Hepatobiliary Toxicity Research Articles

Toxicogenomics Applied to Cultures of Human Hepatocytes Enabled an Identification of Novel Petasites hybridus Extracts for the Treatment of Migraine with Improved Hepatobiliary Safety

Butterbur extracts (Petasites hybridus) are recommended for the prevention of migraine, but pharmacovigilance reports may be suggestive of rare hepatobiliary toxicity. To evaluate its hepatotoxic potential, a series of in vivo and in vitro studies were carried out. Essentially, there were no signs of hepatocellular toxicity at estimated therapeutic C(max) levels of 60 ng/ml. Nonetheless, in a 28-day toxicity study at approximately 200-fold of therapeutic doses, induced liver transaminases and bilirubin elevations were observed. In a subsequent 6-month chronic toxicity study, the initial hepatobiliary effects were reproduced, but at the end of the study, liver function recovered and returned to normal as evidenced by clinical chemistry measurements. To identify possible mechanisms of hepatotoxicity, we investigated liver function in vitro at > 170-fold of therapeutic C(max) levels, including cytotoxicity (lactate dehydrogenase, MTT, and ATP), transaminase activities (alanine aminotransferase and aspartate aminotransferase), albumin synthesis, urea and testosterone metabolism to assay for cytochrome P450 monooxygenase activity. Only with extracts rich in petasin (37% petasin) and at high and well above therapeutic doses, liver toxicity was observed. A toxicogenomic approach applied to hepatocyte cultures enabled hypothesis generation and was highly suggestive for extracts high in petasin content to impair bile acid transport and lipid and protein metabolism. Importantly, neither chronic rat in vivo nor rat in vitro studies predicted reliably hepatotoxicity, therefore reemphasizing the utility of human-based in vitro investigations for the development of safe medicinal products. Finally, toxicogenomics enabled the characterization of a novel butterbur extract with no signals for hepatotoxicity.

Rescue chemotherapy using multidrug chronomodulated hepatic arterial infusion for patients with heavily pretreated metastatic colorectal cancer

: Hepatic arterial infusion (HAI) chemotherapy delivers a high concentration of drugs both to liver metastases and to healthy liver with specific, limiting, hepatobiliary toxicities. Relevant detoxification and cellular proliferation pathways are controlled by the molecular circadian clock in normal liver but not in advanced tumors. In this article, the authors report their experience with chronomodulated HAI chemotherapy as rescue therapy in heavily pretreated patients who had metastatic colorectal cancer. : Data from all consecutive patients with colorectal cancer liver metastases who received HAI with chronomodulated, multidrug chemotherapy regimens in the authors' center after failure on standard chemotherapy were reviewed for efficacy and safety. : Twenty-nine patients were treated, including 76% with liver metastasis only and 24% with liver and lung metastases. Seventy-five percent of patients had received > or =3 chemotherapy lines, including intravenous, chronomodulated chemotherapy in 59% of patients. Patients received a median of 4 HAI courses (range, 1-9 courses). The most frequent grade (according to National Cancer Institute of Canada Common Toxicity Criteria [version 3]) 3 and 4 nonhematologic toxicities were vomiting, diarrhea, abdominal pain, and fatigue. No severe hematologic or hepatic toxicities and no chemical cholangitis were reported. An objective tumor response was observed in 10 patients (34.5%), including 4 patients who subsequently underwent R0 or R1 hepatic resection. The median progression-free survival and overall survival were 4.5 months (95% confidence limits, 2.4-6.5 months) and 18 months (95% confidence limits, 5.8-30.2 months), respectively. : HAI chronomodulated chemotherapy had well tolerated activity in selected, heavily pretreated patients, and the authors believe it deserves to be assessed prospectively in clinical trials among patients who have less advanced disease. Cancer 2009. (c) 2009 American Cancer Society.

Identification of structure-activity relationships for adverse effects of pharmaceuticals in humans: Part B. Use of (Q)SAR systems for early detection of drug-induced hepatobiliary and urinary tract toxicities

This report describes the development of quantitative structure-activity relationship (QSAR) models for predicting rare drug-induced liver and urinary tract injury in humans based upon a database of post-marketing adverse effects (AEs) linked to ∼1600 chemical structures. The models are based upon estimated population exposure using AE proportional reporting ratios. Models were constructed for 5 types of liver injury (liver enzyme disorders, cytotoxic injury, cholestasis and jaundice, bile duct disorders, gall bladder disorders) and 6 types of urinary tract injury (acute renal disorders, nephropathies, bladder disorders, kidney function tests, blood in urine, urolithiases). Identical training data sets were configured for 4 QSAR programs (MC4PC, MDL-QSAR, BioEpisteme, and Predictive Data Miner). Model performance was optimized and was shown to be affected by the AE scoring method and the ratio of the number of active to inactive drugs. The best QSAR models exhibited an overall average 92.4% coverage, 86.5% specificity and 39.3% sensitivity. The 4 QSAR programs were demonstrated to be complementary and enhanced performance was obtained by combining predictions from 2 programs (average 78.4% specificity, 56.2% sensitivity). Consensus predictions resulted in better performance as judged by both internal and external validation experiments.

Identification of structure–activity relationships for adverse effects of pharmaceuticals in humans: Part C: Use of QSAR and an expert system for the estimation of the mechanism of action of drug-induced hepatobiliary and urinary tract toxicities

This report describes an in silico methodology to predict off-target pharmacologic activities and plausible mechanisms of action (MOAs) associated with serious and unexpected hepatobiliary and urinary tract adverse effects in human patients. The investigation used a database of 8,316,673 adverse event (AE) reports observed after drugs had been marketed and AEs noted in the published literature that were linked to 2124 chemical structures and 1851 approved clinical indications. The Integrity ™ database of drug patent and literature studies was used to find pharmacologic targets and proposed clinical indications. BioEpisteme ™ QSAR software was used to predict possible molecular targets of drug molecules and Derek ™ for Windows expert system software to predict chemical structural alerts and plausible MOAs for the AEs. AEs were clustered into five types of liver injury: liver enzyme disorders, cytotoxic injury, cholestasis and jaundice, bile duct disorders, and gall bladder disorders, and six types of urinary tract injury: acute renal disorders, nephropathies, bladder disorders, kidney function tests, blood in urine, and urolithiasis. Results showed that drug-related AEs were highly correlated with: (1) known drug class warnings, (2) predicted off-target activities of the drugs, and (3) a specific subset of clinical indications for which the drug may or may not have been prescribed.

Identification of structure–activity relationships for adverse effects of pharmaceuticals in humans. Part A: Use of FDA post-market reports to create a database of hepatobiliary and urinary tract toxicities

The Informatics and Computational Safety Analysis Staff at the US FDA’s Center for Drug Evaluation and Research has created a database of pharmaceutical adverse effects (AEs) linked to pharmaceutical chemical structures and estimated population exposures. The database is being used to develop quantitative structure–activity relationship (QSAR) models for the prediction of drug-induced liver and renal injury, as well as to identify relationships among AEs. The post-market observations contained in the database were obtained from FDA’s Spontaneous Reporting System (SRS) and the Adverse Event Reporting System (AERS) accessed through Elsevier PharmaPendium™ software. The database contains approximately 3100 unique pharmaceutical compounds and 9685 AE endpoints. To account for variations in AE reports due to different patient populations and exposures for each drug, a proportional reporting ratio (PRR) was used. The PRR was applied to all AEs to identify chemicals that could be scored as positive in the training data sets of QSAR models. Additionally, toxicologically similar AEs were grouped into clusters based upon both biological effects and statistical correlation. This clustering created a weight of evidence paradigm for the identification of compounds most likely to cause human harm based upon findings in multiple related AE endpoints.

Non invasive high resolution in vivo imaging of α-naphthylisothiocyanate (ANIT) induced hepatobiliary toxicity in STII medaka

A novel transparent stock of medaka ( Oryzias latipes; STII), homozygous recessive for all four pigments (iridophores, xanthophores, leucophores, melanophores), permits transcutaneous, high resolution (<1 μm) imaging of internal organs and tissues in living individuals. We applied this model to in vivo investigation of α -naphthylisothiocyanate (ANIT) induced hepatobiliary toxicity. Distinct phenotypic responses to ANIT involving all aspects of intrahepatic biliary passageways (IHBPs), particularly bile preductular epithelial cells (BPDECs), associated with transitional passageways between canaliculi and bile ductules, were observed. Alterations included: attenuation/dilation of bile canaliculi, bile preductular lesions, hydropic vacuolation of hepatocytes and BPDECs, mild BPDEC hypertrophy, and biliary epithelial cell (BEC) hyperplasia. Ex vivo histological, immunohistochemical, and ultrastructural studies were employed to aid in interpretation of, and verify, in vivo findings. 3D reconstructions from in vivo investigations provided quantitative morphometric and volumetric evaluation of ANIT exposed and untreated livers. The findings presented show for the first time in vivo evaluation of toxicity in the STII medaka hepatobiliary system, and, in conjunction with prior in vivo work characterizing normalcy, advance our comparative understanding of this lower vertebrate hepatobiliary system and its response to toxic insult.

Screening a novel class of anticoagulants for multi‐organ toxicity using Fischer 344 rats: involvement of clinical and anatomic pathologists in the early drug development process

Veterinary clinical and anatomic pathologists play a critical role in assessing the safety of new molecules. The process for evaluation of candidate molecules in drug discovery may vary markedly, depending on the unique characteristics of the compound class. The goal of this report is to describe the evaluation process for assessing the potential toxicity of 2 anticoagulant compounds that were representative of molecules tested in early screening studies in Fisher rats, and to use these studies as an example of the strategic approach used by veterinary pathologists in pharmaceutical safety assessment. Groups of 3 rats were given vehicle alone or one of several doses of compound A or B by oral gavage daily for 4 consecutive days. Survival; clinical signs; body and organ weight measurements; hematologic, coagulation, and clinical biochemical testing; and gross and histologic findings at necropsy were assessed. Transmission electron microscopy was used to characterize unique findings in the liver of rats treated with compound B. Both compounds caused dose-dependent prolongation of the prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin clotting time (TCT). Hepatobiliary and intestinal toxicity were identified by alterations in serum chemistry data, and by histopathologic findings. Electron microscopy and tissue inorganic phosphorus analysis revealed phospholipidosis in rats treated with compound B. Pharmacologically mediated or "on target" effects for these molecules were characterized by dose-progressive prolongation of the PT, APTT, and TCT. Nonpharmacologically mediated or "off-target" toxicity consisted of hepatoxicity and enterotoxicity. These liabilities required that scientists alter the original molecular scaffold to reach the desired therapeutic target and minimize toxicity.

An in vivo Look at Vertebrate Liver Architecture: Three‐Dimensional Reconstructions from Medaka (Oryzias latipes)

Understanding three-dimensional (3D) hepatobiliary architecture is fundamental to elucidating structure/function relationships relevant to hepatobiliary metabolism, transport, and toxicity. To date, factual information on vertebrate liver architecture in 3 dimensions has remained limited. Applying noninvasive in vivo imaging to a living small fish animal model we elucidated, and present here, the 3D architecture of this lower vertebrate liver. Our investigations show that hepatobiliary architecture in medaka is based on a polyhedral (hexagonal) structural motif, that the intrahepatic biliary system is an interconnected network of canaliculi and bile-preductules, and that parenchymal architecture in this lower vertebrate is more related to that of the mammalian liver than previously believed. The in vivo findings presented advance our comparative 3D understanding of vertebrate liver structure/function, help clarify previous discrepancies among vertebrate liver conceptual models, and pose interesting questions regarding the "functional unit" of the vertebrate liver.

Characterization of ANIT-Induced Toxicity using Precision-Cut Rat and Dog Liver Slices Cultured in a Dynamic Organ Roller System

This article describes the toxicity of alpha-naphthylisothiocyanate (ANIT), a compound known to induce dose-dependent hepatobiliary toxicity in vivo, using the slice model. Liver slices (200 microm thick) from male Sprague-Dawley rats and male beagle dogs were cultured for 7 days while exposed to a range of ANIT concentrations (1- 100 microM for rat and 4-320 microM for dog). Tissues (and medium for dog) were evaluated using a panel of clinically relevant biomarkers for liver and histological endpoints to assess viability and proliferation. ANIT increased slice levels of enzyme biomarkers corresponding to biliary markers. At high concentrations (80-100 microM for rat, 320 microM for dog) a diminution of tissue enzyme levels was observed, corresponding to severe hepatobiliary injury. By days 5 and 7, biochemical markers in the medium of dog slices indicated an elevation of hepatocellular and biliary markers. Histologically for both species, minimal hepatocellular injury was noted, but proliferation of biliary epithelial cells (BEC) was observed using 5-bromo-2-deoxyuridine (BrdU) immunostaining. In rat slices, ANIT increased the expression of inducible nitrous oxide synthase (iNOS) within 12 hrs of exposure. In summary, additional experimentation using slice culture may further demonstrate its value in screening compounds that cause hepatobiliary toxicity.

The relationship among microsomal enzyme induction, liver weight, and histological change in cynomolgus monkey toxicology studies

The purpose of this investigation was to examine the relationship among hepatic microsomal enzyme induction, liver weight, histological evidence of hepatic injury, and serum clinical chemistry markers of hepatic origin in the cynomolgus monkey. We report here the results from independent toxicology studies for 10 investigative drug candidates representing four therapeutic classes. Study conditions were selected to elicit target organ toxicity. We found that six of the 10 compounds altered cytochrome P450-associated activities in both male and female monkeys, two in females only, and one altered similar activities in males only. Frequently, significant treatment-related elevations in NADPH cytochrome c reductase and ethylmorphine N-demethylase were noted. When the results from all 10 studies were pooled, 14 cytochrome P450-associated activities were significantly increased and five were decreased in males compared to 15 significantly increased and three decreased in the females. Treatment-associated liver weight increases were noted in four studies. Except for hepatocellular hypertrophy in one study, no significant treatment-related microscopic changes in liver and no elevations of serum biomarkers commonly associated with liver toxicity were observed in any of the studies that demonstrated significant hepatic enzyme induction. Compared to parallel rat studies, one compound was an inducer only in monkeys and one was an inducer only in rats. Significant elevations of microsomal drug-metabolizing enzymes in the cynomolgus monkey liver are not accompanied by substantial hepatic changes except for hepatomegaly. These alterations in the hepatic drug-metabolizing enzyme system were benign based the absence of histopathological lesions and serum biomarkers of hepatobiliary toxicity.

In vitro detection of differential and cell-specific hepatobiliary toxicity induced by geldanamycin and 17-allylaminogeldanamycin in rats

The differential toxicity of two anticancer agents is described using the in vitro rat liver slice culture model. Liver slices from F-344 rats were cultured for 5 days in Waymouth’s-based medium with exposure to a range of geldanamycin (GEL) or 17-allylaminogeldanamycin (17-AAG) concentrations. GEL induced concentration-dependent reduction of alkaline phosphatase and of γ-glutamyl transferase levels, which are indicators of biliary epithelial cell(s) (BEC) viability, and exhibited hepatocellular toxicity at higher concentrations. Histologically, BEC cell injury was evident at the lowest GEL concentration (0.1 μM) and progressed to overt bile duct necrosis at 5 μM, a level at which hepatocellular damage was also more prominent. Slices exposed to the same concentrations were more sensitive to toxic effects of GEL than of 17-AAG. 17-AAG at the lowest concentration had more slice biomarker retention than GEL, and histological analysis revealed minimal toxic effect on BEC. With increasing concentration, BEC were progressively lost, and BEC proliferation was completely inhibited at 5 μM 17-AAG. Hepatocellular injury was evident only at high dose exposures. This is believed to be the first use of an in vitro liver tissue model to accurately predict the differential and concentration-dependent toxicities of these compounds.

In Vitro Detection of Differential and Cell-Specific Hepatobiliary Toxicity Induced by Geldanamycin and 17-Allylaminogeldanamycin Using Dog Liver Slices

Experiments on rat liver slices demonstrated the differential hepatobiliary toxic potency of two anticancer agents, geldanamycin (GEL) and 17-allylaminogeldanamycin (17-AAG), over a 5-day period. This report describes the pattern of toxicity of these agents in dog liver tissue, using the in vitro liver slice culture model. Liver slices (200 microm thick) from male beagle dogs were cultured for 5 days in chemically defined culture medium containing a range of GEL and 17-AAG concentrations (0.1-5 microM). Tissues were evaluated using a panel of clinically relevant biomarkers and histological endpoints. GEL-induced reduction of alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) slice levels, indicators of biliary epithelial cell (BEC) viability, was supported by histological findings showing an increasing loss of BEC as higher concentrations were applied. At the highest concentrations studied, GEL caused both hepatocellular necrosis and BEC loss. Biomarker pattern results in the medium concurred with those from slice biochemistry measurements and histology. 17-AAG, a less potent compound in vivo, elicited more biomarker retention at higher concentrations than did GEL. Histological analysis revealed higher BEC viability and significant retention of BEC proliferation as compared with GEL. However, at the highest concentration, the toxic insult caused a marked decrease in BEC viability and proliferation. Comparison of responses with both compounds indicated that slices exposed to the same concentrations were more sensitive to GEL than to 17-AAG. Dog liver slices can thus be used to evaluate species-, compound-, and concentration-dependent differences in toxicity.

Comparison of first-line antiretroviral therapy with regimens including nevirapine, efavirenz, or both drugs, plus stavudine and lamivudine: a randomised open-label trial, the 2NN Study

The 2NN Study was a randomised comparison of the non-nucleoside reverse-transcriptase inhibitors (NNRTI) nevirapine and efavirenz. In this multicentre, open-label, randomised trial, 1216 antiretroviral-therapy-naive patients were assigned nevirapine 400 mg once daily, nevirapine 200 mg twice daily, efavirenz 600 mg once daily, or nevirapine (400 mg) and efavirenz (800 mg) once daily, plus stavudine and lamivudine, for 48 weeks. The primary endpoint was the proportion of patients with treatment failure (less than 1 log(10) decline in plasma HIV-1 RNA in the first 12 weeks or two consecutive measurements of more than 50 copies per mL from week 24 onwards, disease progression [new Centers for Disease Control and Prevention grade C event or death], or change of allocated treatment). Analyses were by intention to treat. Treatment failure occurred in 96 (43.6%) of 220 patients assigned nevirapine once daily, 169 (43.7%) of 387 assigned nevirapine twice daily, 151 (37.8%) of 400 assigned efavirenz, and 111 (53.1%) of 209 assigned nevirapine plus efavirenz. The difference between nevirapine twice daily and efavirenz was 5.9% (95% CI -0.9 to 12.8). There were no significant differences among the study groups in the proportions with plasma HIV-1 RNA concentrations below 50 copies per mL at week 48 (p=0.193) or the increases in CD4-positive cells (p=0.800). Nevirapine plus efavirenz was associated with the highest frequency of clinical adverse events, and nevirapine once daily with significantly more hepatobiliary laboratory toxicities than efavirenz. Of 25 observed deaths, two were attributed to nevirapine. Antiretroviral therapy with nevirapine or efavirenz showed similar efficacy, so triple-drug regimens with either NNRTI are valid for first-line treatment. There are, however, differences in safety profiles. Combination of nevirapine and efavirenz did not improve efficacy but caused more adverse events.

Vascular medial hyperplasia following chronic, intermittent exposure to 4,4'-methylenedianiline.

4,4'-Methylenedianiline (DAPM) is an aromatic amine used in the synthesis of polyurethanes and epoxy resins. Acute exposure to DAPM produces hepatobiliary toxicity in humans as well as animal models. However, the toxic effects of intermittent DAPM exposure have not been explored. We treated male and female rats with 25 mg DAPM/kg or vehicle once per week for 17-22 wk. Though concentric fibrosis around bile ducts of the liver was noted, vascular medial hyperplasia was also prominent. Morphometric analysis of histologic sections revealed that in male rats, vessel wall area increased relative to lumen area in hepatic arteries by 22 wk. However, in female rats, wall areas of both hepatic and pulmonary arteries increased relative to lumen area by 17 wk. In both male and female rats, increased wall thickness was localized to the medial layer; no intimal changes were noted. In vitro treatment of vascular smooth muscle cells (VSMC) with 25-100 microM DAPM resulted in increased DNA synthesis and VSMC proliferation. To test whether the observed alterations in cell cycle control involved VSMC-mediated metabolism of DAPM to electrophilic intermediates, cells were treated with DAPM or DAPM plus 50 microM N-acetylcysteine (NAC). Coincubation with NAC afforded dramatic protection against DAPM-induced VSMC proliferation. Though DAPM had no appreciable effect on levels of reduced glutathione, oxidized glutathione, or oxidant production, DAPM increased glutathione-S-transferase activity in VSMC. These data indicate that DAPM can initiate VSMC proliferation, possibly via VSMC-mediated metabolism of DAPM to reactive intermediates.

Melphalan antitumor efficacy and hepatotoxicity: the effect of variable infusion duration in the hepatic artery.

The optimum conditions (duration and concentration) of a fixed dose, intra-arterial melphalan infusion in relation to its antitumor effect and toxicity in the liver were investigated in a rat colon tumor model (CC531) of liver metastases. We studied the difference in tumor and liver uptake, as well as antitumor effect and hepatotoxicity after 5- and 20-min hepatic arterial infusion (HAI) of a fixed melphalan dose. Melphalan content in perfusate, liver, and tumor tissue was analyzed by high-performance liquid chromatography. The antitumor effect and hepatotoxicity in rats treated either systemically or with 5- and 20-min HAI, with a fixed dose melphalan (4.4 micromol), were assessed 2 weeks after treatment. No difference in melphalan content of tumor/liver tissue or antitumor effect was observed between rats treated with 5- and 20-min HAI. Hepatotoxicity was strongly affected by perfusion duration/concentration, however. Rats treated with 5-min HAI weighed significantly less, and liver toxicity parameters were significantly increased compared with those of all other groups; eight of nine rats showed severe cholangiofibrosis. Body weights and liver toxicity parameters of the rats treated with 20-min HAI were not statistically different from the control group. In conclusion, duration of HAI with 4.4 micromol of fixed dose melphalan did not affect tumor uptake and antitumor effect, but the resulting increase in melphalan concentration had major impact on hepatobiliary toxicity. Therefore, in a clinical setting, caution should be taken when infusion duration and concentration of melphalan are changed.

Evalutaion of the Gender Differences in 4,4'-Methylenedianiline Toxicity, Distribution, and Effects on Biliary Parameters

Exposure to 4,4'-diaminodiphenylmethane (DAPM) has been linked to jaundice, toxic hepatitis, cholangitis, and cholestasis. In rodents, DAPM initially injures biliary epithelial cells, and toxicity is greater in female than male rats. Our goal was to determine if gender differences in DAPM toxicity were due to differences in biliary excretion or covalent binding of DAPM metabolites in the liver. Bile duct-cannulated female and male Sprague-Dawley rats were gavaged with vehicle or with 25 or 50 mg [14C]DAPM/kg, and bile was collected for 6 h. Serum and bile indicators of hepatobiliary toxicity were assessed, and radioactivity was measured in bile, serum, urine, and liver. At the 25 mg/kg dose, serum parameters were elevated only in female rats, while increases in serum parameters were observed in both genders at the 50 mg/kg dose. In males rats, biliary constituents altered by DAPM [inorganic phosphate (Pi

Toxicity of chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in diethylnitrosamine-initiated ovariectomized rats implanted with subcutaneous 17 beta-estradiol pellets.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent hepatocarcinogen in female but not in male rats. Several lines of evidence suggest a key role of ovarian hormones, presumably estrogen, in the mechanism of TCDD-induced hepatocarcinogenesis. The aim of this current study was to determine the toxicity of co-treatment with TCDD and 17 beta-estradiol and assess the efficacy of 90-day subcutaneous constant release 17 beta-estradiol pellets. Ovariectomized (OVX) female Sprague-Dawley rats were initiated with diethylnitrosamine (DEN) and treated with TCDD for 20 or 30 weeks in the presence and absence of 17 beta-estradiol. TCDD concentrations were equivalent in livers of TCDD-treated sham operated and OVX rats following 20 weeks of treatment. Following 30 weeks of TCDD treatment, liver TCDD concentrations were higher in OVX rats than in intact rats. TCDD concentrations in livers of TCDD-treated OVX rats receiving supplemental 17 beta-estradiol were similar to intact rats following either 20 or 30 weeks of treatment. Mean hepatic background TCDD concentrations in untreated rats were 2-fold higher in intact rats compared to OVX rats, regardless of 17-estradiol exposure following 20, but not 30 weeks of treatment. Serum indicators of hepatocellular and hepatobiliary toxicity indicated transient hepatotoxicity in TCDD-treated OVX rats receiving 17 beta-estradiol. Histopathological alterations indicated hepatotoxicity induced by exposure to TCDD following either 20 or 30 weeks of exposure. No excess hepatotoxicity was associated with 17 beta-estradiol-supplementation in TCDD-exposed OVX female Sprague-Dawley rats. Serum 17 beta-estradiol concentrations were not constant and resulted in supra-physiological levels that decreased over time, resulting in target physiological serum 17 beta-estradiol concentrations following several weeks of release. Treatment with 17 beta-estradiol resulted in uterine weights and total body weights comparable to sham-operated female rats. These data confirm the efficacy of supplemental subcutaneous 17 beta-estradiol pellets on the induction of estrogenic responses in TCDD-treated rats and indicate no increased hepatotoxicity associated with 17 beta-estradiol exposure in TCDD-treated rats.

Extensive Biliary Excretion of the Sulfasalazine Analogue, Susalimod, but Different Concentrations in the Bile Duct in Various Animal Species Correlating to Species‐Specific Hepatobiliary Toxicity

Studies on biliary concentrations of susalimod were conducted in rat, dog and monkey to clarify the interspecies differences observed in toxicology studies with respect to hepatobiliary toxicity after long-term administration of the compound. Dose-related bile duct hyperplasia appeared only in dogs at doses > or =75 mg/kg/day, while in rats and monkeys it did not appear at doses up to 1500 and 2000 mg/kg/day respectively. Biliary excretion was investigated after intraduodenal administration of susalimod in anaesthetised animals. In addition excretion routes were determined by collecting urine and faeces following a radiolabelled intravenous dose. Susalimod was extensively excreted via the bile in all animal species, > or =90%, mainly as non-conjugated parent compound. However, the local concentrations in bile varied between the species. Highest concentrations were obtained in the dog. The bile/plasma concentration ratio was 3400 in the dog, 300 in the monkey and 50 in the rat. In the dog, bile duct concentrations of susalimod about 30,000 micromol/l was obtained at plasma concentrations approximately similar to those at which hepatobiliary toxicity occurred, while in rat and monkey the levels were < or =7000 micromol/l at plasma concentrations similar to those obtained at the highest doses in the toxicology studies. From these results supported by a previous biliary excretion study in conscious dogs with chronic bile fistula receiving repeated administration of susalimod (Påhlman et al. 1999), it is likely that the hepatotoxic findings in dog are induced by the high concentrations of susalimod in the bile duct.

Alternating floxuridine and 5-fluorouracil hepatic arterial chemotherapy for colorectal liver metastases minimizes biliary toxicity

The goals of this study of a hepatic arterial infusion (HAI) regimen of alternating floxuridine and 5-fluorouracil were to evaluate the treatment-related toxic effects, the antitumor response rate, and patient survival. Fifty-seven consecutive patients were treated with implanted HAI pumps and received a regimen of alternating floxuridine (0.1 mg/kg/day continuous HAI for 7 days) followed by a weekly HAI pump bolus of 5-fluorouracil (15 mg/kg for 3 weeks). Any changes in treatment plan because of toxicity, antitumor response, and survival were recorded. Thirty-one (54.4%) patients responded to this HAI regimen; 14 (24.5% )patients had stable disease, and 12 (21.1%) progressed during treatment. Responders or patients with stable disease had a significantly (P < 0.05) improved survival rate (19 months median) compared with patients in whom disease progressed (12 months median). Two (3.5%) patients developed biliary sclerosis and 12 (21.1%) had mild transient liver function abnormalities. The liver alone or in combination with another area was the site of first progression of disease in 40 (70.2%) patients. This regimen had reversible or no hepatobiliary toxicity in more than 95% of patients. Tumor reduction or stabilization of disease was observed in 79% of the patients, who had a median survival of 19 months. Reduced toxicity and more effective chemotherapeutic regimens may increase the likelihood of survival after HAI chemotherapy for unresectable colorectal liver metastases.

A phase I evaluation of chronotropic delivery of floxuridine by hepatic arterial infusion in patients with metastatic colorectal cancer

Hepatic arterial infusion (HAI) of floxuridine is often used for metastatic colorectal cancer, though this is associated with dose-limiting hepatobiliary toxicity. A phase I trial was initiated to determine if circadian-patterned HAI floxuridine would reduce toxicity. Twenty-one patients were enrolled, and they received a continuous 14-day HAI of floxuridine, with 90-95% of the drug delivered over the same six-hour period daily. The therapy was tolerable, but there was no reduction in hepatobiliary toxicity. The response rate of 33% (1 complete and 6 partial responses) was similar to that of regimens that do not utilize circadian timing. HAI floxuridine chronotherapy for metastatic colorectal cancer cannot be recommended.