Temozolomide (TMZ), sold under the brand name Temodar among others, is a medication used to treat brain tumors such as glioblastoma and anaplastic astrocytoma. It is taken by mouth or via intravenous infusion.The most common side effects with temozolomide are nausea, vomiting, constipation, loss of appetite, alopecia (hair loss), headache, fatigue, convulsions (seizures), rash, neutropenia or lymphopenia (low white-blood-cell counts), and thrombocytopenia (low blood platelet counts). People receiving the solution for infusion may also have injection-site reactions, such as pain, irritation, itching, warmth, swelling and redness, as well as bruising.Temozolomide is an alkylating agent used to treat serious brain cancers; most commonly as second-line treatments for astrocytoma and as the first-line treatment for glioblastoma. Olaparib in combination with temozolomide demonstrated substantial clinical activity in relapsed small cell lung cancer. Medical uses
In the United States temozolomide is indicated for the treatment of adults with newly diagnosed glioblastoma multiforme concomitantly with radiotherapy and subsequently as monotherapy treatment; or adults with refractory anaplastic astrocytoma who have experienced disease progression on a drug regimen containing nitrosourea and procarbazine.In the European Union temozolomide is indicated for adults with newly diagnosed glioblastoma multiforme concomitantly with radiotherapy and subsequently as monotherapy treatment; or children from the age of three years, adolescents and adults with malignant glioma, such as glioblastoma multiforme or anaplastic astrocytoma, showing recurrence or progression after standard therapy. Contraindications
Temozolomide is contraindicated in people with hypersensitivity to it or to the similar drug dacarbazine. The use of temozolomide is not recommended in people with severe myelosuppression.
In the laboratory, this combination indeed showed increased temozolomide activity in tumor-cell culture in vitro and in animal models in vivo. However, a recently completed phase-II clinical trial with brain-tumor patients yielded mixed outcomes; while there was some improved therapeutic activity when O6-BG and temozolomide were given to patients with temozolomide-resistant anaplastic glioma, there seemed to be no significant restoration of temozolomide sensitivity in patients with temozolomide-resistant glioblastoma multiforme.Some efforts focus on engineering hematopoietic stem cells expressing the MGMT gene prior to transplanting them into brain-tumor patients. This would allow for the patients to receive stronger doses of temozolomide, since the patients hematopoietic cells would be resistant to the drug.High doses of temozolomide in high-grade gliomas have low toxicity, but the results are comparable to the standard doses.Two mechanisms of resistance to temozolomide effects have now been described: 1) intrinsic resistance conferred by MGMT deficiency (MGMTd) and 2) intrinsic or acquired resistance through MMR deficiency (MMRd). The MGMT enzyme is the first line of repair of mismatched bases created by TMZ. Cells are normally MGMT proficient (MGMTp) as they have an unmethylated MGMT promoter allowing the gene to be expressed normally. In this state, TMZ induced DNA damage is able to be efficiently repaired in tumor cells (and normal cells) by the active MGMT enzyme. Cells may grow and pass through the cell cycle normally without arrest or death. However, some tumors cells are MGMT deficient (MGMTd). This is most commonly due to abnormal methylation of the MGMT gene promoter and suppression of gene expression.