LONDON — The drug maker AstraZeneca agreed on Saturday to buy Alexion, a biopharmaceutical company, for $39 billion in cash and stock, as corporate giants resume big-ticket takeovers, even amid the pandemic.
The deal comes as AstraZeneca is in the final stages of testing a Covid-19 vaccine that it is developing with the University of Oxford, one of the most prominent candidates — but which has also faced questions about its effectiveness.
Through the deal for Alexion, the biggest by a health care company this year, AstraZeneca will bolster its offerings for rare diseases like blood disorders. It comes as corporate boards have continued to regain confidence after battening down the hatches in the early stages of the pandemic.
As stock markets have soared and debt financing remains cheap because of central bank policies, companies have resumed their quest for growth and scale — including through acquisitions.
Under the terms of the deal, AstraZeneca will pay $60 in cash and 2.1243 of its American depositary receipts for each of Alexion’s shares. That amounts to $175 a share, a nearly 45 percent premium to Alexion’s closing price on Friday.
AstraZeneca, which is headquartered in Cambridge, England, has turned its focus in recent years to cancer treatments, after its previous best-selling drugs, like the cholesterol treatment Crestor, lost their patent protections. In July, the company agreed to pay up to $6 billion to partner with the Japanese drug maker Daiichi Sankyo on a potential treatment for lung and breast cancers.
But AstraZeneca has been best known in recent months for its work in a different area: Covid-19 vaccines, where it is teaming up with researchers from Oxford.
The two announced in late November that their coronavirus vaccine appeared to be up to 90 percent effective. Unlike some other leading vaccine candidates, including those from Pfizer and Moderna, the AstraZeneca offering can be quickly produced in vast quantities, would cost only a few dollars per dose and is easy to store for long periods.
But scientists and industry experts almost immediately began to raise questions after AstraZeneca acknowledged a key mistake in the vaccine dosage received by some study participants, and now the issue is whether its vaccine’s efficacy will hold up under additional testing.
The deal for Alexion will help AstraZeneca expand in another sector: immunology, where treatments can be highly lucrative for their makers. Alexion, which is based in Boston, is known for focusing on combating rare diseases: Its top drugs include Soliris and Ultomiris, which treat blood disorders.
Each costs several hundred thousand dollars per year. That underpins AstraZeneca’s expectation that the deal will help lead to double-digit sales increases through 2025 and let it raise its dividend payouts.
“Alexion has established itself as a leader in complement biology, bringing life-changing benefits to patients with rare diseases,” Pascal Soriot, AstraZeneca’s chief executive, said in a statement.
The company has faced pressure in recent years from Elliott Management, the $41 billion activist investment firm run by the financier Paul E. Singer. The hedge fund has repeatedly criticized Alexion over its business strategy, including multibillion-dollar corporate takeovers that proved disappointing. (The day Alexion announced its acquisition of Portola Pharmaceuticals in May, its stock fell sharply, signaling investor discontent with the deal.)
Shortly after, Elliott demanded that the drugmaker sell itself. A spokeswoman for the hedge fund declined to comment on Saturday.
Shareholders in Alexion are expected to own about 15 percent of the combined company after the deal closes, which is expected by next September, pending approval by regulators and investors in both companies.