Thomson Reuters
People pass the Pfizer World Headquarters building in New York
The deal values Medivation at $81.50 per share, a notable premium to the $52.50-per-share offer Sanofi had made earlier this year.
Medivation shares ended trading at $67.16 on Friday.
Sanofi went public with its $9.3 billion bid for the company in April. Medivation had rejected that bid but it wasn't long before it was fielding other offers and analysts were speculating about possible buyers, including reports that Pfizer - which in April terminated its merger with Allergan after the US Treasury released new rules - was in the mix.
"The addition of Medivation will strengthen Pfizer's Innovative Health business and accelerate its pathway to a leadership position in oncology, one of our key focus areas, which we believe will drive greater growth and scale of that business over the long-term," Pfizer CEO Ian Read said in a release.
The San Francisco-based biotech already has one drug on the market to treat prostate cancer. And its big appeal comes from an experimental breast-cancer treatment called talazoparib. It still hasn't been approved for use, but the drug also has potential as a treatment of cervical, lung, and ovarian cancers.
In a July conference call, Medivation talked up the value of talazoparib, saying that it has the potential to be "best-in-class" among so-called PARP inhibitors - a new type of medicine that blocks a particular enzyme that's used by our cells to repair DNA so that tumors can't survive.
Medivation's shares surged in early trading, rising almost 20% early Monday.
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