Vertex Pharmaceuticals’ cystic fibrosis combination drug Symdeko (tezacaftor/ivacaftor) received expanded approval from the FDA to treat children aged six and older that have certain genetic mutations.

The drug received FDA approval last year for treating children aged 12 and older with the same specific genetic mutations.

A rare genetic disorder caused by a defective protein, cystic fibrosis causes thick mucus to produce in the lungs, digestive tract and other parts of the body, severely damaging them.

The expanded approval for children as young as six years old “provides an important treatment option for younger patients, and also provides more context on the safety and dosing specific to this population,” said Banu Karimi-Shah, acting deputy director of CDER’s Pulmonary, Allergy and Rheumatology Products division.