Ariad Pharmaceuticals Inc announced the results of pre-clinical studies demonstrating the potency and activity of AP23464, its product candidate to treat life-threatening forms of blood cancer: AP23464 is over 10-fold more potent than imatinib (Gleevec), the leading product for chronic myeloid leukemia (CML), in blocking the activity of the key cancer-causing protein responsible for Gleevec's efficacy.

Furthermore, unlike Gleevec, AP23464 is designed to block additional leukemia therapeutic targets that become increasingly important in patients who no longer respond to Gleevec - an outcome that occurs in approximately 75% of advanced-stage CML patients treated with Gleevec for two years. In spite of these limitations, sales of Gleevec are estimated to reach approximately $1 billion in 2003.

Based on its targeting of oncogenic proteins, AP23464 may provide a compelling alternative to Gleevec - both for Gleevec-resistant patients and as primary therapy for certain forms of leukemia.

"The success of Gleevec, described as a 'magic cancer bullet,' highlights the importance of selecting the right therapeutic targets for new cancer therapies. We are focused on development of our molecularly targeted drug for blood cancer to be Ariad's next product candidate to enter clinical trials," said Harvey J. Berger, chairman and chief executive officer of Ariad.

The malignant transformation in bone marrow cells that leads to certain forms of leukemia is dependent on the activity the Abl protein. Dr. David Baltimore's research group discovered the cancer-causing properties of the Abl protein in the mid-1980's. Dr. Baltimore is one of Ariad's founding scientific advisors. Recent clinical studies have found that genetic variants of Abl develop during Gleevec treatment. While Gleevec does not affect these variant proteins or the Src protein, an important cell-signaling partner of Abl, AP23464 is designed to block these proteins.