An experimental drug called vosoritide, which interferes with specific proteins that block growth, allowed the average annual growth rate to increase in a study of 35 children and teenagers with achondroplasia, a form of dwarfism, according to researchers at Johns Hopkins Medicine, the Murdoch Children's Research Institute in Australia, and seven other medical institutions. According to the researchers, the patients' average boost in height to about 6 centimeters (2.4 inches) per year is close to growth rates among children of average stature, and the side effects of the drug were mostly mild. The team summarized their four-year study in the New England Journal of Medicine.
The associate professor and director of the Greenberg Center for Skeletal Dysplasias at the Johns Hopkins McKusick-Nathans Institute of Genetic Medicine, Julie Hoover-Fong, M.D., Ph.D., said that an increase in the annual growth rate alone might have a positive effect on some patients' quality of life. For other patients, now and in the future, they hope that the altered bone growth throughout the body could ease such problems as sleep apnea, neurological, and leg and back problems, and improve their quality of life. The result of the study, at present, show an impact on growth, and this effect is sustained, at least over nearly four years in this trial. As for the potential long-term, it will take more time to observe.
All over the world, achondroplasia, though rare, is the most common form of dwarfism, affecting an estimated 1 in 15,000 - 40,000 live births. The condition is caused by mutations in a gene called FGFR3 that result in the excess production of proteins that slow bone growth. The disorder is marked by disproportionate short stature with shortened limbs, near normal-sized torsos, and enlarged heads.
Between January 2014 and July 2018, the researchers conducted the current study by enrolling 35 children ages 5 - 14 and followed them for a midpoint of 42 months. There were 19 girls and 16 boys, including two Hispanics, seven Asians, and two African Americans.
For the enrolment, the participants had previously been monitored for six months to determine their baseline growth rate. Then, for six months, participants received a daily vosoritide injection through the skin at doses ranging from 2.5 - 30 micrograms/kilogram. Over the four-year study, two participants discontinued the trial because of anxiety with daily injections. One left the test because their growth plated closed, and another removed for unknown reasons. A fifth was withdrawn when doctors found during routine electrocardiography that a participant has Wolff-Parkinson-White syndrome, a condition in the electrical circuits of heart muscles that causes rapid heartbeat.
Ultimately, the team discovered that, on average, the children's annual growth rate increased from below 4 centimeters per year to below 6 centimeters per year. Hoover-Fong noted that they grew nearly 2 centimeters more, on average, per year, and this rate comes close to the annual growth of ordinary stature people.
