The United States Food and Drug Administration (FDA) has approved GlaxoSmithKline's (GSK) (LSE: GSK)(NYSE: GSK) Nucala (mepolizumab) intended for adults and children aged 12 years and older with hypereosinophilic syndrome (HES) for six months or longer without another identifiable non-blood related cause of the disease, it was reported on Friday.

This is the first new treatment to be approved for HES patients in around 14 years. The product was assessed in a randomised double-blind, multicentre, placebo-controlled trial in 108 patients with HES. The side effects of the product in HES patients include upper respiratory tract infection and pain in extremities (such as the hands, legs and feet).

The US FDA approval is being granted to GlaxoSmithKline of Research Triangle Park, North Carolina.