Overviewing 36-Month, Phase 1b Data Testing Gene Therapy AB-1005 in Parkinson Disease: Nisha Chhabria MD, FAAN

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"Given the fact that we know, with Parkinson disease, a placebo effect can last up to 18 months, if not even longer, these are hopeful results to be able to see sustained improvement at even 36 months."

AB-1005 (AskBio) is an investigational adeno-associated viral vector serotype 2 (AAV2) gene therapy that contains the human glial cell line–derived neurotrophic factor (GDNF) transgene. This design allows for stable, continuous expression of GDNF in localized regions of the brain following direct neurosurgical injection with MRI-monitored convection-enhanced delivery. Researchers have assessed AB-1005 in a phase 1b study (NCT04167540) of 11 patients with Parkinson disease (PD), revealing that the therapy met its primary end point of successful putamen coverage and was safe at 18 months.¹

In the phase 1b trial, a 1-time infusion of AB-1005 into the putamen was well tolerated, with no serious adverse events associated with the gene therapy at 36 months. Among 6 patients with mild PD and 5 patients with moderate PD, findings showed that most mild participants had stable outcomes on the Movement Disorder Society–Unified Parkinson’s Disease Rating Scale, PD motor diaries, and Levodopa Equivalent Daily Dose. Investigators also reported that the moderate group demonstrated improvement or stability on several motor measures, including PD motor diaries.²

These recent results were presented as an awarded poster at the 4th Annual Advanced Therapeutics in Movement and Related Disorders (ATMRD) Congress, held by the PMD Alliance June 27 to 30, 2025, by Nisha Chhabria, MD, FAAN, medical director of CNS clinical development at AskBio. After the congress, Chhabria spoke with NeurologyLive^® to provide further details on the outcomes from the study. In the interview, she noted that the 36-month findings support the continued investigation of the gene therapy in the REGENERATE-PD trial (NCT06285643), a phase 2, randomized, double-blind, sham surgery-controlled study.

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REFERENCES
1. AskBio presents 18-month phase 1b trial results of AB-1005 gene therapy for patients with Parkinson disease. News release. AskBio. April 16, 2024. Accessed August 14, 2025. https://www.globenewswire.com/news-release/2024/04/16/2863581/0/en/AskBio-presents-18-month-Phase-Ib-trial-results-of-AB-1005-gene-therapy-for-patients-with-Parkinson-s-disease.html
2. Phielipp N, Christine C, Merola A, et al. Preliminary efficacy of GDNF gene therapy (AAV2-GDNF; AB-1005) in Parkinson’s disease: 36-month follow-up from a phase 1b study. Presented at: ATMRD 2025; June 27-30, 2025; Washington, DC.