Safety, tolerability, and efficacy of NLY01 in early untreated Parkinson's disease: a randomised, double-blind, placebo-controlled trial
McGarry A, Rosanbalm S, Leinonen M, Olanow CW, To D, Bell A, Lee D, Chang J, +2 more
Lancet Neurology (2024) · n=255
A 36-week Phase 2 trial of NLY01 — a pegylated exenatide variant engineered for CNS exposure — found no difference from placebo on MDS-UPDRS-II+III in 255 early untreated Parkinson's patients, the largest negative GLP-1 readout in the disease to date.
NLY01 is a pegylated form of exenatide developed by D&D Pharmatech / Neuraly to extend half-life and, the developers proposed, enhance central nervous system exposure relative to the parent molecule. McGarry and colleagues conducted a 36-week Phase 2 randomized, double-blind, placebo-controlled trial at 58 U.S. movement-disorder clinics, enrolling 255 adults with early, untreated Parkinson's disease. Participants were randomized in a 1:1:1 ratio to weekly subcutaneous NLY01 2.5 mg, NLY01 5.0 mg, or placebo, with 85 patients per arm. Crucially, participants were not on symptomatic dopaminergic therapy at baseline — a design choice intended to reduce confounding of motor scores by levodopa effects.
The primary endpoint was the change from baseline to week 36 in the combined MDS-UPDRS parts II (activities of daily living) and III (motor) sum score, assessed off-medication. Neither active dose differed from placebo on the primary endpoint. Adverse events were typical of the GLP-1 receptor agonist class — nausea, decreased appetite, gastrointestinal complaints — with no excess discontinuation in the active arms. The trial was sponsored by D&D Pharmatech / Neuraly.
The NLY01 readout is the largest negative trial of a GLP-1 receptor agonist in Parkinson's disease to date and complicates the field's interpretive position. The Athauda 2017 PD3 trial of exenatide was positive at Phase 2; the subsequent UCL exenatide-once-weekly Phase 3 was negative; LIXIPARK (Meissner et al. 2024) was positive on the primary endpoint with a modest magnitude. The mix of positive and negative readouts across closely related molecules has not resolved into a clear class effect or refutation; the broader synthesis is at Parkinson's and peptides. NLY01's pegylation strategy — designed to enhance CNS penetration relative to native exenatide — failing to outperform placebo is, in particular, a data point against the simple "more CNS exposure equals more benefit" model.
The trial's design strengths are also interpretive constraints. Recruiting untreated patients reduces dopaminergic-confound noise but selects for a less symptomatic, earlier-stage population in which 36-week motor progression on placebo may be too small to leave a separable signal. The placebo group did not deteriorate substantially over 36 weeks, which compresses the window within which any neuroprotective effect could be detected. A longer trial, or a population further along the symptom trajectory, could in principle yield a different result.
The disposition of NLY01 in the brain has been claimed in preclinical work but not directly measured in humans in this trial, which means the negative readout cannot distinguish between "NLY01 reaches the relevant CNS targets and does not slow PD" versus "NLY01 does not reach the targets in sufficient quantity." This distinction matters for interpreting the result as evidence against the GLP-1 / Parkinson's hypothesis more broadly versus evidence against this particular molecule.
Industry sponsorship by D&D Pharmatech / Neuraly is disclosed; several authors were company employees, which is typical for sponsor-led Phase 2 trials and does not appear to have compromised the design or reporting. The trial's negative finding has not led to a published Phase 3, and the sponsor's program direction for NLY01 in PD has not been publicly updated to a confirmatory readout as of 2026. Replication in either direction — additional negative trials or a positive Phase 3 of a different GLP-1 agonist — remains the field's open question.
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