Sanofi, the French pharmaceutical giant, announced Thursday it had written to U.S. biotech firm Medivation, making an offer to acquire it for $9.3 billion in an all-cash deal. The proposal values Medivation at $52.5 per share, a more than 50 percent premium to Medivation’s two-month volume weighted average price before takeover rumors began, according to the Sanofi statement.

In the letter sent to Medivation, made public by Sanofi along with its statement, Olivier Brandicourt, CEO of the French company, said “oncology plays an important role” in its “strategic roadmap for 2020.”

“As we aim to further develop our capabilities in this important area, we believe that Medivation represents a very strong fit and, together with our own clinical pipeline and existing infrastructure, will play an important role in our long-term strategy in oncology,” Brandicourt wrote in the letter.

Brandicourt first spoke about his intention to acquire Medivation with its CEO David Hung on March 25, when Hung expressed his unwillingness to meet Brandicourt, and after a board meeting a few days later, Hung told Brandicourt that Medivation wasn’t interested in discussing a transaction, according to the letter.

San Francisco-based Medivation has one marketed prostate cancer drug, Xtandi, and two more cancer drugs in development. Reports earlier this month suggested that AstraZeneca was also holding internal talks to discuss a bid for Medivation.

The U.S. biotech company’s prostate cancer drug makes it attractive for acquisition, given that prostate cancer is the second-most common cancer among men and one of every seven men is expected to be diagnosed with the disease during their lives.

Medivation shares had closed 0.44 percent higher on Nasdaq Wednesday and were trading 2.31 percent higher at 4:12 a.m. EDT in premarket trade Thursday. Meanwhile, Sanofi shares were trading over 2 percent lower in Paris during Thursday morning trade.