A statistically significant (P = 0.032; multiplicity adjusted P = 0.040) increasing trend in tumor incidence through 300 mg/kg/d was observed for hemangiosarcoma in the spleen (12%) in female mice. Step-down analysis results through 100 mg/kg/d were not statistically significant (P = 0.470). The marginally significant P-value through 300 mg/kg/d was attributed to the random occurrence of an unusually low concurrent control rate (0%) (U.S. Food and Drug Administration (FDA) Center for Drug Evaluation and Research (CDER). Guidance for Industry 2001) and was not test article related given that the incidence was well within the historical control range for female CByB6F1/Tg rasH2 mice from the test facility (0% to 16%) and in the published literature (0% to 16% Paranjpe et al. 2013, 2019; 0% to 26% Nambiar et al. 2012).

MOV, molnupiravir; NMU, N-Nitroso-N-methylurea; M, male; F, female.

P ≤ 0.001,

P ≤ 0.01,

P ≤ 0.05 (one-sided P-value from upper-tail Fisher exact test).