* Medivation board unanimously rejects $9.3 bln Sanofi offer
* Says $52.50/share undervalues cancer firm "substantially"
* Sanofi commits to deal, ready to take case to shareholders (Recasts following new statements from both parties)
By Matthias Blamont
PARIS, April 29 (Reuters) - Sanofi and its takeover target Medivation dug in for trench warfare on Friday, with the French drugmaker confident of winning over investors and the U.S. cancer firm insisting it was better off staying independent.
Sanofi, which has a track record of winning hostile fights in the biotech sector, said it was ready to speak directly to Medivation shareholders about its spurned $9.3 billion offer.
"While to date Medivation has chosen not to enter into discussions regarding this value-creating transaction, Sanofi remains committed to the combination," it said.
In its first pronouncement on the subject since Sanofi confirmed its approach on Thursday, Medivation rejected the $52.50-a-share proposed offer outright, which it said undervalued the company "substantially".
"Our board strongly believes that Medivation's business plan will deliver value to our stockholders that is far superior to Sanofi's offer and unanimously rejects your proposal," it said.
Sanofi went public with its offer for the maker of the blockbuster prostate cancer drug Xtandi after failing to get Medivation management to engage.
"We are confident that Medivation shareholders will ultimately share our strong belief that our offer ... would provide significant and immediate cash value," Sanofi Chief Executive Olivier Brandicourt said on a conference call.
He was speaking as Sanofi reported higher quarterly profit on Friday, boosted by its Genzyme division, another U.S. biotech business acquired after a protracted fight in 2011.
Chief Financial Officer Jerome Contamine declined to say whether Sanofi was ready to engage in a bidding war for Medivation and raise its offer, as many investors expect it to do.
Still, shares in Sanofi fell 5 percent, with worries about it getting sucked into a costly and lengthy takeover battle fuelling the decline, traders said.
Industry analysts and healthcare bankers believe Sanofi will need to sweeten its opening offer if is to win its prey, since Medivation shares are already trading $4 above its $52.50 offer.
"I imagine you'll see a fair bit of movement," said one banker not directly involved in the situation. "It's fairly typical to see an average 10 percent premium to the original offer - I think this is going to get much higher."
CVRs, or contingent value rights, might also be deployed, the banker said, as happened when Sanofi bought Genzyme for $20 billion after a similar unsolicited approach.