13 NONCLINICAL TOXICOLOGY
13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
Carcinogenicity studies with conjugated estrogens/bazedoxifene have not been conducted.
Long-term continuous administration of natural and synthetic estrogens in certain animal species increases the frequency of carcinomas of the breast, uterus, cervix, vagina, testis, and liver.
In 6-month oral gavage carcinogenicity studies of bazedoxifene in transgenic Tg.RasH2 mice, there was a drug-related increased incidence of benign, ovarian granulosa-cell tumors in female mice given 150 or 500 mg/kg/day. In a two-year dietary carcinogenicity study of bazedoxifene in rats (administered at 0.003%, 0.01%, 0.03%, or 0.1%) a drug-related marked increased incidence of benign, ovarian granulosa-cell tumors was observed in female rats at concentrations of 0.03% and 0.1%. Systemic exposure (AUC) of bazedoxifene in these groups was 3 and 8 times that observed in postmenopausal women administered 20 mg/day. In male rats, drug-related renal tumors (adenomas and carcinomas), in the presence of renal toxicity, were observed at all doses tested, which corresponded to exposure ratios of 0.06 to 5 times the clinical AUC at a dose of 20 mg.
Mutagenicity studies with conjugated estrogens/bazedoxifene have not been conducted.
Bazedoxifene was not genotoxic or mutagenic in a battery of tests, including in vitro bacterial reverse mutation assay, in vitro mammalian cell forward mutation assay at the thymidine kinase (TK+/-) locus in L5178Y mouse lymphoma cells, in vitro chromosome aberration assay in Chinese hamster ovary (CHO) cells, and in vivo mouse micronucleus assay.
Impairment of Fertility
Impairment of fertility studies with conjugated estrogens/bazedoxifene have not been conducted.
Female rats were administered daily dosages of 0.3 to 30 mg/kg bazedoxifene (0.03 to 10 times human AUC at the 20 mg dose) prior to and during mating with untreated males. Estrous cycles and fertility were adversely affected in all bazedoxifene-treated female groups.
13.2 Animal Toxicology and/or Pharmacology
In a 12-month study in ovariectomized rats, co-administration of conjugated estrogens (2.5 mg/kg/day) and bazedoxifene (0.1, 0.3, or 1 mg/kg/day) prevented the loss of bone mass at the spine, femur, and tibia with concomitant maintenance of biomechanical strength parameters.