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Lynch AM, Howe J, Hildebrand D, Harvey JS, Burman M, Harte DSG, Chen L, Kmett C, Shi W, McHugh CF, Patel KK, Junnotula V, Kenny J, Haworth R, Wills JW. N-Nitrosodimethylamine investigations in Muta™Mouse define point-of-departure values and demonstrate less-than-additive somatic mutant frequency accumulations. Mutagenesis 2024; 39:96-118. [PMID: 38183622 DOI: 10.1093/mutage/geae001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 01/05/2024] [Indexed: 01/08/2024] Open
Abstract
The N-nitrosamine, N-nitrosodimethylamine (NDMA), is an environmental mutagen and rodent carcinogen. Small levels of NDMA have been identified as an impurity in some commonly used drugs, resulting in several product recalls. In this study, NDMA was evaluated in an OECD TG-488 compliant Muta™Mouse gene mutation assay (28-day oral dosing across seven daily doses of 0.02-4 mg/kg/day) using an integrated design that assessed mutation at the transgenic lacZ locus in various tissues and at the endogenous Pig-a gene-locus, along with micronucleus frequencies in peripheral blood. Liver pathology was determined together with NDMA exposure in blood and liver. The additivity of mutation induction was assessed by including two acute single-dose treatment groups (i.e. 5 and 10 mg/kg dose on Day 1), which represented the same total dose as two of the repeat dose treatment groups. NDMA did not induce statistically significant increases in mean lacZ mutant frequency (MF) in bone marrow, spleen, bladder, or stomach, nor in peripheral blood (Pig-a mutation or micronucleus induction) when tested up to 4 mg/kg/day. There were dose-dependent increases in mean lacZ MF in the liver, lung, and kidney following 28-day repeat dosing or in the liver and kidney after a single dose (10 mg/kg). No observed genotoxic effect levels (NOGEL) were determined for the positive repeat dose-response relationships. Mutagenicity did not exhibit simple additivity in the liver since there was a reduction in MF following NDMA repeat dosing compared with acute dosing for the same total dose. Benchmark dose modelling was used to estimate point of departure doses for NDMA mutagenicity in Muta™Mouse and rank order target organ tissue sensitivity (liver > kidney or lung). The BMD50 value for liver was 0.32 mg/kg/day following repeat dosing (confidence interval 0.21-0.46 mg/kg/day). In addition, liver toxicity was observed at doses of ≥ 1.1 mg/kg/day NDMA and correlated with systemic and target organ exposure. The integration of these results and their implications for risk assessment are discussed.
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Affiliation(s)
- Anthony M Lynch
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | - Jonathan Howe
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | | | - James S Harvey
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | - Mark Burman
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | - Danielle S G Harte
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | - Liangfu Chen
- DMPK, GSK R&D, Upper Providence, Collegeville, PA, United States
| | - Casey Kmett
- DMPK, GSK R&D, Upper Providence, Collegeville, PA, United States
| | - Wei Shi
- DMPK, GSK R&D, Upper Providence, Collegeville, PA, United States
| | - Charles F McHugh
- DMPK, GSK R&D, Upper Providence, Collegeville, PA, United States
| | - Kinnari K Patel
- BIB, GSK R&D, Upper Providence, Collegeville, PA, United States
| | | | - Julia Kenny
- TPPS, GSK R&D, Stevenage, SG1 2NY, United Kingdom
| | | | - John W Wills
- Genetic Toxicology & Photosafety, GSK R&D, Stevenage, SG1 2NY, United Kingdom
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Dobrovolsky VN, Atiq OT, Heflich RH, Maisha M, McKinzie PB, Pearce MG, Robison TW. Erythrocyte PIG-A mutant frequencies in cancer patients receiving cisplatin. Cancer Med 2024; 13:e6895. [PMID: 38214136 PMCID: PMC10905239 DOI: 10.1002/cam4.6895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/04/2023] [Accepted: 12/19/2023] [Indexed: 01/13/2024] Open
Abstract
BACKGROUND Cisplatin is a primary chemotherapy choice for various solid tumors. DNA damage caused by cisplatin results in apoptosis of tumor cells. Cisplatin-induced DNA damage, however, may also result in mutations in normal cells and the initiation of secondary malignancies. In the current study, we have used the erythrocyte PIG-A assay to evaluate mutagenesis in non-tumor hematopoietic tissue of cancer patients receiving cisplatin chemotherapy. METHODS Twenty-one head and neck cancer patients undergoing treatment with cisplatin were monitored for the presence of PIG-A mutant total erythrocytes and the young erythrocytes, reticulocytes (RETs), in peripheral blood for up to five and a half months from the initiation of the anti-neoplastic chemotherapy. RESULTS PIG-A mutant frequency (MF) in RETs increased at least two-fold in 15 patients at some point of the monitoring, while the frequency of total mutant RBCs increased at least two-fold in 6 patients. A general trend for an increase in the frequency of mutant RETs and total mutant RBCs was observed in 19 and 18 patients, respectively. Only in one patient did both RET and total RBC PIG-A MFs did not increase at any time-point over the monitoring period. CONCLUSION Cisplatin chemotherapy induces moderate increases in the frequency of PIG-A mutant erythrocytes in head and neck cancer patients. Mutagenicity measured with the flow cytometric PIG-A assay may serve as a tool for predicting adverse outcomes of genotoxic antineoplastic therapy.
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Affiliation(s)
- Vasily N. Dobrovolsky
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research (NCTR), US Food and Drug Administration (FDA)JeffersonArkansasUSA
| | - Omar T. Atiq
- University of Arkansas for Medical Sciences (UAMS) Winthrop P. Rockefeller Cancer InstituteLittle RockArkansasUSA
| | - Robert H. Heflich
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research (NCTR), US Food and Drug Administration (FDA)JeffersonArkansasUSA
| | - Mackean Maisha
- Office of Scientific Coordination, NCTR, FDAJeffersonArkansasUSA
| | - Page B. McKinzie
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research (NCTR), US Food and Drug Administration (FDA)JeffersonArkansasUSA
| | - Mason G. Pearce
- Division of Genetic and Molecular ToxicologyNational Center for Toxicological Research (NCTR), US Food and Drug Administration (FDA)JeffersonArkansasUSA
| | - Timothy W. Robison
- Office of New Drugs, OII, DPTII, Center for Drug Evaluation and Research (CDER), US FDASilver SpringMarylandUSA
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Gollapudi BB. Investigations on the genotoxic potential of styrene in Fischer 344 rats using multiple endpoints. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65:67-75. [PMID: 38525651 DOI: 10.1002/em.22590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 03/04/2024] [Indexed: 03/26/2024]
Abstract
Genotoxicity of styrene monomer was evaluated in male Fischer 344 rats using the alkaline comet assay for DNA damage, micronucleus assay for cytogenetic damage and the Pig-a assay for gene mutations. In a dose range finding (DRF) study, styrene was administered by oral gavage in corn oil for 28 consecutive days at 0, 100, 500, and 1000 mg/kg/day. The bioavailability of styrene was confirmed in the DRF by measuring its plasma levels at approximately 7- or 15-min following dosing. The 1000 mg/kg/day group exceeded the maximum tolerated dose based on body weight and organ weight changes and signs of central nervous system depression. Based on these findings, doses of 0, 100, 250, and 500 mg/kg/day (for 28 or 29 days) were selected for the genotoxicity assays. Animals were sacrificed 3-4 h after treatment on Day 28 or 29 for assessing various genotoxicity endpoints. Pig-a mutant frequencies and micronucleus frequencies were determined in peripheral blood erythrocytes. The comet assay was conducted in the glandular stomach, duodenum, liver, lung, and kidney. These studies were conducted in accordance with the relevant OECD test guidelines. Oral administration of styrene did not lead to genotoxicity in any of the investigated endpoints. The adequacy of the experimental conditions was assured by including animals treated by oral gavage with the positive control chemicals ethyl nitrosourea and ethyl methane sulfonate. Results from these studies supplement to the growing body of evidence suggesting the lack of in vivo genotoxic potential for styrene.
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Dobrovolsky VN, Matsuda T, McKinzie P, Miranda J, Revollo JR. Whole-genome high-fidelity sequencing: A novel approach to detecting and characterization of mutagenicity in vivo. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2023; 891:503691. [PMID: 37770148 DOI: 10.1016/j.mrgentox.2023.503691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 08/29/2023] [Accepted: 09/04/2023] [Indexed: 10/03/2023]
Abstract
Direct DNA sequencing can be used for characterizing mutagenicity in simple and complex biological models. Recently we described a method of whole-genome sequencing for detecting mutations in simple models of cultured bacteria, mammalian cells, and nematode. In the current proof-of-concept study, we expand and improve our method for evaluating a more complex mammalian biological model in outbred mice. We detail the method by applying it to a small set of animals treated with a mutagen with known mutagenicity profiles, N-ethyl-N-nitrosourea (ENU), for consistency with the known data. Whole-genome high-fidelity sequencing (HiFi Sequencing) showed frequencies and spectra of background mutations in tissues of untreated mice that were consistent with normal ageing and characterized by spontaneous or enzymatic deamination of 5-methylcytosine. In mice treated with a single 40 mg/kg dose of ENU, the frequency of mutations in the genomic DNA of solid tissues increased up to 7-fold, with the greatest increase observed in the spleen and the smallest increase in the liver. The most common mutations detected in ENU-treated mice were T > A transitions and T > C transversions, consistent with the types of mutations caused by alkylating agents. The data suggest that HiFi Sequencing may be useful for characterizing mutagenicity of novel compounds in various biological models.
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Affiliation(s)
- Vasily N Dobrovolsky
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson AR, USA.
| | - Tomonari Matsuda
- Research Center for Environmental Quality Management, Kyoto University, Otsu, Shiga, Japan
| | - Page McKinzie
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson AR, USA
| | - Jaime Miranda
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson AR, USA
| | - Javier R Revollo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson AR, USA
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Gollapudi BB. Genotoxicity evaluation of orally administered styrene monomer in mice using comet, micronucleus, and Pig-a endpoints. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023. [PMID: 37042435 DOI: 10.1002/em.22540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 04/07/2023] [Indexed: 06/19/2023]
Abstract
Male B6C3F1 mice were administered styrene monomer by oral gavage for 29 consecutive days at dose levels of 0, 75, 150, or 300 mg/kg/day. The highest dose level represented the maximum tolerated dose based on findings in a 28-day dose range-finding study, in which the bioavailability of orally administered styrene was also confirmed. The positive control group received ethyl nitrosourea (ENU; 51.7 mg/kg/day) on Study Days 1-3 and ethyl methanesulfonate (EMS; 150 mg/kg/day) on Study Days 27-29 by oral gavage. Approximately 3 h following the final dose, blood was collected to assess erythrocyte Pig-a mutant and micronucleus frequencies. DNA strand breakage was assessed in glandular stomach, duodenum, kidney, liver, and lung tissues using the alkaline comet assay. The %tail DNA for stomach, liver, lung, and kidney in the comet assay among the styrene-treated groups was neither significantly different from the respective vehicle controls nor was there any dose-related increasing trend in any of the tissues; results for duodenum were interpreted to be inconclusive because of technical issues. The Pig-a and micronucleus frequencies among styrene-treated groups also did not show significant increases relative to the vehicle controls and there was also no evidence for a dose-related increasing trend. Thus, orally administered styrene did not induce DNA damage, mutagenesis, or clastogenesis/aneugenesis in these Organization of Economic Co-operation and Development test guideline-compliant genotoxicity studies. Data from these studies can contribute to the overall assessment of genotoxic hazard and risk posed to humans potentially exposed to styrene.
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Zeiger E. Determination of a positive response in the Ames Salmonella mutagenicity assay. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:250-258. [PMID: 36916210 DOI: 10.1002/em.22538] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/09/2023] [Accepted: 03/11/2023] [Indexed: 05/03/2023]
Abstract
Genetic toxicology tests are used to categorize substances as genotoxic and potentially carcinogenic. In general, test results are designated as mutagenic, not mutagenic, or inconclusive and, depending on its potential use and applicable regulations, a mutagenic result can restrict or remove a substance from further development, or assign limits to its use. In these tests, mutation responses form a continuum without a clear delineation between an increase over the background, untreated, mutant frequency and a frequency that would define the test substance as a mutagen and a potential carcinogenic hazard. This situation is illustrated using the Salmonella mutagenicity (Ames) test which is the initial, and often only, test used to characterize substances as mutagenic or nonmutagenic. It has its widest use by industry and regulatory authorities to identify potential carcinogens among chemicals in development. The OECD Test Guideline No. 471 has been adopted by regulatory agencies internationally, and describes the minimum requirements for a negative response, but does not provide a specific approach for evaluating the test data. The most widely used criterion for making yes-or-no mutagenicity decisions is a 2- or 3-fold increase over the background (solvent) mutant frequency. Other approaches rely on formal statistics and/or expert judgment. These approaches and recently proposed modifications are evaluated here. Recommendations are made that are in conformity with the OECD guideline and are based on biological relevance and the biology of the mutagenic response rather than on arbitrary decision points (e.g., ≥2-fold increase or p ≤ .05).
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Affiliation(s)
- Errol Zeiger
- Errol Zeiger Consulting, Chapel Hill, North Carolina, USA
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A weight of evidence review of the genotoxicity of titanium dioxide (TiO2). Regul Toxicol Pharmacol 2022; 136:105263. [DOI: 10.1016/j.yrtph.2022.105263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/26/2022] [Accepted: 09/10/2022] [Indexed: 11/06/2022]
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Waters MD, Warren S, Hughes C, Lewis P, Zhang F. Human genetic risk of treatment with antiviral nucleoside analog drugs that induce lethal mutagenesis: The special case of molnupiravir. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2022; 63:37-63. [PMID: 35023215 DOI: 10.1002/em.22471] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/28/2021] [Accepted: 01/08/2022] [Indexed: 06/14/2023]
Abstract
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.
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Affiliation(s)
- Michael D Waters
- Michael Waters Consulting USA, Hillsborough, North Carolina, USA
| | | | - Claude Hughes
- Duke University Medical Center, Durham, North Carolina, USA
| | | | - Fengyu Zhang
- Global Clinical and Translational Research Institute, Bethesda, Maryland, USA
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