Irinotecan in the treatment of small cell lung cancer: a review of patient safety considerations

Construction and application of a high-content analysis for identifying human carboxylesterase 2 inhibitors in living cell system

Human carboxylesterase 2 (hCE2), one of the most principal drug-metabolizing enzymes, catalyzes the hydrolysis of a variety of endogenous esters, anticancer agents, and environmental toxicants. The significant roles of hCE2 in both endobiotic and xenobiotic metabolism sparked great interest in the discovery and development of efficacious and selective inhibitors. However, the safe and effective inhibitors of hCE2 are scarce, due to the lack of efficient screening and evaluation systems for complex biological systems. To offer a solution to this problem, a high-content analysis (HCA)-based cell imaging and multiparametric assay method was constructed for evaluating the inhibitory effect and safety of hCE2 inhibitors in living cell system. In this study, we first established a cell imaging-based method for identifying hCE2 inhibitors at the living cell level with hCE2 fluorescent probe NCEN. Meanwhile, two nuclear probes, Hoechst 33342 and PI, were integrated to evaluate the potential cytotoxicity of compounds simultaneously. Then, the accuracy of the HCA-based method was verified by the LC-FD-based method with a positive inhibitor BNPP, and the results showed that the HCA-based method exhibited excellent precision, robustness, and reliability. Finally, the newly established HCA-based multiparametric assay panel was successfully applied to re-evaluate a series of reported hCE2 inhibitors in living cells. In summary, the HCA-based multiparametric method could serve as an efficient tool for the accuracy measurement inhibitory effect and cytotoxicity of compounds against hCE2 in living cell system. Graphical abstract.

Modulations in the Peripheral Immune System of Glioblastoma Patient Is Connected to Therapy and Tumor Progression-A Case Report from the IMMO-GLIO-01 Trial

Immune responses are important for efficient tumor elimination, also in immune privileged organs such as the brain. Fostering antitumor immunity has therefore become an important challenge in cancer therapy. This cannot only be achieved by immunotherapies as already standard treatments such as radiotherapy and chemotherapy modify the immune system. Consequently, the understanding of how the tumor, the tumor microenvironment, and immune system are modulated by cancer therapy is required for prognosis, prediction, and therapy adaption. The prospective, explorative, and observational IMMO-GLIO-01 trial was initiated to examine the detailed immune status and its modulation of about 50 patients suffering from primary glioblastoma multiforme (GBM) or anaplastic astrocytoma during standard therapy. Prior to the study, a flow cytometry-based assay was established allowing the analysis of 34 immune cell subsets and their activation state. Here, we present the case of the first and longest accompanied patient, a 53-year-old woman suffering from GBM in the front left lobe. In context of tumor progression and therapy, we describe the modulation of the peripheral immune status over 17 months. Distinct immune modulations that were connected to therapy response or tumor progression were identified. Inter alia, a shift of CD4:CD8 ratio was observed that correlated with tumor progression. Twice we observed a unique composition of peripheral immune cells that correlated with tumor progression. Thus, following up these immune modulations in a closely-meshed manner is of high prognostic and predictive relevance for supporting personalized therapy and increasing therapy success.

Clinical Trial registration: ClinicalTrials.gov, identifier NCT02022384 (registered retrospectively on 13th of December, 2013).

The Inhibitory Effect of Ciprofloxacin on the β-Glucuronidase-mediated Deconjugation of the Irinotecan Metabolite SN-38-G

The enterohepatic recycling of a drug consists of its biliary excretion and intestinal reabsorption, which is sometimes accompanied by hepatic conjugation and intestinal deconjugation reactions. β-Glucuronidase, an intestinal bacteria-produced enzyme, can break the bond between a biliary excreted drug and glucuronic acid. Antibiotics such as ciprofloxacin can reduce the enterohepatic recycling of glucuronide-conjugated drugs. In this study, we established an in vitro system to evaluate the β-glucuronidase-mediated deconjugation of the irinotecan metabolite SN-38-G to its active SN-38 form and the effect of ciprofloxacin thereon. SN-38 formation increased in a time-dependent manner from 5 to 30 min. in the presence of β-glucuronidase. Ciprofloxacin and phenolphthalein-β-D-glucuronide (PhePG), a typical β-glucuronidase substrate, significantly decreased SN-38-G deconjugation and, hence SN-38 formation. Similarly, the antibiotics enoxacin and gatifloxacin significantly inhibited the conversion of SN-38-G to SN-38, which was not observed for levofloxacin, streptomycin, ampicillin and amoxicillin/clavulanate. Ciprofloxacin showed a dose-dependent inhibitory effect on the β-glucuronidase-mediated conversion of SN-38-G to SN-38 with a half-maximal inhibitory concentration (IC50 ) value of 83.8 μM. PhePG and ciprofloxacin afforded the inhibition in a competitive and non-competitive manner, respectively. These findings suggest that the reduction in the serum SN-38 concentration following co-administration of ciprofloxacin during irinotecan treatment is due, at least partly, to the decreased enterohepatic circulation of SN-38 through the non-competitive inhibition of intestinal β-glucuronidase-mediated SN-38-G deconjugation.

Novel sulfobutyl ether cyclodextrin gradient leads to highly active liposomal irinotecan formulation

OBJECTIVES

Liposomal delivery of irinotecan could provide protection against drug hydrolysis, deliver more active lactone form to tumours and prolong irinotecan exposure time. Nevertheless, conventional drug-loading technologies have typically resulted in undesired drug retention properties. To resolve the problem, a modified gradient loading method was developed and the resulting formulations were evaluated in a systemic manner.

METHODS

Irinotecan was loaded into liposomes using a novel sulfobutyl ether beta-cyclodextrin (sbe-CD) gradient. The effect of drug-to-lipid ratio (D/L) and polyethylene glycol (PEG) grafting density were investigated. Drug release experiments were performed in ammonium-containing medium based on the fluorescence dequenching phenomenon of irinotecan. Pharmacokinetic studies were performed in normal balb/c mice treated with different formulations. To compare the anti-tumour effect of different formulations, an RM-1 prostate cancer model was used. Acute toxicity studies were performed in healthy female c57 mice.

KEY FINDINGS

Irinotecan could be encapsulated into liposomes with >90% loading efficiency at a high drug-to-lipid mass ratio (>0.5). In-vitro release experiments revealed that sbe-CD anion was more able to retain irinotecan than sulfate. Moreover, the elevated D/L ratio elicited decreased drug release kinetics. Both trends had also been observed when the effects of anions and D/L ratio on half-life of irinotecan were assessed. Pegylated liposomal irinotecan loaded with sbe-CD/triethylammonium gradient had irinotecan half-life values ranging from 9.4 to 13.1 h, surpassing vesicles prepared by the triethylammonium sulfate method (∼4.5 h). In the RM-1 tumour model, all the liposomal irinotecan formulations were more therapeutically active than free irinotecan and the formulation with a high D/L ratio was the most efficacious. Moreover, the high D/L formulation might be less toxic than free irinotecan based on acute toxicity studies.

CONCLUSIONS

The novel sbe-CD gradient could mediate effective irinotecan loading and improve irinotecan retention, thus resulting in highly active liposomal irinotecan formulations. The improvement in drug retention might be associated with the formation of complicated aggregates inside vesicles.

Metabolic pathways of the camptothecin analog AR-67

7-tert-Butyldimethylsilyl-10-hydroxycamptothecin (AR-67; also known as DB-67) is a novel lipophilic camptothecin analog in early-phase anticancer clinical trials. In support of these studies, we evaluated the metabolism of AR-67 in vitro and identified potential metabolites in patient samples. The lactone form of AR-67 was found to be preferentially metabolized over AR-67 carboxylate in human microsomes. Subsequently, the lactone form was tested as a substrate in a panel of CYP450 and UDP-glucuronosyltransferase (UGT) enzymes known to metabolize the majority of clinically approved molecules. AR-67 was metabolized by CYP3A5, CYP3A4, CYP1A1, and CYP1A2, in order of activity. Extrahepatic UGT1A8 and UGT1A7 possessed at least 6-fold higher metabolizing activity than UGT1A1 and other UGT enzymes tested. CYP1A1 and UGT1A7 displayed Michaelis-Menten kinetics, whereas CYP3A4, CYP3A5, and UGT1A8 displayed kinetics consistent with substrate inhibition. Chromatographic analysis of representative patient plasma and urine samples demonstrated the presence of AR-67 glucuronides and oxidized products in the urine but only in very minimal amounts. We conclude that limited in vivo metabolism of AR-67 by UGT1A1 may partly explain the absence of AR-67 glucuronides in plasma and hypothesize that UGT1A8- and CYP3A-mediated biotransformation within the gastrointestinal epithelium may provide protective mechanisms against AR-67 gastrointestinal toxicity.

Dose-dependent association between UGT1A1*28 polymorphism and irinotecan-induced diarrhoea: a meta-analysis

Life-threatening diarrhoea is observed in up to 25% of cancer patients receiving irinotecan. The associations between the UGT1A1*28 polymorphism and irinotecan-induced diarrhoea remains controversial because of conflicting data in the literature. Meta-analyses were performed on published data in terms of relationships between UGT1A1*28 and severe diarrhoea. We searched databases for relevant studies that were published in English or Chinese. Two reviewers extracted data and assessed methodological quality. UGT1A1*28 related odds ratios (ORs) were pooled by use of a fixed-effects model. The studies included were stratified into subgroups representing different races and irinotecan doses, and meta-regression analyses were performed to investigate the effect of study characteristics on the association between UGT1A1*28 and diarrhoea. Twenty trials including a total of 1760 cancer patients were included. The risk of severe diarrhoea at medium and high irinotecan doses was higher among patients with a UGT1A1*28/*28 genotype than among those with a UGT1A1*1/*1 genotype (OR=3.69, 95% confidence interval [CI]=2.00-6.83; P<0.001). Considering the patients with a UGT1A1*1/*28 genotype, the risk of toxicity was also higher than among those with a wild-type genotype at medium and high doses (OR=1.92, 95% CI=1.31-2.82; P=0.001). No association was observed between UGT1A1*28 and severe diarrhoea at low doses (<125 mg/m(2)). In conclusion, patients carrying UGT1A1*28 allele(s) are at an increased risk of irinotecan-induced severe diarrhoea. This increased risk is only apparent in those who are administrated with medium or high irinotecan doses.

Association of ATP-binding cassette, sub-family C, number 2 (ABCC2) genotype with pharmacokinetics of irinotecan in Japanese patients with metastatic colorectal cancer treated with irinotecan plus infusional 5-fluorouracil/leucovorin (FOLFIRI)

ATP-binding cassette, sub-family C, number 2 (ABCC2) is involved in the biliary excretion of irinotecan and its metabolites, SN-38 and SN-38 glucuronide. Effects of the ABCC2 genotype on the pharmacokinetics (PK) of irinotecan and the metabolites were examined in Japanese patients with metastatic colorectal cancer receiving irinotecan plus infusional 5-fluorouracil/leucovorin (FOLFIRI). ABCC2 genotypes (-1549G>A, -1023G>A, -1019A>G, -24C>T, 1249G>A and 3972C>T) and haplotypes were analyzed for 67 patients with cancer. PK was also examined in a subset of 31 patients receiving FOLFIRI. Relationship between the ABCC2 genotypes or diplotypes and area under the time-concentration curve (AUC) of irinotecan and the metabolites normalized by irinotecan dose was analyzed. The lower AUC of irinotecan was seen in patients with A/A or G/A genotypes at 1249 of the ABCC2 gene than others (p=0.011, Mann-Whitney U teat). AUC of SN-38 in patients with A/A or G/A genotypes at -1023 was significantly lower than that in others (p=0.018). The haplotype I included -1023A (GAACGC) was the most frequent one with the allele frequency of 0.366. The AUC of SN-38 observed in patients with diplotypes harboring at least one haplotype I was lower than that observed in others (p=0.023). The haplotype IV consisted of 1249 (GGACAC) and was the fourth most frequent one with the allele frequency of 0.127. Patients with diplotypes carrying at least one haplotype IV showed lower AUC of irinotecan than others (p=0.011). Thus, ABCC2 genotype is one of the predictors of the variability of irinotecan PK in Japanese patients with metastatic colorectal cancer receiving FOLFIRI.

Resistance to chemotherapy in cancer: a complex and integrated cellular response

Inherent and acquired resistance pathways account for the high rate of failure in cancer chemotherapy. The mechanisms or pathways mediating resistance may be classified as pharmacokinetic (i.e. alter intratumour drug exposue) or pharmacodynamic (i.e. failure to elicit cytotoxicity). More often than not, the resistant phenotype is characterised by alterations in multiple pathways. Consequently, the pathways may act synergistically or generate a broad spectrum of resistance to anticancer drugs. There has been a great deal of systematic characterisation of drug resistance in vitro. However, translating this greater understanding into clinical efficacy has rarely been achieved. This review explores the phenomenon of drug resistance in cancer and highlights the gap between in vitro and in vivo observations. This gap presents a major obstacle in overcoming drug resistance and restoring sensitivity to chemotherapy.

Characterisation of mucosal changes in the alimentary tract following administration of irinotecan: implications for the pathobiology of mucositis

PURPOSE

The pathobiology of alimentary tract (AT) mucositis is complex and there is limited information about the events which lead to the mucosal damage that occurs during cancer treatment. Various transcription factors and proinflammatory cytokines are thought to play important roles in pathogenesis of mucositis. The aim of this study was to determine the expression of nuclear factor-kappaB (NF-kappaB), tumor necrosis factor (TNF) and interleukins-1beta (IL-1beta) and -6 (IL-6) in the AT following the administration of the chemotherapeutic agent irinotecan.

METHODS

Eighty-one female dark Agouti rats were assigned to either control or experimental groups according to a specific time point. Following administration of irinotecan, rats were monitored for the development of diarrhoea. The rats were killed at times ranging from 30 min to 72 h after administration of irinotecan. Oral mucosa, jejunum and colon were collected and standard immunohistochemical techniques were used to identify NF-kappaB, TNF, IL-1beta and IL-6 within the tissues. Sections were also stained with haematoxylin and eosin for histological examination.

RESULTS

Irinotecan caused mild to moderate diarrhoea in a proportion of the rats that received the drug. Altered histological features of all tissues from rats administered irinotecan were observed which included epithelial atrophy in the oral mucosa, reduction of villus height and crypt length in the jejunum and a reduction in crypt length in the colon. Tissue staining for NF-kappaB, TNF and IL-1beta and IL-6 peaked at between 2 and 12 h in the tissues examined.

CONCLUSIONS

This is the first study to demonstrate histological and immunohistochemical evidence of changes occurring concurrently in different sites of the AT following chemotherapy. The results of the study provide further evidence for the role of NF-kappaB and associated pro-inflammatory cytokines in the pathobiology of AT mucositis. The presence of these factors in tissues from different sites of the AT also suggests that there may be a common pathway along the entire AT causing mucositis following irinotecan administration.

The role of pro-inflammatory cytokines in cancer treatment-induced alimentary tract mucositis: pathobiology, animal models and cytotoxic drugs

Alimentary tract (AT) mucositis can be a major problem for patients undergoing cancer treatment. It has significant clinical and economic consequences and is a major factor that can compromise the provision of optimal treatment for patients. The pathobiology of AT mucositis is complex and the exact mechanisms that underlie its development still need to be fully elucidated. Current opinion considers that there is a prominent interplay between all of the compartments of the mucosa involving, at a molecular level, the activation of transcription factors, particularly nuclear factor-kappaB, and the subsequent upregulation of pro-inflammatory cytokines and inflammatory mediators. The purpose of this review is to examine the literature relating to what is currently known about the pathobiology of AT mucositis, particularly with respect to the involvement of pro-inflammatory cytokines, as well as currently used animal models and the role of specific cytotoxic chemotherapy agents in the development of AT mucositis.

Irinotecan-induced diarrhea: functional significance of the polymorphic ABCC2 transporter protein

Interindividual pharmacokinetic variability of the anticancer agent irinotecan is high. Life-threatening diarrhea is observed in up to 25% of patients receiving irinotecan and has been related with irinotecan pharmacokinetics and UGT1A1 genotype status. Here, we explore the association of ABCC2 (MRP2) polymorphisms and haplotypes with irinotecan disposition and diarrhea. A cohort of 167 Caucasian cancer patients who were previously assessed for irinotecan pharmacokinetics (90-min infusion given every 21 days), toxicity, and UGT1A1*28 genotype were genotyped for polymorphisms in ABCC2 using Pyrosequencing. Fifteen ABCC2 haplotypes were identified in the studied patients. The haplotype ABCC2*2 was associated with lower irinotecan clearance (28.3 versus 31.6 l/h; P=0.020). In patients who did not carry a UGT1A1*28 allele, a significant reduction of severe diarrhea was noted in patients with the ABCC2*2 haplotype (10 versus 44%; odds ratio, 0.15; 95% confidence interval, 0.04-0.61; P=0.005). This effect was not observed in patients with at least one UGT1A1*28 allele (32 versus 20%; odds ratio, 1.87; 95% confidence interval, 0.49-7.05; P=0.354). This study suggests that the presence of the ABCC2*2 haplotype is associated with less irinotecan-related diarrhea, maybe as a consequence of reduced hepatobiliary secretion of irinotecan. As the association was seen in patients not genetically predisposed at risk for diarrhea due to UGT1A1*28, confirmatory studies of the relationships of ABCC2 genotypes and irinotecan disposition and toxicity are warranted.