Safety and efficacy of ganaxolone in patients with CDKL5 deficiency disorder: results from the double-blind phase of a randomised, placebo-controlled, phase 3 trial.

BACKGROUND: CDKL5 deficiency disorder (CDD) is a rare, X-linked, developmental and epileptic encephalopathy characterised by severe global developmental impairment and seizures that can begin in the first few months after birth and are often treatment refractory. Ganaxolone, an investigational neuroactive steroid, reduced seizure frequency in an open-label, phase 2 trial that included patients with CDD. We aimed to further assess the efficacy and safety of ganaxolone in patients with CDD-associated refractory epilepsy. METHODS: In the double-blind phase of this randomised, placebo-controlled, phase 3 trial, done at 39 outpatient clinics in eight countries (Australia, France, Israel, Italy, Poland, Russia, the UK, and the USA), patients were eligible if they were aged 2-21 years with a pathogenic or probably pathogenic CDKL5 variant and at least 16 major motor seizures (defined as bilateral tonic, generalised tonic-clonic, bilateral clonic, atonic, or focal to bilateral tonic-clonic) per 28 days in each 4-week period of an 8-week historical period. After a 6-week prospective baseline period, patients were randomly assigned (1:1) via an interactive web response system to receive either enteral adjunctive ganaxolone or matching enteral adjunctive placebo (maximum dose 63 mg/kg per day for patients weighing ≤28 kg or 1800 mg/day for patients weighing >28 kg) for 17 weeks. Patients, caregivers, investigators (including those analysing data), trial staff, and the sponsor (other than the investigational product manager) were masked to treatment allocation. The primary efficacy endpoint was percentage change in median 28-day major motor seizure frequency from the baseline period to the 17-week double-blind phase and was analysed (using a Wilcoxon-rank sum test) in all patients who received at least one dose of trial treatment and for whom baseline data were available. Safety (compared descriptively across groups) was analysed in all patients who received at least one dose of trial treatment. This study is registered with ClinicalTrials.gov, NCT03572933, and the open-label extension phase is ongoing. FINDINGS: Between June 25, 2018, and July 2, 2020, 114 patients were screened for eligibility, of whom 101 (median age 6 years [IQR 3 to 10]) were randomly assigned to receive either ganaxolone (n=50) or placebo (n=51). All patients received at least one dose of a study drug, but seizure frequency for one patient in the ganaxolone group was not recorded at baseline and so the primary endpoint was analysed in a population of 100 patients. There was a median percentage change in 28-day major motor seizure frequency of -30·7% (IQR -49·5 to -1·9) in the ganaxolone group and of -6·9% (-24·1 to 39·7) in the placebo group (p=0·0036). The Hodges-Lehmann estimate of median difference in responses to ganaxolone versus placebo was -27·1% (95% CI -47·9 to - 9·6). Treatment-emergent adverse events occurred in 43 (86%) of 50 patients in the ganaxolone group and in 45 (88%) of 51 patients in the placebo group. Somnolence, pyrexia, and upper respiratory tract infections occurred in at least 10% of patients in the ganaxolone group and more frequently than in the placebo group. Serious adverse events occurred in six (12%) patients in the ganaxolone group and in five (10%) patients in the placebo group. Two (4%) patients in the ganaxolone group and four (8%) patients in the placebo group discontinued the trial. There were no deaths in the double-blind phase. INTERPRETATION: Ganaxolone significantly reduced the frequency of CDD-associated seizures compared with placebo and was generally well tolerated. Results from what is, to our knowledge, the first controlled trial in CDD suggest a potential treatment benefit for ganaxolone. Long-term treatment is being assessed in the ongoing open-label extension phase of this trial. FUNDING: Marinus Pharmaceuticals.

Clobazam therapeutic drug monitoring: a comprehensive review of the literature with proposals to improve future studies.

BACKGROUND: Clobazam was recently approved for Lennox-Gastaut syndrome in the United States. There is no published review article focused on clobazam therapeutic drug monitoring (TDM) in English. METHODS: More than 200 clobazam articles identified by a PubMed search were carefully reviewed for information on clobazam pharmacokinetics. Clobazam is mainly metabolized by a cytochrome P450 (CYP) isoenzyme, CYP3A4, to its active metabolite, N-desmethylclobazam. Then, N-desmethylclobazam is mainly metabolized by CYP2C19 unless the individual has no CYP2C19 activity [poor metabolizer (PM)]. RESULTS: Using a mechanistic approach to reinterpret the published findings of steady-state TDM and single-dosing pharmacokinetic studies, 4 different serum clobazam concentration ratios were studied. The available limited steady-state TDM data suggest that the serum N-desmethylclobazam/clobazam ratio can be useful for clinicians, including identifying CYP2C19 PMs (ratio >25 in the absence of inhibitors). There are 3 possible concentration/dose (C/D) ratios. The clobazam C/D ratio has the potential to measure the contribution of CYP3A4 activity to the clearance of clobazam from the body. The N-desmethylclobazam C/D ratio does not seem to be a good measure of clobazam clearance and should be substituted with the total (clobazam + N-desmethylclobazam) C/D ratio. CONCLUSIONS: Future clobazam TDM studies need to use trough concentrations after steady state has been reached (>3 weeks in normal individuals and several months in CYP2C19 PMs). These future studies need to explore the potential of clobazam and total C/D ratios. Better studies on the relative potency of N-desmethylclobazam compared with the parent compound are needed to provide weighted total serum concentrations that correct for the possible lower N-desmethylclobazam pharmacodynamic activity. Standardization and more studies of C/D ratios from clobazam and other drugs can be helpful to move TDM forward.

D-bifunctional protein deficiency associated with drug resistant infantile spasms.

Peroxisomal disorders appear with a frequency of about 1:5000 in newborns. Peroxisomal D-bifunctional protein (D-BP), encoded by the HSD17B4 gene (gene ID: 3294; locus tag: HGNC:5213, chromosome 5q2; official symbol: HSD17B4; name: hydroxysteroid (17-beta) dehydrogenase; gene type: protein coding) (OMIM *601860), comprises an 80 kDa multifunctional enzyme involved in peroxisomal beta-oxidation of certain fatty acids and the synthesis of bile acids. Its deficiency causes a very severe, Zellweger-like clinical phenotype and most patients die within the first year of life. In this paper, we report a case of D-BP deficiency in a patient with two heterozygous trinucleotide deletions (233_235 del AAG and 824_826 del AGA) in the HSD17B4 gene. The patient suffered from a peculiar epileptic phenotype (i.e. a West syndrome with a "modified hypsarrhythmic pattern"--Hrachovy et al. Epilepsia 1984;25:317-25), clinically appearing as drug-resistant asymmetric spasms. Vigabatrin seemed the most effective among the antiepileptic drugs. The patient died at the age of 23 months owing to respiratory complications. To date, only a few patients with D-BP deficiency have been described in the literature. This case adds to our knowledge of the clinical presentation of bifunctional protein deficiency.

CDKL5/Stk9 kinase inactivation is associated with neuronal developmental disorders.

X-linked cyclin-dependent kinase-like 5 (CDKL5 or STK9) has recently been implicated in atypical Rett and X-linked West syndromes, severe neurological disorders associated with mental retardation, loss of communication and motor skills and infantile spasms and seizures in predominantly females. Besides CDKL5, these disease phenotypes are also linked to mutations in the MECP2 and ARX genes. Here, we have expressed and characterized CDKL5 and its mutant forms. CDKL5 is a 118 kDa protein that is widely distributed in all tissues, with highest levels in brain, thymus and testes. Whole mount embryo staining reveals CDKL5 to be ubiquitous. Within cells, CDKL5 is localized primarily in the nucleus. Removal of the C-terminal domain increases CDKL5 expression, enhances autophosphorylation activity and causes perinuclear localization, indicating that the C-terminus regulates CDKL5 function. Although we detect MeCP2 but not ARX binding to CDKL5, our results suggest that neither of these proteins are direct substrates of the CDKL5 kinase. Finally, the CDKL5 mutations associated with the disease phenotype cause loss of kinase activity as assessed by autophosphorylation. These results suggest that inactivation of the CDKL5 kinase can lead to severe neurodevelopmental disorders.

Lactic dehydrogenase isoenzyme in cerebrospinal fluid of children with infantile spasms.

Increased levels of lactic dehydrogenase (LDH) in cerebrospinal fluid (CSF) have been reported in association with several intracranial pathologies. We studied LDH isoenzymes in the CSF of children with infantile spasms. CSF samples collected from 12 patients (aged 4-9 months) with infantile spasms were analyzed for total LDH isoenzymes activity, and were compared to samples from 15 normal children. Mean total LDH activity in the CSF was 34.62 +/- 6.52 U/l. Patients with infantile spasms had a lower LDH-1 percentage and higher LDH-3 percentage; the differences from the control group were statistically significant (p < 0.01). LDH-4 and LDH-5 had similar values in both groups. Infantile spasm is apparently associated with a distinct LDH isoenzyme pattern in the CSF. More studies are needed to confirm the rise in LDH-2, LDH-3 and to determine the optimum time of analysis.

Concomitant administration of sodium dichloroacetate and thiamine in west syndrome caused by thiamine-responsive pyruvate dehydrogenase complex deficiency.

We treated a female patient with West syndrome caused by thiamine-responsive pyruvate dehydrogenase complex (PDHC) deficiency. Infantile spasms occurred in association with elevated blood and CSF lactate concentrations; these symptoms disappeared when lactate concentrations had been lowered by treatment with concomitant sodium dichloroacetate (DCA) and high dose thiamine. Sequencing the patient's PDHC E(1)alpha subunit revealed a substitution of serine for glycine at position 89 in exon 3 (G89S). This mutation must be a de novo mutation because it was not found in either parents' genome DNA. To our knowledge, five previously described patients with PDHC deficiency have displayed the West syndrome. All six known patients, including our own, were female, even though an approximately equal number of males and females have been identified with PDHC deficiency and overall West syndrome occurs somewhat more frequently in males. These results indicated that West syndrome occurred more frequently in female patients with PDHC deficiency. It is suggested that lactate concentration should be measured in patients with West syndrome for potential PDHC deficiency, especially in females.

Decrease of N-acetylaspartate after ACTH therapy in patients with infantile spasms.

Apparent brain atrophy has been frequently observed at CT and MRI after ACTH therapy in patients with infantile spasms. There are several hypotheses to explain ACTH-induced brain shrinkage: 1) a catabolic effect of ACTH on brain tissue, 2) a mineralocorticoid effect resulting in a loss of water and 3) an increase in cerebrospinal fluid (CSF) pressure compressing the brain. An average of 0.21 +/- 0.03 mg/kg of ACTH was administered to nine patients over a period of 14 to 17 days. Water content and concentrations of N-acetylaspartate (NAA), creatine and phosphocreatine (Cr + PCr), and choline (Cho) were measured before, immediately after, and several months after the ACTH therapy by using in-vivo 1H magnetic resonance spectroscopy (MRS). Only NAA concentration exhibited a significant change during the study (6.6 +/- 1.5 mmol/kg, 5.4 +/- 1.1, and 7.0 +/- 1.5, p = 0.017). There was no significant change in Cr + PCr, in Cho, or in water content. These data suggest catabolic effects of ACTH on brain tissue, such as cell loss, decrease in NAA synthesis in mitochondria, and leakage of NAA from cell membrane.