Clemastine Fumarate in the Treatment of Neurodevelopmental Delays in Williams Syndrome

Inclusion Criteria: 1. Age 3-6 years old; 2. Positive fluorescence in situ hybridization (FISH) test confirmed Williams syndrome; 3. GTF2I gene mutation was detected by whole exon; 4. Heart safety variables are normal (e.g. normal ECG, blood pressure 120-129/80-84) Exclusion Criteria: 1. WS patients with other gene mutations; 2. Used antihistamines, monoamine oxidase inhibitors, barbiturates and sedatives, as well as drugs affecting cognitive behavior, limb movement, white matter myelin, and MRI within 2 months before enrollment; 3. Patients with narrow-angle glaucoma, narrow peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy and bladder neck obstruction; Accompanied by severe immunodeficiency disease; 4. Allergic to Clomastine fumarate or other arylalkylamine antihistamines or any receptor; 5. According to the recent interpretation of MRI and neuroradiology experts or WS, there are obvious brain lesions that are not related to WS disease; 6. Clinically significant metabolic, hematological, liver, immune, urinary, endocrine, neurological, pulmonary, psychiatric, skin, allergic, renal, or other major diseases that may affect the interpretation of study findings or patient safety in WS's judgment;