The use of hormone replacement therapy for bone loss prevention in post-menopausal women is well precedented. The normal protocol calls for estrogen supplementation using such formulations containing estrone, estriol, ethynyl estradiol or conjugated estrogens isolated from natural sources (Premarin from Wyeth-Ayerst). In some patients, therapy may be contraindicated due to the proliferative effects unopposed estrogens (estrogens not given in combination with progestins) have on uterine tissue. This proliferation is associated with increased risk for endometriosis and/or endometrial cancer. The effects of unopposed estrogens on breast tissue is less clear, but is of some concern. The need for estrogens which can maintain the bone sparing effect while minimizing the proliferative effects in the uterus and breast is evident. Certain nonsteroidal antiestrogens have been shown to maintain bone mass in the ovariectomized rat model as well as in human clinical trials. Tamoxifen, for example, is a useful palliative for the treatment of breast cancer. It has been demonstrated to exert an estrogen agonist like effect on the bone, in humans. However, it is also a partial agonist in the uterus and this is cause for some concern. Raloxifene, a benzothiophene antiestrogen, has been shown to stimulate uterine growth in the ovariectomized rat to a lesser extent than Tamoxifen while maintaining the ability to spare bone. A suitable review of tissue selective estrogens is: Tissue -Selective Actions Of Estrogen Analogs, Bone Vol. 17, No. 4, October 1995, 181S-190S.
The use of indoles as estrogen antagonists has been reported by Von Angerer, Chemical Abstracts, Vol. 99, No. 7 (1983), Abstract No. 53886u. Also, see, J.Med.Chem. 1990, 33, 2635-2640; J.Med.Chem. 1987, 30, 131-136. Also see Ger. Offen., DE 3821148 A1 891228. Additionally, see WO, A, 93 23374 (Otsuka Pharmaceutical Factory, Inc.). Von Angerer's work is limited to aliphatic chains linked to the indole nitrogen and then linked to the basic amine (or amide) or, benzyl groups not possessing the basic amine. The world patent from Otsuka (Japanese) consists of compounds related to the present invention except R.sub.3 (as shown in formula I) is defined as --SR where R is alkyl. Additionally, there are no chains from the indole nitrogen in their patent with the same structure as the ones given in the present invention, either by claim or example. A related patent WO A 93 10741 describes 5-Hydroxyindoles. WO A 95 17383 (Kar Bio AB) describes aliphatic chain compounds.