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

AstraZeneca AZN and Merck MRK 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.