Genetic map indicates individualised drug therapies

By Wai Lang Chu

- Last updated on GMT

Related tags Dna

Scientists have described it as an achievement that will
revolutionise medicine as the first genetic "map" of human
diversity was published. The gene map, which details common
differences in the human genome, could lead to personalised
treatments for diseases.

Pharmacogenomics, as it is more commonly known, is the study of tailoring drug treatments to a person's genetic profile. It is said to be the future of drug research and development, paving the way for individualised treatment on an unprecedented scale.

It is based on the theory that drugs will act in a different way according to the patient's genetic make-up. Humans are genetically 99.9 per cent identical.

However, it is the 0.1 per cent difference that can hold clues to illnesses such as asthma, dementia and heart disease.

The "HapMap" study, which appears in the journal Nature, involved mapping the genome of 269 people, taking note of key areas of DNA.

The sample group was drawn from four different ethnic groups - the Yoruba tribe from Nigeria, residents of Tokyo, the Han Chinese from Beijing and European Americans from Utah.

By comparing every single possible mutation - single nucleotide polymorphisms - in each of the volunteer's DNA, the scientists produced the first comprehensive study of human genetic variation.

"This represents a milestone for medical research,"​ said David Altshuler of Harvard University, one of the leaders of the team to draw up the genetic map, published in the journal Nature.

"Such understanding is required for researchers to develop new and much-needed approaches to prevent, diagnose and treat diseases such as diabetes, bipolar disorder, cancer and many others,"​ he said.

Much of the genetic variation between individuals is caused by single letter differences in DNA called single-nucleotide polymorphisms (SNPs), of which there are thought to be around 10 million SNPs.

They are grouped into inherited families called haplotypes - that contain a unique battery of single mutations, which tend to be inherited together as a block.

The study identified 300,000 SNPs, which can provide around 90 per cent of the information obtained by looking at all 10 million.

"This report describes a remarkable step in our journey to understand human biology and disease,"​ explained Professor Peter Donnelly, Department of Statistics, University of Oxford and one of two corresponding authors on the report.

"The HapMap also provides unparalleled information about the targets of natural selection in the genome, and about the process of recombination, by which DNA from both our parents is combined and shuffled when we pass it on to our children,"​ he added.

Scientists are already using HapMap data, which is available on the Internet.

In March 2005, studies published in the journal Science used HapMap data to uncover a genetic variation that substantially increases the risk of age-related macular degeneration, the leading cause of severe vision loss in the elderly.

Other teams are using the data to look at conditions including diabetes, Alzheimer's disease, cancer, schizophrenia, asthma, high blood pressure and heart disease.

In addition, the progress of pharma is equally impressive, with a raft of companies using the HapMap data to produce the next generation of diagnostic tools and therapies.

Together with its subsidiary Genentech, Roche has produced a genetically engineered drug (monoclonal antibody) to block the action of this growth factor.

This means if this abnormality is identified before treatment, the patient can be given more specific, personalised treatment.

Roche's product MabThera/Rituxan, which has been used to treat leukaemia for some time now and for a percentage of rheumatoid arthritis sufferers, it has proved invaluable.

Roche introduced the first DNA chip (AmpliChip CYP450), which as the first DNA chip test in the world to receive regulatory approval represented a pioneering new discovery.

This test can be used to show whether people metabolise a drug faster or more slowly as a result of their genetic make-up.

The chip provides information that can aid the selection and dosage of a range of medications (for example, anti-depressants, psychopharmaceuticals, painkillers and drugs to treat cardiovascular disease).

Estimates indicate that systematic use of the AmpliChip test before treatment could improve overall efficacy by 10-20 per cent and avoid 10-15 per cent of all serious side effects.

Related topics Preclinical Research

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