Animal experiment:

Rats: Rats are treated with daily dosing with Fadrozole hydrochloride in purified water by gavage for 2 years. There are 60 rats in each of four groups given 0, 0.05, 0.25 or 1.25 mg/kg daily. Control rats receive only water. Clinical signs are recorded weekly and the animals are examined for palpable masses every 4 weeks for the first 9 months, then every 2 weeks for the remainder of the study[2]. Mice: Fadrozole hydrochloride is administered in the form of sub-dermal long-term release pellets (20 mg/wt kg, in three-week-release pellets), starting 1 week prior to the infection, using a 10-gauge needle. Three pellets are administrated during the study. Placebo pellets are administered to another group of infected mice, in the same fashion as the inhibitor. After 1 week, mice are infected and killed 8 weeks later[3].

Fadrozole is a non-steroidal aromatase inhibitor (IC50s = 5 and 1.4 nM for human placental and rat ovarian microsomal aromatase, respectively). It selectively inhibits estrogen over progesterone production induced by luteinizing hormone (LH) in hamster ovarian tissue as well as corticosterone and aldosterone production induced by adrenocorticotropic hormone in rat adrenal tissue (IC50s = 0.03, 160, 100, and 1 μM, respectively). It also decreases ovarian estrogen levels in rats when administered at a dose of 0.26 mg/kg. Fadrozole inhibits conversion of cholesterol to 27-hydroxycholesterol by the cytochrome P450 (CYP) isomer 27A1 (Ki = 4.6 μM). It inhibits growth of androstenedione-stimulated mammary D2 cells implanted into thoracic mammary fat pads of mice by 95% when administered at a dose of 0.5 mg per animal per day.

References:
[1]. Bhatnagar, A.S., H?usler, A., Schieweck, K., et al. Highly selective inhibition of estrogen biosynthesis by CGS 20267, a new non-steroidal aromatase inhibitor J. Steroid Biochem. Mol. Biol. 37(6), 1021-1027 (1990).
[2]. Steele, R.E., Mellor, L.B., Sawyer, W.K., et al. In vitro and in vivo studies demonstrating potent and selective estrogen inhibition with the nonsteroidal aromatase inhibitor CGS 16949A Steroids 50(1-3), 147-161 (1987).
[3]. Mast, N., Lin, J.B., and Pikuleva, I.A. Marketed drugs can inhibit cytochrome P450 27A1, a potential new target for breast cancer adjuvant therapy Mol. Pharmacol. 88(3), 428-436 (2015).
[4]. Tekmal, R.R., and Durgam, V.R. A novel in vitro and in vivo breast cancer model for testing inhibitors of estrogen biosynthesis and its action using mammary tumor cells with an activated int-5/aromatase gene Cancer Lett. 118(1), 21-28 (1997).