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Last Updated: Wednesday, 10 October 2007, 16:22 GMT 17:22 UK
The quest for bespoke medicine
By Connie St Louis

Pill tray
Scientists hope to develop individually-targeted drugs
It has been estimated most drugs work in only a third of patients, and around 10% of NHS beds are occupied as a result of adverse drug reactions.

That is the equivalent of seven large general hospitals full at any one time.

But scientists hope there may one day be a solution.

Instead of being handed a hit or miss pill, your doctor will do a test and then prescribe a drug that will work, because it will be specifically designed to suit your particular genes.

This approach - dubbed pharmacogenetics - is based on understanding how our genes act to control our body's response to drugs.

But it is still a discipline at an early stage of development.

How do you know how your genes will behave when confronted with a strange new chemical?

Mostly the answer is you don't.

But it is possible a person's origins may give a clue, and this is an idea currently being explored by the pharmaceuticals industry.

We certainly respond to drugs differently depending on our genetic make up. Take, for example, the widely used drug codeine.

When 10% of people take the painkiller, it doesn't work.

The other 90% of the population who take the medicine are able to break codeine down in their cells to make morphine and hence receive a significant amount of pain relief.

It turns out that those who can't turn codeine into morphine lack an enzyme that is controlled by their genes.

Scientists have found that the genetic mutation which renders codeine ineffective is much more common among northern Europeans, than those who hail from the Mediterranean.

But it would be as wrong to conclude that giving codeine to somebody from Malta would be bound to work, as it would to assume that giving it to a Swede would be a waste of time.

Heart failure drug

This, however, has not stopped scientists from developing and marketing medicines aimed at specific ethnic groups.

Gene analysis
Gene analysis is the key to tailor medicine

The first of these so called "race medicines" was BiDil, marketed by NitroMed and targeted at African-American's patients with heart failure and high blood pressure or hypertension.

It is a controversial approach. Some scientists think that using race as a kind of proxy for real pharmacogenetics is misguided.

Professor Sheldon Krimsky, of Tufts University, Boston, thinks that using race to assess a medicine's efficacy and safety is doomed to failure.

He argues that a race is a social construct and that people "self-define" their race by ticking a box from a list of categories.

Dr Paul Martin, from Nottingham University, said: "This approach is extremely problematic because scientific research hasn't shown any fundamental genetic difference between one racial group and another."

Although he does concede that there are significant differences in the way that geographical populations - if not races - metabolise drugs.

Population differences

BiDil is not the only ethnically-targeted drug. Iressa was developed by AstraZeneca to shrink tumours in small cell lung cancer.

It is currently only licensed for use in populations in Japan, China and south east Asia.

The drug acts by blocking a signal path believed to be important in the way cancer cells divide and develop into a tumour.

Initially, Iressa looked promising for all patients with this type of cancer, but when the drug underwent clinical trial the results were disappointing.

It produced an effect in only 10% of Western populations - but the success rate was twice as high among people from Japan, China and south east Asia.

Hence the drug has been targetted accordingly.

But what drug companies really want to do is to find out whether a drug is likely to work on an individual patient, rather than a whole population.

Professor Steve Jones, from University College, London University, says scientists need to focus on developing inexpensive, genetic tests.

That would end the need consider the characteristics of a race, or geographical population - all that would matter is whether the patient was carrying the key gene.

If that can be done, then we really could see the dawn of a new era of bespoke medicine tailored to the individual.

Ethnic Drugs - the Magic Bullet? is broadcast on BBC Radio Four on 10 October at 2100 BST.

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