Survival data following phase 1/2 studies using precision tumor-targeted gene delivery to advanced chemotherapy-resistant malignancies.

Abstract

101 Background: Targeted gene delivery in vivo has long been considered the “Holy Grail” of gene therapy. Methods: We reviewed long-term data of patients with advanced chemotherapy-resistant malignancies, previously-treated patients with two tumor-targeted retrovectors: (1) encoding cytotoxic dominant negative cyclin G1, DeltaRex-G (formerly Rexin-G), and (2) encoding cytokine GMCSF plus suicide gene HStk, DeltaVax (formerly Reximmune-C). Results: Ninety-nine patients received > 5,000 intravenous infusions of DeltaRex-G; another 16 patients received 288 intravenous infusions of DeltaRex-G + 96 infusions of DeltaVax followed by valacyclovir p.o. No therapy-related bone marrow suppression, organ dysfunction or delayed treatment related adverse events were observed. Survival analysis showed 5.0% 10-year overall survival rate for patients who received DeltaRex-G alone, and 18.8% for DeltaRex-G + DeltaVax. Conclusions: Data analysis indicates that tumor-targeted gene delivery in vivo, represented by cytocidal DeltaRex-G, with or without immuno-stimulatory DeltaVax, has induced prolonged ( > 10 years) sustained remissions in cancer patients presenting with advanced chemotherapy-resistant solid and hematologic malignancies—plausibly due to safety, selectivity, and immune modulation. While the curative potential of precision targeted genetic medicine necessarily remains an academic question; it is clear that these initial long-term, cancer-free ( > 10 year) survivors represent a major milestone in both cancer therapy and immunotherapy. Phase 2-3 clinical trials are planned for these hard-to treat malignancies.