The beneficial effects of an oral administration of ADLL were reflected in three—therapy-responsive—outcome measures: (1) a marked decline in the subjectively assessed clinical severity of the RBD phenotype (disappearance of aggressive dream content, reduction of dream enactment); (2) a stabilization or reversal of the slow, progressive decline of specific striatal DAT-SPECT binding ratios; and (3) a stabilization or reversal of the expression of the PDRP, an indicator of the progressive metabolic impairment in the CNS of iRBD and PD—as measured by FDG-PET. This evidence concerns the gene SLC6A3 and Parkinson disease.