Fareston (Page 4 of 5)


13.1 Carcinogenesis, Mutagenesis, and Impairment of Fertility

Conventional carcinogenesis studies in rats at doses of 0.12 to 12 mg/kg/day (approximately 1/50 to 2 times the daily maximum recommended human dose of 60 mg, on a mg/m2 basis) for up to 2 years did not show evidence of carcinogenicity. Studies in mice at doses of 1.0 to 30.0 mg/kg/day (approximately 1/15 to 2 times the daily maximum recommended human dose of 60 mg, on a mg/m2 basis) for up to 2 years revealed increased incidence of ovarian and testicular tumors and increased incidence of osteoma and osteosarcoma. The significance of the mouse findings is uncertain because of the different role of estrogens in mice and the estrogenic effect of toremifene in mice. An increased incidence of ovarian and testicular tumors in mice has also been observed with other human estrogen agonists/antagonists that have primarily estrogenic activity in mice. Endometrial hyperplasia of the uterus was observed in monkeys following 52 weeks of treatment at ≥1 mg/kg and in dogs following 16 weeks of treatment at ≥3 mg/kg with toremifene (approximately 1/3 and 1.4 times, respectively, the daily maximum recommended human dose of 60 mg, on a mg/m2 basis).

Toremifene has not been shown to be mutagenic in in vitro tests (Ames and E. coli bacterial tests). Toremifene is clastogenic in vitro (chromosomal aberrations and micronuclei formation in human lymphoblastoid MCL-5 cells) and in vivo (chromosomal aberrations in rat hepatocytes).

Toremifene produced impairment of fertility and conception in male and female rats at doses ≥25.0 and 0.14 mg/kg/day, respectively (approximately 4 times and 1/50 the daily maximum recommended human dose of 60 mg, on a mg/m2 basis). At these doses, sperm counts, fertility index, and conception rate were reduced in males with atrophy of seminal vesicles and prostate. In females, fertility and reproductive indices were markedly reduced with increased pre- and post-implantation loss. In addition, offspring of treated rats exhibited depressed reproductive indices. Toremifene produced ovarian atrophy in dogs administered doses ≥3 mg/kg/day (approximately 1.5 times the daily maximum recommended human dose of 60 mg, on a mg/m2 basis) for 16 weeks. Cystic ovaries and reduction in endometrial stromal cellularity were observed in monkeys at doses ≥1 mg/kg/day (about 1/3 the daily maximum recommended human dose of 60 mg, on a mg/m2 basis) for 52 weeks.


Three prospective, randomized, controlled clinical studies (North American, Eastern European, and Nordic) were conducted to evaluate the efficacy of FARESTON for the treatment of breast cancer in postmenopausal women. The patients were randomized to parallel groups receiving FARESTON 60 mg (FAR60) or tamoxifen 20 mg (TAM20) in the North American Study or tamoxifen 40 mg (TAM40) in the Eastern European and Nordic studies. The North American and Eastern European studies also included high-dose toremifene arms of 200 and 240 mg daily, respectively. The studies included postmenopausal patients with estrogen-receptor (ER) positive or estrogen-receptor (ER) unknown metastatic breast cancer. The patients had at least one measurable or evaluable lesion. The primary efficacy variables were response rate (RR) and time to progression (TTP). Survival (S) was also determined. Ninety-five percent confidence intervals (95% CI) were calculated for the difference in RR between FAR60 and TAM groups and the hazard ratio (relative risk for an unfavorable event, such as disease progression or death) between TAM and FAR60 for TTP and S.

Two of the 3 studies showed similar results for all effectiveness endpoints. However, the Nordic Study showed a longer time to progression for tamoxifen (see table).

Clinical Studies
1 CR = complete response; 2 PR = partial response; 3 RR = response rate; 4 CI = confidence interval
Study North American Eastern European Nordic
Treatment Group FAR60 TAM20 FAR60 TAM40 FAR60 TAM40
No. Patients 221 215 157 149 214 201
CR1 + PR2 14 + 33 11 + 30 7 + 25 3 + 28 19 + 48 19 + 56
RR3 (CR + PR)% 21.3 19.1 20.4 20.8 31.3 37.3
Difference in RR 2.2 -0.4 -6.0
95% CI4 for Difference in RR -5.8 to 10.2 -9.5 to 8.6 -15.1 to 3.1
Time to Progression (TTP)
Median TTP (mo.) 5.6 5.8 4.9 5.0 7.3 10.2
Hazard Ratio (TAM/FAR) 1.01 1.02 0.80
95% CI4 for Hazard Ratio (%) 0.81 to 1.26 0.79 to 1.31 0.64 to 1.00
Survival (S)
Median S (mo.) 33.6 34.0 25.4 23.4 33.0 38.7
Hazard Ratio (TAM/FAR) 0.94 0.96 0.94
95% CI4 for Hazard Ratio (%) 0.74 to 1.24 0.72 to 1.28 0.73 to 1.22

The high-dose groups, toremifene 200 mg daily in the North American Study and 240 mg daily in the Eastern European Study, were not superior to the lower toremifene dose groups, with response rates of 22.6% and 28.7%, median times to progression of 5.6 and 6.1 months, and median survivals of 30.1 and 23.8 months, respectively. The median treatment duration in the three pivotal studies was 5 months (range 4.2-6.3 months).


FARESTON Tablets, containing toremifene citrate in an amount equivalent to 60 mg of toremifene, are round, convex, unscored, uncoated, and white, or almost white.

FARESTON Tablets are identified with TO 60 embossed on one side.

FARESTON Tablets are available as:
NDC 42747-327-30 bottles of 30
NDC 42747-327-72 samples of 7

Store at 25°C (77°F).
Excursions permitted to 15-30°C (59-86°F)
[See USP Controlled Room Temperature.]
Protect from heat and light.

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