ARIAD Announces Major Advances in Development of its Lead Cancer Product Candidate, AP23573; Reported at the American Society for Clinical Oncology Annual Meeting.

Business Editors/Health/Medical Writers

CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 30, 2003

ARIAD Pharmaceuticals, Inc. (Nasdaq: ARIA) today announced, for the first time, results of comprehensive in vivo studies of AP23573, its lead cancer product candidate which is in Phase 1 clinical trials. AP23573 was highly effective in animal models of human solid tumors: treatment initiated at an early stage of tumor growth induced persistent tumor regression of up to 90%, and treatment at a later more-aggressive stage still produced significant reductions in the rate of growth of all six tumor types studied (i.e., brain, prostate, breast, pancreas, lung, and colon cancers).

The research also demonstrated that the anti-cancer activity of three widely used chemotherapy drugs was markedly enhanced by combined treatment with AP23573, supporting the use of AP23573 in multi-drug regimens that can be tailored to treat specific cancers.

The small-molecule, AP23573, was designed to have broad clinical applications in solid tumors and other malignancies by inhibiting the protein mTOR leading to shrinking of tumors by a novel mode of action - cancer-cell starvation (metabolic arrest) through inhibition of nutrient uptake to tumor cells, as well as inhibition of growth factor stimulation. AP23573 can be administered orally or by injection.

Molecular analysis of tumors removed from the animals dosed in the studies reported today showed that mTOR signaling was completely abolished one day after a single low dose of AP23573 and that this suppression persisted for 2 to 3 days. These findings form the basis for using biomarkers to determine patterns of responsiveness to AP23573 therapy in clinical trials of patients with cancer.

"We continue to build a strong scientific foundation for the clinical use of AP23573, alone and in combination with other anti-cancer drugs, in a broad spectrum of solid tumors and other malignancies," said Harvey J. Berger, M.D., chairman and chief executive officer of ARIAD.