Dr Scott GottliebScott Gottlieb, MD
The FDA has approved the first generic version of vigabatrin for the treatment of complex partial, or focal, seizures as adjunctive therapy in patients with refractory epilepsy who are 10 years of age and older.1

Originally branded as Sabril and manufactured by Lundbeck, vigabatrin was originally approved in August 2009 as monotherapy for infantile spasms. This generic formulation approval was granted by the agency to Teva Pharmaceuticals.

"Prioritizing the approval of generic drugs to compete with medicines that face little or no competition is a key part of our efforts to support access and reduce drug costs to patients. The availability of high-quality generic alternatives of critically important medicines, once the period of patent protection or exclusivity has ended on the brand drug, helps advance access and saves consumers billions of dollars each year,” said FDA Commissioner Scott Gottlieb, MD, in a statement.

In the 2 trials submitted along with its original approval, the treatment was assessed in 357 adults with focal seizures, with or without secondary generalization.2 In Study 1 (n = 174), the treatment showed a mean reduction of 4.8 monthly seizures at 3 g/day and 4.0 monthly seizures at 6 g/day (P <.05 for both), compared to a 0.2 decrease with placebo. In Study 2 (n = 182) the 3 g/day dose resulted in 2.0 fewer seizures per month compared to placebo (P <.05), with the treatment arm experiencing 5.5 monthly seizures by end of study compared to 8.3 at baseline and the placebo arm experiencing 7.5 monthly seizures at the end of the study compared to 9.0 at baseline.

“We know there has been past interest in developing a generic alternative to this product,” Gottlieb said. “Earlier this year, we also highlighted this drug, along with many others, on a list of off-patent, off-exclusivity branded drugs without approved generics, to clarify that there were no patents or exclusivities that should impede its approval.”

The most common adverse events (AEs) associated with vigabatrin tablets, according to the agency, include dizziness, fatigue, somnolence, nystagmus, tremor, blurred vision, memory impairment, weight gain, arthralgia, upper respiratory tract infection, aggression, diplopia, abnormal coordination, and a confused state. Serious AEs associated with vigabatrin tablets include permanent vision loss and risk of suicidal thoughts or actions.

As a result of those serious AEs, the treatment’s original approval was accompanied by a risk evaluation and mitigation strategy (REMS) to ensure that the benefits outweighed the risks of vision loss and of suicidal thoughts and behaviors which were associated with the therapy. According to the FDA, it can cause permanent bilateral concentric visual field constriction, which includes tunnel vision that can result in disability and can, in some cases, damage the central retina and decrease visual acuity. 

“Today’s action demonstrates that there is an open pathway to approving products like this one,” Gottlieb said. “We’re especially focused on new policies aimed at making the generic review process more predictable, efficient and lower cost so we can entice more generic firms to enter this space and help facilitate more generic drug launches after generic approvals.”

The FDA commissioner added that the agency is aware that approving a record number of generics is “not enough” and that the regulator is aiming to see “firms launch these products so that patients can benefit from their availability, and we intend to take steps to advance these goals."
REFERENCES
1. FDA approves first generic version of Sabril to help treat seizures in adults and pediatric patients with epilepsy [press release]. Silver Spring, MD: FDA; Published January 16, 2019. fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm629569.htm. Accessed January 16, 2019.
2. Sabril Prescribing Information. FDA Label. Updated October 2013. accessdata.fda.gov/drugsatfda_docs/label/2013/020427s010s011s012,022006s011s012s013lbl.pdf. Accessed January 16, 2019.