High-performance liquid chromatographic analysis and stability of anti-tumor agent temozolomide in human plasma

Temozolomide (SCH 52365; TEMODAL) is an antineoplastic agent with activity against a broad spectrum of murine tumors. This compound is currently marketed in the European Union for the treatment of patients with glioblastoma multiforme and anaplastic astrocytoma, which are serious and aggressive types of brain cancers. It has been postulated that temozolomide exerts its in vivo activity via the decomposition product MTIC, which is believed to alkylate nucleophiles, and in the process is converted to AIC. A high-performance liquid chromatographic (HPLC) method was developed and validated for the analysis of temozolomide in human plasma. The determination of temozolomide involved extraction with ethyl acetate followed by separation on a reversed phase C-18 column and quantification by UV absorbance at 316 nm. The calibration curve was linear over a concentration range of 0.1-20 microg/ml. The limit of quantitation was 0.1 microg/ml, where the coefficient of variation (CV) was 0% and the bias was 10.0%. The method was precise with a coefficient of variation ranging from 2.5 to 6.9% and accurate with a bias ranging from 5.0 to 10.0%. Temozolomide was unstable at 37 degrees C in human plasma with a degradation t1/2 of 15 min; however, it was stable at 4 degrees C for at least 30 min. Temozolomide was stable in acidified human plasma (pH < 4) for at least 24 h at 25 degrees C, and for at least 30 days at -20 degrees C. Moreover, temozolomide was stable in acidified human plasma after being subjected to three freeze thaw cycles. The assay was shown to be specific, accurate, precise, and reliable for use in pharmacokinetic studies.