Genetic characterization to improve interpretation and clinical management of hepatotoxicity caused by tyrosine kinase inhibitors

Thiazolobenzamide-Naphthalene Hybrids as Potent Anticancer agents compared to Doxorubicin: Design, Synthesis, SAR, In-silico and Toxicity Analysis

In order to determine whether thiazolobenzamide molecules connected to naphthalene could inhibit the growth of three different tumor cell lines, MCF7 (breast carcinoma), A549 (pulmonary carcinoma), and DU145 (prostatic adenocarcinoma) a novel series of ten molecules, designated TA 1-10, was designed, synthesized, and tested. Among these compounds, TA7 showed promising results against cell lines, especially showing exceptional efficacy against breast cancer. Antioxidant activity tests consistently showed the best performance from the TA7 molecule. Furthermore, when a dose of 50 to 500 mg/kg of the total mass of rats is given, the most effective chemical, TA7, did not exhibit any harmful effects during acute oral toxicity tests. The biochemical indicators (SGOT and SGPT) for hepatotoxicity associated with compound TA7 were found to be fairly similar to those of the control group. The findings from molecular docking, XP visualization, and MM-GBSA dG binding investigations are in agreement with the outcomes of in-vitro tests of antioxidant and anticancer capabilities. TA7 was the most effective compound among those that were docked; it bound free energy and had adequate properties for metabolism (biochemical processes), distribution (dispersion), absorption (assimilation), and excretion (elimination). This study found that the TA7 molecule, a thiazole ring system derivative connected to naphthalene, is to be a promising and possible anticancer agent and its efficacy may be further explored in clinical studies.

Severe tyrosine-kinase inhibitor induced liver injury in metastatic renal cell carcinoma patients: two case reports assessed for causality using the updated RUCAM and review of the literature

Background

Sunitinib and pazopanib are both oral small molecule multityrosine kinase inhibitors (MTKI) used in the treatment of renal cell carcinoma (RCC). Hepatotoxicity or “liver injury” is the most important adverse effect of pazopanib administration, but little is known about the underlying mechanism. Liver injury may also occur in patients treated with sunitinib, but severe toxicity is extremely rare. Herein we report two new cases of severe liver injury induced by MTKI. Both cases are unique and exceptional. We assessed both cases for drug-induced liver injury (DILI) using the updated score Roussel Uclaf causality assessment method (RUCAM). The literature on potential pathogenic mechanisms and precautionary measures is reviewed.

Case presentation

A case of a metastatic RCC (mRCC) patient treated with pazopanib who had manifestation of severe liver injury is presented. These manifestations consisted of grade 4 alanine aminotransferase (ALT) increase and grade 4 hyperbilirubinemia. Alternate causes of acute or chronic liver disease were excluded. The patient gradually recovered from the liver injury and refused any further therapy for mRCC. The patient was diagnosed with acute myeloid leukemia (AML) two years later and eventually succumbed to the disease. The second case describes a mRCC patient treated with sunitinib for 3,5 years and fatal liver failure after 2 weeks of clarithromycin co-medication for acute bronchitis.

Conclusions

Liver injury has been commonly observed in TKI-treated patients with unpredictable course. Management requires regular routine liver enzyme-monitoring and the collaboration of medical oncologist and hepatologist. There is an unmet medical need for a risk stratification and definition of predictive biomarkers to identify potential genetic polymorphisms or other factors associated with TKI-induced liver injury. Any potential unrecommended concomitant therapy has to be avoided.

Furanone-functionalized benzothiazole derivatives: synthesis, in vitro cytotoxicity, ADME, and molecular docking studies

In the present study, a novel series of new furanone-based benzothiazole derivatives (4a-j) were synthesized from 4-(benzo[d]thiazol-2-yl)-4-oxobutanoic acid (3) as potential anticancer agents. In vitro cytotoxicity against three human cancer cell lines (A549, MCF7, and DUI45) revealed substantial activity. Di-substituted compound, 4i emerged as a promising anticancer compound which showed IC50 values of 7.2 ± 0.5, 6.6 ± 1.4, and 7.3 ± 0.1 µM against A549, MCF7, and DUI45 cell lines, respectively. Four compounds 4c, 4e, 4f, and 4i evaluated for their acute toxicity were found to be non-toxic on the two vital organs (liver and heart). Further, these compounds were found to be more efficient and less hepatotoxic in comparison to standard drug doxorubicin. Molecular docking studies carried out with VEGFR-2 revealed compounds 4a and 4i as potential VEGFR-2 kinase inhibitors. In silico ADME evaluation was carried out to estimate and predict drug-likeness. Compound 4i demonstrated the best ADME parameters. Based on the results of docking analyses, ADME, and in vitro cytotoxicity, compound 4i is identified as the lead compound for further development of anticancer agents.

Evaluation of the effect of UGT1A1 polymorphisms on the pharmacokinetics of oral and long-acting injectable cabotegravir

Background

Cabotegravir is an HIV integrase inhibitor in clinical development with both oral and long-acting (LA) injectable formulations. Cabotegravir is primarily metabolized by uridine 5′-diphospho-glucuronosyltransferase (UGT) 1A1, a known polymorphic enzyme with functional variants that can affect drug metabolism and exposure.

Objectives

To investigate the pharmacogenetic effects of the reduced-function alleles UGT1A1*6, UGT1A1*28 and/or UGT1A1*37 on steady-state pharmacokinetics (PK) and safety of oral cabotegravir (30 mg/day) and intramuscular cabotegravir LA (400 mg every 4 weeks or 600 mg every 8 weeks).

Methods

Plasma cabotegravir PK was assessed in 346 UGT-genotyped participants with and without UGT1A1 functional variants across six studies (four Phase I and two Phase II) of oral cabotegravir, including 215 HIV-infected participants who received oral cabotegravir followed by cabotegravir LA. Changes from baseline in total bilirubin and ALT were assessed in one study (LATTE; NCT01641809).

Results

Statistically significant (P < 0.05) associations were observed between UGT1A1 genotype and plasma cabotegravir PK parameters, with 28%–50% increases following oral cabotegravir [plasma cabotegravir concentration at the end of the dosing interval (C_tau), 1.50-fold; AUC_tau, 1.41-fold; and C_max, 1.28-fold] and 16%–24% increases following cabotegravir LA administration (48 week C_tau, 1.24-fold; AUC_tau, 1.16-fold; and C_max, 1.18-fold) among those with low-versus-normal genetically predicted UGT1A1 activity. A statistically significant (P < 10⁻⁵) association between predicted UGT1A1 activity and maximum change in total bilirubin was also observed (2.45-fold asymptomatic increase for low versus normal) without a corresponding change in ALT.

Conclusions

This modest increase in oral and parenteral cabotegravir exposure associated with a reduced function of UGT1A1 is not considered clinically relevant based on accumulated safety data; no dose adjustment is required.

Anlotinib, a novel TKI, as a third-line or further-line treatment in patients with advanced non-small cell lung cancer in China: A systemic review and meta-analysis of its efficacy and safety

PURPOSE

In this meta-analysis and systemic review, we focused on the effectiveness and safety of anlotinib in patients with advanced non-small cell lung cancer(NSCLC).

METHODS

The databases of PubMed, EMBASE, Cochrane Library, CNKI, Wanfang, and CBM were searched by 2 investigators up to April 2020. Titles and abstracts of all records were screened and eligible publications were retrieved in full. Review Manager (version 5.2, Cochrane Library) was used for data analysis. The outcomes of interest were disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and treatment-related adverse event (TRAE). Data was pooled for quantitative analysis and the effect size was reported as hazard ratio for survival outcomes and odds ratio (OR) for safety outcomes, both with a random-effects model.

RESULTS

A sum of 1480 patients were included in 11 trials ranging from 2018 to 2020. Substantial improvements of PFS, OS, and DCR were observed in patients treated with anlotinib alone or in combination with other conventional treatment. Accompanied TRAE included statistically significant higher risk for hypertension (OR = 11.05, 95% confidence interval [CI] = 7.85-15.55, P < .001), hepatic dysfunction (OR = 1.96, 95% CI = 1.29-2.68, P < .001), diarrhea (OR = 2.20, 95% CI = 1.17-4.16, P < .05), and hemoptysis (OR = 2.59, 95% CI = 1.71-3.93, P < .01).

CONCLUSIONS

Our study suggested that anlotinib as maintenance therapy for advanced NSCLC patients is associated with prolonged PFS and OS as well as DCR improvement, but it was accompanied by increased risk of TRAE, such as hypertension, hepatic dysfunction, diarrhea and hemoptysis. Although much effort has been made to clinical trials of anlotinib, further studies are warranted to provide more convincing evidence.

Suppression of systemic inflammation and signs of acute and chronic cholangitis by multi-kinase inhibitor 1-(4-Cl-benzyl)-3-chloro-4-(CF3-phenylamino)-1H-pyrrole-2,5-dione

An aberrant activity of growth factor receptors followed by excessive cell proliferation plays a significant role in pathogenesis of cholangitis. Therefore, inhibition of these processes could be a fruitful therapeutic strategy. The effects of multi-kinase inhibitor 1-(4-Cl-benzyl)-3-chloro-4-(CF3-phenylamino)-1H-pyrrole-2,5-dione (MI-1) on the hepatic and systemic manifestations of acute and chronic cholangitis in rats were addressed. MI-1 (2.7 mg/kg per day) was applied to male rats that experienced α-naphthylisothiocyanate-induced acute (3 days) or chronic (28 days) cholangitis. Liver autopsy samples, blood serum markers, and leukograms were studied. MI-1 localization in liver cells and its impact on viability of HepG2 (human hepatoma), HL60 (human leukemia), and NIH3T3 (normal murine fibroblasts) cell lines and lymphocytes of human peripheral blood (MTT, DNA fragmentation, DNA comet assays, Propidium Iodide staining) were assessed. Under both acute and chronic cholangitis, MI-1 substantially reduced liver injury, fibrosis, and inflammatory scores (by 46-86%) and normalized blood serum markers and leukograms. Moreover, these effects were preserved after a 28-day recovery period (without any treatment). MI-1 inhibited the HL60, HepG2 cells, and human lymphocytes viability (IC₅₀ 0.6, 9.5 and 8.3 µg/ml, respectively), while NIH3T3 cells were resistant to that. Additionally, HepG2 cells and lymphocytes being incubated with MI-1 demonstrated insignificant pro-apoptotic and pro-necrotic changes and DNA single-strand breaks, suggesting that MI-1 effects in liver might be partly caused by its cytotoxic action towards liver cells and lymphocytes. In conclusion, MI-1 attenuated the systemic inflammation and signs of acute and chronic cholangitis partly through cytotoxicity towards cells of hepatic and leukocytic origin.

Design, synthesis, and biological evaluation of imidazopyridine-linked thiazolidinone as potential anticancer agents

In this study, two series of imidazopyridine-linked thiazolidinone rings (5a-h and 6a-h) constituting 16 new compounds were synthesized and tested for their antiproliferative activity against a panel of three human cancer cell lines, that is, MCF-7 (human breast cancer), A549 (human lung cancer), and DU145 (human prostate cancer). Three compounds, 5h, 6f, and 6h, exhibited remarkable results against all three cell lines, but compound 6h was found to be the most active one against the breast cancer cell line. Among all the synthesized compounds, 6h displayed the highest antioxidant results. Furthermore, the potent compounds 5h, 6f, and 6h showed no signs of toxicity at doses ranging from 50 to 500 mg/kg of animal body weight. The biochemical parameters (SGOT and SGPT) of compound 6h nearly matched the control in hepatotoxicity studies. The molecular docking and MM-GBSADG binding studies are in agreement with the in vitro anticancer and antioxidant activity results. The most promising compound 6h was found to have the highest docking score and binding energy, and its absorption, distribution, metabolism, and excretion (ADME) parameters are in the acceptable range. Thus, it can be concluded that 6h, an imidazopyridine derivative endowed with a thiazolidinone ring system, has the potential to be developed as an anticancer agent.

Ponatinib Inhibits Proliferation and Induces Apoptosis of Liver Cancer Cells, but Its Efficacy Is Compromised by Its Activation on PDK1/Akt/mTOR Signaling

Ponatinib is a multi-target protein tyrosine kinase inhibitor, and its effects on hepatocellular carcinoma cells have not been previously explored. In the present study, we investigated its effects on hepatocellular carcinoma cell growth and the underlying mechanisms. Toward SK-Hep-1 and SNU-423 cells, ponatinib induces apoptosis by upregulation of cleaved caspase-3 and -7 and promotes cell cycle arrest in the G1 phase by inhibiting CDK4/6/CyclinD1 complex and phosphorylation of retinoblastoma protein. It inhibits the growth-stimulating mitogen-activated protein (MAP) kinase pathway, the phosphorylation of Src on both negative and positive regulation sites, and Jak2 and Stat3 phosphorylation. Surprisingly, it also activates the PDK1, the protein kinase B (Akt), and the mechanistic target of rapamycin (mTOR) signaling pathway. Blocking mTOR signaling strongly sensitizes cells to inhibition by ponatinib and makes ponatinib a much more potent inhibitor of hepatocellular carcinoma cell proliferation. These findings demonstrate that ponatinib exerts both positive and negative effects on hepatocellular cell proliferation, and eliminating its growth-stimulating effects by drug combination or potentially by chemical medication can significantly improve its efficacy as an anti-cancer drug.

Exploratory Investigation of Target Pazopanib Concentration Range for Patients With Renal Cell Carcinoma

BACKGROUND

Severe adverse events frequently occur in patients treated with pazopanib, necessitating dose reduction and discontinuation. However, information on the exposure-toxicity relationship is limited.

PATIENTS AND METHODS

For this retrospective and observational clinical study, we examined 27 patients with renal cell carcinoma treated with pazopanib and enrolled between October 2014 and March 2018. The primary goal was to evaluate the association between trough pazopanib concentration and occurrence of grade ≥ 3 toxicities, and secondarily, to estimate the association between trough pazopanib concentration and objective response rate.

RESULTS

Mean trough pazopanib concentration was significantly higher in the grade ≥ 3 toxicity group (n = 9) than in the grade ≤ 2 toxicity group (n = 18). Based on the receiver operating characteristic curve, the threshold value of trough pazopanib concentration for predicting grade ≥ 3 toxicities was 50.3 μg/mL (area under the curve, 0.85; 95% confidence interval, 0.70-0.99; P < .05). In the pazopanib < 20.5 μg/mL group (n = 3), no patient experienced an objective response. Objective response rates between patients with 20.5 to 50.3 μg/mL pazopanib (n = 11) and patients with ≥ 50.3 μg/mL (n = 13) were similar (45.5% vs. 46.2%).

CONCLUSION

From results of this study, the target trough pazopanib concentration range may be 20.5 to 50.3 μg/mL for patients with renal cell carcinoma.

Role of Cytochrome P450 Enzymes in the Metabolic Activation of Tyrosine Kinase Inhibitors

Tyrosine kinase inhibitors are a rapidly expanding class of molecular targeted therapies for the treatment of various types of cancer and other diseases. An increasing number of clinically important small molecule tyrosine kinase inhibitors have been shown to undergo cytochrome P450-mediated bioactivation to form chemically reactive, potentially toxic products. Metabolic activation of tyrosine kinase inhibitors is proposed to contribute to the development of serious adverse reactions, including idiosyncratic hepatotoxicity. This article will review recent findings and ongoing studies to elucidate the link between drug metabolism and tyrosine kinase inhibitor-associated hepatotoxicity.

The use of SAMe in chemotherapy-induced liver injury

Drug-induced liver injury (DILI) remains the most common cause of acute liver failure in the Western world. Chemotherapy is one of the major class of drugs most frequently associated with idiosyncratic DILI. For this reason, patients who receive chemotherapy require careful assessment of liver function prior to treatment to determine which drugs may not be appropriate and which drug doses should be modified. S-adenosylmethionine (SAMe) is an endogenous agent derived from methionine. Its supplementation is effective in the treatment of liver disease, in particular intrahepatic cholestasis (IHC). The target of this review is to analyze the mechanisms of hepatotoxicity of the principal anticancer agents and the role of SAMe in the prevention of this complication.

Pharmacokinetics and disposition of anlotinib, an oral tyrosine kinase inhibitor, in experimental animal species

Anlotinib is a new oral tyrosine kinase inhibitor; this study was designed to characterize its pharmacokinetics and disposition. Anlotinib was evaluated in rats, tumor-bearing mice, and dogs and also assessed in vitro to characterize its pharmacokinetics and disposition and drug interaction potential. Samples were analyzed by liquid chromatography/mass spectrometry. Anlotinib, having good membrane permeability, was rapidly absorbed with oral bioavailability of 28%-58% in rats and 41%-77% in dogs. Terminal half-life of anlotinib in dogs (22.8±11.0 h) was longer than that in rats (5.1±1.6 h). This difference appeared to be mainly associated with an interspecies difference in total plasma clearance (rats, 5.35±1.31 L·h^-1·kg^-1; dogs, 0.40±0.06 L·h^-1/kg^-1). Cytochrome P450-mediated metabolism was probably the major elimination pathway. Human CYP3A had the greatest metabolic capability with other human P450s playing minor roles. Anlotinib exhibited large apparent volumes of distribution in rats (27.6±3.1 L/kg) and dogs (6.6±2.5 L/kg) and was highly bound in rat (97%), dog (96%), and human plasma (93%). In human plasma, anlotinib was predominantly bound to albumin and lipoproteins, rather than to α₁-acid glycoprotein or γ-globulins. Concentrations of anlotinib in various tissue homogenates of rat and in those of tumor-bearing mouse were significantly higher than the associated plasma concentrations. Anlotinib exhibited limited in vitro potency to inhibit many human P450s, UDP-glucuronosyltransferases, and transporters, except for CYP3A4 and CYP2C9 (in vitro half maximum inhibitory concentrations, <1 μmol/L). Based on early reported human pharmacokinetics, drug interaction indices were 0.16 for CYP3A4 and 0.02 for CYP2C9, suggesting that anlotinib had a low propensity to precipitate drug interactions on these enzymes. Anlotinib exhibits many pharmacokinetic characteristics similar to other tyrosine kinase inhibitors, except for terminal half-life, interactions with drug metabolizing enzymes and transporters, and plasma protein binding.

Supramolecular alleviation of cardiotoxicity of a small-molecule kinase inhibitor

Small-molecule kinase inhibitors (SMKIs) have been widely used in the treatment of a variety of cancers due to their clinically demonstrated efficacy. However, the use of some SMKIs, such as sorafenib (SO), has been plagued by their cardiotoxicity that has been frequently observed in treated patients. Herein we report that the encapsulation of SO by a synthetic receptor cucurbit[7]uril (CB[7]) alleviated the inherent cardiotoxicity of SO, as demonstrated in an in vivo zebrafish model. Moreover, the anti-cancer activity of SO was well preserved, upon its encapsulation by CB[7], as demonstrated by both in vitro and in vivo cancer/angiogenesis models. This discovery may provide new insights into a novel supramolecular formulation of SMKIs for the management of their side-effects.

Synthesis of stable benzimidazole derivatives bearing pyrazole as anticancer and EGFR receptor inhibitors

A new series of benzimidazole linked pyrazole derivatives were synthesized by cyclocondensation reaction through one-pot multicomponent reaction in absolute ethanol. All the synthesized compounds were tested for their in vitro anticancer activities on five human cancer cell lines including MCF-7, HaCaT, MDA-MB231, A549 and HepG2. EGFR receptor inhibitory activities were carried out for all the compounds. Majority of the compounds showed potent antiproliferative activity against the tested cancer cell lines. Compound 5a showed the most effective activity against the lungs cancer cell lines (IC₅₀ = 2.2 µM) and EGFR binding (IC₅₀ = 0.97 µM) affinity as compared to other members of the series. Compound 5a inhibited growth of A549 cancer cells by inducing a strong G₂/M phase arrest. In addition, same compound inhibited growth of A549 cancer cells by inducing apoptosis. In molecular docking studies compound 5a was bound to the active pocket of the EGFR (PDB 1M17) with five key hydrogen bonds and two π-π interaction with binding energies ΔG = -34.581 Kcal/mol.

[Hepatotoxicity of tyrosine kinase inhibitors: Mechanisms involved and practical implications]

Tyrosine kinase inhibitors (TKIs) are used for the targeted treatment of solid cancers. TKIs produce a variable incidence of liver adverse events (5-25%) which can progress to severe liver injury in a minority of patients if treatment is maintained despite ongoing injury. This risk requires careful patient management to maintain treatment benefit without harm. This review highlights the various mechanisms of idiosyncratic hepatotoxicity, the formation of reactive metabolites and how this leads to toxicity. These critical events depend of the drug-specific characteristics of each TKI and the patient risk factors, especially genetic characterization. With improved understanding of the mechanisms leading to hepatotoxicity, several strategies have been adopted to prevent or treat this side effect. Recommendations on liver function liver test monitoring have been proposed according to each TKI.

Mechanisms of mitochondrial toxicity of the kinase inhibitors ponatinib, regorafenib and sorafenib in human hepatic HepG2 cells

Previous studies have shown that certain kinase inhibitors are mitochondrial toxicants. In the current investigation, we determined the mechanisms of mitochondrial impairment by the kinase inhibitors ponatinib, regorafenib, and sorafenib in more detail. In HepG2 cells cultured in galactose and exposed for 24 h, all three kinase inhibitors investigated depleted the cellular ATP pools at lower concentrations than cytotoxicity occurred, compatible with mitochondrial toxicity. The kinase inhibitors impaired the activity of different complexes of the respiratory chain in HepG2 cells exposed to the toxicants for 24 h and in isolated mouse liver mitochondria exposed acutely. As a consequence, they increased mitochondrial production of ROS in HepG2 cells in a time- and concentration-dependent fashion and decreased the mitochondrial membrane potential concentration-dependently. In HepG2 cells exposed for 24 h, they induced mitochondrial fragmentation, lysosome content and mitophagy as well as mitochondrial release of cytochrome c, leading to apoptosis and/or necrosis. In conclusion, the kinase inhibitors ponatinib, regorafenib, and sorafenib impaired the function of the respiratory chain, which was associated with increased ROS production and a drop in the mitochondrial membrane potential. Despite activation of defense measures such as mitochondrial fission and mitophagy, some cells were liquidated concentration-dependently by apoptosis or necrosis. Mitochondrial dysfunction may represent a toxicological mechanism of hepatotoxicity associated with certain kinase inhibitors.

Drug rechallenge following drug-induced liver injury

Drug-induced hepatocellular injury is identified internationally by alanine aminotransferase (ALT) levels equal to or exceeding 5× the upper limit of normal (ULN) appearing within 3 months of drug initiation, after alternative causes are excluded. Upon withdrawing the suspect drug, ALT generally decrease by 50% or more. With drug readministration, a positive rechallenge has recently been defined by an ALT level of 3-5× ULN or greater. Nearly 50 drugs are associated with positive rechallenge after drug-induced liver injury (DILI): antimicrobials; and central nervous system, cardiovascular and oncology therapeutics. Drugs associated with high rates of positive rechallenge exhibit multiple risk factors: daily dose >50 mg, an increased incidence of ALT elevations in clinical trials, immunoallergic clinical injury, and mitochondrial impairment in vitro. These drug factors interact with personal genetic, immune, and metabolic factors to influence positive rechallenge rates and outcomes. Drug rechallenge following drug-induced liver injury is associated with up to 13% mortality in prospective series of all prescribed drugs. In recent oncology trials, standardized systems have enabled safer drug rechallenge with weekly liver chemistry monitoring during the high-risk period and exclusion of patients with hypersensitivity. However, high positive rechallenge rates with other innovative therapeutics suggest that caution should be taken with rechallenge of high-risk drugs.

CONCLUSION

For critical medicines, drug rechallenge may be appropriate when 1) no safer alternatives are available, 2) the objective benefit exceeds the risk, and 3) patients are fully informed and consent, can adhere to follow-up, and alert providers to hepatitis symptoms. To better understand rechallenge outcomes and identify key risk factors for positive rechallenge, additional data are needed from controlled clinical trials, prospective registries, and large health care databases. (Hepatology 2017;66:646-654).

Hepatocellular Toxicity Associated with Tyrosine Kinase Inhibitors: Mitochondrial Damage and Inhibition of Glycolysis

Tyrosine kinase inhibitors (TKIs) are anticancer drugs with a lesser toxicity than classical chemotherapeutic agents but still with a narrow therapeutic window. While hepatotoxicity is known for most TKIs, underlying mechanisms remain mostly unclear. We therefore aimed at investigating mechanisms of hepatotoxicity for imatinib, sunitinib, lapatinib and erlotinib in vitro. We treated HepG2 cells, HepaRG cells and mouse liver mitochondria with TKIs (concentrations 1–100 μM) for different periods of time and assessed toxicity. In HepG2 cells maintained with glucose (favoring glycolysis), all TKIs showed a time- and concentration-dependent cytotoxicity and, except erlotinib, a drop in intracellular ATP. In the presence of galactose (favoring mitochondrial metabolism), imatinib, sunitinib and erlotinib showed a similar toxicity profile as for glucose whereas lapatinib was less toxic. For imatinib, lapatinib and sunitinib, cytotoxicity increased in HepaRG cells induced with rifampicin, suggesting formation of toxic metabolites. In contrast, erlotinib was more toxic in HepaRG cells under basal than CYP-induced conditions. Imatinib, sunitinib and lapatinib reduced the mitochondrial membrane potential in HepG2 cells and in mouse liver mitochondria. In HepG2 cells, these compounds increased reactive oxygen species production, impaired glycolysis, and induced apoptosis. In addition, imatinib and sunitinib impaired oxygen consumption and activities of complex I and III (only imatinib), and reduced the cellular GSH pool. In conclusion, imatinib and sunitinib are mitochondrial toxicants after acute and long-term exposure and inhibit glycolysis. Lapatinib affected mitochondria only weakly and inhibited glycolysis, whereas the cytotoxicity of erlotinib could not be explained by a mitochondrial mechanism.

Management of adverse events during treatment of gastrointestinal cancers with epidermal growth factor inhibitors

The epidermal growth factor receptor (EGFR) is involved in development and progression of some gastrointestinal cancers, and is targeted by monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs) used to treat these conditions. Targeted agents are generally better tolerated than conventional chemotherapy, but have characteristic toxicities that can affect adherence, dosing, and outcomes. Skin conditions are the most common toxicities associated with EGFR inhibitors, particularly papulopustular rash. Other common toxicities include mucosal toxicity, electrolyte imbalances (notably hypomagnesaemia), and diarrhoea, while the chimaeric mAb cetuximab is also associated with increased risk of infusion reactions. With appropriate prophylaxis, the incidence and severity of these events can be reduced, while management strategies tailored to the patient and the degree of toxicity can help to ensure continuation of anti-cancer therapy. Here, we review the main toxicities associated with EGFR-inhibiting mAbs and TKIs in patients with gastrointestinal cancers, and provide recommendations for prophylaxis and treatment.

Ibrutinib-induced severe liver injury

Ibrutinib, an inhibitor of the Bruton's tyrosine kinase of the B‐cell receptor pathway, is an effective therapeutic agent for B‐cell lymphomas. As these drugs are novel, long‐term or rare adverse events are not yet known. We report the first case of ibrutinib‐induced severe liver injury in a patient with relapsed/refractory CLL.

Tyrosine kinase inhibitors: friends or foe in treatment of hepatic fibrosis?

Aberrant activity of tyrosine kinases has been proved to be associated with multiple diseases including fibrotic diseases. Tyrosine kinases inhibitors (TKIs) might be a novel approach to transform the anti-fibrotic treatment. However, both beneficial and adverse effects are observed by researchers when using these TKIs in either preclinical animal models or patients with hepatic fibrosis. Since hepatotoxicity of TKIs is the leading cause for drug withdrawals thus limits its application in anti-fibrosis, not only efficacy but also safety of TKIs should be paid great concerns. It has been observed in a few studies that TKIs could induce relatively high rate of hepatic biochemical markers elevations and even result in liver failure. Fortunately, several strategies have been adopt to handle with the hepatotoxicity. Accumulating evidences suggest that hepatic stellate cells (HSC) play a pivotal role in hepatic fibrogenesis, so it might be a good option to develop selective TKIs specifically targeting HSCs. The present review will briefly summarize the anti-fibrotic mechanism of TKIs, adverse effects of TKIs as well as the novel developed selective delivery of TKIs.

Cytochrome P450 3A4 and CYP3A5-Catalyzed Bioactivation of Lapatinib

Metabolic activation of the dual-tyrosine kinase inhibitor lapatinib by cytochromes CYP3A4 and CYP3A5 has been implicated in lapatinib-induced idiosyncratic hepatotoxicity; however, the relative enzyme contributions have not been established. The objective of this study was to examine the roles of CYP3A4 and CYP3A5 in lapatinib bioactivation leading to a reactive, potentially toxic quinoneimine. Reaction phenotyping experiments were performed using individual human recombinant P450 enzymes and P450-selective chemical inhibitors. Lapatinib metabolites and quinoneimine-glutathione (GSH) adducts were analyzed using liquid chromatography-tandem mass spectrometry. A screen of cDNA-expressed P450s confirmed that CYP3A4 and CYP3A5 are the primary enzymes responsible for quinoneimine-GSH adduct formation using lapatinib or O-dealkylated lapatinib as the substrate. The mean kinetic parameters (Km and kcat) of lapatinib O-dealkylation revealed that CYP3A4 was 5.2-fold more efficient than CYP3A5 at lapatinib O-dealkylation (CYP3A4 kcat/Km = 6.8 μM(-1) min(-1) versus CYP3A5 kcat/Km = 1.3 μM(-1) min(-1)). Kinetic analysis of GSH adduct formation indicated that CYP3A4 was also 4-fold more efficient at quinoneimine-GSH adduct formation as measured by kcat (maximum relative GSH adduct levels)/Km (CYP3A4 = 0.0082 vs. CYP3A5 = 0.0021). In human liver microsomal (HLM) incubations, CYP3A4-selective inhibitors SR-9186 and CYP3cide reduced formation of GSH adducts by 78% and 72%, respectively, compared with >90% inhibition by the pan-CYP3A inhibitor ketoconazole. The 16%-22% difference between CYP3A- and CYP3A4-selective inhibition indicates the involvement of remaining CYP3A5 activity in generating reactive metabolites from lapatinib in pooled HLMs. Collectively, these findings support the conclusion that both CYP3A4 and CYP3A5 are quantitatively important contributors to lapatinib bioactivation.

Drug-induced hepatotoxicity in cancer patients - implication for treatment

INTRODUCTION

All anticancer drugs can cause idiosyncratic liver injury. Therefore, hepatoprotective agents assume particular importance to preserve liver function. Hepatic injury represents 10% of cases of acute hepatitis in adults; drug-related damage is still misjudged because of relative clinical underestimation and difficult differential diagnosis. Chemotherapeutic agents can produce liver toxicity through different pathways, resulting in different categories of liver injuries, but these drugs are not homogeneously hepatotoxic. Frequently, anticancer-induced hepatotoxicity is idiosyncratic and influenced by multiple factors.

AREAS COVERED

The aim of this paper is to perform a review of the literature regarding anticancer-induced liver toxicity. We described hepatotoxicity mechanisms of principal anticancer agents and respective dose reductions. Furthermore, we reviewed studies on hepatoprotectors and their optimal use. Tiopronin, magnesium isoglycyrrhizinate and S-Adenosylmethionine (AdoMet) demonstrated, in some small studies, a potential hepatoprotective activity.

EXPERT OPINION

Actually, in the literature only small experiences are reported. Even though hepatoprotective agents seem to be useful in the oncologic setting, the lack of well-designed prospective Phase III randomized controlled trials is a major limit in the introduction of hepatoprotectors in cancer patients and these kind of studies are warranted to support their use and to give further recommendations for the clinical practice.

Hepatotoxicity of targeted therapy for cancer

INTRODUCTION

Understanding the mechanism of DILI with MTA, and how to avoid and manage these toxicities is essential for minimising inferior cancer treatment outcomes. An organised and comprehensive overview of MTA-associated hepatotoxicity is lacking; this review aims to fill the gap.

AREAS COVERED

A literature review was performed based on published case reports and relevant studies or articles pertaining to the topics on PubMed. Food and Drug Administration drug information documents and search on the US National Library of Medicine LiverTox database was performed for all relevant MTA.

EXPERT OPINION

MTA-associated hepatotoxicity is common but rarely fatal. The pattern of hepatotoxicity is predominantly idiosyncratic. Pharmacogenomics show potential in predicting patients at risk of poorly metabolising or developing immunoallergic responses to MTA, but prospective data is scant. Preventing reactivation of viral hepatitis using anti-viral drugs, and avoidance of drug combinations at high risk of negative interactions are the most readily preventable measures for DILI.

Germline oncopharmacogenetics, a promising field in cancer therapy

Pharmacogenetics (PGx) is the study of the relationship between inter-individual genetic variation and drug responses. Germline variants of genes involved in drug metabolism, drug transport, and drug targets can affect individual response to medications. Cancer therapies are characterized by an intrinsically high toxicity; therefore, the application of pharmacogenetics to cancer patients is a particularly promising method for avoiding the use of inefficacious drugs and preventing the associated adverse effects. However, despite continuing efforts in this field, very few labels include information about germline genetic variants associated with drug responses. DPYD, TPMT, UGT1A1, G6PD, CYP2D6, and HLA are the sole loci for which the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) report specific information. This review highlights the germline PGx variants that have been approved to date for anticancer treatments, and also provides some insights about other germline variants with potential clinical applications. The continuous and rapid evolution of next-generation sequencing applications, together with the development of computational methods, should help to refine the implementation of personalized medicine. One day, clinicians may be able to prescribe the best treatment and the correct drug dosage based on each patient's genotype. This approach would improve treatment efficacy, reduce toxicity, and predict non-responders, thereby decreasing chemotherapy-associated morbidity and improving health benefits.

Formation of reactive metabolites and management of tyrosine kinase inhibitor-induced hepatotoxicity: a literature review

INTRODUCTION

Existing clinical evidence indicates that many tyrosine kinase inhibitors (TKIs) are associated with idiosyncratic hepatotoxicity. TKIs possess risk factors for developing drug-induced liver injury such as their high daily dose, being substrates of P450 enzyme and being involved in significant hepatic metabolism. Several successful strategies to overcome TKI-induced hepatotoxicity include: switching to an alternative TKI with a similar mechanism of action, using an alternative dose and introduction of corticosteroids for treatment and prevention of hepatotoxicity.

AREAS COVERED

This review highlights the formation of reactive metabolites and how this leads to toxicity, as well as the current clinical management of TKI-induced hepatotoxicity.

EXPERT OPINION

Numerous events need to occur in an individual patient before converging into an idiosyncratic hepatotoxicity episode. Of these, the formation of a reactive intermediate through metabolism appears to be the prerequisite. This critical event involves an intricate chemico-biological interaction where, on one hand, drug-specific characteristics create the propensity for occurrence and, on the other hand, patient risk factors determine the individuality of response. With improved understanding of the mechanisms leading to adverse events, several strategies are being adopted to prevent and treat TKI-induced hepatotoxicity. However, further evidence is required before they can be recommended to larger populations.