New Drug Improves Bone Growth in Children With Common Form of Dwarfism

Results of a phase three trial for a drug to help treat the most common form of dwarfism show it can boost bone growth in children—and sometimes cause them to grow as fast as their peers who don’t have dwarfism.

Results of the trial, which focuses on the drug therapy called vosoritide to treat achondroplasia, were published on September 5 in The Lancet. The trial was conducted on 121 children at 24 hospitals in seven countries— Australia, Germany, Japan, Spain, Turkey, the U.S., and the U.K.—with patients between the ages of 5 and 17 when they were enrolled.

Study participants received a daily injection of either vosoritide or a placebo for a year. Researchers discovered that children who received vosoritide grew an average of 1.57 centimeters more than those who received the placebo.

That’s a growth rate that’s almost in line with children who don’t have achondroplasia, study co-author Carlos A. Bacino, MD, a professor of molecular and human genetics at the Baylor College of Medicine and chief of genetics service at the Texas Children's Hospital, tells Verywell.

While the study results were positive, it’s unclear at this point whether the children who received treatment will be taller as adults or what the long-term effects of the therapy will be, Bacino says.

What Is Achondroplasia?

Achondroplasia is a bone growth disorder that prevents the changing of cartilage to bone, explains the National Institutes of Health (NIH). People with achondroplasia typically have dwarfism, which results in a limited range of motion at the elbows, a large head size, and small fingers.

The condition is caused by mutations in the FGFR3 gene. That gene typically slows the growth of bones in children’s limbs, spine, and the base of their skull, Bacino says. “But, with achondroplasia, signaling from the FGFR3 gene goes wrong,” he says. “It constantly signals to the body to restrain bone growth.”

How Vosaritide Works

Vosoritide blocks the activity of FGFR3 and attempts to give children with achondroplasia normal growth rates. “In a way, it stops or puts the brakes on FGFR3’s inhibitory process,” Bacino says. Children with achondroplasia typically grow around 4 centimeters a year, compared with 6 to 7 centimeters in children without the condition.

Previous trials have shown that the drug is safe to give to people with dwarfism, while this particular trial showed it can be effective at increasing bone growth. 

Children who use vosoritide are given daily injections “until the growth plates close, around puberty,” Bacino says. Once a child’s growth plates have closed, he says “you will not have any effect from the drug.”

Achondroplasia is currently treated with monitoring and, in some cases, surgery to address symptoms. But the disease itself isn’t treated.

The condition can cause health complications including:

• Apnea
• Obesity
• Recurrent ear infections
• An exaggerated inward curve of the lumbar spine
• Narrowing of the spinal canal that can pinch the upper part of the spinal cord
• Buildup of fluid in the brain

What Happens Next

Currently, there is no drug therapy approved by the Food and Drug Administration (FDA) to treat achondroplasia. There is currently a trial of vosoritide for children ages 5 and below, and the drug has been submitted to the FDA for approval, Bacino says.

The results of the latest trial on vosoritide are promising, but Bacino says that “it’s going to take a few years until we know how well this works over time." He points out that there is some controversy over the use of vosoritide, given that “some families that have achondroplasia may not necessarily consider it a problem.”

"For many families, achondroplasia is an issue,” Bacino says. He cites spinal issues, pain, and neurological issues that can develop as a result of the disease as a reason for treatment.

“We want to prevent some of these complications and allow people with achondroplasia to have a better quality of living,” he says.