Several clinical trials are ongoing for patients with GBA-associated PD: One trial, PROPEL, studies the effect of PR001, which is a gene-replacement therapy that uses adeno-associated virus 9 (AAV9) to deliver a functional copy of the GBA1 gene to the brain intracisternal (clinicaltrials.gov: NCT04127578). This evidence concerns the gene GBA1 and Parkinson disease.