(Reuters) -The U.S. Food and Drug Administration has declined to approve a higher-dose version of Biogen's drug for a rare genetic disorder that causes progressive muscle weakness, citing the need for updated technical information in the application, the company said on Tuesday.
Biogen said the FDA requested revisions to the Chemistry Manufacturing and Controls module in its so-called "complete response letter" but did not identify deficiencies in the clinical data supporting the high-dose regimen.
The company plans to resubmit the application promptly based on readily available information.
Spinraza, first approved in 2016 to treat spinal muscular atrophy, generated $1.57 billion in global sales in 2024, making it Biogen's second-highest-selling product.
"While this outcome was unexpected, we remain committed to bringing the high dose regimen to people living with SMA," said Priya Singhal, Head of Development at Biogen.
SMA, a rare genetic disorder caused by mutations in the SMN1 gene, leads to progressive muscle wasting and motor neuron degeneration.
Biogen faces mounting competition from Novartis' gene therapy Zolgensma and Roche's oral drug Evrysdi, both of which have gained traction due to ease of administration and broader accessibility.
The high-dose regimen, already approved in Japan and under review by the European Medicines Agency and other regulators, includes two 50 mg loading doses administered 14 days apart, followed by 28 mg maintenance doses every four months, compared to the current standard dose of 12 mg.
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.
The drug is administered via injection into the spinal fluid to boost protein levels essential for motor neuron survival.
Biogen licensed the global rights to develop, manufacture and commercialize Spinraza from Ionis Pharmaceuticals.
The company did not immediately respond to a Reuters request for comment.
(Reporting by Kamal Choudhury, Mariam Sunny and Siddhi Mahatole in Bengaluru; Editing by Krishna Chandra Eluri)
