A neuropharmacokinetic assessment of bafetinib, a second generation dual BCR-Abl/Lyn tyrosine kinase inhibitor, in patients with recurrent high-grade gliomas

PURPOSE

The primary objective of this study was to use intracerebral microdialysis (ICMD) to determine the neuropharmacokinetics of bafetinib, a dual BCR-Abl/Lyn tyrosine kinase inhibitor that may have activity against gliomas.

METHODS

A microdialysis catheter was placed into either peritumoural or enhancing brain tissue of seven patients at the time of tumour resection or biopsy. Twenty-four hours later, bafetinib was administered, 240 or 360 mg po, repeating the same dose 12 h later. Dialysate samples were continuously collected for 24h, with plasma samples obtained in parallel. One to two weeks after finishing ICMD, patients were allowed to resume taking bafetinib continuously while being observed for toxicity and tumour response.

RESULTS

Twenty-six dialysate samples per patient were collected (n=6) and analysed for bafetinib by tandem mass spectrometry. Bafetinib concentrations in the brain were below the lower limit of detection of the assay (0.1 ng/ml) in all samples except one from a single subject that was 0.52 ng/ml. The mean plasma bafetinib maximum concentrations after dose 1 and 2 were 143±99 and 247±73 ng/ml, respectively. Only one patient remained on treatment past two cycles, and no radiographic responses were seen.

CONCLUSIONS

Bafetinib does not sufficiently cross intact or disrupted blood-brain barrier, and therefore, systemic administration of bafetinib is not recommended when investigating this drug as a treatment for brain tumours. ICMD can be a valuable research tool in early drug development. Lead-in ICMD studies can be performed relatively quickly, requiring only a small number of patients, and without significantly disrupting standard cancer care.

Gliomas and seizures

Glial neoplasms account for nearly 50% of all adult primary brain tumors. They originate from glial cells in the brain and/or spinal cord and include low-grade diffuse astrocytomas, anaplastic-astrocytomas, and glioblastomas. Of all brain tumors, glioblastoma multiforme (GBM) is the most aggressive and is characterized by rapid glial cell growth, resistance to radio- and chemo- therapies, and relentless infiltration and spreading throughout the central nervous system (CNS). In glioblastomas, primary tumor growth and CNS invasion are associated with the activation of complex structural molecular and metabolic changes within the tumor tissue, which profoundly affect the surrounding neuronal networks and may in part explain induction of epilepsy. In fact, epileptic seizures are very common among patients with glial tumors, reaching nearly 50% in glioblastoma patients and almost 90% in low-grade astrocytomas. The overall hypothesis presented here discusses the possibility that the aberrant tumor cell metabolism may act directly on neuronal network, and this leads to seizure susceptibility. Further invasion and growth of the malignant glial cells exacerbate this initial pathologic state which promotes recurrent seizures (epileptogenesis).