LAUSR

Abstract Paediatric brain tumours are the second most common cancer after haematological malignancies. Intermittent dosing regimens are typical for chemotherapy drugs in order to avoid excessive damage to organs and avoid the onset of late effects. Cannabidiol (CBD) has been shown to have cytotoxic properties on paediatric brain tumour cell lines. Although CBD is far less toxic and damaging than the classical chemotherapy options which are currently available to children suffering with brain tumours, there are some possible side effects. Given that the half-life of the drug is 24 hours, it was important to establish the nature of the effect of cumulative dosing on top of the remaining drug in the system. The pHGG cell line, SF188 was cultured in different concentrations of CBD with either 1, 2 or 3 doses being given on consecutive days. 24 hours after the last dose the cells were analysed using the resazurin assay. It was observed that the amount of drug required for an EC50 to be obtained decreased; 17.6µM (1 dose), 8µM (2 doses), 5µM (3 doses) and that cell survival was reduced to nearly 0% in those cells which received multiple does of CBD at 17.6µM. In order to mimic the intermittent dosing regime, the cells were returned to the incubator for 4 days before the resazurin assay was repeated. The decrease in viability was maintained over the extended culture period meaning that the ability of even the apparent “healthy” cells to proliferate had been permanently affected.