Mitochondrial Expression of Therapeutic Proteins

DESCRIPTION (provided by applicant): A major problem in gene therapy and transfection technologies in general, is the occurrence of random integration/recombination of DNA into the nuclear genome which may disrupt key biological processes. The diagnosis of leukemia in two children involved in a gene therapy trial for X-linked severe combined immunodeficiency (SCID) highlights this risk. The nuclear genome contains the vast majority of human genes but is not the only repository of genetic information. The mitochondrial genome (mtDNA) encodes 13 genes involved in electron transport and is located in the mitochondrial matrix, separated from the nucleus by both mitochondrial inner and outer membranes. A single cell can contain thousands of mitochondria, each with multiple copies of the replication, transcription, and translation-competent 16,569 base pair mtDNA. If it were possible to utilize the mitochondrial machinery to produce therapeutic proteins, scientists and physicians would possess a method to circumvent manipulation of the nuclear genome and reduce the inherent associated risk. In a Phase I SBIR, Gencia Corporation successfully utilized a method for mitochondrial expression of genes cloned into full length mtDNA. These gene products could be specifically targeted to extra-mitochondrial locations, such as the nucleus. Using this novel mitochondrial transfection technology, Protofection(tm) (Protein Mediated Transfection), additional data beyond the aims of the Phase I study showed that protofection could deliver and express a full-length mtDNA engineered to express a nuclear targeted reporter protein (GFP, Green Fluorescent Protein), in vivo. Furthermore, the mechanism by which the mitochondrial transfection technology delivers mtDNA to mitochondria implicates mitochondrial lipid rafts. To address the therapeutic potential of this technology in this Phase II SBIR proposal, Gencia Corporation will target Friedreich's ataxia (FRDA), an autosomal recessive disease caused by a triplet expansion in frataxin, a gene which codes for a protein localized to mitochondria. By expressing frataxin in the mitochondria of an animal model of FRDA, Gencia Corporation believes the problems inherent in therapies targeting the nucleus can be overcome. The Specific Aims sought in this proposal would enable the first non-nuclear gene therapy for an autosomal disease and provide necessary data for an Investigational New Drug (IND) application to the FDA/Center for Biologics Evaluation and Research.