Ariad drug proves effective in curbing chronic leukemia in study

* 56 pct of chronic patients achieved "major response"

* US FDA decision expected by March 27

Dec 9 (Reuters) - An experimental leukemia drug from Ariad Pharmaceuticals Inc eliminated the cancer from the bone marrow of nearly half of patients with a chronic form of the disease who had stopped responding to other drugs, according to a 12-month follow-up of a pivotal drug trial.

The trial of the drug, ponatinib, which involved 444 patients, including 267 with chronic myeloid leukemia who had previously been treated with older drugs, also showed that 56 percent of chronic patients achieved the study's goal of a "major response," meaning the disease had nearly disappeared from the bone marrow.

Ariad earlier this year presented interim results from the trial, and U.S. Food and Drug Administration agreed in October to an expedited review. The agency is slated to decide by March 27 whether to approve ponatinib.

"We expect FDA approval sometime in the first quarter," said Tim Clackson, Ariad's chief scientific officer. He said the company is prepared to immediately launch sales of the drug. "We believe the overall trial data suggests activity in all forms of resistant disease."

Ponatinib is designed to target an abnormal tyrosine kinase that is closely associated with chronic myeloid leukemia and Philadelphia chromosome positive acute lymphoblastic leukemia.

Ariad is also testing the drug in newly diagnosed CML patients. Final results from that trial are expected at the end of 2014, but an interim analysis will occur after half of the trial patients are enrolled, Clackson said.

Around 5,000 U.S. patients are diagnosed with CML each year, and about 2,500 patients will become resistant to their treatment, according to Ariad.

(Reporting By Deena Beasley; Editing by Leslie Adler)