A case report published in Nature Communications suggests that the peptide derivative acetyl-DL-leucine (ADLL) may modify the progression of prodromal Parkinson's disease. In two patients with isolated REM sleep behavior disorder (iRBD), long-term treatment with ADLL not only reduced sleep symptoms but also appeared to reverse the loss of dopamine transporter binding in the brain. These findings indicate that ADLL could potentially slow or stabilize neurodegeneration associated with Parkinson's.