Study of the Efficacy of Topiramate in Patients With Prader Willi Syndrome Over 8 Weeks

Scientific background and justification of the study :

Patients with a rare disease are often challenging to treat when considering psychotropic treatment for behavioral or psychiatric manifestations. There is an important lack of clear data or treatment guidelines for treating behavioral disturbance in patients with intellectual disabilities. Prader Willi syndrome (PWS) is a paradigmatic example of such a disease. It is a rare disease with an estimated prevalence of 1:25,000 at birth. PWS is a genetic disease located on chromosome 15 (15 q11-q13). Imprinting silence the normal genes on 15 q11-Q13, rendering them non-functional, with the paternal non-imprinted genes being deleted. The imprinting effect in this region explains why approximately 60 to 70% of patients with PWS have a paternal deletion of 15q11-q13 (2). An additional 25 to 35 % of patients have two copies of maternal chromosome 15 (uniparental disomy). Rarely, PWS may be associated with translocation, mutation, or other anomalies. Angelman Syndrome, which has primarily been associated with autism spectrum disorders, involves the same genetic region and is commonly associated to mutations of the maternal allele of the UB3a gene or rare deletions. .

PWS patients present in a neonatal hypotonic state with deficit of sucking and eating refusal which progresses to with hyperphagia and obsession with food in infancy or adolescence. In addition, patients have distinct facial features, such as a narrow forehead, almond-shaped eyes, and a triangular mouth, as well as a short stature, related to growth hormone deficiency and small hands and feet. Puberty is often delayed or incomplete, and most affected individuals are unable to have children. This eating disorder is more similar to an addictive disorder to food than a traditional eating disorder. PWS leads to severe obesity, which is a major issue associated with quality of life and medical prognosis.

Psychiatric and cognitive symptoms in patients with PWS are severe and have an important impact on social and interpersonal life. Patients with PWS often have mild to moderate intellectual disability (ID), with learning impairments and poor academic achievement. They have particular difficulties in mathematics, calculation, and abstraction, which may be related to under-diagnosed neuro-visual impairments. There is a large individual heterogeneity of language impairments, primarily in morphosyntaxic abilities. Behavioral impairments predominately include temper outbursts, impulsivity, emotional liability and aggressive behavior , as well as self-injury behavior, such as compulsively picking the skin and mucosa (rectal picking), which may lead to a severe wound and severe infections. Patients with disomy as a group have more severe overall symptoms than patients with a deletion.

Regarding the relationship between PWS and schizophrenia spectrum disorders (SSDs), 5 studies have utilized standardized psychometric tools to assess psychiatric diagnoses. SSDs are primarily, but not exclusively, associated with disomy, and the clinical diagnosis may be complicated. Considering that disomy represents only 20%, at most, of patients, SSDs affect less than 20% of patients with PWS, most likely approximately 17% or 15%. There are few studies in the field of behavioral treatment in PWS they suggests that risperidone for psychotic symptoms associated with disomy, and N-acetylcysteine for skin picking might be efficient. Moreover and despite many study limitations, the investigators identified promising treatment effects with topiramate for self-injury and impulsive/aggressive behaviors. To date there is only one study (open trial) for topiramate in PWS.

Our aim is to assess efficacy and tolerance of topiramate in behavioral disturbance in patients with PWS.

Main objective :

Assess the efficacy and tolerance of topiramate at 200 mg / day on hyperphagia (H), seflf-injury (SI) and Irritability-Impuslivity Behavior in patients with Prader Willi Syndrome during an 8 weeks follow-up.

Secondary objective Assess the tolerance and side effect ot topiramate 200mg/day in this specific population.

Methodology :

The investigators will run a multicentric double blind placebo controlled randomized trial with outpatients in Paris and Toulouse and inpatients in Hendaye. Inclusion period is 3 years in order to obtain a total number of participants of 125 randomly assigned in two groups (drug vs placebo).

Local Ethic Committee did approve this research. Patients and/or their parents / caregiver give informed consent.

Main outcome measure will be Clinical Global Impression thereshold will be to obtain at least 1 at CGI Improvement scoring at endpoint after 8 weeks follow-up.

Secondary outcome (psychometric scales and biological measures):

• Weight, Self-Injury Behavior, C-SHARP and A-SHARP (suicide ideation scale, according to age), CONNERS Impulsivity, Dickens (Hyperphagia)
• Sides effects assessment; PANNS (for hallucinations), Eysenck Anxiety
• And biological assessment including lipid, hepatic enzyme, insulin, serum bicarbonate, leptin, amoniemia, ghreline and HbA1c.

Instruments and assessments. Psychometric scales: Impulsivity and aggressive behavior will be evalauated with irritability sub-score of Aberrant Behaviour Checklist The Children's Scale of Hostility and Aggression: Reactive/Proactive (C-SHARP) for adolescents until 16 years-old and The Adult Scale of Hostility and Aggression: Reactive/Proactive (A-SHARP) for adults. The Dickens questionnaire, especially oriented for PWS patients, will be used for eating behavior. Self injury behavior will be assessed with Scale of Self-Aggressive Behavior (ECAA Yale-Paris), especially in the sub -scale regarding severity, duration and frequency of such behavior. The Clinical Global Impression, will be used at base line, 2, 4, 6 and 8 weeks (endpoint).

Scale for the Assesment of Positive Symptoms, SAPS, and Brief Psychiatric Rating Scale, BPRS, Hamilton Anxiety Sclale, HAS et Columbia Classification Algorithm of Suicide Assessment (C-CASA).

Somatic assessment: Blood sample with routine elements associated with complete blood count, creatinin, amoniemia serum bicarbonate, ASAT/ALAT/γGT, glycemia lipid profil and insulin, ghrelin, leptin, TG and HbA1c. Weight and size in order to calculate the Body Mass Index. Centralized blood level of drug concentration at baseline (no treatment), week 4 and week 8.

Design and timeline :

Selection will be made on inclusion/exclusion criteria including blood sample. Inclusion and randomization is at baseline and all assessments will be made.

Visits are scheduled at week 2, 4, 6 and 8 (endpoint and end of patient participation). All scales are used for all visit and biological sample are made at selection, inclusion, week 4 and week 8.