A new drug to treat a rare genetic disorder that causes rapid aging in children has been approved after clinical studies showed promising results in extending their lives.

Zokinvy, the first drug of its kind to treat the genetic mutation known as progeria that also stunts growth, was approved by the US Food and Drug Administration this week. In clinical tests, the drug was found to increase patients’ lives by more than two years.

There are an estimated 400 people around the world and 20 in the US who suffer from the condition which causes hair loss and aged-looking skin. Children afflicted with the disease suffer strokes and hardening of arteries and typically die at 14.

The disorder is not inherited but due to a chance gene mutation that causes a damaging buildup in cells of a protein called progeria,
Research on the treatment was mainly funded by the Progeria Research Foundation in Peabody, Mass., with help from drug developer Eiger BioPharmaceuticals.