PEP is an estradiol ester in the form of a polymer and is an extremely long-lasting prodrug of estradiol.
As such, it is an estrogen, or an agonist of the estrogen receptors.
PEP has antigonadotropic and functional antiandrogenic effects due to its estrogenic activity.
A single repeat unit of PEP, corresponding to estradiol phosphate (minus OH₂), is of about 23% higher molecular weight than estradiol due to the presence of its C17β phosphate ester.
Because PEP is a prodrug of estradiol, it is considered to be a natural and bioidentical form of estrogen.

PEP is a strong inhibitor of several enzymes, including acid phosphatase, alkaline phosphatase, and hyaluronidase, in vitro.
In light of the fact that phosphatases, which cleave PEP into estradiol and phosphoric acid, are present in most tissues in the body, it has been said that the long elimination half-life and slow release of PEP are somewhat surprising.
It is thought that PEP may inhibit its own metabolism.
PEP is an estradiol ester in the form of a polymer and is an extremely long-lasting prodrug of estradiol. As such, it is an estrogen, or an agonist of the estrogen receptors. PEP has antigonadotropic and functional antiandrogenic effects due to its estrogenic activity. A single repeat unit of PEP, corresponding to estradiol phosphate (minus OH₂), is of about 23% higher molecular weight than estradiol due to the presence of its C17β phosphate ester. Because PEP is a prodrug of estradiol, it is considered to be a natural and bioidentical form of estrogen.
PEP is a strong inhibitor of several enzymes, including acid phosphatase, alkaline phosphatase, and hyaluronidase, in vitro. In light of the fact that phosphatases, which cleave PEP into estradiol and phosphoric acid, are present in most tissues in the body, it has been said that the long elimination half-life and slow release of PEP are somewhat surprising. It is thought that PEP may inhibit its own metabolism.
Polyestradiol phosphate