Defining Hand Stereotypies in Rett Syndrome: A Movement Disorders Perspective

Design and outcome measures of LAVENDER, a phase 3 study of trofinetide for Rett syndrome

INTRODUCTION

Rett syndrome (RTT) is a debilitating neurodevelopmental disorder with no approved treatments. Trofinetide is a synthetic analog of glycine-proline-glutamate, the N-terminal tripeptide of insulin-like growth factor 1. In a phase 2, placebo-controlled trial in 82 females with RTT aged 5-15 years, a significant (p ≤ 0.042) improvement over placebo was observed with the highest trofinetide dose (200 mg/kg twice daily [BID]) on three measures: Rett Syndrome Behavior Questionnaire (RSBQ), Clinical Global Impression-Improvement (CGI-I), and RTT-Clinician Domain Specific Concerns-Visual Analog Scale (RTT-DSC-VAS). Trofinetide was well tolerated at all doses (50, 100, and 200 mg/kg BID). A phase 3 trial utilizing disease-specific and novel scales was designed to investigate the efficacy and safety of trofinetide in girls and women with RTT.

METHODS

This 12-week, double-blind, randomized, placebo-controlled study (LAVENDER; NCT04181723) will evaluate trofinetide in 187 females, aged 5-20 years, with RTT. Co-primary endpoints are the RSBQ and CGI-I scales. Clinical domains of the CGI-I include communication, ambulation, hand use, seizures, attentiveness, and social (eye contact) and autonomic (breathing) aspects. Secondary endpoints will leverage four novel RTT-specific clinician ratings (derived from the RTT-DSC-VAS) of hand function, ambulation, ability to communicate, and verbal communication, and existing scales, to evaluate other core symptoms of RTT, quality of life and caregiver burden. A 40-week, open-label extension study will follow.

DISCUSSION

This study was designed using disease-specific scales optimized to demonstrate changes in core symptoms of RTT and may provide the first phase 3 data demonstrating drug efficacy in individuals with RTT.

TRIAL REGISTRATION

Clinicaltrials.govNCT04181723.

GABRB2, a key player in neuropsychiatric disorders and beyond

The GABA receptors represent the main inhibitory system in the central nervous system that ensure synaptogenesis, neurogenesis, and the regulation of neuronal plasticity and learning. GABAA receptors are pentameric in structure and belong to the Cys-loop superfamily. The GABRB2 gene, located on chromosome 5q34, encodes the β2 subunit that combines with the α and γ subunits to form the major subtype of GABAA receptors, which account for 43% of all GABAA receptors in the mammalian brain. Each subunit probably consists of an extracellular N-terminal domain, four membrane-spanning segments, a large intracellular loop between TM3 and TM4, and an extracellular C-terminal domain. Alternative splicing of the RNA transcript of the GABRB2 gene gives rise at least to four long and short isoforms with dissimilar electrophysiological properties. Furthermore, GABRB2 is imprinted and subjected to epigenetic regulation and positive selection. It has been associated with schizophrenia first in Han Chinese, and subsequently validated in other populations. Gabrb2 knockout mice also exhibited schizophrenia-like behavior and neuroinflammation that were ameliorated by the antipsychotic drug risperidone. GABRB2 was also associated with other neuropsychiatric disorders including bipolar disorder, epilepsy, autism spectrum disorder, Alzheimer's disease, frontotemporal dementia, substance dependence, depression, internet gaming disorder, and premenstrual dysphoric disorder. Recently, it has been postulated that GABRB2 might be a potential marker for different cancer types. As GABRB2 has a pivotal role in the central nervous system and is increasingly recognized to contribute to human diseases, further understanding of its structure and function may expedite the generation of new therapeutic approaches.

Comparison of the presence and absence of an intervention to reduce hand stereotypies in individuals with Rett syndrome

BACKGROUND

We investigated how many individuals with Rett syndrome were undergoing interventions to reduce stereotypic hand movements and the factors determining the presence or absence of an intervention.

METHOD

A questionnaire was sent to 194 families. Each survey item was compared between the intervention and non-intervention groups according to the presence or absence of interventions to reduce hand stereotypies.

RESULTS

Information was acquired from 72 cases; 72.1% of individuals had received an intervention to reduce stereotypies at some point in their lives. An upper limb splint was the most common intervention. Age, locomotor and reaching function, diagnostic age, frequency and type of stereotypy, joint contractures and stereotypy-associated problems separated the presence or absence of a current or past intervention.

CONCLUSIONS

Interventions for stereotypy-associated problems are important and there are several variables related to whether an intervention is received.

Movement disorders in patients with Rett syndrome: A systematic review of evidence and associated clinical considerations

AIM

This systematic review identified and thematically appraised clinical evidence of movement disorders in patients with Rett syndrome (RTT).

METHOD

Using PRISMA criteria, six electronic databases were searched from inception to April 2021. A thematic analysis was then undertaken on the extracted data to identify potential themes.

RESULTS

Following the thematic analysis, six themes emerged: (i) clinical features of abnormal movement behaviors; (ii) mutational profile and its impact on movement disorders; (iii) symptoms and stressors that impact on movement disorders; (iv) possible underlying neurobiological mechanisms; (v) quality of life and movement disorders; and (vi) treatment of movement disorders. Current guidelines for managing movement disorders in general were then reviewed to provide possible treatment recommendations for RTT.

CONCLUSION

Our study offers an enriched data set for clinical investigations and treatment of fine and gross motor issues in RTT. A detailed understanding of genotype-phenotype relationships of movement disorders allows for more robust genetic counseling for families but can also assist healthcare professionals in terms of monitoring disease progression in RTT. The synthesis also showed that environmental enrichment would be beneficial for improving some aspects of movement disorders. The cerebellum, basal ganglia, alongside dysregulation of the cortico-basal ganglia-thalamo-cortical loop, are likely anatomical targets. A review of treatments for movement disorders also helped to provide recommendations for treating and managing movement disorders in patients with RTT.

Scoping review of symptoms in children with rare, progressive, life-threatening disorders

BACKGROUND

Q3 conditions are progressive, metabolic, neurological or chromosomal childhood conditions without a cure. Children with these conditions face an unknown lifespan as well as unstable and uncomfortable symptoms. Clinicians and other healthcare professionals are challenged by a lack of evidence for symptom management for these conditions.

AIMS

In this scoping review, we systematically identified and mapped the existing literature on symptom management for children with Q3 conditions. We focused on the most common and distressing symptoms, namely alertness, behavioural problems, bowel incontinence, breathing difficulties, constipation, feeding difficulties, sleep disturbance, temperature regulation, tone and motor problems and urinary incontinence. For children with complex health conditions, good symptom management is pertinent to ensure the highest possible quality of life.

METHODS

Scoping review. Electronic database searches in Ovid MEDLINE, Embase and CINAHL and a comprehensive grey literature search.

RESULTS

We included 292 studies in our final synthesis. The most commonly reported conditions in the studies were Rett syndrome (n=69), followed by Cornelia de Lange syndrome (n=25) and tuberous sclerosis (n=16). Tone and motor problems were the most commonly investigated symptom (n=141), followed by behavioural problems (n=82) and sleep disturbance (n=62).

CONCLUSION

The evidence for symptom management in Q3 conditions is concentrated around a few conditions, and these studies may not be applicable to other conditions. The evidence is dispersed in the literature and difficult to access, which further challenges healthcare providers. More research needs to be done in these conditions to provide high-quality evidence for the care of these children.

Hand stereotypies: Lessons from the Rett Syndrome Natural History Study

OBJECTIVE

To characterize hand stereotypies (HS) in a large cohort of participants with Rett syndrome (RTT).

METHODS

Data from 1,123 girls and women enrolled in the RTT Natural History Study were gathered. Standard tests for continuous and categorical variables were used at baseline. For longitudinal data, we used repeated-measures linear and logistic regression models and nonparametric tests.

RESULTS

HS were reported in 922 participants with classic RTT (100%), 73 with atypical severe RTT (97.3%), 74 with atypical mild RTT (96.1%), and 17 females with MECP2 mutations without RTT (34.7%). Individuals with RTT who had classic presentation or severe MECP2 mutations had higher frequency and earlier onset of HS. Heterogeneity of HS types was confirmed, but variety decreased over time. At baseline, almost half of the participants with RTT had hand mouthing, which like clapping/tapping, decreased over time. These 2 HS types were more frequently reported than wringing/washing. Increased HS severity (prevalence and frequency) was associated with worsened measures of hand function. Number and type of HS were not related to hand function. Overall clinical severity was worse with decreased hand function but only weakly related to any HS characteristic. While hand function decreased over time, prevalence and frequency of HS remained relatively unchanged and high.

CONCLUSIONS

Nearly all individuals with RTT have severe and multiple types of HS, with mouthing and clapping/tapping decreasing over time. Interaction between HS frequency and hand function is complex. Understanding the natural history of HS in RTT could assist in clinical care and evaluation of new interventions.

Rett syndrome: Teenagers' and young adults' activities, usage of time and responses during an ordinary week - a diary study

Background: Little is known about the everyday life of individuals with Rett syndrome.Aim/Objective: To describe ten participants' (teenagers/young adults) activities during a period of seven days, the time-use, where and with whom the activities were performed and the participants' responses in the form of visible/audible reactions during activities.Material and method: A time-geographic self-administered diary was filled in by 63 informants (parents/support staff) and analysed using the software, DAILY LIFE 2011.Results/Findings: The most frequently reported activities were hygiene/toilet, moving around indoors, eating and getting dressed. Most time was spent in sleeping, daily care, medical health care and travel/transportation. Little time remained for receptive activities, daytime rest, physical, social/creative, communication, school/daily work and domestic chore activities, especially for the young adults. Most time was spent with staff, thereafter with families and the least time was spent with friends. The most reported response was "interested", and "opposed" was the least reported.Conclusions: Daily and medical health care activities were time consuming. Improved communication between all parties may increase participation and well-being and provide solutions for handling unpleasant activities and sedentary time.Significance: A more varied range of activities may improve the everyday life for individuals with Rett syndrome.