Evaluation of the ability of a battery of three in vitro genotoxicity tests to discriminate rodent carcinogens and non-carcinogens I. Sensitivity, specificity and relative predictivity

The performance of a battery of three of the most commonly used in vitro genotoxicity tests--Ames+mouse lymphoma assay (MLA)+in vitro micronucleus (MN) or chromosomal aberrations (CA) test--has been evaluated for its ability to discriminate rodent carcinogens and non-carcinogens, from a large database of over 700 chemicals compiled from the CPDB ("Gold"), NTP, IARC and other publications. We re-evaluated many (113 MLA and 30 CA) previously published genotoxicity results in order to categorise the performance of these assays using the response categories we established. The sensitivity of the three-test battery was high. Of the 553 carcinogens for which there were valid genotoxicity data, 93% of the rodent carcinogens evaluated in at least one assay gave positive results in at least one of the three tests. Combinations of two and three test systems had greater sensitivity than individual tests resulting in sensitivities of around 90% or more, depending on test combination. Only 19 carcinogens (out of 206 tested in all three tests, considering CA and MN as alternatives) gave consistently negative results in a full three-test battery. Most were either carcinogenic via a non-genotoxic mechanism (liver enzyme inducers, peroxisome proliferators, hormonal carcinogens) considered not necessarily relevant for humans, or were extremely weak (presumed) genotoxic carcinogens (e.g. N-nitrosodiphenylamine). Two carcinogens (5-chloro-o-toluidine, 1,1,2,2-tetrachloroethane) may have a genotoxic element to their carcinogenicity and may have been expected to produce positive results somewhere in the battery. We identified 183 chemicals that were non-carcinogenic after testing in both male and female rats and mice. There were genotoxicity data on 177 of these. The specificity of the Ames test was reasonable (73.9%), but all mammalian cell tests had very low specificity (i.e. below 45%), and this declined to extremely low levels in combinations of two and three test systems. When all three tests were performed, 75-95% of non-carcinogens gave positive (i.e. false positive) results in at least one test in the battery. The extremely low specificity highlights the importance of understanding the mechanism by which genotoxicity may be induced (whether it is relevant for the whole animal or human) and using weight of evidence approaches to assess the carcinogenic risk from a positive genotoxicity signal. It also highlights deficiencies in the current prediction from and understanding of such in vitro results for the in vivo situation. It may even signal the need for either a reassessment of the conditions and criteria for positive results (cytotoxicity, solubility, etc.) or the development and use of a completely new set of in vitro tests (e.g. mutation in transgenic cell lines, systems with inherent metabolic activity avoiding the use of S9, measurement of genetic changes in more cancer-relevant genes or hotspots of genes, etc.). It was very difficult to assess the performance of the in vitro MN test, particularly in combination with other assays, because the published database for this assay is relatively small at this time. The specificity values for the in vitro MN assay may improve if data from a larger proportion of the known non-carcinogens becomes available, and a larger published database of results with the MN assay is urgently needed if this test is to be appreciated for regulatory use. However, specificity levels of <50% will still be unacceptable. Despite these issues, by adopting a relative predictivity (RP) measure (ratio of real:false results), it was possible to establish that positive results in all three tests indicate the chemical is greater than three times more likely to be a rodent carcinogen than a non-carcinogen. Likewise, negative results in all three tests indicate the chemical is greater than two times more likely to be a rodent non-carcinogen than a carcinogen. This RP measure is considered a useful tool for industry to assess the likelihood of a chemical possessing carcinogenic potential from batteries of positive or negative results.

Hsp70 and Hsp90--a relay team for protein folding

Molecular chaperones are a functionally defined set of proteins which assist the structure formation of proteins in vivo. Without certain protective mechanisms, such as binding nascent polypeptide chains by molecular chaperones, cellular protein concentrations would lead to misfolding and aggregation. In the mammalian system, the molecular chaperones Hsp70 and Hsp90 are involved in the folding and maturation of key regulatory proteins, like steroid hormone receptors, transcription factors, and kinases, some of which are involved in cancer progression. Hsp70 and Hsp90 form a multichaperone complex, in which both are connected by a third protein called Hop. The connection of and the interplay between the two chaperone machineries is of crucial importance for cell viability. This review provides a detailed view of the Hsp70 and Hsp90 machineries, their cofactors and their mode of regulation. It summarizes the current knowledge in the field, including the ATP-dependent regulation of the Hsp70/Hsp90 multichaperone cycle and elucidates the complex interplay and their synergistic interaction.

How to reduce false positive results when undertaking in vitro genotoxicity testing and thus avoid unnecessary follow-up animal tests: Report of an ECVAM Workshop

Workshop participants agreed that genotoxicity tests in mammalian cells in vitro produce a remarkably high and unacceptable occurrence of irrelevant positive results (e.g. when compared with rodent carcinogenicity). As reported in several recent reviews, the rate of irrelevant positives (i.e. low specificity) for some studies using in vitro methods (when compared to this "gold standard") means that an increased number of test articles are subjected to additional in vivo genotoxicity testing, in many cases before, e.g. the efficacy (in the case of pharmaceuticals) of the compound has been evaluated. If in vitro tests were more predictive for in vivo genotoxicity and carcinogenicity (i.e. fewer false positives) then there would be a significant reduction in the number of animals used. Beyond animal (or human) carcinogenicity as the "gold standard", it is acknowledged that genotoxicity tests provide much information about cellular behaviour, cell division processes and cellular fate to a (geno)toxic insult. Since the disease impact of these effects is seldom known, and a verification of relevant toxicity is normally also the subject of (sub)chronic animal studies, the prediction of in vivo relevant results from in vitro genotoxicity tests is also important for aspects that may not have a direct impact on carcinogenesis as the ultimate endpoint of concern. In order to address the high rate of in vitro false positive results, a 2-day workshop was held at the European Centre for the Validation of Alternative Methods (ECVAM), Ispra, Italy in April 2006. More than 20 genotoxicity experts from academia, government and industry were invited to review data from the currently available cell systems, to discuss whether there exist cells and test systems that have a reduced tendency to false positive results, to review potential modifications to existing protocols and cell systems that might result in improved specificity, and to review the performance of some new test systems that show promise of improved specificity without sacrificing sensitivity. It was concluded that better guidance on the likely mechanisms resulting in positive results that are not biologically relevant for human health, and how to obtain evidence for those mechanisms, is needed both for practitioners and regulatory reviewers. Participants discussed the fact that cell lines commonly used for genotoxicity testing have a number of deficiencies that may contribute to the high false positive rate. These include, amongst others, lack of normal metabolism leading to reliance on exogenous metabolic activation systems (e.g. Aroclor-induced rat S9), impaired p53 function and altered DNA repair capability. The high concentrations of test chemicals (i.e. 10 mM or 5000 microg/ml, unless precluded by solubility or excessive toxicity) and the high levels of cytotoxicity currently required in mammalian cell genotoxicity tests were discussed as further potential sources of false positive results. Even if the goal is to detect carcinogens with short in vitro tests under more or less acute conditions, it does not seem logical to exceed the capabilities of cellular metabolic turnover, activation and defence processes. The concept of "promiscuous activation" was discussed. For numerous mutagens, the decisive in vivo enzymes are missing in vitro. However, if the substrate concentration is increased sufficiently, some other enzymes (that are unimportant in vivo) may take over the activation-leading to the same or a different active metabolite. Since we often do not use the right enzyme systems for positive controls in vitro, we have to rely on their promiscuous activation, i.e. to use excessive concentrations to get an empirical correlation between genotoxicity and carcinogenicity. A thorough review of published and industry data is urgently needed to determine whether the currently required limit concentration of 10mM or 5000 microg/ml, and high levels of cytotoxicity, are necessary for the detection of in vivo genotoxins and DNA-reactive, mutagenic carcinogens. In addition, various measures of cytotoxicity are currently allowable under OECD test guidelines, but there are few comparative data on whether different measures would result in different maximum concentrations for testing. A detailed comparison of cytotoxicity assessment strategies is needed. An assessment of whether test endpoints can be selected that are not intrinsically associated with cytotoxicity, and therefore are less susceptible to artefacts produced by cytotoxicity, should also be undertaken. There was agreement amongst the workshop participants that cell systems which are p53 and DNA-repair proficient, and have defined Phase 1 and Phase 2 metabolism, covering a broad set of enzyme forms, and used within the context of appropriately set limits of concentration and cytotoxicity, offer the best hope for reduced false positives. Whilst there is some evidence that human lymphocytes are less susceptible to false positives than the current rodent cell lines, other cell systems based on HepG2, TK6 and MCL-5 cells, as well as 3D skin models based on primary human keratinocytes also show some promise. Other human cell lines such as HepaRG, and human stem cells (the target for carcinogenicity) have not been used for genotoxicity investigations and should be considered for evaluation. Genetic engineering is also a valuable tool to incorporate missing enzyme systems into target cells. A collaborative research programme is needed to identify, further develop and evaluate new cell systems with appropriate sensitivity but improved specificity. In order to review current data for selection of appropriate top concentrations, measures and levels of cytotoxicity, metabolism, and to be able to improve existing or validate new assay systems, the participants called for the establishment of an expert group to identify the in vivo genotoxins and DNA-reactive, mutagenic carcinogens that we expect our in vitro genotoxicity assays to detect as well as the non-genotoxins and non-carcinogens we expect them not to detect.

Phase III study of weekly high-dose infusional fluorouracil plus folinic acid with or without irinotecan in patients with metastatic colorectal cancer: European Organisation for Research and Treatment of Cancer Gastrointestinal Group Study 40986

PURPOSE

To demonstrate that adding irinotecan to a standard weekly schedule of high-dose, infusional fluorouracil (FU) and leucovorin (folinic acid [FA]) can prolong progression-free survival (PFS).

PATIENTS AND METHODS

Four hundred thirty patients with measurable or assessable metastatic colorectal cancer were randomly assigned to receive either FA 500 mg/m(2) as a 2-hour infusion and FU 2.6 g/m(2) by intravenous 24-hour infusion, both administered weekly for 6 weeks, followed by a 2-week rest (Arbeitsgemeinschaft für Internistische Onkologie [AIO] arm, n = 216), or a similar schedule but with FU 2.3 or 2.0 g/m(2) preceded by irinotecan 80 mg/m(2) administered over 30 minutes (experimental group, n = 214).

RESULTS

The median PFS time in the experimental group was 8.5 months (95% CI, 7.6 to 9.9 months) compared with 6.4 months (95% CI, 5.3 to 7.2 months) in the AIO arm (P < .0001). The median overall survival time was increased from 16.9 to 20.1 months (P = .2779). The objective response rate was 62.2% (95% CI, 55.0% to 69.5%) in the experimental group and 34.4% (95% CI, 27.5% to 41.3%) in the AIO arm (P < .0001).

CONCLUSION

The addition of irinotecan to the standard AIO FU/FA regimen was associated with a highly significant improvement in PFS and response rate and was well tolerated. The results of this study confirm that irinotecan in combination with high-dose infusional FU/FA is a reference first-line treatment.

A rationale for determining, testing, and controlling specific impurities in pharmaceuticals that possess potential for genotoxicity

The synthesis of pharmaceutical products frequently involves the use of reactive reagents and the formation of intermediates and by-products. Low levels of some of these may be present in the final drug substance and drug product as impurities. Such chemically reactive impurities may have at the same time the potential for unwanted toxicities including genotoxicity and carcinogenicity and hence can have an impact on product risk assessment. This paper outlines a procedure for testing, classification, qualification, toxicological risk assessment, and control of impurities possessing genotoxic potential in pharmaceutical products. Referencing accepted principles of cancer risk assessment, this document proposes a staged threshold of toxicological concern (TTC) approach for the intake of genotoxic impurities over various periods of exposure. This staged TTC is based on knowledge about tumorigenic potency of a wide range of genotoxic carcinogens and can be used for genotoxic compounds, for which cancer data are limited or not available. The delineated acceptable daily intake values of between approximately 1.5 microg/day for approximately lifetime intake and approximately 120 microg/day for < or = 1 month are virtually safe doses. Based on sound scientific reasoning, these virtually safe intake values do not pose an unacceptable risk to either human volunteers or patients at any stage of clinical development and marketing of a pharmaceutical product. The intake levels are estimated to give an excess cancer risk of 1 in 100,000 to 1 in a million over a lifetime, and are extremely conservative given the current lifetime cancer risk in the population of over 1 in 4 (http://seer.cancer.gov/statfacts/html.all.html). The proposals in this document apply to all clinical routes of administration and to compounds at all stages of clinical development. It is important to note that certain types of products, such as those for life-threatening indications for which there are no safer alternatives, allow for special considerations using adaptations of the principles outlined in this paper.

Assessment of imatinib as first-line treatment of chronic myeloid leukemia: 10-year survival results of the randomized CML study IV and impact of non-CML determinants

Chronic myeloid leukemia (CML)-study IV was designed to explore whether treatment with imatinib (IM) at 400 mg/day (n=400) could be optimized by doubling the dose (n=420), adding interferon (IFN) (n=430) or cytarabine (n=158) or using IM after IFN-failure (n=128). From July 2002 to March 2012, 1551 newly diagnosed patients in chronic phase were randomized into a 5-arm study. The study was powered to detect a survival difference of 5% at 5 years. After a median observation time of 9.5 years, 10-year overall survival was 82%, 10-year progression-free survival was 80% and 10-year relative survival was 92%. Survival between IM400 mg and any experimental arm was not different. In a multivariate analysis, risk group, major-route chromosomal aberrations, comorbidities, smoking and treatment center (academic vs other) influenced survival significantly, but not any form of treatment optimization. Patients reaching the molecular response milestones at 3, 6 and 12 months had a significant survival advantage. For responders, monotherapy with IM400 mg provides a close to normal life expectancy independent of the time to response. Survival is more determined by patients' and disease factors than by initial treatment selection. Although improvements are also needed for refractory disease, more life-time can currently be gained by carefully addressing non-CML determinants of survival.

Polycyclic aromatic hydrocarbons in foods: human exposure through the diet in Catalonia, Spain

The dietary intake of 16 polycyclic aromatic hydrocarbons (PAHs) (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-c,d]pyrene) by the general population of Catalonia, Spain, was calculated. Concentrations of PAHs in food samples randomly acquired in seven cities of Catalonia from June to August 2000 were measured. Eleven food groups were included in the study. High-performance liquid chromatography was used to analyze PAHs. The dietary intakes of total and carcinogenic PAHs was calculated for five population groups: children, adolescents, male adults, female adults, and seniors. Among the analyzed PAHs, there was a predominance of phenanthrene (16.7 microg/kg) and pyrene (10.7 microg/kg). By food group, the highest levels of total PAHs were detected in cereals (14.5 microg/kg) and in meat and meat products (13.4 microg/kg). The mean estimated dietary intake of the sum of the 16 PAHs was as follows: male adults, 8.4 microg/day; adolescents, 8.2 microg/day; children, 7.4 microg/day; seniors, 6.3 microg/day; female adults, 6.3 microg/day. The calculated daily intake of PAHs would be associated with a 5/106 increase in the risk for the development of cancer in a male adult with a body weight of 70 kg.

High activity of sorafenib in FLT3-ITD-positive acute myeloid leukemia synergizes with allo-immune effects to induce sustained responses

Preliminary evidence suggests that the multikinase inhibitor sorafenib has clinical activity in FLT3-ITD-positive (FLT3-ITD) acute myeloid leukemia (AML). However, the quality and sustainability of achievable remissions and clinical variables that influence the outcome of sorafenib monotherapy are largely undefined. To address these questions, we evaluated sorafenib monotherapy in 65 FLT3-ITD AML patients treated at 23 centers. All but two patients had relapsed or were chemotherapy-refractory after a median of three prior chemotherapy cycles. Twenty-nine patients (45%) had undergone prior allogeneic stem cell transplantation (allo-SCT). The documented best responses were: hematological remission in 24 patients (37%), bone marrow remission in 5 patients (8%), complete remission (with and without normalization of peripheral blood counts) in 15 patients (23%) and molecular remission with undetectable FLT3-ITD mRNA in 10 patients (15%), respectively. Seventeen of the patients without prior allo-SCT (47%) developed sorafenib resistance after a median treatment duration of 136 days (range, 56-270 days). In contrast, allo-SCT patients developed sorafenib resistance less frequently (38%) and significantly later (197 days, range 38-225 days; P=0.03). Sustained remissions were seen exclusively in the allo-SCT cohort. Thus, sorafenib monotherapy has significant activity in FLT3-ITD AML and may synergize with allogeneic immune effects to induce durable remissions.

Cetuximab plus cisplatin-5-fluorouracil versus cisplatin-5-fluorouracil alone in first-line metastatic squamous cell carcinoma of the esophagus: a randomized phase II study of the Arbeitsgemeinschaft Internistische Onkologie

BACKGROUND

This study assessed the activity of the mAb cetuximab in combination with cisplatin and 5-fluorouracil (5-FU) in advanced esophageal squamous cell carcinoma.

PATIENTS AND METHODS

For a maximum of six 29-day cycles, patients received cisplatin 100 mg/m(2), day 1, plus 5-FU 1000 mg/m(2), days 1-5 (CF), either alone or in combination with cetuximab (CET-CF; 400 mg/m(2) initial dose followed by 250 mg/m(2) weekly thereafter). The primary end point was tumor response. Tumor material was obtained for analysis of KRAS mutation status.

RESULTS

Sixty-two eligible patients were included, 32 receiving CET-CF and 30 CF. Cetuximab did not exacerbate grade 3/4 toxicity, except for rash (6% versus 0%) and diarrhea (16% versus 0%). The overall response rate according to RECIST criteria was 19% and 13% and the disease control rate 75% and 57% for the CET-CF and CF arms, respectively. With a median follow-up of 21.5 months, the median progression-free survival was 5.9 and 3.6 months and median overall survival 9.5 and 5.5 months for CET-CF and CF, respectively. No KRAS codon 12/13 tumor mutations were identified in 37 evaluated samples.

CONCLUSION

Cetuximab can be safely combined with CF chemotherapy and may increase the efficacy of standard CF chemotherapy.

Consequences of cadmium toxicity in rat hepatocytes: mitochondrial dysfunction and lipid peroxidation

Cadmium (Cd) (10-100 microM) decreased the ATP/ADP ratio and enhanced lipid peroxidation (LPO) (measured as thiobarbituric acid reactants) in incubated rat hepatocytes. Analysis of the subcellular distribution of Cd indicated its preferential attachment to the inner membranes of mitochondria. Incubation of isolated mitochondria with 0.005-0.05 microM Cd resulted in increased formation of formazans from nitroblue tetrazolium salts, indicating enhanced membrane permeability to succinate. These Cd-concentrations also diminished mitochondrial ATP. LPO in mitochondria strongly increased only after Cd-exposures above 1 microM Cd. Similarly, in Cd-treated hepatocytes decreases in ATP/ADP ratios corresponded to increases in LPO stimulation only at 30 and 60 min but not at 15 min of incubation when ATP/ADP ratios were already affected. Moreover, neither hepatocellular ATP/ADP decrease nor mitochondrial formazan formation due to Cd were prevented by (+)-cyanidanol-3, an effective inhibitor of Cd-induced LPO. These data suggest that even low Cd-concentrations in the hepatocyte disturb the integrity of its mitochondrial membranes concomitantly impairing the hepatocellular energy supply. LPO, only observed at higher Cd-concentrations, is not responsible for these adverse Cd-effects.

PET study of [11C]beta-CIT binding to monoamine transporters in the monkey and human brain

The cocaine congener beta-CIT has been labeled with 11C for positron emission tomographic (PET) studies of the dopamine transporter. In the present autoradiographic study on human brain sections and PET study on monkey and human [11C]beta-CIT accumulated markedly in the striatum. [11C]beta-CIT binding in the striatum was selective to the dopamine transporter. The binding in the thalamus was on an intermediate level and was displaced by compounds having affinity for norepinephrine and serotonin transporters. The neocortical binding was on a low level and could be displaced only by citalopram, a serotonin uptake inhibitor. A high dose of cocaine intravenously (7 mg/kg) induced a 50% occupancy of specific [11C]beta-CIT binding to the dopamine transporter in the striatum. This dose is much higher than the doses of 0.25-0.5 mg/kg i.v. for cocaine arousal in human subjects. The finding indicates that cocaine arousal may be induced at a low dopamine transporter occupancy of a few percent. [11C]beta-CIT should be a useful radioligand to explore cocaine actions in humans and to follow the pathophysiological process in vivo by PET in neurodegenerative diseases of the striatum.

Functions and pathologies of BiP and its interaction partners

The endoplasmic reticulum (ER) is involved in a variety of essential and interconnected processes in human cells, including protein biogenesis, signal transduction, and calcium homeostasis. The central player in all these processes is the ER-lumenal polypeptide chain binding protein BiP that acts as a molecular chaperone. BiP belongs to the heat shock protein 70 (Hsp70) family and crucially depends on a number of interaction partners, including co-chaperones, nucleotide exchange factors, and signaling molecules. In the course of the last five years, several diseases have been linked to BiP and its interaction partners, such as a group of infectious diseases that are caused by Shigella toxin producing E. coli. Furthermore, the inherited diseases Marinesco-Sjögren syndrome, autosomal dominant polycystic liver disease, Wolcott-Rallison syndrome, and several cancer types can be considered BiP-related diseases. This review summarizes the physiological and pathophysiological characteristics of BiP and its interaction partners.

Tobacco smoke: unraveling a controversial subject

Cigarettes are a modern and industrial form of tobacco use and obviously involve more than just tobacco. A multitude of physical processes and chemical reactions occur inside the burning zone of a cigarette. Cigarette smoke is an aerosol of liquid droplets (the particulate phase) suspended within a mixture of gases and semi-volatile compounds. Two kinds of smoke with different composition and properties are produced during smoking: mainstream smoke inhaled by the smoker and sidestream smoke, which is released into the environment between puffs from the lit end of the cigarette. Several techniques and modifications have altered the design of the cigarette during the last 50 years and changed smoke composition, with the effect of lower tar and nicotine smoke yields. An enormous amount of research has been done since the 1950s on smoke composition. With regard to the numerous toxic or carcinogenic constituents identified in tobacco smoke, there is a strong focus in the industry and with the authorities on the over 40 compounds, called "Hoffmann analytes". The yields of tar and nicotine in mainstream smoke of a cigarette brand as printed on the pack are measured with smoking machines under highly standardized conditions. Yields must comply with regulatory limits set in a number of countries. Smoking by machine is different from the smoking behavior of humans. There is a growing movement to develop more "realistic" methods to estimate smoke yields. But it is unclear whether alternative smoking regimens are more representative of human smoking behavior and provide better predictions of human exposure. Tobacco smoke has strong biological and toxicological effects in vitro and in vivo. There is an obvious need for developing a unified and validated testing approach particularly for the assessment of additives and the evaluation of new potentially reduced exposure products (PREPs). This paper gives a comprehensive overview of cigarette design, the composition and toxicity testing of smoke, and the way machines and people smoke - with links to the more detailed literature.

Irinotecan combined with infusional 5-fluorouracil/folinic acid or capecitabine plus celecoxib or placebo in the first-line treatment of patients with metastatic colorectal cancer. EORTC study 40015

BACKGROUND

The study aimed to demonstrate the noninferiority of capecitabine to 5-fluorouracil (5-FU)/folinic acid (FA), in relation to progression-free survival (PFS) after first-line treatment of metastatic colorectal cancer and the benefit of adding celecoxib (C) to irinotecan/fluoropyrimidine regimens compared with placebo (P).

PATIENTS AND METHODS

Patients were randomly assigned to receive FOLFIRI: irinotecan (180 mg/m(2) i.v. on days 1, 15 and 22); FA (200 mg/m(2) i.v. on days 1, 2, 15, 16, 29 and 30); 5-FU (400 mg/m(2) i.v. bolus, then 22-h, 600 mg/m(2) infusion) or CAPIRI: irinotecan (250 mg/m(2) i.v. infusion on days 1 and 22); capecitabine p.o. (1000 mg/m(2) b.i.d. on days 1-15 and 22-36). Patients were additionally randomly assigned to receive either placebo or celecoxib (800 mg: 2 x 200 mg b.i.d.).

RESULTS

The trial was closed following eight deaths unrelated to disease progression in the 85 enrolled (629 planned) patients. Response rates were 22% for CAPIRI + C, 48% for CAPIRI + P, 32% for FOLFIRI + C and 46% for FOLFIRI + P. Median PFS and overall survival (OS) times were shorter for CAPIRI versus FOLFIRI (PFS 5.9 versus 9.6 months and OS 14.8 versus 19.9 months) and celecoxib versus placebo (PFS 6.9 versus 7.8 months and OS 18.3 versus 19.9 months).

CONCLUSION

Due to the small sample size following early termination, no definitive conclusions can be drawn in relation to the noninferiority of CAPIRI compared with FOLFIRI.

Recurrent finding of the FIP1L1-PDGFRA fusion gene in eosinophilia-associated acute myeloid leukemia and lymphoblastic T-cell lymphoma

The FIP1L1-PDGFRA fusion gene has been described in patients with eosinophilia-associated myeloproliferative disorders (Eos-MPD). Here, we report on seven FIP1L1-PDGFRA-positive patients who presented with acute myeloid leukemia (AML, n=5) or lymphoblastic T-cell non-Hodgkin-lymphoma (n=2) in conjunction with AML or Eos-MPD. All patients were male, the median age was 58 years (range, 40-66). AML patients were negative for common mutations of FLT3, NRAS, NPM1, KIT, MLL and JAK2; one patient revealed a splice mutation of RUNX1 exon 7. Patients were treated with imatinib (100 mg, n=5; 400 mg, n=2) either as monotherapy (n=2), as maintenance treatment after intensive chemotherapy (n=3) or in overt relapse 43 and 72 months, respectively, after primary diagnosis and treatment of FIP1L1-PDGFRA-positive disease (n=2). All patients are alive, disease-free and in complete hematologic and complete molecular remission after a median time of 20 months (range, 9-36) on imatinib. The median time to achievement of complete molecular remission was 6 months (range, 1-14). We conclude that all eosinophilia-associated hematological malignancies should be screened for the presence of the FIP1L1-PDGFRA fusion gene as they are excellent candidates for treatment with tyrosine kinase inhibitors even if they present with an aggressive phenotype such as AML.

ICH-harmonised guidances on genotoxicity testing of pharmaceuticals: evolution, reasoning and impact

The International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) has convened an expert working group which consisted of the authors of this paper and their respective committees, consulting groups and task forces. Two ICH guidances regarding genotoxicity testing have been issued: S2A, 'Guidance on Specific Aspects of Regulatory Genotoxicity Tests' and S2B, 'Genotoxicity: A Standard Battery for Genotoxicity Testing of Pharmaceuticals.' Together, these guidance documents now form the regulatory backbone for genotoxicity testing and assessment of pharmaceuticals in the European Union, Japan, and the USA. These guidances do not constitute a revolutionary new approach to genotoxicity testing and assessment, instead they are an evolution from preexisting regional guidelines, guidances and technical approaches. Both guidances describe a number of specific criteria as well as a general test philosophy in genotoxicity testing. Although these guidances were previously released within the participating regions in their respective regulatory communiqués, to ensure their wider distribution and better understanding, the texts of the guidances are reproduced here in their entirety (see Appendix A) and the background for the recommendations are described. The establishment of a standard battery for genotoxicity testing of pharmaceuticals was one of the most important issues of the harmonisation effort. This battery currently consists of: (i) a test for gene mutation in bacteria, (ii) an in vitro test with cytogenetic evaluation of chromosomal damage with mammalian cells or an in vitro mouse lymphoma tk assay, (iii) an in vivo test for chromosomal damage using rodent hematopoietic cells. A major change in testing philosophy is the acceptance of the interchangeability of testing for chromosomal aberrations in mammalian cells and the mouse lymphoma tk assay. This agreement was reached on the basis of the extensive review of databases and newly generated experimental data which are in part described in this publication. The authors are fully aware of the fact that some of the recommendations given in these ICH guidances are transient in nature and that the dynamic qualities and ongoing evolution of genetic toxicology makes necessary a continuous maintenance process that would serve to update the guidance as necessary.