Diacomit extends seizure-free time, new STICLO data confirm

New trial data also show treatment reduces seizure frequency

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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Treatment with add-on Diacomit (stiripentol) rapidly reduced seizure frequency and extended seizure-free periods in children with Dravet syndrome, according to additional data from the treatment’s STICLO clinical trials.

Open-label extension study data, which had not been previously reported, showed that placebo-treated patients who switched to Diacomit experienced a rapid decrease in seizure frequency. Moreover, some patients who didn’t respond to Diacomit during the first two months eventually responded in the one-month extension study.

Data from caregiver diaries aligned with STICLO data, showing an increase in the number and period of seizure-free days in Diacomit-treated patients.

“This marked efficacy together with an acceptable tolerability likely translates into improvements in patients and caregivers’ quality of life,” the researchers wrote.

The newly reported STICLO results were published in the journal Neurology and Therapy, in the study, “Additional Results from Two Randomized, Placebo-Controlled Trials of Stiripentol in Dravet Syndrome Highlight a Rapid Antiseizure Efficacy with Longer Seizure-Free Periods.” The study was funded by Biocodex, the manufacturer of Diacomit.

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A recent seizure has me worried about my daughter with Dravet

Studies involve total of 64 children

Diacomit is an add-on antiseizure medication recommended in combination with Onfi (clobazam) and Depacon (sodium valproate) for Dravet patients. It was approved in Europe in 2007 and in the U.S. in 2018, where approval was extended to children as young as 6 months who weigh at least 7 kg (about 15 lbs) in 2022.

Two independent Phase 3, placebo-controlled clinical trials — STICLO-France and STICLO-Italy — supported its approval.

Collectively, the studies included 64 Dravet children, ages 3 and older, who were experiencing at least four generalized clonic or tonic-clonic seizure episodes per month despite Onfi and Depacon. Participants were randomly assigned to receive Diacomit or a placebo, in combination with Onfi and Depacon, for two months.

According to pooled trial data, significantly more Diacomit-treated patients saw their seizure frequency drop by at least 50% than those given the placebo (69.7% vs. 6.5%). In addition, about one-third of patients (36.4%) in the Diacomit group were seizure-free throughout the two-month study period compared with none in the placebo group.

However, not all STICLO results were published, particularly data from an open-label extension (OLE) period, some STICLO-Italy efficacy data, and reports by caregivers.

To fill in these gaps, researchers in France and Italy, alongside scientists from Biocodex, which funded this study, reported more trial outcomes, including those of the 44 patients in the OLE.

Including new data confirmed the early findings after two months, with significantly more Diacomit-treated patients experiencing at least 50% fewer seizures than placebo patients (72% vs. 7%). Moreover, Diacomit outperformed placebo in the number of patients whose seizures dropped by 75% (56% vs. 3%).

Diacomit’s efficacy was maintained during the extra third month of the OLE, with a similar reduction in seizure frequency compared with the first two months.

The original placebo-treated patients who switched to Diacomit in the OLE saw their seizure frequency rapidly drop by 80.2%. By the end of the OLE, there were no differences in response rates between those who had continued Diacomit into the OLE and those who switched.

Individually, all patients who switched from placebo to Diacomit during the OLE had a decrease in seizure frequency. Only three patients who continued Diacomit had a higher seizure frequency compared with before treatment.

Notably, five Diacomit-treated patients who did not respond during the first two months responded during the third OLE month. Two of them saw a drop in seizure frequency by at least 50%, one by at least 75%, and two were seizure-free.

Based on caregiver diaries collected from 52 patients (81%), the median number of seizure-free days over two months was higher in the Diacomit group than in the placebo group (55.8 vs. 40.9 days). The median period of consecutive seizure-free days was also longer with Diacomit (32 days vs. 8.5 days).

Regarding safety, all patients in the Diacomit group experienced adverse events, compared with about half in the placebo group (100% vs. 45%). The most common Diacomit-related adverse events were sleepiness, weight loss, and the eating disorder anorexia.

“Overall, the pooled STICLO trials data demonstrate a rapid antiseizure efficacy of [Diacomit] in patients with Dravet syndrome, with highly significant responder rates,” the researchers wrote. “this marked efficacy together with the increase in seizure-free periods likely translates into improvements in patients’ and caregivers’ quality of life.”