The ClinicalTrials.gov registry now lists NCT01621581, a Phase 1 study of gene transfer for advanced Parkinson's disease (PD), with an overall status of completed. The record is sponsored by the National Institute of Neurological Disorders and Stroke (NINDS) and was last updated June 18, 2026. According to the registry, the study began on March 13, 2013 and carries a completion date of February 4, 2022, and it enrolled 25 participants. Its official title describes it as "A Phase 1 Open-Label Dose Escalation Safety Study of Convection Enhanced Delivery (CED) of Adeno-Associated Virus Encoding Glial Cell Line-Derived Neurotrophic Factor (AAV2-GDNF) in Subjects With Advanced Parkinson's Disease."

The intervention is listed in the record as a genetic agent and is described as an "Adeno-Associated Virus Encoding Glial Cell Line-Derived Neurotrophic Factor (AAV2-GDNF) Administered via Bilateral Stereotactic Convection-Enhanced Delivery." Where many gene-therapy programs rely on systemic or cerebrospinal-fluid routes, this study documents direct delivery into brain tissue: per the detailed description, bilateral catheters are placed surgically through the skull, and the vector is delivered by convection-enhanced delivery to both putamina at a stated volume of 450 microliters per hemisphere. The putamen is a region the registry's rationale ties to the dopamine system that PD degrades.

"While medications can temporarily alleviate the symptoms of Parkinson s disease (PD), they do not influence the degenerative process."— ClinicalTrials.gov, NCT01621581, source

That single sentence frames the scientific premise the record lays out. The detailed description states that progressive loss of nigral dopaminergic neurons — "the pathological hallmark of PD" — results in progressive neurologic dysfunction and death, and that glial cell line-derived neurotrophic factor (GDNF) "was first identified based on its ability to promote the survival of embryonic DA neurons in vitro," with research demonstrating beneficial effects in animal models of PD. The record is candid about prior efforts: it notes that "preliminary clinical trials of GDNF infusions have yielded inconclusive results," and that observed problems with tolerability and efficacy "may have been related to the methods of delivery." The registry positions gene transfer via direct viral-vector delivery as the approach this study set out to test.

What the record reports about design and population

The eligibility section lists a minimum age of 18 years and no stated maximum, and includes both sexes. The detailed description specifies adult subjects "with advanced Parkinson s disease, who are candidates for surgical treatment for Parkinson s disease and who meet all Inclusion and Exclusion Criteria." The registry frames the trial as a single-center, open-label, dose-escalation safety and tolerability study, and the record's actual enrollment of 25 participants exceeds the 24-subject figure cited in the design narrative.

The participant journey documented in the record is long and procedurally intensive. According to the registry, participants are in the study for about five years, with 18 outpatient study visits and a three-day hospital stay, plus possible overnight stays for follow-up. Screening — a physical exam, medical history, blood sampling, tests of PD symptoms, mood and memory testing, and imaging to locate the infusion target — takes place up to 60 days before surgery. The record describes a baseline visit about a month before surgery, during which participants keep a diary of motor problems and undergo movement tests before and after a regular dose of levodopa. After the surgical infusion of AAV2-GDNF, the record states that participants recover in the hospital for at least two days and undergo additional lumbar punctures at 6 and 18 months, with neurosurgeon visits at one, two, and four weeks and regular follow-up every three months for the first three years.

How the trial defines its primary measure

The registry lists a single primary outcome: to "Assess the safety and tolerability of 4 different dose levels of AAV2-GDNF," measured by treatment-related adverse events. That is consistent with the Phase 1, dose-escalation design the record describes. As of this update, the registry indicates the study does not have posted results, so the entry reflects a documented status of completed and the design details above rather than a reported clinical readout. The record itself draws no conclusions about whether the gene transfer slowed the degenerative process it describes.

For readers tracking the patent and licensing terrain of central-nervous-system gene therapy, the entry is most useful as a primary-source marker of a specific construct-and-delivery combination. The record names the elements an IP or licensing review would want to locate: an AAV serotype 2 vector, a human GDNF complementary-DNA payload, and convection-enhanced delivery into the putamen via bilateral stereotactic catheters. Each maps onto a recognizable category of gene-therapy claims — capsid and serotype, transgene cassette, and method of intraparenchymal administration. The ClinicalTrials.gov record asserts no patent position; it documents that an NINDS-sponsored program advanced this combination through a first-in-human Phase 1 study to completion.

The entry also contrasts instructively with intrathecally delivered AAV programs that target the central nervous system through the cerebrospinal fluid. Here the registry documents direct intraparenchymal infusion — vector pushed under pressure into a defined brain region by convection-enhanced delivery — rather than systemic or spinal-fluid routes. What the record establishes is narrow and concrete: as of June 18, 2026, the NINDS lists this 25-participant, single-center Phase 1 safety study of AAV2-GDNF for advanced Parkinson's disease as completed. Readers seeking the trial's safety and tolerability findings will need to await results posted to the registry or to the peer-reviewed literature, neither of which is contained in the current record.