Microdialysis measurement of intratumoral temozolomide concentration after cediranib, a pan-VEGF receptor tyrosine kinase inhibitor, in a U87 glioma model

Background: Combining anti-angiogenesis agents with cytotoxic agents for the treatment of malignant gliomas may affect the cytotoxic drug distribution by normalizing the blood-brain barrier (BBB). This study examines the intratumoral concentration of temozolomide (TMZ) in the presence and absence of the pan-VEGF receptor tyrosine kinase inhibitor, cediranib. Methods: Seven nude rats bearing U87 intracerebral gliomas had a microdialysis probe centered within the tumor. Ten-days after tumor implantation, TMZ (50 mg/kg) was given orally. The extracellular fluid (ECF) concentrations of TMZ within the tumor were assessed via microdialysis for 6 h following TMZ administration. Cediranib (6 mg/kg) was then given orally, and 12 h later, TMZ was re-administered with subsequent microdialysis collection. A subset of animals also underwent functional MRI to assess angiogenesis in vivo at post-inoculation days 12 and 21, before and after the cediranib treatment. Results: After dosing of oral TMZ only, ECF-TMZ mean-C _max and area under the concentration curve(AUC_0-∞) within the tumor were 0.59 μg/mL and 1.82 μg h/mL, respectively. Post-cediranib, ECF-TMZ mean-C _max and AUC_0-∞ were 0.83 μg/mL and 3.72 ± 0.61 μg h/mL within the tumor, respectively. This represented a 1.4-fold (p = 0.3) and 2.0-fold (p = 0.06) increase in the ECF-TMZ C _max and AUC_0-∞, respectively, after cediranib administration. In vivo MRI measurements of the various vascular parameters were consistent with a BBB "normalization" profile following cediranib treatment. Conclusions: In the U87 intracerebral glioma model, within the first day of administration of cediranib, the intratumoral concentrations of TMZ in tumor ECF were slightly, but not statistically significantly, increased when compared to the treatment of TMZ alone with radiographic evidence of a normalized BBB.