Temozolomide: a cytostatic drug that is still important today

TMZ has an advantage over other traditional alkylating agents (carmustine, lomustine, procarbazine), which are highly toxic and have poor patient survival. TMZ circumvents these problems because cytochrome P450 enzymes and the kidneys are not involved in its metabolism, it has predictable side effects (nausea, vomiting, thrombocytopenia, neutropenia), which are usually reversible and only mild to moderate, have been widely described. About half of patients treated with TMZ have high drug resistance induced by activity of O6-methylguanine methyltransferase. Cancer stem cells (CSCs), which are found among the neoplastic cell population, have also been shown to be responsible for resistance to TMZ. Additionally, acquired immunity, induced by TMZ’s epigenetic and genetic alterations, may develop. Currently, there are new therapeutic strategies for GBM based on nanotechnology, which are aimed at improving TMZ treatment (e.g. the use of apolipoprotein), or other techniques (siRNA, which increases the oxygen level in the tumour). Thus, although TMZ was discovered more than three decades ago, this drug will be used to treat not only GBM, but also a large number of neoplastic pathologies. Further research focused on understanding the mechanisms of action and resistance to TMZ is required to improve its clinical application today and in the future. Keywords: alkylating agents, drug resistance, chemotherapy, nanoparticles, cancer, glioblastoma multiforme