regonyl regonyl regonyl (developmental code name tx-380), also known as 17α-ethynyl-5α-androst-2-en-17β-ol 17β-acetate, is a steroidal drug described as an antiprogestogen and "antiprolactin" (prolactin inhibitor). it was studied for lactation inhibition in bitches. it has minimal to no androgenic, estrogenic, or progestogenic activity but is said to strongly inhibit the hypothalamic–pituitary–gonadal axis at central and peripheral levels and to markedly oppose the action of progesterone. however, the antiprogestogenic effects of regonyl do not appear to be due to direct interaction with the progesterone receptor. the actions of regonyl result in estrus cycle disturbances and impaired ovulation. regonyl was proposed for use in humans, for instance in the treatment of gynecological disorders like endometriosis and benign breast disease, and in hormonal contraception. regonylclinical dataother namestx-380; nsc-69588; 17α-ethynyl-5α-androst-2-en-17β-ol 17β-acetate; 17β-acetoxy-5α,17α-pregn-2-en-20-yneidentifiers iupac name phenanthren-17-yl] acetate cas number124-85-6pubchem cid159358chemspider140149uniicby5520366keggc15186chebichebi:79703comptox dashboard (epa)dtxsid20924673 chemical and physical dataformulac23h32o2molar mass340.507 g·mol−13d model (jsmol)interactive image smiles cc(=o)o1(cc21(cc32cc43(cc=cc4)c)c)c#c inchi inchi=1s/c23h32o2/c1-5-23(25-16(2)24)15-12-20-18-10-9-17-8-6-7-13-21(17,3)19(18)11-14-22(20,23)4/h1,6-7,17-20h,8-15h2,2-4h3/t17-,18-,19+,20+,21+,22+,23+/m1/s1key:sqrbbvvzrkzepf-ownqeuamsa-n