The cancer drug maker's shares popped 14% by midday, hitting $186.60 apiece on reports by Reuters that the company is speaking with investment banks, including Citigroup, about a potential deal. The report noted that Tesaro is not yet seeking a sale.
Tesaro and Sanofi could not be reached for immediate comment on a potential deal.
The biotech, which has a market cap of $9.56 billion, has long been seen as a target for M&A by investors and analysts.
In November, TheStreet's sister website, The Deal, reported that Tesaro could be a sensible target for Gilead (GILD) - Get Gilead Sciences, Inc. (GILD) Report , which is sorely in need of additional assets in its pipeline. Tesaro could be especially valuable for its PARP inhibitor for the treatment of cancer, analysts said at the time.
Of note: private equity firm Ally Bridge Group Capital invested $155 million in Tesaro in February 2016.
Clovis has also been long seen as a takeover target in the oncology drug development space. Eli Lilly (LLY) - Get Eli Lilly and Company (LLY) Report and Merck (MRK) - Get Merck & Co., Inc. (MRK) Report have been seen as buyers for Clovis, in part because neither one was unable to close a deal with Medivation (MDVN) , which was acquired by Pfizer (PFE) - Get Pfizer Inc. Report for $14 billion just last year.