Improving Treatment Trial Outcomes for Rett Syndrome: The Development of Rett-specific Anchors for the Clinical Global Impression Scale

Intravenous esketamine in pediatric Rett syndrome: An open-label, early phase 1 pilot study

Rett syndrome (RTT) is a severe neurodevelopmental disorder. N-Methyl-d-aspartate receptor (NMDAR) antagonism has shown therapeutic potential in preclinical RTT models. We performed a pilot study to explore whether intravenous esketamine, an NMDAR antagonist, alleviates the symptoms of pediatric RTT. This was a prospective, single-arm, single-site, open-label, early phase 1 pilot study. Three girls with classic RTT aged 5-10 years were enrolled. Esketamine was intravenously administrated once per week for 5 weeks. The efficacy assessments included RTT-related questionnaires and video electroencephalograms (VEEGs). Prespecified adverse events (AEs) were monitored using clinical observations and standard laboratory tests. The treatment with intravenous esketamine was generally well tolerated and safe, with some patients experiencing mild AEs, including self-alleviating nausea, vomiting, and irritability. Three participants showed minimal improvements in their Clinical Global Impression Scale-Improvement, Rett Syndrome Behavior Questionnaire, and Revised Motor Behaviors Assessment Scale scores. However, individual differences were observed in the efficacy measures. VEEGs indicated gradual increases in posterior dominant rhythm peak frequency throughout the intervention. This pilot study highlights the potential of esketamine treatment for improving behavioral dysfunction in patients with RTT. Investigating the appropriate dosage form of esketamine may enhance its beneficial effects in RTT with fewer undesirable features.

Psychometric Assessment of the Rett Syndrome Caregiver Assessment of Symptom Severity (RCASS)

Rett syndrome is a severe neurodevelopmental disorder that affects about 1 in 10,000 females. Clinical trials of disease modifying therapies are on the rise, but there are few psychometrically sound caregiver-reported outcome measures available to assess treatment benefit. We report on a new caregiver-reported outcome measure, the Rett Caregiver Assessment of Symptom Severity (RCASS). Using data from the Rett Natural History Study (n = 649), we examined the factor structure, using both exploratory and confirmatory factor analysis, and the reliability and validity of the RCASS. The four-factor model had the best overall fit, which covered movement, communication, behavior, and Rett-specific symptoms. The RCASS had moderate internal consistency. Strong face validity was found with age and mutation type, and convergent validity was established with other similar measures, including the Revised Motor-Behavior Assessment Scale, Clinical Severity Scale, Clinical Global Impression Scale, and the Child Health Questionnaire. These data provide initial evidence that the RCASS is a viable caregiver-outcome measure for use in clinical trials in Rett syndrome. Future work to assess sensitivity to change and other measures of reliability, such as test-retest and inter-rater agreement, are needed.

Development and refinement of the Clinical Global Impression of Improvement for Non-seizure Symptoms measure in Dravet syndrome and Lennox-Gastaut syndrome

BACKGROUND

Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS) are rare, severe, childhood-onset developmental and epileptic encephalopathies characterized by treatment-resistant epilepsy and varying intellectual disability levels. Clinical outcome assessments (COAs) describe how patients feel, function, or survive, thus providing valuable information on a therapy's efficacy and impact. Individuals with DS or LGS are heterogeneous, and many have limited verbal abilities and intellectual disability. Existing epilepsy-specific COA measures are unsuitable for DS and LGS clinical trials as many items demonstrate floor effects in these populations. As patients often cannot self-report symptoms, caregiver feedback on the measures' relevance and understandability is critical when developing COAs to ensure their suitability for the intended population, and that caregivers can help clinicians complete the measures when necessary.

METHODOLOGY

We aimed to develop a novel clinician-reported outcomes measure, to be completed in consultation with caregivers at clinic visits, to assess non-seizure symptoms in individuals with DS or LGS using a Clinical Global Impression of Improvement (CGI-I) approach: the CGI-I Non-seizure Symptoms measure. A 13-item initial draft measure was reviewed by experts in a three-round Delphi panel to confirm each item's relevance and refine descriptions, reduce overlap, and limit respondent burden.

RESULTS

Following panel review, three items reached consensus (≥70% agreement of no revision required) and were included in the final measure: communication, alertness, and disruptive behaviors. To ensure caregivers can help clinicians complete the measure, and to establish levels of change in each item domain considered meaningful from their perspective, the three-item measure was cognitively debriefed with caregivers of individuals with DS or LGS. Caregivers showed that each item was understandable by describing their child using the descriptions provided in the measure and reported that items were relevant or important to assess in DS or LGS. Most caregivers reported that even a minimal change to their child's condition in each domain would be meaningful to them and their child.

CONCLUSIONS

This CGI-I Non-seizure Symptoms measure represents relevant non-seizure outcomes considered important to individuals with DS or LGS and their families. The systematic development and refinement approach presented here supports its use in DS and LGS clinical trials.

Prenatal gene editing for neurodevelopmental diseases: Ethical considerations

Neurodevelopmental diseases (NDDs) are notoriously difficult to treat because clinical symptoms stem from developmental processes that begin before birth. Prenatal gene editing could fill the treatment gap for NDDs by targeting and permanently correcting the genetic variants that underlie these pathogenic developmental processes. At the same time, there is a risk of unintended edits to the fetus or the pregnant person that could result in serious adverse consequences that are difficult, if not impossible, to undo. This raises ethical concerns that make the development of prenatal gene editing especially challenging. To date, there are no frameworks for considering the steps necessary for an ethical path forward for prenatal gene editing specifically. The 60-year history of in utero therapy has included the development of frameworks for other therapies that can provide starting points for addressing the unique issues of prenatal gene editing. We identified 12 themes from 17 ethical frameworks, literature, consensus statements, and government reports on prenatal interventions that could set precedents for prenatal gene editing interventions. In considering these alongside current criteria for postnatal gene therapies for NDDs, we discuss a path forward for prenatal gene editing interventions of NDDs.

A randomized, placebo-controlled, cross-over trial of ketamine in Rett syndrome

BACKGROUND

Preclinical studies and anecdotal case reports support the potential therapeutic benefit of low-dose oral ketamine as a treatment of clinical symptoms in Rett syndrome (RTT); however, no controlled studies have been conducted in RTT to evaluate safety, tolerability and efficacy.

DESIGN

This was a sequentially initiated, dose-escalating cohort, placebo-controlled, double blind, randomized sequence, cross-over study of oral ketamine in 6-12-year-old girls with RTT to evaluate short-term safety and tolerability and explore efficacy.

METHODS

Participants were randomized to either five days treatment with oral ketamine or matched placebo, followed by a nine-day wash-out period and then crossed-over to the opposite treatment. Ketamine was dosed twice daily at 0.75 mg/kg/dose (Cohort 1) or 1.5 mg/kg/dose (Cohort 2). An independent safety monitoring committee evaluated safety and approved proceeding to the next dose cohort. Caregivers, participants, outcome assessors, and study staff except pharmacists were blinded to allocation. The primary endpoint was safety and tolerability. Exploratory efficacy endpoints included change in clinician- and caregiver-rated measures of RTT features, brain activity on electroencephalography, and wearable biosensors to measure respiration, heart rate, sleep, and activity.

RESULTS

Twenty-three participants enrolled (11 in Cohort 1, 12 in Cohort 2) from 3/12/2019-11/22/2021. One participant was excluded from analysis due to not meeting inclusion criteria on blinded review prior to analysis. One participant was withdrawn from the study due to an adverse event (vomiting) after the first dose of ketamine. Although planned for four dose cohorts, the trial was stopped after Cohort 2 due to enrollment challenges associated with the COVID-19 pandemic. Ketamine was safe and tolerated in both cohorts, with 1 related treatment emergent adverse event of vomiting. No difference was observed in efficacy between ketamine and placebo. Electroencephalography showed the expected increase in high frequency power with ketamine.

CONCLUSIONS

Short-term, low-dose oral ketamine was safe and well tolerated in girls with RTT. No clinical efficacy of ketamine in treating symptoms of RTT was observed with 5 days of treatment, despite electroencephalography evidence of ketamine target engagement during the first dose. Further studies are needed to evaluate safety and efficacy of higher dose and longer exposure to ketamine in RTT.

TRIAL REGISTRATION

Registered at clinicaltrials.gov NCT03633058.

International workshop: what is needed to ensure outcome measures for Rett syndrome are fit-for-purpose for clinical trials? June 7, 2023, Nashville, USA

INTRODUCTION

The clinical, research and advocacy communities for Rett syndrome are striving to achieve clinical trial readiness, including having fit-for-purpose clinical outcome assessments. This study aimed to (1) describe psychometric properties of clinical outcome assessment for Rett syndrome and (2) identify what is needed to ensure that fit-for-purpose clinical outcome assessments are available for clinical trials.

METHODS

Clinical outcome assessments for the top 10 priority domains identified in the Voice of the Patient Report for Rett syndrome were compiled and available psychometric data were extracted. The clinical outcome assessments measured clinical severity, functional abilities, comorbidities and quality of life, and electrophysiological biomarkers. An international and multidisciplinary panel of 29 experts with clinical, research, psychometric, biostatistical, industry and lived experience was identified through International Rett Syndrome Foundation networks, to discuss validation of the clinical outcome assessments, gaps and next steps, during a workshop and in a follow-up questionnaire. The identified gaps and limitations were coded using inductive content analysis.

RESULTS

Variable validation profiles across 26 clinical outcome assessments of clinical severity, functional abilities, and comorbidities were discussed. Reliability, validity, and responsiveness profiles were mostly incomplete; there were limited content validation data, particularly parent-informed relevance, comprehensiveness and comprehensibility of items; and no data on meaningful change or cross-cultural validity. The panel identified needs for standardised administration protocols and systematic validation programmes.

CONCLUSION

A pipeline of collaborative clinical outcome assessment development and validation research in Rett syndrome can now be designed, aiming to have fit-for-purpose measures that can evaluate meaningful change, to serve future clinical trials and clinical practice.

Rett Syndrome: The Emerging Landscape of Treatment Strategies

Rett syndrome (RTT) has enjoyed remarkable progress in achieving specific therapies. RTT, a unique neurodevelopmental disorder first described in 1966, progressed slowly until the landmark paper of Hagberg and colleagues in 1983. Thereafter, rapid advances were achieved including the development of specific diagnostic criteria and the active search for a genetic etiology, resulting 16 years later in identification of variants in the methyl-CpG-binding protein (MECP2) gene located at Xq28. Shortly thereafter, the NIH Office of Rare Diseases funded the RTT Natural History Study (NHS) in 2003, initiating the acquisition of natural history data on clinical features from a large population of individuals with RTT. This information was essential for advancement of clinical trials to provide specific therapies for this disorder. In the process, the International Rett Syndrome Association (IRSA) was formed (now the International Rett Syndrome Foundation-IRSF), which participated directly in encouraging and expanding enrollment in the NHS and, subsequently, in developing the SCOUT program to facilitate testing of potential therapeutic agents in a mouse model of RTT. The overall objective was to review clinical characteristics developed from the NHS and to discuss the status of specific therapies for this progressive neurodevelopmental disorder. The NHS study provided critical information on RTT: growth, anthropometrics, longevity, key comorbidities including epilepsy, breath abnormalities, gastroesophageal dysfunction, scoliosis and other orthopedic issues, puberty, behavior and anxiety, and progressive motor deterioration including the appearance of parkinsonian features. Phenotype-genotype correlations were noted including the role of X chromosome inactivation. Development of clinical severity and quality of life measures also proved critical for subsequent clinical trials. Further, development of biochemical and neurophysiologic biomarkers offered further endpoints for clinical trials. Initial clinical trials prior to the NHS were ineffective, but advances resulting from the NHS and other studies worldwide promoted significant interest from pharmaceutical firms resulting in several clinical trials. While some of these have been unrewarding such as sarizotan, others have been quite promising including the approval of trofinetide by the FDA in 2023 as the first agent available for specific treatment of RTT. Blarcamesine has been trialed in phase 3 trials, 14 agents have been studied in phase 2 trials, and 7 agents are being evaluated in preclinical/translational studies. A landmark study in 2007 by Guy et al. demonstrated that activation of a normal MECP2 gene in a null mouse model resulted in significant improvement. Gene replacement therapy has advanced through translational studies to two current phase 1/2 clinical trials (Taysha102 and Neurogene-401). Additional genetic therapies are also under study including gene editing, RNA editing, and X-chromosome reactivation. Taken together, progress in understanding and treating RTT over the past 40 years has been remarkable. This suggests that further advances can be expected.

Associations between genotype, phenotype and behaviours measured by the Rett syndrome behaviour questionnaire in Rett syndrome

INTRODUCTION

Rett syndrome (RTT) is a rare neurodevelopmental disorder with developmental impairments, comorbidities, and abnormal behaviours such as hand stereotypies and emotional features. The Rett Syndrome Behaviour Questionnaire (RSBQ) was developed to describe the behavioural and emotional features of RTT. Little is known how RSBQ scores are associated with genetic and clinical characteristics in RTT. This study investigated relationships between genotype, age, walking, hand function, sleep, and RSBQ total and subscale scores in RTT.

METHODS

This is a cross-sectional analysis of data collected in the Australian Rett Syndrome Database and the International Rett Syndrome Phenotype Database. Parent caregivers completed the RSBQ and Sleep Disturbance Scale for Children [subscales for disorders of initiating and maintaining sleep (DIMS), disorders of excessive somnolence (DOES)], and provided information on age, variant type, functional abilities (mobility, hand function), seizure frequency and gastrointestinal problems. Associations between the RSBQ scores and the independent variables were modelled using linear regression.

RESULTS

Data were available for 365 individuals with RTT [median (range) age 17.8 (2.9-51.9) years, 2 males]. Compared to adults, 2- to 12-year-old children had higher mean Total, Night-time Behaviour and Fear/Anxiety scores. Compared to individuals with a C-terminal deletion, individuals with the p.Arg255* variant had higher mean Total and Night-time Behaviours scores, whereas the p.Arg294* variant had higher mean Mood scores. Individuals with intermediate mobility and hand function abilities had a higher mean Total score. Total RSBQ and subscale scores were similar across categories for seizures, constipation, and reflux, but were higher with abnormal DIMS and abnormal DOES scores.

CONCLUSION

Except for associations with sleep, the RSBQ measures the behavioural phenotype rather than clinical severity in RTT, as traditionally conceptualised in terms of functional abilities and comorbidities. When designing clinical trials, the RSBQ needs to be complemented by other outcome measures to assess specific core functions and associated comorbidities in RTT.

Trofinetide for the treatment of Rett syndrome: Long-term safety and efficacy results of the 32-month, open-label LILAC-2 study

BACKGROUND

Trofinetide was approved for the treatment of Rett syndrome (RTT) in patients aged ≥2 years based on the results of the 12-week, randomized, phase 3 LAVENDER study. In LILAC, a 40-week, open-label extension study of LAVENDER, trofinetide continued to improve the symptoms of RTT, with a similar safety profile as LAVENDER. Here, we report long-term safety and efficacy results of LILAC-2, a 32-month, open-label extension study.

METHODS

Females aged 5-22 years who completed LILAC were eligible to enter LILAC-2. Safety and tolerability were assessed with the incidence of adverse events (AEs). Efficacy was assessed with Rett Syndrome Behaviour Questionnaire (RSBQ) and Clinical Global Impression-Improvement (CGI-I) scores. Caregiver interviews explored the patient's experience with RTT and the efficacy of trofinetide during study participation.

FINDINGS

In total, 77 participants were enrolled in LILAC-2. The most common AEs were diarrhea (53.2%), COVID-19 (27.3%), and vomiting (19.5%). The mean (standard error [SE]) change in RSBQ score from LAVENDER baseline to week 104 of LILAC-2 was -11.8 (2.45). The mean (SE) CGI-I score from LILAC baseline to week 12 of LILAC-2 was 3.1 (0.10). Most caregivers (96%; n = 24/25) were satisfied or very satisfied with the benefits of trofinetide.

CONCLUSIONS

Long-term treatment with trofinetide continued to improve RTT symptoms, without new safety concerns. Caregivers reported satisfaction with trofinetide related to improvements that were meaningful for their child and themselves.

FUNDING

The study was supported by Acadia Pharmaceuticals (San Diego, CA, USA). This study was registered at ClinicalTrials.gov: NCT04776746.

Rett syndrome diagnostic odyssey: Limitations of NextGen sequencing

Typical (or classic) Rett syndrome (RTT) is an X-linked neurodevelopmental disorder characterized by a period of regression, partial or complete loss of purposeful hand movements, and acquired speech, impaired gait, and stereotyped hand movements. In over 95% of typical RTT, a pathogenic variant is found in the methyl-CPG binding protein 2 gene (MECP2). Here, we describe a young woman with clinically diagnosed typical RTT syndrome who lacked a genetic diagnosis despite 20 years of investigation and multiple rounds of sequencing the MECP2 gene. Recently, additional genetic testing using next-generation sequencing was completed, which revealed a partial insertion of the BCL11A gene within exon 4 of MECP2, resulting in a small deletion in MECP2, causing likely disruption of MeCP2 function due to a frameshift. This case demonstrates the ever-changing limitations of genetic testing, as well as the importance of continual pursuit of a diagnosis as technologies improve and are more widely utilized.

Trofinetide for the treatment of Rett syndrome: Results from the open-label extension LILAC study

BACKGROUND

Trofinetide was approved for the treatment of Rett syndrome based on the results of the phase 3, randomized, placebo-controlled, 12-week LAVENDER study. Rett syndrome is a chronic disorder requiring long-term treatment. We report the efficacy and safety results of LILAC, a 40-week, open-label extension study of LAVENDER.

METHODS

Females with Rett syndrome aged 5-21 years received open-label treatment with trofinetide for 40 weeks. The primary endpoint was long-term safety of trofinetide; secondary endpoints included the change from baseline at week 40 in the Rett Syndrome Behaviour Questionnaire score and the Clinical Global Impression-Improvement score at week 40.

FINDINGS

Overall, 154 participants were enrolled and treated with trofinetide in LILAC. The most common adverse events in LILAC were diarrhea (74.7%), vomiting (28.6%), and COVID-19 (11.0%). Diarrhea was the most common adverse event leading to treatment withdrawal (21.4%). The Rett Syndrome Behaviour Questionnaire mean score (standard error) improvement from the LAVENDER baseline to week 40 in LILAC was -7.3 (1.62) and -7.0 (1.61) for participants treated with trofinetide and placebo in LAVENDER, respectively. Mean Clinical Global Impression-Improvement scores (standard error) at week 40 rated from the LILAC baseline were 3.1 (0.11) and 3.2 (0.14) for participants treated with trofinetide and placebo in LAVENDER, respectively.

CONCLUSIONS

Treatment with trofinetide for ≤40 weeks continued to improve symptoms of Rett syndrome. Trofinetide had a similar safety profile in LILAC as in LAVENDER.

FUNDING

The study was supported by Acadia Pharmaceuticals Inc. (San Diego, CA, USA). This trial was registered at ClinicalTrials.gov (NCT04279314).

Using Precision Medicine to Disentangle Genotype-Phenotype Relationships in Twins with Rett Syndrome: A Case Report

Rett syndrome (RTT) is a paediatric neurodevelopmental disorder spanning four developmental stages. This multi-system disorder offers a unique window to explore genotype-phenotype relationships in a disease model. However, genetic prognosticators of RTT have limited clinical value due to the disorder's heterogeneity on multiple levels. This case report used a precision medicine approach to better understand the clinical phenotype of RTT twins with an identical pathogenic MECP2 mutation and discordant neurodevelopmental profiles. Targeted genotyping, objective physiological monitoring of heart rate variability (HRV) parameters, and clinical severity were assessed in a RTT twin pair (5 years 7 months old) with an identical pathogenic MECP2 mutation. Longitudinal assessment of autonomic HRV parameters was conducted using the Empatica E4 wristband device, and clinical severity was assessed using the RTT-anchored Clinical Global Impression Scale (RTT-CGI) and the Multi-System Profile of Symptoms Scale (MPSS). Genotype data revealed impaired BDNF function for twin A when compared to twin B. Twin A also had poorer autonomic health than twin B, as indicated by lower autonomic metrics (autonomic inflexibility). Hospitalisation, RTT-CGI-S, and MPSS subscale scores were used as measures of clinical severity, and these were worse in twin A. Treatment using buspirone shifted twin A from an inflexible to a flexible autonomic profile. This was mirrored in the MPSS scores, which showed a reduction in autonomic and cardiac symptoms following buspirone treatment. Our findings showed that a combination of a co-occurring rs6265 BDNF polymorphism, and worse autonomic and clinical profiles led to a poorer prognosis for twin A compared to twin B. Buspirone was able to shift a rigid autonomic profile to a more flexible one for twin A and thereby prevent cardiac and autonomic symptoms from worsening. The clinical profile for twin A represents a departure from the disorder trajectory typically observed in RTT and underscores the importance of wider genotype profiling and longitudinal objective physiological monitoring alongside measures of clinical symptoms and severity when assessing genotype-phenotype relationships in RTT patients with identical pathogenic mutations. A precision medicine approach that assesses genetic and physiological risk factors can be extended to other neurodevelopmental disorders to monitor risk when genotype-phenotype relationships are not so obvious.

Is trofinetide a future treatment for Rett syndrome? A comprehensive systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Rett syndrome (RTT) is a rare, life-threatening, genetic neurodevelopmental disorder. Treatment in RTT encounters many challenges. Trofinetide, a modified amino-terminal tripeptide of insulin-like growth factor 1, has demonstrated clinically promising results in RTT. In this study, trofinetide efficacy and safety in RTT are systematically reviewed and meta-analyzed.

METHODS

A systematic search of five electronic databases was conducted until January 2024. Review Manager 5.4 software was used for the analysis. The analysis was based on a weighted mean difference and standard error with a confidence interval (CI) of 95%, and a statistically significant P-value was considered if it was < 0.05. The study was registered on PROSPERO with registration number CRD42024499849. Quality of evidence was assessed using GRADE.

RESULTS

Three randomized controlled trials (RCTs) with 276 patients were included in the analysis. Trofinetide improved both caregiver outcomes and clinical scales by improving the Rett Syndrome Behavior Questionnaire (RSBQ) (mean difference (MD): - 3.46 points, 95% CI: - 5.63 to - 1.27, P = 0.0002) and Clinical Global Impression Scale-Improvement (CGI-I) (MD: - 0.35, 95% CI: - 0.51 to - 0.18, P < 0.0001), respectively. However, trofinetide neither improved the Caregiver Top 3 Concerns Visual Analog Scale nor the Rett Motor Behavioral Assessment. Regarding safety, trofinetide was significantly associated with vomiting compared to placebo (odds ratio (OR): 3.17, 95% CI: 1.57 to 6.43, P = 0.001). After solving heterogeneity, results showed a statistically significant incidence of diarrhea in the trofinetide (200 mg) group compared to placebo (OR: 18.51, 95% CI: 9.30 to 36.84, P ≤ 0.00001).

CONCLUSIONS

Trofinetide demonstrated statistically significant improvements in CGI-I and RSBQ in pediatrics and adult patients with Rett. Side effects are limited to vomiting and diarrhea. Although diarrhea yielded an insignificant result in our analysis, it emerged as a cause for treatment discontinuation in the participating trials, and a statistically significant risk for diarrhea emerged when excluding the study using a lower dose of the drug, hence causing heterogeneity, in the meta-analysis. Given the diverse genetic landscape of RTT, future RCTs investigating correlations between RTT genotype and phenotypic improvements by trofinetide will be beneficial. RCTs encompassing male patients with larger and longer cohorts are recommended.

Co-Occurring Methylenetetrahydrofolate Reductase (MTHFR) rs1801133 and rs1801131 Genotypes as Associative Genetic Modifiers of Clinical Severity in Rett Syndrome

AIM

Remethylation disorders such as 5,10-methylenetetrahydrofolate reductase (MTHFR) deficiency reduce the remethylation of homocysteine to methionine. The resulting hyperhomocysteinemia can lead to serious neurological consequences and multisystem toxicity. The role of MTHFR genotypes has not been investigated in patients with Rett Syndrome (RTT). In this study, we sought to assess the impact of co-occurring MTHFR genotypes on symptom profiles in RTT.

METHOD

Using pharmacogenomic (PGx) testing, the MTHFR genetic polymorphisms rs1801133 (c.665C>T mutation) and rs1801131 (c.1286A>C mutation) were determined in 65 patients (18.7 years ± 12.1 [mean ± standard deviation]) with RTT as part of routine clinical care within the Centre for Interventional Paediatric Psychopharmacology (CIPP) Rett Centre, a National and Specialist Child and Adolescent Mental Health Service (CAMHS) in the UK. The clinical severity of patients was assessed using the RTT-anchored Clinical Global Impression Scale (RTT-CGI).

RESULTS

The clinical severity symptom distribution varied between the homozygous and heterozygous MTHFR rs1801133 and rs1801131 genotypes. Those with the homozygous genotype had a narrower spread of severity scores across several domains (language and communication, ambulation, hand-use and eye contact clinical domains). Patients with the homozygous genotype had statistically significantly greater CGI-Severity scores than individuals with a non-homozygous MTHFR genotype (Z = -2.44, p = 0.015). When comparing the ratings of moderately impaired (4), markedly impaired (5), severely impaired (6) and extremely impaired (7), individuals with the homozygous MTHFR genotype were more impaired than those with the non-homozygous MTHFR genotype (Z = -2.06, p = 0.039). There was no statistically significant difference in the number of prescribed anti-epileptic drugs between the genotypes.

CONCLUSIONS

Our findings show that in those with a pathogenic RTT genetic variant, co-occurring homozygotic MTHFR rs1801133 and rs1801131 polymorphisms may act as associative genetic modifiers of clinical severity in a subset of patients. Profiling of rs1801133 and rs1801131 in RTT may therefore be useful, especially for high-risk patients who may be at the most risk from symptom deterioration.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

BACKGROUND

In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary.

METHODS

AEPs were recorded to simple 100 Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures.

RESULTS

Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident.

CONCLUSIONS

To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Exposure-Response Efficacy Modeling to Support Trofinetide Dosing in Individuals with Rett Syndrome

INTRODUCTION

Trofinetide was recently approved for the treatment of Rett syndrome (RTT) on the basis of the efficacy and safety findings of the phase 3 LAVENDER study, which used a body weight-based dosing regimen. Exposure-response (E-R) efficacy modeling was used to characterize relationships between trofinetide exposure measures (maximum drug concentration and area under the concentration-time curve for the dosing interval of 0-12 h [AUC0-12]) and efficacy endpoints in RTT clinical studies to support the trofinetide dosing regimen.

METHODS

Efficacy endpoints were modeled using trofinetide exposure measures predicted from the population pharmacokinetic model and Bayesian estimates. The analysis population for each E-R model comprised individuals receiving placebo or trofinetide who had available trofinetide exposure measures. Efficacy endpoints were scores from the Rett Syndrome Behaviour Questionnaire (RSBQ), the Clinical Global Impression-Improvement, the Communication and Symbolic Behavior Scales Developmental Profile™ Infant-Toddler Checklist (CSBS-DP-IT) Social Composite, and the Rett Syndrome Clinician Rating of Ability to Communicate Choices (RTT-COMC).

RESULTS

Higher trofinetide exposure was associated with improvements in RSBQ, CSBS-DP-IT Social Composite, and RTT-COMC scores. Assuming target trofinetide AUC0-12 values of 800-1200 μg·h/mL, the reductions in RSBQ total scores at week 12 were approximately five- to seven-fold greater with trofinetide (range 3.55-4.94) versus placebo (0.76). Significant E-R relationships were also found for the CSBS-DP-IT Social Composite and RTT-COMC scores.

CONCLUSION

E-R efficacy modeling demonstrated significant relationships between trofinetide exposure and RSBQ, CSBS-DP-IT Social Composite, and RTT-COMC scores. Trofinetide is efficacious within the target exposure range, supporting the approved dosing regimen for trofinetide.

TRIAL REGISTRATION

NCT01703533, NCT02715115, NCT04181723.

Trofinetide Treatment Demonstrates a Benefit Over Placebo for the Ability to Communicate in Rett Syndrome

BACKGROUND

Trofinetide was approved by the US Food and Drug Administration for the treatment of Rett syndrome (RTT) in March 2023. Benefiting the ability to communicate in RTT is often identified as the most important caregiver goal for new therapies. This analysis reports the communication-related end points from the phase 3 LAVENDER study of trofinetide in RTT.

METHODS

Females with RTT, aged five to 20 years, were randomized 1:1 to trofinetide or placebo for 12 weeks. Secondary efficacy end points related to communication were based on change from baseline to week 12 and included the caregiver-rated Communication and Symbolic Behavior Scales Developmental Profile™ Infant-Toddler Checklist (CSBS-DP-IT) Social Composite score (key secondary end point; scores ranged from 0 to 26 [higher scores indicated better communication]) and novel clinician rating scales (0 [normal] to 7 [severe impairment]) measuring the ability to communicate choices nonverbally (RTT-COMC) and verbally (RTT-VCOM).

RESULTS

Trofinetide demonstrated a statistically significant difference versus placebo for the CSBS-DP-IT Social Composite score (least squares mean [LSM] difference = 1.0; 95% confidence interval [CI], 0.3 to 1.7; P = 0.0064; Cohen's d effect size = 0.43) and a nominally significant difference for the RTT-COMC (LSM difference: -0.3; 95% CI, -0.6 to -0.0; P = 0.0257; Cohen's d effect size = 0.36). As expected, there was no difference for the RTT-VCOM.

CONCLUSIONS

Significant treatment benefit for trofinetide versus placebo was observed in scales measuring the ability to communicate. These scales may be appropriate for future clinical studies in RTT and other neurodevelopmental disorders.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

Background In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary. Methods AEPs were recorded to simple 100Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures. Results Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident. Conclusions To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

Background

In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary.

Methods

AEPs were recorded to simple 100Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures.

Results

Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident.

Conclusions

To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Development of trofinetide for the treatment of Rett syndrome: from bench to bedside

Rett syndrome (RTT) is rare neurodevelopmental disorder caused by mutations in the MECP2 gene that encodes methyl-CpG-binding protein 2 (MeCP2), a DNA-binding protein with roles in epigenetic regulation of gene expression. Functional loss of MeCP2 results in abnormal neuronal maturation and plasticity, characterized by loss of verbal communication and loss of fine and gross motor function, among others. Trofinetide, a synthetic analog of glycine-proline-glutamate, was approved by the US Food and Drug Administration for the treatment of RTT in adult and pediatric patients aged 2 years and older. Here, we present the development of trofinetide from bench research to clinical studies and emphasize how the collaboration between academia, the pharmaceutical industry, and patient advocacy led to the recent approval. The bench-to-bedside development of trofinetide underscores the value of collaboration between these groups in the development and approval of treatments for rare diseases.

An adapted clinical global Impression of improvement for use in Angelman syndrome: Validation analyses utilizing data from the NEPTUNE study

PURPOSE

Angelman Syndrome (AS) is a rare, severe neurogenetic disorder that causes symptoms such as intellectual disability and motor impairments and is typically diagnosed in early childhood. The complexity and heterogeneity of AS confound characterization of disease severity and pose unique challenges when determining an individual's response to treatment. There is therefore a substantial unmet need for rating scales specifically designed for complex conditions such as AS. To address this, the Clinical Global Impressions (CGI) scale, which has components for both symptom severity (CGI-S) and improvement (CGI-I) was specifically adapted to measure severity (CGI-S-AS) and improvement (CGI-I-AS) in AS.

METHODS

The modified CGI-S/I-AS was used in the NEPTUNE trial of gaboxadol for the treatment of AS. Here we report on the validation of the CGI-I-AS using data from NEPTUNE and discuss insights for its potential use in future trials.

RESULTS

Improvements in the CGI-I-AS rating tended to be consistent with changes on other relevant rating scales. Sleep-related symptoms were particularly well represented, while communication-related symptoms were not.

CONCLUSIONS

Our validation analysis of the CGI-I-AS demonstrates its usefulness along with possible areas of improvement. The CGI-I-AS is a potential tool for use in other trials of AS drug candidates, and the process for its development can serve as a road map for the development of assessment tools for other neuropsychiatric disorders with similar complexities and heterogeneity.

Top caregiver concerns in Rett syndrome and related disorders: data from the US natural history study

OBJECTIVE

Recent advances in the understanding of neurodevelopmental disorders such as Rett syndrome (RTT) have enabled the discovery of novel therapeutic approaches that require formal clinical evaluation of efficacy. Clinical trial success depends on outcome measures that assess clinical features that are most impactful for affected individuals. To determine the top concerns in RTT and RTT-related disorders we asked caregivers to list the top caregiver concerns to guide the development and selection of appropriate clinical trial outcome measures for these disorders.

METHODS

Caregivers of participants enrolled in the US Natural History Study of RTT and RTT-related disorders (n = 925) were asked to identify the top 3 concerning problems impacting the affected participant. We generated a weighted list of top caregiver concerns for each of the diagnostic categories and compared results between the disorders. Further, for classic RTT, caregiver concerns were analyzed by age, clinical severity, and common RTT-causing mutations in MECP2.

RESULTS

The top caregiver concerns for classic RTT were effective communication, seizures, walking/balance issues, lack of hand use, and constipation. The frequency of the top caregiver concerns for classic RTT varied by age, clinical severity, and specific mutations, consistent with known variation in the frequency of clinical features across these domains. Caregivers of participants with increased seizure severity often ranked seizures as the first concern, whereas caregivers of participants without active seizures often ranked hand use or communication as the top concern. Comparison across disorders found commonalities in the top caregiver concerns between classic RTT, atypical RTT, MECP2 duplication syndrome, CDKL5 deficiency disorder, and FOXG1 syndrome; however, distinct differences in caregiver concerns between these disorders are consistent with the relative prevalence and impact of specific clinical features.

CONCLUSION

The top caregiver concerns for individuals with RTT and RTT-related disorders reflect the impact of the primary clinical symptoms of these disorders. This work is critical in the development of meaningful therapies, as optimal therapy should address these concerns. Further, outcome measures to be utilized in clinical trials should assess these clinical issues identified as most concerning by caregivers.

A review of the Rett Syndrome Behaviour Questionnaire and its utilization in the assessment of symptoms associated with Rett syndrome

The Rett Syndrome Behaviour Questionnaire (RSBQ), which is completed by the caregiver, is one of the most widely used efficacy measures in clinical studies of Rett syndrome (RTT) due to its specificity to the core features of RTT. As healthcare providers participate in routine healthcare assessments of individuals with RTT in clinical practice, there is a need for these providers to understand the psychometric properties of the RSBQ and how it relates to the core clinical features of RTT. Here, we describe the characteristics of the RSBQ, review the literature on its validity and reliability as well as its performance in a phase 2 study and the recent phase 3 LAVENDER study. The RSBQ was first shown to discriminate RTT from other intellectual disorders with good inter-rater and test-retest reliability scores. It was subsequently validated as an appropriate instrument for measuring behavior in females with RTT and adopted as a clinical trial outcome. In LAVENDER, the FDA-approved drug trofinetide significantly improved the RSBQ total score over placebo in girls and women with RTT and change from baseline for all RSBQ subscores were directionally in favor of trofinetide. The change in RSBQ was aligned with the Clinical Global Impression-Improvement scale, suggesting that improvement in behavioral components may be related to overall clinical status. Given its validity and ubiquity in RTT clinical studies, it is important that the interplay of the domains and the psychometric profile of the RSBQ are understood.

Developing Angelman syndrome-specific clinician-reported and caregiver-reported measures to support holistic, patient-centered drug development

BACKGROUND

Angelman syndrome (AS) is a rare, heterogenous neurogenetic condition, which significantly impacts the lives of people with AS and their families. Valid and reliable measures reporting key symptoms and functional impairments of AS are required to support development of patient-centered therapies. We describe the development of clinician- and caregiver-reported, AS-specific Global Impression scales for incorporation into clinical trials. Best practice US Food and Drug Administration guidance for measure development was followed with input from expert clinicians, patient advocates, and caregivers during content generation and refinement.

RESULTS

Initial measurement domains for the Symptoms of AS-Clinician Global Impression (SAS-CGI) and the Caregiver-reported AS Scale (CASS) were identified from a conceptual disease model of AS symptoms and impacts, derived from interviews with caregivers and clinicians. Two rounds of cognitive debriefing (CD) interviews were performed; clinicians debriefed the SAS-CGI, with patient advocates and caregivers debriefing the CASS to ensure relevance and comprehension. Feedback was used to refine items and ensure wording was age-appropriate and captured AS-specific symptoms, as well as associated impacts and functional impairments. The SAS-CGI and CASS capture global assessments of seizures, sleep, maladaptive behaviors, expressive communication, fine and gross motor skills, cognition, and self-care, which were determined by clinicians, patient advocates, and caregivers to be the most challenging aspects of AS. Additionally, the measures include items for assessing overall AS symptoms and the meaningfulness of any change. In addition to ratings for severity, impact, and change, a notes field was included in the SAS-CGI to provide the rationale for the chosen rating. CD interviews confirmed the measures covered key concepts of AS from the perspective of clinicians and caregivers, and demonstrated that the measures' instructions, items, and response options were clear and appropriate. Interview feedback informed adjustments to the wording of the instructions and the items.

CONCLUSIONS

The SAS-CGI and CASS were designed to capture multiple AS symptoms, reflecting the heterogeneity and complexity of AS in children 1 to 12 years old. These clinical outcome assessments have been incorporated into AS clinical studies, which will allow for the evaluation of their psychometric properties and inform further refinements if needed.

Trofinetide for the treatment of Rett syndrome: a randomized phase 3 study

Rett syndrome is a rare, genetic neurodevelopmental disorder. Trofinetide is a synthetic analog of glycine-proline-glutamate, the N-terminal tripeptide of the insulin-like growth factor 1 protein, and has demonstrated clinical benefit in phase 2 studies in Rett syndrome. In this phase 3 study ( https://clinicaltrials.gov identifier NCT04181723 ), females with Rett syndrome received twice-daily oral trofinetide (n = 93) or placebo (n = 94) for 12 weeks. For the coprimary efficacy endpoints, least squares mean (LSM) change from baseline to week 12 in the Rett Syndrome Behaviour Questionnaire for trofinetide versus placebo was -4.9 versus -1.7 (P = 0.0175; Cohen's d effect size, 0.37), and LSM Clinical Global Impression-Improvement at week 12 was 3.5 versus 3.8 (P = 0.0030; effect size, 0.47). For the key secondary efficacy endpoint, LSM change from baseline to week 12 in the Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist Social Composite score was -0.1 versus -1.1 (P = 0.0064; effect size, 0.43). Common treatment-emergent adverse events included diarrhea (80.6% for trofinetide versus 19.1% for placebo), which was mostly mild to moderate in severity. Significant improvement for trofinetide compared with placebo was observed for the coprimary efficacy endpoints, suggesting that trofinetide provides benefit in treating the core symptoms of Rett syndrome.

Top Caregiver Concerns in Rett syndrome and related disorders: data from the US Natural History Study

Objective

Recent advances in the understanding of neurodevelopmental disorders such as Rett syndrome (RTT) has enabled development of novel therapeutic approaches that are currently undergoing clinical evaluation or are proposed to move into clinical development. Clinical trial success depends on outcome measures that assess clinical features that are most impactful for affected individuals. To determine the top concerns in RTT and RTT-related disorders we asked caregivers to list the top clinical concerns in order to gain information to guide the development and selection of outcome measures for future clinical trials.

Methods

Caregivers of participants enrolled in the US Natural History Study of RTT and related disorders were asked to identify the top 3 concerning problems impacting the affected participant. We generated a weighted list of top caregiver concerns for each of the diagnostic categories and compared results between the disorders. Further, for Classic RTT, caregiver concerns were analyzed by age, clinical severity, and common RTT-causing mutations in MECP2.

Results

The top caregiver concerns for Classic RTT were effective communication, seizures, walking/balance issues, lack of hand use, and constipation. The rank order of the frequency of the top caregiver concerns for Classic RTT varied by age, clinical severity, and specific mutations, consistent with known variation in the frequency of clinical features across these domains. The frequency of caregiver concern for seizures, hand use, and spoken language increased in relation to clinician assessed severity in these clinical domains, showing consistency between clinician assessments and caregiver concerns. Comparison across disorders found commonalities in the top caregiver concerns between Classic RTT, Atypical RTT, MECP2 Duplication Syndrome, CDKL5 Deficiency Disorder, and FOXG1 Syndrome; however, distinct differences in caregiver concerns between these disorders are consistent with the relative prevalence and impact of specific clinical features.

Conclusion

The top caregiver concerns for individuals with RTT and the RTT-related disorders reflect the impact of the primary clinical symptoms of these disorders. This work is critical in the development of meaningful therapies, as optimal therapy should address these concerns. Further, outcome measures to be utilized in clinical trials should assess these clinical issues identified as most concerning by caregivers.

A circuit-level biomarker of Rett syndrome based on ectopic phase-amplitude coupling during slow-wave-sleep

Rett syndrome (RTT) is a neurodevelopmental disorder characterized by loss of purposeful hand use and spoken language following an initial period of normal development. Although much is known about the genetic and molecular underpinnings of RTT, less is known about the circuit-level etiopathology. Coupling of oscillations during slow-wave-sleep (SWS) underlies important neurocognitive processes in adulthood, yet its emergence has yet to be described in early typical development (TD) or in RTT. We therefore addressed these unknowns by describing SWS cross-frequency coupling in both RTT and early TD using a retrospective study design. We found that in TD, phase-amplitude coupling (PAC) during SWS was dominated by coupling of slow-wave (0.5-2 Hz) phase to theta amplitude (5-8 Hz, "SW:T") as well as slow-wave to spindle-range (12-15 Hz, "SW:S"). Coupling exhibited characteristic vertex-prominent spatial topography, which emerged during an early developmental window. This topography failed to develop in patients with RTT due to persistent ectopic coupling. Furthermore, we found that subtypes of RTT exhibit distinct PAC topographic profiles, and that ectopic PAC correlates with clinical severity. These findings suggest that altered PAC dynamics and spatial organization during SWS may underlie the circuit-level pathophysiology of RTT and suggest that ectopic coupling may contribute to RTT pathogenesis.

Rett syndrome severity estimation with the BioStamp nPoint using interactions between heart rate variability and body movement

Rett syndrome, a rare genetic neurodevelopmental disorder in humans, does not have an effective cure. However, multiple therapies and medications exist to treat symptoms and improve patients' quality of life. As research continues to discover and evaluate new medications for Rett syndrome patients, there remains a lack of objective physiological and motor activity-based (physio-motor) biomarkers that enable the measurement of the effect of these medications on the change in patients' Rett syndrome severity. In our work, using a commercially available wearable chest patch, we recorded simultaneous electrocardiogram and three-axis acceleration from 20 patients suffering from Rett syndrome along with the corresponding Clinical Global Impression-Severity score, which measures the overall disease severity on a 7-point Likert scale. We derived physio-motor features from these recordings that captured heart rate variability, activity metrics, and the interactions between heart rate and activity. Further, we developed machine learning (ML) models to classify high-severity Rett patients from low-severity Rett patients using the derived physio-motor features. For the best-trained model, we obtained a pooled area under the receiver operating curve equal to 0.92 via a leave-one-out-patient cross-validation approach. Finally, we computed the feature popularity scores for all the trained ML models and identified physio-motor biomarkers for Rett syndrome.

The Rare Diseases Clinical Research Network: a model for clinical trial readiness

Background

The current road to developing treatments for rare diseases is often slow, expensive, and riddled with risk. Change is needed to improve the process, both in how we think about rare disease treatment development and the infrastructure we build to support ongoing science. The National Institutes of Health (NIH)-supported Rare Diseases Clinical Research Network (RDCRN) was established to advance the diagnosis, management, and treatment of rare diseases and to promote highly collaborative, multi-site, patient-centric, translational, and clinical research. The current iteration of the RDCRN intends to build upon and enhance successful approaches within the network while identifying innovative methods to fill gaps and address needs in the approach to the rare disease treatment development process through innovation, collaboration, and clinical trial readiness.

Objective

The objective of this paper is to provide an overview of the productivity and influence of the RDCRN since it was first established 20 years ago.

Design and methods

Using a suite of tools available to NIH staff that provides access to a comprehensive, curated, extensively linked data set of global grants, patents, publications, clinical trials, and FDA-approved drugs, a series of queries were executed that conducted bibliometric, co-author, and co-occurrence analysis.

Results

The results demonstrate that the entire RDCRN consortia and network has been highly productive since its inception. They have produced 2763 high-quality publications that have been cited more than 100,000 times, expanded international networks, and contributed scientifically to eight FDA-approved treatments for rare diseases.

Conclusion

The RDCRN program has successfully addressed some significant challenges while developing treatments for rare diseases. However, looking to the future and being agile in facing new challenges that arise as science progresses is important.

GENE TARGET: A framework for evaluating Mendelian neurodevelopmental disorders for gene therapy

Interest in gene-based therapies for neurodevelopmental disorders is increasing exponentially, driven by the rise in recognition of underlying genetic etiology, progress in genomic technology, and recent proof of concept in several disorders. The current prioritization of one genetic disorder over another for development of therapies is driven by competing interests of pharmaceutical companies, advocacy groups, and academic scientists. Although these are all valid perspectives, a consolidated framework will facilitate more efficient and rational gene therapy development. Here we outline features of Mendelian neurodevelopmental disorders that warrant consideration when determining suitability for gene therapy. These features fit into four broad domains: genetics, preclinical validation, clinical considerations, and ethics. We propose a simple mnemonic, GENE TARGET, to remember these features and illustrate how they could be scored using a preliminary scoring rubric. In this suggested rubric, for a given disorder, scores for each feature may be added up to a composite GENE TARGET suitability (GTS) score. In addition to proposing a systematic method to evaluate and compare disorders, our framework helps identify gaps in the translational pipeline for a given disorder, which can inform prioritization of future research efforts.

Development and Psychometric Properties of the Multi-System Profile of Symptoms Scale in Patients with Rett Syndrome

Background: Rett Syndrome (RTT) is a rare, neurodevelopmental disorder characterised by a range of problematic symptoms. There is yet to be a robust instrument to adequately capture the range of disease severity across the lifespan. In this study, we aimed to develop and assess the validity of an RTT-specific electronic Observer Reported Outcome (eObsRO), the Multi-System Profile of Symptoms Scale (MPSS). Methods: The study was conducted in two phases. Phase 1 consisted of a systematic literature review, focus groups, expert feedback, and a pilot test of the new scale. Modifications were made based on preliminary analysis and feedback collected in the pilot phase. Phase 2 consisted of the validation of the questionnaire based on two samples (Sample 1, n = 18; Sample 2, n = 106). Participants were all parents or caregivers of individuals with RTT. Results: The MPSS consists of 12 validated sub-scales (mental health problems, autonomic problems, cardiac problems, communication problems, problems in social behaviour, problems in engagement, gastrointestinal problems, problems in motor skills, neurological problems, orofacial problems, respiratory problems, and sleep problems), which explore symptom frequency in the past month and a supplement to the scale consisting of five sub-scales (sensory problems, immune dysfunction and infection, endocrine problems, skeletal problems, and dermatological problems), which is designed to capture symptom changes over a longer time period. The frequency of symptoms was rated on a 10-point slider scale, which then was automatically transformed into a 0 to 5 Likert score. All 12 sub-scales showed strong internal consistency (α ≥ 0.700) and good stability, ranging from 0.707 to 0.913. Pearson’s correlation showed a statistically significant (r = 0.649) correlation between the MPSS and the Rett Syndrome Behaviour Questionnaire (RSBQ) total score and significant correlations between sub-scales with items that were presented in both the MPSS and RSBQ. Conclusions: The MPSS is a psychometrically validated eObsRO using the HealthTrackerTM platform and has the potential to be used in clinical trials.

Outcome measurement instruments in Rett syndrome: A systematic review

OBJECTIVE

The aim of the study was to identify and characterize outcome measures for objective and subjective assessment in persons with Rett syndrome (RS).

METHODS

A systematic review was conducted consulting the EBSCO, Cochrane, Web of Science, Scielo, MEDLINE and PsycINFO databases for published studies describing the use of patient-reported outcome measures (PROMs) and other outcome measures in persons with RS. Validation studies and observational studies were included. The PROMs were first described, and then the measurement properties were evaluated using predefined criteria according to the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN). The outcome measures were then grouped according to the International Classification of Functioning, Disability and Health (ICF) to establish a relationship between outcome measures and ICF domains.

RESULTS

Twenty out of 2327 articles were appraised, and seventeen different outcome measures were identified and described. Ten outcome measures corresponded to evaluation questionnaires, while the remaining seven assessed functional outcomes: walking distance, physical activity level and ability to interact visually. A relation between these outcome measures that assess RS and the ICF allows understanding that most of the instruments (fifteen) include the assessment of activity limitations.

CONCLUSIONS

The findings of this study seem to be promising for their use by clinicians and researchers, although they have methodological limitations. The accuracy and quality of these individual outcome measures should continue to be assessed in an attempt to gather a consensus on the best tools used in RS.

Exploring the characteristics and most bothersome symptoms in MECP2 duplication syndrome to pave the path toward developing parent-oriented outcome measures

BACKGROUND

MECP2 Duplication Syndrome (MDS), resulting from the duplication of Xq28 region, including MECP2, is a rare disorder with a nascent understanding in clinical features and severity. Studies using antisense oligonucleotides revealed a broad phenotypic rescue in transgenic mice. With human clinical trials on the horizon, there is a need to develop clinical outcome measures for MDS.

METHODS

We surveyed caregivers of MDS individuals to explore the frequency and severity of MDS clinical features, and identify the most meaningful symptoms/domains that need to be included in the outcome measure scales.

RESULTS

A total of 101 responses were eligible for the survey. The top six most meaningful symptoms to caregivers in descending order included epilepsy, gross motor, fine motor, communication, infection, and constipation problems. Epilepsy was present in 58.4% of the subjects and 75% were drug-resistant, Furthermore, ~12% required intensive care unit (ICU) admission. Infections were present in 55% of the subjects, and one-fourth of them required ICU admission. Constipation was present in ~85% of the subjects and one-third required enemas/suppositories.

CONCLUSION

Our study is one of the largest cohorts conducted on MDS individuals characterizing the frequency and severity of MDS symptoms. Additionally, these study results will contribute to establishing a foundation to develop parent-reported outcomes in MDS.

Development of the Clinical Gestalt Assessment: a visual clinical global impression scale for Proteus syndrome

BACKGROUND

Clinical outcome assessments are important tools for measuring the natural history of disease and efficacy of an intervention. The heterogenous phenotype and difficult to quantity features of Proteus syndrome present challenges to measuring clinical outcomes. To address these, we designed a global clinical assessment for Proteus syndrome, a rare mosaic overgrowth disorder. The Clinical Gestalt Assessment (CGA) aims to evaluate change over time in this phenotypically diverse disorder.

RESULTS

We gathered paired serial photographs and radiographs obtained at 12-to-36-month intervals from our natural history study of Proteus syndrome. The chronologic order of each set was blinded and presented to clinicians familiar with overgrowth disorders. They were asked to determine the chronologic order and, based on that response, rate global clinical change using a seven-point scale (Much Worse, Worse, Minimally Worse, No Change, Minimally Improved, Improved, Much Improved). Following a pilot, we tested the inter-rater reliability of the CGA using eight cases rated by eight clinicians. Raters identified the correct chronologic order in 53 of 64 (83%) of responses. There was low inter-rater variance and poor to moderate reliability with an intraclass correlation coefficient of 0.46 (95% CI 0.24-0.75). The overall estimate of global change was Minimally Worse over time, which is an accurate reflection of the natural history of Proteus syndrome.

CONCLUSIONS

The CGA is a tool to evaluate clinical change over time in Proteus syndrome and may be a useful adjunct to measure clinical outcomes in prospective therapeutic trials.

Improving clinical trial readiness to accelerate development of new therapeutics for Rett syndrome

Rett syndrome is associated with severe functional impairments and many comorbidities, each in urgent need of treatments. Mutations in the MECP2 gene were identified as causing Rett syndrome in 1999. Over the past 20 years there has been an abundance of preclinical research with some studies leading to human clinical trials. Despite this, few viable therapeutic options have emerged from this investment of effort. Reasons for this lack of success as they relate both to preclinical research and the clinical trial landscape are discussed. Considering what needs to be done to promote further success in the field, we take a positive and constructive approach and introduce the concept of clinical trial readiness and its necessary ingredients for Rett syndrome. These include: listening to the needs of families; support from advocacy groups; optimising use of existing clinic infrastructures and available natural history data; and, finally, the validation of existing outcome measures and/or the development and validation of new measures. We conclude by reiterating the need for a collaborative and coordinated approach amongst the many different stakeholder groups and the need to engage in new types of trial design which could be much more efficient, less costly and much less burdensome on families.

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.

Content Validation of Clinician-Reported Items for a Severity Measure for CDKL5 Deficiency Disorder

CDKL5 deficiency disorder (CDD) results in early-onset seizures and severe developmental impairments. A CDD clinical severity assessment (CCSA) was previously developed with clinician and parent-report items to capture information on a range of domains. Consistent with US Food and Drug Administration (FDA) guidelines, content validation is the first step in evaluating the psychometric properties of an outcome measure. The aim of this study was to validate the content of the clinician-reported items in the CCSA (CCSA-Clinician). Eight neurologists leading the USA CDD Center of Excellence clinics were interviewed using the "think aloud" technique to critique 26 clinician-reported items. Common themes were aggregated, and a literature search of related assessments informed item modifications. The clinicians then participated in 2 consensus meetings to review themes and finalize the items. A consensus was achieved for the content of the CCSA-Clinician. Eight of the original items were omitted, 11 items were added, and the remaining 18 items were revised. The final 29 items were classified into 2 domains: functioning and neurologic impairments. This study enabled refinement of the CCSA-Clinician and provided evidence for its content validity. This preliminary validation is essential before field testing and further validation, in order to advance the instrument toward clinical trial readiness.

Clinician- and Patient-reported Endpoints in CNS Orphan Drug Clinical Trials: ISCTM Position Paper on Best Practices for Endpoint Selection, Validation, Training, and Standardization

OBJECTIVE

The International Society of CNS Clinical Trials Methodology (ISCTM) Working Group on Rare Disease/Orphan Drug Development is dedicated to improving and streamlining trials to best develop new treatments for rare diseases. The rarity of these disorders requires a drug development strategy that differs from those of nonrare conditions. Rare disease drug development programs are challenged with small sample sizes, heterogeneous clinical presentations, and few, if any, off-the-shelf endpoints. When disease-specific clinical endpoints exist, they might not be validated and are typically not well known or broadly used in clinical practice. This paper aims to provide an overview of the special issues surrounding endpoints in rare disease drug development, with guidance, practical applications, and discussion.

DISCUSSION

The paper covers regulatory considerations in endpoint selection; identification of relevant measurement domains; methods of quantifying clinical meaningfulness; incorporation of patient- and clinician-reported outcomes; considerations for global clinician- and patient-rated clinical assessments; cognition assessment challenges in rare diseases; translation considerations; training, standardization, and calibration of assessors; and endpoint quality assurance. Additionally, it provides guidance and resources for those involved in drug development for rare diseases.

CONCLUSION

In keeping with the mission of ISCTM and the rare disease/orphan drug development working group, this article is designed to encourage thoughtful consideration and provide insight and guidance to promote and further efforts in in central nervous system (CNS) rare disease drug development efforts.

Clinical Trial Design for Disease-Modifying Therapies for Genetic Epilepsies

Although trials with anti-seizure medications (ASMs) have not shown clear anti-epileptogenic or disease-modifying activity in humans to date, rapid advancements in genomic technology and emerging gene-mediated and gene replacement options offer hope for the successful development of disease-modifying therapies (DMTs) for genetic epilepsies. In fact, more than 26 potential DMTs are in various stages of preclinical and/or clinical development for genetic syndromes associated with epilepsy. The scope of disease-modification includes but is not limited to effects on the underlying pathophysiology, the condition's natural history, epilepsy severity, developmental achievement, function, behavior, sleep, and quality of life. While conventional regulatory clinical trials for epilepsy therapeutics have historically focused on seizure reduction, similarly designed trials may prove ill-equipped to identify these broader disease-modifying benefits. As we look forward to this pipeline of DMTs, focused consideration should be given to the challenges they pose to conventional clinical trial designs for epilepsy therapeutics. Just as DMTs promise to fundamentally alter how we approach the care of patients with genetic epilepsy syndromes, DMTs likewise challenge how we traditionally construct and measure the success of clinical trials. In the following, we briefly review the historical and preclinical frameworks for DMT development for genetic epilepsies and explore the many novel challenges posed for such trials, including the choice of suitable outcome measures, trial structure, timing and duration of treatment, feasible follow-up period, varying safety profile, and ethical concerns.

Emotional Behavioural and Autonomic Dysregulation (EBAD) in Rett Syndrome - EDA and HRV monitoring using wearable sensor technology

BACKGROUND

Rett syndrome (RTT) is a severe genetic neurodevelopmental disorder. Emotional, Behavioural and Autonomic Dysregulation (EBAD), is frequent in RTT and is associated with multiple impairments. There are major challenges in the clinical assessment of emotions, behaviours, and autonomic function in RTT patients that limit the management of symptoms.

METHODS

Web-based technology (HealthTracker™) to measure the phenotype, and non-invasive, wearable sensor technology to evaluate autonomic function through Electrodermal Activity (EDA) and Heart Rate Variability (HRV) in 10 RTT patients was used, and treatment response of EBAD symptoms was monitored after different pharmacological treatments.

RESULTS

and discussion: 4 patients received buspirone, 2 sertraline, 1 gabapentin and 3 were not started on medications. Buspirone normalized the EDA in 3 patients with associated improvement in EBAD, whilst another patient only improved marginally. Both patients treated with sertraline (including one with normal EDA) significantly improved symptomatically. The patients on unchanged regimens showed no change in symptoms and autonomic function. Within 24 h of our assessment, one patient required intensive inpatient care due to septicaemia - this patient had been on gabapentin and showed a sharp and sustained EDA increase without obvious worsening of emotional and behavioural symptoms. Unlike the EDA, the analyses of HRV metrics did not reveal patterns that were associated with clinical outcomes. Our findings suggest a reasonable association of EDA normalization and symptomatic improvement in RTT subjects with EBAD treated with buspirone and point out its potential application as a measure of dysautonomia in RTT. Very high and sustained EDA levels may be a biomarker for concurrent serious physical illness in RTT.

Development of an adapted Clinical Global Impression scale for use in Angelman syndrome

BACKGROUND

The Clinical Global Impression-Severity (CGI-S) and CGI-Improvement (CGI-I) scales are widely accepted tools that measure overall disease severity and change, synthesizing the clinician's impression of the global state of an individual. Frequently employed in clinical trials for neuropsychiatric disorders, the CGI scales are typically used in conjunction with disease-specific rating scales. When no disease-specific rating scale is available, the CGI scales can be adapted to reflect the specific symptom domains that are relevant to the disorder. Angelman syndrome (AS) is a rare, clinically heterogeneous condition for which there is no disease-specific rating scale. This paper describes efforts to develop standardized, adapted CGI scales specific to AS for use in clinical trials.

METHODS

In order to develop adapted CGI scales specific to AS, we (1) reviewed literature and interviewed caregivers and clinicians to determine the most impactful symptoms, (2) engaged expert panels to define and operationalize the symptom domains identified, (3) developed detailed rating anchors for each domain and for global severity and improvement ratings, (4) reviewed the anchors with expert clinicians and established minimally clinically meaningful change for each symptom domain, and (5) generated mock patient vignettes to test the reliability of the resulting scales and to standardize rater training. This systematic approach to developing, validating, and training raters on a standardized, adapted CGI scale specifically for AS is described herein.

RESULTS

The resulting CGI-S/I-AS scales capture six critical domains (behavior, gross and fine motor function, expressive and receptive communication, and sleep) defined by caregivers and expert clinicians as the most challenging for patients with AS and their families.

CONCLUSIONS

Rigorous training and careful calibration for clinicians will allow the CGI-S/-I-AS scales to be reliable in the context of randomized controlled trials. The CGI-S/-I-AS scales are being utilized in a Phase 3 trial of gaboxadol for the treatment of AS.

A Psychometric Evaluation of the Motor-Behavioral Assessment Scale for Use as an Outcome Measure in Rett Syndrome Clinical Trials

Rett syndrome (RTT) is a neurodevelopmental disorder that primarily affects females. Recent work indicates the potential for disease modifying therapies. However, there remains a need to develop outcome measures for use in clinical trials. Using data from a natural history study (n = 1,075), we examined the factor structure, internal consistency, and validity of the clinician-reported Motor Behavior Assessment scale (MBA). The analysis resulted in a five-factor model: (1) motor dysfunction, (2) functional skills, (3) social skills, (4) aberrant behavior, and (5) respiratory behaviors. Item Response Theory (IRT) analyses demonstrated that all items had acceptable discrimination. The revised MBA subscales showed a positive relationship with parent reported items, age, and a commonly used measure of clinical severity in RTT, and mutation type. Further work is needed to evaluate this measure longitudinally and to add items related to the RTT phenotype.

Associations Among Diurnal Salivary Cortisol Patterns, Medication Use, and Behavioral Phenotype Features in a Community Sample of Rett Syndrome

Rett syndrome (RTT) is a severe neurodevelopmental disorder resulting from mutations of the MECP2 gene. Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis and abnormal stress responses have been observed in animal models of RTT, but little is known about HPA axis function among individuals with RTT. Diurnal salivary cortisol patterns from 30 females with RTT were examined in relation to mutation type, medication use, and features of the RTT behavioral phenotype. Cortisol patterns were significantly related to mutation severity, anticonvulsant medication status, and bruxism (tooth grinding). This study provides preliminary support for the hypothesis that RTT may be at risk for outcomes associated with aberrant HPA axis function, and that this risk may be mediated by mutation type.

Pharmacological read-through of R294X Mecp2 in a novel mouse model of Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder primarily caused by mutations in Methyl-CpG-binding Protein 2 (MECP2). More than 35% of affected individuals have nonsense mutations in MECP2. For these individuals, nonsense suppression has been suggested as a possible therapeutic approach. To assess the viability of this strategy, we created and characterized a mouse model with the common p.R294X mutation introduced into the endogenous Mecp2 locus (Mecp2R294X). Mecp2R294X mice exhibit phenotypic abnormalities similar to those seen in complete null mouse models; however, these occur at a later time point consistent with the reduced phenotypic severity seen in affected individuals containing this specific mutation. The delayed onset of severe phenotypes is likely due to the presence of truncated MeCP2 in Mecp2R294X mice. Supplying the MECP2 transgene in Mecp2R294X mice rescued phenotypic abnormalities including early death and demonstrated that the presence of truncated MeCP2 in these mice does not interfere with wild-type MeCP2. In vitro treatment of a cell line derived from Mecp2R294X mice with the nonsense suppression agent G418 resulted in full-length MeCP2 protein production, demonstrating feasibility of this therapeutic approach. Intraperitoneal administration of G418 in Mecp2R294X mice was sufficient to elicit full-length MeCP2 protein expression in peripheral tissues. Finally, intracranial ventricular injection of G418 in Mecp2R294X mice induced expression of full-length MeCP2 protein in the mouse brain. These experiments demonstrate that translational read-through drugs are able to suppress the Mecp2 p.R294X mutation in vivo and provide a proof of concept for future preclinical studies of nonsense suppression agents in RTT.

Comparison of Core Features in Four Developmental Encephalopathies in the Rett Natural History Study

OBJECTIVE

Rett syndrome, CDKL5-deficiency disorder, FOXG1 disorder, and MECP2 duplication disorder are developmental encephalopathies with shared and distinct features. Although they are historically linked, no direct comparison has been performed. The first head-to-head comparison of clinical features in these conditions is presented.

METHODS

Comprehensive clinical information was collected from 793 individuals enrolled in the Rett and Rett-Related Disorders Natural History Study. Clinical features including clinical severity, regression, and seizures were cross-sectionally compared between diagnoses to test the hypothesis that these are 4 distinct disorders.

RESULTS

Distinct patterns of clinical severity, seizure onset age, and regression were present. Individuals with CDKL5-deficency disorder were the most severely affected and had the youngest age at seizure onset (2 months), whereas children with MECP2 duplication syndrome had the oldest median age at seizure onset (64 months) and lowest severity scores. Rett syndrome and FOGX1 were intermediate in both features. Smaller head circumference correlates with increased severity in all disorders and earlier age at seizure onset in MECP2 duplication syndrome. Developmental regression occurred in all Rett syndrome participants (median = 18 months) but only 23 to 34% of the other disorders. Seizure incidence prior to the baseline visit was highest for CDKL5 deficiency disorder (96.2%) and lowest for Rett syndrome (47.5%). Other clinical features including seizure types and frequency differed among groups.

INTERPRETATION

Although these developmental encephalopathies share many clinical features, clear differences in severity, regression, and seizures warrant considering them as unique disorders. These results will aid in the development of disease-specific severity scales, precise therapeutics, and future clinical trials. ANN NEUROL 2020;88:396-406.

Using generalizability theory to evaluate the comparative reliability of developmental measures in neurogenetic syndrome and low-risk populations

BACKGROUND

The lack of available measures that can reliably characterize early developmental skills in children with neurogenetic syndromes (NGS) poses a significant challenge for research on early development in these populations. Although syndrome-specific measures may sometimes be necessary, a more cost- and time-efficient solution would be to identify existing measures that are appropriate for use in special populations or optimize existing measures to be used in these groups. Reliability is an important metric of psychometric rigor to consider when auditing and optimizing assessment tools for NGS. In this study, we use Generalizability Theory, an extension of classical test theory, as a novel approach for more comprehensively characterizing the reliability of existing measures and making decisions about their use in the field of NGS research.

METHODS

We conducted generalizability analyses on a popular early social communication screener, the Communication and Symbolic Behavior Scales-Infant-Toddler Checklist (CSBS-ITC), collected on 172 children (41 Angelman syndrome, 30 Prader-Willi syndrome, 42 Williams syndrome, 59 low-risk controls).

RESULTS

Overall, the CSBS-ITC demonstrated at least adequate reliability in the NGS groups included in this study, particularly for the Prader-Willi and Williams syndrome groups. However, the sources of systematic error variance in the CSBS-ITC varied greatly between the low-risk control and NGS groups. Moreover, as unassessed in previous research, the CSBS-ITC demonstrated substantial differences in variance sources among the NGS groups. Reliability of CSBS-ITC scores was highest when averaging across all measurement points for a given child and was generally similar or better in the NGS groups compared to the low-risk control group.

CONCLUSIONS

Our findings suggest that the CSBS-ITC communicates different information about the reliability of stability versus change, in low-risk control and NGS samples, respectively, and that psychometric approaches like Generalizability Theory can provide more complete information about the reliability of existing measures and inform decisions about how measures are used in research on early development in NGS.

Severity Assessment in CDKL5 Deficiency Disorder

BACKGROUND

Pathologic mutations in cyclin-dependent kinase-like 5 cause CDKL5 deficiency disorder, a genetic syndrome associated with severe epilepsy and cognitive, motor, visual, and autonomic disturbances. This disorder is a relatively common genetic cause of early-life epilepsy. A specific severity assessment is lacking, required to monitor the clinical course and needed to define the natural history and for clinical trial readiness.

METHODS

A severity assessment was developed based on clinical and research experience from the International Foundation for CDKL5 Research Centers of Excellence consortium and the National Institutes of Health Rett and Rett-Related Disorders Natural History Study consortium. An initial draft severity assessment was presented and reviewed at the annual CDKL5 Forum meeting (Boston, 2017). Subsequently it was iterated through four cycles of a modified Delphi process by a group of clinicians, researchers, industry, patient advisory groups, and parents familiar with this disorder until consensus was achieved. The revised version of the severity assessment was presented for review, comment, and piloting to families at the International Foundation for CDKL5 Research-sponsored family meeting (Colorado, 2018). Final revisions were based on this additional input.

RESULTS

The final severity assessment comprised 51 items that comprehensively describe domains of epilepsy; motor; cognition, behavior, vision, and speech; and autonomic functions. Parental ratings of therapy effectiveness and child and family functioning are also included.

CONCLUSIONS

A severity assessment was rapidly developed with input from multiple stakeholders. Refinement through ongoing validation is required for future clinical trials. The consensus methods employed for the development of severity assessment may be applicable to similar rare disorders.

Double-blind, randomized, placebo-controlled study of trofinetide in pediatric Rett syndrome

OBJECTIVE

To determine safety, tolerability, and pharmacokinetics of trofinetide and evaluate its efficacy in female children/adolescents with Rett syndrome (RTT), a debilitating neurodevelopmental condition for which no pharmacotherapies directed at core features are available.

METHODS

This was a phase 2, multicenter, double-blind, placebo-controlled, parallel-group study, in which safety/tolerability, pharmacokinetics, and clinical response to trofinetide were characterized in 82 children/adolescents with RTT, aged 5 to 15 years. Sixty-two participants were randomized 1:1:1:1 to receive placebo twice a day (bid) for 14 days, followed by placebo, 50, 100, or 200 mg/kg bid of trofinetide for 42 days. Following blinded safety data review, 20 additional participants were randomized 1:1 to the 200 mg/kg or placebo bid groups. Safety assessments included adverse events, clinical laboratory tests, physical examinations, and concomitant medications. Clinician- and caregiver-based efficacy measurements assessed clinically relevant, phenotypic dimensions of impairment of RTT.

RESULTS

All dose levels were well tolerated and generally safe. Trofinetide at 200 mg/kg bid showed statistically significant and clinically relevant improvements relative to placebo on the Rett Syndrome Behaviour Questionnaire, RTT-Clinician Domain Specific Concerns-Visual Analog Scale, and Clinical Global Impression Scale-Improvement. Exploratory analyses suggested that observed changes correlated with trofinetide exposure.

CONCLUSION

These results, together with those from a previous adolescent/adult trial, indicate trofinetide's potential for treating core RTT symptoms and support further trials.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that for children/adolescents with RTT, trofinetide was safe, well-tolerated, and demonstrated improvement over placebo at 200 mg/kg bid in functionally important dimensions of RTT.

Potential identification of vitamin B6 responsiveness in autism spectrum disorder utilizing phenotype variables and machine learning methods

We investigated whether machine learning methods could potentially identify a subgroup of persons with autism spectrum disorder (ASD) who show vitamin B6 responsiveness by selected phenotype variables. We analyzed the existing data from our intervention study with 17 persons. First, we focused on signs and biomarkers that have been identified as candidates for vitamin B6 responsiveness indicators. Second, we conducted hypothesis testing among these selected variables and their combinations. Finally, we further investigated the results by conducting cluster analyses with two different algorithms, affinity propagation and k-medoids. Statistically significant variables for vitamin B6 responsiveness, including combination of hypersensitivity to sound and clumsiness, and plasma glutamine level, were included. As an a priori variable, the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS) scores was also included. The affinity propagation analysis showed good classification of three potential vitamin B6-responsive persons with ASD. The k-medoids analysis also showed good classification. To our knowledge, this is the first study to attempt to identify subgroup of persons with ASD who show specific treatment responsiveness using selected phenotype variables. We applied machine learning methods to further investigate these variables' ability to identify this subgroup of ASD, even when only a small sample size was available.

Key issues in Rett syndrome: emotional, behavioural and autonomic dysregulation (EBAD) - a target for clinical trials

Complex neurodevelopmental disorders need multi-disciplinary treatment approaches for optimal care. The clinical effectiveness of treatments is limited in patients with rare genetic syndromes with multisystem morbidity. Emotional and behavioural dysregulation is common across many neurodevelopmental disorders. It can manifest in children across multiple diagnostic groups, including those on the autism spectrum and in rare genetic syndromes such as Rett Syndrome (RTT). There is, however a remarkable scarcity in the literature on the impact of the autonomic component on emotional and behavioural regulation in these disorders, and on the longer-term outcomes on disorder burden.RTT is a debilitating and often life-threatening disorder involving multiple overlapping physiological systems. Autonomic dysregulation otherwise known as dysautonomia is a cardinal feature of RTT characterised by an imbalance between the sympathetic and parasympathetic arms of the autonomic nervous system. Unlocking the autonomic component of emotional and behavioural dysregulation would be central in reducing the impairment seen in patients with RTT. In this vein, Emotional, Behavioural and Autonomic Dysregulation (EBAD) would be a useful construct to target for treatment which could mitigate burden and improve the quality of life of patients.RTT can be considered as a congenital dysautonomia and because EBAD can give rise to impairments occurring in multiple overlapping physiological systems, understanding these physiological responses arising out of EBAD would be a critical part to consider when planning treatment strategies and improving clinical outcomes in these patients. Biometric guided pharmacological and bio-feedback therapy for the behavioural and emotional aspects of the disorder offers an attracting perspective to manage EBAD in these patients. This can also allow for the stratification of patients into clinical trials and could ultimately help streamline the patient care pathway for optimal outcomes.The objectives of this review are to emphasise the key issues relating to the management of EBAD in patients with RTT, appraise clinical trials done in RTT from the perspective of autonomic physiology and to discuss the potential of EBAD as a target for clinical trials.