Molecular properties and preclinical pharmacology of JNJ-1250132, a steroidal progesterone receptor modulator that inhibits binding of the receptor to DNA in vitro

Progesterone receptor modulators have diverse potential therapeutic uses, including the treatment of endometriosis, uterine fibroids and breast cancer. Here we describe the molecular properties and preclinical pharmacology of a new steroidal progestin antagonist, JNJ-1250132. The compound is a high affinity ligand for the progesterone receptor, possessing cross-reactivity with other steroid receptors comparable to that of steroidal antagonists such as mifepristone. It inhibits progestin-inducible alkaline phosphatase gene expression in T47D human breast cancer cells, and also inhibits their in vitro proliferation. It inhibits gestation in rats and progesterone-dependent endometrial transformation in rabbits with efficacies comparable to mifepristone. Like mifepristone, it is a glucocorticoid antagonist in vivo. In cell-free DNA binding assays, the compound inhibits binding of the human progesterone receptor to a progesterone response element, and thus is similar to onapristone in this regard. In contrast, as judged by proteolytic analysis, JNJ-1250132 induces a receptor conformation more similar to that induced by mifepristone, which promotes receptor binding to DNA. Therefore, JNJ-1250132 has unique effects on the progesterone receptor that may translate into a novel clinical profile.