Switzerland's Nestle will pay $34.50 a share for Aimmune, which makes Palforzia, the first treatment for peanut allergy to be approved by the Food and Drug Administration.
Aimmune shares closed at $12.60 on Friday. They were trading at $34.20 in trading Monday, up 171.43%.
Nestle's health sciences division already owns a 26% stake in Aimmune. Including that stake, the deal has an enterprise value of about $2.6 billion. Bloomberg calculated that Nestle will be paying about $1.7 billion for the Aimmune shares.
Back in February, Nestle lifted its investment in Aimmune by $200 million to $473 million.
The deal is expected to close in the fourth quarter.
"Aimmune's Palforzia is the first and only FDA-approved treatment to help reduce the frequency and severity of allergic reaction to peanuts, including anaphylaxis, in children aged 4 through 17," Nestle said.
"This transaction brings together Nestle's nutritional science leadership with one of the most innovative companies in food allergy treatment," said Nestle Health Science CEO Greg Behar. "Together we will be able to offer a wide range of solutions that can transform the lives of people suffering from food allergies around the world."
Palforzia received approval from the FDA on Jan. 31. The drug is derived from peanut powder and works by exposing patients to doses that are equivalent to small amounts of peanuts.
The list price for Palforzia, Aimmune said, is $890 a month, or about $10,680 a year.