Minicircle - Die nächste Generation nicht-viraler Gentherapie-Vektoren. Zirkuläre, superspiralisierte Expressionskassetten ersetzen Plasmid-DNA

Minicircle-Based Engineering of Chimeric Antigen Receptor (CAR) T Cells

Plasmid DNA is being used as a pharmaceutical agent in vaccination, as well as a basic substance and starting material in gene and cell therapy, and viral vector production. Since the uncontrolled expression of backbone sequences present in such plasmids and the dissemination of antibiotic resistance genes may have profound detrimental effects, an important goal in vector development was to produce supercoiled DNA lacking bacterial backbone sequences: Minicircle (MC) DNA. The Sleeping Beauty (SB) transposon system is a non-viral gene delivery platform enabling a close-to-random profile of genomic integration. In combination, the MC platform greatly enhances SB transposition and transgene integration resulting in higher numbers of stably modified target cells. We have recently developed a strategy for MC-based SB transposition of chimeric antigen receptor (CAR) transgenes that enable improved transposition rates compared to conventional plasmids and rapid manufacturing of therapeutic CAR T cell doses (Monjezi et al. 2016). This advance enables manufacturing CAR T cells in a virus-free process that relies on SB-mediated transposition from MC DNA to accomplish gene-transfer. Advantages of this approach include a strong safety profile due to the nature of the MC itself and the genomic insertion pattern of MC-derived CAR transposons. In addition, stable transposition and high-level CAR transgene expression, as well as easy and reproducible handling, make MCs a preferred vector source for gene-transfer in advanced cellular and gene therapy. In this chapter, we will review our experience in MC-based CAR T cell engineering and discuss our recent advances in MC manufacturing to accelerate both pre-clinical and clinical implementation.

Minicircle: Next Generation DNA Vectors for Vaccination

The use of DNA vaccines requires pharmaceutical grade DNA that causes the immunization on the basis of a nucleic acid sequence that encodes the protein to be vaccinated against. This nucleic acid sequence can be a circular or linear plasmid, preferably a double stranded one and should not contain any other and especially not any "toxic" sequences. Sequences that are not desirable to be part of the DNA drug can be those deriving from the (typically) bacterial amplification system to produce the DNA vaccine. These could be those portions of a plasmid that are only used for controlling the bacterial replication of the plasmid or those used to select for the plasmid during cloning or even worse during production. After initial approaches to avoid the presence of these sequences in DNA vaccine plasmids with "mini-plasmids," a significant improvement in product safety was obtained by use of minicircles-circular and ccc-supercoiled expression cassettes of the DNA vaccine. Initial results proofed their extremely high expression level and recent comparison of DNA vaccines based on either plasmid or minicircle DNA show successful vaccination against HBV in mice, as shown in this overview chapter.