Comprehensive genotoxicity and carcinogenicity assessment of molnupiravir

Molnupiravir is registered or authorized in several countries as a 5-d oral coronavirus disease 2019 treatment for adults. Molnupiravir is a prodrug of the antiviral ribonucleoside β-D-N4-hydroxycytidine (NHC) that distributes into cells, where it is phosphorylated to its pharmacologically active ribonucleoside triphosphate (NHC-TP) form. NHC-TP incorporates into severe acute respiratory syndrome coronavirus 2 RNA by the viral RNA-dependent RNA polymerase, resulting in an accumulation of errors in the viral genome, leading to inhibition of viral replication and loss of infectivity. The potential of molnupiravir to induce genomic mutations and DNA damage was comprehensively assessed in several in vitro and in vivo genotoxicity assays and a carcinogenicity study, in accordance with international guideline recommendations and expert opinion. Molnupiravir and NHC induced mutations in vitro in bacteria and mammalian cells but did not induce chromosome damage in in vitro or in vivo assays. The in vivo mutagenic and carcinogenic potential of molnupiravir was tested in a series of in vivo mutagenicity studies in somatic and germ cells (Pig-a Assay and Big Blue® TGR Mutation Assay) and in a carcinogenicity study (transgenic rasH2-Tg mouse), using durations of exposure and doses exceeding those used in clinical therapy. In vitro genotoxicity results are superseded by robustly conducted in vivo studies. Molnupiravir did not increase mutations in somatic or germ cells in the in vivo animal studies and was negative in the carcinogenicity study. The interpretation criteria for each study followed established regulatory guidelines. Taken together, these data indicate that molnupiravir use does not present a genotoxicity or carcinogenicity risk for patients.

Genotoxic mode of action and threshold exploration of 2-methyl furan under 120-day sub-chronic exposure in male Sprague-Dawley rats

2-Methylfuran (2-MF) is an important member of the furan family generated during food thermal processing. An in-vivo multiple endpoint genotoxicity assessment system was applied to explore the genotoxic mode of action and threshold of 2-MF. Male Sprague-Dawley rats received 2-MF by oral gavage at doses of 0.16, 0.625, 2.5, and 10 mg/kg.bw/day for 120 days. An additional 15 days were granted for recovery. The Pig-a gene mutation frequency of RET and RBC showed significant increases among the 2-MF groups on day 120. After a 15-day recovery period, the Pig-a gene mutation frequency returned to levels similar to those in the vehicle control. The tail intensity (TI) values of peripheral blood cells at a dose of 10 mg/kg.bw/day significantly increased from day 4 and remained at a high level after the recovery period. No statistical difference was found in the micronucleus frequency of peripheral blood between any 2-MF dose group and the corn oil group at any timepoint. 2-MF may not induce the production of micronuclei, but it could cause DNA breakage. It could not be ruled out that 2-MF may accumulate in vivo and cause gene mutations. Hence, DNA, other than the spindle, may be directly targeted. The mode of action of 2-MF may be that it was metabolized by EPHX1 to more DNA-active metabolites, thus leading to oxidative and direct DNA damage. The point of departure (PoD) of 2-MF-induced genotoxicity was derived as 0.506 mg/kg bw/day.

Assessment of the three-test genetic toxicology battery for groundwater metabolites

The two-test in vitro battery for genotoxicity testing (Ames and micronucleus) has in the majority of cases replaced the three-test battery (as two-test plus mammalian cell gene mutation assay) for the routine testing of chemicals, pharmaceuticals, cosmetics, and agrochemical metabolites originating from food and feed as well as from water treatment. The guidance for testing agrochemical groundwater metabolites, however, still relies on the three-test battery. Data collated in this study from 18 plant protection and related materials highlights the disparity between the often negative Ames and in vitro chromosome aberration data and frequently positive in vitro mammalian cell gene mutation assays. Sixteen of the 18 collated materials with complete datasets were Ames negative, and overall had negative outcomes in in vitro chromosome damage tests (weight of evidence from multiple tests). Mammalian cell gene mutation assays (HPRT and/or mouse lymphoma assay (MLA)) were positive in at least one test for every material with this data. Where both MLA and HPRT tests were performed on the same material, the HPRT seemed to give fewer positive responses. In vivo follow-up tests included combinations of comet assays, unscheduled DNA synthesis, and transgenic rodent gene mutation assays, all gave negative outcomes. The inclusion of mammalian cell gene mutation assays in a three-test battery for groundwater metabolites is therefore not justified and leads to unnecessary in vivo follow-up testing.

Comparison of the transgenic rodent mutation assay, error corrected next generation duplex sequencing, and the alkaline comet assay to detect dose-related mutations following exposure to N-nitrosodiethylamine

N-Nitrosodiethylamine (NDEA), a well-studied N-nitrosamine, was tested in rats to compare the dose-response relationship of three genotoxicity endpoints. Mutant / mutation frequencies were determined using the transgenic rodent (TGR) gene mutation assay and error corrected next generation sequencing (ecNGS) (i.e., duplex sequencing (DS)), and genetic damage was detected by the alkaline comet assay. Big Blue® (cII Locus) animals (n = 6 per dose group) were administered doses of 0.001, 0.01, 0.1, 1, 3 mg/kg/day NDEA by oral gavage. Samples were collected for cII mutation and DS analyses following 28-days of exposure and 3 days recovery. In a separate study, male Sprague-Dawley (SD) rats (n = 6 per dose group) were administered the same doses by oral gavage for two consecutive days and then samples collected for the alkaline comet assay. A dose-related increase in mutant / mutation frequencies of the liver but not duodenum was observed using the TGR assay and DS with DS resulting in a slightly more sensitive response, with a lower benchmark dose (BMD). In addition, a dose-related increase in percent tail DNA was observed in the liver using the alkaline comet assay. Therefore, DS and comet assays showed good utility for hazard identification and dose-response analysis of a representative N-nitrosamine comparable to the TGR gene mutation assay.

Systematic review of the association between talc and female reproductive tract cancers

Talc is a hydrous magnesium sheet silicate used in cosmetic powders, ceramics, paints, rubber, and many other products. We conducted a systematic review of the potential carcinogenicity of genitally applied talc in humans. Our systematic review methods adhere to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and incorporated aspects from the US Institute of Medicine (IOM, now the National Academy of Medicine) and several US EPA frameworks for systematic reviews, evaluating and integrating the epidemiological, animal, and mechanistic literature on talc and cancer. We conducted a comprehensive literature search. Detailed data abstraction and study quality evaluation, adapting the Toxic Substances Control Act (TSCA) framework, were central to our analysis. The literature search and selection process identified 40 primary studies that assessed exposure to talc and female reproductive cancer risks in humans (n = 36) and animals (n = 4). The results of our evaluation emphasize the importance of considering biological plausibility and study quality in systematic review. Integrating all streams of evidence according to the IOM framework yielded classifications of suggestive evidence of no association between perineal application of talcum powders and risk of ovarian cancer at human-relevant exposure levels. We also concluded that there is suggestive evidence of no association between genital talc application and endometrial cancer, and insufficient evidence to determine whether a causal association exists between genital talc application and cervical cancer based on a smaller but largely null body of literature.

Efficacy and safety of Molnupiravir in COVID-19 patients: a systematic review

BACKGROUND

Molnupiravir is an oral antiviral drug that received Emergency Use Authorization in three countries for the treatment of mild COVID-19. The aim of this systematic review was to find out the safety and efficacy of Molnupiravir in SARS-COV-2 infections.

METHODS

The electronic databases such as PubMed, MedRxiv, BioRxiv, FDA, ClinicalTrials.Gov, ctri.nic.in and Google Scholar were searched for articles from January 2021 to March 2022 using the keywords such as "Molnupiravir", "COVID-19", "Oral antiviral pill", "MK-4482", "EIDD-280", "Efficacy" and "Safety". Details of published, unpublished with interim reports and ongoing studies of Molnupiravir in COVID-19 were retrieved, and a systematic review was performed.

RESULTS

A total of 6 articles and 18 ongoing trials data were collected. Out of these, data from 4 published and 2 unpublished with interim reports were extracted. After review of these studies, it was observed that the daily dose of 1600 mg Molnupiravir for 5 days was safe and tolerable with nausea, diarrhea and headache as the common adverse effects. The results also showed significant decrease in time to viral clearance with 800 mg twice daily in mild patients and reduction in the risk of hospitalization or death by 50% in non-hospitalized COVID-19 patients.

CONCLUSION

Evidence from clinical studies showed that Molnupiravir caused significant reduction in the risk of hospitalization or death in high-risk mild COVID-19 patients. Molnupiravir was also found to be well tolerated and safe without any major adverse events on short-term use. For confirmative use of this drug in mild-to-moderate COVID-19 disease, further studies are required in vaccinated COVID-19 patients and against emerging variants.

Exposure to nanoplastic particles and DNA damage in mammalian cells

There is concern about human exposure to nanoplastics from intentional use or degradation of plastics in the environment. This review assesses genotoxic effects of nanoplastics, defined as particles with a primary size of less than 1000 nm. The majority of results on genotoxicity come from studies on polystyrene (PS) particles in mammalian cell cultures. Most studies have measured DNA strand breaks (standard comet assay), oxidatively damaged DNA (Fpg-modified comet assay) and micronuclei. Twenty-nine out of 60 results have shown statistically significant genotoxic effects by PS exposure in cell cultures. A statistical analysis indicates that especially modified PS particles are genotoxic (odds ratio = 8.6, 95 % CI: 1.6, 46) and immune cells seems to be more sensitive to genotoxicity than other cell types such as epithelial cells (odds ratio = 8.0, 95 % CI: 1.6, 39). On the contrary, there is not a clear association between statistically significant effects in genotoxicity tests and the primary size of PS particles, (i.e. smaller versus larger than 100 nm) or between the type of genotoxic endpoint (i.e. repairable versus permanent DNA lesions). Three studies of PS particle exposure in animals have shown increased level of DNA strand breaks in leukocytes and prefrontal cortex cells. Nanoplastics from polyethylene, propylene, polyvinyl chloride and polyethylene terephthalate have been investigated in very few studies and it is currently not possible to draw conclusion about their genotoxic hazard. In summary, there is some evidence suggesting that PS particles may be genotoxic in mammalian cells.

Search for the optimal genotoxicity assay for routine testing of chemicals: Sensitivity and specificity of conventional and new test systems

Many conventional in vitro tests that are currently widely used for routine screening of chemicals have a sensitivity/specificity in the range between 60 % and 80 % for the detection of carcinogens. Most procedures were developed 30-40 years ago. In the last decades several assays became available which are based on the use of metabolically competent cell lines, improvement of the cultivation conditions and development of new endpoints. Validation studies indicate that some of these models may be more reliable for the detection of genotoxicants (i.e. many of them have sensitivity and specificity values between 80 % and 95 %). Therefore, they could replace conventional tests in the future. The bone marrow micronucleus (MN) assay with rodents is at present the most widely used in vivo test. The majority of studies indicate that it detects only 5-6 out of 10 carcinogens while experiments with transgenic rodents and comet assays seem to have a higher predictive value and detect genotoxic carcinogens that are negative in MN experiments. Alternatives to rodent experiments could be MN experiments with hen eggs or their replacement by combinations of new in vitro tests. Examples for promising candidates are ToxTracker, TGx-DDI, multiplex flow cytometry, γH2AX experiments, measurement of p53 activation and MN experiments with metabolically competent human derived liver cells. However, the realization of multicentric collaborative validation studies is mandatory to identify the most reliable tests.

Molnupiravir and Its Antiviral Activity Against COVID-19

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) constitutes a major worldwide public health threat and economic burden. The pandemic is still ongoing and the SARS-CoV-2 variants are still emerging constantly, resulting in an urgent demand for new drugs to treat this disease. Molnupiravir, a biological prodrug of NHC (β-D-N(4)-hydroxycytidine), is a novel nucleoside analogue with a broad-spectrum antiviral activity against SARS-CoV, SARS-CoV-2, Middle East respiratory syndrome coronavirus (MERS-CoV), influenza virus, respiratory syncytial virus (RSV), bovine viral diarrhea virus (BVDV), hepatitis C virus (HCV) and Ebola virus (EBOV). Molnupiravir showed potent therapeutic and prophylactic activity against multiple coronaviruses including SARS-CoV-2, SARS-CoV, and MERS-CoV in animal models. In clinical trials, molnupiravir showed beneficial effects for mild to moderate COVID-19 patients with a favorable safety profile. The oral bioavailability and potent antiviral activity of molnupiravir highlight its potential utility as a therapeutic candidate against COVID-19. This review presents the research progress of molnupiravir starting with its discovery and synthesis, broad-spectrum antiviral effects, and antiviral mechanism. In addition, the preclinical studies, antiviral resistance, clinical trials, safety, and drug tolerability of molnupiravir are also summarized and discussed, aiming to expand our knowledge on molnupiravir and better deal with the COVID-19 epidemic.

Molnupiravir Does Not Induce Mutagenesis in Host Lung Cells during SARS-CoV-2 Treatment

As SARS-CoV-2 continues to evolve and spread with the emergence of new variants, interest in small molecules with broad-spectrum antiviral activity has grown. One such molecule, Molnupiravir (MOV; other names: MK-4482, EIDD-2801), a ribonucleoside analogue, has emerged as an effective SARS-CoV-2 treatment by inducing catastrophic viral mutagenesis during replication. However, there are growing concerns as MOV’s potential to induce host DNA mutagenesis remains an open question. Analysis of RNA-seq data from SARS-CoV-2–infected MOV-treated golden hamster lung biopsies confirmed MOV’s efficiency in stopping SARS-CoV-2 replication. Importantly, MOV treatment did not increase mutations in the host lung cells. This finding calls for additional mutation calls on host biopsies from more proliferative tissues to fully explore MOV’s hypothesized mutagenic risk.

Human genetic risk of treatment with antiviral nucleoside analog drugs that induce lethal mutagenesis: The special case of molnupiravir

This review considers antiviral nucleoside analog drugs, including ribavirin, favipiravir, and molnupiravir, which induce genome error catastrophe in SARS-CoV or SARS-CoV-2 via lethal mutagenesis as a mode of action. In vitro data indicate that molnupiravir may be 100 times more potent as an antiviral agent than ribavirin or favipiravir. Molnupiravir has recently demonstrated efficacy in a phase 3 clinical trial. Because of its anticipated global use, its relative potency, and the reported in vitro "host" cell mutagenicity of its active principle, β-d-N4-hydroxycytidine, we have reviewed the development of molnupiravir and its genotoxicity safety evaluation, as well as the genotoxicity profiles of three congeners, that is, ribavirin, favipiravir, and 5-(2-chloroethyl)-2'-deoxyuridine. We consider the potential genetic risks of molnupiravir on the basis of all available information and focus on the need for additional human genotoxicity data and follow-up in patients treated with molnupiravir and similar drugs. Such human data are especially relevant for antiviral NAs that have the potential of permanently modifying the genomes of treated patients and/or causing human teratogenicity or embryotoxicity. We conclude that the results of preclinical genotoxicity studies and phase 1 human clinical safety, tolerability, and pharmacokinetics are critical components of drug safety assessments and sentinels of unanticipated adverse health effects. We provide our rationale for performing more thorough genotoxicity testing prior to and within phase 1 clinical trials, including human PIG-A and error corrected next generation sequencing (duplex sequencing) studies in DNA and mitochondrial DNA of patients treated with antiviral NAs that induce genome error catastrophe via lethal mutagenesis.

Utility of a next-generation framework for assessment of genomic damage: A case study using the pharmaceutical drug candidate etoposide

We present a hypothetical case study to examine the use of a next-generation framework developed by the Genetic Toxicology Technical Committee of the Health and Environmental Sciences Institute for assessing the potential risk of genetic damage from a pharmaceutical perspective. We used etoposide, a genotoxic carcinogen, as a representative pharmaceutical for the purposes of this case study. Using the framework as guidance, we formulated a hypothetical scenario for the use of etoposide to illustrate the application of the framework to pharmaceuticals. We collected available data on etoposide considered relevant for assessment of genetic toxicity risk. From the data collected, we conducted a quantitative analysis to estimate margins of exposure (MOEs) to characterize the risk of genetic damage that could be used for decision-making regarding the predefined hypothetical use. We found the framework useful for guiding the selection of appropriate tests and selecting relevant endpoints that reflected the potential for genetic damage in patients. The risk characterization, presented as MOEs, allows decision makers to discern how much benefit is critical to balance any adverse effect(s) that may be induced by the pharmaceutical. Interestingly, pharmaceutical development already incorporates several aspects of the framework per regulations and health authority expectations. Moreover, we observed that quality dose response data can be obtained with carefully planned but routinely conducted genetic toxicity testing. This case study demonstrates the utility of the next-generation framework to quantitatively model human risk based on genetic damage, as applicable to pharmaceuticals.

Developing a direct acting, orally available antiviral agent in a pandemic: the evolution of molnupiravir as a potential treatment for COVID-19

Despite the availability of vaccines, there remains an urgent need for antiviral drugs with potent activity against SARS-CoV-2, the cause of COVID-19. Millions of people are immune-suppressed and may not be able to mount a fully protective immune response after vaccination. There is also an increasingly critical need for a drug to cover emerging SARS-CoV-2 variants, against which existing vaccines may be less effective. Here, we describe the evolution of molnupiravir (EIDD-2801, MK-4482), a broad-spectrum antiviral agent originally designed for the treatment of Alphavirus infections, into a potential drug for the prevention and treatment of COVID-19. When the pandemic began, molnupiravir was in pre-clinical development for the treatment of seasonal influenza. As COVID-19 spread, the timeline for the development program was moved forward significantly, and focus shifted to treatment of coronavirus infections. Real time consultation with regulatory authorities aided in making the acceleration of the program possible.

From environmental bioavailability of metal(loid)s to their ecogenotoxicological effects in land snails

To date, no study has linked the environmental and the ecogenotoxicological bioavailability of contaminants to land snails. Yet, understanding the specific ecotoxicological mechanisms from bioaccumulation to genotoxicity is necessary e.g., to build an adverse outcome pathway relevant to risk assessment. Consequently, the aim of our study is to look for relationships between accumulated concentrations of As, Cd and Hg in sub-adult snails and ecotoxicological effects at the individual (survival and growth) and molecular (genomic stability) levels. This study combines random amplified polymorphic DNA (RAPD) coupled with high-resolution capillary electrophoresis system (HRS) and micronucleus (MN) assay on haemocytes to consider various types of cytogenomic damage, such as chromosomal aberrations, breakages, adducts and mutations. The results showed alteration of the individual endpoints at higher accumulation quotients (AQs) that reflect the excess of transfers to snails, especially with decreased survival for As. In addition, genotoxic effects were observed with an increased occurrence of MN in haemocytes for the three meta(loid)s considered (R² from 0.57 to 0.61 as a function of the meta(loid)s). No concentration-dependent decrease in genome stability was highlighted by RAPD-HRS in snails exposed to As and Cd but not Hg. Our results demonstrate the complementarity of the RAPD-HRS and the MN assay for understanding the different genotoxic mechanisms of the three metal(loid)s studied in land snails. They show a way to better assess environmental risks of contaminated soils by associating ecotoxicity, genotoxicity and bioaccumulation assays (ISO 24032), i.e., ecogenotoxicological bioavailability. Convergences highlighted here between the bioaccumulation of metal(loid)s in viscera and genotoxic effects in haemocytes constitute a way to better assess the bioavailability of contaminants in soils to the land snail and the subsequent environmental risk.

Preliminary Evidence for a Hormetic Effect on DNA Nucleotide Excision Repair in Veterans with Gulf War Illness

Introduction

Veterans of the 1991 Gulf War were potentially exposed to a mixture of stress, chemicals and radiation that may have contributed to the persistent symptoms of Gulf War Illness (GWI). The genotoxic effects of some of these exposures are mediated by the DNA nucleotide excision repair (NER) pathway. We hypothesized that individuals with relatively low DNA repair capacity would suffer greater damage from cumulative genotoxic exposures, some of which would persist, causing ongoing problems.

Materials and Methods

Blood samples were obtained from symptomatic Gulf War veterans and age-matched controls. The unscheduled DNA synthesis assay, a functional measurement of NER capacity, was performed on cultured lymphocytes, and lymphocyte mRNA was extracted and analyzed by sequencing.

Results

Despite our hypothesis that GWI would be associated with DNA repair deficiency, NER capacity in lymphocytes from affected GWI veterans actually exhibited a significantly elevated level of DNA repair (p = 0.016). Both total gene expression and NER gene expression successfully differentiated individuals with GWI from unaffected controls. The observed functional increase in DNA repair capacity was accompanied by an overexpression of genes in the NER pathway, as determined by RNA sequencing analysis.

Conclusion

We suggest that the observed elevations in DNA repair capacity and NER gene expression are indicative of a “hormetic,” i.e., induced or adaptive protective response to battlefield exposures. Normally such effects are short-term, but in these individuals this response has resulted in a long-term metabolic shift that may also be responsible for the persistent symptoms of GWI.

APC gene 3'UTR SNPs and interactions with environmental factors are correlated with risk of colorectal cancer in Chinese Han population

Objective: To study the correlation between adenomatous polyposis coli (APC) gene 3′ untranslated region (UTR) single nucleotide polymorphisms (SNPs) and their interactions with environmental factors and the risk of colorectal cancer (CRC) in a Chinese Han population.

Methods: Genotypes of APC gene 3′UTR rs1804197, rs41116, rs448475, and rs397768 loci in 340 Chinese Han patients with CRC and 340 healthy controls were analyzed. All patients with CRC were analyzed for progression-free survival (PFS) during a 3-year follow-up.

Results: The risk of CRC in subjects carrying the APC gene rs1804197 A allele was 2.95-times higher than for the C allele carriers. The interactions of the rs1804197 SNP with body mass index (BMI) and smoking were associated with the risk of CRC. The risk of CRC in the APC gene rs397768 G allele carriers was 1.68-times higher than in the A allele carriers. The interaction between the rs397768 locus SNP and gender was also associated with the risk of CRC. The 3-year PFS of patients with APC gene rs1804197 AA genotype, CA genotype, and CC genotype CRC decreased in this order, with significant difference. In addition, the 3-year PFS of rs397768 locus GG genotype, AG genotype, and AA genotype CRC patients decreased in this order, and the difference was significant.

Conclusion: The rs1804197 locus in the 3′UTR region of the APC gene and its interactions with BMI and smoking are associated with the risk of CRC in a Chinese Han population. In addition, the interaction between rs397768 locus SNP and gender is related to the risk of CRC.

No Genotoxicity Is Detectable for Escherichia coli Strain Nissle 1917 by Standard In Vitro and In Vivo Tests

Probiotic Escherichia coli strain Nissle 1917 (EcN) has a long history of safe use. However, the recently discovered presence of a pks locus in its genome presumably producing colibactin has questioned its safety, as colibactin has been implicated in genotoxicity. Here, we assess the genotoxic potential of EcN. Metabolic products were tested in vitro by the Ames test, a mutagenicity assay developed to detect point mutation-inducing activity. Live EcN were tested by an adapted Ames test. Neither the standard nor the adapted Ames test resulted in increased numbers of revertant colonies, indicating that EcN metabolites or viable cells lacked mutagenic activity. The in vivo Mammalian Alkaline Comet Assay (the gold standard for detecting DNA-strand breaks) was used to determine potentially induced DNA-strand breaks in cells of the gastro-intestinal tract of rats orally administered with viable EcN. Bacteria were given at 10⁹–10¹¹ colony forming units (CFU) per animal by oral gavage on 2 consecutive days and daily for a period of 28 days to 5 rats per group. No significant differences compared to negative controls were found. These results demonstrate that EcN does not induce DNA-strand breaks and does not have any detectable genotoxic potential in the test animals.

3Rs friendly study designs facilitate rat liver and blood micronucleus assays and Pig-a gene mutation assessments: Proof-of-concept with 13 reference chemicals

Regulatory guidance documents stress the value of assessing the most appropriate endpoints in multiple tissues when evaluating the in vivo genotoxic potential of chemicals. However, conducting several independent studies to evaluate multiple endpoints and/or tissue compartments is resource intensive. Furthermore, when dependent on visual detection, conventional approaches for scoring genotoxicity endpoints can be slow, tedious, and less objective than the ideal. To address these issues with current practices we attempted to (1) devise resource sparing treatment and harvest schedules that are compatible with liver and blood micronucleus endpoints, as well as the Pig-a gene mutation assay, and (2) utilize flow cytometry-based methods to score each of these genotoxicity biomarkers. Proof-of-principle experiments were performed with 4-week-old male and female Crl:CD(SD) rats exposed to aristolochic acids I/II, benzo[a]pyrene, cisplatin, cyclophosphamide, diethylnitrosamine, 1,2-dimethylhydrazine, dimethylnitrosamine, 2,6-dinitrotoluene, hydroxyurea, melphalan, temozolomide, quinoline, or vinblastine. These 13 chemicals were each tested in two treatment regimens: one 3-day exposure cycle, and three 3-day exposure cycles. Each exposure, blood collection, and liver harvest was accomplished during a standard Monday-Friday workweek. Key findings are that even these well-studied, relatively potent genotoxicants were not active in both tissues and all assays (indeed only cisplatin was clearly positive in all three assays); and whereas the sensitivity of the Pig-a assay clearly benefitted from three versus one treatment cycle, micronucleus assays yielded qualitatively similar results across both study designs. Collectively, these results suggest it is possible to significantly reduce animal and other resource requirements while improving assessments of in vivo genotoxicity potential by simultaneously evaluating three endpoints and two important tissue compartments using fit-for-purpose study designs in conjunction with flow cytometric scoring approaches. Environ. Mol. Mutagen., 60:704-739, 2019. © 2019 Wiley Periodicals, Inc.

Pig-a gene mutation database

Mutations in the X-linked phosphatidylinositol glycan, class A gene (Pig-a) lead to loss of glycosylphosphatidylinositol (GPI) anchors and GPI-anchored proteins from the surface of erythrocytes and other mammalian cells. The Pig-a gene mutation assay quantifies in vivo gene mutation by immunofluorescent labeling and flow cytometry to detect the loss of GPI-anchored proteins on peripheral blood erythrocytes. As part of the regulatory acceptance of the assay, a public database has been created that provides detailed information on Pig-a gene mutation assays conducted in rats and mice. A searchable version of the database is available through a website designed and hosted by the University of Maryland School of Pharmacy. Currently, the database contains only mouse and rat data, but it is anticipated that it will expand to include data from other species, including humans. A major purpose in developing the database was to aid in the preparation of a Retrospective Performance Analysis and Detailed Review Paper required for Organisation for Economic Co-operation and Development Test Guideline acceptance. We anticipate, however, that it also will be useful for accessing and comparing Pig-a data to data from other assays and for conducting quantitative assessments of Pig-a gene mutation responses. Environ. Mol. Mutagen., 60:759-762, 2019. © 2019 Wiley Periodicals, Inc.