Tg.rasH2 Mouse Model for Assessing Carcinogenic Potential of Pharmaceuticals: Industry Survey of Current Practices.

The Tg.rasH2 mouse was developed as an alternative model to the traditional 2-year mouse bioassay for pharmaceutical carcinogenicity testing. This model has found extensive use in support of pharmaceutical drug development over the last few decades. It has the potential to improve quality and timeliness, reduce animal usage, and in some instances allow expedient decision-making regarding the human carcinogenicity potential of a drug candidate. Despite the increased use of the Tg.rasH2 model, there has been no systematic survey of current practices in the design, interpretation of results from the bioassay, and global health authority perspectives. Therefore, the aim of this work was to poll the pharmaceutical industry on study design practices used in the dose range finding and definitive 6-month studies and on results relative to the ongoing negotiations to revise The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use S1 Guidance. Twenty-two member companies of International Consortium for Innovation and Quality in Pharmaceutical Development DruSafe Leadership Group participated in the survey, sharing experiences from studies conducted with 55 test compounds between 2010 and 2018. The survey results provide very useful insights into study design and interpretation. Importantly, the results identified several key opportunities for reducing animal use and increasing the value of testing for potential human carcinogenicity using this model. Recommended changes to study designs that would reduce animal usage include eliminating the requirement to include positive control groups in every study, use of nontransgenic wild-type littermates in the dose range finding study, and use of microsampling to reduce or eliminate satellite groups for toxicokinetics.

A novel, integrated in vitro carcinogenicity test to identify genotoxic and non-genotoxic carcinogens using human lymphoblastoid cells.

Human exposure to carcinogens occurs via a plethora of environmental sources, with 70-90% of cancers caused by extrinsic factors. Aberrant phenotypes induced by such carcinogenic agents may provide universal biomarkers for cancer causation. Both current in vitro genotoxicity tests and the animal-testing paradigm in human cancer risk assessment fail to accurately represent and predict whether a chemical causes human carcinogenesis. The study aimed to establish whether the integrated analysis of multiple cellular endpoints related to the Hallmarks of Cancer could advance in vitro carcinogenicity assessment. Human lymphoblastoid cells (TK6, MCL-5) were treated for either 4 or 23 h with 8 known in vivo carcinogens, with doses up to 50% Relative Population Doubling (maximum 66.6 mM). The adverse effects of carcinogens on wide-ranging aspects of cellular health were quantified using several approaches; these included chromosome damage, cell signalling, cell morphology, cell-cycle dynamics and bioenergetic perturbations. Cell morphology and gene expression alterations proved particularly sensitive for environmental carcinogen identification. Composite scores for the carcinogens' adverse effects revealed that this approach could identify both DNA-reactive and non-DNA reactive carcinogens in vitro. The richer datasets generated proved that the holistic evaluation of integrated phenotypic alterations is valuable for effective in vitro risk assessment, while also supporting animal test replacement. Crucially, the study offers valuable insights into the mechanisms of human carcinogenesis resulting from exposure to chemicals that humans are likely to encounter in their environment. Such an understanding of cancer induction via environmental agents is essential for cancer prevention.

Regulatory Forum.

Revision of the International Council for Harmonization (ICH) S1 guidance for rat carcinogenicity studies to be more selective of compounds requiring a 2-year rat carcinogenicity study has been proposed following extensive evaluation of rat carcinogenicity and chronic toxicity studies by industry and drug regulatory authorities. To inform the ICH S1 expert working group in their potential revision of ICH S1, a prospective evaluation study was initiated in 2013, in which sponsors would assess the pharmacologic and toxicologic findings present in the chronic toxicity studies and predict a positive or negative carcinogenicity outcome using a weight of evidence argument (a carcinogenicity assessment document [CAD]). The Scientific and Regulatory Policy Committee was asked by the Society of Toxicology Pathology (STP) executive committee to track these changes with ICH S1 and inform the STP membership of status changes. This commentary is intended to provide a brief summary of recent changes to the CAD guidance and highlight the importance of STP membership participation in the process of CAD submissions.

Development of a screening tool to prioritize testing for the carcinogenic hazard of residual aromatic extracts and related petroleum streams.

Residual aromatic extracts (RAE) are petroleum substances with variable composition predominantly containing aromatic hydrocarbons with carbon numbers greater than C25. Because of the high boiling nature of RAEs, the aromatics present are high molecular weight, with most above the range of carcinogenic polycyclic aromatic hydrocarbons (PAHs). However, refinery distillations are imperfect; some PAHs and their heteroatom-containing analogs (collectively referred to as polycyclic aromatic content or PAC) may remain in the parent stream and be extracted into the RAE, and overall PAC content is related to the carcinogenic potential of an RAE. We describe here a real-time analytical chemistry-based tool to assess the carcinogenic hazard of RAE via the development of a functional relationship between carcinogenicity and boiling point. Samples representative of steps along the RAE manufacturing process were obtained from five refineries to evaluate relationships between mutagenicity index (MI), PAC ring content and gas chromatographic distillation (GCD) curves. As expected, a positive linear relationship between MI and PAC ring content occurred, most specifically for 3-6 ring PAC (R2=0.68). A negative correlation was found between MI and temperature at 5% vaporization by GCD (R2=0.72), indicating that samples with greater amounts of lower boiling constituents were more likely to be carcinogenic. The inverse relationship between boiling range and carcinogenicity was further demonstrated by fractionation of select RAE samples (MI=0.50+0.07; PAC=1.70+0.51wt%; n=5) into low and high boiling fractions, where lower boiling fractions were both more carcinogenic than the higher boiling fractions (MI=2.36±0.55 and 0.17±0.11, respectively) and enriched in 3-6 ring PACs (5.20+0.70wt% and 0.97+0.35wt%, respectively). The criteria defining carcinogenicity was established as 479°C for the 5% vaporization points by GCD, with an approximate 95% probability of a future sample having an MI below the recommended limit of 0.4 for RAEs. Overall, these results provide a cost-efficient and real-time tool by which the carcinogenic potential of RAEs can be assessed at the refinery level, ultimately providing a means to readily monitor and minimize the carcinogenic potential of RAEs.

Bhas 42 cell transformation activity of cigarette smoke condensate is modulated by selenium and arsenic.

Cigarette smoking remains a major health risk worldwide. Development of newer tobacco products requires the use of quantitative toxicological assays. Recently, v-Ha-ras transfected BALB/c3T3 (Bhas 42) cell transformation assay was established that simulates the two-stage animal tumorigenesis model and measures tumor initiating and promoting activities of chemicals. The present study was performed to assess the feasibility of using this Bhas 42 cell transformation assay to determine the initiation and promotion activities of cigarette smoke condensate (CSC) and its water soluble fraction. Further, the modulating effects of selenium and arsenic on cigarette smoke-induced cell transformation were investigated. Dimethyl sulfoxide (DMSO) and water extracts of CSC (CSC-D and CSC-W, respectively) were tested at concentrations of 2.5-40 µg mL(-1) in the initiation or promotion assay formats. Initiation protocol of the Bhas 42 assay showed a 3.5-fold increase in transformed foci at 40 µg mL(-1) of CSC-D but not CSC-W. The promotion phase of the assay yielded a robust dose response with CSC-D (2.5-40 µg mL(-1)) and CSC-W (20-40 µg mL(-1)). Preincubation of cells with selenium (100 nM) significantly reduced CSC-induced increase in cell transformation in initiation assay. Co-treatment of cells with a sub-toxic dose of arsenic significantly enhanced cell transformation activity of CSC-D in promotion assay. The results suggest a presence of both water soluble and insoluble tumor promoters in CSC, a role of oxidative stress in CSC-induced cell transformation, and usefulness of Bhas 42 cell transformation assay in comparing tobacco product toxicities and in studying the mechanisms of tobacco carcinogenesis.

Regulatory Forum Opinion Piece*: Retrospective Evaluation of Doses in the 26-week Tg.rasH2 Mice Carcinogenicity Studies: Recommendation to Eliminate High Doses at Maximum Tolerated Dose in Future Studies. A Response to the Counterpoints.

We recently conducted a retrospective analysis of data collected from 29 Tg.rasH2 carcinogenicity studies conducted at our facility to determine how successful was the strategy of choosing the high dose of the 26-week studies based on an estimated maximum tolerated dose (MTD). As a result of our publication, 2 counterviews were expressed. Both counterviews illustrate very valid points in their interpretation of our data. In this article, we would like to highlight clarifications based on several points and issues they have raised in their papers, namely, the dose-level selection, determining if MTD was exceeded in 26-week studies, and a discussion on the number of dose groups to be used in the studies.

Regulatory Forum Commentary* Counterpoint: Dose Selection for Tg.rasH2 Mouse Carcinogenicity Studies.

High-dose selection for 6-month carcinogenicity studies of pharmaceutical candidates in Tg.rasH2-transgenic mice currently primarily relies on (1) estimation of a maximum tolerated dose (MTD) from the results of a 1-month range-finding study, (2) determination of the maximum dose administrable to the animals (maximum feasible dose [MFD]), (3) demonstration of a plateau in systemic exposure, and (4) use of a limit dose of 1,500 mg/kg/day for products with human daily doses not exceeding 500 mg. Eleven 6-month Tg.rasH2 carcinogenicity studies and their corresponding 1-month range-finding studies conducted at Merck were reviewed. High doses were set by estimation of the MTD in 6, by plateau of exposure in 3, and by MFD in 2 cases. For 4 of 6 studies where MTD was used for high-dose selection, the 1-month study accurately predicted the 6-month study tolerability whereas in the remaining 2 studies the high doses showed poorer tolerability than expected. The use of 3 or more drug-treated dose levels proved useful to ensure that a study would successfully and unambiguously demonstrate that a drug candidate was adequately evaluated for carcinogenicity at a minimally toxic high dose level, especially when the high dose may be found to exceed the MTD.

Regulatory Forum Commentary* Counterpoint: Dose Selection for rasH2 Mouse Carcinogenicity Studies.

Dose selection for the 6-month rasH2 mouse carcinogenicity studies depends heavily on the maximum tolerated dose (MTD) obtained from 1-month range-finding studies. A retrospective evaluation of range-finding studies and pivotal 6 month rasH2 mouse studies for 11 compounds demonstrated that the MTD based on at least a 10% decrease in body weight gain, mortality, and target organ toxicity in range-finding studies appropriately identified high doses for pivotal studies for 8 of 11 compounds. Two of the selected high doses were based on decreased body weight gain alone, while 7 were based on mortality at higher doses in shorter duration range-finding studies. High-dose selection was based on the maximum feasible dose for one study. The Center for Drug Evaluation and Research, U.S. Food and Drug Administration Executive Carcinogenicity Assessment Committee often suggested different doses than those proposed by the sponsor. High mortality was observed in only one pivotal study and the high dose was lowered during the course of that study.

Regulatory Forum Opinion Piece*: Retrospective Evaluation of Doses in the 26-week Tg.rasH2 Mice Carcinogenicity Studies: Recommendation to Eliminate High Doses at Maximum Tolerated Dose (MTD) in Future Studies.

High doses in Tg.rasH2 carcinogenicity studies are usually set at the maximum tolerated dose (MTD), although this dose selection strategy has not been critically evaluated. We analyzed the body weight gains (BWGs), mortality, and tumor response in control and treated groups of 29 Tg.rasH2 studies conducted at BioReliance. Based on our analysis, it is evident that the MTD was exceeded at the high and/or mid-doses in several studies. The incidence of tumors in high doses was lower when compared to the low and mid-doses of both sexes. Thus, we recommend that the high dose in male mice should not exceed one-half of the estimated MTD (EMTD), as it is currently chosen, and the next dose should be one-fourth of the EMTD. Because females were less sensitive to decrements in BWG, the high dose in female mice should not exceed two-third of EMTD and the next dose group should be one-third of EMTD. If needed, a third dose group should be set at one-eighth EMTD in males and one-sixth EMTD in females. In addition, for compounds that do not show toxicity in the range finding studies, a limit dose should be applied for the 26-week carcinogenicity studies.

Frequency of micronucleus in oral epithelial cells after exposure to mate-tea in healthy humans

OBJECTIVES: The aim of this study was to evaluate the possibility of technique simplification for cytology slides in order to evaluate the frequency of micronuclei (FMic) and conduct a experiment looking to know the FMic of oral epithelial cells of healthy volunteers exposed to mate tea (Ilex paraguarariensis). MATERIAL AND METHODS: This is a laboratorial and nonrandomized trial (quasi-experiment), where the nonusers subjects were exposed to mate-tea, consumed in the traditional way, two drinks, two times a day for a single week. Two cytology of exfoliated epithelial cells were obtained before and after the mate tea exposition. RESULTS: The sample was composed by 10 volunteers. The age ranged from 18 to 33 years (Mean 23; SD5.5). The use of mate tea did not showed significant variation in the FMic (Wilcoxon Signed Ranks Test p= .24). CONCLUSIONS: The proposed technique simplification showed to be reliable, without losses when compared to the conventional technique and with the advantage of eliminate toxic substances, becoming simple and practical tool for research in dentistry. The acute exposure to mate tea did not induce an increase of FMic in exfoliated buccal cells of healthy nondrinkers and nonsmokers subjects and may not have genotoxic effect. More human studies are needed before a conclusion can be made on the oral carcinogenic risk of mate tea to humans

No disponible

Evaluation of toxicogenomics approaches for assessing the risk of nongenotoxic carcinogenicity in rat liver.

The current gold-standard method for cancer safety assessment of drugs is a rodent two-year bioassay, which is associated with significant costs and requires testing a high number of animals over lifetime. Due to the absence of a comprehensive set of short-term assays predicting carcinogenicity, new approaches are currently being evaluated. One promising approach is toxicogenomics, which by virtue of genome-wide molecular profiling after compound treatment can lead to an increased mechanistic understanding, and potentially allow for the prediction of a carcinogenic potential via mathematical modeling. The latter typically involves the extraction of informative genes from omics datasets, which can be used to construct generalizable models allowing for the early classification of compounds with unknown carcinogenic potential. Here we formally describe and compare two novel methodologies for the reproducible extraction of characteristic mRNA signatures, which were employed to capture specific gene expression changes observed for nongenotoxic carcinogens. While the first method integrates multiple gene rankings, generated by diverse algorithms applied to data from different subsamplings of the training compounds, the second approach employs a statistical ratio for the identification of informative genes. Both methods were evaluated on a dataset obtained from the toxicogenomics database TG-GATEs to predict the outcome of a two-year bioassay based on profiles from 14-day treatments. Additionally, we applied our methods to datasets from previous studies and showed that the derived prediction models are on average more accurate than those built from the original signatures. The selected genes were mostly related to p53 signaling and to specific changes in anabolic processes or energy metabolism, which are typically observed in tumor cells. Among the genes most frequently incorporated into prediction models were Phlda3, Cdkn1a, Akr7a3, Ccng1 and Abcb4.

Alternatives to the carcinogenicity bioassay for toxicity prediction: are we there yet?

INTRODUCTION: For decades, traditional toxicology has been the ultimate source of information on the carcinogenic potential of chemicals; however, with increasing demand on regulation of chemicals and decreasing resources for testing, opportunities to accept 'alternative' approaches have dramatically expanded. The need for tools able to identify carcinogens in shorter times and at a lower cost in terms of animal lives and money is still an open issue, and the present strategies and regulations for carcinogenicity prescreening do not adequately protect human health. AREAS COVERED: This paper briefly summarizes the theories on the early steps of carcinogenesis and presents alternative detection methods for carcinogens based on genetic toxicology, structure-activity relationships and cell transformation assays. EXPERT OPINION: There is evidence that the combination of Salmonella and structural alerts for the DNA-reactive carcinogens, and in vitro cell transformation assays for nongenotoxic carcinogens, permits the identification of a very large proportion of carcinogens. If implemented, this alternative strategy could improve considerably the protection of human health.

The incidence of positive results in the mouse lymphoma TK assay (MLA) in pharmaceutical screening and their prediction by MultiCase MC4PC.

There are published data indicating that the mouse lymphoma TK assay (MLA) has an unacceptably high incidence of positive results, hence it was decided to review the MLA data generated in this laboratory for potential drug candidates. Of the 355 compounds tested, only 52 (15%) gave positive results so, even if it is assumed that all of these are non-carcinogens, the incidence of 'false positive' predictions of carcinogenicity is much lower than the 61% apparent from analysis of the literature. Furthermore, only 19 compounds (5%) were positive by a mechanism that could not be associated with the compounds primary pharmacological activity or positive responses in other genotoxicity assays. It should be noted that the majority of these compounds were not bacterial mutagens so, in most cases, the positive results were an additional indicator of genotoxicity. However, data are not available to assess any risk they might present. At least for pharmaceuticals, it appears that the MLA does not generate as many positive results as is commonly believed, and it is against this incidence that the performance of other in vitro genotoxicity tests should be compared. The predictive accuracy of the program MultiCase MC4PC was also examined using these results. The sensitivity and specificity were found to be 62 and 38%, respectively; in fact, 62% of all compounds were predicted to be positive irrespective of whether they were actually positive or negative. It was concluded that, in its current state of development, M4PC cannot be considered sufficiently accurate to be used to predict the activity of pharmaceuticals in the MLA.

Renal histopathology in toxicity and carcinogenicity studies with tert-butyl alcohol administered in drinking water to F344 rats: a pathology working group review and re-evaluation.

An independent Pathology Working Group (PWG) re-evaluated the kidney changes in National Toxicology Program (NTP) toxicology/carcinogenicity studies of tert-butyl alcohol (TBA) in F344/N rats to determine possible mode(s) of action underlying renal tubule tumors in male rats at 2-years. In the 13-week study, the PWG confirmed that the normal pattern of round hyaline droplets in proximal convoluted tubules was replaced by angular droplet accumulation, and identified precursors of granular casts in the outer medulla, changes typical of alpha(2u)-globulin (α(2u)-g) nephropathy. In the 2-year study, the PWG confirmed the NTP observation of increased renal tubule tumors in treated male groups. Linear papillary mineralization, another hallmark of the α(2u)-g pathway was present only in treated male rats. Chronic progressive nephropathy (CPN) was exacerbated in high-dose males and females, with a relationship between advanced grades of CPN and renal tumor occurrence. Hyperplasia of the papilla lining was a component of CPN in both sexes, but there was no pelvic urothelial hyperplasia. High-dose females showed no TBA-related nephrotoxicity. The PWG concluded that both α(2u)-g nephropathy and exacerbated CPN modes of action were operative in TBA renal tumorigenicity in male rats, neither of which has relevance for human cancer risk.

Further analysis of Ames-negative rodent carcinogens that are only genotoxic in mammalian cells in vitro at concentrations exceeding 1 mM, including retesting of compounds of concern.

In the analysis by Parry et al. [Parry, J. M., Parry, E., Phrakonkham, P. and Corvi, R. (2010) Analysis of published data for top concentration considerations in mammalian cell genotoxicity testing. Mutagenesis, 25, 531-538], 24 rodent carcinogens that were negative in the Ames test were identified that were only positive in mammalian cell tests at concentrations between 1 and 10 mM. These carcinogens can be subdivided into four groups as follows: (1) probable non-genotoxic (non-mutagenic) carcinogens, tumour promoters or negative for genotoxicity in vivo (n=10); (2) questionable carcinogens (n=4); (3) carcinogens with a probable genotoxic mode of action (n=5); (4) compounds where carcinogenicity or in vivo genotoxicity is unknown or unclear (n=5). It is not expected that in vitro mammalian cell tests should give positive results with Group 1 chemicals. Within Groups 2-4, five chemicals were considered a low priority because they could be detected using modified conditions because genotoxicity was associated with precipitate or pH shifts or because non-standard metabolism was required. The remaining nine chemicals were therefore considered most critical in terms of detection of genotoxic activity in mammalian cells. Daminozide was also included because it may have given positive responses between 1 and 10 mM. Many of the reported studies could have given positive results only at >1 mM because 'old' protocols were followed. These 10 chemicals have therefore been retested using modern protocols. Some were negative even up to 10 mM. Others were positive at concentrations <1 mM. Only methylolacrylamide was positive at a concentration >1 mM (2 mM = 202 µg/ml). Low-molecular weight substances may therefore require concentrations >1 mM, but further work is needed. Based on this analysis, it is concluded that the 10 mM upper limit in mammalian cell tests can be lowered without any loss of sensitivity in detecting genotoxic rodent carcinogens. A new limit of 1 mM or 500 µg/ml, whichever is the higher, is proposed.

A stable and sensitive testing system for potential carcinogens based on DNA damage-induced gene expression in human HepG2 cell.

In order to analyze potential carcinogenic and genotoxic responses caused by exposure to pollutants existing in environment, a screening method has been established in our laboratory that uses a stably transfected HepG2 cell lines containing gadd153 promoter regions which drive a luciferase reporter gene. Activation of the exogenous gadd153 promoter was quantified using the luciferase activity following drug exposure. Twenty four agents were used to evaluate this screening assay. We selected the agents, ranging from DNA alkylating agents, oxidative agent, radiation, DNA cross-linking agent, nongenotoxic carcinogens, precarcinogenic agents, which included cadmium chloride, chromium trichloride, mercuric chloride, lead nitrate, dichloro-diphenyl-trichloroethane, deltamethrin, biphenylamine, 2-aminofluorene, benzo[a]pyrene, 2,3,7,8,-tetracblorodibenzo-p-dioxin, diethyl-stilbestrol, carbon tetrachloride, mitomycin C, hydroxycamptothecin, UV, sodium fluoride, acrylamide, hydrogen peroxide. In addition, two complex genotoxic agents (water samples) existing in the environment were selected. The results showed that all 20 tested known carcinogenic and genotoxic agents were able to induce gadd153-Luc expression at a sublethal dose. In contrast, four tested non-carcinogens, included 4-acetylaminofluorene, pyrene, benzylpenicillin sodium and vitamin C, were unable to induce gadd153-Luc expression. In conclusion, this reporter system can facilitate in vitro screening for potential carcinogens. Therefore, the gadd153-Luc test system we have developed appears to be a useful and complementary system to existing genotoxic and mutagenic tests.

The utility of the K6/ODC transgenic mouse as an alternative short term dermal model for carcinogenicity testing of pharmaceuticals.

The use of transgenic rodents may overcome many limitations of traditional cancer studies. Regulatory perspectives continue to evolve as new models are developed and validated. The transgenic mouse, K6/ODC, develops epidermal tumors when exposed to genotoxic carcinogens. In this study, K6/ODC mice were evaluated for model fitness and health robustness in a 36-week study to determine oncogenic risk of residual DNA in vaccines from neoplastic cell substrates. K6/ODC and C57BL/6 mice were treated with T24-H-ras expression plasmid, carrier vector DNA, or saline topically or by subcutaneous injection. One group of K6/ODC mice received 7,12-dimethylbenz-[a]anthracene [DMBA] dermally. Only DMBA-treated mice developed papillomas by six weeks, increasing in incidence to 25 weeks. By week 11, many K6/ODC mice showed severe dehydration and dermal eczema. By week 32, (6/8) surviving K6/ODC mice showed loss of mobility and balance. Microscopic evaluation of tissues revealed dermal/sebaceous gland hyperplasia, follicular dystrophy, splenic atrophy, and amyloid deposition/neutrophilic infiltration within liver, heart, and spleen, in all K6/ODC mice. Pathology was not detected in C57BL/6 mice. Progressive adverse health, decreased survival, and failure to develop papillomas to the H-ras plasmid suggest that K6/ODC mice may be an inappropriate alternative model for detection of oncogenic DNA and pharmaceutical carcinogenicity testing.

Nonclinical safety of ziconotide: an intrathecal analgesic of a new pharmaceutical class.

Ziconotide, a potent, selective, reversible blocker of neuronal N-type voltage-sensitive calcium channels, is approved in the United States for the management of severe chronic pain in patients for whom intrathecal therapy is warranted, and who are intolerant or refractory to other treatment, such as systemic analgesics, adjunctive therapies, or intrathecal morphine. In the European Union, ziconotide is indicated for the treatment of severe chronic pain in patients who require intrathecal analgesia. Nonclinical investigations of ziconotide included a comprehensive characterization of its toxicology, incorporating acute and subchronic toxicity studies in rats, dogs, and monkeys; reproductive toxicity assessments in rats and rabbits; and mutagenic, carcinogenic evaluations performed in vivo and in vitro. Additional investigations assessed the potential for cardiotoxicity (rats) and immunogenicity (mice, rats, and guinea pigs), and the presence or absence of intraspinal granuloma formation and local cell proliferation and apoptosis (dogs). The resulting nonclinical toxicology profile was predictive of human adverse events reported in clinical trials and consistent with ziconotide's pharmacological activity. Frequently observed nonclinical behavioral effects included tremoring, shaking, ataxia, and hyperreactivity. Occurrences were generally transient and reversible upon cessation of treatment, and intolerable effects occurred at doses more than 45 times the maximum recommended clinical dose. Ziconotide was not associated with target organ toxicity, teratogenicity, or treatment-related gross or histopathological changes; it displayed no mutagenic or carcinogenic potential and no propensity to induce local cell proliferation or apoptosis. Although guinea pigs developed systemic anaphylaxis, antibodies to ziconotide were not detected in mice, rats, or guinea pigs, indicating low immunogenic potential. No evidence of granuloma formation was observed with intrathecal ziconotide treatment. In summary, the results from these nonclinical safety assessments revealed no significant toxicological risk to humans treated with ziconotide as recommended.

The use of human cell line reporter gene-based assays in chemical toxicity testing.

Genetically modified rodents allow greater sensitivity in monitoring DNA damage or gene expression than traditional rodent bioassays and have become increasingly used for toxicity testing, particularly with the greater availability of protein and DNA-based toxicity biomarkers. Here, the advantages and limitations of several in vitro reporter assays already used to study the mechanisms of toxicity are discussed in relation to the in vivo traditional and reporter-based bioassays for carcinogenicity, mutagenicity, endocrine changes and inflammation endpoints to examine the scope for refining and replacing transgenic in vivo models.

Revisión de la literatura sobre la toxicidad del sen / No disponible

El objetivo de este artículo es revisar la información de la literatura científica sobre la toxicidad de la hoja y el fruto de sen. Este análisis establece que: -No existen evidencias suficientes de que el uso crónico de sen tenga como consecuencia una alteración estructural y/o funcional de los nervios entéricos o del músculo liso intestinal. -No existe relación entre la administración a largo plazo de un extracto de sen y aparición de tumor es gastrointestinales o de otra índole en la rata. -El sen no es carcinogénico en ratas incluso después de una administración diaria durante dos años en dosis de hasta 300 mg/kg/día. -La evidencia de que se dispone en la actualidad no demuestra que exista un riesgo de genotoxicidad para los pacientes que consumen laxantes que contienen extractos de sen o senósidos (AU)

The aim of this article is to review the scientific literature about the toxicity of senna leaves and senna pods. This analysis stablish that: - There are not definitive evidences about the effects of the chronic uses of senna on the structural or functional alteration on the enteric nerves or on intestinal smooth muscle. -There is no relation between the long term administration of senna and gastrointestinal or another tumours in rats. - Senna is not carcinogenic on rats even after the daily administration, during two years, at doses of at least 300 mg/kg/day. -Nowadays, the evidences do not confirm the genotoxicity risk on patients consuming laxatives containing senna or sennosides (AU)