Clinical Takeaway
Transdermal cannabidiol gel (ZYN002) has demonstrated an acceptable long-term safety and tolerability profile in children and adolescents with Fragile X syndrome across an ongoing open-label extension study. The transdermal delivery format offers a practical administration route for a pediatric population where swallowing pills or tolerating oral liquids may be challenging. These interim findings support continued investigation of cannabidiol as a targeted intervention for behavioral symptoms in FXS, given the known role of dysregulated endocannabinoid signaling in this condition.
#20 Long-term safety and tolerability of transdermal cannabidiol gel in children and adolescents with Fragile X syndrome (ZYN2-CL-017): an interim analysis of an ongoing open-label extension study.
Citation: Berry-Kravis Elizabeth et al.. Long-term safety and tolerability of transdermal cannabidiol gel in children and adolescents with Fragile X syndrome (ZYN2-CL-017): an interim analysis of an ongoing open-label extension study.. Journal of neurodevelopmental disorders. 2025. PMID: 41254489.
Design: 5 Journal: 0 N: 2 Recency: 2 Pop: 2 Human: 1 Risk: -2
This interim analysis provides critical long-term safety and tolerability data for transdermal cannabidiol in a pediatric population with FXS, addressing a significant evidence gap since cannabinoid therapeutics remain poorly characterized in children despite growing clinical interest. The transdermal delivery system offers a pharmacologically advantageous alternative to oral formulations by potentially improving bioavailability and reducing first-pass metabolism, which may enhance therapeutic efficacy while maintaining safety in this vulnerable developmental population. These findings are essential for informing regulatory pathways and clinical decision-making regarding cannabinoid use in FXS, a monogenic disorder with limited pharmacological treatment options for behavioral symptoms.
Quality Gate Alerts:
- Preclinical only
Methodological Considerations:
- Open-label design — placebo effect not excluded
Abstract: BACKGROUND: Dysregulated endocannabinoid signaling is involved in Fragile X syndrome (FXS), suggesting a potential role for the endocannabinoid signaling modulator, cannabidiol, in treatment. ZYN002 is a synthetic cannabidiol that has been uniquely formulated as a gel for transdermal delivery and is currently under investigation for the treatment of behavioral symptoms associated with FXS. DESIGN: ZYN2-CL-017 is an ongoing, long-term, open-label extension (OLE) safety trial of ZYN002 in patients with FXS. We are enrolling patients from past and current ZYN002 clinical trials to evaluate the safety and tolerability of ZYN002 in patients with FXS. METHODS: Primary safety assessments were conducted in patients who enrolled into the OLE from 2 completed ZYN002 trials. Secondary analyses, conducted in a subgroup enrolled from a completed placebo-controlled trial of ZYN002, included the FXS-specific Aberrant Behavior Checklist-Community Social Avoidance and Irritability subscales (ABC-CFXS SA and ABC-CFXS Irr, examined change from baseline of the randomized study) and the Caregiver Global Impression of Change (CaGI-C, examined change from baseline of the OLE), in which caregivers were asked to rate the change in their child’s overall behavior. RESULTS: At the time of this interim analysis data cut (January 31, 2024), 240 patients had been enrolled from 2 completed ZYN002 trials. Mean age at entry to the OLE was 9.7 years (range 3-17 years), and the majority were male (76.3%) and White (80.4%). Mean exposure to ZYN002 during the initial trials and OLE was 28 months. Treatment-related adverse events (AEs) were reported in 12.9% of patients; the most common (6.7% of patients) was short-term application site pain. The highest degree of skin irritation reported by investigators was moderate erythema in 7 patients (2.9%). In the secondary analysis cohort (n=196 evaluable patients), patients demonstrated clinically meaningful changes in ABC-CFXS SA, ABC-CFXS Irr, and CaGI-C scor
🧬 This interim safety analysis of transdermal cannabidiol in pediatric Fragile X syndrome patients addresses an underexplored therapeutic avenue rooted in plausible endocannabinoid dysfunction, though the open-label design without a concurrent control group limits our ability to distinguish genuine drug effects from natural disease progression, placebo response, or regression to the mean. The transdermal delivery approach is pragmatically appealing for this population, potentially improving adherence compared to oral formulations, yet we must acknowledge that long-term cannabinoid effects in developing brains remain incompletely characterized, and safety signals may take years to fully emerge. Confounders such as concurrent medications, variable dosing adherence in a gel formulation, and the heterogeneous behavioral phenotype of FXS itself complicate interpretation of efficacy claims in an extension cohort where only the most tolerant or responsive patients may continue. Until randomized controlled data become available, clinicians should view cannabidiol as an investigational option for carefully selected F