Exos (active agent – exemestane) is a very strong and very potent steroidal aromatase inhibitor of the suicidal type.  Exos is extremely effective at 25mg daily for the reduction of serum circulating estrogen levels by 85%.

Aromatase inhibitors are the compounds that serve to reduce estradiol levels in blood by eliminating the production of estradiol through binding to and disabling the aromatase enzyme, which is responsible for the conversion (or aromatization) of androgens into estradiol. Suicidal aromatase inhibitors serve to permanently inhibit and disable the aromatase enzyme to which it is bound to. This renders the enzyme inactive forever. The body will eventually manufacture more aromatase enzymes, but the currently-bound enzymes are bound indefinitely, eliminating any risk for estrogen rebound. This is the main difference compared alongside two other major aromatase inhibitors: anastrozole and letrozole, which are non-suicidal aromatase inhibitors that are only bound to the aromatase enzyme for limited time periods. If a non-suicidal aromatase inhibitor is halted too abruptly, the circulating inhibited aromatase enzymes that have not been metabolized out of the body will then become free again, and begin aromatizing androgens into estrogens at an often rapid rate. This is not the case with Exos.