Rare Diseases Clinical Trials Update: Week 25, 2026

Published June 19, 2026 — 5 trials covered

By Victor Lafforgue, Founder of TrialsAlert. Blog posts are AI-drafted from ClinicalTrials.gov source data and reviewed by the editorial team. See our editorial policy for details.

Pediatric Patients Aged 1 to 6 Years With APDS

This Phase 3 trial is testing leniolisib, an oral medication, in young children with Activated Phosphoinositide 3-Kinase Delta Syndrome (APDS), a rare immune system disorder. If successful, leniolisib could address the root cause of APDS, potentially improving immune system function and reducing serious health complications. The study is active but not currently recruiting and includes sites in the United States and Europe.

Safety and Efficacy of Eliglustat With or Without Imiglucerase in Pediatric Patients With Gaucher Disease (GD) Type 1 and Type 3

This completed Phase 3 trial evaluated eliglustat, an oral treatment, with or without imiglucerase enzyme infusions, in children aged 2 to under 18 who have Gaucher Disease Types 1 and 3. The findings may support a new treatment option that reduces the need for regular enzyme infusions, making management easier and enhancing quality of life for affected children. The study involved 57 participants across multiple countries.

How Simplified Language Affects Comprehension and Learning in Young Children With Down Syndrome

This study is exploring whether using simpler language helps young children with Down syndrome understand and learn new words better. If effective, this approach could offer caregivers and educators an easy-to-use method to support language development in children with Down syndrome. The trial is recruiting 30 children in the United States.

Safety, Tolerability, and Preliminary Effectiveness of CTH120 in Fragile X Syndrome

This Phase 2 trial is testing the drug CTH120 in adult males with Fragile X syndrome, a genetic condition that can cause intellectual and behavioral challenges. The goal is to see if CTH120 is safe and can improve symptoms, potentially providing a new treatment option. Recruitment is ongoing in Spain with plans to include 30 participants.

Low- vs High-Dose Sirolimus With Prednisolone for KHE and KMP

This Phase 2 trial compares low versus high doses of sirolimus combined with prednisolone in children with kaposiform hemangioendothelioma and Kasabach-Merritt phenomenon, rare blood vessel and clotting disorders. The study aims to find a dose that balances effectiveness with fewer side effects, improving safety for children undergoing treatment. The trial is recruiting 76 participants in China.

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