Eli Lilly and Co.’s patent- infringement claim over Hospira Inc.’s generic version of the cancer treatment Gemzar will be investigated by a U.S. trade agency with the power to block imports of the copycat drug.

The U.S. International Trade Commission in Washington, D.C., said Thursday it will probe the complaint Lilly filed Jan. 20. Indianapolis-based Lilly claims Hospira’s gemcitabine, Gemzar’s active ingredient, infringes a patent that doesn't expire until February 2014.

Global sales of Gemzar, used to treat lung, breast, pancreatic and ovarian cancer, dropped 22 percent, to $243.6 million, in the fourth quarter, Lilly reported Jan. 27. Lake Forest, Ill.-based Hospira began selling gemcitabine in November after Lilly lost an appeals court ruling that said a separate patent expiring in May 2013 was invalid.

The patented method is “the most commercially viable process available for manufacturing gemcitabine” and “involves less steps, higher yields and lower costs,” Lilly said in its complaint.

Hospira sued Lilly in September, seeking a court ruling that its process wouldn’t infringe the patent. That case is pending in federal court in Chicago.

The Lilly ITC complaint also names Hospira suppliers Jiangsu Hansoh Pharmaceutical Co. of China, Intas Pharmaceuticals Ltd. of India and ChemWerth Inc. of Woodbridge, Conn. According to Lilly, Hansoh makes the active ingredient, ships it to India where it’s formulated into the drug before being sent to ChemWerth for sale by Hospira.