Effect of VAL-083, a novel N7 alkylating agent, on growth of temolozomide-resistant primary adult glioblastoma multiforme (GBM) cells providing a new potential treatment option for GBM.

Abstract

e13123 Background: Glioblastoma (GBM) remains one of the most difficult tumors to treat first because many new agents fail to cross the blood brain barrier (BBB), and second due to intrinsic drug resistance. Temozolomide (TMZ) is a front-line therapy for the treatment of GBM; however, it is often ineffective due to drug inactivation by O6-methylguanine-DNA methyltransferase (MGMT). Cancer stem cells (CSC) are a subpopulation of the tumor that resist therapy and give rise to relapse. Here we describe VAL-083, a novel alkylating agent that creates N7 methylation on DNA, and readily crosses the BBB. VAL-083 is currently undergoing human clinical trials in the USA in refractory GBM patients. We previously described how VAL-083 can overcome resistance associated with MGMT in cell lines, and targets brain tumor CSCs. This demonstrates that VAL-083 has the potential to surpass the standard-of-care. Methods: To provide further preclinical support for VAL-083 we examined the effect of VAL-083 on primary adult GBM cells in culture, isolated fresh following surgical resection, in cases where clinical activity of TMZ was known to be limited and high expression of MGMT had been observed. Results: VAL-083 (5uM) inhibited cell growth in these primary adult GBMs that did not show significant sensitivity to TMZ in vitro. VAL-083 also inhibited the growth of CSCs by 100% in neurosphere growth assays. Conclusions: In summary, VAL-083 demonstrates in vitro efficacy against primary adult GBM cells where TMZ has limited activity thereby further supporting the potential of VAL-083 to surpas the standard-of-care.