Pimecrolimus is a semi-synthetic, macrocyclic lactone derived from ascomycin by activation of the 32-hydroxy group with a triflate ester, and nucleophilic substitution with chloride under phase transfer conditions to provide the chloro analogue. Pimecrolimus has been targeted for treatment of inflammatory skin disorders. Like all tacrolimus analogues, pimecrolimus binds to receptor protein, FKBP12. The complex then binds to mTOR preventing it from interacting with target proteins. Pimecrolimus is extensively cited in the literature with over 2,000 citations.