Estradiol sulfate
As the sodium salt, sodium estradiol sulfate, E2S is present as a minor constituent (0.9%) of conjugated equine estrogens (CEEs), or Premarin. It effectively functions as a prodrug to estradiol in this preparation, similarly to E1S. E2S is also formed as a metabolite of estradiol, as well as of estrone and E1S. Aside from its presence in CEEs, E2S is not available as a commercial pharmaceutical drug.
Estriol sulfamate
Estriol sulfamate (developmental code name J1034), or estriol 3-"O"-sulfamate, is a synthetic estrogen and estrogen ester which was never marketed. It is the C3 sulfamate ester of estriol. The drug shows substantially improved oral estrogenic potency (vagina, uterus) relative to estriol in rats but without an increase in hepatic estrogenic potency. However, the closely related compound estradiol sulfamate (E2MATE) failed to show estrogenic activity in humans, which is due to the fact that it is additionally a highly potent inhibitor of steroid sulfatase and prevents its own bioactivation into estradiol.