# Cannabinoid Clinical Trials: CBD Gel Safety in Fragile X > **Author:** Benjamin Caplan, MD (ABFM Board Certified, MA Lic. #240562, NPI: 1962722637) > **Publisher:** CED Clinic (https://cedclinic.com) > **Canonical URL:** https://cedclinic.com/transdermal-cannabidiol-gel-fragile-x-syndrome-safety/ > **Published:** 2026-03-04T02:51:59-04:00 | **Last Modified / Clinically Audited:** 2026-09-28T11:12:11-04:00 > **Clinical Summary:** Explore transdermal cannabidiol gel fragile x syndrome safety data from clinical trials assessing long-term tolerability in pediatric patients. --- #### Clinical Takeaway Transdermal cannabidiol gel (ZYN002) has been studied in children and adolescents with Fragile X syndrome through an open-label extension trial focused on long-term safety and tolerability. Early interim data suggest the synthetic CBD formulation is being evaluated for its potential to address behavioral symptoms linked to dysregulated endocannabinoid signaling in this population. No conclusions about efficacy can be drawn from this interim safety analysis alone. ### #19 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](https://cedclinic.com/medical-cannabis-gilles-de-la-tourette-syndrome-experience/). 2025. PMID: 41254489. **Study type:** Journal Article, Randomized Controlled Trial  |  **Topic area:** Cannabidiol  |  **CED Score:** 10 Design: 5 Journal: 0 N: 2 Recency: 2 Pop: 2 Human: 1 Risk: -2 Why This Matters This interim analysis provides crucial long-term safety data for transdermal cannabidiol in a pediatric population with Fragile X syndrome, a rare genetic disorder lacking FDA-approved behavioral treatments and representing an underserved clinical need. The transdermal formulation addresses significant barriers to [cannabinoid therapy](https://cedclinic.com/unknown-cannabinoid-receptor-brain-damage-relief/) in children by improving tolerability and compliance compared to oral alternatives while allowing for dose titration based on individual response and safety profiles. These findings support the continued clinical development of cannabidiol as a potential disease-modifying therapy targeting the dysregulated endocannabinoid signaling underlying FXS pathophysiology. **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](https://cedclinic.com/endocannabinoid-system-emotional-memory-ptsd-treatment/) 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](https://cedclinic.com/cbd-endocrine-effects-gynecomastia-risk-safety/) (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 Clinical Perspective This interim analysis of an open-label extension study provides valuable long-term safety data for transdermal cannabidiol in pediatric Fragile X syndrome, a rare condition where endocannabinoid dysregulation may contribute to behavioral symptoms. The transdermal formulation is theoretically advantageous for children and adolescents, potentially avoiding hepatic first-pass metabolism and improving adherence compared to oral alternatives. However, the open-label design without a control group limits our ability to distinguish true drug effects from placebo response, natural disease progression, or confounding by concurrent therapies, and interim analyses may overestimate safety signals that stabilize with longer follow-up. The relatively small population with FXS also means findings may not generalize broadly to other pediatric conditions. Given the lack of established treatments for FXS-related behavioral symptoms and the theoretical mechanism of action, this safety data could support cautious consideration of cannabidiol in selected patients refractory to standard interventions, while practitioners should maintain realistic expectations about  |   |  Further Reading Cannabis News[Youth and cannabis: What’s the risk? – The Lewiston Tribune](https://cedclinic.com/cannabis-use-adolescent-brain-risks/) CED Clinic Blog[5 Essential Truths About Pediatric Cannabis Care: A Comprehensive Look](https://cedclinic.com/cannabinoids-in-pediatric-care-evidence-insights/) Cannabis Memes[College is hard lmao](https://cedclinic.com/college-is-hard-lmao/) Further Reading Research Digest[CED Cannabis Research Digest — February 27, 2026](https://cedclinic.com/cannabis-medicine-research-digest-february-27-2026/) CED Clinic Blog[5 Essential Truths About Pediatric Cannabis Care: A Comprehensive Look](https://cedclinic.com/cannabinoids-in-pediatric-care-evidence-insights/) CED Clinic Blog[Why Cannabis Works](https://cedclinic.com/why-cannabis-works/) [View on PubMed ↗](https://pubmed.ncbi.nlm.nih.gov/41254489/)[Full Text ↗](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12625530/)[DOI ↗](https://doi.org/10.1186/s11689-025-09657-x) RELATED READING AT CED CLINIC Continue exploring the evidence [Transdermal CBD Gel Safety in Fragile X: Clinical Data](https://cedclinic.com/transdermal-cannabidiol-gel-safety-fragile-x-syndrome/) Detailed [clinical data](https://cedclinic.com/uk-germany-medical-cannabis-markets-double-2025/) on the safety profile of transdermal CBD gel in children with Fragile X syndrome. [Read Clinical Data](https://cedclinic.com/transdermal-cannabidiol-gel-safety-fragile-x-syndrome/) [Cannabinoid Clinical Trials: Evidence-Based Pediatric Care](https://cedclinic.com/cannabinoid-use-pediatric-epilepsy-clinical-trials/) Overview of cannabinoid [clinical trials](https://cedclinic.com/endocannabinoid-system-emotional-memory-ptsd-treatment/) focusing on pediatric populations and safety outcomes. [Explore Pediatric Care](https://cedclinic.com/cannabinoid-use-pediatric-epilepsy-clinical-trials/) [Phase 2, open-label INSPIRE trial to assess the tolerability and effectiveness of transdermal cannabidiol gel in children and adolescents with 22q11.2 deletion syndrome (ZYN2-CL-031).](https://cedclinic.com/transdermal-cannabidiol-gel-children-inspire-trial/) Insights from a phase 2 trial evaluating transdermal cannabidiol gel tolerability in a pediatric genetic disorder population. [Learn About INSPIRE Trial](https://cedclinic.com/transdermal-cannabidiol-gel-children-inspire-trial/) Have thoughts on this? Share it: [X Share on X](https://twitter.com/intent/tweet?text=Cannabinoid%20Clinical%20Trials%3A%20CBD%20Gel%20Safety%20in%20Fragile%20X&url=https%3A%2F%2Fcedclinic.com%2Ftransdermal-cannabidiol-gel-fragile-x-syndrome-safety%2F) [in Share on LinkedIn](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fcedclinic.com%2Ftransdermal-cannabidiol-gel-fragile-x-syndrome-safety%2F) [Share on BlueSky](https://bsky.app/intent/compose?text=Cannabinoid%20Clinical%20Trials%3A%20CBD%20Gel%20Safety%20in%20Fragile%20X%20https%3A%2F%2Fcedclinic.com%2Ftransdermal-cannabidiol-gel-fragile-x-syndrome-safety%2F) [Follow on Instagram](https://www.instagram.com/drbenjamincaplan) [Read more on Substack](https://doctorapprovedcannabis.substack.com/) [Subscribe via RSS](https://cedclinic.com/feed/) ### Related --- ### Verification & Medical Governance - **Lead Clinical Author:** Benjamin Caplan, MD - **Credentials:** Board Certified in Family Medicine (ABFM), Founder & CMO CED Clinic & CED Foundation, Author of *The Doctor-Approved Cannabis Handbook* (Penguin Random House). - **Clinical Scale:** 350,000+ lifetime evaluations overseen; 81,008-patient Real-World Evidence Registry (`~/.ced_rwe_vault.db`); 125,000+ peer-reviewed study literature observatory (`http://localhost:8768/api/explorer/terminal`). - **License Verification:** Commonwealth of Massachusetts License #240562 (https://checkahealthlicense.mass.gov/). - **NPI Registry:** 1962722637 (https://npiregistry.cms.hhs.gov/provider-view/1962722637). - **Ethics & Data Privacy:** Clinical registry observations adhere strictly to HIPAA Safe Harbor de-identification (45 CFR § 164.514(b)) and criteria for secondary research exemption under 45 CFR § 46.104(d)(4).