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. 2022 Aug;41(4):276–290. doi: 10.1177/10915818221095489

Table 4.

Group Incidences and Severities of Nirmatrelvir-Related Microscopic Findings in a 2-Week Rat Toxicity Study.

Male Female
Dose (mg/kg) (q.d.) Dose (mg/kg) (q.d.)
Study phase Tissue Findings 0 0a 60 200 1,000 0 0a 60 200 1,000
Dosing Liver Hypertrophy, hepatocyte; periportal 0/10 0/10 0/10 0/10 6/10b 0/10 0/10 0/10 3/10b 10/10b
Minimal (Grade 1) 0/10 0/10 0/10 0/10 1/10b 0/10 0/10 0/10 3/10# 2/10#
Mild (Grade 2) 0/10 0/10 0/10 0/10 5/10b 0/10 0/10 0/10 0/10 8/10b
Vacuolation, hepatocyte; periportal 0/10 0/10 0/10 0/10 0/10 4/10 5/10 3/10 5/10 10/10
Minimal (Grade 1) 0/10 0/10 0/10 0/10 0/10 4/10 5/10 3/10 5/10 6/10
Mild (Grade 2) 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 0/10 4/10b
Thyroid gland Hypertrophy, follicular cell 0/10 0/10 0/10 0/10 8/10b 0/10 0/10 0/10 0/10 8/10b
Minimal (Grade 1) 0/10 0/10 0/10 0/10 6/10b 0/10 0/10 0/10 0/10 6/10b
Mild (Grade 2) 0/10 0/10 0/10 0/10 2/10b 0/10 0/10 0/10 0/10 2/10b
Pituitary gland Vacuolation, endocrine cells, pars distalis 0/10 ND ND ND 0/10 0/10 ND ND ND 0/10
Minimal (Grade 1) 0/10 ND ND ND 0/10 0/10 ND ND ND 0/10
Mild (Grade 2) 0/10 ND ND ND 0/10 0/10 ND ND ND 0/10
Recovery Liver Hypertrophy, hepatocyte; periportal 0/5 0/5 ND 0/5 0/5 0/5 0/5 ND 0/5 0/5
Minimal (Grade 1) 0/5 0/5 ND 0/5 0/5 0/5 0/5 ND 0/5 0/5
Vacuolation, hepatocyte; periportal 0/5 0/5 ND 0/5 0/5 4/5 2/5 ND 4/5 4/5
Minimal (Grade 1) 0/5 0/5 ND 0/5 0/5 4/5 2/5 ND 4/5 4/5
Thyroid gland Hypertrophy, follicular cell 0/5 0/5 ND ND 0/5 0/5 0/5 ND ND 0/5
Minimal (Grade 1) 0/5 0/5 ND ND 0/5 0/5 0/5 ND ND 0/5
Pituitary gland Vacuolation, endocrine cells, pars distalis ND ND ND ND ND ND ND ND ND ND
Minimal (Grade 1) ND ND ND ND ND ND ND ND ND ND

aDenotes MTBE control.

bDenotes nirmatrelvir-related finding.

Values represent the number of animals with findings compared with the total number of animals per group. ND, not determined.