ORIGINAL ARTICLES Department of Pharmaceutics1, School of Pharmacy, Qingdao University; Department of Thoracic Surgery2, Qingdao Central Hospital, Qingdao, China Pharmacokinetics of abiraterone acetate released from a tablet based on lipid matrix in beagle dogs H. ZHOU1, P. XU2, Y. SUN1,* Received November 23, 2020, accepted April 17, 2021 *Corresponding author: Yong Sun, Department of Pharmaceutics, School of Pharmacy, Qingdao University, Qingdao 266071, China [email protected] Pharmazie 76: 308-312 (2021) doi: 10.1691/ph.2021.0171 Objective: To compare the pharmacokinetic behavior of abiraterone acetate after oral administration of a lipid- based formulation tablet and a reference preparation, and to study the relative bioavailability of abiraterone acetate released from the lipid matrix-based tablet. Methods: Beagle dogs received a single dose orally. The experimental dosage was 75 mg/tablet, and the reference dosage was 250 mg/tablet. Six beagle dogs in each group were investigated with the method of 3 × 3 cross-administration. Blood plasma was collected and centri- fuged before administration and 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 h after administration, and the plasma samples were analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Results: The half-life (T1/2) values of lipid-based formulation (LBF) abiraterone acetate tablet samples (75 mg/tablet) and reference tablets (250 mg/tablet) after oral administration were 3.42 and 4.27 h, respectively, while the area under the concentration time curve (AUC0-t) (h·ng/mL) values were 107.71 and 52.83, respectively. The F value of the relative bioavailability was 704.80%. Conclusion: The preparation method based on lipid matrix can significantly improve the bioavailability of abiraterone acetate tablets, which is a feasible method to improve the bioavailability of biopharmaceutical classification system (BCS) class IV drugs. 1. Introduction In this study, we prepared a lipid-based formulation (LBF), which Prostate cancer, with strong pathological heterogeneity and only dissolved and dispersed the insoluble drug in the lipid matrix 28% 5-year survival rate, is the second deadliest cancer in men in a molecular state, followed by the addition of an appropriate (Desborough et al. 2008). Abiraterone acetate inhibits key enzymes surfactant, dispersion of the insoluble drugs in the unano-pore size in androgen synthesis and has an inhibitory effect on androgen absorbents, and preparation of the oral solid formulation (Becker production in testes and other parts of the body. Therefore, it is et al. 2015; Shukla et al. 2011). After oral administration, LBF used in the treatment of advanced prostate cancer (Malikova et al. reduces the particle size of abiraterone as much as possible under 2017; Schweizer and Antonarakis 2012). the action of surfactants; thus, insoluble abiraterone and molecular The concept of the biopharmaceutical classification system was intestinal juice form a small particle size microemulsion that is first proposed in 1995. The drugs are classified into four cate- easily absorbed by intestinal epithelial cells, which increases the gories depending on their solubility and intestinal membrane bioavailability of oral preparations and improves their efficacy permeability. Among them, the biopharmaceutical classification (Kyatanwar et al. 2010; Pouton 2000; Taylor and Zhang 2016; system (BCS) class IV drug include drugs with low solubility and Williams et al. 2013). poor ability to cross the small-intestine epithelial cell membrane The Lipid Formula Classification System (LFCS) was proposed (Amidon et al. 1995; Schultz et al. 2020a,b), resulting in low and by Pouton. LFCS divides LBF into four main types depending on variable bioavailability. Abiraterone belongs to the BCS class IV the ratios of surfactants and co-surfactants (Pouton 2000, 2006). category (Benoist et al. 2016; Schultz et al. 2020a,b). Owing to its A self-microemulsifying drug delivery system (SMEDDS) is a low intrinsic solubility, the absolute bioavailability of abiraterone type III lipid preparation, which is composed of lipids, surfactants, has not been successfully determined due to the inability to and co-surfactants. SMEDDS can effectively solve the problem of develop an acceptable intravenous formulation. The bioavail- formulating poorly soluble drugs with low solubility in the gastro- ability of abiraterone is 5% (Thakur 2015); however, since 92% intestinal fluids. Although the potential use of SMEDDS has been of abiraterone is metabolized to inactive metabolites in vivo, the known for some time, it has only been widely developed and used actual utilization rate is only 0.4% (Schultz et al. 2020a,b). in recent years. Many BCS class IV drug developments based on The traditional method to improve the solubility of insoluble drugs SMEDDS have been successful. mainly relies on improving their dispersion in aqueous solution To compare the bioavailability between abiraterone acetate LBF through the action of surfactants, which reduces the particle size and ordinary abiraterone acetate tablets, in this study we made of the drugs (Dokania and Joshi 2015; Larsen et al. 2008; Singh et abiraterone acetate LBF as tablet formulation, established the al. 2009). However, since the insoluble drugs and water belong to determination method of abiraterone acetate in beagles’ plasma by two-phase system, it is difficult to disperse the insoluble drugs in high performance liquid chromatography–tandem mass spectrom- the aqueous phase in the form of a single molecule, which results etry (HPLC–MS/MS), analyzed the pharmacokinetic parameters in large aggregate particle sizes of the insoluble drug, thereby of abiraterone acetate LBF and reference tablets after oral admin- limiting the effectiveness of this method in improving the insoluble istration, and provided references for the solid oral preparations of drugs’ bioavailability. abiraterone acetate (Benoist et al. 2016; Kim et al. 2017; Schultz 308 Pharmazie 76 (2021) ORIGINAL ARTICLES et al. 2020a,b; Solymosi et al. 2017a; Solymosi et al. 2017b; Xiao Table 1: Interday and intraday accuracy and precision of abiraterone et al. 2012). acetate in dog plasma Adding Interday Intraday 2. Investigations, results and discussion concentration Accuracy Precision Accuracy Precision (ng/mL) (RR, %, n = 18) (RSD, %, n = 18) (RR, %, n = 6) (RSD, %, n = 6) 2.1. Standard curve 1 4.52 4.50 3.68 12.89 The linear range was set wider and optimized through the determi- nation of the samples’ measured concentration in the later stage. 50 6.36 9.96 5.16 1.66 Specifically, it was 0.5–1000 ng/mL in the beginning, and it was 800 2.69 6.89 8.86 2.96 adjusted to 0.5–500 ng/mL in the end. The obtained standard curve equation was Abbreviations: RR - recall rate; RSD - relative standard deviation y = 0.01284x + 6.34261e−4, r2 = 0.99535 (weight coefficient 1/x2, n = 6), (1) indicating that a fine linear range was presented within the range of 0.5–1000 μg/mL. The deviations between the measured concentra- tion and theoretical concentration of all standard curved samples with different concentrations did not exceed 15% (the lower limit of quantitation [LLQQ] was not more than 20%). 2.2. Method specifi city Under the abovementioned chromatographic conditions, basically no endogenous characteristic peak of the blank plasma samples was observed within the range of 0–4 min. The retention time of abiraterone was 1.9 min (Fig. 1-A-II) and that of internal standard (carbamazepine) was 1.73 min (Fig. 1-B-II). Both abiraterone and carbamazepine achieved complete separation, which showed that the endogenous substances in the plasma did not interfere with the determination of abiraterone, indicating that this method had good specificity. Typical multi-response monitoring (MRM) chromato- grams of determination of abiraterone and carbamazepine in dog plasma are shown in Fig. 1. 2.3. Accuracy and precision The results of interday and intraday accuracy and precision of Fig. 2: The plasma concentration–time curve of abiraterone acetate after oral admin- abiraterone in dog plasma are shown in Table 1. Accuracy (recall istration of lipid-based formulation (LBF) abiraterone acetate tablet samples rate [RR], %) was between 2.69% and 8.86%, while precision (75 mg/tablet) in dogs (n = 6). (relative standard deviation [RSD], %) was not more than 12.89%, indicating that this method could be used for the determination of abiraterone in dog plasma. oral administration of LBF abiraterone acetate tablet samples (75 mg/tablet) are shown in Fig. 2, while the data for reference tablets (250 mg/tablet) are shown in Fig. 3. The average plasma 2.4. Plasma concentration data concentration–time data after oral administration of LBF abiraterone Nos. 1–5 were samples for test, and Nos. 6–10 were reference acetate tablet samples (75 mg/tablet) and those of reference tablets tablets. The plasma concentration–time data of abiraterone after (250 mg/tablet) are shown in Fig. 4. Fig. 1: Typical multi-response monitoring (MRM) chromatograms of abiraterone acetate and internal standard carbamazepine in dog plasma: (A) abiraterone acetate; (B) carba- mazepine; (I) chromatogram of blank plasma; (II) chromatogram of blank plasma with abiraterone acetate or carbamazepine. Pharmazie 76 (2021) 309 ORIGINAL ARTICLES Table 3: Pharmacokinetics parameters of abiraterone acetate after oral administration of reference tablets (250 mg/tablet) in dogs (n = 6) Dog No. 7 9 10 11 12 Mean SD Cmax 63.13 19.08 11.35 39.52 17.56 30.13 21.27 (ng/mL) Tmax (h) 1 0.5 0.75 1.5 0.75 0.9 0.38 AUC(0-t) 131.26 23.36 12.71 69.94 26.9 52.83 48.98 (h·ng/mL) T1/2 (h) 6.63 3.79 1.77 3.25 5.93 4.27 1.99 Abbreviations: AUC - area under the cure; Cmax - peak concentration; LBF - lipid-based formula- tion; SD - standard deviation; T1/2 - half-life; Tmax - peak time The half-life (T1/2) of the reference preparation group was 4.27±1.99 h.