Sorafenib N-Oxide Is an Inhibitor of Human Hepatic CYP3A4

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Metabolic activation of tyrosine kinase inhibitors: recent advance and further clinical practice

At present, receptor tyrosine kinase signaling-related pathways have been successfully mediated to inhibit tumor proliferation and promote anti-angiogenesis effects for cancer therapy. Tyrosine kinase inhibitors (TKIs), a group of novel chemotherapeutic agents, have been applied to treat diverse malignant tumors effectively. However, the latent toxic and side effects of TKIs, such as hepatotoxicity and cardiotoxicity, limit their use in clinical practice. Metabolic activation has the potential to lead to toxic effects. Numerous TKIs have been demonstrated to be transformed into chemically reactive/potentially toxic metabolites following cytochrome P450-catalyzed activation, which causes severe adverse reactions, including hepatotoxicity, cardiotoxicity, skin toxicity, immune injury, mitochondria injury, and cytochrome P450 inactivation. However, the precise mechanisms of how these chemically reactive/potentially toxic species induce toxicity remain poorly understood. In addition, we present our viewpoints that regulating the production of reactive metabolites may decrease the toxicity of TKIs. Exploring this topic will improve understanding of metabolic activation and its underlying mechanisms, promoting the rational use of TKIs. This review summarizes the updated evidence concerning the reactive metabolites of TKIs and the associated toxicities. This paper provides novel insight into the safe use of TKIs and the prevention and treatment of multiple TKIs adverse effects in clinical practice.

A high throughput method for Monitoring of Sorafenib, regorafenib, cabozantinib and their metabolites with UPLC-MS/MS in rat plasma

As multi-targeted tyrosine kinase inhibitors, sorafenib, regorafenib and cabozantinib are widely used in hepatocellular carcinoma (HCC) for systemic therapies with anti-proliferative and anti-angiogenic effects. Nevertheless, adverse effects or insufficient efficacy appear frequently due to the plasma concentration with individual variability of these drugs. To ensure the curative effect and safety by therapeutic drug monitoring (TDM), this study developed a high throughput method to quantify sorafenib, regorafenib, cabozantinib and their active metabolites in plasma simultaneously. The chromatographic separation analysis achievement was performed on a Waters-ACQUITY UPLC BEH C18 column by UPLC-MS/MS system using a gradient elution of solvent A (acetonitrile) and solvent B (water with 0.1% formic acid) in 3.0 min. This method presented satisfactory results of specificity, precision (the intra-day coefficient of variation was between 2.5% and 6.6%, and the inter-day coefficient of variation was between 4.0% and 11.1%) and accuracy (within ±15% for intra-day and inter-day), as well as the stability under certain conditions, the matrix effect in plasma, and extraction recovery (75.6%–94.4%). The linearity of each analyte in the proper concentration scope indicated excellent. This study strictly complied with the performance rules of assay validation in biological medium proposed by FDA and was successfully applied to the pharmacokinetic study in rats. Thus, it would be an advantageous option to research the relationship between concentration-efficacy and concentration-toxic in HCC patients who were supposed to take these medications.

Herbacetin Broadly Blocks the Activities of CYP450s by Different Inhibitory Mechanisms

Herbacetin is a bioactive flavanol compound that has various pharmacological effects. However, the pharmacokinetic characteristics have not been thoroughly investigated. Previously, we screened a natural compound library and identified herbacetin as a potent CYP blocker. Herein, we aimed to mechanistically determine the inhibitory effects of herbacetin on CYP450 and its potential application. A human liver microsome incubation system was developed based on a UPLC-MS/MS method. Moreover, an in silico docking assay and a human CYP recombinase reaction system were developed and used to investigate binding affinity and inhibitory efficacy. Subsequently, the effects of the combination of herbacetin and sorafenib on HepG2 cells were assessed by MTT and immunoblotting assays. The concentration of sorafenib and its main metabolite were measured by UPLC-MS/MS after incubation with or without herbacetin. As a result, we found herbacetin almost completely inhibited the functions of major CYPs at 100 µM. Moreover, through analysis of the structure-activity relationship, we found 4-, 6-, and 8-hydroxyl were essential groups for the inhibitory effects. Herbacetin inhibited CYP3A4, CYP2B6, CYP2C9, and CYP2E1 in a mixed manner, but non-competitively blocked CYP2D6. These results are in good agreement with the recombinase reaction in vitro results, with an IC₅₀ < 10 µM for each tested isoenzyme. Interestingly, the stimulatory effects of sorafenib on HepG2 cell apoptosis were significantly enhanced by combining with herbacetin, which was associated with increased sorafenib exposure. In summary, herbacetin is a potent inhibitor of a wide spectrum of CYP450s, which may enhance the exposure of drugs in vivo.

Species differences in oxidative metabolism of regorafenib

Despite the prevalence of laboratory animals such as monkeys, rats, and mice in clinical drug trials, we know little regarding the oxidation of regorafenib in these test subjects. This study aimed to elucidate species differences in the kinetics of regorafenib oxidation into two metabolites: regorafenib N-oxide (M-2) and hydroxyregorafenib (M-3).M-2 formation best fitted the Hill equation and showed positive cooperativity in liver and small intestinal microsomes from all species. For all species, M-2 formation had a higher maximum velocity in microsomes from the liver than the small intestines. Maximum velocity was also higher in microsomes from humans and monkeys than those from rats and mice. M-3 formation was well-fitted to the Hill equation and showed positive cooperativity in all microsomes, except those from rat small intestines, where it exhibited biphasic kinetics. At half the maximum velocity, substrate concentration for M-2 and M-3 formation was lower in microsomes from humans than from other species. Moreover, M-2 was the major metabolite in microsomes from humans, monkeys, and mice, whereas M-2 and M-3 were the major metabolites in rat microsomes.M-2 and M-3 formation involving CYP3A4 and CYP3A5 fitted to the Hill equation. However, M-3 formation involving CYP2J2 fitted to the substrate inhibition model.Our study confirmed species differences in regorafenib oxidative metabolism.

Tissue engineered artificial liver model based on viscoelastic hyaluronan-collagen hydrogel and the effect of EGCG intervention on ALD

In alcoholic liver disease (ALD) research, animal models, as one of the most popular methods to explore pathology and therapeutic drug screening, show the limitations of expensive cost and ethic, as well as long modeling time. To minimize the use of animal models in ALD research, an artificial liver model has been developed by incorporating HepG2 cells into hydrogel matrix based on difunctional hyaluronan and collagen. And on this basis an alcohol-induced ALD model in vitro by adding alcohol in the engineering process has been established. Results showed that the construct exhibited a simulated synthetic and metabolic liver function thanks to the bionic fibrillar and viscoelastic characteristics of hydrogels. And the in vitro alcohol-induced ALD model was also proved to be successfully established, even presenting equal results with ALD mice. Furthermore, epigallocatechin gallate (EGCG) as an intervention on ALD was confirmed in both in vitro and in vivo model. The findings indicate our simple artificial liver model is not only highly predictive but also easy to apply to drug screening and implantation studies, suggesting a promising alternative to animal models. Moreover, as the main active ingredient of tea, EGCG's effective intervention and reversal effect on fatty liver provides support for the theory that green tea could prevent alcoholic fatty liver.

Pharmacokinetic Interaction between Sorafenib and Atorvastatin, and Sorafenib and Metformin in Rats

The tyrosine kinase inhibitor sorafenib is the first-line treatment for patients with hepatocellular carcinoma (HCC), in which hyperlipidemia and type 2 diabetes mellitus (T2DM) may often coexist. Protein transporters like organic cation (OCT) and multidrug and toxin extrusion (MATE) are involved in the response to sorafenib, as well as in that to the anti-diabetic drug metformin or atorvastatin, used in hyperlipidemia. Changes in the activity of these transporters may lead to pharmacokinetic interactions, which are of clinical significance. The study aimed to assess the sorafenib−metformin and sorafenib−atorvastatin interactions in rats. The rats were divided into five groups (eight animals in each) that received sorafenib and atorvastatin (I_SOR+AT), sorafenib and metformin (II_SOR+MET), sorafenib (III_SOR), atorvastatin (IV_AT), and metformin (V_MET). Atorvastatin significantly increased the maximum plasma concentration (C_max) and the area under the plasma concentration–time curve (AUC) of sorafenib by 134.4% (p < 0.0001) and 66.6% (p < 0.0001), respectively. Sorafenib, in turn, caused a significant increase in the AUC of atorvastatin by 94.0% (p = 0.0038) and its metabolites 2−hydroxy atorvastatin (p = 0.0239) and 4−hydroxy atorvastatin (p = 0.0002) by 55.3% and 209.4%, respectively. Metformin significantly decreased the AUC of sorafenib (p = 0.0065). The AUC ratio (II_SOR+MET group/III_SOR group) for sorafenib was equal to 0.6. Sorafenib did not statistically significantly influence the exposure to metformin. The pharmacokinetic interactions observed in this study may be of clinical relevance in HCC patients with coexistent hyperlipidemia or T2DM.

The oxidation and hypoglycaemic effect of sorafenib in streptozotocin-induced diabetic rats

Background

Diabetes reduces the activity of CYP3A4 and may increase the exposure for the drugs metabolized by the isoenzyme. Sorafenib is a multi-targeted tyrosine kinase inhibitor (TKI), used for the treatment of advanced renal cell carcinoma, hepatocellular carcinoma and radioactive iodine resistant thyroid carcinoma. The TKI undergoes CYP3A4-dependent oxidative transformation, which may be influenced by hyperglycaemia. The aim of the study was to compare the oxidation for sorafenib between healthy and streptozotocin-induced diabetic rats. Additionally, the effect of sorafenib on glucose levels was investigated.

Methods

The rats were assigned to the groups: streptozotocin-induced diabetic (DG, n = 8) or healthy (HG, n = 8). The rats received sorafenib orally as a single dose of 100 mg/kg. The plasma concentrations of sorafenib and its metabolite N-oxide were measured with the validated high-performance liquid chromatography with ultraviolet detection.

Results

The difference between groups in C_max and AUC_0−t values for sorafenib were significant (p = 0.0004, p = 0.0104), and similarly for the metabolite (p = 0.0008, p = 0.0011). Greater exposure for the parent drug and analysed metabolite was achieved in diabetic group. However, the C_max, AUC_0−t, and AUC_0−∞ ratios between the metabolite and sorafenib were similar in both groups. The significant reduction of glycaemia was observed only in the diabetic animals.

Conclusion

The findings of the study provide evidence that diabetes significantly influence on the exposition for sorafenib and its metabolite, but similar ratios N-oxide/sorafenib for AUC and C_max in healthy and diabetic animals suggest that oxidation of the TKI is rather unchanged. Additionally, sorafenib-associated hypoglycaemia was confirmed in diabetic animals.

Inhibition of Hepatic CYP2D6 by the Active N-Oxide Metabolite of Sorafenib

The multikinase inhibitor sorafenib (SOR) is used to treat patients with hepatocellular and renal carcinomas. SOR undergoes CYP-mediated biotransformation to a pharmacologically active N-oxide metabolite (SNO) that has been shown to accumulate to varying extents in individuals. Kinase inhibitors like SOR are frequently coadministered with a range of other drugs to improve the efficacy of anticancer drug therapy and to treat comorbidities. Recent evidence has suggested that SNO is more effective than SOR as an inhibitor of CYP3A4-mediated midazolam 1'-hydroxylation. CYP2D6 is also reportedly inhibited by SOR. The present study assessed the possibility that SNO might contribute to CYP2D6 inhibition. The inhibition kinetics of CYP2D6-mediated dextromethorphan O-demethylation were analyzed in human hepatic microsomes, with SNO found to be ~ 19-fold more active than SOR (K_is 1.8 ± 0.3 μM and 34 ± 11 μM, respectively). Molecular docking studies of SOR and SNO were undertaken using multiple crystal structures of CYP2D6. Both molecules mediated interactions with key amino acid residues in putative substrate recognition sites of CYP2D6. However, a larger number of H-bonding interactions was noted between the N-oxide moiety of SNO and active site residues that account for its greater inhibition potency. These findings suggest that SNO has the potential to contribute to pharmacokinetic interactions involving SOR, perhaps in those individuals in whom SNO accumulates.