The French drugmaker on Wednesday filed preliminary documents with the Securities and Exchange Commission (SEC) looking to remove and replace Medivation’s entire board. The California-based cancer therapy maker rejected a $9.3 billion takeover bid by Sanofi in April and has spurned its subsequent overtures, leading Sanofi to threaten ousting Medivation’s board earlier this month.

“Despite multiple attempts, both prior to and following the public disclosure of Sanofi’s proposal, Medivation has thus far refused to engage with us regarding the merits of a value creating transaction,” said Sanofi chief executive Olivier Brandicourt in a statement. “Unfortunately, this has left us with no choice but to commence a process to elect directors who are more open to supporting the best interests of Medivation shareholders regarding a potential transaction.”

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Sanofi’s eight board nominees include Michael E. Campbell, a current director at packaging giant WestRock (WRK), and former top Shire (SHPG) exec Barbara Deptula, among others.

The Medivation deal has been a top priority for Sanofi and Brandicourt as the firm attempts to shore up its oncology franchise in the wake of troubles in its diabetes and cardiovascular segment. On Monday, the company announced a reorganization of its executive committee, including the departure of diabetes and cardiovascular unit head Pascale Witz.

Medivation has just one approved therapy, the prostate cancer drug Xtandi. But a number of major biopharma players have been eyeing the company as a potentially lucrative takeover target. The U.K.’s AstraZeneca and American pharma giant Pfizer (PFE) have both reportedly explored a buyout. And on Wednesday, Bloomberg cited unnamed sources saying that U.S. biotech giants Gilead (GILD) and Celgene (CELG) are also considering their own Medivation offers, raising the specter of a bidding war.

Sanofi’s announcement did little to sway its defiant target. “Sanofi is seeking to take control of our Board in a clear attempt to circumvent objective deliberations over what course of action is in the best interests of all Medivation stockholders,” said Kim Blickenstaff, chair of Medivation’s board, in a statement. “The unattractive economics of Sanofi’s proposal – which the Board has already determined to be substantially inadequate – have not changed.”