Diverse Strategies to Correct the Dystrophin Gene Using Vascular Delivery (U54)

点击翻译按钮获取中文摘要

The premise for this U54 gene therapy proposal is that clinically meaningful results can be achieved by vascular delivery in patients with Duchenne muscular dystrophy (DMD). Discussions with FDA indicate that this will move forward in a stepwise fashion whereby regional vascular delivery will precede systemic vascular delivery for clinical trials. Our proposal revolves around this central point and gene delivery to the legs through the femoral artery is the starting place. In project 1, rAAV.micro-dystrophin will be used to restore the missing dystrophin protein. In project 2, a novel gene, CT GalNAc transferase (also called GALGT2) will be delivered by AAV. Both approaches, through entirely different mechanisms, reinforce the weakened muscle membrane, responsible for progressive muscle fiber damage and loss with replacement by fat and connective tissue. The studies presented in this proposal will take the first steps leading to a clinical trial through a vascular route. There are several considerations addressed in this U54 that must be resolved before application for IND, including method of delivery and immunogenicity of the virus and its cargo. We will study this in the rhesus macaque, an ideal system with close homology to the human anatomically and in the immune system. We will use rAAV8, a viral serotype that we found crosses the vascular barrier in both small and large animal species, setting the stage for the monkey studies. In addition, we can deliver this serotype with and without pre-exising immunity to AAV8 by pre-screening for neutralizing antibodies. We can also test various immunosuppressive protocols to establish if immune suppression will be necessary for gene transfer in patients (as predicted by the human gene transfer studies with factor IX). The monkey also provides a vascular route of entry that closely simulates that which we will encounter clinically. Thus, we will deliver rAAVS carrying micro-dystrophin or GALGT2 in a compartmentalized system through a balloon catheter to provide safe passage for the virus and to protect the host from spread of virus to unwanted targets. Upon completion of these studies we will have enough information to apply to FDA for an IND for both of these promising products. We feel that both should be carried forward to the clinic, each very promsing in its own right. Completion of phase I safety trials for both of these gene therapy approaches opens the gate for further vascular delivery leading to clinically meaningful results for patients.