O(6)-alkylguanine-DNA alkyltransferase (AGAT), involved in temozolomide-induced DNA damage repair, plays a key role in the efficacy of temozolomide. AGAT activity may be reduced by protracted temozolomide doses. On the basis of the preclinical findings, we treated patients with a histologically-proven diagnosis of glioblastoma (GBM) following adjuvant temozolomide failure with a low protracted dose of temozolomide (130 mg/m(2)/day, days 1-7 and 15-21, every 4 weeks). The primary endpoint of the study was 6-month progression-free survival (PFS-6 m). The secondary endpoints were overall survival (OS) from the start of temozolomide alternative schedule and toxicity. Enrolment was ceased at 27 patients due to the lack of effectiveness of this regimen. Results indicate that our schedule is well-tolerated, but ineffective in patients with GBM and further strategies are required to improve the outcome of these patients.