Phase II Study of Combined Temozolomide and SGT-53 for Treatment of Recurrent Glioblastoma

The p53 is a vital human tumor suppressor gene. Loss of p53 suppressor function is present in the majority of human cancers. The p53 protein has a diverse range of functions including regulation of cell cycle checkpoints, cell death (apoptosis), senescence, DNA repair, maintenance of genomic integrity, and control of angiogenesis. Abnormalities of the p53 gene may impact the efficacy of standard anticancer treatments such as radiation and chemotherapy. P53 mutation and pathway dysfunction are associated with poor clinical outcomes and the presence of the p53 mutation correlates with resistance to chemotherapy and radiation. The development of somatic gene therapy has created the potential to restore wild type function of p53. SGT-53 is a complex of cationic liposome encapsulating a normal human wild type p53 DNA sequence in a plasmid backbone. This complex has been shown to efficiently and specifically deliver the p53 cDNA to the tumor cells and to cross the blood-brain barrier. Introduction of the p53 cDNA sequence is expected to restore wtp53 function in the apoptotic pathway. P53 restoration has been shown most effective in enhancing cytotoxicity in combination with an agent which results in DNA damage or initiates apoptosis. The primary mechanism of resistance to current standard chemotherapeutic agent Temozolomide (TMZ) is overexpression of O6-methylguanine-DNA-methyl transferase (MGMT), which repairs the TMZ-induced DNA lesion by removing the o6-guanine adducts. Thus, a means to down modulate MGMT activity would enhance the therapeutic effect of TMZ. A number of reports have indicated that increasing wtp53 expression can down-regulate expression of DNA repair genes such as MGMT and increases the sensitivity of tumor cells to alkylating agents. This is a Phase II clinical trial of the tumor-targeted SGT-53 nanocomplex in combination with chemotherapeutic agent, temozolomide which is the standard of care for Glioblastoma Multiforme (GBM) brain tumors. We propose to test the combination of SGT-53 and standard temozolomide to determine efficacy and safety in patients with confirmed glioblastoma who have proven tumor recurrence or progression.