Familial hypercholesterolemia (FH) is an autosomal dominant genetic disease characterized by severely elevated plasma low-density lipoprotein (LDL) cholesterol (LDL-C) and premature coronary heart disease. Most of FH patients (about 95% of cases) are attributed to functional loss mutation of the LDL receptor (LDLR) gene. The prevalence of the heterozygous mutations in LDLR has been estimated at 1 in 200 to 1 in 500 in the population, and the homozygous form in 1 in 100000 individuals. As a key lipoprotein receptor on the surface of hepatocyte, the LDLR is critical for liver clearing LDL-C from the circulation. By endocytosis and further processing of the LDL-C, LDLR is responsible for removing most excess LDL-C from the serum, and there are no substitutes in vivo. These heterozygotes (HeFH) typically have twice the normal plasma LDL levels and cardiovascular diseases at an earlier age. Homozygous individuals (HoFH) face much higher LDL-C levels and often die before the age of 20 years if untreated. Although existing therapeutics, such as statins, ezetimibe and PCSK9 inhibitors, have some beneficial effects on HeFH, few drugs have therapeutic effects on HoFH even at high-doses. Lipid apheresis and liver transplantation are the current clinical managements to reduce the LDL-C level, while gene therapy holds the promise.~Exosomes are small intracellular vesicles ranging in 30-150 nm size and have an important role in cell-cell communication. Many studies show that exosome can efficiently deliver cargos, such as mRNA, miRNA and even plasmid DNA, to target cells, emerging as a promising therapeutic carrier for gene therapy. Compared with virus, exosomes, as natural nanoparticles, are easy to handle, non-cytotoxic and non-immunogenic. It is thus promising to develop exosome-based LDLR-gene delivery strategy and explore the therapeutic effects on HoFH.~In this study, an Ldlr-expressing virus vector will be constructed to generate Ldlr mRNA-enriched exosomes. To meet the standards of clinical trials, we will use the GMP-grade compliant normal donor bone marrow-derived MSCs to produce exosomes. Exosomes will be enriched by filtration and ultracentrifugation, and then normalized by Nanosight, Electron microscopy and key exosomes biomarkers. In order to ensure the safety of patients, we plan to inject exosomes through abdominal puncture under ultrasound guidance, and purchase medical insurance for patients. This first-in-human study is aimed to evaluate the safety of this exosome product for gene therapy and preliminary evidence of efficacy using plasma LDL-C levels as a surrogate biomarker. The study is promising to provide a new therapeutic approach for the treatment of Homozygous Familial Hypercholesterolemia patients.
mRNA therapy is a highly promising gene therapeutic strategy in the treatment of Homozygous Familial Hypercholesterolemia (HoFH). Exosomes is safe and efficient carriers for mRNA drug delivery, due to their biocompatibility, bioavailability. This first-in-human study is aimed to evaluate the safety and preliminary effectiveness of Exosome-based ldlr mRNA nanoplatform for gene therapy in HoFH.