In an open-label, non-randomized, non-controlled clinical trial with 17 PD patients, ambroxol crossed the BBB and bound to GCase and increased GCase protein levels and α-synuclein concentrations in the cerebrospinal fluid in patients both with and without GBA mutations, and it induced no serious adverse effects (Mullin et al., 2020). The gene discussed is SNCA; the disease is Parkinson disease.