"Our agreement with Almirall brings strategic and long- term value to AstraZeneca's strong respiratory franchise, one of our key growth platforms," said Pascal Soriot, chief executive officer of AstraZeneca.
Almirall has a market value of about $2.7 billion. Chairman Jorge Gallardo and First Vice Chairman Antonio Gallardo own about 67 percent of the stock via two holding companies.
As part of the deal, AstraZeneca will acquire Eklira, also called Tudorza Pressair, a treatment for smoking-related diseases such as bronchitis and emphysema, which recorded $112 million in sales in 2013 and made up 12 percent of Almirall's revenue.
Another lung drug, Ebastel, had revenues of $102 million. Almirall's respiratory drugs combined for $283 million in sales.
Almirall is applying for U.S. approval to market a combination of Eklira with formoterol, developed with New York-based partner Forest Laboratories Inc. Although the combination is approved in Europe, U.S. regulators asked for additional data. Actavis Plc bought Forest this month.
AstraZeneca rejected Pfizer's bid of $117 billion in May, saying the company's pipeline of experimental drugs made it more valuable as a standalone company. In a June interview, Soriot said the company wouldn't make acquisitions as part of its defense strategy, although he said he would consider small to medium-sized acquisitions.