US FDA approves higher dose of Biogen's genetic disorder drug

March 30 (Reuters) - The U.S. Food and Drug Administration has approved a higher-dose version of Biogen's BIIB.O drug for a rare genetic disorder that causes progressive muscle weakness, the company said on Monday, offering patients a potentially more effective option.

The regulator had declined to approve the company's application last year, seeking updated technical information.

The therapy, Spinraza, is approved in the U.S. for spinal muscular atrophy, a group of inherited diseases which affect nerve cells in the brain and spinal cord that control movement, as well as muscles used for speaking, walking, swallowing, and breathing.

Biogen's application was supported by mid-to-late-stage trial data showing the higher-dose version significantly improved motor function in infants compared to untreated patients, while maintaining a safety profile similar to the low dose regimen.

SMA patients in the U.S. also have access to Roche's ROPC.S oral drug Evrysdi, and Novartis' NOVN.S gene therapies Zolgensma for patients under two years of age and Itvisma for those aged two and older.

Biogen's Spinraza generated global sales of $1.55 billion in 2025, compared with $1.57 billion a year earlier.

The drug is administered via injection into the spinal fluid to boost protein levels essential for motor neuron survival and slowing progression of the disease..

The new regimen, which will be available in the U.S. in the coming weeks, uses two 50 milligram initial doses given 14 days apart, followed by a 28 mg maintenance dose every four months, compared to the current standard dose of 12 mg, Biogen said.