Safety and biodistribution studies of an HSV multigene vector following intracranial delivery to non-human primates

Abstract

Malignant glioma is a fatal human cancer in which surgery, chemo-and radiation therapies are ineffective. Therapeutic gene transfer used in combination with current treatment methods may augment their effectiveness with improved clinical outcome. We have shown that NUREL-C2, a replication-defective multigene HSV-based vector, is effective in treating animal models of glioma. Here, we report safety and biodistribution studies of NUREL-C2 using rhesus macaques as a model host. Increasing total doses (1 Â 10 7 to 1 Â 10 9 plaque forming units (PFU)) of NUREL-C2 were delivered into the cortex with concomitant delivery of ganciclovir (GCV). The animals were evaluated for changes in behavior, alterations in blood cell counts and chemistry. The results showed that animal behavior was generally unchanged, although the chronic intermediate dose animal became slightly ataxic on day 12 postinjection, a condition resolved by treatment with aspirin. The blood chemistries were unremarkable for all doses. At 4 days following vector injections, magnetic resonance imaging showed inflammatory changes at sites of vector injections concomitant with HSV-TK and TNFa expression. The inflammatory response was reduced at 14 days, resolving by 1 month postinjection, a time point when transgene expression also became undetectable. Immunohistochemical staining following animal killing showed the presence of a diffuse low-grade gliosis with infiltrating macrophages localized to the injection site, which also resolved by 1 month postinoculation. Viral antigens were not detected and injected animals did not develop HSV-neutralizing antibodies. Biodistribution studies revealed that vector genomes remained at the site of injection and were not detected in other tissues including contralateral brain. We concluded that intracranial delivery of 1 Â 10 9 PFU NUREL-C2, the highest anticipated patient dose, was well tolerated and should be suitable for safety testing in humans.

Evaluation and optimization of the administration of a selectively replicating herpes simplex viral vector to the brain by convection-enhanced delivery

“…16 In this study, the feasibility of administering a replicationselective HSV-1 vector by CED into normal brain was therefore examined in detail. In spite of the large number of preclinical studies that have involved the direct intracranial administration of HSV-based vectors, 17,18,[20][21][22][23][24][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] remarkably this represents the first published study to evaluate the distribution properties of an HSV-1 vector using appropriate infusion parameters in both gray and white matter, as well as evaluation of strategies to improve vector distribution.…”

“…16 Clearly this has the potential to make the effective intracranial administration of HSV-1-based vectors unachievable. Nevertheless, in addition to the aforementioned clinical trials, [6][7][8][9] HSV vectors have been administered by stereotactic injection into normal mouse, [17][18][19] rat [20][21][22][23][24][25][26] and primate brains, [20][21][22][23][24][25][26][27][28] animal models of high-grade glioma, [29][30][31][32][33][34][35] mucopolysaccharidosis type VII, 36 GM2 gangliosidosis 37 and Parkinson's disease, [37][38][39] as well as being administered by CED into a glioma rat model. 40 In view of there being this large number of studies, it is surprising that to date no attempt has been made to systematically evaluate and optimize the delivery of these vectors directly into the brain.…”

Enhancement of Th2 responses to replicative herpes simplex virus type 1 vectors by immunomodulative chemotherapy

“…Replication-competent Dg34.5 HSV-1 vectors are safe in humans up to 10 5 PFU [21]. The nonreplicating NUREL-C2 HSV-vector has been shown to be safe in rhesus macaques up to 10 9 PFU when infected intracranially [22].…”

Gene transfer to the rhesus monkey brain using SV40-derived vectors is durable and safe

“…3,4,8,[42][43][44] HSV type 1 multigene vector safety and biodistribution have also been studied in non-human primate brain. 45 In non-human primates, CNS transduction efficiency and durability varied with the vector, injection site and method of delivery. For AAV vectors, transduced cells numbered from 444 400 at 8 weeks to 1 296 350 at 3 years, 32 for lentiviral vectors, 764 149 at 1 month for lentiviral vectors 42 titers ranging between 2.75Â10 12 genome copies per ml for AAV2/1, 1.69Â10 13 42 and between 2Â10 10 PFU ml À1 (ref.…”