Aromatic l-amino acid decarboxylase deficiency: a patient-derived neuronal model for precision therapies.

Aromatic l-amino acid decarboxylase (AADC) deficiency is a complex inherited neurological disorder of monoamine synthesis which results in dopamine and serotonin deficiency. The majority of affected individuals have variable, though often severe cognitive and motor delay, with a complex movement disorder and high risk of premature mortality. For most, standard pharmacological treatment provides only limited clinical benefit. Promising gene therapy approaches are emerging, though may not be either suitable or easily accessible for all patients. To characterize the underlying disease pathophysiology and guide precision therapies, we generated a patient-derived midbrain dopaminergic neuronal model of AADC deficiency from induced pluripotent stem cells. The neuronal model recapitulates key disease features, including absent AADC enzyme activity and dysregulated dopamine metabolism. We observed developmental defects affecting synaptic maturation and neuronal electrical properties, which were improved by lentiviral gene therapy. Bioinformatic and biochemical analyses on recombinant AADC predicted that the activity of one variant could be improved by l-3,4-dihydroxyphenylalanine (l-DOPA) administration; this hypothesis was corroborated in the patient-derived neuronal model, where l-DOPA treatment leads to amelioration of dopamine metabolites. Our study has shown that patient-derived disease modelling provides further insight into the neurodevelopmental sequelae of AADC deficiency, as well as a robust platform to investigate and develop personalized therapeutic approaches.

Transplant eligibility in elderly multiple myeloma patients: Prospective external validation of the international myeloma working group frailty score and comparison with clinical judgment and other comorbidity scores in unselected patients aged 65-75 years.

Autologous stem cell transplantation (ASCT) is feasible and effective in selected older patients with Multiple Myeloma, but specific criteria for evaluating ASCT eligibility in elderly patients are lacking. We evaluated 131 patients aged 65-75 considered for ASCT at our center: The Charlson Comorbidity Index (CCI), Hematopoietic cell transplantation comorbidity index (HCT-CI) and IMWG frailty score were obtained at diagnosis, but the intensity of treatment was left to physician's choice. The scores and age's impact on outcome was analyzed: 85 patients were judged transplant eligible, whereas 46 patients received a less intensive treatment (median follow up 27 months). No patients classified as frail had been considered eligible to ASCT with a worse outcome compared to fit and unfit patients (median PFS (progression free survival): 7.9 vs 32.9 and 29.6 months; P < .001). PFS was superior in the ASCT group (35.6 vs 19.9 months, P .013). In the ASCT group, PFS was better in patients aged 65-69 years than in patients ≥70 (51.5 vs 27.7 months, P.004). Indeed, in unfit patients aged ≥70 the PFS of the ASCT group was comparable to NO ASCT group (18 vs 27 months, P = .33) whereas in unfit patients aged 65-69 PFS was superior in the ASCT group: 43.3 vs 18.4 months, P .01. ISS III and impaired functional status independently affected PFS in a multivariate analysis (P .011 and P .006). While CCI and HCT-CI did not predict different outcome in ASCT patients, the IMWG frailty score would be of help in identifying unfit patients aged 70-75, whose outcome with ASCT selected by clinical judgment was no better than with less intensive treatments.

Gene therapy restores dopamine transporter expression and ameliorates pathology in iPSC and mouse models of infantile parkinsonism.

Most inherited neurodegenerative disorders are incurable, and often only palliative treatment is available. Precision medicine has great potential to address this unmet clinical need. We explored this paradigm in dopamine transporter deficiency syndrome (DTDS), caused by biallelic loss-of-function mutations in SLC6A3, encoding the dopamine transporter (DAT). Patients present with early infantile hyperkinesia, severe progressive childhood parkinsonism, and raised cerebrospinal fluid dopamine metabolites. The absence of effective treatments and relentless disease course frequently leads to death in childhood. Using patient-derived induced pluripotent stem cells (iPSCs), we generated a midbrain dopaminergic (mDA) neuron model of DTDS that exhibited marked impairment of DAT activity, apoptotic neurodegeneration associated with TNFα-mediated inflammation, and dopamine toxicity. Partial restoration of DAT activity by the pharmacochaperone pifithrin-µ was mutation-specific. In contrast, lentiviral gene transfer of wild-type human SLC6A3 complementary DNA restored DAT activity and prevented neurodegeneration in all patient-derived mDA lines. To progress toward clinical translation, we used the knockout mouse model of DTDS that recapitulates human disease, exhibiting parkinsonism features, including tremor, bradykinesia, and premature death. Neonatal intracerebroventricular injection of human SLC6A3 using an adeno-associated virus (AAV) vector provided neuronal expression of human DAT, which ameliorated motor phenotype, life span, and neuronal survival in the substantia nigra and striatum, although off-target neurotoxic effects were seen at higher dosage. These were avoided with stereotactic delivery of AAV2.SLC6A3 gene therapy targeted to the midbrain of adult knockout mice, which rescued both motor phenotype and neurodegeneration, suggesting that targeted AAV gene therapy might be effective for patients with DTDS.