The decision to target Medivation (MDVN) marks a return to the biotech takeover trail by Sanofi (SNYNF), which is looking to new cancer treatments to bolster its portfolio and help offset declining sales of its mainstay diabetes drug Lantus.

Sanofi’s non-binding proposal is to buy Medivation for $52.50 per share in cash, representing a 50% premium over the San Francisco-based firm’s two-month volume-weighted average share price prior to takeover rumors.

It is, however, only modestly above Medivation’s Wednesday closing price of $52.05, reflecting a run-up in the stock in recent weeks on bid talk.

Reuters reported last month that Medivation had been working with investment bank JPMorgan to handle interest from companies regarding a potential acquisition, but it had no plans to sell itself.

Sanofi and Britain’s AstraZeneca were among companies reported to have looked at Medivation.

Bryan Garnier analyst Eric Le Berrigaud said Sanofi could now face a lengthy takeover fight with other players potentially getting involved, including Astellas Pharma, Medivation’s partner on its prostate cancer drug Xtandi.

Stepping up acquisitions fits with the strategy of Sanofi Chief Executive Olivier Brandicourt, who took over a year ago. He told Reuters in January that he was looking for deals to broaden its reach in areas such as oncology.

France’s biggest drugmaker is going through a tough patch, due to falling sales of Lantus, prompting it to warn of no meaningful profit growth over the next two years and spurring Brandicourt’s drive to focus on priority areas like cancer.

Oncology is currently the hottest area of pharmaceutical research, thanks to advances in understanding the biological drivers of the disease.

‘Compelling’ Proposal

Brandicourt first contacted Medivation about a deal on March 25 but he said Chief Executive Officer David Hung had declined to meet him and had told him the U.S. company’s board was not interested in discussing a transaction.

Sanofi then set out its $52.50-a-share offer in an April 15 letter to Hung, to which Medivation only acknowledged receipt without commenting on its contents.

“We do not understand the delay in responding to our letter. The price we put forth represents a very substantial premium, and it would be all cash without any financing condition. In these circumstances we believe it is appropriate to make this letter public, which we are doing today,” Brandicourt wrote.

“We also strongly believe that Medivation shareholders would find our proposal to be compelling.”

The French company said that there was no certainty the Medivation deal would get done, but that if it did, it would boost earnings immediately.

Last month Sanofi poached one of AstraZeneca’s top scientists, a specialist in immunology and oncology, to be its new research head.

Xtandi is Medivation’s only marketed drug but it has two other cancer treatments in clinical development. The high price of Xtandi has been criticised by some U.S. lawmakers, including Democratic Party presidential hopeful Bernie Sanders.

The global pharmaceutical industry has seen a flurry of deal-making in the past two years, as large companies try to focus on a smaller number of businesses where they can establish a leading position, often by snapping up young biotech firms.