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The UK-based drugs company Glaxo Wellcome — which says that it has patented the idea of a single-nucleotide polymorphism (SNP) map of the human genome (see page 545) — has been attempting for some time to incorporate information about variations in gene sequences into its drug discovery programme.

The company became convinced of the feasibility of mapping the variations in nucleotide base pairs in 1997. Within four months, it had used an SNP map from late-onset Alzheimer's patients to narrow down a possible genetic basis for the disease to just two genes — ApoC1 and ApoE.

Over the past two years, the company has launched studies of patients with asthma and coronary heart disease, disorders whose genetic basis is less well known. In addition, it asks patients on clinical trials for many of its drugs for permission to include their genetic profiles in a future SNP database.

According to Allen Roses, a vice-president of Glaxo Wellcome and worldwide director of genetics, a more complete SNP map could establish a genetic basis for handling side effects of drugs.

Roses says doctors are reluctant to prescribe an anticonvulsant drug, Lamictal, because five per cent of patients develop a potentially fatal skin rash as a side effect. If a genetic basis for such side effects were found, patients could be screened, and the drug given to the majority not predisposed to developing the rash.