Scott Ralph

Neuroprotection in a rat Parkinson model by GDNF gene therapy using EIAV vector

Vectors based on lentiviruses are opening up new approaches for the treatment of neurodegenerative diseases. Currently, the equine infectious anaemia virus (EIAV) vector is one of the most attractive gene delivery systems with respect to neuronal tropism. The aim was to validate EIAV-lentiviral vectors as a gene delivery system for neurotrophic factor genes in an animal model of Parkinsons disease. EIAV carrying the glial cell line-derived neurotrophic factor (GDNF) gene was unilaterally injected into rat striatum and above the substantia nigra (SN). One week later, the rats received a 6-OHDA lesion into the ipsilateral striatum. GDNF delivery led to extensive expression of GDNF protein within the striatum. In addition, near complete protection against dopaminergic cell death was observed in the GDNF-treated group.

367. A Dopamine Gene Therapy for Advanced PD: 4 Years Phase I/II Clinical Update

Parkinsons disease (PD) is a neurodegenerative condition that results in a progressive degeneration of dopaminergic neurons. The dopamine (DA) precursor L-Dopa and dopamine agonists provide the primary standard of care and demonstrate good therapeutic benefit in the early stages of disease. However, their long term use is associated with severe motor side effects that are at least partially caused by the fluctuating nature of dopaminergic stimulation that arises from oral drug administration. As such, a therapy that provides a more continuous and local supply of dopamine to the site of pathology provides a potential approach for the development of new therapeutic strategies. ProSavin® is a gene therapy product that utilises a lentiviral vector to transfer three genes that are critical for de novo dopamine biosynthesis in the striatum, that is depleted of dopamine in PD. Fifteen advanced PD patients have received ProSavin® in three dose cohorts. ProSavin® has been demonstrated to be safe and well tolerated at all doses evaluated to date. No serious adverse events related to the study drug or surgical procedures were observed. All patients demonstrated improvement over baseline at both 6 and 12 months, which were sustained in some patients up to four years. Patients in the highest dose cohort demonstrated the greatest improvement in motor scores, a reduction in requirement for oral dopaminergic medication, and evidences of DA production by PET imaging. In summary, ProSavin® was safe and well tolerated in advanced PD patients. To increase the dose of ProSavin® by administering more vectors is not desirable due to physical constraints. Therefore we have generated OXB-102, an improved version of ProSavin®, that expresses the same enzymes but with an increased DA production per genetically modified cell. An update on OXB-102 will be presented.

200. Advancing a State of the Art Gene Therapy for Parkinson's Disease

The primary standard of care for Parkinsons disease (PD) is oral dopaminergic treatments and although these are initially highly efficacious, over time they lead to debilitating long term side effects that seriously impact on the quality of life and restrict the long-term effectiveness of such treatments.OXB-102 is a lentiviral-based vector that delivers the genes encoding the three key enzymes in the dopamine (DA) biosynthetic pathway, tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), and GTP-cyclohydrolase (CH1), to nondopaminergic striatal neurons of the sensorimotor putamen, thus providing these cells with the ability to synthesise and release their own DA. The effectiveness of this strategy has already been demonstrated in rodents, non-human primates and Parkinsons (PD) patients (Palfi et. al, Lancet 2014) with a precursor gene therapy vector called ProSavin®. OXB-102 is an improved version of ProSavin® that expresses the same enzymes but with an increased DA production per genetically modified cell.In non-clinical studies the efficacy of a full-strength and a 1/5th dose of OXB-102 has been compared to the efficacy of full-strength ProSavin® in the ‘gold standard’ MPTP NHP model of PD; a vector that does not express any genes was used as a negative control. The longitudinal follow-up consisted of recording clinical rating scores and video-based quantification of locomotor activity before and after vector administration. The full-strength and the 1/5th dose of OXB-102 were as efficacious as the full-strength dose of ProSavin®, whereas the control-treated macaques maintained a significant PD phenotype, indicating improved dopamine production from OXB-102.Positron emission tomography (PET) was also carried out at baseline and at 3 and 6 months following vector administration using 18F-FMT, a presynaptic biomarker that acts as a substrate of AADC. There was a significant increase in the FMT signal in both of the OXB-102 treatment groups that was greater than in the ProSavin® treated animals whilst there was no significant change in the FMT signal in the control treatment group.Results from a 6-month toxicology and biodistribution study in the NHP indicate that the OXB-102 vector is safe and well tolerated following stereotactic administration into the putamen and the vector does not significantly spread beyond the site of administrationGMP manufacture of OXB-102 for a planned clinical trial in PD patients is currently in progress.

528. VEGF gene therapy with retrogradely transported lentivirus prolongs survival in mouse ALS model

We have developed a minimal lentiviral vector system that mediates efficient gene transfer into mammalian cells. The lentiviral vector system is derived from the non-primate equine infectious anaemia virus (EIAV, LentiVector®). LentiVector® has been shown to mediate long term gene transfer in the central nervous system with efficient expression and minimal toxicity (Mazarakis et al., 2001; Azzouz et al., 2002). We have previously demonstrated that pseudotyping of LentiVector® with the glycoprotein of the ERA strain of the rabies virus confers retrograde axonal transport on these vectors (Mazarakis et al., 2001). Delivery of such vectors by direct injection into muscle of rodent resulted in transduction of cells local to the site of injection. Efficient transduction of motor neurons (MNs) projecting into the injection site was also observed. These results, therefore indicated, that gene therapy approaches involving targeting of LentiVector® to MNs via peripheral administration into muscle may offer a promising strategy for gene therapy in motor neuron diseases (MND).