RARE DISEASE
Rett syndrome
Rett syndrome
Rett syndrome
Drug discovery
37
drugs
With orphan designations
Overview
Rett syndrome is a rare X-linked neurodevelopmental disorder caused by MECP2 gene mutations, characterized by progressive loss of motor skills, communication abilities, and hand stereotypies after initial normal development (6-18 months). Hallmark features include seizures, breathing irregularities, scoliosis, and autonomic dysfunction. Diagnosis is clinical with genetic confirmation. While incurable, multidisciplinary care focuses on symptom management and quality of life optimization [1][11][16].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
1,213 drug discovery papers about Rett syndrome, with 5 first-in-class and 50 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
1,213 drug discovery papers about Rett syndrome, with 5 first-in-class and 50 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2026-09-30 | Fenfluramine in Rett syndrome: A multidimensional clinical study.
Rett syndrome (RTT) is a severe neurodevelopmental disorder frequently associated with drug-resistant epilepsy, autonomic dysfunction, respiratory abnormalities, sleep disturbances, and behavioral impairment. Fenfluramine has shown efficacy in developmental and epileptic encephalopathies and may provide broader therapeutic benefits through modulation of serotonergic and sigma-1 receptor pathways. We conducted a prospective, open-label, single-center study to evaluate the efficacy, safety, and tolerability of adjunctive fenfluramine in patients with classic RTT carrying pathogenic MECP2 variants. Clinical assessments were performed at baseline and after 3 and 6 months of treatment. Outcomes included seizure frequency; clinician-reported measures of RTT severity, including the Clinical Global Impression-Improvement (CGI-I) scale, Clinical Severity Scale (CSS), and Motor Behavior Assessment (MBA); caregiver-reported measures, including the Rett Syndrome Behavior Questionnaire (RSBQ), Sleep Disturbance Scale for Children (SDSC), the EQ-5D-5L quality of life scale; and neurophysiological measures using auditory evoked potentials. Eight patients with classic RTT and drug-resistant epilepsy were included. Median age was 12 years (range, 6-17 years), and the median number of previously failed antiseizure medications was 5 (range, 2-10). All patients achieved a >50% reduction in seizure frequency. Significant improvements were observed in clinician-reported outcomes, including CGI-I, CSS, and MBA scores, and in caregiver-reported behavioral symptoms assessed with the RSBQ at 3 and 6 months (-7 and -9, respectively). Sleep disturbances improved markedly, with normalization of SDSC scores in all patients by month 6. Respiratory dysfunction, including hyperventilation-related symptoms, improved during follow-up. Neurophysiological assessments showed improved attentional and auditory discrimination processing in a subset of patients. Adverse events occurred in 71% of patients, most commonly somnolence; no patient discontinued treatment because of tolerability issues. Fenfluramine was associated with clinically meaningful improvements across several symptom domains in patients with RTT, including seizures, respiratory dysfunction, behavior, sleep, and overall disease severity, with an acceptable safety profile. Further evaluation of fenfluramine as a potential multisymptomatic treatment strategy in RTT in prospective controlled studies is warranted. Rett syndrome is a rare genetic disorder with complex symptoms that affect many aspects of daily life. In this study, fenfluramine was associated with improvements in seizures and several other important symptoms, including behavior, sleep, breathing, and clinical severity. The treatment was generally well tolerated. These results support further studies to determine whether fenfluramine could become a treatment for multiple symptoms of Rett syndrome.
2026-09-10 | Rett syndrome: MECP2 biology, multisystem pathophysiology, and the evolving therapeutic landscape.
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder arising predominantly from de novo loss-of-function mutations in MECP2, affecting approximately 1 in 10,000 live female births. MECP2 is a dosage-sensitive epigenetic regulator acting through its methyl-CpG-binding (MBD) and transcriptional-repression (TRD) domains; isoform-specific expression and X-chromosome-inactivation mosaicism drive the wide phenotypic variability, with mutation type broadly correlating with severity. Although historically viewed as neuron-centric, RTT is a multisystem disorder: beyond psychomotor regression, stereotypic hand movements, gait apraxia, and loss of spoken language, MECP2 deficiency contributes to brainstem-mediated breathing dysrhythmia, QTc prolongation, enteric dysmotility, low bone density, and mitochondrial/metabolic deficits, amplified by glial-neuronal crosstalk. Preclinical models, MECP2 rodents, patient iPSC-derived neurons, and cerebral organoids, reveal synaptic and dendritic deficits that improve substantially when MECP2 is reactivated in these systems, indicating that MECP2-deficient neurons remain viable rather than degenerating; whether comparable improvement can be achieved in affected individuals is not yet established. The therapeutic landscape now spans multidisciplinary supportive care, the first approved pharmacotherapy trofinetide, AAV-mediated MECP2 gene replacement (now in pivotal trials, with an important gene-therapy safety signal), antisense oligonucleotides for dosage normalisation, and emerging metabolic agents; validated biomarkers and objective outcome measures remain a major unmet need. RTT is a multisystem monogenic disorder whose management is shifting from symptom control toward disease modification. Phenotypic rescue after MECP2 restoration in rodent models provides the rationale for this shift but does not establish that RTT is reversible in patients; progress now depends on validated biomarkers, dose-controlled disease-modifying therapies, long-term outcome data, and equitable global access. • More than 90-95% of classic Rett syndrome is caused by de novo loss-of-function mutations in MECP2, a dosage-sensitive epigenetic reader whose isoform distribution, residual function and X-chromosome-inactivation mosaicism together account for much of the phenotypic variability. • Reactivating MECP2 in symptomatic adult rodents substantially improves many disease features, establishing that MECP2-deficient neurons are functionally impaired rather than lost and providing the rationale for disease-modifying therapy. • This review integrates isoform-specific and non-neuronal (glial, respiratory, cardiac, gastrointestinal, skeletal and metabolic) mechanisms with a literature base updated to 15 August 2026, and identifies the continuing absence of any validated biomarker or surrogate endpoint, rather than target identification, as the principal obstacle to efficient trials. • It critically appraises the post-trofinetide landscape - divergent FDA and EMA assessments of the same trial data, a fatal high-dose AAV hyperinflammatory event, and single-arm registrational gene-therapy programmes reported largely outside peer review - and concludes that the demonstrated outcome to date is gain or re-acquisition of developmental milestones, not reversal of established disease.
2026-09-06 | Alteration of cholinergic pathway in the enteric nervous system of a mouse model of Rett syndrome.
Rett syndrome (RTT) is a severe neurological disorder caused by pathogenic variants in the MECP2 gene associated with gastrointestinal (GI) motility disorders strongly impacting patients' quality of life. Intestinal motility relies on coordinated neuronal activity in the enteric nervous system (ENS) where MECP2 is highly expressed. Here, we sought to determine whether cholinergic-mediated excitatory neuromuscular transmission could be affected in the ENS of a RTT mouse model and the functional consequences on intestinal motility. In this study, 55 days-old wild type (WT) and Mecp2-knock-out (KO) mice were used. After confirming the increase in GI transit time in Mecp2-KO mice in vivo, intestinal mechanical activity was assessed in vitro by evaluating contractile responses of small intestinal muscle to electrical field stimulation (EFS) of the ENS. The function of the cholinergic pathway was evaluated using gene expression, protein, and enzymatic activity quantifications of different factors of the acetylcholine (ACh) metabolism. Our in vivo results confirm that the slowed GI transit previously identified in RTT patients and in the mouse model. In vitro, successive EFS lead to a progressive and rapid decrease in the amplitude of cholinergic contractions in Mecp2-KO mice contrary to WT mice. Levels of ACh are decreased in the ENS of Mecp2-KO mice (-47%, P-value<0.01) due to decreased activity of the synthesizing enzyme choline-acetyltransferase (-39%, P-value = 0.04). In addition to the deficit of ACh, we found that both nicotinic and muscarinic cholinergic receptors are also significantly impacted. This is the first report of a major dysfunction of the enteric cholinergic pathway in a mouse model of RTT supporting its direct involvement in GI disorders in this disease. We propose that the rhythmic GI contractions occurring during fed conditions may cause a rapid depletion of the stock of enteric ACh that could largely depress the propulsive efficiency of, or even suppress, peristalsis during digestion.
2026-09-05 | Rett syndrome in the therapeutic era: Rethinking diagnosis, boundaries, clinical outcomes, and financing.
Rett syndrome (RTT) is a severe neurodevelopmental disorder characterized by multiple neurological impairments, which affects predominantly females. It is associated, in most cases, with pathogenic variants in MECP2, the gene encoding the methyl-CpG-binding protein 2. In the four decades since its description in the English literature, the RTT field has seen major progress in the understanding of its genetics, neurobiology, and clinical evolution. These have led to the first drug approved for core symptoms of a neurodevelopmental disorder, trofinetide, and gene replacement programs at advanced development. These achievements have brought new challenges and highlighted unresolved issues. These include diagnosis before developmental regression and of individuals without core RTT features, including males; the role of MECP2 testing in RTT diagnosis; the boundaries of RTT; instruments needed for assessing clinical evolution in research and practice; the definition of meaningful clinical improvement; and the development, availability, and affordability of new treatments. These topics are reviewed in terms of their implications for RTT and for other genetic neurodevelopmental disorders.
2026-09-01 | Compatibility of trofinetide with ketogenic diets in patients with rett syndrome: case reports
Rett syndrome (RTT) is a rare neurodevelopmental disease characterized by developmental stagnation and regression. Epilepsy is seen in 60–80% of patients with RTT. Seizures are primarily managed with pharmacologic therapy; although ketogenic diets can be used to further optimize seizure control in patients with drug-resistant epilepsy. When following a ketogenic diet, all sources of carbohydrates must be considered. Trofinetide, an approved treatment for RTT, is available as trofinetide oral solution (TOS; marketed as DAYBUE®) and trofinetide powder for oral solution (TPOS; marketed as DAYBUE® Stix). TOS contributes 0.03 g of carbohydrates/mL of oral solution while TPOS contributes 0.04 g of carbohydrates/g of powder. Across recommended doses, TOS contributes 1.5–3.6 g of carbohydrates/day and TPOS contributes 0.40–0.96 g of carbohydrates/day. The feasibility implementing a ketogenic diet while taking trofinetide is unknown. Here, we present cases of patients with RTT who were started and maintained on ketogenic diets amid concomitant TOS before TPOS was available. This suggests that TOS is compatible with ketogenic diets in patients with RTT. TPOS should also be compatible with ketogenic diets, as it contains less carbohydrates per dose than TOS. More research is needed to confirm the compatibility of trofinetide formulations with ketogenic diets.
proteins
2026-05-11 | Toward an NGF-based therapy for Rett syndrome.
Rett syndrome (RTT) is a severe neurodevelopmental disorder primarily caused by mutations in the MECP2 gene. Although recent therapeutic advances, such as the approval of Trofinetide, offer partial relief, no comprehensive curative treatment is currently available. Among the emerging strategies, nerve growth factor (NGF) has gained attention due to its neurotrophic and immunomodulatory properties. This review, in addition to discussing the key features of RTT and the role of growth factors, also highlights recent evidence supporting NGF-based strategies for RTT, focusing on two independent studies that tested intranasal administration of NGF-like molecules in Mecp2-mutant mice. Both recombinant human NGF (rhNGF) and a modified, "painless" variant (hNGFp) improved behavioral (cognitive and motor) symptoms. While rhNGF primarily restored mitochondrial function, hNGFp restored neuroinflammatory responses through microglial regulation. Despite differences in molecular mechanisms and dosages, both molecules demonstrated efficacy without adverse effects, especially when administered intranasally, preventively, and over longer periods. These findings suggest that NGF may act through dual mechanisms, by supporting energy homeostasis and regulating immune responses. The use of intranasal delivery further enhances translational potential by overcoming blood-brain barrier limitations. Together, these studies provide a strong rationale for pursuing NGF-based therapies in RTT and encourage further investigations to optimize dosing, timing, and safety in preclinical and clinical settings.
2026-02-16 | Pediatric intestinal pseudo-obstruction found in 3-year-old male with Rett-related mutation of methyl-CpG binding protein 2.
A 3-year-old male with chronic abdominal distention, constipation, and severe malnutrition is diagnosed with pediatric intestinal pseudo-obstruction (PIPO) after extensive evaluation that excluded mechanical, malabsorptive, metabolic, inflammatory, and infectious causes. Aside from speech delay, he has a normal neurologic exam. Whole exome sequencing reveals a pathogenic methyl-CpG binding protein 2 (MECP2) variant, suggesting atypical Rett syndrome. Management includes promotility agents and a gastrostomy tube with cyclic feedings of peptide-based formula, leading to resolution of symptoms. This case highlights the diagnostic complexity of PIPO and the need to consider genetic etiologies, including MECP2-related disorders, even in patients with mild neurologic findings. Early genetic testing and multidisciplinary care are essential for diagnosis and management in this atypical presentation of Rett syndrome with manifestation of PIPO.
2026-02-09 | IGF1 peptide targets Rett Syndrome astrocytes to degrade IGF binding protein, rescue synaptogenesis and restore mitochondrial function.
Rett syndrome (RTT), a severe neurodevelopmental disorder caused by mutations in MECP2, leads to profound synaptic and circuit deficits in the brain. While neurons have historically been the focus of RTT pathology, emerging evidence implicates astrocytes in non-cell autonomous mechanisms that impair synaptic structure, function and development. Here, we uncover a central role for astrocyte-secreted IGFBP2 in mediating these deficits and demonstrate that treatment with an IGF1-derived peptide restores synapse formation by promoting IGFBP2 degradation. Using an indirect astrocyte-neuron co-culture system, we show that astrocytes derived from RTT model mice suppress excitatory synapse formation in wild-type neurons and that this impairment is reversed when RTT astrocytes are treated with IGF1(1-3) peptide. Proteomic analysis reveals elevated levels of IGFBP2 in RTT astrocytes and their conditioned media. IGF1(1-3) peptide treatment leads to proteasomal degradation of IGFBP2, increasing IGF1 bioavailability, restoring mitochondrial function, and enhancing downstream PI3K/Akt signaling in neurons. Our data define a molecular mechanism by which astrocyte dysfunction in RTT can be rescued and provide a mechanistic basis for the therapeutic efficacy of IGF1(1-3) peptide, including Trofinetide, an FDA-approved IGF1 peptide mimetic, in RTT. Astrocyte dysfunction is increasingly recognized as a contributor to neurodevelopmental disorders, yet precise mechanisms remain elusive. Here, we identify IGFBP2 as a key astrocyte-derived inhibitor of synaptogenesis in Rett syndrome. We show that an IGF1-derived peptide, IGF1(1-3), depletes IGFBP2 via proteasomal degradation. This restores IGF1 bioavailability and rescues synaptic function in a non-cell-autonomous manner. These findings provide a mechanistic explanation for the clinical efficacy of IGF1 peptide and its mimetics in Rett syndrome, and highlight astrocytes as rational therapeutic targets in neurodevelopmental and other disorders.
2025-11-26 | To What Extent Could the Parasite Toxoplasma Gondii revolutionize the Treatment of Rett Syndrome
Rett Syndrome (RTT) is a rare, neurodevelopmental disorder which, up until now, lacks curative treatment. Toxoplasma gondii is an infectious parasite responsible for the prevalent infection Toxoplasmosis within humans, and is notable for its ability to cross the blood-brain barrier and establish latent cerebral infection. This essay evaluates the current, most promising treatments being investigated to treat RTT, which are Trofinetide, gene therapy and cholesterol therapy, through comparison in terms of tolerability, efficacy and translational potential. I evaluate the extent to which T. Gondii could revolutionize RTT treatment by overcoming limitations involved in investigated treatments. Ultimately, while T. Gondii shows promising early results as a novel biological mechanism with specifically adapted machinery to deliver functional proteins to the brain, I explore the distinctive challenges this form of treatment also faces, including but not limited to specificity, long-term viability and safety. Finally, I conclude that, although treatment using T. Gondii presents a radical change from investigated therapies, it does not yet constitute a successful or clinically transformative solution, suggesting that further investigation to discover specific dosage requirements of the therapeutic protein is required, in order to fully target the necessary patient populations and address their unmet needs.
2025-11-10 | Ghrelin restores D1 receptor-mediated dopamine neurotransmission and enhances attentive behaviour in Mecp2 KO mice.
Rett syndrome is an X-linked neurodevelopmental disorder characterised by cognitive, attentional, and communicative impairments along with sensory and motor deficits. Optimal activation of dopamine D1 receptor signalling in the prefrontal cortex (PFC) is essential for cognition and object-based attention. Ghrelin has been observed to modulate dopaminergic neurotransmission and improve cognitive function and attention impairments in various animal models. Herein, we investigated the effects of ghrelin on D1 receptor-mediated dopaminergic neurotransmission in the PFC of male Mecp2 knockout (KO) mice, a mouse model of Rett syndrome, using in vivo microdialysis. External stimuli, such as saline injection and novelty induced increases in the dopamine levels in the PFC of wild-type mice, and the dopamine release was bidirectionally regulated by D1 receptors. In the PFC of Mecp2 KO mice, the dopaminergic responses to external stimuli were attenuated, and the dopamine reuptake system was upregulated. Pharmacological analyses revealed that the ability of D1 receptor signalling to inhibit dopamine release would be upregulated and/or its ability to stimulate dopamine release would be downregulated in Mecp2 KO mice. Ghrelin injection (8.6 μg/mouse, s.c.) restored dopaminergic responses to external stimuli by adjusting the altered function of D1 receptor signalling. While ghrelin injection failed to improve the impaired object recognition ability in Mecp2 KO mice, it enhanced attention and exploratory activity toward objects. These findings in Mecp2 KO mice suggest that ghrelin may enhance D1 receptor-mediated dopaminergic neurotransmission and exert beneficial effects on dopamine-related behaviour, such as attention and investigatory motivation towards objects, in Rett syndrome.
gene therapies
2026-08-26 | Beyond Rett syndrome: a case series expanding the neurological spectrum associated with pathogenic MECP2 variants.
Although pathogenic variants in MECP2 are classically associated with Rett syndrome (RTT), increasing evidence suggests that they can underlie a broader spectrum of neurological phenotypes. Clinical manifestations may vary according to sex, variant type, residual protein function, and pattern of X-chromosome inactivation. We describe five unrelated individuals carrying pathogenic MECP2 variants identified through multiplex ligation-dependent probe amplification, chromosomal microarray analysis, and next-generation sequencing. Clinical, neuroradiological, neurophysiological, and molecular findings were retrospectively reviewed. Two unrelated girls carrying large de novo Xq28 deletions encompassing the entire MECP2 locus presented with mild neurodevelopmental impairment and epilepsy, but no developmental regression or classic RTT features. Both girls showed borderline cognitive functioning and normal brain MRI. A 9-year-old boy carrying a maternally inherited MECP2 frameshift variant presented with intellectual disability, autism spectrum disorder, and focal epilepsy, whereas carriers in his family exhibited milder neuropsychiatric manifestations. A 44-year-old man carrying a MECP2 missense variant presented with an early-onset spastic-ataxic syndrome, peripheral neuropathy, and cerebellar dysfunction, while a 16-year-old girl patient carrying a distinct de novo MECP2 missense variant displayed isolated mild motor incoordination and subtle cerebellar signs with preserved cognitive functioning. Our findings expand the evidence that pathogenic MECP2 variants can produce neurological phenotypes distinct from classic RTT, including mild neurodevelopmental impairment without regression, and predominantly cerebellar or spastic-ataxic manifestations associated with limited cognitive involvement. Allelic heterogeneity seems to correlate with clinical phenotypes, at least in our small cohort. In conjunction with established diagnostic criteria, these observations support testing MECP2 in a selection of atypical neurodevelopmental and movement disorder presentations.
2026-08-10 | Translational reading frame predicts the pathogenicity of C-terminal frameshift deletions in MeCP2.
Mutations in the MECP2 gene cause the severe neurological disorder Rett syndrome. A cluster of frameshift-causing C-terminal deletions (CTDs) removes ~100 amino acids and accounts for approximately 10% of RTT-causing mutations. Their pathogenicity is unexpected because this C-terminal domain is dispensable in mice. Analysis of pathogenic and benign human MECP2 variants reveals that some individuals with apparently typical CTDs do not develop Rett syndrome, confirming that C-terminal truncations are not intrinsically pathogenic. Using human sequence data and mouse models we show that pathogenicity results from a marked reduction in MeCP2 levels and depends on the presence of a proline proline stop motif (-PPX) generated by a shift to the +2 reading frame. CTDs that shift to the +1 frame avoid this motif and are benign. Replacing the stop codon of the PPX motif with tryptophan restores MeCP2 expression and rescues RTT-like phenotypes in a CTD mouse model. An adenine base editor efficiently introduces this substitution in cultured cells. These findings define a reliable prognostic distinction between benign and pathogenic CTDs and establish a potential editing strategy for correcting disease-causing CTD mutations.
2026-07-17 | Programmable CRISPRtune dissects the transcriptional repressive activity of MeCP2.
The ability to control the expression of human genes is a major goal in synthetic biology, enables dissection of gene function, and can be harnessed for therapeutic applications. Advances in genome editing and transcriptional engineering often result in complete gene inactivation or full transcriptional repression. However, programmable tools to dial transcription at intermediate levels remain challenging. Here, we present CRISPRtune - a synthetic fusion of MeCP2 to catalytically dead dCas9 that tunes down transcription of endogenous genes in human cells by harnessing the mild repressor activity of MeCP2. Using pooled genome-scale CRISPR screens, we tune the expression of thousands of endogenous genes and define the targeting rules of CRISPRtune in human cells. With a platform to target MeCP2 at defined genomic sites, we show the direct epigenetic changes induced by MeCP2 at gene promoters and we identify its genetic dependency partners for productive transcriptional repression. Rett syndrome-associated mutations of MeCP2 show defects for transcriptional repression due to their failure to remodel the local epigenetic landscape of target genes. Together, we present a programmable method for transcriptional tuning in mammalian cells and offer an orthogonal platform to dissect the mechanistic function of chromatin regulators in living cells.
2026-06-30 | Recent advances in epigenetic therapeutics for Rett syndrome: from mechanisms to clinical trials
Rett syndrome (RTT) stands at the forefront of the genetic therapy revolution. This severe X-linked neurodevelopmental disorder, primarily caused by mutations in the MECP2 gene, was historically considered a static condition but is now recognized as a potentially reversible neurodevelopmental disorder. This review synthesizes recent breakthroughs in our understanding of MeCP2’s role in chromatin architecture, including its involvement in liquid-liquid phase separation (LLPS). We critically examine the transition from conventional symptom management to precision epigenetic therapeutics. Key advances discussed include next-generation gene replacement strategies with autoregulatory control to prevent toxicity, programmable epigenetic editing (e.g., CRISPR-off/on) to correct MECP2 expression endogenously, and novel approaches for X-chromosome reactivation (XCI). Furthermore, we propose a stratified therapeutic framework (genotype-guided therapies) based on specific mutation types. Finally, we analyze data from ongoing clinical trials and highlight the remaining hurdles—such as delivery efficiency, immunogenicity, and the urgent need for objective biomarkers—that must be overcome to translate these epigenetic innovations into a cure.
2026-04-30 | A functional MeCP2-LBX1 axis regulates neuronal gene expression in neuronal cells.
Rett syndrome is a neurodevelopmental disorder caused by mutations in MECP2 and is frequently associated with scoliosis; however, the molecular mechanisms linking MeCP2 dysfunction to this phenotype remain poorly understood. In this study, we identify LBX1, a gene implicated in adolescent idiopathic scoliosis, as a downstream target of MeCP2 and investigate its regulatory role in neuronal gene expression. Chromatin immunoprecipitation (ChIP) analysis demonstrated that MeCP2 binds to the promoter region of LBX1, which contains a CT-rich and highly methylated sequence, providing a favorable context for MeCP2 binding. Consistently, CRISPR/Cas9-mediated disruption of MECP2 in A172 cells resulted in a marked reduction of LBX1 expression, whereas expression of the antisense transcript LBX1-AS remained unchanged, indicating gene-specific regulation. These findings support a role for MeCP2 as a transcriptional activator of LBX1 in this context. Given the established role of LBX1 in specifying GABAergic and glutamatergic neuronal identities, we performed targeted gene expression profiling using a GABA and glutamate-related PCR array. Several neuronal genes were differentially expressed in MeCP2-deficient cells, and GABRB1 and P2RX7 were identified as LBX1-dependent downstream targets, as their expression levels were restored by ectopic expression of LBX1. Together, these findings reveal a previously unrecognized MeCP2-LBX1 regulatory axis and suggest that its disruption may contribute to altered neuronal signaling. This pathway provides a potential molecular link between MeCP2 dysfunction and scoliosis in Rett syndrome.
oligonucleotides
2026-09-22 | MeCP2 MBD-ID module: a unified DNA/RNA binding interface disrupted in Rett syndrome.
Rett syndrome neurodevelopmental disorder is caused by mutations in the epigenetic regulator MeCP2. While the MeCP2 methyl-CpG binding domain (MBD) is well-characterized, the function of the adjacent intervening domain (ID) remains largely understudied. The ID has been described as a distinct RNA-binding region, yet evidence also suggests RNA competitively displaces MeCP2 from DNA. Here, we address these conflicting findings by demonstrating the MBD and ID do not function in isolation but as a synergistic functional unit. The ID significantly enhances affinity of the MBD for methylated DNA by ∼35-fold. Moreover, these two subdomains form a high-affinity RNA-binding module, with preference for structured RNAs increased over 1000-fold compared to the MBD or ID alone. We find binding to RNA precludes binding to DNA, such that the integrated MBD-ID unit explains the competition phenomenon. Analysis of Rett syndrome-associated ID mutations (R167W, K174Q, and R190H) and a therapeutic MiniGene reveals they do not disrupt methyl-DNA binding but instead selectively weaken RNA and non-methylated DNA binding, thereby disrupting the competitive balance between nucleic acids. Our work establishes the MBD-ID module as MeCP2's central nucleic acid interaction hub, whose disruption provides a potential molecular etiology of Rett syndrome due to mutations in the ID.
2026-08-26 | MeCP2 Dosage Control in Rett Syndrome: Non-Coding RNA-Based and Epigenetic Strategies for Safer Gene Therapy.
Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder that is caused in most cases by pathogenic variants in MECP2, the gene encoding methyl-CpG-binding protein 2 (MeCP2). Despite substantial progress in the development of gene therapy, restoring MECP2 expression remains challenging because MeCP2 is highly dosage-sensitive. Both deficiency and excessive expression of this protein are associated with severe neurological abnormalities. This makes simple viral vector-mediated replacement of MECP2 potentially unsafe and underscores the need for multilayered systems that control transgene expression. This review discusses current and emerging strategies for regulating MeCP2 expression in RTT, with an emphasis on non-coding RNA-based and epigenetic mechanisms. Particular attention is given to the limitations of conventional AAV-mediated gene therapy, the use of cell-specific and endogenous promoters, miRNA-regulated elements, autoregulatory systems, and post-transcriptional control of MECP2 expression. Strategies for reactivating the inactive X chromosome are also discussed, including XIST-dependent regulation and epigenome editing. In addition, the review considers CRISPR-mediated regulation, selective epigenetic activation, and combined therapeutic platforms that integrate viral delivery, RNA-dependent post-transcriptional control, and endogenous gene regulation. Overall, clinically applicable gene therapy for RTT will likely need to move beyond simple MECP2 replacement and instead rely on precise cell- and dose-dependent regulation of its expression. Non-coding RNA and epigenetic mechanisms represent important layers of such control and may contribute to the development of safer gene therapy strategies for RTT.
2026-03-04 | Modulating alternative splicing of MECP2 is a potential therapeutic strategy for Rett syndrome.
Rett syndrome (RTT) is a neurological disorder caused by loss-of-function mutations in methyl-CpG-binding protein 2 (MECP2), which encodes a transcriptional regulator essential for maintenance of normal neuronal function. The current US Food and Drug Administration-approved treatment for RTT, trofinetide, mildly alleviates some symptoms. In contrast, reintroducing MeCP2 or increasing its amount through transgenesis in mouse RTT models improves most neurological phenotypes and enhances survival. Here, we devised a therapeutic strategy to moderately increase MeCP2 protein by modulating the alternative splicing of MECP2 to switch the less efficiently translated e2 to the more efficiently translated e1 isoform. We deleted Mecp2 exon 2 (unique to e2), leading to production of only e1 mRNA, and showed that this up-regulated MeCP2 by 50 to 60% in mice. Next, we investigated the consequences of isoform switching in two independent RTT induced pluripotent stem cell (iPSC)-derived neuron models harboring mutations that reduce both MeCP2 expression and function. Exon 2 deletion in neurons derived from patients with MeCP2-G118E up-regulated MeCP2, ameliorated morphological and electrophysiological changes, and corrected the dysregulated transcriptome in these neurons. Isoform switching in neurons derived from patients with MeCP2-G118E, modeling a severe RTT mutation, only modestly affected MeCP2 protein abundance and, despite this, led to a partial transcriptomic rescue. Last, an exon 2-skipping morpholino up-regulated MeCP2-E1 in vivo in mice. These data set the stage for a potential therapeutic strategy using antisense oligonucleotides to promote isoform switching in patients with RTT who carry partially functioning alleles of MECP2.
2026-02-13 | A Translational Roadmap for Neurological Nonsense Mutation Disorders.
Nonsense mutations, responsible for ~11% of gene lesions causing human monogenic diseases, introduce premature termination codons (PTCs) that lead to truncated proteins and nonsense-mediated mRNA decay (NMD). In the central nervous system (CNS), these mutations drive severe, progressive neurological conditions such as spinal muscular atrophy, Rett syndrome, and Duchenne muscular dystrophy. Readthrough therapies-strategies to override PTCs and restore full-length protein expression-have evolved from early aminoglycosides to modern precision tools including suppressor tRNAs, RNA editing, and CRISPR-based platforms. Yet clinical translation remains hampered by inefficient CNS delivery, variable efficacy, and the absence of personalized stratification. In this review, we propose a translational framework-the 4 Ds of Readthrough Therapy-to systematically address these barriers. The framework dissects the pipeline into Detection (precision patient identification and biomarker profiling), Delivery (engineered vectors for CNS targeting), Decoding (context-aware molecular correction), and Durability (long-term safety and efficacy). By integrating advances in machine learning, nanocarriers, base editing, and adaptive trial designs, this roadmap provides a structured strategy to bridge the translational gap. We advocate that a synergistic, modality-tailored approach will transform nonsense suppression from palliative care to durable, precision-based cures for once-untreatable neurological disorders.
2025-07-05 | Targeting microRNA-dependent control of X chromosome inactivation improves the Rett Syndrome phenotype.
X chromosome inactivation (XCI) is induced by Xist long non-coding RNA and protein-coding genes. However, the role of small non-coding RNA function in XCI remains unidentified. Our genome-wide, loss-of-function CRISPR/Cas9 screen in female fibroblasts identified microRNAs (miRNAs) as regulators of XCI. A striking finding is the identification of miR106a among the top candidates from the screen. Loss of miR106a is accompanied by altered Xist interactome, leading to dissociation and destabilization of Xist. XCI interference via miR106a inhibition has therapeutic implications for Rett syndrome (RTT) girls with a defective X-linked MECP2 gene. Here, we discovered that the inhibition of miR106a significantly improves several facets of RTT pathology: it increases the life span, enhances locomotor activity and exploratory behavior, and diminishes breathing variabilities. Our results suggest that miR106a targeting offers a feasible therapeutic strategy for RTT and other monogenic X-linked neurodevelopmental disorders.
other
2026-08-27 | Transforming Rett Syndrome Research: Lessons from Successes and Failures in Clinical Trials
This white paper explores the evolving landscape of Rett syndrome clinical development, examining the disease biology, approved treatments, pivotal clinical trials, and key challenges in therapeutic research. The white paper highlights the significance of trofinetide (Daybue), the first FDA-approved treatment for Rett syndrome, and reviews the evidence from the Phase 3 LAVENDER study that supported its approval. It also analyzes unsuccessful development programs, including blarcamesine and sarizotan, to identify critical lessons for future studies. The paper discusses the importance of selecting appropriate endpoints such as RSBQ and CGI-I, managing placebo response, addressing small patient populations, and incorporating objective assessment tools to improve trial outcomes. Additionally, it outlines iNGENū CRO’s physician-led approach to designing FDA-ready, cost-effective clinical trials aimed at accelerating the development of innovative therapies for patients living with Rett syndrome.
2026-05-25 | The role of the gut mycobiota in neurodevelopmental disorders: a multikingdom disruption of the gut-brain axis.
Research on the gut-brain axis in neurodevelopmental disorders (NDDs) has historically focused on bacteria, overlooking fungal contributions. This review synthesizes emerging evidence to propose that intestinal fungi may actively contribute to NDD pathophysiology through multikingdom interactions, though causality requires validation. We delineate a consistent gut mycobiota dysbiosis signature across autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and Rett syndrome (RTT) characterized by reduced diversity and Candida expansion. Potential mechanisms include compromised intestinal barrier integrity, systemic immune activation via Dectin-1/Syk/CARD9 signaling, and disruption of neuroactive metabolites like short-chain fatty acids. We propose distinct etiological pathways: a "top-down" cascade in RTT, where MeCP2 mutation-induced dysmotility creates a pro-dysbiotic niche, and a "bottom-up" pathway in ASD and ADHD, where bacterial dysbiosis erodes colonization resistance, permitting fungal overgrowth. This "bacteria-fungi-host" framework provides a coherent explanation for gut-brain axis disruptions and opens avenues for biomarker discovery and multikingdom therapeutic interventions.
2025-11-15 | Harnessing the microbiota-gut-brain axis to prevent and treat pediatric neurodevelopmental disorders: translational insights and strategies.
Pediatric neurodevelopmental and neuropsychiatric disorders, including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), Rett syndrome (RTT), Tourette syndrome (TS), Down syndrome (DS), Fragile X syndrome (FXS), Prader–Willi syndrome (PWS), fetal alcohol spectrum disorder (FASD), pediatric epilepsy, congenital Zika syndrome (CZS), Wilson’s disease (WD), and cerebral palsy (CP), are associated with long-term impairments and high societal burden. Emerging evidence implicates the microbiota–gut–brain axis (MGBA) in early neurodevelopment with factors, such as maternal microbiota, birth mode, antibiotics, and infant diet shaping microbial colonization and influencing developmental outcomes. This review aims to synthesize current translational evidence from animal and human studies to address the following research questions: (1) How do disruptions in the MGBA contribute to the pathophysiology of pediatric neurodevelopmental disorders? (2) What microbiome alterations are consistently associated with these conditions? and (3) What ethical and safety considerations should be addressed in implementing early-life microbiome-based interventions? We also assess emerging microbiota-based interventions, including probiotics, prebiotics, dietary strategies, fecal microbiota transplantation, and traditional therapies, and their potential to modulate disease outcomes. The MGBA presents a promising, yet currently preliminary, target for early intervention in pediatric neurodevelopmental disorders. There is emerging evidence that therapies targeting the microbiota could have an effect on neurodevelopment and outcomes of health and disease; however, most of the findings are in the initial stages, and the evidence is still inconsistent. Therefore, the findings must be translated into mechanisms of action over extended periods with longitudinal multi-omic studies to identify possible intervention windows, optimize personalized therapies, and evaluate the safety and efficacy of interventions targeting the microbiome. Till that point, these microbiota-targeted approaches should be approached cautiously and treated as experimental in the realm of pediatric interventions, given the present-day state of evidence.
2025-02-21 | Transduction of hematopoietic stem and progenitor cells by an MECP2 lentiviral vector improves Rett syndrome phenotypes
Introduction Rett Syndrome is a genetic neurodevelopmental disorder caused by decreased levels of MeCP2. Due to mutations in the MECP2 gene, insufficient MeCP2 protein levels lead to clinical phenotypes including the loss of normal movement, decreased communication, seizures, sleep disorders, and breathing problems. Currently there is no cure for Rett Syndrome and the only means to help patients is palliative care directed to their specific symptoms. Therefore, novel therapies need to be developed to alleviate disease phenotypes by restoring normal MECP2 expression. An autologous hematopoietic stem cell and gene therapy approach for Rett syndrome may offer a benefit to affected patients by systemic delivery of functional MeCP2, including to affected neurons in the central nervous system. Methods In our current experiments, we evaluated the therapeutic effect of MECP2 lentiviral vector transduced human CD34+ hematopoietic stem and progenitor cells after transplantation into an immunodeficient mouse model of Rett syndrome. Results We observed improvement of Rett syndrome-related phenotypes including the reversion toward normal motor abilities in an open field assay for total activity, horizontal activity, and vertical rearing activity, and an increased latency to fall in a rotarod assay. An increased level of MeCP2 protein was also observed in the brain tissue of transplanted mice. Discussion By providing functional MeCP2 to affected cells, our results highlight the ability of this strategy to improve Rett syndrome phenotypes. These proof-of-concept studies demonstrate the potential use of a stem cell gene therapy approach as a novel treatment for Rett syndrome patients.
2025-01-03 | The Management of Bone Defects in Rett Syndrome.
Rett syndrome (RS) is a rare neurodevelopmental disorder primarily caused by mutations in the X-linked methyl-CpG binding protein 2 (MECP2) gene, responsible for encoding MECP2 which plays a pivotal role in regulating gene expression. The neurological and non-neurological manifestations of RS vary widely in severity depending on the specific mutation type. Bone complications, mostly scoliosis but also osteoporosis, hip displacement, and a high rate of fractures, are among the most prevalent non-neurological comorbidities observed in girls with RS. Low bone mineral density (BMD) is primarily due to a slow rate of bone formation due to dysfunctional osteoblast activity. The use of anticonvulsants, immobilization, low physical activity, poor nutrition, and inadequate vitamin D intake all significantly hamper skeletal maturation and the accumulation of bone mass in RS girls, making them more susceptible to fragility fractures. In RS patients, the upper and lower limbs are the most common sites for fractures which are due to both a reduced BMD and a diminished bone size. This review summarizes the knowledge on risk factors for fragility fracture in patients with RS and proposes a potential diagnostic and therapeutic pathway to enhance low BMD and mitigate the risk of fragility fractures. In particular, this review focused on the importance of clinical and instrumental evaluation of bone status as a basis for adequate planning of nutritional, pharmacological, and surgical interventions to be undertaken. Additionally, the management of bone defects in individuals with RS should be customized to meet each person's specific needs, abilities, and general health.
small molecules
2026-09-30 | Fenfluramine in Rett syndrome: A multidimensional clinical study.
Rett syndrome (RTT) is a severe neurodevelopmental disorder frequently associated with drug-resistant epilepsy, autonomic dysfunction, respiratory abnormalities, sleep disturbances, and behavioral impairment. Fenfluramine has shown efficacy in developmental and epileptic encephalopathies and may provide broader therapeutic benefits through modulation of serotonergic and sigma-1 receptor pathways. We conducted a prospective, open-label, single-center study to evaluate the efficacy, safety, and tolerability of adjunctive fenfluramine in patients with classic RTT carrying pathogenic MECP2 variants. Clinical assessments were performed at baseline and after 3 and 6 months of treatment. Outcomes included seizure frequency; clinician-reported measures of RTT severity, including the Clinical Global Impression-Improvement (CGI-I) scale, Clinical Severity Scale (CSS), and Motor Behavior Assessment (MBA); caregiver-reported measures, including the Rett Syndrome Behavior Questionnaire (RSBQ), Sleep Disturbance Scale for Children (SDSC), the EQ-5D-5L quality of life scale; and neurophysiological measures using auditory evoked potentials. Eight patients with classic RTT and drug-resistant epilepsy were included. Median age was 12 years (range, 6-17 years), and the median number of previously failed antiseizure medications was 5 (range, 2-10). All patients achieved a >50% reduction in seizure frequency. Significant improvements were observed in clinician-reported outcomes, including CGI-I, CSS, and MBA scores, and in caregiver-reported behavioral symptoms assessed with the RSBQ at 3 and 6 months (-7 and -9, respectively). Sleep disturbances improved markedly, with normalization of SDSC scores in all patients by month 6. Respiratory dysfunction, including hyperventilation-related symptoms, improved during follow-up. Neurophysiological assessments showed improved attentional and auditory discrimination processing in a subset of patients. Adverse events occurred in 71% of patients, most commonly somnolence; no patient discontinued treatment because of tolerability issues. Fenfluramine was associated with clinically meaningful improvements across several symptom domains in patients with RTT, including seizures, respiratory dysfunction, behavior, sleep, and overall disease severity, with an acceptable safety profile. Further evaluation of fenfluramine as a potential multisymptomatic treatment strategy in RTT in prospective controlled studies is warranted. Rett syndrome is a rare genetic disorder with complex symptoms that affect many aspects of daily life. In this study, fenfluramine was associated with improvements in seizures and several other important symptoms, including behavior, sleep, breathing, and clinical severity. The treatment was generally well tolerated. These results support further studies to determine whether fenfluramine could become a treatment for multiple symptoms of Rett syndrome.
2026-09-10 | Rett syndrome: MECP2 biology, multisystem pathophysiology, and the evolving therapeutic landscape.
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder arising predominantly from de novo loss-of-function mutations in MECP2, affecting approximately 1 in 10,000 live female births. MECP2 is a dosage-sensitive epigenetic regulator acting through its methyl-CpG-binding (MBD) and transcriptional-repression (TRD) domains; isoform-specific expression and X-chromosome-inactivation mosaicism drive the wide phenotypic variability, with mutation type broadly correlating with severity. Although historically viewed as neuron-centric, RTT is a multisystem disorder: beyond psychomotor regression, stereotypic hand movements, gait apraxia, and loss of spoken language, MECP2 deficiency contributes to brainstem-mediated breathing dysrhythmia, QTc prolongation, enteric dysmotility, low bone density, and mitochondrial/metabolic deficits, amplified by glial-neuronal crosstalk. Preclinical models, MECP2 rodents, patient iPSC-derived neurons, and cerebral organoids, reveal synaptic and dendritic deficits that improve substantially when MECP2 is reactivated in these systems, indicating that MECP2-deficient neurons remain viable rather than degenerating; whether comparable improvement can be achieved in affected individuals is not yet established. The therapeutic landscape now spans multidisciplinary supportive care, the first approved pharmacotherapy trofinetide, AAV-mediated MECP2 gene replacement (now in pivotal trials, with an important gene-therapy safety signal), antisense oligonucleotides for dosage normalisation, and emerging metabolic agents; validated biomarkers and objective outcome measures remain a major unmet need. RTT is a multisystem monogenic disorder whose management is shifting from symptom control toward disease modification. Phenotypic rescue after MECP2 restoration in rodent models provides the rationale for this shift but does not establish that RTT is reversible in patients; progress now depends on validated biomarkers, dose-controlled disease-modifying therapies, long-term outcome data, and equitable global access. • More than 90-95% of classic Rett syndrome is caused by de novo loss-of-function mutations in MECP2, a dosage-sensitive epigenetic reader whose isoform distribution, residual function and X-chromosome-inactivation mosaicism together account for much of the phenotypic variability. • Reactivating MECP2 in symptomatic adult rodents substantially improves many disease features, establishing that MECP2-deficient neurons are functionally impaired rather than lost and providing the rationale for disease-modifying therapy. • This review integrates isoform-specific and non-neuronal (glial, respiratory, cardiac, gastrointestinal, skeletal and metabolic) mechanisms with a literature base updated to 15 August 2026, and identifies the continuing absence of any validated biomarker or surrogate endpoint, rather than target identification, as the principal obstacle to efficient trials. • It critically appraises the post-trofinetide landscape - divergent FDA and EMA assessments of the same trial data, a fatal high-dose AAV hyperinflammatory event, and single-arm registrational gene-therapy programmes reported largely outside peer review - and concludes that the demonstrated outcome to date is gain or re-acquisition of developmental milestones, not reversal of established disease.
2026-09-06 | Alteration of cholinergic pathway in the enteric nervous system of a mouse model of Rett syndrome.
Rett syndrome (RTT) is a severe neurological disorder caused by pathogenic variants in the MECP2 gene associated with gastrointestinal (GI) motility disorders strongly impacting patients' quality of life. Intestinal motility relies on coordinated neuronal activity in the enteric nervous system (ENS) where MECP2 is highly expressed. Here, we sought to determine whether cholinergic-mediated excitatory neuromuscular transmission could be affected in the ENS of a RTT mouse model and the functional consequences on intestinal motility. In this study, 55 days-old wild type (WT) and Mecp2-knock-out (KO) mice were used. After confirming the increase in GI transit time in Mecp2-KO mice in vivo, intestinal mechanical activity was assessed in vitro by evaluating contractile responses of small intestinal muscle to electrical field stimulation (EFS) of the ENS. The function of the cholinergic pathway was evaluated using gene expression, protein, and enzymatic activity quantifications of different factors of the acetylcholine (ACh) metabolism. Our in vivo results confirm that the slowed GI transit previously identified in RTT patients and in the mouse model. In vitro, successive EFS lead to a progressive and rapid decrease in the amplitude of cholinergic contractions in Mecp2-KO mice contrary to WT mice. Levels of ACh are decreased in the ENS of Mecp2-KO mice (-47%, P-value<0.01) due to decreased activity of the synthesizing enzyme choline-acetyltransferase (-39%, P-value = 0.04). In addition to the deficit of ACh, we found that both nicotinic and muscarinic cholinergic receptors are also significantly impacted. This is the first report of a major dysfunction of the enteric cholinergic pathway in a mouse model of RTT supporting its direct involvement in GI disorders in this disease. We propose that the rhythmic GI contractions occurring during fed conditions may cause a rapid depletion of the stock of enteric ACh that could largely depress the propulsive efficiency of, or even suppress, peristalsis during digestion.
2026-09-05 | Rett syndrome in the therapeutic era: Rethinking diagnosis, boundaries, clinical outcomes, and financing.
Rett syndrome (RTT) is a severe neurodevelopmental disorder characterized by multiple neurological impairments, which affects predominantly females. It is associated, in most cases, with pathogenic variants in MECP2, the gene encoding the methyl-CpG-binding protein 2. In the four decades since its description in the English literature, the RTT field has seen major progress in the understanding of its genetics, neurobiology, and clinical evolution. These have led to the first drug approved for core symptoms of a neurodevelopmental disorder, trofinetide, and gene replacement programs at advanced development. These achievements have brought new challenges and highlighted unresolved issues. These include diagnosis before developmental regression and of individuals without core RTT features, including males; the role of MECP2 testing in RTT diagnosis; the boundaries of RTT; instruments needed for assessing clinical evolution in research and practice; the definition of meaningful clinical improvement; and the development, availability, and affordability of new treatments. These topics are reviewed in terms of their implications for RTT and for other genetic neurodevelopmental disorders.
2026-09-01 | Compatibility of trofinetide with ketogenic diets in patients with rett syndrome: case reports
Rett syndrome (RTT) is a rare neurodevelopmental disease characterized by developmental stagnation and regression. Epilepsy is seen in 60–80% of patients with RTT. Seizures are primarily managed with pharmacologic therapy; although ketogenic diets can be used to further optimize seizure control in patients with drug-resistant epilepsy. When following a ketogenic diet, all sources of carbohydrates must be considered. Trofinetide, an approved treatment for RTT, is available as trofinetide oral solution (TOS; marketed as DAYBUE®) and trofinetide powder for oral solution (TPOS; marketed as DAYBUE® Stix). TOS contributes 0.03 g of carbohydrates/mL of oral solution while TPOS contributes 0.04 g of carbohydrates/g of powder. Across recommended doses, TOS contributes 1.5–3.6 g of carbohydrates/day and TPOS contributes 0.40–0.96 g of carbohydrates/day. The feasibility implementing a ketogenic diet while taking trofinetide is unknown. Here, we present cases of patients with RTT who were started and maintained on ketogenic diets amid concomitant TOS before TPOS was available. This suggests that TOS is compatible with ketogenic diets in patients with RTT. TPOS should also be compatible with ketogenic diets, as it contains less carbohydrates per dose than TOS. More research is needed to confirm the compatibility of trofinetide formulations with ketogenic diets.
proteins
2026-05-11 | Toward an NGF-based therapy for Rett syndrome.
Rett syndrome (RTT) is a severe neurodevelopmental disorder primarily caused by mutations in the MECP2 gene. Although recent therapeutic advances, such as the approval of Trofinetide, offer partial relief, no comprehensive curative treatment is currently available. Among the emerging strategies, nerve growth factor (NGF) has gained attention due to its neurotrophic and immunomodulatory properties. This review, in addition to discussing the key features of RTT and the role of growth factors, also highlights recent evidence supporting NGF-based strategies for RTT, focusing on two independent studies that tested intranasal administration of NGF-like molecules in Mecp2-mutant mice. Both recombinant human NGF (rhNGF) and a modified, "painless" variant (hNGFp) improved behavioral (cognitive and motor) symptoms. While rhNGF primarily restored mitochondrial function, hNGFp restored neuroinflammatory responses through microglial regulation. Despite differences in molecular mechanisms and dosages, both molecules demonstrated efficacy without adverse effects, especially when administered intranasally, preventively, and over longer periods. These findings suggest that NGF may act through dual mechanisms, by supporting energy homeostasis and regulating immune responses. The use of intranasal delivery further enhances translational potential by overcoming blood-brain barrier limitations. Together, these studies provide a strong rationale for pursuing NGF-based therapies in RTT and encourage further investigations to optimize dosing, timing, and safety in preclinical and clinical settings.
2026-02-16 | Pediatric intestinal pseudo-obstruction found in 3-year-old male with Rett-related mutation of methyl-CpG binding protein 2.
A 3-year-old male with chronic abdominal distention, constipation, and severe malnutrition is diagnosed with pediatric intestinal pseudo-obstruction (PIPO) after extensive evaluation that excluded mechanical, malabsorptive, metabolic, inflammatory, and infectious causes. Aside from speech delay, he has a normal neurologic exam. Whole exome sequencing reveals a pathogenic methyl-CpG binding protein 2 (MECP2) variant, suggesting atypical Rett syndrome. Management includes promotility agents and a gastrostomy tube with cyclic feedings of peptide-based formula, leading to resolution of symptoms. This case highlights the diagnostic complexity of PIPO and the need to consider genetic etiologies, including MECP2-related disorders, even in patients with mild neurologic findings. Early genetic testing and multidisciplinary care are essential for diagnosis and management in this atypical presentation of Rett syndrome with manifestation of PIPO.
2026-02-09 | IGF1 peptide targets Rett Syndrome astrocytes to degrade IGF binding protein, rescue synaptogenesis and restore mitochondrial function.
Rett syndrome (RTT), a severe neurodevelopmental disorder caused by mutations in MECP2, leads to profound synaptic and circuit deficits in the brain. While neurons have historically been the focus of RTT pathology, emerging evidence implicates astrocytes in non-cell autonomous mechanisms that impair synaptic structure, function and development. Here, we uncover a central role for astrocyte-secreted IGFBP2 in mediating these deficits and demonstrate that treatment with an IGF1-derived peptide restores synapse formation by promoting IGFBP2 degradation. Using an indirect astrocyte-neuron co-culture system, we show that astrocytes derived from RTT model mice suppress excitatory synapse formation in wild-type neurons and that this impairment is reversed when RTT astrocytes are treated with IGF1(1-3) peptide. Proteomic analysis reveals elevated levels of IGFBP2 in RTT astrocytes and their conditioned media. IGF1(1-3) peptide treatment leads to proteasomal degradation of IGFBP2, increasing IGF1 bioavailability, restoring mitochondrial function, and enhancing downstream PI3K/Akt signaling in neurons. Our data define a molecular mechanism by which astrocyte dysfunction in RTT can be rescued and provide a mechanistic basis for the therapeutic efficacy of IGF1(1-3) peptide, including Trofinetide, an FDA-approved IGF1 peptide mimetic, in RTT. Astrocyte dysfunction is increasingly recognized as a contributor to neurodevelopmental disorders, yet precise mechanisms remain elusive. Here, we identify IGFBP2 as a key astrocyte-derived inhibitor of synaptogenesis in Rett syndrome. We show that an IGF1-derived peptide, IGF1(1-3), depletes IGFBP2 via proteasomal degradation. This restores IGF1 bioavailability and rescues synaptic function in a non-cell-autonomous manner. These findings provide a mechanistic explanation for the clinical efficacy of IGF1 peptide and its mimetics in Rett syndrome, and highlight astrocytes as rational therapeutic targets in neurodevelopmental and other disorders.
2025-11-26 | To What Extent Could the Parasite Toxoplasma Gondii revolutionize the Treatment of Rett Syndrome
Rett Syndrome (RTT) is a rare, neurodevelopmental disorder which, up until now, lacks curative treatment. Toxoplasma gondii is an infectious parasite responsible for the prevalent infection Toxoplasmosis within humans, and is notable for its ability to cross the blood-brain barrier and establish latent cerebral infection. This essay evaluates the current, most promising treatments being investigated to treat RTT, which are Trofinetide, gene therapy and cholesterol therapy, through comparison in terms of tolerability, efficacy and translational potential. I evaluate the extent to which T. Gondii could revolutionize RTT treatment by overcoming limitations involved in investigated treatments. Ultimately, while T. Gondii shows promising early results as a novel biological mechanism with specifically adapted machinery to deliver functional proteins to the brain, I explore the distinctive challenges this form of treatment also faces, including but not limited to specificity, long-term viability and safety. Finally, I conclude that, although treatment using T. Gondii presents a radical change from investigated therapies, it does not yet constitute a successful or clinically transformative solution, suggesting that further investigation to discover specific dosage requirements of the therapeutic protein is required, in order to fully target the necessary patient populations and address their unmet needs.
2025-11-10 | Ghrelin restores D1 receptor-mediated dopamine neurotransmission and enhances attentive behaviour in Mecp2 KO mice.
Rett syndrome is an X-linked neurodevelopmental disorder characterised by cognitive, attentional, and communicative impairments along with sensory and motor deficits. Optimal activation of dopamine D1 receptor signalling in the prefrontal cortex (PFC) is essential for cognition and object-based attention. Ghrelin has been observed to modulate dopaminergic neurotransmission and improve cognitive function and attention impairments in various animal models. Herein, we investigated the effects of ghrelin on D1 receptor-mediated dopaminergic neurotransmission in the PFC of male Mecp2 knockout (KO) mice, a mouse model of Rett syndrome, using in vivo microdialysis. External stimuli, such as saline injection and novelty induced increases in the dopamine levels in the PFC of wild-type mice, and the dopamine release was bidirectionally regulated by D1 receptors. In the PFC of Mecp2 KO mice, the dopaminergic responses to external stimuli were attenuated, and the dopamine reuptake system was upregulated. Pharmacological analyses revealed that the ability of D1 receptor signalling to inhibit dopamine release would be upregulated and/or its ability to stimulate dopamine release would be downregulated in Mecp2 KO mice. Ghrelin injection (8.6 μg/mouse, s.c.) restored dopaminergic responses to external stimuli by adjusting the altered function of D1 receptor signalling. While ghrelin injection failed to improve the impaired object recognition ability in Mecp2 KO mice, it enhanced attention and exploratory activity toward objects. These findings in Mecp2 KO mice suggest that ghrelin may enhance D1 receptor-mediated dopaminergic neurotransmission and exert beneficial effects on dopamine-related behaviour, such as attention and investigatory motivation towards objects, in Rett syndrome.
gene therapies
2026-08-26 | Beyond Rett syndrome: a case series expanding the neurological spectrum associated with pathogenic MECP2 variants.
Although pathogenic variants in MECP2 are classically associated with Rett syndrome (RTT), increasing evidence suggests that they can underlie a broader spectrum of neurological phenotypes. Clinical manifestations may vary according to sex, variant type, residual protein function, and pattern of X-chromosome inactivation. We describe five unrelated individuals carrying pathogenic MECP2 variants identified through multiplex ligation-dependent probe amplification, chromosomal microarray analysis, and next-generation sequencing. Clinical, neuroradiological, neurophysiological, and molecular findings were retrospectively reviewed. Two unrelated girls carrying large de novo Xq28 deletions encompassing the entire MECP2 locus presented with mild neurodevelopmental impairment and epilepsy, but no developmental regression or classic RTT features. Both girls showed borderline cognitive functioning and normal brain MRI. A 9-year-old boy carrying a maternally inherited MECP2 frameshift variant presented with intellectual disability, autism spectrum disorder, and focal epilepsy, whereas carriers in his family exhibited milder neuropsychiatric manifestations. A 44-year-old man carrying a MECP2 missense variant presented with an early-onset spastic-ataxic syndrome, peripheral neuropathy, and cerebellar dysfunction, while a 16-year-old girl patient carrying a distinct de novo MECP2 missense variant displayed isolated mild motor incoordination and subtle cerebellar signs with preserved cognitive functioning. Our findings expand the evidence that pathogenic MECP2 variants can produce neurological phenotypes distinct from classic RTT, including mild neurodevelopmental impairment without regression, and predominantly cerebellar or spastic-ataxic manifestations associated with limited cognitive involvement. Allelic heterogeneity seems to correlate with clinical phenotypes, at least in our small cohort. In conjunction with established diagnostic criteria, these observations support testing MECP2 in a selection of atypical neurodevelopmental and movement disorder presentations.
2026-08-10 | Translational reading frame predicts the pathogenicity of C-terminal frameshift deletions in MeCP2.
Mutations in the MECP2 gene cause the severe neurological disorder Rett syndrome. A cluster of frameshift-causing C-terminal deletions (CTDs) removes ~100 amino acids and accounts for approximately 10% of RTT-causing mutations. Their pathogenicity is unexpected because this C-terminal domain is dispensable in mice. Analysis of pathogenic and benign human MECP2 variants reveals that some individuals with apparently typical CTDs do not develop Rett syndrome, confirming that C-terminal truncations are not intrinsically pathogenic. Using human sequence data and mouse models we show that pathogenicity results from a marked reduction in MeCP2 levels and depends on the presence of a proline proline stop motif (-PPX) generated by a shift to the +2 reading frame. CTDs that shift to the +1 frame avoid this motif and are benign. Replacing the stop codon of the PPX motif with tryptophan restores MeCP2 expression and rescues RTT-like phenotypes in a CTD mouse model. An adenine base editor efficiently introduces this substitution in cultured cells. These findings define a reliable prognostic distinction between benign and pathogenic CTDs and establish a potential editing strategy for correcting disease-causing CTD mutations.
2026-07-17 | Programmable CRISPRtune dissects the transcriptional repressive activity of MeCP2.
The ability to control the expression of human genes is a major goal in synthetic biology, enables dissection of gene function, and can be harnessed for therapeutic applications. Advances in genome editing and transcriptional engineering often result in complete gene inactivation or full transcriptional repression. However, programmable tools to dial transcription at intermediate levels remain challenging. Here, we present CRISPRtune - a synthetic fusion of MeCP2 to catalytically dead dCas9 that tunes down transcription of endogenous genes in human cells by harnessing the mild repressor activity of MeCP2. Using pooled genome-scale CRISPR screens, we tune the expression of thousands of endogenous genes and define the targeting rules of CRISPRtune in human cells. With a platform to target MeCP2 at defined genomic sites, we show the direct epigenetic changes induced by MeCP2 at gene promoters and we identify its genetic dependency partners for productive transcriptional repression. Rett syndrome-associated mutations of MeCP2 show defects for transcriptional repression due to their failure to remodel the local epigenetic landscape of target genes. Together, we present a programmable method for transcriptional tuning in mammalian cells and offer an orthogonal platform to dissect the mechanistic function of chromatin regulators in living cells.
2026-06-30 | Recent advances in epigenetic therapeutics for Rett syndrome: from mechanisms to clinical trials
Rett syndrome (RTT) stands at the forefront of the genetic therapy revolution. This severe X-linked neurodevelopmental disorder, primarily caused by mutations in the MECP2 gene, was historically considered a static condition but is now recognized as a potentially reversible neurodevelopmental disorder. This review synthesizes recent breakthroughs in our understanding of MeCP2’s role in chromatin architecture, including its involvement in liquid-liquid phase separation (LLPS). We critically examine the transition from conventional symptom management to precision epigenetic therapeutics. Key advances discussed include next-generation gene replacement strategies with autoregulatory control to prevent toxicity, programmable epigenetic editing (e.g., CRISPR-off/on) to correct MECP2 expression endogenously, and novel approaches for X-chromosome reactivation (XCI). Furthermore, we propose a stratified therapeutic framework (genotype-guided therapies) based on specific mutation types. Finally, we analyze data from ongoing clinical trials and highlight the remaining hurdles—such as delivery efficiency, immunogenicity, and the urgent need for objective biomarkers—that must be overcome to translate these epigenetic innovations into a cure.
2026-04-30 | A functional MeCP2-LBX1 axis regulates neuronal gene expression in neuronal cells.
Rett syndrome is a neurodevelopmental disorder caused by mutations in MECP2 and is frequently associated with scoliosis; however, the molecular mechanisms linking MeCP2 dysfunction to this phenotype remain poorly understood. In this study, we identify LBX1, a gene implicated in adolescent idiopathic scoliosis, as a downstream target of MeCP2 and investigate its regulatory role in neuronal gene expression. Chromatin immunoprecipitation (ChIP) analysis demonstrated that MeCP2 binds to the promoter region of LBX1, which contains a CT-rich and highly methylated sequence, providing a favorable context for MeCP2 binding. Consistently, CRISPR/Cas9-mediated disruption of MECP2 in A172 cells resulted in a marked reduction of LBX1 expression, whereas expression of the antisense transcript LBX1-AS remained unchanged, indicating gene-specific regulation. These findings support a role for MeCP2 as a transcriptional activator of LBX1 in this context. Given the established role of LBX1 in specifying GABAergic and glutamatergic neuronal identities, we performed targeted gene expression profiling using a GABA and glutamate-related PCR array. Several neuronal genes were differentially expressed in MeCP2-deficient cells, and GABRB1 and P2RX7 were identified as LBX1-dependent downstream targets, as their expression levels were restored by ectopic expression of LBX1. Together, these findings reveal a previously unrecognized MeCP2-LBX1 regulatory axis and suggest that its disruption may contribute to altered neuronal signaling. This pathway provides a potential molecular link between MeCP2 dysfunction and scoliosis in Rett syndrome.
oligonucleotides
2026-09-22 | MeCP2 MBD-ID module: a unified DNA/RNA binding interface disrupted in Rett syndrome.
Rett syndrome neurodevelopmental disorder is caused by mutations in the epigenetic regulator MeCP2. While the MeCP2 methyl-CpG binding domain (MBD) is well-characterized, the function of the adjacent intervening domain (ID) remains largely understudied. The ID has been described as a distinct RNA-binding region, yet evidence also suggests RNA competitively displaces MeCP2 from DNA. Here, we address these conflicting findings by demonstrating the MBD and ID do not function in isolation but as a synergistic functional unit. The ID significantly enhances affinity of the MBD for methylated DNA by ∼35-fold. Moreover, these two subdomains form a high-affinity RNA-binding module, with preference for structured RNAs increased over 1000-fold compared to the MBD or ID alone. We find binding to RNA precludes binding to DNA, such that the integrated MBD-ID unit explains the competition phenomenon. Analysis of Rett syndrome-associated ID mutations (R167W, K174Q, and R190H) and a therapeutic MiniGene reveals they do not disrupt methyl-DNA binding but instead selectively weaken RNA and non-methylated DNA binding, thereby disrupting the competitive balance between nucleic acids. Our work establishes the MBD-ID module as MeCP2's central nucleic acid interaction hub, whose disruption provides a potential molecular etiology of Rett syndrome due to mutations in the ID.
2026-08-26 | MeCP2 Dosage Control in Rett Syndrome: Non-Coding RNA-Based and Epigenetic Strategies for Safer Gene Therapy.
Rett syndrome (RTT) is a severe X-linked neurodevelopmental disorder that is caused in most cases by pathogenic variants in MECP2, the gene encoding methyl-CpG-binding protein 2 (MeCP2). Despite substantial progress in the development of gene therapy, restoring MECP2 expression remains challenging because MeCP2 is highly dosage-sensitive. Both deficiency and excessive expression of this protein are associated with severe neurological abnormalities. This makes simple viral vector-mediated replacement of MECP2 potentially unsafe and underscores the need for multilayered systems that control transgene expression. This review discusses current and emerging strategies for regulating MeCP2 expression in RTT, with an emphasis on non-coding RNA-based and epigenetic mechanisms. Particular attention is given to the limitations of conventional AAV-mediated gene therapy, the use of cell-specific and endogenous promoters, miRNA-regulated elements, autoregulatory systems, and post-transcriptional control of MECP2 expression. Strategies for reactivating the inactive X chromosome are also discussed, including XIST-dependent regulation and epigenome editing. In addition, the review considers CRISPR-mediated regulation, selective epigenetic activation, and combined therapeutic platforms that integrate viral delivery, RNA-dependent post-transcriptional control, and endogenous gene regulation. Overall, clinically applicable gene therapy for RTT will likely need to move beyond simple MECP2 replacement and instead rely on precise cell- and dose-dependent regulation of its expression. Non-coding RNA and epigenetic mechanisms represent important layers of such control and may contribute to the development of safer gene therapy strategies for RTT.
2026-03-04 | Modulating alternative splicing of MECP2 is a potential therapeutic strategy for Rett syndrome.
Rett syndrome (RTT) is a neurological disorder caused by loss-of-function mutations in methyl-CpG-binding protein 2 (MECP2), which encodes a transcriptional regulator essential for maintenance of normal neuronal function. The current US Food and Drug Administration-approved treatment for RTT, trofinetide, mildly alleviates some symptoms. In contrast, reintroducing MeCP2 or increasing its amount through transgenesis in mouse RTT models improves most neurological phenotypes and enhances survival. Here, we devised a therapeutic strategy to moderately increase MeCP2 protein by modulating the alternative splicing of MECP2 to switch the less efficiently translated e2 to the more efficiently translated e1 isoform. We deleted Mecp2 exon 2 (unique to e2), leading to production of only e1 mRNA, and showed that this up-regulated MeCP2 by 50 to 60% in mice. Next, we investigated the consequences of isoform switching in two independent RTT induced pluripotent stem cell (iPSC)-derived neuron models harboring mutations that reduce both MeCP2 expression and function. Exon 2 deletion in neurons derived from patients with MeCP2-G118E up-regulated MeCP2, ameliorated morphological and electrophysiological changes, and corrected the dysregulated transcriptome in these neurons. Isoform switching in neurons derived from patients with MeCP2-G118E, modeling a severe RTT mutation, only modestly affected MeCP2 protein abundance and, despite this, led to a partial transcriptomic rescue. Last, an exon 2-skipping morpholino up-regulated MeCP2-E1 in vivo in mice. These data set the stage for a potential therapeutic strategy using antisense oligonucleotides to promote isoform switching in patients with RTT who carry partially functioning alleles of MECP2.
2026-02-13 | A Translational Roadmap for Neurological Nonsense Mutation Disorders.
Nonsense mutations, responsible for ~11% of gene lesions causing human monogenic diseases, introduce premature termination codons (PTCs) that lead to truncated proteins and nonsense-mediated mRNA decay (NMD). In the central nervous system (CNS), these mutations drive severe, progressive neurological conditions such as spinal muscular atrophy, Rett syndrome, and Duchenne muscular dystrophy. Readthrough therapies-strategies to override PTCs and restore full-length protein expression-have evolved from early aminoglycosides to modern precision tools including suppressor tRNAs, RNA editing, and CRISPR-based platforms. Yet clinical translation remains hampered by inefficient CNS delivery, variable efficacy, and the absence of personalized stratification. In this review, we propose a translational framework-the 4 Ds of Readthrough Therapy-to systematically address these barriers. The framework dissects the pipeline into Detection (precision patient identification and biomarker profiling), Delivery (engineered vectors for CNS targeting), Decoding (context-aware molecular correction), and Durability (long-term safety and efficacy). By integrating advances in machine learning, nanocarriers, base editing, and adaptive trial designs, this roadmap provides a structured strategy to bridge the translational gap. We advocate that a synergistic, modality-tailored approach will transform nonsense suppression from palliative care to durable, precision-based cures for once-untreatable neurological disorders.
2025-07-05 | Targeting microRNA-dependent control of X chromosome inactivation improves the Rett Syndrome phenotype.
X chromosome inactivation (XCI) is induced by Xist long non-coding RNA and protein-coding genes. However, the role of small non-coding RNA function in XCI remains unidentified. Our genome-wide, loss-of-function CRISPR/Cas9 screen in female fibroblasts identified microRNAs (miRNAs) as regulators of XCI. A striking finding is the identification of miR106a among the top candidates from the screen. Loss of miR106a is accompanied by altered Xist interactome, leading to dissociation and destabilization of Xist. XCI interference via miR106a inhibition has therapeutic implications for Rett syndrome (RTT) girls with a defective X-linked MECP2 gene. Here, we discovered that the inhibition of miR106a significantly improves several facets of RTT pathology: it increases the life span, enhances locomotor activity and exploratory behavior, and diminishes breathing variabilities. Our results suggest that miR106a targeting offers a feasible therapeutic strategy for RTT and other monogenic X-linked neurodevelopmental disorders.
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2026-08-27 | Transforming Rett Syndrome Research: Lessons from Successes and Failures in Clinical Trials
This white paper explores the evolving landscape of Rett syndrome clinical development, examining the disease biology, approved treatments, pivotal clinical trials, and key challenges in therapeutic research. The white paper highlights the significance of trofinetide (Daybue), the first FDA-approved treatment for Rett syndrome, and reviews the evidence from the Phase 3 LAVENDER study that supported its approval. It also analyzes unsuccessful development programs, including blarcamesine and sarizotan, to identify critical lessons for future studies. The paper discusses the importance of selecting appropriate endpoints such as RSBQ and CGI-I, managing placebo response, addressing small patient populations, and incorporating objective assessment tools to improve trial outcomes. Additionally, it outlines iNGENū CRO’s physician-led approach to designing FDA-ready, cost-effective clinical trials aimed at accelerating the development of innovative therapies for patients living with Rett syndrome.
2026-05-25 | The role of the gut mycobiota in neurodevelopmental disorders: a multikingdom disruption of the gut-brain axis.
Research on the gut-brain axis in neurodevelopmental disorders (NDDs) has historically focused on bacteria, overlooking fungal contributions. This review synthesizes emerging evidence to propose that intestinal fungi may actively contribute to NDD pathophysiology through multikingdom interactions, though causality requires validation. We delineate a consistent gut mycobiota dysbiosis signature across autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and Rett syndrome (RTT) characterized by reduced diversity and Candida expansion. Potential mechanisms include compromised intestinal barrier integrity, systemic immune activation via Dectin-1/Syk/CARD9 signaling, and disruption of neuroactive metabolites like short-chain fatty acids. We propose distinct etiological pathways: a "top-down" cascade in RTT, where MeCP2 mutation-induced dysmotility creates a pro-dysbiotic niche, and a "bottom-up" pathway in ASD and ADHD, where bacterial dysbiosis erodes colonization resistance, permitting fungal overgrowth. This "bacteria-fungi-host" framework provides a coherent explanation for gut-brain axis disruptions and opens avenues for biomarker discovery and multikingdom therapeutic interventions.
2025-11-15 | Harnessing the microbiota-gut-brain axis to prevent and treat pediatric neurodevelopmental disorders: translational insights and strategies.
Pediatric neurodevelopmental and neuropsychiatric disorders, including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), Rett syndrome (RTT), Tourette syndrome (TS), Down syndrome (DS), Fragile X syndrome (FXS), Prader–Willi syndrome (PWS), fetal alcohol spectrum disorder (FASD), pediatric epilepsy, congenital Zika syndrome (CZS), Wilson’s disease (WD), and cerebral palsy (CP), are associated with long-term impairments and high societal burden. Emerging evidence implicates the microbiota–gut–brain axis (MGBA) in early neurodevelopment with factors, such as maternal microbiota, birth mode, antibiotics, and infant diet shaping microbial colonization and influencing developmental outcomes. This review aims to synthesize current translational evidence from animal and human studies to address the following research questions: (1) How do disruptions in the MGBA contribute to the pathophysiology of pediatric neurodevelopmental disorders? (2) What microbiome alterations are consistently associated with these conditions? and (3) What ethical and safety considerations should be addressed in implementing early-life microbiome-based interventions? We also assess emerging microbiota-based interventions, including probiotics, prebiotics, dietary strategies, fecal microbiota transplantation, and traditional therapies, and their potential to modulate disease outcomes. The MGBA presents a promising, yet currently preliminary, target for early intervention in pediatric neurodevelopmental disorders. There is emerging evidence that therapies targeting the microbiota could have an effect on neurodevelopment and outcomes of health and disease; however, most of the findings are in the initial stages, and the evidence is still inconsistent. Therefore, the findings must be translated into mechanisms of action over extended periods with longitudinal multi-omic studies to identify possible intervention windows, optimize personalized therapies, and evaluate the safety and efficacy of interventions targeting the microbiome. Till that point, these microbiota-targeted approaches should be approached cautiously and treated as experimental in the realm of pediatric interventions, given the present-day state of evidence.
2025-02-21 | Transduction of hematopoietic stem and progenitor cells by an MECP2 lentiviral vector improves Rett syndrome phenotypes
Introduction Rett Syndrome is a genetic neurodevelopmental disorder caused by decreased levels of MeCP2. Due to mutations in the MECP2 gene, insufficient MeCP2 protein levels lead to clinical phenotypes including the loss of normal movement, decreased communication, seizures, sleep disorders, and breathing problems. Currently there is no cure for Rett Syndrome and the only means to help patients is palliative care directed to their specific symptoms. Therefore, novel therapies need to be developed to alleviate disease phenotypes by restoring normal MECP2 expression. An autologous hematopoietic stem cell and gene therapy approach for Rett syndrome may offer a benefit to affected patients by systemic delivery of functional MeCP2, including to affected neurons in the central nervous system. Methods In our current experiments, we evaluated the therapeutic effect of MECP2 lentiviral vector transduced human CD34+ hematopoietic stem and progenitor cells after transplantation into an immunodeficient mouse model of Rett syndrome. Results We observed improvement of Rett syndrome-related phenotypes including the reversion toward normal motor abilities in an open field assay for total activity, horizontal activity, and vertical rearing activity, and an increased latency to fall in a rotarod assay. An increased level of MeCP2 protein was also observed in the brain tissue of transplanted mice. Discussion By providing functional MeCP2 to affected cells, our results highlight the ability of this strategy to improve Rett syndrome phenotypes. These proof-of-concept studies demonstrate the potential use of a stem cell gene therapy approach as a novel treatment for Rett syndrome patients.
2025-01-03 | The Management of Bone Defects in Rett Syndrome.
Rett syndrome (RS) is a rare neurodevelopmental disorder primarily caused by mutations in the X-linked methyl-CpG binding protein 2 (MECP2) gene, responsible for encoding MECP2 which plays a pivotal role in regulating gene expression. The neurological and non-neurological manifestations of RS vary widely in severity depending on the specific mutation type. Bone complications, mostly scoliosis but also osteoporosis, hip displacement, and a high rate of fractures, are among the most prevalent non-neurological comorbidities observed in girls with RS. Low bone mineral density (BMD) is primarily due to a slow rate of bone formation due to dysfunctional osteoblast activity. The use of anticonvulsants, immobilization, low physical activity, poor nutrition, and inadequate vitamin D intake all significantly hamper skeletal maturation and the accumulation of bone mass in RS girls, making them more susceptible to fragility fractures. In RS patients, the upper and lower limbs are the most common sites for fractures which are due to both a reduced BMD and a diminished bone size. This review summarizes the knowledge on risk factors for fragility fracture in patients with RS and proposes a potential diagnostic and therapeutic pathway to enhance low BMD and mitigate the risk of fragility fractures. In particular, this review focused on the importance of clinical and instrumental evaluation of bone status as a basis for adequate planning of nutritional, pharmacological, and surgical interventions to be undertaken. Additionally, the management of bone defects in individuals with RS should be customized to meet each person's specific needs, abilities, and general health.
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Drug Discovery Landscape
37 orphan drug designations for Rett syndrome, including 3 approved therapies.
37 orphan drug designations for Rett syndrome, including 3 approved therapies.
Drug | Therapy type | Orphan designation | Clinical trial status | Sponsor |
|---|---|---|---|---|
recombinant serotype 9 adeno-associated virus encoding a full-length human methyl cytosine binding protein 2 (MECP2) | gene therapies | FDA | — | GeneTrek Therapeutics (Shanghai) Co., Ltd. |
(S)-1-(L-Leucyl-L-arginyl)-2-methylpyrrolidine-2-carboxamide | peptides | FDA | — | ENCUE, Inc. |
Fenfluramine hydrochloride | small molecules | EMA | UCB Pharma | |
2-[[Hydroxy[(R)-2-[((5Z,8Z,11Z,14Z)-eicosa-5,8,11,14-tetraenoyl)oxy]-3-(octadecyloxy)propoxy]phosphoryl]oxy]ethan-1-amine | small molecules | EMA | — | 3R Pharma Consulting GmbH |
Extract from Cannabis flower, containing high levels of cannabidiolic acid and <0.3% of tetrahydrocannabinol, Extraction solvent: olive oil, virgin | small molecules | EMA | — | Granzer Regulatory Consulting & Services GmbH |
CBDA dominant extract of Cannabis sativa / Low (<0.3% w/w) delta-9-tetrahydrocannabinolic acid (THC-A) and delta 9-tetrahydrocannabinol (THC) extract of Cannabis sativa with major cannabinoid constituent cannabidiolic acid (CBD-A) | small molecules | FDA | Neurotech International Limited | |
vorinostat | small molecules | FDA | Unravel Biosciences, Inc. | |
Self-complementary Adeno-Associated Virus 9 containing human methyl-CpG binding protein 2 | gene therapies | FDA | Genecombio Ltd. | |
Adeno-associated viral vector serotype 9 containing the human MECP2 gene, an intron encoding a miRNA generating sequence, and complementary miRNA binding sites | gene therapies | EMA | Eusme Limited | |
1-O-octadecyl-2-arachidonoyl-sn-glycerol-3-phosphoethanolamine | small molecules | FDA | — | Neurocores Inc. |
Recombinant serotype 9 adeno-associated virus (AAV) encoding an intron encoding a miRNA generating sequence, complementary miRNA binding sites and a full-length human methyl cytosine binding protein 2 (MECP2) | gene therapies | FDA | Neurogene Inc. | |
Ketamine | small molecules | FDA | PharmaTher Inc. | |
Methyl(R)-4-((3S,5R,7R,8R,9S,10S,13R,14S,17R)-7-hydroxy-10,13-dimethyl-3-((4-((pyridin-3-ylmethyl)amino)butyl)amino)hexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)pentanoate | small molecules | EMA | — | Maxia Strategies-Europe Limited |
methyl (R)-4-((3S,5R,7R,8R,9S,10S,13R,14S,17R)-7-hydroxy-10,13-dimethyl-3-((4-((pyridin-3- ylmethyl)amino)butyl)amino)hexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)pentanoate | small molecules | FDA | — | DepYmed, Inc. |
Adeno-associated viral vector serotype 9 containing the human MECP2 gene | gene therapies | EMA | — | Pharma Gateway AB |
Adeno-associated virus serotype 9 expressing the cDNA for human MECP2 | gene therapies | EMA | [INACTIVE] Novartis Gene Therapies EU Limited | |
recombinant serotype 9 adeno-associated virus encoding a codon-optimized human MECP2 gene | gene therapies | FDA | Taysha Gene Therapies | |
1-(2,2-diphenyltetrahydrofuran-3-yl)-N,N-dimethylmethanamine hydrochloride | small molecules | EMA | Anavex Germany GmbH | |
a non-replicating, recombinant adeno-associated virus serotype 9 (AAV9) containing the human Methyl CpG Binding Protein 2B (MECP2B) cDNA under the control of a segment of the murine MECP2 promoter. | gene therapies | FDA | Novartis Institute for BioMedical Research, Inc. | |
Mercaptamine-pantetheine disulfide | small molecules | EMA | — | Thiogenesis Therapeutics S.A.R.L |
tianeptine | small molecules | FDA | — | AMO Pharma Ltd. |
Cannabidivarin | small molecules | EMA | — | Jazz Pharmaceuticals Ireland Limited |
[(S)-1-(L-valyl)-N_((S)-1-phenyl-2-(pyridin-2-yl)ethyl)pyrrolidine-2-carboxamide fumarate] | small molecules | FDA | — | Biohaven Pharmaceutical Holding Company, Ltd. |
cannabidivarin | small molecules | FDA | — | Jazz Pharmaceuticals Research UK Limited |
6'-(R)-Methyl-5-O-(5-amino-5,6-dideoxy-a-L-talofuranosyl)- paromamine sulfate | small molecules | FDA | — | Eloxx Pharmaceuticals, Ltd. |
(2,2-diphenyl-tetrahydro-furan-3-yl-methyl)-dimethylamine hydrochloride | small molecules | FDA | Anavex Life Sciences Corporation | |
mecasermin, recombinant human insulin-like growth factor-1 | proteins | FDA | Keck Graduate Institute of Applied Life Sciences | |
Glycyl-L-2-methylprolyl-L-glutamic acid [Daybu] | small molecules | EMA | Approved | Acadia Pharmaceuticals (Netherlands) B.V. |
Sarizotan hydrochloride | small molecules | EMA | Newron Pharmaceuticals SpA | |
sarizotan | small molecules | FDA | Newron Pharmaceuticals US, Inc. | |
trofinetide [Daybue] | small molecules | FDA | Approved | ACADIA Pharmaceuticals Inc. |
trofinetide [Daybue Stix] | peptides | FDA | Approved | ACADIA Pharmaceuticals Inc. |
vatiquinone | small molecules | FDA | PTC Therapeutics, Inc. | |
3-Chloro-4-fluorophenyl-[4-fluoro-4-{[(5-methylpyrimidin-2-ylmethyl) amino]methyl}piperidin-1-yl]methanone | small molecules | EMA | — | Neurolixis SAS |
3-chloro-4-fluorophenyl-[4-fluoro-4-[[(5-methylpyrimidin-2-ylmethyl)amino]methyl]piperidin-1yl]methanone | small molecules | FDA | — | Neurolixis, Inc. |
acetyl-l-carnitine (ALC) | small molecules | FDA | — | Leadiant Biosciences, Inc. |
Desipramine hydrochloride | small molecules | EMA | [INACTIVE] Orphelia Pharma |
“Terminated” – programs with discontinued clinical trials, or with no updates reported for 5 years after completion or 12 years after the last trial started.
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