical development, according to a 2022 tally by the Generics and Biosimilars Initiative. Patents Merck’s Keytruda Likely Has a Few Extra Years of Dominance, With Billions on the Line Sales of Merck’s longtime oncology blockbuster Keytruda will erode more starkly in about 2033 rather than 2029, predicts Bloomberg Intelligence, translating to some $22 billion more in revenue. February 24, 2026 · 3 min read · Annalee Armstrong Read more Merck is attempting to head off the threat of earnings erosion by producing an under-the-skin version of Keytruda. The FDA signed off on this subcutaneous injection, which now carries the brand name Keytruda Qlex, in September 2025. Last year, Keytruda Qlex hit $40 million in sales. Keytruda is expected to continue growing as it approaches loss-of-exclusivity, hitting peak sales of $35 billion in 2028, Merck executives said during the pharma’s full-year 2025 earnings call on Feb. 3. Even past the 2028 patent inflection point, as biosimilars enter the market, Merck sees Keytruda Qlex as helping to buttress the product family. “We continue to think we are going to see 30% to 40% adopted as you get out to 2028,” CEO Robert Davis told investors on the call. “We will drive that as high as we can.” Lilly’s Mounjaro Edges Out Rival 2025 sales: $22.965 billion YoY change: 99% Despite being five years late to the GLP-1 game, Eli Lilly has emerged as the undisputed market champion. The pharma’s type 2 diabetes injection Mounjaro surged 99% year-on-year to earn $22.965 billion in 2025 and become the industry’s second-best-selling drug—while also cleanly surpassing its chief competitor. Many analysts consider Lilly to have outmaneuvered Novo in the obesity market, coming from behind the Danish giant with a stronger market execution for its products. Indeed, since entering the market in 2022, Mounjaro quickly overtook Novo’s Ozempic with a sales ramp-up that outpaced even Keytruda . Aside from superior marketing, Lilly’s product also appears to have an efficacy edge over Novo’s, with many studies over the years showing better weight-loss and sugar control figures with tirzepatide. Now faced with the task of ensuring it stays in the lead, Lilly is looking to expand its obesity business into the oral domain, with orforglipron awaiting a regulatory decision in April . In this market, too, the Indiana pharma is playing catch-up to Novo, which launched its oral form of Wegovy earlier this year. But Lilly doesn’t seem to be threatened. During the company’s full-year 2025 earnings call, Ken Custer, executive VP of Lilly cardiometabolic health, expressed optimism regarding the success of oral Wegovy, suggesting that 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.” Obesity Lilly Prepares $1B+ Orforglipron Stock Ahead of Approval as Novo Brings Wegovy Pill Overseas Eli Lilly has long been gearing up for the launch of orforglipron, announcing as early as February 2024 that it was ramping up manufacturing investments for the weight-loss pill. February 13, 2026 · 2 min read · Tristan Manalac Read more Lilly’s other tirzepatide brand Zepbound, which is indicated specifically for chronic weight management, made $13.542 billion in 2025—a 175% increase from the year prior. Taken together, the pharma’s tirzepatide franchise hit $36.507 billion last year, beating out Keytruda. Taking orforglipron into account, analysts expect Lilly’s obesity trifecta to top $100 billion in peak revenue. Despite First-Mover Advantage, Novo’s Ozempic Falls Behind 2025 sales: $20.1 billion YoY change: 10% After being 2024’s runner-up, Novo Nordisk’s Ozempic fell one spot in 2025 to land behind its chief competitor Mounjaro. The blockbuster diabetes drug, which opened the current era of GLP-1 dominance, brought in $20.1 billion in 2025 , a 10% increase over the previous year. Along with its sister brands Rybelsus and Wegovy, which are specifically indicated for weight-loss, Novo’s semaglutide franchise made roughly $36.19 billion last year, still trailing Lilly’s tirzepatide family. Novo has largely attributed its market troubles to the rise and persistence of compounders —independent manufacturers that make their own remixed versions of semaglutide. In the early days of the GLP-1 boom, the pharma was unable to keep up with the spike in demand, leaving room for compounders to enter the picture and establish a foothold in the market. The compounding problem grew big enough that Dave Moore, Novo’s EVP of U.S. operations, conceded in February 2025 that compounders? were “having an impact and it is growing faster than we had anticipated.” Aside from compounding, CEO Maziar Mike Doustdar also said on the company’s full-year 2025 earnings call last month that declining drug prices in the U.S. were a key commercialization challenge. The Danish giant is among several big pharma companies that have signed pricing deals with the government, offering its GLP-1 products at a discount through the state-sponsored direct-to-consumer platform TrumpRx. Despite falling behind Lilly, Novo has now been presented with a good opportunity to get back in the market with the FDA’s approval of oral Wegovy. The pill got off to a great start, reaching more than 3,000 patients in just its first week on the market. GLP-1 Novo’s Wegovy Pill Wins Obesity Approval, Securing Lead in Oral GLP-1 Race Analysts called the approval a much-needed win for Novo Nordisk, but warned that the company could struggle to grow sales once rival drugs come to market. December 23, 2025 · 2 min read · Nick Paul Taylor Read more Novo has vowed to go “ all in ” on oral Wegovy, Doustdar said on the earnings call. But given that the pharma has already flubbed a big market advantage once, analysts remain skeptical. Sanofi/Regeneron’s Dupixent Extends Reign as Most Valuable Immuno Drug 2025 sales: $17.806 billion YoY change: 26% Leading the immunology space is Sanofi and Regeneron’s Dupixent, which last year totaled $17.8 billion in sales , representing 26% year-on-year growth. Unlike Keytruda, Dupixent has no patent problems on its immediate horizon, with key U.S. protections holding until 2031 . The drug, which works by disrupting IL-4 and IL-13 signaling to suppress inflammation, has also recently expanded into new indications. In April 2025, Dupixent became the first new FDA-approved therapy in over a decade for chronic spontaneous urticaria. A few months later, the drug became the first targeted therapy for bullous pemphigoid. Sanofi and Regeneron are continuing to push Dupixent into new therapeutic areas, with a regulatory verdict in allergic fungal rhinosinusitis due by Feb. 28 . In April, the FDA is also set to release its decision on the use of Dupixent for chronic spontaneous urticaria in patients aged 2 to 11, according to a corporate presentation last month . Dupixent is also currently in late-stage development for lichen simplex chronicus and chronic pruritus of unknown origin. Regeneron is also testing a combo regimen of Dupixent with its bispecific antibody Lynozyfic for severe food allergy. Aside from unlocking new indications, the companies are also improving Dupixent’s formulation , with the goal of prolonging dosing intervals or improving efficacy, RegeneronCSO George Yancopoulos said during the pharma’s full-year 2025 earnings call in January. Given the drug’s continued development, analysts expect Dupixent to keep gaining through the end of the decade, with BMO Capital Markets estimating in a Jan. 29 note that sales could hit $22.7 billion by 2030. AbbVie Gracefully Rides Out Humira Cliff as Skyrizi Rises 2025 sales: $17.562 billion YoY change: 49.7% Capping off this list is AbbVie, which, in a way, has become a prime example of how to properly manage a patent cliff that would have otherwise been disastrous to a company’s bottom line. In 2025, the IL-23 blocker Skyrizi skyrocketed 49.7% on an operational basis, bringing in $17.562 billion. AbbVie owns Humira, which was once the world’s most valuable pharma franchise and reigned as the industry’s top-selling product for six years straight. In 2024, however, the anti-TNF therapy started buckling to competitive pressures from biosimilars, which were able to enter the market after Humira’s patent protections expired. Skyrizi was a fundamental element of AbbVie’s strategy to replace the mega-blockbuster, winning its first FDA approval in April 2019 for moderate to severe plaque psoriasis. The drug has since expanded into inflammatory bowel diseases (IBD), with a Crohn’s disease nod in June 2022 and one for ulcerative colitis in June 2024 . While Skyrizi has so far shown strong growth, investors have raised concerns about its near-term outlook, particularly as the IBD space grows more crowded, according to a Feb. 2 note to investors from William Blair. In March last year, Johnson & Johnson’s IL-23 inhibitor Tremfya won the FDA’s nod for Crohn’s disease, then months later earned another for ulcerative colitis. The analysts nevertheless expect Skyrizi to “continue to command dominant share in key markets.” Also crucial to AbbVie’s survival of the Humira cliff is the JAK inhibitor Rinvoq. The drug made $8.3 billion last year, a 38.8% year-on-year increase, finishing as 2025’s ninth best-selling medicine.

The announcement of a manufacturing expansion in Ireland comes roughly two weeks after Novo Nordisk CEO Mike Doustdar told Bloomberg that the company was eyeing an Ireland expansion to help produce its Wegovy pill for markets outside the U.S. With a vital obesity launch now underway in the U.S., Novo Nordisk is casting its attention eastward as it shores up the prospects of its Wegovy pill in Europe and beyond. Novo will invest 432 million euros ($501 million) to add a new tableting plant at its facility in Athlone, Ireland, the company said in a March 2 press release. The expansion will equip the Athlone site with significant additional capacity for Novo’s suite of current and future GLP-1 medicines, according to the release. Specifically, Novo says it is upgrading and retrofitting the existing site in Athlone to manufacture oral GLP-1s like the Wegovy pill. Novo originally announced its purchase of the site from Alkermes in late 2023. The project’s announcement comes roughly two weeks after Novo CEO Mike Doustdar told Bloomberg that the company was eyeing an Ireland expansion to help produce its Wegovy pill for markets outside the U.S. Novo’s Wegovy pill was approved by the FDA in late 2025, launched Jan. 5 and has since generated impressive prescribing stats during its roughly two months on the U.S. market. The pill, which is seen as key in Novo’s showdown in the prescription obesity market with Eli Lilly, is also under review in the EU, with an approval decision expected sometime this year. With the Athlone expansion, Novo asserts that it’s bolstering its oral drug production capabilities and supply while also positioning its Ireland operations as a “critical hub” for markets outside the U.S. The Emerald Isle is host to a bevy of Big Pharma manufacturing setups, including Novo’s chief metabolic medicine rival Eli Lilly, which produces its own GIP/GLP-1 drugs for diabetes and obesity, Mounjaro and Zepbound, there. In a sign of the republic’s biopharma production muscle, Ireland’s pharmaceutical manufacturing output surged a staggering 41.3% last year as companies sought to get a jump on potential U.S. import tariffs, financial services firm Atradius noted in a report earlier this year. That topped the surge seen in any other individual country last year and came in well above the global pharmaceutical production increase of 9.1%, according to Atradius.Novo says it has already started work on the Athlone expansion, which it expects to wrap up “gradually from the end of 2027 through 2028.” Novo noted that it currently has a workforce of 260 at the plant. The company explained that those workers will continue focusing on oral drug production without clarifying whether the project is expected to generate new jobs at the plant.  Novo’s Ireland expansion comes as it and many other drugmakers have sought to bolster their U.S. production footprints in recent months. In Novo’s case, the motivation behind its recent manufacturing moves was likely twofold, informed both by the threat of Trump administration pharmaceutical tariffs and a desire to avoid the supply shortfalls that defined early obesity GLP-1 launches for Novo and Lilly. On that front, Novo last June said it would spend $4.1 billion to construct a second-fill finish plant at its campus in Clayton, North Carolina, which is also producing the Wegovy pill. As with many of Novo’s recent projects, the new facility will also produce injectable Ozempic and Wegovy, the company said last year.