The FDA has approved Zogenix Inc.’s Fintepla (fenfluramine), an oral treatment for patients age 2 and older with seizures associated with Dravet syndrome, a rare, pediatric-onset form of epilepsy.

The company’s stock (NASDAQ: ZGNX) was up 15.93% in premarket trading June 26. Fintepla was approved late in the day on its PDUFA date, June 25.

Dravet syndrome, which afflicts children, is life threatening, chronic and the seizures associated with it are severe. It also comes with an increased risk of sudden unexpected death.

Fintepla, whose journey began six years ago in Belgium, will launch by the end of July through the Fintepla Risk Evaluation and Mitigation Strategy (REMS) Program, where patients will be monitored while being treated.

The price will vary from patient to patient, Ashish Sagrolikar, Zogenix’s executive vice president and chief commercial officer, said in Friday morning’s conference call, with an average list price based on dosing and patient weight expected to be $96,000 per year. The of Emeryville, Calif.-based company will have a patient assistance program offering support based on patient needs, he added.

There are anywhere from 6,000 to 8,000 Dravet syndrome patients in the U.S.

SVB Leerink analyst Marc Goodman on March 3 estimated Fintepla’s U.S. sales in Dravet syndrome to about $22 million in 2020 and about $83 million in 2021.

Fintepla’s approval was based on two randomized, double blinded, placebo-controlled phase III studies, along with safety data from an open-label extension trial that lasted up to three years for some of the studies’ 341 patients. Patients age 2 to 18 receiving the treatment had significantly fewer convulsive seizures than those receiving placebo. The seizures were held at bay within the first three to four weeks and stayed that way for the 14 to 15-week treatments.

Its path to approval wasn’t smooth. In April 2019, the FDA sent Zogenix a refusal-to-file letter, complaining the firm failed to include non-clinical data related to Fintepla’s chronic use and that the NDA contained the wrong version of the clinical dataset on the package, which meant the regulators couldn’t complete the review until they had more information.

With Fintepla, gatekeepers said they wanted sensitivity analyses on phase III results.

“The data are incredibly robust to any sensitivity analysis we have conducted, to the point where we're not seeing any shift in ‘p’ values and very, very small differences in endpoint estimates,” CEO Stephen Farr told investors on the March 2 earnings call. “We don't think there's really anything that the FDA is going to uncover here that we have not already seen.”

Fintepla is the small molecule formerly known as ZX-008. Fenfluramine is a serotonin reuptake blocker.

As half of the weight-loss drug known as fen-phen, fenfluramine’s past is checkered. It was withdrawn from the market in 1997 after cases of heart valve defects and pulmonary hypertension were reported in people who had taken the compound with phentermine.