Advancing AADC deficiency therapy through MR-guided multisite delivery of AAV2-hAADC to dopaminergic and serotonergic pathways in the brainstem

Adeno-associated virus (AAV) vectors have taken center stage for gene therapy and have shown clinical efficacy in 15 human diseases to date. The Food and Drug Administration has approved seven AAV "drugs" for one-time treatment respectively for Leber's congenital amaurosis, spinal muscular atrophy, hemophilia B, Duchenne muscular dystrophy, hemophilia A, and aromatic L-amino acid decarboxylase deficiency. Despite these remarkable developments, it has become increasingly clear that the first generation of AAV vectors is less than optimal since in most, if not all, cases, exceedingly high doses are needed to achieve clinical efficacy, and as a consequence, in some patients, serious adverse events have been observed, and to date, at least 21 patients have died. Thus, there is a need to reassess the limitations of the first generation of AAV vectors as well as an urgent need to develop the next generation of AAV vectors that are safe and effective.

Adeno-associated viral vectors have proven to be a safe and effective gene therapy delivery system. Over the past decade, the approval of AAV gene therapies made a revolution in treatment of severe hereditary diseases, including spinal muscular atrophy, AADC deficiency, and others. Recombinant AAV-based therapeutics are currently intended for single administration. Safety concerns arise from immune responses to AAV and the resulting transgene, which can render subsequent injections ineffective. It remains unclear whether patients who have received an AAV-based gene therapy will need re-administration in the future. Furthermore, since many people have neutralizing antibodies or memory T cells against AAV from natural infections, it is crucial to overcome pre-existing immunity. This review considers existing modern approaches aimed to overcome both pre-existing natural immunity and immunity obtained after the administration of a gene therapy drug, which include various modifications of the viral drug (capsid modification, codon optimization), the use of empty capsid traps, and pharmacological support (immunosuppressive corticosteroids, inhibitors of various branches of the immune response, nanoparticles, IgG-degrading enzymes). The goal of this review is to illustrate the importance of this challenge and to highlight potential strategies for overcoming immunity to AAV-based gene therapies, contributing to the development of a successful therapeutic gene delivery platform.

Treatable and preventable causes of inborn errors of metabolism: Cohort of neurotransmitter disorders in children from India.

Recently, the gene therapy eladocagene exuparvovec received accelerated approval from the US Food and Drug Administration (as eladocagene exuparvovec-tneq) for treatment of aromatic L-amino acid decarboxylase deficiency (AADCd), a rare, infantile-onset disorder characterized by developmental delays. To conduct a US, modified societal perspective cost-utility analysis comparing eladocagene exuparvovec versus best supportive care (BSC). Multistate survival modeling was implemented tracking disease progression from a "no motor function" health state to achievement of motor-function improvements, measured by: (1) multiples of the meaningful score difference (MSD) of the Peabody Developmental Motor Scales-Second Edition (PDMS-2) total score and (2) motor milestones. Eladocagene exuparvovec trials informed clinical inputs. Health-state utilities were from a US time-trade-off study that valued AADCd quality-of-life impacts. Outcomes were discounted (3%); costs were reported in 2024 US dollars. Scenario analyses, characterizing alternative approaches of the multistate survival model analyses and probabilistic sensitivity analysis to assess the impact of parameter uncertainty, were conducted. Discounted incremental quality-adjusted life-years (QALYs) for eladocagene exuparvovec were 20.83 (multiples of the MSD of total PDMS-2) and 18.44 (motor milestones). Incremental cost per QALY ranged from $199,007-$224,104. The scenario and sensitivity analyses results supported the validity of the base case analysis. Eladocagene exuparvovec is associated with considerable QALY gains compared with BSC. Within the context of other ultra-rare and/or one-time treatments, eladocagene exuparvovec provides substantial clinical improvements at lower cost than many other rare-disease treatments. Findings from this study highlight that eladocagene exuparvovec is an important treatment option for patients with AADCd.

The CRISPR-Cas9 dopa decarboxylase (DDC) gene knockout SH-SY5Y model for aromatic L-amino acid decarboxylase (AADC) deficiency provides a valuable neuronal platform for functional and structural investigation of pathogenic variants. In their study, Bertoldi etal. successfully recapitulate the biochemical and metabolic hallmarks of AADC deficiency using the AADC catalytic variants R347Q and L353P. Their combined structural and cellular approach identifies loop3 dynamics as a critical determinant of enzymatic dysfunction. This model may pave the way for the development of precision therapies.

EE402 Cost-Effectiveness Analysis of Eladocagene Exuparvovec-tneq for Aromatic L-Amino Acid Decarboxylase Deficiency (AADC-D) and Comparison with Other Rare Disease One-Time Treatments in the United States

Genetic dystonias are a heterogeneous group of movement disorders characterized by involuntary, sustained muscle contractions that cause repetitive movements and abnormal postures. Often beginning in childhood, they can significantly affect quality of life. Although individually rare, genetic causes are collectively relevant in pediatric dystonias, with over 250 associated genes. Among these, TOR1A, SGCE, and KMT2B are the most frequently reported in pediatric forms. Diagnosis is challenging due to the wide clinical and genetic variability. Recent advances in genetic testing, including whole-exome and whole-genome sequencing, have improved the early identification of causative variants. Functional data on selected mutations are helping to refine genotype-phenotype correlations. Management typically requires a multidisciplinary approach. Symptomatic treatments include anticholinergics, benzodiazepines, and botulinum toxin, while deep brain stimulation can be effective in refractory cases, especially in patients with TOR1A variants. Disease-modifying therapies are also emerging, such as gene therapy for AADC deficiency, highlighting the potential of precision medicine. This review provides an updated overview of pediatric genetic dystonias, with a focus on differential diagnosis and treatment strategies. Early and accurate diagnosis, together with personalized care, is key to improving outcomes in affected children.

Aromatic amino acid decarboxylase (AADC) deficiency is a severe inherited recessive neurotransmitter disorder caused by an impairment in dopamine synthesis due to the lack/modification of AADC, the enzyme converting l‐dopa to dopamine. Patients exhibit severe movement disorders and neurodevelopmental delay, with a high risk of premature mortality. Given the lack of a reliable model for the disease, we developed a dopa decarboxylase knockout model using CRISPR/Cas9 technology in the SH‐SY5Y neuroblastoma cell line. This model showed a deficiency in AADC protein and activity, with an altered dopamine metabolites profile (low homovanillic acid and high 3‐O‐methyldopa) and a modified expression of key enzymes, such as dopamine beta‐hydroxylase and monoamine oxidases, which are involved in the catecholamine pathway. We then transfected the DDC‐KO cells with two AADC catalytic variants, R347Q and L353P, which resulted in loss‐of‐function and an altered profile of dopamine metabolites. By combining several structural approaches (X‐ray crystallography, molecular dynamics, small angle X‐ray scattering, dynamic light scattering, and spectroscopy), we determined that both variants alter the flexibility of the structural element to which they belong, whose integrity is essential for catalysis. This change causes a mispositioning of essential residues at the active site, leading, in turn, to an unproductive external aldimine, identifying the molecular basis for the loss‐of‐function. Overall, the DDC‐KO model recapitulates some key features of AADC deficiency, is useful to study the molecular basis of the disease, and represents an ideal system for small molecule screening regarding specific enzyme defects, paving the way for a precision therapeutic approach.

Early detection of rare diseases is one of the ongoing challenges in clinical practice because their prevalence is low, presentations are heterogeneous, and their diagnoses are complex. In this work, we introduce a new deep learning approach based on a Hierarchical Temporal Transformer (HTT) to detect rare diseases from clinical multi-dimensional patient data stored in electronic health records (EHR). Our model is tailored to recognize complex patterns in patient data over time and overcome extreme class imbalance by introducing a focal loss function. We perform an extensive comparison with conventional machine learning and deep learning baselines on three big-scale real-world EHR datasets covering over 170,000 patients with multiple rare diseases like Gaucher, ALS, and AADC deficiency. Our model outperforms baselines with a significant margin with an F1-score of 0.69, AUC of 0.89, and detects disease up to 12 days in advance of clinical detection. Our model models generalize well across datasets from other institutions and shows stable, balanced performance across demographic sub-populations. Besides predictive performance, the model provides clinical interpretability in the form of its temporal attention mechanism to flag medical relevant features (e.g., splenomegaly, thrombocytopenia) that are known to be associated with disease. An exhaustive ablation study also ensures the contribution of the key architectural elements such as hierarchical embedding and positional encodings. Our work shows the potential of deep learning in diagnosing rare diseases early and indicates the clinical utility of interpretable AI in clinical care in real-world healthcare. Our proposed model is a transferable and scalable solution that can facilitate early intervention and reduce the delay in diagnostics and improve the treatment of people with rare diseases

BackgroundAromatic L-amino acid decarboxylase deficiency (AADCd) is a rare genetic disorder characterized by movement disorders, motor and autonomic dysfunction, and developmental delays. The gene therapy eladocagene exuparvovec has become available in some regions; pooled clinical trial results demonstrate continuous long-term improvement in motor development and cognitive function. We sought to characterize clinically meaningful change in motor function, as measured by Total Peabody Developmental Motor Scales-Second Edition (PDMS-2) score, and assess correlations with cognition and language domains of the Bayley-III and motor milestone (MM) achievement.MethodsData from N = 30 patients from three single-arm clinical studies of eladocagene exuparvovec were analyzed. Anchor-based estimation of the meaningful score difference (MSD) of Total PDMS-2 score was conducted using mean-difference and receiver operating characteristic curve (ROC) approaches. MM achievement served as the anchor defining meaningful change.ResultsAn MSD of 40 points for Total PDMS-2 score was selected for analysis as it yielded specificity > 0.95 using the ROC approach, and generally aligned with the mean-difference approach. Cumulative incidence analysis reflected that 50% of patients treated with eladocagene exuparvovec may achieve the MSD of 40-point change in Total PDMS-2 score at 6 months, and 86% at 18 months. Correlations between measures were of large magnitude and improved over time (Month 6: r = 0.599 [p = 0.0032]; Month 18: r = 0.796 [p = 0.0002]; Month 60: r = 0.861 [p = 0.0007]).ConclusionsThe MSD of 40 points for Total PDMS-2 score enables the interpretation of changes observed in patients with AADCd, and suggests that treatment with eladocagene exuparvovec leads to significant improvements in motor and cognitive function.

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare life-threatening inborn error of neurotransmitter biosynthesis. It is characterized by deficient biosynthesis of neurotransmitters dopamine and serotonin, leading to catecholamines deficiency and sympathetic deprivation, while the parasympathetic system remains functional. Since 2012, gene therapy has led to clinical improvements in symptoms and motor function with a severe phenotype. General anesthesia of children with AADC deficiency is challenging. Describe prolonged anesthesia management of children with aromatic L-amino acid decarboxylase deficiency undergoing stereotactically guided gene therapy. Prospective reporting of epidemiologic and anesthetics data of four children consecutively undergoing magnetic resonance-guided direct delivery of an AADC vector for gene therapy under general anesthesia. General anesthesia was initiated with sevoflurane and ketamine and rocuronium was the neuromuscular blocking agent of choice throughout the procedures. Intraoperative hemodynamic monitoring included an arterial line. All children required low doses of diluted norepinephrine during the intraoperative period. No dysautomic episodes as well as no episode of severe hypotension and no severe hypoglycemia were reported throughout the procedures. Vasopressor support was discontinued for all children at the end of the procedures. Moreover, no peroperative and postoperative effects secondary to AADC vector injection were noted. Using an anesthetic plan based on atropine, ketamine, sevoflurane, and a titrated infusion of norepinephrine, prolonged anesthesia appeared to be safe and reproductible in this population.

BackgroundAADCd is a rare neurometabolic disorder presenting in infancy. Children with AADCd have motor dysfunction and development delays that result in the need for lifelong care; quality of life is greatly impacted. Current characterizations of health-related quality of life and associated health state utilities (HSUs) may be underestimated in AADCd. Accurate characterization of AADCd burden is important when evaluating the benefits of treatment, especially the improvements observed with the recently approved disease-modifying therapy eladocagene exuparvovec. Time-trade-off (TTO) vignette methods may be used to elicit HSUs in AADCd for assessing the value of new treatments. This study aimed to first update previously published health state vignettes, then estimate AADCd HSUs in the United States (US).MethodsExisting vignettes for five AADCd health states were updated based on the review of published literature and clinician/caregiver input. Health states included: “bedridden/no motor function,” “head control,” “sitting unassisted,” “standing with support,” “walking with assistance.” Online composite TTO interviews were conducted 1:1 with adults from the US general public. Participants ranked health states in order of preference using a visual analog scale, then were presented with health state vignettes to elicit utilities using TTO. Mean TTO scores were calculated for each health state, and regression models were used to estimate disutility associated with use of feeding tube.ResultsFollowing revision of the vignettes, 120 participants completed the TTO task (mean age: 47 years; 50% female; 70% White); characteristics were not significantly different from US population norms in terms of age, sex, race or ethnicity. Six participants who appeared to misunderstand the exercise were excluded. Mean (SD) HSUs were: -0.258 (0.534) for bedridden state, -0.155 (0.569) for head control, 0.452 (0.523) for sitting unassisted, 0.775 (0.242) for standing with support, and 0.796 (0.235) for walking with assistance. The need for a feeding tube was associated with a disutility of 0.07.ConclusionsThis study implemented TTO methods to estimate utilities for five health states which reflect the burden and impact of AADCd. The range in values from the most to least severe health state suggests that there is potential for effective treatments to substantially improve quality of life in these patients.

PurposeWe present two clinical cases of frameless, neuronavigated gene therapy with eladocagene exuparvovec for aromatic L-amino acid decarboxylase (AADC) deficiency in pediatric patients, detailing the targeted bilateral microdose delivery of viral vectors into the putamen and highlighting the feasibility and challenges of this approach in managing a rare neurometabolic disorder.MethodsTwo patients with a confirmed diagnosis of AADCD underwent frameless stereotactic gene therapy. High-resolution 3 T MRI-guided trajectories were planned for the targeted bilateral putaminal infusion of 0.32 ml of eladocagene exuparvovec (AAV2-hAADC). The agent was delivered via a SmartFlow Neuro Ventricular Cannula in a “Z-pattern,” retracting the cannula 2 mm every 9 min to achieve controlled microdosing.ResultsAccurate frameless drug delivery was achieved in a shorter time than frame-based approaches, with no intraoperative or postoperative complications. One patient showed a small post-ischemic cyst on the 1-month follow-up MRI, without any neurological deficits. Over 2 months, both patients demonstrated reduced oculogyric crises, diminished hyperkinesis, and improved head control, with no significant adverse events.ConclusionFrameless, neuronavigated gene therapy for AADC deficiency proved both feasible and safe, with early clinical improvements observed in motor function and symptom control. This technique offers a promising alternative to frame-based methods and expands treatment options for this rare neurometabolic disorder.

Background: The main objective of this prospective, multicenter study (REVEAL-CP) was to test children with cerebral palsy-like signs and symptoms for raised 3-O-methyldopa (3-OMD) blood levels, a biomarker for aromatic L-amino acid decarboxylase deficiency (AADCd). A secondary objective was to characterize the molecular basis for the defective aromatic L-amino acid decarboxylase (AADC) gene product. Methods: Patients were identified in pediatric secondary and tertiary care hospitals through database searches and personal communication. 3-OMD concentrations from Guthrie card tests were determined using liquid chromatography/mass spectrometry. If 3-OMD was raised, cerebrospinal fluid analysis and dopa decarboxylase (DDC) gene sequencing were performed. An in-silico mutagenesis analysis was carried out to model altered AADC enzymes. Results: In total, 166 patients were enrolled in this study. The median age was 8 years. Sixty-six patients (39.8%) had a diagnosis of cerebral palsy, with the most common type being "mixed" (n = 42; 25.3%). One patient (0.6%), an 11-month-old boy from Italy, was diagnosed with AADCd caused by a homozygous, pathogenic DDC variant (c.749C>T; p.Ser250Phe). Three-dimensional modeling of the Ser250Phe AADC enzyme variant revealed its destabilization. Conclusions: A Guthrie card test for 3-OMD is a recognized screening technique for AADCd. If universal newborn screening for this metabolic disease is not available, children with signs and symptoms of a movement disorder should be investigated for AADCd.

Interrogation of coded healthcare data to facilitate identification of patients with a rare neurotransmitter disorder; Aromatic L-Amino acid decarboxylase deficiency

Parkinson's Disease (PD), a progressive neurodegenerative disorder characterized by dopaminergic neuron degeneration, leads to motor and non-motor symptoms that significantly impair quality of life. Conventional treatments, such as levodopa, provide symptom relief but are associated with long-term complications and do not halt disease progression. This review systematically evaluates the efficacy and safety of gene therapy targeting the aromatic L-amino acid decarboxylase (AADC) enzyme in treating PD and AADC deficiency, focusing on sustained dopamine production and motor function improvement. A systematic literature review was conducted using databases like PubMed, Scopus, and Embase, covering studies published over the past 32 years. Out of 52 articles identified, 25 met inclusion criteria, providing data on motor outcomes, dopamine production, and safety profiles. Findings suggest that AADC gene therapy may offer a durable therapeutic approach, reducing reliance on conventional dopamine replacement therapies and mitigating related complications. This review highlights gene therapy's potential in clinical practice, emphasizing a shift towards targeted treatment strategies for dopamine-deficient neurodegenerative disorders. Further research should address long-term efficacy and safety across diverse patient groups. Limitations include potential selection bias and language restrictions.

Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare autosomal recessive disorder that results in a lack of the monoamine neurotransmitters dopamine, serotonin, norepinephrine, and epinephrine. Patients present with a wide spectrum of symptoms, including motor and autonomic dysfunction, hypotonia, and developmental delay, often before the age of one. Until recently, treatment options were limited to symptom control, but the recent approval of the first gene therapy for AADC deficiency in Europe and the UK has provided an alternative to treating symptoms for this disease. Eladocagene exuparvovec is a one-time gene therapy, administered bilaterally to the putamen by magnetic resonance imaging-guided stereotactic neurosurgery. While administration of the gene therapy itself is minimally invasive, the anesthetic management of patients with AADC deficiency is challenging due to the absence of sympathetic regulation secondary to the lack of adrenergic neurotransmitters. Optimal anesthetic management requires an understanding of the complex and heterogeneous nature of the disease. Hemodynamic instability, temperature dysregulation, and hypoglycemia are of primary concern, but there are also challenges regarding intravenous access and airway management. A thorough preoperative assessment is essential and should be guided by the patient's history. Advanced planning is necessary regarding the timing of the procedure schedule and operative plan; meticulous preparation, simulation for the operating room, as well as communication with all perioperative staff members, are crucial. Intraoperatively, utmost care must be taken to protect the skin, maintain body temperature, and to prepare for inotropic and/or glycemic support as needed. Postoperative intensive care management is necessary for consideration of postoperative extubation and provision of supportive care. With careful planning, preparation, and vigilance, patients with AADC deficiency can safely undergo anesthesia.

Nigrostriatal tract defects in mice with aromatic l-amino acid decarboxylase deficiency

Diagnosis of aromatic L-amino acid decarboxylase deficiency via neurodevelopmental disorder gene panel screening in a patient with atypical presentation