Optimized pharmacological control over the AAV-Gene-Switch vector for regulable gene therapy

Abstract

Gene therapy in its current design is an irreversible process. It cannot be stopped in case of unwanted side effects, nor can expression levels of therapeutics be adjusted to individual patient’s needs. Thus, the Gene-Switch (GS) system for pharmacologically regulable neurotrophic factor expression was established for treatment of parkinsonian patients. Mifepristone, the synthetic steroid used to control transgene expression of the GS vector, is an approved clinical drug. However, pharmacokinetics and -dynamics of mifepristone vary considerably between different experimental animal species and depend on age and gender. In humans, but not in any other species, mifepristone binds to a high-affinity plasma carrier protein. We now demonstrate that the formulation of mifepristone can have robust impact on its ability to activate the GS system. Furthermore, we show that a pharmacological booster, ritonavir (Rtv), robustly enhances the pharmacological effect of mifepristone, and allows it to overcome gender- and species-specific pharmacokinetic and -dynamic issues. Most importantly, we demonstrate that the GS vector can be efficiently controlled by mifepristone in the presence of its human plasma carrier protein, α1-acid glycoprotein, in a “humanized” rat model. Thus, we have substantially improved the applicability of the GS vector toward therapeutic use in patients.

Oxidative stress induced by sustained supraphysiological intrastriatal GDNF delivery is prevented by dose regulation

“…Some systems have, however, been developed that use drugs at clinically acceptable doses. 28 , 71 , 78 In particular, the dox-inducible vector expressing hGDNF used in this study, allowed to obtain DA neuron protection and halt the progression of motor symptoms at a dox dose of 200 mg/kg dox diet, corresponding to a dox plasmatic concentration of 319 ± 50 ng/mL, 28 which is below the antimicrobial threshold (1 mg/mL) and in the range of doses used to treat benign inflammatory diseases such as rosacea or periodontitis, with no effect on intestinal 79 or subgingival 80 , 81 flora.…”

An Adapted GeneSwitch Toolkit for Comparable Cellular and Animal Models: A Proof of Concept in Modeling Charcot-Marie-Tooth Neuropathy

“…As a matter of fact, the GeneSwitch™ technology was previously tested to prevent a lethal knockout phenotype in inhibin α null mice [56]. Its application was also reported in a humanized rat model to test controlled GDNF expression as a treatment strategy for Parkinson's disease [57]. To our knowledge, the GeneSwitch™ was not tested in model organisms such as zebrafish and worms.…”

Gene Therapeutic Strategies for Peripheral Artery Disease and New Opportunities Provided by Adeno-Associated Virus Vectors

“…The Gene-Switch system is controlled by mifepristone, which dimerizes with the gene-switch protein, allowing expression from the transgene promoter. 102 However, these systems are relatively new, and their feasibility in the clinic remains to be tested. For example, the initially promising Tet-operon system was found to be immunogenic in nonhuman primates.…”