The board of US biopharmaceuticals producer Medivation has unanimously rejected French drugmaker Sanofi’s $9.3 billion bid to acquire the company. David Hung, founder, president and CEO of the California-based prostate cancer specialist, said the cash offer, which he termed “opportunistically timed” as the company’s share price has deteriorated over the past several months, “substantially undervalues” the company.

Sanofi had offered to pay $52.50 a share in cash, which it said represented a 50% premium over Medivation’s two-month volume-weighted average. Despite the rejection, the French company indicated it is not prepared to abandon the hoped-for deal.

While Medivation “has chosen not to enter into discussions regarding this value-creating transaction,” Sanofi said it remains committed to the “compelling combination” and added that it is looking forward to “engaging directly with Medivation shareholders.” Sanofi said it is “a disciplined acquirer” and has a strong acquisition track-record.