ERT was developed in 1964 by Christian de Duve and Roscoe Brady.[1][3] Leading work was done on this subject at the Department of Physiology at the University of Alberta by Mark J. Poznansky and Damyanti Bhardwaj, where a model for enzyme therapy was developed using rats.[4] ERT was not used in clinical practice until 1991, after the FDA gave orphan drug approval for the treatment of Gaucher disease with Alglucerase.[1] ERTs were initially manufactured by isolating the therapeutic enzyme from human placenta.[1] The FDA has now approved ERTs that are derived from other human cells, animal cells (i.e. Chinese hamster ovary cells, or CHO cells), and plant cells.[1]