Role of the endocannabinoid system in fragile X syndrome: potential mechanisms for benefit from cannabidiol treatment.

Multiple lines of evidence suggest a central role for the endocannabinoid system (ECS) in the neuronal development and cognitive function and in the pathogenesis of fragile X syndrome (FXS). This review describes the ECS, its role in the central nervous system, how it is dysregulated in FXS, and the potential role of cannabidiol as a treatment for FXS. FXS is caused by deficiency or absence of the fragile X messenger ribonucleoprotein 1 (FMR1) protein, FMRP, typically due to the presence of >200 cytosine, guanine, guanine sequence repeats leading to methylation of the FMR1 gene promoter. The absence of FMRP, following FMR1 gene-silencing, disrupts ECS signaling, which has been implicated in FXS pathogenesis. The ECS facilitates synaptic homeostasis and plasticity through the cannabinoid receptor 1, CB1, on presynaptic terminals, resulting in feedback inhibition of neuronal signaling. ECS-mediated feedback inhibition and synaptic plasticity are thought to be disrupted in FXS, leading to overstimulation, desensitization, and internalization of presynaptic CB1 receptors. Cannabidiol may help restore synaptic homeostasis by acting as a negative allosteric modulator of CB1, thereby attenuating the receptor overstimulation, desensitization, and internalization. Moreover, cannabidiol affects DNA methylation, serotonin 5HT1A signal transduction, gamma-aminobutyric acid receptor signaling, and dopamine D2 and D3 receptor signaling, which may contribute to beneficial effects in patients with FXS. Consistent with these proposed mechanisms of action of cannabidiol in FXS, in the CONNECT-FX trial the transdermal cannabidiol gel, ZYN002, was associated with improvements in measures of social avoidance, irritability, and social interaction, particularly in patients who are most affected, showing ≥90% methylation of the FMR1 gene.

A randomized, controlled trial of ZYN002 cannabidiol transdermal gel in children and adolescents with fragile X syndrome (CONNECT-FX).

BACKGROUND: Fragile X syndrome (FXS) is associated with dysregulated endocannabinoid signaling and may therefore respond to cannabidiol therapy. DESIGN: CONNECT-FX was a double-blind, randomized phase 3 trial assessing efficacy and safety of ZYN002, transdermal cannabidiol gel, for the treatment of behavioral symptoms in children and adolescents with FXS. METHODS: Patients were randomized to 12 weeks of ZYN002 (250 mg or 500 mg daily [weight-based]) or placebo, as add-on to standard of care. The primary endpoint assessed change in social avoidance (SA) measured by the Aberrant Behavior Checklist-Community Edition FXS (ABC-CFXS) SA subscale in a full cohort of patients with a FXS full mutation, regardless of the FMR1 methylation status. Ad hoc analyses assessed efficacy in patients with ≥ 90% and 100% methylation of the promoter region of the FMR1 gene, in whom FMR1 gene silencing is most likely. RESULTS: A total of 212 patients, mean age 9.7 years, 75% males, were enrolled. A total of 169 (79.7%) patients presented with ≥ 90% methylation of the FMR1 promoter and full mutation of FMR1. Although statistical significance for the primary endpoint was not achieved in the full cohort, significant improvement was demonstrated in patients with ≥ 90% methylation of FMR1 (nominal P = 0.020). This group also achieved statistically significant improvements in Caregiver Global Impression-Change in SA and isolation, irritable and disruptive behaviors, and social interactions (nominal P-values: P = 0.038, P = 0.028, and P = 0.002). Similar results were seen in patients with 100% methylation of FMR1. ZYN002 was safe and well tolerated. All treatment-emergent adverse events (TEAEs) were mild or moderate. The most common treatment-related TEAE was application site pain (ZYN002: 6.4%; placebo: 1.0%). CONCLUSIONS: In CONNECT-FX, ZYN002 was well tolerated in patients with FXS and demonstrated evidence of efficacy with a favorable benefit risk relationship in patients with ≥ 90% methylation of the FMR1 gene, in whom gene silencing is most likely, and the impact of FXS is typically most severe. TRIAL REGISTRATION: The CONNECT-FX trial is registered on Clinicaltrials.gov (NCT03614663).

Pain-free results with sumatriptan taken at the first sign of migraine pain: 2 randomized, double-blind, placebo-controlled studies.

OBJECTIVE: To evaluate the efficacy and tolerability of sumatriptan, 50-mg and 100-mg tablets, compared with placebo for treatment of migraine at the first sign of pain. PATIENTS AND METHODS: Two identical multicenter randomized, double-blind, placebo-controlled, single-attack studies were conducted from May through November 2000 in adults (aged 18-65 years). Patients treated migraine at the first sign of pain, while pain was mild, but not more than 2 hours after onset with oral sumatriptan, 50 mg or 100 mg, or matching placebo. The primary end point was pain-free relief at 2 hours after treatment with 50 mg of sumatriptan compared with placebo. RESULTS: There were 354 patients in study 1 and 337 patients in study 2. Significantly more patients treated with sumatriptan, 50 mg and 100 mg, were completely free from pain 2 and 4 hours after treatment vs patients treated with placebo (at 2 hours, 50% and 57% vs 29%; at 4 hours, 61% and 68% vs 30%; for both, P < .001). Also, significantly more patients treated with sumatriptan, 50 mg and 100 mg, were migraine-free (no pain or associated symptoms) vs those treated with placebo at 2 and 4 hours after treatment (at 2 hours, 43% and 49% vs 24%; at 4 hours, 54% and 63% vs 28%; for both, P < .001). The incidence of overall adverse events was low with the 50- and 100-mg dose of sumatriptan (placebo, 7%; sumatriptan at 50 mg, 14%; sumatriptan at 100 mg, 16%). CONCLUSIONS: Treatment of migraine at the first sign of pain with sumatriptan, 50-mg and 100-mg tablets, provides superior pain-free relief at 2 and 4 hours after treatment compared with placebo. Results of these studies suggest that sumatriptan at 100 mg may be more efficacious than at 50 mg when used in the early treatment paradigm. Because these studies were not powered to detect statistical differences between active doses, studies to investigate this finding are warranted.

The pharmacokinetics of sumatriptan when administered with clarithromycin in healthy volunteers.

BACKGROUND: Macrolide antibiotics such as clarithromycin are potent inhibitors of the cytochrome P450 (CYP)3A4 isozyme and have the potential to attenuate the metabolism and increase blood concentrations of drugs metabolized by this pathway. In vitro studies have suggested that sumatriptan is metabolized primarily by the monoamine oxidase-A isozyme and not by CYP3A4. OBJECTIVE: This study sought to determine the effect of coadministration of clarithromycin dosed to steady state on the pharmacokinetics of a single dose of sumatriptan. A secondary objective was to assess the safety and tolerability of combining these agents. METHODS: This was an open-label, randomized, 2-way crossover study in healthy volunteers. During treatment period 1, subjects received either a single oral dose of sumatriptan 50 mg (sumatriptan alone) or clarithromycin 500 mg orally every 12 hours on days 1 to 3 and a single oral dose of sumatriptan 50 mg plus a single oral dose of clarithromycin 500 mg on the morning of day 4 (combination treatment). During treatment period 2, they received the alternative regimen. Equivalence between sumatriptan alone and combination treatment was concluded if the 90% CI for the ratio of reference to test means of loge-transformed data for area under the plasma concentration-time curve extrapolated to infinity (AUC(infinity)) and maximum plasma concentration (Cmax) fell within the interval from 0.8 to 1.25. RESULTS: In the 24 evaluable subjects (12 men, 12 women) included in the pharmacokinetic analysis, mean sumatriptan AUC(infinity) and Cmax values after administration of combination treatment were 9% and 14% higher, respectively, than the corresponding values after administration of sumatriptan alone. The 90% CI for the ratio of reference to test means for AUC(infinity) was 1.03 to 1.15. The 90% CI for the ratio of reference to test means for Cmax was 1.03 to 1.26, above the traditional bioequivalence criterion. All other pharmacokinetic parameters tested, including nonparametric analysis of the time to Cmax, met the criterion for equivalence between treatments. Both treatments were well tolerated in the 27 subjects (13 men, 14 women) included in the safety analysis. CONCLUSIONS: The extent of absorption of sumatriptan was similar after oral administration alone and in combination with clarithromycin dosed to steady state. These data are consistent with previous reports that sumatriptan is unaffected by coadministration with the potent CYP3A4 inhibitor clarithromycin, supporting concomitant administration of these agents without the need for dose adjustment of sumatriptan in the acute treatment of migraine.