Repurchasing L'Oreal's 9 % stake in Sanofi might make sense for the French drugmaker if the $12 billion holding is put up for sale, Sanofi's chief executive said.

Chris Viehbacher told an investor conference the group had the resources to do "opportunistic" share buybacks, as well as making bolt-on acquisitions and potentially increasing its stake in U.S. biotech firm Regeneron Pharmaceuticals.

Speculation over the fate of L'Oreal's stake in Sanofi has been fuelled by comments from L'Oreal's CEO, who said last month that the cosmetics company could buy back the $30 billion stake Nestle holds in it if L'Oreal in turn sold the €9 billion stake it owns in Sanofi.

Asked about his potential interest in buying back L'Oreal's stake, Viehbacher said it was difficult to comment because the issue was highly conditional.

Viehbacher said he did not exclude other share buybacks, but said these would depend on opportunities for acquisitions. Sanofi could also look at raising its stake in Regeneron to as much as 30 %. Sanofi holds about 16 % of Regeneron and said in February it has the right to increase this to a maximum 30 % under its decade-long partnership with Regeneron.

"The Regeneron relationship has become extremely productive for us," Viehbacher said. "Over time, it could well make sense to build our stake up to 30 percent. How fast we do that, whether or not we do that is a function of a number of different factors - but it is a bulky chunk of money to use."

Regeneron's market value is about $27 billion.