(M1030-06-34) Investigating Bioequivalence of Antimalarial Formulations Using In Vitro and In Silico Biopharmaceutics Tools

Purpose: For bioequivalence studies, clinical trials need to be carried out. These trials can be lengthy and costly. In recent years, regulatory bodies have encouraged the use of in vitro and in silico biopharmaceutics tools to support the demonstration of bioequivalence between reference and test products with the aim of reducing or replacing extensive clinical testing. The purpose of the study was to investigate the bioequivalence of two oral immediate-release formulations of the antimalarial agent piperaquine (PQP) with the use of a physiologically based pharmacokinetic (PBPK) modeling informed with bio-predictive dissolution data.

Methods: In Vitro Biorelevant Dissolution Testing: Dissolution experiments were conducted for a tablet and a granule formulation (PQP dose of 160 mg) in three set ups: (1) single-stage, USP II (closed system), (2) two-stage, USP II (closed system) and (3) two-stage, USP IV (open system). Single-stage experiments were carried out in 250 mL of fasted state simulated gastric fluid (FaSSGF) [1] at 75 rpm or 250 mL of fasted state simulated intestinal fluid (FaSSIF-V2) [1] at 100 rpm. In the USP II-two-stage experiments, the addition of FaSSIF occurred after 30 min and the agitation speed was 50 rpm. In the USP IV studies, formulations were exposed to FaSSGF at 12 mL/min for 30 min followed by FaSSIF-V2 at 4 mL/min for 240 min. 2 mL samples were collected at pre-specified timepoints and analysed by HPLC. All experiments were conducted in triplicate at 37^oC. In Silico Bioequivalence: A PBPK model for piperaquine was developed using Simcyp® software v22 (Certara, UK). The physicochemical parameters of PQP were extracted from the literature. PQP distribution was described with a full PBPK model and absorption was initially described using a first-order model [2]. The model was optimized and validated with data from a clinical trial provided by the Medicines for Malaria Venture (MMV) in which 27 healthy fasted adult subjects were given 960 mg of PQP as either the tablet or the granule formulation. Once the first-order model was validated, the Advanced Dissolution Absorption and Metabolism (ADAM) model in SimCYP® was used in order to get a mechanistic understanding of the absorption process. The biorelevant dissolution profiles were input as discrete profiles. The healthy volunteer population available in SimCYP® was used with 10 virtual trials of 10 subjects per trial.

Results: Rapid dissolution of PQP from both formulations was observed in gastric conditions due to the weakly basic nature of PQP (pKa = 7.4, 8.8). In intestinal media, an initial parachuting effect was observed with a subsequent drop in the percentage dissolved, which remained below 20% due to the low solubility of PQP at the higher pH of the intestine. In the USP II two-stage experiments, precipitation of PQP occurred upon the simulation of stomach-to-intestinal transfer. The in vitro AUC_0-240min ratio of tablet-to-granule was between 0.80-1.25 for all the set ups explored, similar to the in vivo AUC_0-∞ ratio of tablet-to-granule (0.99), revealing in vitro bioequivalence. The in silico predicted pharmacokinetic profiles for both formulations were comparable when the two stage USP II dissolution profile was used as an input, with an AUC_0-∞ ratio of tablet-to-granule of 0.88 (Figure 1). This was in agreement with the observed AUC_0-∞ ratio indicating that bioequivalence between the two formulations could successfully be predicted in silico.

Conclusion: The bioequivalence between the tablet and the granule PQP formulation was demonstrated with the use of in vitro biorelevant dissolution data and PBPK modeling. The use of such in vitro and in silico tools to reveal bioequivalence between formulations could accelerate drug development process.

References: 1. Jantratid, E., Janssen, N., Reppas, C., Dressman, J.B. Dissolution media simulating conditions in the proximal human gastrointestinal tract: an update. Pharmaceutical Research, 2008. 25 (7): 1663-1676.
2. Abla, N., Howgate, E., Rowland-Yeo, K., Dickins, M., Bergagnini-Kolev, M.C., Chen, K.F., McFeely, S., Bonner, J.J., Santos, L.G.A., Gobeau, N., Burt, H., Barter, Z., Jones, H.M., Wesche, D., Charman, S.A., Mohrle, J.J., Burrows, J.N., Almond, L.M. Development and application of a PBPK modeling strategy to support antimalarial drug development. CPT: Pharmacometrics and Systems Pharmacology, 2023. 12 (9): 1335-1346.

Acknowledgements: This publication is based on research funded in part by the Gates Foundation. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Gates Foundation.


Simulated (straight line) and observed in vivo (individual circles) plasma concentration-time profiles of the PQP tablet (blue) and granule formulation (red) in healthy adults in fasted state. [ n = 14 for the tablet and n = 13 for the granule; grey doted lines represent the 5th and 95th percentile of the simulated population].