More than two weeks ahead of its expected PDUFA date, PTC Therapeutics Inc.’s spinal muscular atrophy (SM) drug, risdiplam, gained FDA approval, making it the first at-home, oral treatment intended for use in adults and children 2 months and older.
Branded Evrysdi, the drug will be marketed by partner Genentech, a member of the Roche Group, and is expected to be available in the U.S. within two weeks for direct delivery to patients’ homes through Accredo Health Group Inc., according to PTC. Pricing information was not immediately available.
A small-molecule survival motor neuron 2 (SMN2)-directed RNA splicing modifier, Evrysdi was co-developed by PTC and Roche, along with the SMA Foundation. It is designed to treat SMA caused by mutations in chromosome 5q that lead to SMN protein deficiency. By acting as a splicing modifier of SMN2, it aims to increase production of full-length protein to compensate to SMA-causing mutations in SMN1.
Approval was based on data from the pivotal Firefish and Sunfish trials, showing clinically meaningful improvements in motor function and hitting development milestones in patients across all levels of disease severity, including types 1, 2 and 3 SMA. Firefish, which enrolled symptomatic infants, ages 2 months to 7 months with type 1 SMA, showed 41% (7/17) of those treated with the therapeutic dose achieved the ability to sit without support for at least five seconds as measured by the Bayley Scales of Infant and Toddler Development Third Edition (BSID-III) gross motor scale. That compares to historical data showing untreated infants with infantile-onset SMA cannot sit independently. Nineteen of 21 infants (90%) were alive without permanent ventilation and reached 15 months of age or older, while 81% (17/21) of all patients were alive without permanent ventilation after a minimum of 23 months of treatment and reached an age of 28 months or older.
Sunfish, which enrolled children and adults with types 2 and 3 SMA, showed improvement in motor function, as measured by a change in baseline in the Motor Function Measure 32 (MFM-32) total score (p=0.0156) at 12 months vs. placebo. MFM-32 is designed to assess 32 different motor functions across a wide range of people with the progressive neuromuscular disease. In addition, Sunfish data showed improved upper limb motor function vs. baseline, as measured by the Revised Upper Limb Module, a secondary independent motor function endpoint of the study (p=0.0028).
Evrysdi will go up against two drugs that have already staked out significant claims in the SMA space, mostly notably Biogen Inc.’s antisense oligonucleotide, Spinraza (nusinersen). Designed with a mechanism similar to Evrysdi, Spinraza rapidly gained market uptake following its late 2016 approval and pulled in full-year 2019 revenues of nearly $2.1 billion. Gaining ground is Novartis AG’s gene therapy, Zolgensma (onasemnogene abeparvovec), a potential one-time, curative treatment that gained FDA approval in May 2019.
In addition to clinical data testing the drug in a wide range of SMA patients, PTC and Genentech are banking on Evrysdi’s administration to give it an advantage over Spinraza, which must be injected into the spine. Evrysdi can be administered daily at home in liquid form by mouth or feeding tube, offering a far more convenient option.
A marketing submission for Evrysdi is pending at the EMA, which previously granted the drug Priority Medicines designation and orphan designation. Applications also are pending in Brazil, Chile, China, Indonesia, Russia, South Korea and Taiwan.
Evrysdi’s application to the FDA received orphan drug, fast track and priority review designations. It also was awarded a rare pediatric disease priority review voucher.
Shares of PTC (NASDAQ:PTCT) closed Aug. 7 at $47.83, up 81 cents, following news of the approval.