Hisada S, Tsubota K, Inoue K, Yamada H, Ikeda T, Sistare FD. Survey of tumorigenic sensitivity in 6-month rasH2-Tg mice studies compared with 2-year rodent assays.
J Toxicol Pathol 2022;
35:53-73. [PMID:
35221496 PMCID:
PMC8828610 DOI:
10.1293/tox.2021-0031]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 10/07/2021] [Indexed: 12/04/2022] Open
Abstract
The pharmacokinetic endpoint of a 25-fold increase in human exposure is one of the
specified criteria for high-dose selection for 2-year carcinogenicity studies in rodents
according to ICH S1C(R2). However, this criterion is not universally accepted for 6-month
carcinogenicity tests in rasH2-Tg mice. To evaluate an appropriate multiple for rasH2-Tg
mice, we evaluated data for 53 compounds across five categories of rasH2-Tg mouse-positive
[(1) genotoxic and (2) non-genotoxic] carcinogens and rasH2-Tg mouse-negative [(3)
non-genotoxic carcinogens with clear or uncertain human relevance; (4) non-genotoxic
rodent-specific carcinogens; and (5) non-carcinogens], and surveyed their tumorigenic
activities and high doses in rasH2-Tg mice and 2-year rodent models. Our survey indicated
that area under the curve (AUC) margins (AMs) or body surface area-adjusted dose ratios
(DRs) of tumorigenesis in rasH2-Tg mice to the maximum recommended human dose (MRHD) were
0.05- to 5.2-fold in 6 category (1) compounds with small differences between models and
0.2- to 47-fold in 7 category (2) including three 2-year rat study-negative compounds.
Among all 53 compounds, including 40 compounds of the rasH2-Tg mouse-negative category
(3), (4), and (5), no histopathologic risk factors for rodent neoplasia were induced only
at doses above 50-fold AM or DR in rasH2-Tg mice except for two compounds, which induced
hyperplasia and had no relationship with the tumors observed in the rasH2-Tg mouse or
2-year rodent studies. From the results of these surveys, we confirmed that exceeding a
high dose level of 50-fold AM in rasH2-Tg mouse carcinogenicity studies does not appear to
be of value.
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