Effects of 17α-ethynylestradiol-induced cholestasis on the pharmacokinetics of doxorubicin in rats: reduced biliary excretion and hepatic metabolism of doxorubicin

Implications of chronic moderate protein-deficiency malnutrition on doxorubicin pharmacokinetics and cardiotoxicity in early post-weaning stage

BACKGROUND

Malnutrition is a common problem in developing countries, and the impact of severe malnutrition on optimal treatment outcomes of chemotherapy in pediatric cancer patients is well documented. However, despite being a more prevalent and distinct entity, moderate malnutrition is until now unexplored for its effects on treatment outcomes.

AIMS

In this study we aimed to investigate the molecular basis of altered pharmacokinetics and cardiotoxicity of doxorubicin observed in early-life chronic moderate protein deficiency malnutrition.

MATERIALS AND METHODS

We developed an animal model of early-life moderate protein-deficiency malnutrition and validated it using clinical samples. This model was used to study pharmacokinetic and toxicity changes and was further utilized to study the molecular changes in liver and heart to get mechanistic insights.

KEY FINDINGS

Here we show that moderate protein-deficiency malnutrition in weanling rats causes changes in drug disposition in the liver by modification of hepatic ABCC3 and MRP2 transporters through the TNFα signalling axis. Furthermore, malnourished rats in repeat-dose doxorubicin toxicity study showed higher toxicity and mortality. A higher accumulation of doxorubicin in the heart was observed which was associated with alterations in cardiac metabolic pathways and increased cardiotoxicity.

SIGNIFICANCE

Our findings indicate that moderate malnutrition causes increased susceptibility towards toxic side effects of chemotherapy. These results may necessitate further investigations and new guidelines on the dosing of chemotherapy in moderately malnourished pediatric cancer patients.

Molecular insights into experimental models and therapeutics for cholestasis

Cholestatic liver disease (CLD) is a range of conditions caused by the accumulation of bile acids (BAs) or disruptions in bile flow, which can harm the liver and bile ducts. To investigate its pathogenesis and treatment, it is essential to establish and assess experimental models of cholestasis, which have significant clinical value. However, owing to the complex pathogenesis of cholestasis, a single modelling method can merely reflect one or a few pathological mechanisms, and each method has its adaptability and limitations. We summarize the existing experimental models of cholestasis, including animal models, gene-knockout models, cell models, and organoid models. We also describe the main types of cholestatic disease simulated clinically. This review provides an overview of targeted therapy used for treating cholestasis based on the current research status of cholestasis models. In addition, we discuss the respective advantages and disadvantages of different models of cholestasis to help establish experimental models that resemble clinical disease conditions. In sum, this review not only outlines the current research with cholestasis models but also projects prospects for clinical treatment, thereby bridging basic research and practical therapeutic applications.

Phase I Study of Elraglusib (9-ING-41), a Glycogen Synthase Kinase-3β Inhibitor, as Monotherapy or Combined with Chemotherapy in Patients with Advanced Malignancies

PURPOSE

The safety, pharmacokinetics, and efficacy of elraglusib, a glycogen synthase kinase-3β (GSK-3β) small-molecule inhibitor, as monotherapy or combined with chemotherapy, in patients with relapsed or refractory solid tumors or hematologic malignancies was studied.

PATIENTS AND METHODS

Elraglusib (intravenously twice weekly in 3-week cycles) monotherapy dose escalation was followed by dose escalation with eight chemotherapy regimens (gemcitabine, doxorubicin, lomustine, carboplatin, irinotecan, gemcitabine/nab-paclitaxel, paclitaxel/carboplatin, and pemetrexed/carboplatin) in patients previously exposed to the same chemotherapy.

RESULTS

Patients received monotherapy (n = 67) or combination therapy (n = 171) elraglusib doses 1 to 15 mg/kg twice weekly. The initial recommended phase II dose (RP2D) of elraglusib was 15 mg/kg twice weekly and was defined, without dose-limiting toxicity observation, due to fluid volumes necessary for drug administration. The RP2D was subsequently reduced to 9.3 mg/kg once weekly to reduce elraglusib-associated central/peripheral vascular access catheter blockages. Other common elraglusib-related adverse events (AE) included transient visual changes and fatigue. Grade ≥3 treatment-emergent AEs occurred in 55.2% and 71.3% of patients on monotherapy and combination therapy, respectively. Part 1 monotherapy (n = 62) and part 2 combination (n = 138) patients were evaluable for response. In part 1, a patient with melanoma had a complete response, and a patient with acute T-cell leukemia/lymphoma had a partial response (PR). In part 2, seven PRs were observed, and the median progression-free survival and overall survival were 2.1 [95% confidence interval (CI), 2-2.6] and 6.9 (95% CI, 5.7-8.4) months, respectively.

CONCLUSIONS

Elraglusib had a favorable toxicity profile as monotherapy and combined with chemotherapy and was associated with clinical benefit supporting further clinical evaluation in combination with chemotherapy.

Consecutive baicalin treatment relieves its accumulation in rats with intrahepatic cholestasis by increasing MRP2 expression

Baicalin, an important flavonoid isolated from Scutellaria baicalensis Georgi, is a Chinese herb widely used in clinical practice. We previously reported the in vivo accumulation of baicalin in rats with intrahepatic cholestasis (IHC) after a single dose. However, the effects of the long-term administration of baicalin on its pharmacokinetics are unknown. Thus, we investigated the disposition of baicalin in normal rats and those with IHC after single and multiple consecutive administrations. In addition, we further investigated the effect of baicalin on multidrug resistance protein 2 (MRP2) in vivo to explore the underlying mechanism. In our study, the liquid chromatography-mass spectrometry (LC-MS) method established to determine baicalin concentrations in rat blood was simple, specific, and with linearity (R² = 0.9980) in the range of 1.01-506.00 μg/mL. The relative standard deviations (RSD) for intra-day and inter-day precision were not more than 10.55%, and the intra-day and inter-day accuracies were 94.94%-109.13%. The recovery rate and stability were in line with the requirements of the quantitative analysis of biological samples as stated in the Chinese Pharmacopoeia (2020 Edition). Compared with that in normal rats, the C_max and t_1/2 increased significantly in EE-induced rats with IHC, whereas the clearance (CL) decreased after a single administration of baicalin. However, the area under the curve decreased, CL increased, and the t_1/2 was shortened after the continuous administration of baicalin in the IHC rat model compared with the single administration of baicalin, and the pharmacokinetic characteristics were similar to those in normal rats. Moreover, MRP2 expression increased in rats with IHC with the continuous administration of baicalin. Continuous baicalin intervention could effectively reduce its accumulation in rats with IHC, and the mechanism may be attributed to its enhancement of MRP2 expression.

A Novel Integrated Pharmacokinetic-Pharmacodynamic Model to Evaluate Combination Therapy and Determine In Vivo Synergism

Understanding pharmacokinetic (PK)-pharmacodynamic (PD) relationships is essential in translational research. Existing PK-PD models for combination therapy lack consideration of quantitative contributions from individual drugs, whereas interaction factor is always assigned arbitrarily to one drug and overstretched for the determination of in vivo pharmacologic synergism. Herein, we report a novel generic PK-PD model for combination therapy by considering apparent contributions from individual drugs coadministered. Doxorubicin (Dox) and sorafenib (Sor) were used as model drugs whose PK data were obtained in mice and fit to two-compartment model. Xenograft tumor growth was biphasic in mice, and PD responses were described by three-compartment transit models. This PK-PD model revealed that Sor (contribution factor = 1.62) had much greater influence on overall tumor-growth inhibition than coadministered Dox (contribution factor = 0.644), which explains the mysterious clinical findings on remarkable benefits for patients with cancer when adding Sor to Dox treatment, whereas there were none when adding Dox to Sor therapy. Furthermore, the combination index method was integrated into this predictive PK-PD model for critical determination of in vivo pharmacologic synergism that cannot be correctly defined by the interaction factor in conventional models. In addition, this new PK-PD model was able to identify optimal dosage combination (e.g., doubling experimental Sor dose and reducing Dox dose by 50%) toward much greater degree of tumor-growth inhibition (>90%), which was consistent with stronger synergy (combination index = 0.298). These findings demonstrated the utilities of this new PK-PD model and reiterated the use of valid method for the assessment of in vivo synergism. SIGNIFICANCE STATEMENT: A novel pharmacokinetic (PK)-pharmacodynamic (PD) model was developed for the assessment of combination treatment by considering contributions from individual drugs, and combination index method was incorporated to critically define in vivo synergism. A greater contribution from sorafenib to tumor-growth inhibition than that of coadministered doxorubicin was identified, offering explanation for previously inexplicable clinical observations. This PK-PD model and strategy shall have broad applications to translational research on identifying optimal dosage combinations with stronger synergy toward improved therapeutic outcomes.

Dose-Dependent Pharmacokinetics of Tofacitinib in Rats: Influence of Hepatic and Intestinal First-Pass Metabolism

This study investigated the pharmacokinetics of tofacitinib in rats and the effects of first-pass metabolism on tofacitinib pharmacokinetics. Intravenous administration of 5, 10, 20, and 50 mg/kg tofacitinib showed that the dose-normalized area under the plasma concentration-time curve from time zero to infinity (AUC) was significantly higher at 50 mg/kg than at lower doses, a difference possibly due to saturation of the hepatic metabolism of tofacitinib. Oral administration of 10, 20, 50, and 100 mg/kg tofacitinib showed that the dose-normalized AUC was significantly higher at 100 mg/kg than at lower doses, a difference possibly due to saturation of the intestinal metabolism of tofacitinib. Following oral administration of 10 mg/kg tofacitinib, the unabsorbed fraction from the rat intestine was 3.16% and the bioavailability (F) was 29.1%. The AUC was significantly lower (49.3%) after intraduodenal, compared to intraportal, administration, but did not differ between intragastric and intraduodenal administration, suggesting that approximately 46.1% of orally administered tofacitinib was metabolized through an intestinal first-pass effect. The AUC was also significantly lower (42%) after intraportal, compared to intravenous, administration, suggesting that the hepatic first-pass effect on tofacitinib after entering the portal vein was approximately 21.3% of the oral dose. Taken together, these findings suggest that the low F of tofacitinib is due primarily to intestinal first-pass metabolism.

Pharmacokinetic Characteristics of Baicalin in Rats with 17α-ethynyl-estradiol-induced Intrahepatic Cholestasis

Baicalin is one of the main active ingredients of choleretic traditional Chinese medicine drug Radix Scutellariae. The aim of this study was to explore the pharmacokinetic characteristics of baicalin in rats with 17α-ethynylestradiol (EE)-induced intrahepatic cholestasis (IC) based on its choleretic effects. Firstly, rats were subcutaneously injected with EE solution (5 mg/kg, 0.25 mL/100 g) for 5 consecutive days to construct an IC model. Then the bile excretion rate, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and total bile acid (TBA) and pathological changes of the liver were detected. Secondly, after successfully modeling, the rats were intragastrically given baicalin solution (200 mg/kg) (n=6). Blood samples were collected from the tail vein at different time points after intragastric administration. The protective effects of low- (50 mg/kg), medium- (100 mg/kg) and high-dose (200 mg/kg) baicalin on the liver in IC rats were evaluated. The content of baicalin in plasma was detected by liquid chromatography-mass spectrometry/mass spectrometry and pharmacokinetics parameters were calculated. Pharmacodynamic results showed that low-, medium- and high-dose baicalin all significantly increased the average excretion rate of bile (P<0.05), and significantly decreased serum levels of ALT, AST and ALP and TBA (P<0.05). Meanwhile, HE staining showed that baicalin significantly relieved EE-induced hepatocyte edema and necrosis. Pharmacokinetic results exhibited that the absorption of baicalin in both IC and normal control rats showed bimodal phenomenon. C_max, AU_(0-t) and AUC_(0-∞) of baicalin in IC rats were significantly higher than those of the normal control group (P<0.01). T_1/2 of plasma baicalin in the model group was significantly extended to (11.09±1.84) h, with clearance dropping to 61.78% of that of the normal control group (P<0.01). The above results suggested that baicalin had protective effects on the liver of IC rats, accompanied by significantly increased in vivo exposure, delayed in vivo clearance and markedly alterative pharmacokinetic characteristics. This study provides a theoretical basis for further development of baicalin as a feasible drug for treating IC.

Effect of Liver Disease on Hepatic Transporter Expression and Function

Liver disease can alter the disposition of xenobiotics and endogenous substances. Regulatory agencies such as the Food and Drug Administration and the European Medicines Evaluation Agency recommend, if possible, studying the effect of liver disease on drugs under development to guide specific dose recommendations in these patients. Although extensive research has been conducted to characterize the effect of liver disease on drug-metabolizing enzymes, emerging data have implicated that the expression and function of hepatobiliary transport proteins also are altered in liver disease. This review summarizes recent developments in the field, which may have implications for understanding altered disposition, safety, and efficacy of new and existing drugs. A brief review of liver physiology and hepatic transporter localization/function is provided. Then, the expression and function of hepatic transporters in cholestasis, hepatitis C infection, hepatocellular carcinoma, human immunodeficiency virus infection, nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, and primary biliary cirrhosis are reviewed. In the absence of clinical data, nonclinical information in animal models is presented. This review aims to advance the understanding of altered expression and function of hepatic transporters in liver disease and the implications of such changes on drug disposition.

Role of rat cytochromes P450 in the oxidation of 17α-ethinylestradiol

17α-Ethinylestradiol (EE2) is an endocrine disruptor (ED) used as an ingredient of oral contraceptives. Rat hepatic microsomes metabolize EE2 to three products; two of them are hydroxylated EE2 derivatives. Of the hydroxylation reactions, 2-hydroxylation, is the major reaction. Cytochrome P450 (CYP) plays a major role in EE2 hydroxylation. To resolve which rat CYPs are responsible for EE2 oxidation, three approaches were used: induction of specific CYPs, selective inhibition of CYPs, and recombinant rat CYPs. The results demonstrate that EE2 is hydroxylated by several rat CYPs, among them CYP2C6 and 2C11 are most efficient in 2-hydroxy-EE2 formation, while CYP2A and 3A catalyze EE2 hydroxylation to the second product. EE2 is also an inhibitor of CYP2C- and CYP3A-catalyzed hydroxylation of endogenous EDs progesterone and testosterone. EE2 acts as a reversible inhibitor of CYP3A-mediated progesterone 6β-hydroxylation and inactivates CYP3A- and CYP2C-catalyzed testosterone 6β-hydroxylation and progesterone 21- or 16α-hydroxylation, respectively, in a mechanism-based manner.

Drug disposition alterations in liver disease: extrahepatic effects in cholestasis and nonalcoholic steatohepatitis

INTRODUCTION

The pharmacokinetics (PK) of drugs and xenobiotics, namely pharmaceuticals, is influenced by a host of factors that include genetics, physiological factors and environmental stressors. The importance of disease on the disposition of xenobiotics has been increasingly recognized among medical professionals for alterations in key enzymes and membrane transporters that influence drug disposition and contribute to the development of adverse drug reactions.

AREAS COVERED

This review will survey pertinent literature of how liver disease alters the PKs of drugs and other xenobiotics. The focus will be on nonalcoholic steatohepatitis as well as cholestatic liver diseases. A review of basic pharmacokinetic principles, with a special emphasis on xenobiotic metabolizing enzymes and membrane transporters, will be provided. Specifically, examples of how genetic alterations affect metabolism and excretion, respectively, will be highlighted. Lastly, the idea of 'extrahepatic' regulation will be explored, citing examples of how disease manifestation in the liver may affect drug disposition in distal sites, such as the kidney.

EXPERT OPINION

An expert opinion will be provided highlighting the definite need for data in understanding extrahepatic regulation of membrane transporters in the presence of liver disease and its potential to dramatically alter the PK and toxicokinetic profile of numerous drugs and xenobiotics.