Bioequivalence study followed by model‐informed dose optimization of a powder for oral suspension of 6‐mercaptopurine

Abstract Background 6‐Mercaptopurine (6MP) is the mainstay chemotherapy for acute lymphoblastic leukemia (ALL) and is conventionally available as 50 mg tablets. A new 6MP powder for oral suspension (PFOS 10 mg/mL) was developed recently by IDRS Labs, India, intended for pediatric use. A comparative pharmacokinetics of PFOS with T. mercaptopurine was conducted to determine the dose equivalence. Methods An open‐label, randomized, two‐treatment, two‐period, two‐sequence, single oral dose, crossover, bioequivalence study was conducted on 51 healthy adult subjects. Post hoc, a population pharmacokinetic (PopPK) model was developed using the healthy volunteer data to perform simulations with various PFOS doses and select a bioequivalent dose. Further, to confirm the safety of PFOS in pediatrics, a simulation of 6MP and 6‐thioguanine exposures was performed by incorporating the formulation‐specific parameters derived from the healthy volunteer study into the PopPK model in childhood ALL available in literature. Results The 6MP PFOS had 47% higher oral bioavailability compared to the reference product. Simulations using a two‐compartmental PopPK model with dissolution and transit compartments showed that 40 mg of PFOS was found to be equivalent to 50 mg tablets. The simulated 6‐thioguanine nucleotide concentrations in children using the dose adjusted for PFOS were between 114 and 703.6 pmol/8 × 10 8 RBC, which was within the range reported in pediatric ALL studies. Conclusion 6MP PFOS 10 mg/mL should be administered at a 20% lower dose than the tablet to achieve comparable exposure. 6MP PFOS addresses an unmet medical need for a liquid formulation of 6MP in the Indian subcontinent.