The Shifting Landscape of Blockbuster Drugs
The pharmaceutical industry is in a constant state of flux, with blockbuster drugs—those generating over a billion dollars in annual revenue—vying for the top position. For over a decade, AbbVie's Humira was the undisputed king, but its reign has ended due to patent expiries and the rise of powerful new therapies [1.5.3, 1.2.3]. Today, the battle for the title of the world's best-selling drug is primarily a contest between an innovative cancer treatment and a new class of metabolic drugs that have captured global attention.
The Reigning Champion: Keytruda (pembrolizumab)
Merck's Keytruda (pembrolizumab) is currently the world's top-selling drug, achieving remarkable sales of $29.48 billion in 2024, an 18% increase from its $25 billion revenue in 2023 [1.2.1, 1.3.5]. Keytruda is a type of immunotherapy known as a PD-1 inhibitor [1.6.6].
Mechanism of Action Unlike traditional chemotherapy that directly attacks cancer cells, Keytruda works by harnessing the body's own immune system. Some cancer cells can produce a protein called PD-L1, which binds to the PD-1 receptor on immune T-cells. This interaction acts as an "off switch," preventing the T-cells from recognizing and attacking the cancer cells [1.6.2]. Keytruda blocks this PD-1 pathway, effectively releasing the brakes on the immune system and allowing T-cells to identify and destroy cancer cells [1.6.1, 1.6.4].
Approved Uses Keytruda's success is largely due to its broad range of approved indications. It is used to treat numerous types of cancer, including:
- Melanoma (skin cancer) [1.6.1]
- Non-small cell lung cancer (NSCLC) [1.6.1]
- Head and neck squamous cell cancer (HNSCC) [1.6.1]
- Classical Hodgkin lymphoma [1.6.5]
- Bladder and urinary tract cancer [1.6.1]
- Triple-negative breast cancer [1.6.1]
- Cervical, endometrial, stomach, and colorectal cancers [1.6.3]
The continuous expansion of its approved uses for earlier-stage cancers has been a major driver of its revenue growth [1.3.3].
The Meteoric Rise of GLP-1 Agonists: Ozempic and Wegovy
While Keytruda holds the top spot, drugs from the GLP-1 (glucagon-like peptide-1) receptor agonist class are experiencing explosive growth. Novo Nordisk's Ozempic and Wegovy, both of which have semaglutide as the active ingredient, are at the forefront of this trend. In 2024, Ozempic alone generated $18.655 billion in sales, a 25.8% increase from the previous year [1.2.1]. Together, Ozempic and Wegovy brought in about $26 billion for Novo Nordisk in 2024 [1.4.1].
Mechanism and Different Indications Though they share the same active ingredient, Ozempic and Wegovy are approved for different uses and prescribed in different doses [1.7.4].
- Ozempic: Approved for managing blood sugar levels in adults with type 2 diabetes, with a secondary benefit of weight loss [1.7.1, 1.7.2]. It works by increasing insulin production, slowing digestion, and reducing appetite [1.7.3].
- Wegovy: Specifically approved for chronic weight management in adults and children aged 12 and over who are obese or overweight with weight-related health issues [1.7.2, 1.7.5]. It is prescribed at a higher dose than Ozempic to maximize its appetite-suppressing effects [1.7.3].
The immense public interest and demand for their weight-loss benefits have made these drugs household names and driven their sales to unprecedented heights.
The Former King: Humira's Decline
For years, AbbVie's Humira (adalimumab) was the best-selling drug globally, peaking with sales of $21.2 billion in 2022 [1.5.3]. It is used to treat a variety of autoimmune and inflammatory conditions, such as rheumatoid arthritis and Crohn's disease [1.5.4]. However, the loss of its patent exclusivity in the U.S. in 2023 opened the door for cheaper "biosimilar" versions to enter the market [1.5.3]. This direct competition has caused a sharp decline in Humira's sales, which fell to $8.993 billion in 2024, causing it to drop out of the top 10 best-sellers list entirely [1.2.3].
Comparison of Top Selling Drugs
| Feature | Keytruda (pembrolizumab) | Ozempic (semaglutide) | Humira (adalimumab) |
|---|---|---|---|
| Company | Merck & Co. [1.2.1] | Novo Nordisk [1.2.1] | AbbVie [1.2.4] |
| Primary Use | Cancer Immunotherapy [1.6.2] | Type 2 Diabetes [1.7.2] | Autoimmune Diseases [1.5.4] |
| Mechanism | PD-1 inhibitor; helps the immune system attack cancer cells [1.6.4] | GLP-1 receptor agonist; increases insulin, slows digestion, reduces appetite [1.7.3] | TNF-alpha blocker; reduces inflammation [1.5.4] |
| 2023 Revenue | $25.011 billion [1.2.1] | $14.846 billion [1.2.1] | $14.4 billion [1.5.3] |
| 2024 Revenue | $29.482 billion [1.2.1] | $18.655 billion [1.2.1] | $8.993 billion [1.2.3] |
Conclusion: A Dynamic and Competitive Market
The title of the world's best-selling drug is a reflection of major trends in global health, from the fight against cancer to the growing challenges of diabetes and obesity. Keytruda's current leadership highlights the transformative impact of immunotherapy in oncology. At the same time, the rapid ascent of Ozempic and other GLP-1 agonists demonstrates a massive unmet need and consumer demand for effective metabolic and weight-loss treatments. The decline of Humira serves as a potent reminder of the pharmaceutical lifecycle, where patent cliffs and biosimilar competition inevitably reshape the market. The race for the top spot will remain fiercely competitive, driven by scientific innovation, expanding treatment indications, and evolving public health priorities.
