Abstract 1150: Pharmacokinetics and pharmacogenetics of liposomal cytarabine in AML patients treated with CPX-351

Abstract CPX-351 is a liposomal form encapsulating cytarabine and daunorubicin for treating Acute Myeloid Leukemia (AML) patients. Cytidine Deaminase (CDA) catabolizes free cytarabine in the liver, but to what extent it could affect as well the pharmacokinetics of liposomal cytarabine is yet to be investigated. Here we have studied the pharmacokinetics (PK) of released, liposomal and total cytarabine using a population-modeling approach in adult AML patients treated with CPX-351. Impact of CDA status (i.e., Poor Metabolizer (PM) vs. Extensive Metabolizer (EM)) on cytarabine exposure levels (AUC, trough levels, Cmax) and PK parameters were analyzed. All patients showed febrile neutropenia and one toxic-death was observed. Overall response rate was 75%. The ratio free:total cytarabine monitored in our patients was higher than expected (i.e., 47%). Inter-individual variability on pharmacokinetics parameters and subsequent exposure levels was >60%. A trend towards severe toxicities was observed in patients with higher exposure of cytarabine. Results showed that liposomal CPX-351 led to sustained exposure with reduced clearance (Cl = 0.16 L/h) and prolonged half-life (T1/2 = 28 h). Of note, liposomes were observed transiently in bone marrow on D15, with cytarabine levels 2.3-time higher than in plasma. Sequencing CDA gene was not contributive and CDA status was primarily evaluated upon phenotyping patients. PM status was found in 77% of the patients with a marked impact on cytarabine PK parameters, i.e., PM patients had higher exposure than EM patients (AUC: 5536 vs. 1784 ng/mL.h), prolonged half-life (T1/2: 33.9 vs. 13.7 h), and reduced clearance (Cl: 0.12 vs. 0.29 L/h). This pilot study suggests that despite being encapsulated in a liposomal vehicle as CPX-351, cytarabine fate in the body is highly dependent upon CDA activity, suggesting that liver metabolism is only partly skipped by the nanoparticle. Here, CDA status proved to have a major impact on cytarabine PK and possibly safety in AML patients treated with CPX-351. Indeed PM patients displayed higher exposure levels with higher risk for severe non-hematological toxicities. This study suggests that CDA status could be used as a covariate to customize CPX-351 dosing in AML patients. Citation Format: Melanie Donnette, Mourad Hamimed, Joseph Ciccolini, Regis Costello, Laure Delassus, Geoffroy Venton, Raphaelle Fanciullino. Pharmacokinetics and pharmacogenetics of liposomal cytarabine in AML patients treated with CPX-351 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1150.