Novartis AG is seeking U.S. and EU approval for its drug siponimod to treat an aggressive type of multiple sclerosis, an autoimmune disorder.

The Swiss drugmaker said the U.S. Food and Drug Administration and the European Medicines Agency have accepted the company's drug application for the therapy, which is intended for patients with secondary progressive multiple sclerosis.

MS is characterized by nerve damage in the brain and the spine, leading to loss of physical and cognitive function. The secondary progressive type of the disease is characterized by gradual and irreversible worsening of disability in patients.

The applications are based on data from a phase 3 study of the therapy, called Expand, which showed that siponimod cut the risk of disability progression at three months by 21% in patients with secondary progressive multiple sclerosis compared to placebo.

Siponimod also significantly reduced the annualized rate of relapses in patients with relapsing remitting MS — the most common type of the disease — over six months compared to placebo in a phase 2 study called Bold.

The U.S. and EU drug regulators are expected to decide on siponimod's approval by March 2019 and late 2019, respectively. Novartis said it used a review voucher to speed up the review of siponimod in the U.S.

MS affects about 2.3 million people worldwide.