Pharmacokinetic analysis of crushed venetoclax tablets combined with azacitizine for recurrent pediatric acute myeloid leukemia (AML)

Abstract Background: The efficacy of a combination therapy consisting of venetoclax (VEN) and azacytidine (AZA) for newly diagnosed acute myeloid leukemia (AML) has been confirmed in elderly patients. However, the clinical data on VEN for pediatric AML are limited. A combination therapy consisting of crushed VEN tablets and AZA (VEN/AZA) was administered to two children with recurrent AML. The pharmacokinetics of VEN were then analysed. Case Presentation: [Patient 1] A 1-year-old, male patient who experienced an AML relapse following an allogeneic hematopoietic stem cell transplantation received three courses of VEN/AZA. At the initial dosage of VEN (8 mg/kg), the minimum plasma concentration (Cmin) was only 0.44 μg/ml, which was far less than the optimal Cmin of 1.2 μg/ml. Subsequent dose-escalation to 10 mg/kg only achieved Cmin 0.42 μg/ml. [Patient 2] A 3-year-old, female patient in whom infantile acute lymphoblastic leukemia was originally diagnosed experienced a recurrence in the form of AML after lineage-switching. Three courses of VEN/AZA were administered with the same therapeutic drug monitoring as in Case 1. The Cmin of VEN was 0.15 μg/ml at 8 mg/kg. Afterwards, voliconazole 16 mg/kg/day was begun for a concomitant fungal infection together with VEN 2 mg/kg. This combination finally achieved Cmin 1.14 μg/ml probably through CYP3A4 inhibition by voriconazole. In terms of safety, only grade 4 hematological adverse events were observed in both patients. In terms of efficacy, patient 1 and patient 2 achieved stable disease status for two months and six months, respectively. Conclusion: Pediatric patients barely attain an effective plasma concentration of VEN when crushed tablets are used at the same dosage as in adults.