Future directions in the treatment of malignant gliomas with temozolomide

Temozolomide (TMZ) is a new, orally administered, second-generation imidazotetrazine prodrug with essentially 100% oral bioavailability that has demonstrated meaningful efficacy and an acceptable safety profile in the treatment of patients with recurrent glioblastoma multiforme. Because of its unique properties and broad spectrum of anticancer activity, preliminary studies are being conducted to evaluate the efficacy of TMZ in combination with other chemotherapeutic agents, radiation, or immunotherapy. The presence of de novo or acquired resistance to alkylating agents exhibited by malignant gliomas represents a serious impediment in the treatment of these tumors. This review discusses the mechanism of action of TMZ and strategies for overcoming pathways of resistance to this promising agent, including the use of TMZ in combination with other chemotherapeutic agents or radiation therapy, and exploration of alternate dosing schedules. Studies that have evaluated some of these strategies indicate that TMZ is a useful therapeutic option in patients with high-grade gliomas. Alternative approaches, including the use of high-dose TMZ with bone marrow transplantation and in combination with gene therapy, will also be discussed.