1. ¹Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
2. ²Department of Neurosurgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
3. ³Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
4. ⁴Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

Correspondence: Dr JC Glorioso, Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, E1240 Biomedical Science Tower, Pittsburgh, PA 15261, USA

Received 28 April 2004; Accepted 11 June 2004; Published online 12 August 2004.

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 (1 10⁷ to 1 10⁹ 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 TNF 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 1 10⁹ PFU NUREL-C2, the highest anticipated patient dose, was well tolerated and should be suitable for safety testing in humans.