Pfizer's approach comes less than a week after Sanofi went public with its $52.50 per share cash offer, complaining that Medivation refused to engage. Medivation subsequently rejected the offer as too low. Its shares closed on Tuesday at $57.52.
Medivation has not yet decided whether it should engage with Pfizer in negotiations and is in discussions with its financial and legal advisers, the people said. There is no certainty that Pfizer will press ahead with a bid, they added.
Sanofi currently has no plans to raise its offer and is waiting for Medivation to launch an auction to sell itself before it makes any new bid, some of the people said.
The sources asked not to be identified because the matter is not public. Medivation, Sanofi and Pfizer declined to comment.
Based in San Francisco, Medivation is best known for its oncology drug Xtandi, which treats prostate cancer.
For Pfizer, a deal with Medivation would mark another attempt at building scale in patented drugs after it scrapped its $160 billion acquisition of Dublin-based Allergan last month.
The breakdown came days after the U.S. Treasury issued new rules that weighed on Pfizer's ability to slash its tax bill by using the deal to redomicile in Ireland.
Earlier on Tuesday, Pfizer Chief Executive Ian Read said in an interview with Reuters that he would consider another merger of any size, as long as the deal makes sense. He did not comment on Medivation.
Sanofi is vying for Medivation in an attempt to expand in the lucrative oncology sector, as it struggles to compensate for declining revenues from a key diabetes drug that recently lost patent protection.
Sanofi's unsolicited approach for Medivation has echoes of its bid for rare disease drug maker Genzyme in 2011. It took Sanofi nine months to overcome Genzyme's resistance. It also offered Genzyme shareholders so-called contingent value rights, which offered them additional payments if the acquired company was able to achieve certain performance milestones.
Using contingent value rights in the case of Medivation may be more challenging for Sanofi, given its lackluster track record in cancer drugs. However, Sanofi has no plans to use contingent value rights in any new offer, according to the sources.