24 April 2007

One Pill to Treat 1800 Genetic Diseases?

Within the next three years, PTC Therapeutics plans to offer PTC 124 to treat over 1800 genetic diseases.
As well as offering hope of a first effective treatment for two conditions that are at present incurable, the drug has excited scientists because research suggests it should also work against more than 1,800 other genetic illnesses.

PTC124 targets a particular type of mutation that can cause very different symptoms according to the gene that is disrupted. This makes it potentially useful against a range of inherited disorders.

The same drug could be given to patients with Duchenne muscular dystrophy, the most serious form of the muscle-wasting condition, cystic fibrosis, which mainly affects the lungs, and haemophilia, in which the blood does not clot. It can be taken orally, and safety trials have not revealed any major side effects.

“There are literally thousands of genetic diseases that could benefit from this approach,” Lee Sweeney, of the University of Pennsylvania, who is leading the research, said. “What’s unique about this drug is it doesn’t just target one mutation that causes disease, but a whole class of mutations.”

....PTC124 works by binding to a part of the cell called the ribosome, which translates genetic code into protein, and allows it to ignore nonsense mutations. The gene can be read straight through and a normal protein is produced.

The beauty of the drug is that it should be useful with any disease caused by a nonsense mutation, no matter what its outward effects. The error is not corrected, but ignored. Patients would have to take the pill throughout their lives.

PTC124, which is made by PTC Therapeutics, has been staggeringly successful in animal models. A study published today in Nature shows that in mice with a nonsense mutation that causes Duchenne muscular dystrophy, the drug starts dystrophin production and restores their muscles to health.

The drug has passed safety trials in humans, and the results of phase-two trials on cystic fibrosis and Duchenne muscular dystrophy will be published shortly.

This ribosome targeting approach may eventually palliate between 5% - 15% of genetic disorders. Other approaches to gene therapy would target different parts of the gene expression network. This drug reveals how many possible approaches to treating genetic conditions there must be.

Using viral and non-viral vectors to replace faulty DNA in the nucleus is the most straightforward approach. But the potential for gene therapy exists from nuclear DNA to transcription factors and enzymes to RNA in coding and noncoding forms, to proteomics, to glycomics, etc.

Pharmaceutical companies exist to make a profit. If crusading politicians are allowed to remove the profitability from the pharma business, the number of approaches taken in the laboratory to solve these disease problems will drop significantly. In other words, we will be stuck with "local optima," when better possibilities existed but were not pursued for lack of backing.

In a market, profit-driven economy, multiple approaches are taken. In a state-planned economy, singular approaches are taken. Watch your politicians closely to determine which type of economy they favour.

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