AstraZeneca, the British-Swedish multinational pharmaceutical company currently collaborating with the University of Oxford on a COVID-19 vaccine, will purchase Alexion Pharmaceuticals for $39 billion. The transaction, which awaits approval by shareholders and regulators, is the largest purchase by a health care company this year and is expected to close in the third quarter of 2021.

Alexion was founded in 1992 and is headquartered in Boston but has a global presence. It is known for its research and development of specialty drugs that treat rare diseases in niche markets usually not prioritized by larger pharmaceutical companies. To provide some examples, Alexion’s first approved drug is Soliris (one of the most expensive drugs in the world) and is used to treat atypical hemolytic uremic syndrome and Paroxysmal nocturnal hemoglobinuria, while Alexion’s second approved drug is Strensiq, which is used to treat hypophosphatasia.

The purchase represents a major investment in the market for rare-disease drugs by AstraZeneca, which will attempt to leverage its resources to grow Alexion’s pipeline. The company has also stated it expects the acquisition will “deliver double-digit average annual revenue growth through 2025.”

The acquisition news comes as AstraZeneca is collaborating with the University of Oxford in the final testing stages of its COVID-19 vaccine. Despite having to initiate a study hold on its development this fall, recent reports show positive results for the vaccine and up to 90% effectiveness in preventing infection.

Here are some reports relating to this deal for your reference: The New York Times, Bloomberg, and MarketWatch.