Cephalon Inc. said today its experimental cancer drug Treanda was "significantly" more effective than a common chemotherapy drug in helping patients with chronic lymphocytic leukemia achieve remisson, based on a late-stage patient study.

The Frazer company presented the data at the American Society of Hematology meeting in Atlanta.

The remission rate among 305 patients in the study was 68 percent among patients taking Treanda, also known as bendamustine, compared with 39 percent in patients who received chlorambucil.

The disease, a slowly progressing cancer of the blood and bone marrow, has an estimated 15,000 new U.S. cases a year, according to the National Cancer Institute. Treanda, which is administered intravenously, is also being tested for non-Hodgkin's lymphoma and other cancers, Cephalon said.

The Food and Drug Administration has agreed to review Treanda on a priority basis, which can reduce the time it takes for a drug's approval. The most common side effect seen with the drug was low white blood count with fever and pneumonia, the company said.

Cephalon shares rose $2.04, or 2.67 percent, to $78.58 on the Nasdaq.

Contact staff writer Linda Loyd at 215-854-2831 or lloyd@phillynews.com.