AstraZeneca PLC (AZN) is a global biopharmaceutical company formed in 1999 through the merger of Sweden's Astra and the United Kingdom's Zeneca. It sells branded medicines in oncology, which contributes more than 40% of revenue; cardiovascular, renal, and metabolic diseases, which contribute more than 20%; rare diseases, about 16%; and respiratory and immunology, about 15%. Most sales come from international markets, while the United States accounts for close to one-third of total sales.