AZN vs. MRK: Comparing Keytruda, Pipelines and Growth Strategies

Kinjel Shah September 21, 2026

AZN MRK MRNA

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Key Takeaways

AstraZeneca targets $80 billion in revenues by 2030, backed by 20 planned new medicine launches.
Merck's Keytruda remains a major growth driver, with peak sales expected to reach $35 billion by 2028.
Both face patent pressures. MRK trades at a higher forward P/E than AZN.

AstraZeneca (AZN - Free Report) and Merck (MRK - Free Report) are leading global drugmakers with broad and diversified portfolios. Merck is based in the United States, while AstraZeneca is headquartered in Cambridge, UK. Both have strong positions in oncology, which remains a key growth driver for each company.

Oncology accounts for more than 60% of Merck’s pharmaceutical revenues, led by blockbuster Keytruda, which contributes more than half of pharma sales. At AstraZeneca, oncology represents about 46% of total revenues, with segment sales rising 15% at constant exchange rates in the first half of 2026. Beyond oncology, AstraZeneca has a strong presence in immunology, rare diseases, vaccines and cardiovascular/respiratory medicine. Merck’s portfolio also spans vaccines, neuroscience, diabetes, virology and animal health.

The two companies also collaborate on the PARP inhibitor Lynparza, highlighting their strategic relationship in oncology.

Both drugmakers continue to post solid revenue and earnings growth and have promising long-term pipelines. However, with the stocks trading at current levels, which offers the more compelling investment opportunity? Comparing their fundamentals, growth prospects, valuations and key risks can provide a clearer view of their relative risk-reward profiles.

The Case for MRK Stock

Merck boasts more than six blockbuster drugs in its portfolio, with Keytruda being the key top-line driver. Keytruda, approved for several types of cancers, has played an instrumental role in driving Merck’s steady revenue growth over the past few years. Though Keytruda will lose patent exclusivity in 2028, its sales are expected to remain strong until then.

The company expects Keytruda to achieve peak sales of $35 billion by 2028. Merck’s other oncology drugs, Welireg, AstraZeneca-partnered Lynparza and Eisai-partnered Lenvima, are also contributing to top-line growth.

MRK’s Animal Health business is also a key contributor to its top-line growth, with sales expected to more than double by the mid-2030s.

Merck’s expanding drug pipeline and potential new blockbuster drugs beyond Keytruda look encouraging. Its late-stage pipeline has expanded substantially since 2021, supported by in-house progress as well as the addition of candidates through M&A deals. Merck expects to launch 20 new drugs by 2030, with many already launched.

Its new products, pulmonary arterial hypertension drug Winrevair, cancer drug Welireg and 21-valent pneumococcal conjugate vaccine, Capvaxive, have begun to contribute significantly to top-line growth.

In a key pipeline development, last month Merck and partner Moderna (MRNA - Free Report) announced positive top-line data from a phase III study, which evaluated their personalized cancer therapy combo as an adjuvant treatment for patients with completely resected stage IIB-IV melanoma. The phase III INTerpath-001 study evaluated Moderna’s investigational mRNA-based individualized neoantigen therapy (“INT”), intismeran autogene, in combination with Keytruda. The study met its primary endpoint of recurrence-free survival and key secondary endpoint of distant metastasis-free survival.

Merck is actively pursuing acquisitions to prepare for Keytruda’s 2028 patent expiration. Recent deals added Ohtuvayre through Verona Pharma, influenza candidate MK-1406 through Cidara, and potential blockbuster cancer drug MK-4208 through Terns Pharmaceuticals.

However, sales of Merck’s second-largest product, its HPV vaccine Gardasil, have slowed down, with sales declining 9% in the first half of 2026 amid weaker demand in China, Japan and the United States. The outlook remains challenging, particularly in China, where economic weakness, elevated channel inventories and growing competition from lower-cost domestic HPV vaccines are expected to keep 2026 revenues immaterial, while changes in U.S. vaccination recommendations are also weighing on demand.

Merck is heavily reliant on Keytruda. While Keytruda may be Merck’s biggest strength and a solid reason to own the stock, the company is excessively dependent on the drug. Keytruda’s core U.S. patent is expected to expire around 2028, with additional patents expiring shortly thereafter. Keytruda is expected to face significant biosimilar competition around 2028-2029. Once biosimilars enter the market, Keytruda’s sales are likely to decline sharply.

Merck faces continued revenue pressure from declining demand for its diabetes drugs Januvia/Janumet and increasing generic erosion across products such as Isentress/Isentress HD, Bridion and Dificid.

The Case for AZN Stock

AstraZeneca now has 16 blockbuster medicines, including Tagrisso, Fasenra, Farxiga, Imfinzi, Lynparza, Soliris and Ultomiris in its portfolio, with sales (product sales and alliance revenues) exceeding $1 billion. These drugs are driving AstraZeneca’s top-line growth, backed by increasing demand trends.

Newer drugs like Wainua, Airsupra, Saphnelo, Datroway (partnered with Daiichi Sankyo) and Truqap are also contributing to top-line growth, more than offsetting the LOE of some mature brands like Brilinta, Pulmicort and Soliris.

AZN expects continued revenue and earnings growth in 2026. It expects total revenues to grow by a mid-to-high single-digit percentage at CER in 2026, while core EPS is expected to increase by a low double-digit percentage at CER. The company is also on track to achieve a mid-30s percentage core operating margin by 2026.

AstraZeneca has set itself some visible targets for the next few years. It expects to generate $80 billion in total revenues by 2030. By that time frame, AstraZeneca plans to launch 20 new medicines, with around 11 already launched/approved. Two new drugs, Etcamah in breast cancer and Baxfendy in hypertension, are already approved this year.

AstraZeneca believes that many of these new medicines, like Datroway, Etcamah and Baxfendy, have peak-year revenue potential of more than $5 billion. Beyond these launches, AstraZeneca also boasts a broad portfolio of late-stage assets that are expected to deliver pivotal data before 2030, including multiple programs with multi-blockbuster potential. AstraZeneca expects a rich catalyst path ahead with several high-value readouts due over the next 18 months.

However, despite solid underlying financial performance, AstraZeneca faces its share of challenges. The loss of exclusivity of mature brands like Brilinta, Pulmicort and Soliris is hurting sales. Generic versions of one of the company's major drugs, Farxiga, have been launched in the United Kingdom, United States, Japan and China, and revenues are declining sharply.

China, though an important market for AstraZeneca, remains a somewhat uncertain market due to pricing pressure from volume-based procurement (VBP) programs and ongoing legal and compliance investigations involving the company’s former China head, Leon Wang. China contributes roughly 12% of the company's revenues. AZN’s stock has also taken a beating recently, with the company facing several pipeline setbacks in the past few months.

How Do Estimates Compare for AZN & MRK?

The Zacks Consensus Estimate for AZN’s 2026 sales and EPS implies a year-over-year increase of 7.6% and 2.0%, respectively. EPS estimates for 2026 have declined from $10.22 per share to $9.34 per share over the past 60 days, while those for 2027 have declined from $11.47 to $10.54 over the same timeframe.