That's where PTC124 comes in: it was designed from the start to have similar properties to gentamicin but to be safer and more easily absorbed. "We are really in a different situation now, where we are trying to identify drugs based on how they should act," says Langdon Miller, chief medical officer of PTC Therapeutics in New Jersey.
The drug was screened out of a pool of 175,000 synthetic molecules. Pre-clinical tests so far indicate that it is more potent than gentamicin and seems to have very low toxicity. "This could have very far-reaching effects," claims David Bedwell, a microbiologist at the University of Alabama in Birmingham, who has tested the compound in his lab and is collaborating with the company.
In mice with muscular dystrophy the drug restores expression of the dystrophin protein found on the surface of muscle cells. Tests suggest the muscles regain some of their normal characteristics. Tests on mice with cystic fibrosis also suggest PTC124 restores production of functional CFTR.
All the results remain unpublished, though researchers working with the company say they hope to publish as soon as intellectual property issues are resolved. Miller says the company hopes to start clinical trials with healthy volunteers as early as next year.
But a premature stop mutation will not always be the cause of a particular genetic disease. So even if PTC124 or gentamicin make it to the market for treating genetic diseases, they will not be a magical cure for everyone.