Early results from a pivotal trial of Ariad Pharmaceuticals Inc's experimental leukemia drug ponatinib show it is effective in nearly half of patients who had stopped responding to currently available drugs.

An interim look at the study, presented here at a meeting of the American Society of Hematology, shows that 47 percent of chronic myeloid leukemia (CML) patients with chronic-phase disease had a major response to ponatinib, meaning that at least two-thirds of their bone marrow was normal.

Thirty-nine percent of those patients achieved complete remission of their leukemia, a cancer of the bone marrow.

The trial involves 449 patients -- the interim results are from 392 subjects -- who had stopped responding to treatment with Sprycel, sold by Novartis AG, and Bristol-Myers Squibb Co's Tasigna.

Both of these older drugs, respectively known generically as dasatinib and nilotinib, are members of a class called tyrosine kinase inhibitors.

Ariad's drug is designed to target an abnormal tyrosine kinase that is closely associated with CML and Philadelphia chromosome positive acute lymphoblastic leukemia.

Side effects seen in the trial included rash (in 32 percent of patients), thrombocytopenia (31 percent), dry skin (24 percent), abdominal pain (19 percent), and headache (17 percent).

Ariad said 6 percent of patients developed pancreatitis, inflammation of the pancreas, but all of them were able to remain in the trial.

Researchers said the deaths of four patients, all of whom had advanced leukemia and other serious medical conditions, may have been related to treatment with ponatinib.

The side effect profile is every bit as good as other drugs in this class, said Ariad Chief Executive Officer Harvey Berger.

Ariad plans to file for U.S. regulatory approval of ponatinib in mid-2012 based on the mid-stage trial results.

Berger said the company will decide in the first quarter of next year whether to secure a European partner for the drug, and remains committed to commercializing it on its own in the United States.

The CEO also said Ariad will launch next year a trial of ponatinib in newly-diagnosed patients.

Cancer Leukemia Cancer