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.
Estetrol (medication)
In addition to a single-drug formulation, estetrol is under development in combination with the progestin drospirenone for use as a birth control pill to prevent pregnancy with the tentative brand name Estelle. Drospirenone is also a potent antimineralocorticoid and antiandrogen in addition to progestogen, and in relation to this, is said to have a progesterone-like medication profile. As of April 2018, estetrol/drospirenone are in phase III clinical trials for pregnancy prevention.