(T1430-07-38) Different Pharmacokinetics and Local Inflammation between Injectable Aqueous Drug Suspension and Oil Suspension

Purpose: Parenteral long-acting (LA) delivery systems including drug crystalline suspension are being clinical application and research, but the effect of delivery vehicle on the in vivo performance of injectable drug suspensions are still being questioned. Therefore, suspensions of entecavir-3-palmitate (EV-P), an ester prodrug of entecavir (EV), are manufactured using different vehicles that aqueous or oil to evaluate difference of vehicles. The purpose of this study is to investigate physicochemical properties (such as morphology, particle size, viscosity), in vitro release profiles, in vivo pharmacokinetics (PK) profiles and histological analysis of suspensions in different vehicles.

Methods: To manufacture aqueous suspension (AS) and oil suspension (OS), EV-P was selected by as model drug. Injectable AS of EV-P was prepared by an anti-solvent precipitation method and OS of EV-P was prepared by ultra-sonication employing tricaprylin as an oily vehicle, with low EV-P solubility. Morphology, size and zeta potential of suspensions was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and techniques of laser diffraction and zeta potential measurement. To evaluate thermal behavior of EV-P particles dispersed in AS or OS, differential scanning calorimetry (DSC) was used. Viscosity of suspensions was evaluated by rotational rheometer. In vitro release test was performed using dialysis membrane model. To investigate in vivo PK behaviors, and histological analysis for local tolerability, Uniform suspensions (OS or AS) were administered intramuscularly to the femoral tissue of the hind leg on Eight-week-old male Sprague-Dawley rats at a dose of 1.44 mg/kg (as EV). The level of EV in plasma was determined by HPLC mass spectroscopy (MS/MS) and PK parameters was calculated using PK analysis program. Histological observation in injection site was performed by using paraffin technique with H&E staining and histological parameter (such as the severity of local inflammation) was assessed quantitatively.

Results: In the result of physicochemical properties, OS and AS of EV-P were investigated both similarities and differences (Fig. 1.). Although viscosity and morphology of OS and AS were different, crystallinity, particle size (OS median diameter 2.7 μm, AS median diameter 2.6 μm) and in vitro release profiles (data not shown in paper) of OS and AS were similar. However, in vivo PK profiles of OS and AS showed different results (Fig. 2.). AUC_{(0-28 days)} obtained from IM injection of OS was approximately 18% higher than that IM injection of OS, Cmax of AS and OS obtained from OS treatment was more than 2.4-fold higher than that in the AS-treated group. Moreover, quantitative local inflammation evaulation revealed that OS lower than AS (Fig. 3.).

Conclusion: The present study examined the effects of different delivery systems (AS and OS) on the pharmacokinetic profiles of lipidic prodrug particles and local inflammatory responses at the injection site. The difference significantly affected the rate and extent of systemic exposure, displaying different C_max, elimination half-life, and AUC values. To the best of our knowledge, this study is the first attempt to compare the effects of different delivery vehicles on the in vivo performance of injectable suspensions, especially for identical drug candidate, suggesting the importance of dispersion medium of drug suspension in terms of pharmacokinetic profile and local inflammatory responses.

References: 1. N. Darville, M. van Heerden, D. Mariën, M. de Meulder, S. Rossenu, A. Vermeulen, A. Vynckier, S. de Jonghe, P. Sterkens, P. Annaert, G. van den Mooter, The effect of macrophage and angiogenesis inhibition on the drug release and absorption from an intramuscular sustained-release paliperidone palmitate suspension, Journal of Controlled Release. 230 (2016) 95–108. https://doi.org/10.1016/j.jconrel.2016.03.041
2. M.J. Ho, D.R. Lee, S.H. Im, J.A. Yoon, C.Y. Shin, H.J. Kim, S.W. Jang, Y.W. Choi, Y.T. Han, M.J. Kang, Microsuspension of fatty acid esters of entecavir for parenteral sustained delivery, International Journal of Pharmaceutics. 543 (2018) 52–59. https://doi.org/10.1016/j.ijpharm.2018.03.042.

Acknowledgments: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2022R1C1C1004561).

Fig. 1. Morphological and physical characteristics of EV-P OS and AS. (A) Scanning electron microscope (SEM) image of EV-P powder. Transmission electron microscopic (TEM) images of drug particles in (B) OS (C) AS, respectively. (D) Representative differential scanning calorimeter patterns of the raw material and EV-P suspensions. (E) Size distribution of EV-P particles in OS (●) and AS (○). (F) Representative viscosity curve of drug suspensions in the shearing rate of 1-100 sec-1.



Fig. 2. Plasma concentration-time profiles of EV following IM injection (1.44 mg/kg as EV) of EV-P OS (●) and AS (○) in rats. Data represent mean ± SD (n = 5).



Fig. 3. Temporal evolution of (A) numbers of inflammatory cells, (B) inflammatory area (mm2), and (C) fibrosis thickness (µm), following IM injection of EV-P suspensions in rats.