Lilopristone (ZK 98.734) has a high affinity for progesterone receptors. The progesterone antagonistic effects of ZK 98.734 could be a result of the decrease in progesterone synthesis by the corpus luteum and/or placenta in addition to the interference with the progesterone binding to its cellular receptors in the target organ. ZK 98.734 has potential for fertility regulation. It is a very potent abortifacient in the common marmosets. Lilopristone could significantly suppress the proliferation of ectopic stromal cells in a time- and dose-dependent manner in vitro. The action mechanisms may be associated with the suppression of expression of NF-kappaB P65 mRNA and NF-kappaB P65.

Sufugolix (TAK-013 or 5-(N-benzyl-N-methylaminomethyl)-1-(2,6-difluorobenzyl)-6-[4-(3-methoxyureido)phenyl]-3-phenylthieno[2,3-d]pyrimidine-2,4(1H,3H)-dione) is a highly potent and orally active non-peptide antagonist of luteinizing hormone-releasing hormone (LHRH) receptor. Sufugolix by oral administration suppresses a pituitary-ovarian axis continuously and reversibly in cynomolgus monkeys. Takeda studied Sufugolix in the trials for the treatment of endometriosis and uterine leiomyoma however development was discontinued.

Topilutamide is a non-steroidal anti-androgen. Topilutamide downregulated androgen receptor expression by 40% at 3 uM and up to 95% at 10 uM in LNCaP Cells After 48-h drug incubation. While highly hydrophobic and hydrolytically degradable, it is systemically nonresorbable. In animals, fluridil demonstrated high local and general tolerance. After 3 months of topical application of topilutamide, the average anagen percentage did not change in placebo subjects but increased in topilutamide subjects (male with androgenetic alopecia) from 76% to 85%, and at 9 months to 87%. In former placebo subjects, topilutamide increased the anagen percentage after 6 months from 76% to 85%. Sexual functions, libido, hematology, and blood chemistry values were normal.

Turosteride [FCE 26073] is a selective 5α-reductase inhibitor being developed by Pharmacia Corporation. Turosteride inhibits human and rat prostatic 5 alpha-reductases with IC50 values of 55 and 53 nM, respectively. It was in phase II clinical trials in Italy for the treatment of benign prostatic hyperplasia.

Asoprisnil (J867) is a novel selective steroid receptor modulator that shows unique pharmacodynamic effects in animal models and humans. Asoprisnil, its major metabolite J912, and other structurally related compounds represent a new class of progesterone receptor (PR) ligands that exhibit partial agonist and antagonist activities in vivo. Asoprisnil demonstrates a high degree of receptor and tissue selectivity, with a high-binding affinity for PR, moderate affinity for glucocorticoid receptor (GR), low affinity for androgen receptor (AR), and no binding affinity for estrogen or mineralocorticoid receptors. This compound was recently in clinical trials for the treatment of uterine fibroids and endometriosis, but those studies were discontinued.

IZONSTERIDE, a benzoquinolinone, is a selective inhibitor of the 5-alpha reductase, with antagonistic effect on both the type I (liver, skin, hair follicles) and type II (prostate) isoforms of the enzyme. It is a competitive inhibitor of type I 5-alpha reductase and a non-competitive inhibitor of type II 5-alpha reductase. It was under development for the treatment of prostatic cancer.

Bifluranol (brand name Prostarex), a fluorinated bibenzyl anti-androgen was developed as a nonsteroidal estrogen and was studied for the treatment of benign prostatic hyperplasia. Besides, was shown that bifluranol inhibited 17 alpha-hydroxylase/C17-C20 lyase.

Retosiban is a small molecule oxytocin receptor antagonist that is under evaluation for treatment of premature labor. Retosiban was found to be safe in healthy non-pregnant volunteers in phase I studies. Intravenous retosiban also had good safety and tolerability in phase II studies and was suggested to prolong pregnancies in women with preterm labor. Phase III studies have been conducted to demonstrate the efficacy of retosiban to prolong pregnancy and improve neonatal outcomes, and compare effects with a similar drug atosiban, but these studies were terminated in 2018 (not due to adverse events).

Topterone is an anti-androgen agent. Topterone inhibited stimulation of flank organ development of castrated immature male hamsters by both testosterone and dihydrotestosterone. Topical application of topterone on the flank organs of the male hamster did not cause any significant effect on testosterone metabolism of this tissue. In addition, there was no decrease in the lipogenic capacity of the flank organ. Topterone exerts its antiandrogenic action by binding with the cytosolic androgen receptor(s) in the flank organ thus inhibiting the action of dihydrotestosterone. Systemic administration demonstrated that topterone was both antiandrogenic and progestational. Topterone produced a mean inhibition of sebum excretion of 20% when it was applied topically for four weeks to the forehead skin of patients with acne.