In a first, drug offers hope for children with dwarfism An experimental drug, vying to become the first approved treatment for dwarfism, improved growth in children by a significant amount in a preliminary study, the drug's developer, BioMarin Pharmaceutical, said on Wednesday.

In the study, the 10 children who got the highest dose of the drug grew at an average rate of 6.1cm, or 2.4 inches, per year, about a 50% increase from the four centimetres per year they were growing before starting the drug. The growth rate while on the drug was similar to that of a child without the condition, the company said. Wall Street investors and analysts had been hoping for a 50% improvement in growth rate, and BioMarin shares rose 6% in after-hours trading.

Dr William R Wilcox, a human genetics professor at Emory University, called the results "promising." But he expressed caution, given that only 10 children were getting the high dose and were treated for only six months. "Six-month results are important, but they don't really give you the whole story," said Dr Wilcox, who has been a consultant to BioMarin.

He said that human growth hormone, a drug already marketed for certain children, can also increase the growth rate for people with dwarfism to 6 centimetres per year ” but the effect wears off after one year. So, he said, it would be important to see if the BioMarin drug can increase growth year after year.

The drug, which is called BMN 111 or vosoritide, is aimed at treating achondroplasia, the most common form of dwarfism. The company says there may be 24,000 children with the condition in the markets in North America, Europe, Asia and Latin America in which it anticipates selling the drug. The drug would not be expected to work in adults because they have stopped growing.

Women with achondroplasia typically grow to about four feet tall, and men a few inches taller.

The condition also causes disproportionate growth that can lead to complications like bowed legs, sleep apnea and spinal cord compression, which can require surgery to correct. It is too soon to say if vosoritide can prevent any of those complications.

The drug is not universally welcomed. Some people with dwarfism say it is not a disease that needs treatment. But about 80% of children with achondroplasia are born to parents of normal stature, and many parents want treatments for their children. One is a torturous surgery that lengthens the legs by breaking them.