At long last the spinal muscular atrophy community has a treatment and hope.

On Dec. 23, the FDA gave the final go-ahead for Spinraza (nusinersen), a disease-modifying antisense drug developed by Ionis Pharmaceuticals and licensed by Biogen.

Underscoring the extreme unmet need, the FDA granted the drug fast-track designation, priority review and orphan drug designation, a trifecta of incentives that streamline the approval of drugs for rare and unmet diseases.

Spinraza is the product of Ionis Pharmaceutical’s novel antisense pipeline. The drug is designed to increase the production of SMN1 by modulating a closely related gene, SMN2, which helps to offset the underlying genetic defect.

SMA varies greatly in regards to severity, age of onset and rate of decline. Individuals with the disease experience weakness and wasting of their voluntary muscles, but it does not directly affect cognitive ability or intelligence.

In July 2016, Biogen dropped $75 million to exercise its exclusive option to license Spinraza. The deal also made Ionis eligible for up to $150 million in milestone payments and tiered royalties — rights it will now be cashing in.

Spinraza was approved following a pivotal trial of the therapy in 121 patients with infantile-onset SMA. All were diagnosed before 6 months of age and started the drug before they were 7 months old. Two-thirds of patients received an active dose of the drug, the rest were given a mock spinal injection to mimic the delivery procedure.

In its approval news release, the FDA noted that it worked closely with the company on the Phase 3 trial design and then called for an interim analysis to quickly gauge treatment efficacy. Some 82 of the 121 patients were eligible for the early review.

At that stage in the study, 40 percent of those treated Spinraza had achieved the pre-defined improvements in motor control. None of the control patients did. The trial was subsequently stopped and all patients were invited to transition to an open-label study of the drug.

Chief medical and scientific officer of the Muscular Dystrophy Association (MDA), Valerie Cwik, said the drug was a turning point in the fight against the disease.

“Spinraza truly is the life-changing therapy our SMA community has been waiting for, and we’re eager to see our families benefit from it. Not only has it appeared in trials to slow the progression of SMA, but some patients actually improved. It’s a significant achievement, with babies who would have been expected to die before turning a year old instead sitting up, rolling over and even walking.”

Around one in 40 Americans is a carrier of a mutation in the survival of motor neuron 1 (SMN1) gene. If both parents are carriers their child has a one in 4 chance of developing spinal muscular atrophy (SMA).

Photo: bandit2523, Getty Images