Fig. 3: Inactivation of anti-leukaemic drugs by glucuronidation in human metabolic tissues, B-cell models, and detected in CLL patients.

a Fludarabine, ibrutinib or idelalisib glucuronidation by human liver microsomes generated two glucuronidated metabolites G1 and G2 for each drug separated by liquid chromatography and named according to their order of elution. MS fragmentation patterns confirmed the glucuronidated nature of metabolites with the loss of the glucuronic acid (GlcA) moiety corresponding to a m/z shift of 176 Da. Masses of the protonated drug-glucuronide [M + H]⁺ and parent drug [M-G + H]⁺ are shown and were in accordance with those of the parent drugs alone and of GlcA. Their identity was confirmed upon β-glucuronidase hydrolysis (not shown). b Identification of UGT2B17 and UGT1A4 enzymes primarily targeting anti-leukaemic drugs for glucuronidation using quantitative MS methods. The screening included human liver, intestine and kidney that are enriched in UGTs and individual recombinant UGT1A (n = 8) and UGT2B (n = 6) enzymes. c Detection of fludarabine-G in plasma samples of two CLL patients collected in the first week after fludarabine treatment. Peaks corresponding to fludarabine-G are highlighted. d Concentrations of ibrutinib-G and the parent drug measured by quantitative MS in two CLL patients undergoing ibrutinib treatment collected at baseline (T₀), 3 weeks to 2 months (T₁) and between 4 and 9 months (T₂) after treatment initiation. Patients’ characteristics are displayed in Table S4.