Stiripentol (STP) is an anticonvulsant drug that can block CYP3A4's (noncompetitively) and CYP2C19's (competitively) N-demethylation of CLB to N-desmethylclobazam (NCLB). The best models to explain the inhibition of CLB demethylation by Stiripentol (STP) are the competitive inhibition model with Ki=0.52 μM for the cDNA-expressing CYP2C19 and the noncompetitive inhibition model with apparent Ki=1.6 μM for the cDNA-expressing CYP3A4. Stiripentol (STP) has a Ki=0.14 μM and competitively inhibits the formation of OH-NCLB from NCLB by cDNA-expressing CYP2C19[1].

Stiripentol (STP) is an anticonvulsant drug that can block CYP3A4's (noncompetitively) and CYP2C19's (competitively) N-demethylation of CLB to N-desmethylclobazam (NCLB). The best models to explain the inhibition of CLB demethylation by Stiripentol (STP) are the competitive inhibition model with Ki=0.52 μM for the cDNA-expressing CYP2C19 and the noncompetitive inhibition model with apparent Ki=1.6 μM for the cDNA-expressing CYP3A4. Stiripentol (STP) has a Ki=0.14 μM and competitively inhibits the formation of OH-NCLB from NCLB by cDNA-expressing CYP2C19[1].

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Stiripentol competitively inhibited the hydroxylation of N-desmethylclobazam (NCLB) to 4′-hydroxy-N-desmethylclobazam (OH-NCLB) mediated by cDNA-expressed CYP2C19, with a Ki of 0.139 ± 0.025 μM and an IC50 of 0.276 μM.
Stiripentol noncompetitively inhibited the N-demethylation of clobazam (CLB) to NCLB mediated by cDNA-expressed CYP3A4, with a Ki of 1.59 ± 0.07 μM and an IC50 of 1.58 μM.
Stiripentol competitively inhibited the N-demethylation of CLB to NCLB mediated by cDNA-expressed CYP2C19, with a Ki of 0.516 ± 0.065 μM and an IC50 of 3.29 μM.
The inhibitory effect of stiripentol on CLB demethylation by CYP3A4 was much weaker than that of ketoconazole (IC50 = 0.023 μM), whereas its effect on NCLB hydroxylation by CYP2C19 was much stronger than that of omeprazole (IC50 = 2.99 μM). [1]

The difference in temperature between BT1 (39.67±1.09°C) and BT2 (41.32±1.05°C) in mice receiving Stiripentol (STP) monotherapy reaches statistical significance (t=3.097, p<0.05). Between Stiripentol (STP) monotherapy and CLB monotherapy, there is a statistically significant difference in BT2 (t=2.615, p<0.05). The difference between BT1 (40.18±0.58°C) and BT2 (43.03±0.49°C) in mice receiving Stiripentol (STP)+CLB combination therapy reaches statistical significance (t=10.44, p<0.01)[2].

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In a randomized, placebo-controlled trial involving pediatric patients with severe myoclonic epilepsy in infancy (SMEI), co-administration of stiripentol (mean daily dose 49 ± 2 mg/kg/day) with clobazam (0.5 mg/kg/day) and valproate resulted in significant changes in plasma concentrations compared to baseline.
The mean normalized minimum plasma concentrations of CLB and NCLB increased significantly from 0.39 to 0.84 (mg/l)/(mg/kg) and from 3.6 to 11.6 (mg/l)/(mg/kg), respectively.
The mean normalized minimum plasma concentration of OH-NCLB decreased significantly from 0.258 to 0.063 (mg/l)/(mg/kg).
The NCLB/CLB plasma concentration ratio increased by 269%, while the OH-NCLB/NCLB ratio decreased by 86%. OH-CLB was not detected in patient plasma. [1]

Incubation mixtures contained 100 mM phosphate buffer (pH 7.4), 0.5 mg/ml MgCl2, 1 mM NADP+, 0.5 mg/ml glucose 6-phosphate, 0.5 U/ml glucose 6-phosphate dehydrogenase, the inhibitor (stiripentol, ketoconazole, or omeprazole), and the substrate (CLB or NCLB) in a final volume of 0.5 ml. CLB and NCLB concentrations were chosen within the therapeutic plasma concentration range (2 μM and 14 μM, respectively). Reactions were initiated by adding cDNA-expressed human CYP3A4 or CYP2C19 (final P450 concentration 50 nM). Incubations were performed for 10 min (CYP3A4) or 30 min (CYP2C19) at 37°C and stopped by adding ice-cold acetonitrile.
To determine the inhibition constant (Ki), various concentrations of CLB (2–100 μM) were incubated with increasing concentrations of stiripentol (0–5 μM) for CYP3A4- and CYP2C19-mediated demethylation. For CYP2C19-mediated NCLB hydroxylation, various concentrations of NCLB (1.5–14 μM) were incubated with increasing concentrations of stiripentol (0–2 μM). All incubations were conducted in duplicate.
To determine the IC50, the substrate (2 μM CLB or 14 μM NCLB) was coincubated with increasing concentrations of stiripentol (0.001–10 μM). For comparison, IC50 values for ketoconazole and omeprazole were also determined using similar concentration ranges. [1]

150, 300 mg/kg; i.p. Mice

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Heterozygous Scn1a^RX/+ mice (a model of Dravet syndrome) and age-matched wild-type mice were used. Mice were anesthetized with isoflurane, and EEG electrodes were implanted into the skull at least 24 hours before seizure induction.
Hyperthermia-induced seizures were provoked by placing the mouse in a heated box, with body temperature gradually increased by approximately 0.1°C per 10 seconds using a hot plate and an electric light bulb. Rectal temperature was monitored continuously. The heating was stopped when a seizure was observed on EEG or when rectal temperature reached 45°C.
For drug efficacy testing, baseline seizure-inducing body temperature (BT₁) and seizure duration (D₁) were first determined in Scn1a^RX/+ mice. After a 48-hour recovery period, drugs were administered via intraperitoneal injection. Stiripentol was suspended in saline (0.9% NaCl) containing 1% Tween 80 (v/v). Seizure induction was repeated 1 hour after drug administration to determine post-treatment seizure-inducing body temperature (BT₂) and duration (D₂).
Two age groups were tested: young mice (p1M, aged 4 weeks) and older mice (p5M, aged 5–10 months). In the young group, mice received either Stiripentol monotherapy (300 mg/kg), clobazam (CLB) monotherapy (6.62 mg/kg), or combination therapy (Stiripentol 150 mg/kg + CLB 6.62 mg/kg). The Stiripentol dose in the young combination group was reduced from 300 mg/kg due to severe toxicity (hypothermia and death) observed at the higher dose in pilot studies.
In the older group, mice received either Stiripentol monotherapy (300 mg/kg), CLB monotherapy (6.62 mg/kg), or combination therapy (Stiripentol 300 mg/kg + CLB 6.62 mg/kg).
Blood samples were collected 1 hour and 20 minutes after drug administration for measurement of plasma drug concentrations. [1]

Absorption, Distribution and Excretion
Following oral administration, staefenol is rapidly absorbed, with a median time to peak concentration (Tmax) of 2–3 hours. Systemic exposure increases proportionally with dose. Due to its insolubility in water and extensive metabolism, staefenol has low bioavailability. Staefenol is primarily eliminated through metabolism. Its metabolites are mainly excreted via the kidneys. After an acute oral dose, the majority (73%) of the total staefenol metabolites are excreted in the urine, with an additional 13–24% excreted unchanged in the feces. The mean volume of distribution is 1.03 L/kg, but this is dose-independent. After administration, staefenol enters the brain and accumulates in the cerebellum and medulla oblongata. High doses significantly reduce plasma clearance; it decreases from approximately 40 L/kg/day at a 600 mg daily dose to approximately 8 L/kg/day at a 2400 mg daily dose. The clearance rate of staepentol decreased after repeated administration, likely due to inhibition of the cytochrome P450 isoenzymes responsible for its metabolism. Metabolism/Metabolites Staepentol is extensively metabolized. Approximately 13 different metabolites have been identified in urine. The major metabolic processes are demethylenelation (oxidative cleavage of the methylenedioxy ring system) and glucuronidation, but the enzymes involved have not been precisely identified. Other metabolic pathways include O-methylation of catechol metabolites, hydroxylation of tert-butyl groups, and conversion of the allyl alcohol side chain to the isomer 3-pentanone. In vitro studies have shown that phase I metabolism of staepentol is catalyzed by CYP1A2, CYP2C19, and CYP3A4, as well as other possible enzymes. Biological Half-Life The elimination half-life is approximately 4.5 to 13 hours, and is dose-dependent.

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In pediatric patients receiving a mean daily dose of 49 ± 2 mg/kg/day, the mean lowest steady-state plasma concentration of staefenol was 10.0 ± 3.6 mg/L (equivalent to 42.7 ± 15.4 μM). [1]
The commonly used steady-state plasma concentration range of staefenol is reported to be 10 to 60 μM. [1]

Hepatotoxicity
Limited safety data exist for staepentol, primarily based on small, open-label, placebo-controlled clinical trials in children with Dravet syndrome. In these studies, adding staepentol to long-term clobazine therapy did not increase the incidence of elevated serum transaminases or clinically significant liver injury. Long-term use of staepentol is associated with lower rates of ALT and alkaline phosphatase elevation, but up to 38% of cases show elevated gamma-glutamyl transferase (GGT). No published case reports of hepatotoxicity have been received since the widespread use of staepentol. Therefore, clinically significant liver injury caused by staepentol, even if it occurs, is extremely rare. Probability Score: E (Unlikely a cause of clinically significant liver injury). Pregnancy and Lactation Effects ◉ Overview of Use During Lactation Since there is currently no information regarding the use of staepentol during lactation, alternative medications are recommended, especially for breastfeeding newborns or preterm infants.
◉ Effects on breastfed infants
No published information found as of the revision date.
◉ Effects on lactation and breast milk
No published information found as of the revision date.

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Protein binding
The protein binding rate of steptospirol is 99%.

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In a preliminary study, administration of high doses of steptospirol (300 mg/kg) and intraperitoneal injection of clobazian (6.62 mg/kg) to four 1-month-old Scn1a^{RX/+ mice resulted in severe hypothermia (approximately 20°C) and death within 1 hour. This severe toxicity prompted the reduction of the steptospirol dose to 150 mg/kg in the combination therapy regimen in the juvenile rat group in the primary study. [1]}

[1]. In vitro and in vivo inhibitory effect of stiripentol on clobazam metabolism.Drug Metab Dispos. 2006 Apr;34(4):608-11. Epub 2006 Jan 13.

[2]. Efficacy of stiripentol in hyperthermia-induced seizures in a mouse model of Dravet syndrome. Epilepsia. 2012 Jul;53(7):1140-5.

Pharmacodynamics
Stevastatin is an antiepileptic drug that reduces the frequency of seizures. When used alone, it has anticonvulsant effects and may enhance GABAergic inhibition through several proposed mechanisms. It offers a therapeutic advantage by inhibiting cytochrome P450 enzymes that typically metabolize other antiepileptic drugs, thereby improving the efficacy of those drugs. The anticonvulsant activity of stevastatin is age-related, with better efficacy in younger patients. Stevastatin is an anticonvulsant often used in combination with crobazal and sodium valproate to treat severe myoclonic epilepsy in infants (SMEI). Its clinical efficacy is related to its ability to inhibit cytochrome P450 enzymes (especially CYP2C19), thereby increasing the plasma concentration of the active metabolite of crobazal, N-demethylclobarazal (NCLB), and enhancing the antiepileptic effect of crobazal. This drug interaction has therapeutic effects, not just adverse reactions. [1]
The inhibitory effect of staptinol may be influenced by CYP2C19 gene polymorphisms. Patients carrying the defective CYP2C19 allele may experience varying degrees of metabolic interactions. [1]

C₁₄H₁₈O₃

234.29

234.125

49763-96-4

Stiripentol-d9;1185239-64-8

5311454

White to off-white solid powder

1.1±0.1 g/cm3

365.4±11.0 °C at 760 mmHg

73-74ºC

174.8±19.3 °C

0.0±0.9 mmHg at 25°C

1.579

3.39

1

3

3

17

280

0

CC(C)(C)C(/C=C/C1=CC2=C(C=C1)OCO2)O

IBLNKMRFIPWSOY-FNORWQNLSA-N

InChI=1S/C14H18O3/c1-14(2,3)13(15)7-5-10-4-6-11-12(8-10)17-9-16-11/h4-8,13,15H,9H2,1-3H3/b7-5+

(E)-1-(1,3-benzodioxol-5-yl)-4,4-dimethylpent-1-en-3-ol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.08 mg/mL (8.88 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (8.88 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (8.88 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)