A large-scale, multinational, phase 3 trial of the experimental drug ataluren has opened its first trial site, in Cincinnati, Ohio.
The trial is recruiting boys with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD) caused by anonsense mutation — also known as a premature stop codon — in the dystrophin gene. This type of mutation causes cells to stop synthesizing a protein before the process is complete, resulting in a short, nonfunctional protein. Nonsense mutations are believed to cause DMD or BMD in approximately 10 to 15 percent of boys with these disorders.
Ataluren — sometimes referred to as a stop codon read-through drug — has the potential to overcome the effects of a nonsense mutation and allow functional dystrophin — the muscle protein that’s missing in Duchenne MD and deficient in Becker MD — to be produced.
The orally delivered drug is being developed by PTC Therapeutics, a South Plainfield, N.J., biotechnology company, to whichMDA gave a $1.5 million grant in 2005.
Ataluren, formerly known as PTC124, is a novel small-molecular agent designed to makeribosomes become less sensitive to, or possibly ignore premature stop codons. This may be particularly beneficial in genetic disorders where the mRNA contains a mutation causing premature stop codon or nonsense codon. However, it is not equally effective with every stop codon, working best on the sequence ‘UGA’.
PTC124 has been tested on healthy humans and humans carrying genetic disorderscaused by nonsense mutations,such as some people with cystic fibrosis andDuchenne muscular dystrophy. Clinical trials are proceeding for several genetic disorders, in the subset of affected people who have nonsense mutations (typically <10% of those with the disorder). PTC Therapeutics released preliminary results of its phase 2b clinical trial for Duchenne muscular dystrophy, with participants not showing a significant improvement in the six minute walk distance after the 48 weeks of the trial.However, phase 2 clinical trials were successful for cystic fibrosis in Israel, France and Belgium.Multicountry phase 3 clinical trials are currently in progress for cystic fibrosis in Europe and the USA.
PTC124 has been developed by PTC Therapeutics.