Phase I trial of adenovirus-mediated p53 gene therapy for recurrent glioma: Biological and clinical results

Purpose: Advances in brain tumor biology indicate that transfer of p53 is an alternative therapy for human gliomas. Consequently, we undertook a phase I clinical trial of p53 gene therapy using an adenovirus vector (Ad-p53, INGN 201). Materials and Methods: To obtain molecular information regarding the transfer and distribution of exogenous p53 into gliomas after intratumoral injection and to determine the toxicity of intracerebrally injected Ad-p53, patients underwent a two-stage approach. In stage 1, Ad-p53 was stereotactically injected intratumorally via an implanted catheter. In stage 2, the tumor-catheter was resected en bloc, and the postresection cavity was treated with Ad-p53. This protocol provided intact Ad-p53-treated biologic specimens that could be analyzed for molecular end points, and because the resection cavity itself was injected with Ad-p53, patients could be observed for clinical toxicity. Results: Of fifteen patients enrolled, twelve underwent both treatment stages. In all patients, exogenous p53 protein was detected within the nuclei of astrocytic tumor cells. Exogenous p53 transactivated p21^CIP/WAF and induced apoptosis. However, transfected cells resided on average within 5 mm of the injection site. Clinical toxicity was minimal and a maximum-tolerated dose was not reached. Although anti-adenovirus type 5 (Ad5) titers increased in most patients, there was no evidence of systemic viral dissemination. Conclusion: Intratumoral injection of Ad-p53 allowed for exogenous transfer of the p53 gene and expression of functional p53 protein. However, at the dose and schedule evaluated, transduced cells were only found within a short distance of the injection site. Although toxicity was minimal, widespread distribution of this agent remains a significant goal.