CHICAGO ( TheStreet) -- Ariad Pharmaceuticals ( ARIA) will report improved tumor response rates to its leukemia drug ponatinib during a presentation later today at the American Society of Clinical Oncology (ASCO) annual meeting. The new ponatinib data come from an update of the "PACE" pivotal study in chronic myeloid leukemia (CLL) and Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL). All patients in the trial either resistant to Novartis' ( NVS) Tasigna or Bristol-Myers Squibb's ( BMY) Sprycel, or who have a specific genetic mutation known as T315I that makes the leukemia resistant to current therapies. Ariad expects to seek regulatory approval in the U.S. and Europe in the third quarter, the company said. Following treatment with ponatinib and with a median follow-up of 10 months, 54% of CML patients with chronic phase disease had a major cytogenic, or cellular, response, meaning a reduction in the number mutated cells to less than 35%. Last December, 47% of these patients reported a similar response. In the subgroup of patients with the T315I mutation, the major cytogenic response rate was 70%, up from 65% last December. The incidence of pancreatitis, a closely watched adverse event, remained unchanged at 6%. A more detailed presentation of the latest ponatinib data are scheduled for 10 am EDT at the ASCO meeting. CML and Ph+ ALL are cancers in which a genetic abnormality produces excessive quantities of a protein known as BCR-ABL. This, in turn, causes bone marrow to generate too many white blood cells. --Written by Adam Feuerstein in Chicago. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: firstname.lastname@example.org. Follow TheStreet on Twitter and become a fan on Facebook.