This study was conducted as part of the International Life Sciences Institute (ILSI) program to evaluate the carcinogenic potential of
clofibrate, a nongenotoxic,
peroxisome proliferator-activated receptor (
PPAR) alpha agonist following
oral administration to Tg.AC (transgenic) and wild-type FVB (nontransgenic) mice for a minimum for 6 months.
Clofibrate was well tolerated at doses up to 500 (males) and 650 (females) mg/kg/day.
Oral administration of
clofibrate to Tg.AC or FVB (wild-type) male and female mice for 6 months did not result in the increased formation of neoplastic lesions. Epithelial
hyperplasia in the urinary bladder (Tg.AC and FVB) and prostate gland (Tg.AC only), and interstitial-cell
hyperplasia in the testes (Tg.AC) were noted at 500 mg/kg/day. Non-neoplastic nonproliferative findings included hepatic
hypertrophy and hematopoietic changes (myeloid
hyperplasia, myelodysplasia, lymphoid depletion, and erythropoiesis) in Tg.AC and FVB mice of both sexes; reproductive (cystic degeneration and dilatation, hypospermia,
spermatocele, dilated inspissated
protein) and urogenital (tubular-cell
hypertrophy, degenerative/regenerative nephropathy,
necrosis/
fibrosis) changes in Tg.AC and FVB male mice; congestion in the lung in male Tg.AC mice; gall bladder dilatation in female Tg.AC mice; and adrenal (intracellular lipofuscinosis and
atrophy) and heart (eosinophillic myofibers) findings in Tg.AC mice of both sexes and in female FVB mice. The results of this study indicate that the
clofibrate is not carcinogenic when administered to Tg.AC mice by oral gavage for 6 months at doses up to 500 (males) and 650 (females) mg/kg/day, which did produce liver
hypertrophy.