The Food and Drug Administration said it has approved Talon Therapeutics Inc's Marqibo treatment for adults with a rare form of leukemia known as Philadelphia chromosome negative acute lymphoblastic leukemia.

The drug, a targeted version of generic chemotherapy drug vincristine, will be the first commercial product for Talon.

The company is majority-owned by Warburg Pincus and Deerfield Management, but shares accounting for a minority portion of its equity trade over-the-counter and were down 5 percent in afternoon trading.

Talon licensed Marqibo in 2006 after the FDA turned down an application for the drug, filed by two other companies, as a treatment for relapsed non-Hodgkin's lymphoma.

Thursday's FDA approval is for acute lymphoblastic leukemia patients who have failed at least two other therapies.

Talon's shares, which were down 5 percent at 92 cents, have more than doubled so far this year.