Toronto, CANADA -- November 28, 2001 -- MDS Inc. (NYSE: MDZ; TSE: MDS) now provides cross-Canada access to therapeutic drug monitoring for the new anti-rejection drug sirolimus using state-of-the-art tandem mass spectrometry. This supports the MDS strategy of leading in the introduction of new technology in Canada and ensuring all Canadians have access to specialty diagnostic tests.

Sirolimus is a new immunosuppressant drug that significantly improves kidney transplant survival rates and reduces the toxic side effects on the patient. Monitoring of drug levels in the patient’s system is critical to patient care, and mass spectrometry is the most accurate way to perform these tests.

The sirolimus test is performed using the proprietary Applied BioSystems/MDS Sciex tandem mass spectrometry technology. The MDS Sciex mass spectrometer is a highly sensitive and sophisticated analytical instrument that is used to identify the molecular structure and chemical composition of substances.

Without immunosuppressant drugs, such as sirolimus, the patient’s normal immune response would reject a transplanted kidney. Patients often stay on these drugs for extended periods. Patients on these drugs need regular testing to ensure they have the right amount of drug in their blood. Like many other drugs, the optimal use depends on achieving the correct balance within a target therapeutic range. If the drug level is too low, the patient’s immune system may reject the kidney. If the drug level is too high, there may be toxic side effects from the drug itself.

The current global shortage in donor organs for patients needing kidney transplants makes it all the more important that each transplant is successful. The Canadian Organ Replacement Register estimates that there are approximately 2,900 Canadians currently on a waiting list to receive a kidney transplant.

“Therapeutic drug monitoring for sirolimus is critical in reducing both organ rejection and the level of toxicity following renal transplant. Using the most accurate and sensitive test allows the clinician to adjust the patient dose to be the most effective, ” noted Dr. Brian Sheridan, Vice President, Medical Affairs, MDS Laboratory Services.

MDS uses the highly sophisticated MDS Sciex liquid chromatography / tandem mass spectrometer (LC/MS/MS) instrumentation to measure sirolimus blood levels at the MDS International Reference Laboratory in Toronto, Canada. This instrument is a highly sophisticated instrument that can identify and quantify minute amounts of substances with great accuracy. In many cases, the MDS Sciex instrument can pick out, and accurately identify, one molecule from a trillion others; the equivalent of one drop of alcohol in the Toronto Sky Dome. The MDS Sciex instrument breaks substances into molecules, gives them an electrical charge (ionization) then measures the mass (weight and size) of each molecule along with the strength of the electrical charge. The resulting molecular ‘fingerprints’ are analyzed by sophisticated computers and compared to known molecular ‘fingerprints’ to identify the amount and type of substance in each sample.

MDS has facilitated breakthrough technological achievements for over two decades, and is the only company of its kind in Canada to manufacture precision scientific instrumentation for the development of pharmaceutical and life sciences products. In addition to sirolimus drug monitoring, MDS currently performs homocysteine testing on this sophisticated analyzer and is in the process of developing other new diagnostic testing applications for the mass spectrometer. Homocysteine levels are increasingly used as a marker of elevated risk for coronary heart disease, stroke, and venous thrombosis. It may also be helpful in the diagnosis of folate and B12 deficiencies.

“I am very pleased to see this technology increasingly take its place in diagnostics where the high accuracy and sensitivity will certainly help clinicians treat patients much more effectively,” said Andy Boorn, president of MDS Sciex.

Monitoring of sirolimus blood levels is recommended for patients following renal and liver transplant, for pediatric patients, for those with hepatic (liver) impairment and for those patients receiving certain drug combinations.

MDS is working with transplant centres across Canada to ensure national access to the MDS drug monitoring service for sirolimus.

About the MDS Diagnostic Sector and MDS Inc.

As a part of MDS Inc., the MDS Diagnostic Sector is a leading provider of diagnostic laboratory services in North America. In Canada, MDS provides national access to a comprehensive menu of diagnostic and laboratory tests. These tests range from routine tests such as glucose testing for diabetes, to more complex testing such as hepatitis or Helicobacter pylori testing, and then on to new, highly specialized tests, for example, the patented genetic predisposition testing for cancers. For more information on the MDS Diagnostic Sector visit www.mdsdx.com

MDS Inc. (NYSE: MDZ; TSE: MDS) is an international health and life sciences company. The MDS focus is on using science to advance health. It does this by providing: laboratory testing, imaging agents for nuclear medicine testing, sterilization systems for medical and consumer products, research services to speed discovery and development of new drugs, therapy systems for planning and delivery of cancer treatment, analytical instruments to assist in the development of new drugs, and medical/surgical supplies. For more information on MDS, visit http://www.mdsintl.com.

For further information: Contact: Patricia Everitt, Director of External Communications, MDS Diagnostic Sector, (416) 213-4258, peveritt@mdsintl.com