A drug that helps regulate bone development has been found to boost growth rates in children with achondroplasia, the most common type of dwarfism, in a global trial.The patients' average boost in height to about 6 cm (2.4 inches) per year was close to growth rates among children of average stature, and the side effects of the drug were mostly mild, said study co-author Julie Hoover, Associate Professor at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University. "Right now, the results of the study show an impact on growth, and this effect is sustained, at least over nearly four years in this trial," Hoover said. Results of the phase-2 trial published in the New England Journal of Medicine showed that the drug, vosoritide, was generally well tolerated by patients.On average, participants in the trial grew at a 50 per cent faster compared to baseline with no adverse effects on body proportion, the results showed.Achondroplasia is caused by over-activity of a signal that stops growth, and could be likened to overwatering a plant, said lead author Ravi Savarirayan, Professor at Melbourne's Murdoch Children's Research Institute in Australia.
"This drug basically kinks the hose so that the plant gets the right amount of water and can resume regular growth," Savarirayan said. Achondroplasia is a genetic bone disorder affecting about one in every 25,000 infants. It is caused by a mutation in the FGFR3 gene that impairs the growth of bones in the limbs, the spine, and base of the skull.The most common health complications experienced by children with achondroplasia are spinal cord compression, spinal curvature and bowed legs. About half of these children will need spinal or other surgery.Unlike other treatments - such as growth hormone and limb-lengthening surgery - that focus on symptoms, vosoritide focuses on the underlying cause of achondroplasia and directly counteracts the effect of the mutation that slows growth.The study ran over four years across research centres in Australia, France, Britain and the US with 35 children assigned to one of four groups receiving daily subcutaneous doses of the drug in increasing amounts.The results showed vosoritide demonstrated dose-dependent increases in centimetres grown per year during the first six months, with improvements maintained over the study extension period of a further three years.