Tm BIOSCIENCE LAUNCHES DRUG METABOLISM GENETIC TEST

TORONTO, ON, June 27, 2002 - Tm Bioscience Corporation (TSX Venture: TMC) announced today the launch of the Tag-It(tm) Mutation Detection Kit for P450-2D6 (or Drug Metabolism). This genetic test kit will be used to identify the presence or absence of important mutations common in patients with atypical drug metabolism, which can lead to adverse drug responses, a major cause of hospitalization. The Tag-It(tm) P450-2D6 test will provide diagnostic laboratories and drug developers with a cost-effective, accurate system to meet the growing demand for drug metabolism testing. 

"Drug metabolism testing is one of the fastest growing segments of the genetic testing market as pharmaceutical companies strive to identify patients predisposed to drug side effects and as regulators demand this enhanced drug safety data to minimize adverse drug reactions in the population," said Greg Hines, President and CEO of Tm Bioscience. "Our test is a highly accurate and comprehensive test for P450-2D6 genetic markers. This test is the promise of personalized medicine, and Tm is excited to be at the forefront of this rapidly emerging opportunity."

Many common prescription and over the counter drugs are affected by P450 enzymes. It is estimated that 20% of currently available prescription drugs are metabolized by P450-2D6 derived enzymes. The demand for genetic tests to identify the presence or absence of important mutations common in patients with atypical drug metabolism is growing rapidly, as drug developers and the medical community face increasing pressure from regulators to characterize patients for improved safety. Hospitalization for adverse drug reactions is the third leading cause of emergency room admissions in the United States.

"The innovative, multiplexed format of the Tag-It(tm) platform allows this test to be sold to the customer at a fraction of the cost of recently announced competitive products," continued Greg Hines. "The huge market potential for drug metabolism testing will only be realized if tests are marketed at a price that healthcare providers can afford to pay. Tm's P450 tests will be priced in alignment with international cost containment initiatives." 

Tm's announcement follows yesterday's announcement by the UK Department of Health who unveiled their £50 million ($113 million Cdn.) plan to transform healthcare with genetic testing and gene therapy (www.doh.gov.uk/genetics/whitepaper.htm ).

Tm Bioscience has in place a development and supply agreement with an unnamed U.S. customer for this product and expects to begin shipping in the next quarter. The Tag-It(tm) P450-2D6 test can be ordered directly from Tm Bioscience by calling 1 (800) 593-2370.

About Tm Tag-It(tm) Drug Metabolism Tests
The Tm Bioscience Tag-It(tm) Mutation Detection Kit for P450-2D6 will test for the 13 most important variants in the P450-2D6 gene. In addition to point mutations, the Kit will identify patients lacking one or both copies of the P450-2D6 gene (deletion patients) and those with multiple (greater than 2 copies) copies of the gene. More than 10% of Caucasians have mutations or a total absence of the P450-2D6 gene, resulting in significantly decreased drug metabolism, which can result in adverse drug reactions. Alternatively, duplication of the gene is known to cause "ultra rapid metabolism" rendering some drugs ineffective at commonly used dosages. 

The Company also recently announced the addition of two new drug metabolism tests to its development pipeline. The Tag-It(tm) Mutation Detection Kits for P450-2C9 and the Tag-It(tm) Mutation Detection Kits for P450-2C19 will test for mutations linked to atypical metabolism for a range of common prescription and over the counter medications. The Company anticipates that the Tag-It(tm) P450-2C9 test will be commercially available by the end of 2003 and the Tag-It(tm) P450-2C19 test in the first half of 2004.

About Tag-It(tm) genetic tests
The Tag-It(tm) genetic test series initially targets common genetic anomalies related to coagulation, cystic fibrosis and the cytochrome P450 drug metabolizing genes, with additional tests to follow as more genetic markers gain clinical acceptance. The Company's rapid and flexible kit design and development process combined with its integrated manufacturing operations allow the production of accurate, low cost, high-throughput genetic tests for use by commercial diagnostic laboratories.

About Tm Bioscience - Putting the Human Genome to Work(tm)
Tm Bioscience is a DNA-based diagnostics company developing a suite of genetic tests. Tm Bioscience's product pipeline includes tests for genetic mutations related to hematology, cystic fibrosis, toxicology and other debilitating genetic disorders. Tm Bioscience is located in Toronto, Ontario. Additional information about Tm Bioscience can be found at www.tmbioscience.com .

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James Smith
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jsmith@equicomgroup.com  

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