BioTransplant And The Massachusetts General Hospital Announce Award Of U.S. Patent Covering A Unique Approach To Transplantation And Blood Cell Cancers

Patent Represents Important Advance In Development Of Clinically Acceptable Procedures

Charlestown, MA PRNewswire -- BioTransplant Incorporated and its collaborator, The Massachusetts General Hospital (MGH), announced today the award of a patent which covers BioTransplant's novel approach to transplantation and blood cell cancer treatments. The U.S. patent (no. 6006752), titled "Mixed Chimerism and Tolerance," was issued to Megan Sykes, M.D. of MGH and licensed exclusively to BioTransplant. The technology covered in the patent is designed to re-educate a recipient's immune system to accept donor cells and organs as "self". The Company believes this technology has the potential to expand the number of blood cell cancer and organ transplant patients who can be treated, produce fewer side-effects in these patients, and reduce or eliminate the need for long-term immunosuppressive drug treatments.

Megan Sykes, M.D., Immunologist at the Transplantation Biology Research Center, MGH, and Professor at Harvard Medical School, added, "Our goal is to develop approaches that will allow patients to accept donor cells and organs without rejection and address the critical shortage of acceptable donor bone marrow cells and organs. This approach has important implications for transplantation between mismatched donors and recipients, where the 'bar' is higher for achieving long-term tolerance."

The patent covers methods of promoting functional tolerance (recognizing the donor tissue as "self") in humans to grafts from human and non-human donors through the creation of mixed chimerism. These methods include preparatory, conditioning regimens that do not require whole-body irradiation, and reduce or eliminate the need for immunosuppressive drug treatments. BioTransplant's patent portfolio includes previous patents issued to MGH and licensed to BioTransplant covering its AlloMune(TM) and XenoMune(TM) Systems for achieving functional tolerance in human-to-human and cross-species transplantation, respectively.

"Combined with the patent issued last March, the award of today's patent strengthens BioTransplant's proprietary position in applying our approach to transplantation and treatment of blood cell cancers," said Elliot Lebowitz, Ph.D., President and Chief Executive Officer of BioTransplant. "The award of patents is significant as we advance our products towards commercialization, while continuing to work with the medical community to improve the transplantation of cells, tissues and organs."

Current Challenges

Bone marrow transplant patients often experience graft-versus-host (GvHD) disease while other patients are unable to withstand the harsh and debilitating preparation that the current procedures require to completely destroy the bone marrow by chemotherapy or radiation in addition to long-term immunosuppressive drug treatment. Currently, organ transplant patients require life-long immunosuppressive drug treatment, with associated side effects and complications. In addition, many patients are unable to benefit from organ transplantation because of the shortage of human donor organs.

To address these challenges, MGH researchers, in collaboration with BioTransplant, are developing conditioning regimens to allow the establishment of mixed hematopoietic chimerism in patients without the use of whole-body irradiation. This regimen can be applied to the treatment of blood cell cancers, potentially increasing the number of patients that are eligible for transplant, increasing the donor pool and increasing the anti-tumor response. Use of BioTransplant's procedure in organ transplant recipients may potentially allow the elimination of chronic immunosuppressive drug use in human organ transplantation, and when applied to cross-species transplantation (xenotransplantation), may allow the use of organs from porcine donor animals. In addition, the protocol could potentially be applied to mismatched human donor/recipient pairs, expanding the number of patients who could be treated and decreasing the dependence on immunosuppressive drug treatments.

Preliminary Data

In proof-of-principle studies published in The Lancet, MGH researchers have demonstrated that it is possible to transplant bone marrow successfully from mismatched human donors without the usual amount of pre-transplant destruction of the patient's own bone marrow. The scientists successfully induced a state of mixed chimerism (in which the immune systems from both donor and recipient are blended) in the four evaluable of five enrolled patients with aggressive non-Hodgkin's lymphomas who failed other treatment methods. Two of the patients achieved long-term remission without significant GvHD, an often fatal complication of bone marrow transplantation. In a separate MGH study, published in the journal Transplantation, researchers successfully induced a state of immune tolerance in a double transplant recipient (bone marrow and kidney), enabling the patient to discontinue immunosuppressive drug treatment without rejecting the transplanted kidney. In addition, there was no sign of GvHD and no detectable evidence of the previously existing myeloma.

ImmunoCognance(TM) Approach

BioTransplant's approach to transplantation, functional tolerance, (ImmunoCognance(TM)), is based on work pioneered by David H. Sachs, M.D. of MGH. ImmunoCognance(TM) may allow the recipient's immune system to accept donor tissue as "self" without compromising the recipient's immune defenses. This is achieved by mixing elements of the donor's immune system with that of the recipient. The AlloMune(TM) Transplant System, for human-to-human transplantation, and the XenoMune(TM) System for the transplantation of organs from BioTransplant's proprietary miniswine into humans, contains a number of advanced approaches which are designed to facilitate the acceptance of donor tissue by the human immune system.

BioTransplant Incorporated utilizes these proprietary technologies in re-educating the body's immune responses to allow functional tolerance of foreign cells, tissues and organs. Based on this technology, the Company is developing a portfolio of products designed to treat a range of medical conditions, including organ and tissue transplantation, cancer and autoimmune disease, for which current therapies are inadequate. BioTransplant's products are intended to induce long-term functional transplantation tolerance in humans, increase the therapeutic benefit of bone marrow transplants, and reduce or eliminate the need for lifelong immunosuppressive therapy.

This announcement may contain, in addition to historical information, certain forward-looking statements that involve risks and uncertainties. Such statements reflect management's current views and are based on certain assumptions. Actual results could differ materially from those currently anticipated as a result of a number of factors, including risks and uncertainties discussed in the Company's filings with the U.S. Securities and Exchange Commission.

NOTE: Patent No. 5,876,708 issued on March 2, 1999 to The Massachusetts General Hospital and licensed exclusively to BioTransplant, covers key technologies relating to BioTransplant's AlloMune(TM) and XenoMune(TM) Systems.

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