Dive Brief:
- Shares in Stoke Therapeutics nearly doubled in value Tuesday morning, after the biotechnology company disclosed updated trial data Monday evening for an experimental drug it’s developing for a form of genetic epilepsy.
- Results showed treatment with a high dose of the drug substantially reduced the frequency of convulsive seizures in people with Dravet syndrome, compared to a placebo. Monday’s disclosure included data from more study participants at three and six months after their last dose than an earlier update last July.
- Stoke plans to discuss with regulators a larger study to follow the trials it’s currently running. That later-stage study would likely test three high doses of its drug, followed by continued treatment at a middle dose, Stoke said.
Dive Insight:
The market reception to Stoke’s new data is more positive than in July, when shares fell after the company released results analysts viewed as mixed and disclosed a serious adverse reaction trial investigators linked to treatment.
The new cut of data, while from the same two Phase 1/2a trials, focused on the 70 milligram drug dose Stoke aims to take forward into later-stage testing. The company shared longer follow-up results for 11 study participants who had received either two or three 70 milligram doses and, for the first time, data from eight participants who received one dose.
Seizure frequency dropped by a median of 43% three months after those eight participants’ only dose, and by 85% three months after the last dose given to 10 of the 11 other study volunteers. Data for one participant was excluded due to a change in background medication, Stoke said.
At six months, the decline in seizure frequency was 57% and 74% among seven and nine participants in each group, respectively.
Stoke did not report changes in seizure frequency from about one month through three and six months after a patient’s last dose, as it did in July.
Across the two trials as well as open-label studies, Stoke has treated 81 people with various doses of its drug. Thirty percent, or 24, have experienced a drug-related side effect, most commonly vomiting and elevations in a biomarker known as cerebrospinal fluid protein.
Eighteen people have had a serious adverse event, but only in the case Stoke disclosed in July was the adverse event linked to treatment.
“The stock has been under pressure during the past 2 years due to the mixed interim results, so the high consistency observed in the final dataset should be appreciated by investors,” wrote Rudy Li, a Leerink Partners analyst, in a note to clients.
People with Dravet experience frequent and prolonged seizures, often starting very early in life. While there are drugs available to treat or prevent those seizures, the condition can also cause intellectual disability and development delays.
Stoke’s drug, a so-called antisense oligonucleotide, is designed to promote expression of a protein called NaV1.1 to reduce seizures and address the disease’s other health effects. The NaV1.1 protein helps transport sodium ions into cells, which plays an important role in nerve cell signaling.
Ed Kaye, Stoke’s CEO, has previously compared the company’s drug to Spinraza, another antisense oligonucleotide that treats the disease spinal muscular atrophy by promoting a key muscle protein.
“The totality of these data provide compelling evidence that support the potential for STK-001 to be a disease-modifying medicine for patients with Dravet syndrome by treating the underlying cause of the disease, rather than just the symptoms,” said Kaye, referring to the company’s drug by its code name in a Monday statement.
After rising by as much as 100% early on Tuesday, Stoke shares were trading up 75% by mid-morning.