Electroencephalographic Correlates of Clinical Severity in the Natural history study of RTT and Related Disorders.

OBJECTIVE: This study was undertaken to characterize quantitative electroencephalographic (EEG) features in participants from the Natural history study of RTT and Related Disorders and to assess the potential for these features to act as objective measures of cortical function for Rett syndrome (RTT). METHODS: EEG amplitude and power features were derived from the resting EEG of 60 females with RTT (median age = 10.7 years) and 26 neurotypical females (median age = 10.6 years). Analyses focus on group differences and within the RTT group, associations between the EEG parameters and clinical severity. For a subset of participants (n = 20), follow-up data were available for assessing the reproducibility of the results and the stability in the parameters over 1 year. RESULTS: Compared to neurotypical participants, participants with RTT had greater amplitude variability and greater low-frequency activity as reflected by greater delta power, more negative 1/f slope, and lower theta/delta, alpha/delta, beta/delta, alpha/theta, and beta/theta ratios. Greater delta power, more negative 1/f slope, and lower power ratios were associated with greater severity. Analyses of year 1 data replicated the associations between 1/f slope and power ratios and clinical severity and demonstrated good within-subject consistency in these measures. INTERPRETATION: Overall, group comparisons reflected a greater predominance of lower versus higher frequency activity in participants with RTT, which is consistent with prior clinical interpretations of resting EEG in this population. The observed associations between the EEG power measures and clinical assessments and the repeatability of these measures underscore the potential for EEG to provide an objective measure of cortical function and clinical severity for RTT. ANN NEUROL 2024.

De novo GRIN variants in M3 helix associated with neurological disorders control channel gating of NMDA receptor.

N-methyl-D-aspartate receptors (NMDARs) are members of the glutamate receptor family and participate in excitatory postsynaptic transmission throughout the central nervous system. Genetic variants in GRIN genes encoding NMDAR subunits are associated with a spectrum of neurological disorders. The M3 transmembrane helices of the NMDAR couple directly to the agonist-binding domains and form a helical bundle crossing in the closed receptors that occludes the pore. The M3 functions as a transduction element whose conformational change couples ligand binding to opening of an ion conducting pore. In this study, we report the functional consequences of 48 de novo missense variants in GRIN1, GRIN2A, and GRIN2B that alter residues in the M3 transmembrane helix. These de novo variants were identified in children with neurological and neuropsychiatric disorders including epilepsy, developmental delay, intellectual disability, hypotonia and attention deficit hyperactivity disorder. All 48 variants in M3 for which comprehensive testing was completed produce a gain-of-function (28/48) compared to loss-of-function (9/48); 11 variants had an indeterminant phenotype. This supports the idea that a key structural feature of the M3 gate exists to stabilize the closed state so that agonist binding can drive channel opening. Given that most M3 variants enhance channel gating, we assessed the potency of FDA-approved NMDAR channel blockers on these variant receptors. These data provide new insight into the structure-function relationship of the NMDAR gate, and suggest that variants within the M3 transmembrane helix produce a gain-of-function.

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.

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.

CDKL5 deficiency disorder and other infantile-onset genetic epilepsies.

AIM: To differentiate phenotypic features of individuals with CDKL5 deficiency disorder (CDD) from those of individuals with other infantile-onset epilepsies. METHOD: We performed a retrospective cohort study and ascertained individuals with CDD and comparison individuals with infantile-onset epilepsy who had epilepsy gene panel testing. We reviewed records, updated variant classifications, and compared phenotypic features. Wilcoxon rank-sum tests and χ2 or Fisher's exact tests were performed for between-cohort comparisons. RESULTS: We identified 137 individuals with CDD (110 females, 80.3%; median age at last follow-up 3 year 11 months) and 313 individuals with infantile-onset epilepsies (156 females, 49.8%; median age at last follow-up 5 years 2 months; 35% with genetic diagnosis). Features reported significantly more frequently in the CDD group than in the comparison cohort included developmental and epileptic encephalopathy (81% vs 66%), treatment-resistant epilepsy (95% vs 71%), sequential seizures (46% vs 6%), epileptic spasms (66% vs 42%, with hypsarrhythmia in 30% vs 48%), regression (52% vs 29%), evolution to Lennox-Gastaut syndrome (23% vs 5%), diffuse hypotonia (72% vs 36%), stereotypies (69% vs 11%), paroxysmal movement disorders (29% vs 17%), cerebral visual impairment (94% vs 28%), and failure to thrive (38% vs 22%). INTERPRETATION: CDD, compared with other suspected or confirmed genetic epilepsies presenting in the first year of life, is more often characterized by a combination of treatment-resistant epilepsy, developmental and epileptic encephalopathy, sequential seizures, spasms without hypsarrhythmia, diffuse hypotonia, paroxysmal movement disorders, cerebral visual impairment, and failure to thrive. Defining core phenotypic characteristics will improve precision diagnosis and treatment.

Clinical and functional consequences of GRIA variants in patients with neurological diseases.

AMPA receptors are members of the glutamate receptor family and mediate a fast component of excitatory synaptic transmission at virtually all central synapses. Thus, their functional characteristics are a critical determinant of brain function. We evaluate intolerance of each GRIA gene to genetic variation using 3DMTR and report here the functional consequences of 52 missense variants in GRIA1-4 identified in patients with various neurological disorders. These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression. We predict that these functional and localization changes will have important consequences for circuit function, and therefore likely contribute to the patients' clinical phenotype. We evaluated the sensitivity of variant receptors to AMPAR-selective modulators including FDA-approved drugs to explore potential targeted therapeutic options.

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.

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.

Classification of missense variants in the N-methyl-d-aspartate receptor GRIN gene family as gain- or loss-of-function.

Advances in sequencing technology have generated a large amount of genetic data from patients with neurological conditions. These data have provided diagnosis of many rare diseases, including a number of pathogenic de novo missense variants in GRIN genes encoding N-methyl-d-aspartate receptors (NMDARs). To understand the ramifications for neurons and brain circuits affected by rare patient variants, functional analysis of the variant receptor is necessary in model systems. For NMDARs, this functional analysis needs to assess multiple properties in order to understand how variants could impact receptor function in neurons. One can then use these data to determine whether the overall actions will increase or decrease NMDAR-mediated charge transfer. Here, we describe an analytical and comprehensive framework by which to categorize GRIN variants as either gain-of-function (GoF) or loss-of-function (LoF) and apply this approach to GRIN2B variants identified in patients and the general population. This framework draws on results from six different assays that assess the impact of the variant on NMDAR sensitivity to agonists and endogenous modulators, trafficking to the plasma membrane, response time course and channel open probability. We propose to integrate data from multiple in vitro assays to arrive at a variant classification, and suggest threshold levels that guide confidence. The data supporting GoF and LoF determination are essential to assessing pathogenicity and patient stratification for clinical trials as personalized pharmacological and genetic agents that can enhance or reduce receptor function are advanced. This approach to functional variant classification can generalize to other disorders associated with missense variants.

Expression of hyperpolarization-activated current (Ih) in zonally defined vestibular calyx terminals of the crista.

Calyx terminals make afferent synapses with type I hair cells in vestibular epithelia and express diverse ionic conductances that influence action potential generation and discharge regularity in vestibular afferent neurons. Here we investigated the expression of hyperpolarization-activated current (Ih) in calyx terminals in central and peripheral zones of mature gerbil crista slices, using whole cell patch-clamp recordings. Slowly activating Ih was present in >80% calyces tested in both zones. Peak Ih and half-activation voltages were not significantly different; however, Ih activated with a faster time course in peripheral compared with central zone calyces. Calyx Ih in both zones was blocked by 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride (ZD7288; 100 µM), and the resting membrane potential became more hyperpolarized. In the presence of dibutyryl-cAMP (dB-cAMP), peak Ih was increased, activation kinetics became faster, and the voltage of half-activation was more depolarized compared with control calyces. In current clamp, calyces from both zones showed three different categories of firing: spontaneous firing, phasic firing where a single action potential was evoked after a hyperpolarizing pulse, or a single evoked action potential followed by membrane potential oscillations. In the absence of Ih, the latency to peak of the action potential increased; Ih produces a small depolarizing current that facilitates firing by driving the membrane potential closer to threshold. Immunostaining showed the expression of HCN2 subunits in calyx terminals. We conclude that Ih is found in calyx terminals across the crista and could influence conventional and novel forms of synaptic transmission at the type I hair cell-calyx synapse.NEW & NOTEWORTHY Calyx afferent terminals make synapses with vestibular hair cells and express diverse conductances that impact action potential firing in vestibular primary afferents. Conventional and nonconventional synaptic transmission modes are influenced by hyperpolarization-activated current (Ih), but regional differences were previously unexplored. We show that Ih is present in both central and peripheral calyces of the mammalian crista. Ih produces a small depolarizing resting current that facilitates firing by driving the membrane potential closer to threshold.

Comparison of evoked potentials across four related developmental encephalopathies.

BACKGROUND: Developing biomarkers is a priority for drug development for all conditions, but vital in the rare neurodevelopmental disorders where sensitive outcome measures are lacking. We have previously demonstrated the feasibility and tracking of evoked potentials to disease severity in Rett syndrome and CDKL5 deficiency disorder. The aim of the current study is to characterize evoked potentials in two related developmental encephalopathies, MECP2 duplication syndrome and FOXG1 syndrome, and compare across all four groups to better understand the potential of these measures to serve as biomarkers of clinical severity for the developmental encephalopathies. METHODS: Visual and auditory evoked potentials were acquired from participants with MECP2 duplication syndrome and FOXG1 syndrome across five sites of the Rett Syndrome and Rett-Related Disorders Natural History Study. A group of age-matched individuals (mean = 7.8 years; range = 1-17) with Rett syndrome, CDKL5 deficiency disorder, and typically-developing participants served as a comparison group. The analysis focused on group-level differences as well as associations between the evoked potentials and measures of clinical severity from the Natural History Study. RESULTS: As reported previously, group-level comparisons revealed attenuated visual evoked potentials (VEPs) in participants with Rett syndrome (n = 43) and CDKL5 deficiency disorder (n = 16) compared to typically-developing participants. VEP amplitude was also attenuated in participants with MECP2 duplication syndrome (n = 15) compared to the typically-developing group. VEP amplitude correlated with clinical severity for Rett syndrome and FOXG1 syndrome (n = 5). Auditory evoked potential (AEP) amplitude did not differ between groups, but AEP latency was prolonged in individuals with MECP2 duplication syndrome (n = 14) and FOXG1 syndrome (n = 6) compared to individuals with Rett syndrome (n = 51) and CDKL5 deficiency disorder (n = 14). AEP amplitude correlated with severity in Rett syndrome and CDKL5 deficiency disorder. AEP latency correlated with severity in CDKL5 deficiency disorder, MECP2 duplication syndrome, and FOXG1 syndrome. CONCLUSIONS: There are consistent abnormalities in the evoked potentials in four developmental encephalopathies some of which correlate with clinical severity. While there are consistent changes amongst these four disorders, there are also condition specific findings that need to be further refined and validated. Overall, these results provide a foundation for further refinement of these measures for use in future clinical trials for these conditions.

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.

The CaV1.2 G406R mutation decreases synaptic inhibition and alters L-type Ca2+ channel-dependent LTP at hippocampal synapses in a mouse model of Timothy Syndrome.

Genetic alterations in autism spectrum disorders (ASD) frequently disrupt balance between synaptic excitation and inhibition and alter plasticity in the hippocampal CA1 region. Individuals with Timothy Syndrome (TS), a genetic disorder caused by CaV1.2 L-type Ca2+ channel (LTCC) gain-of function mutations, such as G406R, exhibit social deficits, repetitive behaviors, and cognitive impairments characteristic of ASD that are phenocopied in TS2-neo mice expressing G406R. Here, we characterized hippocampal CA1 synaptic function in male TS2-neo mice and found basal excitatory transmission was slightly increased and inhibitory transmission strongly decreased. We also found distinct impacts on two LTCC-dependent forms of long-term potentiation (LTP) synaptic plasticity that were not readily consistent with LTCC gain-of-function. LTP induced by high-frequency stimulation (HFS) was strongly impaired in TS2-neo mice, suggesting decreased LTCC function. Yet, CaV1.2 expression, basal phosphorylation, and current density were similar for WT and TS2-neo. However, this HFS-LTP also required GABAA receptor activity, and thus may be impaired in TS2-neo due to decreased inhibitory transmission. In contrast, LTP induced in WT mice by prolonged theta-train (PTT) stimulation in the presence of a ß-adrenergic receptor agonist to increase CaV1.2 phosphorylation was partially induced in TS2-neo mice by PTT stimulation alone, consistent with increased LTCC function. Overall, our findings provide insights regarding how altered CaV1.2 channel function disrupts basal transmission and plasticity that could be relevant for neurobehavioral alterations in ASD.

Electrophysiological biomarkers of brain function in CDKL5 deficiency disorder.

CDKL5 deficiency disorder is a debilitating developmental and epileptic encephalopathy for which no targeted treatment exists. A number of promising therapeutics are under development for CDKL5 deficiency disorder but a lack of validated biomarkers of brain function and clinical severity may limit the ability to objectively assess the efficacy of new treatments as they become available. To address this need, the current study quantified electrophysiological measures in individuals with CDKL5 deficiency disorder and the association between these parameters and clinical severity. Visual and auditory evoked potentials, as well as resting EEG, were acquired across 5 clinical sites from 26 individuals with CDKL5 deficiency disorder. Evoked potential and quantitative EEG features were calculated and compared with typically developing individuals in an age- and sex-matched cohort. Baseline and Year 1 data, when available, were analysed and the repeatability of the results was tested. Two clinician-completed severity scales were used for evaluating the clinical relevance of the electrophysiological parameters. Group-level comparisons revealed reduced visual evoked potential amplitude in CDKL5 deficiency disorder individuals versus typically developing individuals. There were no group differences in the latency of the visual evoked potentials or in the latency or amplitude of the auditory evoked potentials. Within the CDKL5 deficiency disorder group, auditory evoked potential amplitude correlated with disease severity at baseline as well as Year 1. Multiple quantitative EEG features differed between CDKL5 deficiency disorder and typically developing participants, including amplitude standard deviation, 1/f slope and global delta, theta, alpha and beta power. Several quantitative EEG features correlated with clinical severity, including amplitude skewness, theta/delta ratio and alpha/delta ratio. The theta/delta ratio was the overall strongest predictor of severity and also among the most repeatable qEEG measures from baseline to Year 1. Together, the present findings point to the utility of evoked potentials and quantitative EEG parameters as objective measures of brain function and disease severity in future clinical trials for CDKL5 deficiency disorder. The results also underscore the utility of the current methods, which could be similarly applied to the identification and validation of electrophysiological biomarkers of brain function for other developmental encephalopathies.

Anxiety-like behavior and anxiolytic treatment in the Rett syndrome natural history study.

BACKGROUND: Rett syndrome (RTT) is a neurodevelopmental disorder most often related to a pathogenic variant in the X-linked MECP2 gene. Internalizing behaviors appear to be common, but standard methods of diagnosing anxiety are not readily applied in this population which typically has cognitive impairment and limited expressive language. This study aims to describe the frequency of anxiety-like behavior and anxiolytic treatments along with associated clinical features in individuals with RTT. METHODS: Parental reports and medication logs provided data from 1380 females with RTT participating in two iterations of the multicenter U.S. RTT Natural History Study (RNHS) from 2006 to 2019. RESULTS: Most participants with RTT (77.5%) had at least occasional anxious or nervous behavior. Anxiety was reported to be the most troublesome concern for 2.6%, and within the top 3 concerns for 10.0%, of participants in the second iteration. Parents directly reported treatment for anxious or nervous behavior in 16.6% of participants in the second iteration with most reporting good control of the behavior (71.6%). In the medication logs of both RNHS iterations, the indication of anxiety was listed for a similar number of participants (15% and 14.5%, respectively). Increased use of anxiolytics and selective serotonin reuptake inhibitors (SSRIs) was related to more frequent anxiety-like behaviors (P < 0.001), older age (P < 0.001), and mild MECP2 variants (P = 0.002). CONCLUSION: Anxiety-like behavior is frequent at all ages and is a significant parental concern in RTT. Older individuals and those with mild MECP2 variants are more likely to be treated with medications. Better diagnosis and treatment of anxiety in RTT should be a goal of both future studies and clinical care. TRIAL REGISTRATION: NCT00299312 and NCT02738281.

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 Behaviour 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.

Current neurologic treatment and emerging therapies in CDKL5 deficiency disorder.

BACKGROUND: CDKL5 deficiency disorder (CDD) is associated with refractory infantile onset epilepsy, global developmental delay, and variable features that include sleep, behavioral disturbances, and movement disorders. Current treatment is primarily symptom-based and informed by experience in caring for this population. METHODS: We describe medication and non-medication approaches to treatment of epilepsy and additional key neurologic symptoms (sleep disturbances, behavioral issues, movement disorders, and swallowing dysfunction) in a cohort of 177 individuals meeting criteria for CDD, 154 evaluated at 4 CDKL5 Centers of Excellence in the USA and 40 identified through the NIH Natural History Study of Rett and Related Disorders. RESULTS: The four most frequently prescribed anti-seizure medications were broad spectrum, prescribed in over 50% of individuals. While the goal was not to ascertain efficacy, we obtained data from 86 individuals regarding response to treatment, with 2-week response achieved in 14-48% and sustained 3-month response in 5-36%, of those with known response. Additional treatments for seizures included cannabis derivatives, tried in over one-third of individuals, and clinical trial medications. In combination with pharmacological treatment, 50% of individuals were treated with ketogenic diet for attempted seizure control. Surgical approaches included vagus nerve stimulators, functional hemispherectomy, and corpus callosotomy, but numbers were too limited to assess response. Nearly one-third of individuals received pharmacologic treatment for sleep disturbances, 13% for behavioral dysregulation and movement disorders, and 43% had gastrostomy tubes. CONCLUSIONS: Treatment for neurologic features of CDD is currently symptom-based and empiric rather than CDD-specific, though clinical trials for CDD are emerging. Epilepsy in this population is highly refractory, and no specific anti-seizure medication was associated with improved seizure control. Ketogenic diet is commonly used in patients with CDD. While behavioral interventions are commonly instituted, information on the use of medications for sleep, behavioral management, and movement disorders is sparse and would benefit from further characterization and optimization of treatment approaches. The heterogeneity in treatment approaches highlights the need for systematic review and guidelines for CDD. Additional disease-specific and disease-modifying treatments are in development.

Cerebral visual impairment in CDKL5 deficiency disorder: vision as an outcome measure.

AIM: To characterize the neuro-ophthalmological phenotype of cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) and assess visual acuity as a reproducible, quantitative outcome measure. METHOD: We retrospectively analyzed clinical data from patients with CDD. Complete neuro-ophthalmological assessments, including visual acuity, were evaluated. RESULTS: Of 26 patients (22 females, four males; median age 4y, interquartile range 2y 1mo-7y 10mo), cerebral visual impairment (CVI), defined as visual dysfunction in the absence of ocular or anterior visual pathway abnormalities, was diagnosed in all those over 2 years of age. Ophthalmological examinations revealed nystagmus in 10 patients and strabismus in 24 patients. Visual acuity was measured in 24 patients, by preferential looking in all and by sweep visual evoked potential in 13. Visual acuities were lower than age expectations and demonstrated improvement in the first 3 years. Adjusting for age and sex, average preferential looking visual acuity after 2 years of age was higher in patients with intact mobility than in those who were non-mobile. INTERPRETATION: CVI was observed in patients with CDD. Visual acuity improved over time and correlated with mobility. Visual acuity, as a quantifiable measure of visual function, should be considered as an outcome measure in pre-clinical and clinical studies for CDD. What this paper adds Cerebral visual impairment is highly prevalent in cyclin-dependent kinase-like 5 deficiency disorder (CDD). Visual acuity is a measurable quantitative outcome measure in CDD. Visual acuity in CDD correlates with gross motor ability.

Sodium channel blockers for the treatment of epilepsy in CDKL5 deficiency disorder: Findings from a multicenter cohort.

OBJECTIVE: This study was aimed to analyze the effectiveness of sodium channel blockers (SCBs) in CDKL5 deficiency disorder (CDD)-related epilepsy. METHODS: A retrospective, observational study was performed, including patients with CDD diagnosis evaluated between 2016 and 2019 at three tertiary Epilepsy Centers. Demographic, electroclinical and genetic features, as well as ASM treatments and their outcomes were analyzed, with special focus on SCBs. RESULTS: Twenty-one patients evaluated at three tertiary Epilepsy Centers were included, of which 19 presented with epilepsy (90.5%); all had pathogenic mutations of CDKL5. Six patients (31.6%) were classified as SCB responders (more than 50% reduction), four being currently seizure free (mean seizure-free period of 8 years). Most frequent SCB drugs were oxcarbazepine (OXC), carbamazepine (CBZ), and lacosamide (LCM). None of them presented relevant adverse events. In contrast, three patients showed seizure aggravation in the non-responder group. When comparing both groups, responders had statistically significant younger age at SCB treatment and epilepsy onset, higher proportion of focal epileptiform activity and less frequent history of West syndrome. CONCLUSIONS: The results of this study indicate that treatment with SCBs might be effective and safe in a subset of patients with CDD-related epilepsy.