GBA1 and Parkinson disease: Other researchers supporting the gain-of-function explanation have used other animal models [3]—notably the fruit fly Drosophila [8,9]—to explore the use of pharmacological chaperones (PCs), mainly Ambroxol (an over-the-counter (OTC) cough medicine which has been shown to be a glucocerebrosidase-specific PC [10,11]), to treat both GBA1-PD and idiopathic PD (assuming that misfolding could also occur in the wild-type glucocerebrosidase enzyme) [10,11].