Author Response: Safety of AADC Gene Therapy for Moderately Advanced Parkinson Disease: Three-Year Outcomes From the PD-1101 Trial

We appreciate the comment by Palma on our research.1 The presence of serum AAV2 neutralizing antibodies (nAbs) was determined using a validated ELISA method at baseline and then at 1-, 3-, 6-, and 12-month postinfusion of AAV2-AADC gene therapy. At baseline, all treated participants met the inclusion criterion with nAb ≤1:1,200 and 11 participants (73%) had nAb below the lower limit of detection. Twelve months after administration of VY-AADC01, most participants (12, 80%) developed nAb at titers ranging from 1:57 to 1:7,273, whereas 2 participants from cohort 1 and 1 participant from cohort 2 had no detectable nAb. Peak titers appeared at 6 months with either stable or lower titers at 12 months. Neither the presence of preexisting nAb above the detection limit nor an increase in nAb titer from baseline precluded an increase in 6-[18F]fluoro-l-dopa uptake ratio after administration of VY-AADC01. These findings, along with the clinical stability of these participants over the 3-year study, suggest that an inflammatory response to AAV2 did not affect AADC gene expression.