ARIAD's Gene-Targeted Drug to Treat Graft-Versus-Host Disease Granted Orphan Drug Status by the FDA.

Business/Health Editors

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Feb. 24, 2000

Phase 2 clinical trial in bone marrow transplant patients

planned at Fred Hutchinson Cancer Research Center

ARIAD Pharmaceuticals, Inc. (Nasdaq: "ARIA") today announced that its gene-targeted drug, AP1903, has been granted orphan drug status for the treatment of acute graft-versus-host disease (GvHD) by the U.S. Food and Drug Administration (FDA). Orphan drug products have seven years of marketing exclusivity for the designated indications once they receive FDA regulatory approval, according to the Orphan Drug Act of 1983. AP1903 is a proprietary small-molecule drug used in the ARIAD Regulated Gene Expression Technology (ARGENT(TM)) GvHD product. A Phase 2 clinical trial of the ARGENT GvHD product in patients with chronic myeloid leukemia undergoing bone marrow transplantation is scheduled to begin at the Fred Hutchinson Cancer Research Center, Seattle with Stanley R. Riddell, M.D. as the principal investigator.

GvHD is a serious complication which often follows allogeneic bone marrow and stem cell transplantation (BMT), the treatment of choice for various hematologic malignancies. The effectiveness of this treatment has been attributed, in part, to the ability of cytotoxic donor T cells provided with the BMT to attack cancer cells. However, these T cells can attack the recipient's healthy tissue as well, which frequently results in a severe and often lethal complication known as GvHD.

The ARGENT GvHD product includes engineering of donor T cells to include a gene for an inactive apoptosis (cell death) protein. These engineered cells maintain their anti-tumor effect. They are programmed to undergo apoptosis only if the patient is treated with AP1903. A beneficial effect of AP1903 against GvHD is anticipated, since the disease-causing donor T cells should be eliminated in response to drug administration.

"Receiving orphan drug designation for AP1903 further strengthens the competitive position of our ARGENT GvHD product," said Harvey J. Berger, M.D., chairman and chief executive officer of ARIAD. "The upcoming clinical trial in patients with leukemia undergoing bone marrow transplantation should provide important insights into the utility of our product. This new gene therapy may decrease the need for steroids and immunosuppressive drugs in the treatment of GvHD and may improve the safety and broaden the utility of allogeneic BMT."

ARIAD Pharmaceuticals (www.ariad.com) is engaged in the discovery and development of gene-targeted therapeutics based on signal transduction technology. ARIAD is developing gene therapy products, regulated by small-molecule drugs, for protein and cell therapy based on its proprietary gene regulation and gene activation technologies including the ARGENT(TM) and RAPID(TM) systems. The Company also is developing orally administered small-molecule drugs to block intracellular signaling pathways that play a critical role in major diseases, such as osteoporosis and immune-related disorders.

Some of the matters discussed in this news release are forward-looking statements that involve risks and uncertainties, which include, but are not limited to, risks and uncertainties regarding the Company's ability to conduct clinical trials of AP1903, the success of such trials, and the Company's success in obtaining regulatory and marketing approval of such products, as well as risks and uncertainties relating to economic conditions, markets, products, competition, intellectual property, services and prices, key employees, future capital needs, dependence on our collaborators and other factors under the heading "Cautionary Statement Regarding Forward-Looking Statements" in ARIAD's Annual Report on Form 10-K for the fiscal year ended December 31, 1998 filed with the Securities and Exchange Commission.