Plasma and cerebrospinal fluid pharmacokinetics of vincristine and vincristine sulfate liposomes injection (VSLI, marqibo®) after intravenous administration in Non-human primates

Summary

Purpose Vincristine sulfate liposomes injection (VSLI, Marqibo®) is an FDA approved encapsulated preparation of standard vincristine in sphingomyelin/cholesterol liposomes. Clinical pharmacokinetics show VSLI to be a long-circulating, slow release formulation that is confined to plasma, and prior data on cerebrospinal fluid (CSF) pharmacokinetics are lacking. We report our results comparing CSF and plasma pharmacokinetic parameters of intravenous aqueous vincristine to intravenous VSLI using an established non-human primate (NHP) model. Methods Three adult male rhesus monkeys (Macaca mulatta) were administered 0.1 mg/kg (1.2 mg/m² human-equivalent dose) of vincristine or VSLI in a crossover pharmacokinetic study. Serial paired blood and CSF samples were obtained before infusion, at the end of infusion (EOI) and at various time points thereafter. Results In contrast to standard vincristine, which had a multi-exponential plasma disappearance curve with a median initial (EOI to 30 min post-infusion) half-life (T_1/2) of 4.8 min (range, 4.4–5.0 min) and terminal T_1/2 of 24.3 h, a near-monoexponential curve with a median T_1/2 of 17.9 h (range, 13.9–21.5 h) hours was calculated with VSLI. The ratios Cl _VCR:Cl _VSLI for the individual NHP were 300, 463 and 477. Vincristine was not detected in any CSF sample after administration of either formulation. Conclusions In three animals, each serving as their own control, we demonstrate that the pharmacokinetic profile of VSLI shows markedly prolonged clearance (approximately 400-fold lower) of total vincristine in comparison to the standard aqueous formulation, enhancing our understanding of VSLI pharmacokinetics. Several clinical trials incorporating VSLI as substitution for standard vincristine are in progress.