(Reuters) - The U.S. Securities and Exchange Commission filed an insider trading lawsuit on Friday against "unknown traders" who it said engaged in "highly suspicious trading" just ahead of the announcement that hemophilia specialist Bioverativ Inc had agreed to be acquired by France's Sanofi in an $11.6 billion deal.

According to the lawsuit, filed in U.S. District Court in Manhattan, the defendants, who may be foreign traders, made "highly suspicious, timely, and lucrative purchases and sales of options on Bioverativ stock," generating profits of about $4.9 million.

The SEC said the options purchase orders originated through a foreign brokerage firm located in Zurich in the name of Credit Suisse (Switzerland) Ltd and were cleared through Credit Suisse Securities (USA) LLC, which executed the orders through a domestic options exchange.

Bioverativ agreed to be acquired by Sanofi for $105 a share, which represented a premium of 64 percent over Bioverativ's closing share price on the last trading day ahead of the announcement. Its shares closed up 61.9 percent on Jan. 22, the day the deal with Sanofi was announced, the lawsuit noted.

The SEC said it seeks an order to freeze the assets of the traders, require the identification of the defendants and the repatriation of assets. The SEC in the lawsuit also said it is also seeking disgorgement of all ill-gotten gains.

(Reporting by Arunima Banerjee in Bengaluru; Editing by Leslie Adler)