Toxicity evaluation of prolonged convection-enhanced delivery of small-molecule kinase inhibitors in naïve rat brainstem.

PURPOSE: Convection-enhanced delivery (CED), a local drug delivery technique, is typically performed as a single session and drug concentrations therefore decline quickly post CED. Prolonged CED (pCED) overcomes this problem by performing a long-term infusion to maintain effective drug concentrations for an extended period. The purpose of the current study was to assess the toxicity of using pCED to deliver single and multi-drug therapy in naïve rat brainstem.

METHODS: Sixteen rats underwent pCED of three small-molecule kinase inhibitors in the pons. Single and multi-drug combinations were delivered continuously for 7 days using ALZET mini-osmotic pumps (model 2001, rate of 1 μl/h). Rats were monitored daily for neurological signs of toxicity. Rats were sacrificed 10 days post completion of infusion, and appropriate tissue sections were analyzed for histological signs of toxicity.

RESULTS: Two rats exhibited signs of neurological deficits, which corresponded with diffuse inflammation, necrosis, and parenchymal damage on histological analysis. The remaining rats showed no neurological or histological signs of toxicity.

CONCLUSION: The neurological deficits in the two rats were likely due to injury from physical force, such as cannula movement post insertion and subsequent encephalitis. The remaining rats showed no toxicity and therefore brainstem targeting using pCED to infuse single and multi-drug therapy was well tolerated in these rats.