Background: 6-Mercaptopurine (6-MP) is widely used to treat pediatric acute lymphoblastic leukemia
(ALL). Mini-tablets of 5 mg per tablet were developed for precision individual therapy for children and individuals
with poor thiopurine S-methyltransferase (TPMT) or nucleoside diphophate-linked moiety X-type motif 15
(NUDT15) metabolism. This study investigated the pharmacokinetic profiles of mini-tablets and conventional
tablets with an improved ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)
Methods: After giving 8 healthy beagle dogs 50 mg 6-MP in different dosage forms, plasma samples collected at
different time points were analyzed for pharmacokinetic evaluation. The samples were precipitated by methanol
with 0.05% formic acid and separated on a Waters Atlantis T3 column (2.1 × 150 mm, 3 μm particles) using 0.1%
formic acid in water and methanol at a flow rate of 0.4 mL/min in 4 min.
Results: This method showed good linearity, accuracy, precision and stability with a detection range of 5.0-500.0
ng/mL for 6-MP, 6-methylmercaptopurine (6-MMP) and 6-thioguanine (6-TG). The main parameters, half-life of
apparent terminal disposition, maximum observed plasma concentration, total AUC extrapolated to infinity, AUC
since initiation of the experiment, mean residence time, distribution volume and clearance were 1.62 ± 0.87 hours,
90.58 ± 60.43 ng/mL, 151.20 ± 94.18 ng·h/mL, 292.06 ± 184.02 ng·h2/mL, 1.90 ± 0.92 hours, 864.08 ± 538.52 L,
and 432.75 ± 360.64 L/h for conventional tablets and 1.70 ± 1.10 hours, 84.15 ± 39.50 ng/mL, 147.70 ± 51.80
ng·h/mL, 300.92 ± 124.48 ng·h2/mL, 2.07 ± 0.50 hours, 756.90 ± 324.00 L, and 340.75 ± 125.81 L/h for minitablets,
respectively. Paired t-tests showed no significant difference in any of the evaluated pharmacokinetic parameters
between the two types tablets (P > 0.05).
Conclusion: Two dosage forms showed the same pharmacokinetic characteristics. This developing, novel formulation
will help to provide a more accurate and optimal dosing regimen of 6-MP for humans in the future.