Scientific Abstract 
PROJECT TITLE: Gene Therapy for the Treatment of Malignant Brain Tumors 
with In Vivo Tumor Transduction with the Herpes Thymidine 
Kinase Gene/Ganciclovir System. 
PRINCIPAL INVESTIGATORS: Corey Raffel, M.D., Ph.D. and Kenneth W. 
Culver, M.D. 
SCIENTIFIC ABSTRACT 
Murine retroviral vectors can infect a wide variety of 
proliferating mammalian cell types (e.g. lymphocytes) . Non- 
proliferating tissues (e.g. neurons) are not transduced by murine 
retroviral vectors. These findings suggest that this type of vector may 
be useful for the selective introduction of genes into growing tumors 
in the brain, since the tumor is essentially the only tissue that will 
integrate and express the vector genes. 
The possibility of direct in vivo gene transfer into growing brain 
tumors in animals has been investigated. Rats with a malignant brain 
tumor were given an intratumoral stereotaxic injection of murine 
retroviral vector-producer cells (VPC) that were producing vectors 
containing the Herpes simplex-thymidine kinase (HS-tk) gene or a control 
VPC line containing the B-galactosidase gene. The animals were rested 
5 days to allow time for the HS-tk retroviral vectors that were produced 
in situ to transduce the neighboring proliferating gliosarcoma. The 
animals were then treated with the anti-herpes drug ganciclovir (GCV) . 
Tumors injected with the HS-tk VPC regressed completely with GCV therapy 
while the tumors injected with B-galactosidase VPC developed large 
tumors. Staining for B-galactosidase (+) cells in control animal brain 
revealed transduction of 10-50% of the tumor cells without evidence of 
transduction of the surrounding normal brain tissue. No significant 
toxicity was observed in toxicity studies in mice, rats and non-human 
primates . 
Based upon these findings, we propose a human clinical trial to 
determine if the direct implantation of the GITkSvNa VPC line into 
growing human brain tumors will induce regression with GCV therapy. The 
patient population primarily consists of children with recurrent 
malignant tumors, who are currently considered ineligible for the 
approved adult protocols. The RAC has previously approved two trials 
involving this type of therapy. In this protocol, children will undergo 
treatment based on the surgical accessibility of their tumor. Those 
with resectable tumors will undergo surgical debulking of the tumor 
followed by repeated treatments of HS-tk VPC into the tumor bed in an 
attempt to induce complete regression of the tumor with GCV therapy. 
Children with unresectable tumors will undergo stereotaxic injection of 
the tumor with VPC. These children will have failed standard therapy 
for their tumor and are expected to survive for several weeks to a few 
months . 
[50] 
Recombinant DNA Research, Volume 18 
