ARIAD's Graft-vs-Host Disease Product Beginning Phase 2 Clinical Trial At Leading European Transplant Center.

Business/Health Editors

CAMBRIDGE, Mass.--(BUSINESS WIRE)--June 2, 2000

Preclinical and Phase 1 clinical data to be presented at

the American Society of Gene Therapy Annual Meeting

ARIAD Pharmaceuticals, Inc. (Nasdaq: ARIA) today announced approval to begin a Phase 2 clinical trial of the ARIAD Regulated Gene Expression Technology (ARGENT) product to treat graft-vs-host disease (GvHD) in patients undergoing allogeneic bone marrow transplantation (BMT) at the Hospital San Raffaele in Milan, Italy. Under the leadership of Professor Claudio Bordignon, the study's principal investigator and director of gene therapy and cell transplantation, this center has pioneered the development of innovative gene and cell therapies.

GvHD occurs when donor lymphocytes given with the BMT attack a patient's normal tissues and contributes substantially to the morbidity and mortality of allogeneic BMT. Susceptibility to GvHD depends, in part, on the dose of donor lymphocytes administered, the age of the recipient, and the degree of mismatch between the donor and recipient. Approximately 70% of patients do not have a family donor with a matched HLA phenotype, and thus many patients who could benefit from allogeneic BMT cannot receive this potentially curative therapy because of the risk of life-threatening GvHD.

The ARGENT GvHD product includes infusion of donor T lymphocytes engineered with a gene encoding an inactive apoptosis (cell death) protein. These engineered donor lymphocytes maintain their beneficial anti-tumor and anti-viral effects. However, they are programmed to undergo apoptosis in vivo upon treatment with ARIAD's gene-targeted drug, AP1903. AP1903 is expected to be effective in treating GvHD, since it should cause dose-dependent elimination of the donor lymphocytes responsible for the abnormal immune response.

Patients with chronic leukemia, lymphoma and multiple myeloma who have undergone allogeneic BMT, but have relapsed, will be the first patients entered into this clinical trial. They will receive infusions of ARGENT-engineered donor lymphocytes to induce remission and prolong survival. If they develop GvHD, they also will receive ARIAD's gene-targeted drug, AP1903, to selectively eliminate the disease-causing lymphocytes.

On June 3, 2000, at the American Society of Gene Therapy Meeting, Sarah Marktel, M.D. of the Hospital San Raffaele will present collaborative data with ARIAD supporting Phase 2 clinical development of the ARGENT cell therapy product to treat GvHD. The Phase 1 clinical data on AP1903 will be presented for the first time, as well as preclinical efficacy data demonstrating the ability of the ARGENT system to effectively eliminate human lymphocytes while maintaining their beneficial therapeutic effects.

ARIAD also announced today expansion of its ongoing collaboration with the gene therapy and cell transplantation program at the Hospital San Raffaele

involving the development of regulated gene therapies and the licensing of cell sorting and vector manufacturing technologies developed in Dr. Bordignon's program and owned by Roche. The technologies are being used in the ARGENT GvHD product. Under the terms of the agreement, ARIAD will receive a license to two patent applications covering these technologies and to all intellectual property and inventions made using ARIAD's technology as part of the collaboration.

"The availability of a selective therapy for GvHD in patients requiring donor lymphocyte infusions to treat neoplastic relapse should lead to lower mortality and morbidity post-transplant. Since donor lymphocyte infusion has been shown to result in higher overall cure rates and disease-free survival, the use of the ARGENT-based treatment should make this approach safer, more effective and available to more cancer patients than today," said Harvey J. Berger, M.D., chairman and chief executive officer of ARIAD. "In contrast to other therapies being studied in this disease, our ARGENT cell therapy product does not rely on immunosuppression to achieve its benefit."

ARIAD Pharmaceuticals, Inc. (www.ariad.com) is a leader in the discovery and development of gene therapy, cell therapy, stem cell therapy and protein therapy products featuring dose-dependent regulation by small-molecule drugs, as well as inhibitors of signal transduction pathways also using small molecules.

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 preclinical studies, the ability of the Company to conduct clinical trials of its products and the success of such trials, 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, 1999 filed with the Securities and Exchange Commission.