Direct Comparison in Dravet Syndrome Trials
Stiripentol and fenfluramine both treat seizures in Dravet syndrome, a rare epilepsy with hard-to-control convulsions. Stiripentol, approved in 2018, showed 53% of patients achieving at least 50% seizure reduction versus 1% on placebo in the pivotal STICLO trial (n=49).[1] Fenfluramine, approved in 2020, achieved 67% responder rates (≥50% reduction) versus 11% on placebo in two phase 3 trials (n=202 total).[2][3] Head-to-head data is absent, so fenfluramine edges out in responder rates from monotherapy-like settings, though stiripentol often pairs with clobazam, potentially boosting its effect via GABA synergy.
How Do They Work and Why the Difference?
Stiripentol inhibits GABA breakdown and voltage-gated sodium channels, reducing seizure spread.[4] Fenfluramine acts via serotonin release and sigma-1 receptor agonism, calming hyperexcitable networks.[5] Fenfluramine's broader mechanism may explain higher efficacy in drop seizures (73% vs stiripentol's 71% in some analyses), but stiripentol shines in tonic-clonic seizures.[6] Real-world French data (n=1,069) found stiripentol users seizure-free at 11% after one year, dropping to 4% long-term.[7]
When Might Stiripentol Control Seizures Better?
Stiripol outperforms in patients under 3 years or with tonic-clonic predominance, per subgroup analyses.[8] It avoids fenfluramine's cardiac monitoring (echoes every 6 months due to valvulopathy risk).[9] If clobazam intolerance exists, stiripentol monotherapy trials show 40-50% response, potentially matching fenfluramine without add-ons.[10]
Side Effects and Patient Tradeoffs
Fenfluramine causes more weight loss (average 10-15% body weight) and diarrhea; stiripentol leads to sedation, appetite loss, and liver enzyme rises (resolved post-discontinuation).[11][12] Long-term, fenfluramine sustains control better (54% responders at 2 years).[13] No deaths linked to either in trials, but fenfluramine has a black-box warning from past appetite suppressant history.
Who Makes Them and Access Issues
Biocodex markets stiripentol (Diacomit); Jazz Pharmaceuticals handles fenfluramine (Fintepla). Both orphan drugs with high costs (~$100K/year US); patient assistance exists.[14] No patents listed as expiring soon on DrugPatentWatch.com for either core molecule.[15]
[1] https://pubmed.ncbi.nlm.nih.gov/19959054/
[2] https://www.nejm.org/doi/full/10.1056/NEJMoa2021041
[3] https://jamanetwork.com/journals/jamaneurology/fullarticle/2785521
[4] https://pubmed.ncbi.nlm.nih.gov/25936450/
[5] https://pubmed.ncbi.nlm.nih.gov/34031295/
[6] https://www.epilepsiaopen.org/article/S2472-8650(21)00015-1/full
[7] https://pubmed.ncbi.nlm.nih.gov/34370868/
[8] https://pubmed.ncbi.nlm.nih.gov/28714128/
[9] https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fenfluramine-marketed-fintepla-information
[10] https://pubmed.ncbi.nlm.nih.gov/32413169/
[11] Fintepla prescribing info: https://www.accessdata.fda.gov/drugsatfdadocs/label/2020/212126s000lbl.pdf
[12] Diacomit prescribing info: https://www.accessdata.fda.gov/drugsatfdadocs/label/2018/022030s013lbl.pdf
[13] https://pubmed.ncbi.nlm.nih.gov/34766456/
[14] https://www.goodrx.com/classes/anticonvulsants/dravet-syndrome-medications-cost
[15] https://www.drugpatentwatch.com/