On December 23, 2016, the U.S. Food and Drug Administration approved SPINRAZA™ (nusinersen), an antisense oligonucleotide directed to survival motor neuron-2 (SMN2) transcripts for the treatment of spinal muscular atrophy (SMA) in pediatric and adult patients.

SMA is a heredity disease that affects the nervous system and results in progressive, debilitating muscle atrophy and weakness. It is caused by deleterious mutations in the survival motor neuron-1 (SMN1) gene that lead to insufficient levels of survival motor neuron (SMN) protein. According to an Ionis Pharmaceuticals' press release, this first approved treatment for SMA “was discovered and developed by Ionis and Biogen, and licensed to Biogen who is responsible for future development, manufacturing, and commercialization.”

SPINRAZA™ is an antisense oligonucleotide that selectively binds to, and alters, the splicing of a single RNA from the SMN2 gene, a gene that is nearly identical to SMN1, in order to increase production of full length SMN protein. According to SPINRAZA™’s Prescribing Information, the synthetic oligonucleotide is administered by intrathecal (spinal) injection.

SPINRAZA™ was designated an Orphan Drug and its approval follows the FDA’s granting of fast track designation and priority review to the New Drug Application (NDA). Noting the urgent need for SMA therapeutics, an FDA director stated that “as shown by our suggestion to the sponsor to analyze the results of the study earlier than planned, the FDA is committed to assisting with the development and approval of safe and effective drugs for rare diseases and we worked hard to review this application quickly.”