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Federal regulators on Friday approved a Biogen Inc. drug as the first treatment for spinal muscular atrophy, a rare disease that causes loss of muscle control in children and is the leading genetic cause of death for infants.
The preholiday OK from the Food and Drug Administration lifted the spirits of the families of thousands of children across the United States suffering from the inherited neurological disorder, known as SMA, which often requires them to use a wheelchair at an early age and makes it hard for them to hold up their heads, breathe, and swallow.
There are an estimated 9,000 patients in the United States and up to 40,000 worldwide with SMA, which is believed to affect about one in 10,000 children born around the world.
“This is miraculous,” said Courtney Davidopoulos of Westford, whose 7-year-old son, Matthew, began taking Biogen’s drug this month under an early access program at Boston Children’s Hospital.
“It’s what the families of kids living with this disease have been waiting for,’’ Davidopoulos said. “Now when kids are diagnosed, they’ll be told, ‘You have SMA, but you can come in for a treatment.’ It’s a totally different future for these kids.”
Davidopoulos called the news “the best Christmas present imaginable.”
The approval also boosted morale at Cambridge-based Biogen, the largest Massachusetts-based biotech company, which named a new chief executive earlier this week amid gnawing questions about the strength of the company’s drug development pipeline.
Biogen chief executive George A. Scangos said in a statement that the drug, which will be sold under the brand name Spinraza, “exemplifies our mission to make a meaningful difference in the lives of patients.” The FDA’s approval covers both children and adults with the disease in the United States.
“There has been a longstanding need for a treatment for spinal muscular atrophy, the most common genetic cause of death in infants, and a disease that can affect people at any stage of life,” said Dr. Billy Dunn, director of the neurology products division at the FDA’s Center for Drug Evaluation and Research.
Dunn said the FDA had asked Biogen to let regulators review data from its clinical trial as soon as possible through an interim analysis not typically conducted by the FDA. Data from 82 of the 121 infant-onset patients being studied in the trial were eligible for the interim analysis. Forty percent of them achieved improvement in motor milestones.
Biogen’s injectable drug was given fast-track designation and priority review by the FDA because it addressed an unmet medical need.
It was approved three months after Biogen completed a “rolling application” process, submitting clinical data and other information in FDA regulators in stages, an unusually fast review period for the agency. Biogen is preparing to launch it early next year.
“This is exactly what we do at Biogen — cutting-edge research and breakthrough therapies,” said Alfred Sandrock, the company’s chief medical officer. “We feel a high sense of urgency to introduce it as soon as [it is] feasible to make sure patients get access to this drug.”
Biogen won’t disclose how much it will charge for Spinraza until next week at the earliest, but it is expected to be a premium price for a fatal disease with no other treatments. Analysts have estimated that its peak annual sales could top $1 billion within the next few years.
The FDA’s decision was released after the close of regular trading. Biogen’s stock rose 2.2 percent to $293.53 in after-hours trading.
Spinraza will be administered to eligible patients at clinical trial sites as well as other hospitals and the offices of pediatric neurologists across the nation. The drug will be injected into the spinal fluid in the lower backs of patients.
Biogen, the leading maker of multiple sclerosis medicines, agreed in 2012 to collaborate on Spinraza with Ionis Pharmaceuticals Inc. of Carlsbad, Calif., which developed the drug in its labs.
Last August, Biogen paid $75 million to Ionis to exercise an option to complete development and commercialize the drug. Under that deal, Ionis is eligible to receive up to $225 million more, plus sales royalties, if the drug met certain regulatory and commercial targets.
In clinical trials, Biogen and Ionis tested the experimental drug on patients ranging from presymptomatic infants to adults living with the disease, finding that babies and children with SMA showed statistically significant improvement in motor function.
The most common side effects found in patients in the clinical trials were upper respiratory infection, lower respiratory infection, and constipation, the FDA said.
Davidopoulos said it was too soon to assess the effects of Spinraza on her son Matthew, but she is hopeful. “We see this as a start,” she said. “We need more therapies. Even if it only stops progression of the disease, my kid could get to another therapy.”
Michel Vounatsos, who was named Biogen’s incoming chief executive earlier this week, cited the successful launch of Spinraza as a top near-term goal. Long term, Vounatsos said, Biogen must broaden its drug portfolio and work to bring its drug candidate for Alzheimer’s disease to market.
Robert Weisman can be reached at email@example.com. Follow him on Twitter @GlobeRobW.