Preclinical and preliminary clinical evaluation of genetically transduced dermal tissue implants for the sustained secretion of erythropoietin and interferon α

Abstract

Protein drugs are currently delivered by bolus injection and although treatment frequently is successful, these methods also have major drawbacks, which call for the development of alternative technologies allowing prolonged delivery of these drugs. We developed a new ex vivo gene therapy platform called Transduced Autologous Restorative Gene Therapy (TARGT) for sustained long term production and secretion of autologous therapeutic proteins. A biopsy of dermal tissue taken from the patient is transduced ex vivo with a viral vector encoding the required gene under a constitutive promoter. Following measurement of protein secretion ex vivo, the transduced dermal tissue is implanted back into the patient, where it secretes the therapeutic protein into the circulation for several months or longer. A major hurdle to this approach is potential immunogenicity of the transduced tissue following implantation. In this paper we describe the preclinical and early clinical development of this technology, which allowed overcoming these hurdles. To that end, we have used the helper dependent (HD) adenoviral vector with newly designed expression cassette containing genetic elements to optimize transgene expression. Moreover, we have developed procedures for TARGT tissue implantation, with measures to improve engraftment and reduce inflammation and rejection. Implantation of human TARGT to immune-deficient SCID mice indicated long-term production of active proteins in the blood. Preliminary results of a clinical trial from two anemic end-stage renal disease patients, implanted with TARGTs expressing the human erythropoietin (EPO) gene, demonstrated prolonged secretion with physiologic blood level of the hormone and Hemoglobin maintenance in the desired range, for a period of at least five months without exogenous EPO administration. We believe that the TARGT technology has the potential to become a platform for the sustained delivery of therapeutic proteins in various clinical indications.

Sustained secretion of anti‐tumor necrosis factor α monoclonal antibody from ex vivo genetically engineered dermal tissue demonstrates therapeutic activity in mouse model of rheumatoid arthritis

“…This notion, however, should be tested in controlled clinical studies. Indeed, clinical studies using TARGT tissues secreting erythropoietin in patients with anemia demonstrated safety and efficacy, as indicated by an elevated hematocrit and erythrocyte differentiation similar to multiple bolus injections with recombinant erythropoietin …”

“…DNA encoding the adalimumab light and heavy chains was inserted into the same open reading frame in the previously described HDAd‐MAR‐EF1α cassette in HD adenovirus DNA (Figure ). The IgG DNA coding sequences were codon optimized and all CpG sequences in the expression cassette were changed, without affecting the gene reading frame.…”

“…Autologous microdermal tissues were harvested from abdominal skin slabs donated by healthy volunteers, who were undergoing an elective cosmetic abdominoplasty plastic surgical procedure, as described previously . All skin donations were approved by the ethic committee in the respective clinical centers where the procedure was performed, as well as by the Israeli Ministry of Health.…”

“…We have demonstrated the utility of this approach using the erythropoietin gene transduced into microdermal tissue ex vivo and implanted in kidney failure anemic patients. Indeed, in a phase I–II safety study, red blood cells levels in these patients were elevated to the normal range, in the absence of erythropoietin protein therapy bolus injections …”