RESUMO
X-linked myotubular myopathy (XLMTM) results from MTM1 gene mutations and myotubularin deficiency. Most XLMTM patients develop severe muscle weakness leading to respiratory failure and death, typically within 2 years of age. Our objective was to evaluate the efficacy and safety of systemic gene therapy in the p.N155K canine model of XLMTM by performing a dose escalation study. A recombinant adeno-associated virus serotype 8 (rAAV8) vector expressing canine myotubularin (cMTM1) under the muscle-specific desmin promoter (rAAV8-cMTM1) was administered by simple peripheral venous infusion in XLMTM dogs at 10 weeks of age, when signs of the disease are already present. A comprehensive analysis of survival, limb strength, gait, respiratory function, neurological assessment, histology, vector biodistribution, transgene expression, and immune response was performed over a 9-month study period. Results indicate that systemic gene therapy was well tolerated, prolonged lifespan, and corrected the skeletal musculature throughout the body in a dose-dependent manner, defining an efficacious dose in this large-animal model of the disease. These results support the development of gene therapy clinical trials for XLMTM.
Assuntos
Dependovirus/genética , Terapia Genética , Vetores Genéticos/genética , Músculo Esquelético/metabolismo , Miopatias Congênitas Estruturais/genética , Animais , Biópsia , Dependovirus/classificação , Modelos Animais de Doenças , Progressão da Doença , Cães , Marcha , Expressão Gênica , Terapia Genética/efeitos adversos , Terapia Genética/métodos , Vetores Genéticos/administração & dosagem , Vetores Genéticos/efeitos adversos , Vetores Genéticos/farmacocinética , Imunidade Celular , Imunidade Humoral , Estimativa de Kaplan-Meier , Força Muscular , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Músculo Esquelético/ultraestrutura , Miopatias Congênitas Estruturais/diagnóstico , Miopatias Congênitas Estruturais/mortalidade , Miopatias Congênitas Estruturais/terapia , Proteínas Tirosina Fosfatases não Receptoras/genética , Recuperação de Função Fisiológica , Reflexo , Testes de Função Respiratória , Distribuição Tecidual , Transgenes/genética , Transgenes/imunologia , Resultado do TratamentoRESUMO
INTRODUCTION: X-linked myotubular myopathy (XLMTM), a devastating pediatric disease caused by the absence of the protein myotubularin, results from mutations in the MTM1 gene. While there is no cure for XLMTM, we previously reported effects of MTM1 gene therapy using adeno-associated virus (AAV) vector on muscle weakness and pathology in MTM1-mutant dogs. Here, we followed 2 AAV-infused dogs over 4 years. METHODS: We evaluated gait, strength, respiration, neurological function, muscle pathology, AAV vector copy number (VCN), and transgene expression. RESULTS: Four years following AAV-mediated gene therapy, gait, respiratory performance, neurological function and pathology in AAV-infused XLMTM dogs remained comparable to their healthy littermate controls despite a decline in VCN and muscle strength. CONCLUSIONS: AAV-mediated gene transfer of MTM1 in young XLMTM dogs results in long-term expression of myotubularin transgene with normal muscular performance and neurological function in the absence of muscle pathology. These findings support a clinical trial in patients. Muscle Nerve 56: 943-953, 2017.