These micro-dystrophin and utrophin chimeric constructs optimize the treatment of Duchenne Muscular Dystrophy (DMD). DMD is a rare, X-chromosome-linked disorder characterized by progressive muscle degeneration and weakness. Expression of the dystrophin protein is in skeletal, smooth, and cardiac muscle, and mutations in the gene encoding cause DMD. Severe Duchenne cases present total loss of dystrophin from skeletal and cardiac muscles, leading to debilitating muscle degeneration and, ultimately, heart failure. The utrophin protein is highly related to dystrophin and can substitute for dystrophin’s function in mammals. Typically, utrophin is highly expressed in developing muscles and enriches at the neuromuscular junction in mature muscles. As myofibers mature, utrophin levels decrease and express dystrophin.
Gene replacement therapy is the most active and available therapy for DMD. This strategy involves the delivery of a functional dystrophin copy to the patient using viral delivery vectors. However, these vectors have limited carrying capacity, and the large size of dystrophin depicts a compatibility challenge, leading to the need for micro-dystrophin-based gene therapy with a truncated but functional version of dystrophin. While there are ongoing clinical trials implementing these strategies, these therapies are optimized for skeletal muscle without enough evaluation of the clinical impact on cardiac function. This may lead to a form of DMD with severe cardiomyopathy and slowly failing skeletal muscle function as a long-term consequence. Additionally, adverse effects in these clinical trials are present due to neoantigens found in patients with dystrophin isoforms lacking gene regions present in the clinical trial isoforms.
Researchers at the University of Florida have designed micro-dystrophin and utrophin chimeric constructs for treating Duchenne Muscular Dystrophy (DMD) and avoiding micro-dystrophin-associated neoantigen presentation. The utrophin N-terminus replaces the dystrophin N-terminus, reducing the immune response in patients and rescuing the heart and diaphragm muscle without an immune response. The constructs include promoters specific for skeletal or cardiac muscles for enhanced effectivity.
Tissue-specific delivery and expression of micro-dystrophin and utrophin chimeric constructs for the treatment of Duchenne Muscular Dystrophy
These micro-dystrophin and utrophin chimeric nucleic acid constructs provide effective Duchenne Muscular Dystrophy (DMD) treatment. The micro-dystrophin and utrophin sequence combinations enable the replacement of immunogenic micro-dystrophin gene regions with the utrophin equivalent, reducing the risk for neoantigen presentation. Additionally, the constructs have promoters specific to either the skeletal or cardiac muscles and recombinant adeno-associated viral vectors (rAAVs) deliver them to either tissue for targeted or optimized expression of the chimeric proteins in each tissue. More specifically, delivery to a subject consists of a first rAAV comprising a chimeric construct linked to a cardiac muscle-specific promoter to the cardiac muscle and a second rAAV comprising a chimeric construct linked to a skeletal muscle-specific promoter to the skeletal muscle. Delivery of the rAAV particles involves introducing a catheter into the femoral artery and advancing to the heart for delivery of the first rAAV into the coronary arteries (cardiac muscle), and then retracting the catheter to the aortic arch for delivery of the second rAAV to the subclavian and carotid arteries (skeletal muscle). This strategy enables the treatment of each specific tissue independently and efficiently.
