Lancet issues expression of concern on exenatide Parkinson's trial
The Lancet has flagged its own 2025 exenatide-in-Parkinson's trial with an expression of concern, so claims that GLP-1 drugs slow Parkinson's rest on unsettled evidence.
The Lancet has published an Expression of Concern about a 2025 phase 3 trial that tested exenatide once a week as a possible disease-modifying treatment for Parkinson's disease [1]. The notice flags the paper for readers; it is not a retraction, and the original paper remains listed in PubMed [1].
The trial report, titled "Exenatide once a week versus placebo as a potential disease-modifying treatment for people with Parkinson's disease in the UK," was published in The Lancet on Feb. 22, 2025, in volume 405, issue 10479, pages 627–636, and appeared online Feb. 4, 2025 [1]. It is described as a phase 3, multicentre, double-blind, parallel-group, randomised, placebo-controlled trial [1]. The author list includes Nirosen Vijiaratnam and Thomas Foltynie, among many others [1]. The trial paper carries the PubMed identifier 39919773 [1].
The expression of concern is cataloged separately, as its own PubMed record [1]. That notice was published in June 2026 [1].
The record for the notice carries no abstract, and the editors' specific concerns are not spelled out there [1]. It has not been disclosed what prompted the notice, which parts of the paper are being examined, or whether the questions involve the data, the analysis or the reporting [1]. The notice also does not restate the trial's results, its enrollment or its outcome measures, so those details are not available from that record [1]. The full text of the notice is available through the publisher under the identifier S0140-6736(26)01241-9 [1].
Because the notice record does not describe the trial's findings, the size of any effect exenatide had on Parkinson's symptoms or progression is not stated there [1]. Whether the journal's review will change how the trial's results should be read also is not yet known [1].
Why it matters for patients
Exenatide is a GLP-1 receptor agonist — the same broad drug class as semaglutide, which is sold as Ozempic, Wegovy and Rybelsus [1]. This trial is a prominent test of whether a drug in that class can slow Parkinson's disease rather than only ease symptoms [1]. Until the journal resolves its concerns, any claim that GLP-1 drugs treat or slow Parkinson's disease, when that claim rests on this trial, should be treated as unsettled [1].
The notice concerns only the exenatide trial in Parkinson's disease, and it does not address other GLP-1 medications or their approved uses [1]. Exenatide and semaglutide are different molecules, and the flagged trial evaluated exenatide only [1].
An expression of concern is a journal's public signal that questions exist about a published paper, and it sits apart from the trial report itself in the PubMed record [1]. It is not a finding of error, and it is not a retraction [1].
What happens next
The notice sets no timetable, and the journal has not said when its review will finish [1]. Outcomes in such cases typically include the paper standing once questions are answered, a correction, or a retraction, but the record does not indicate which is expected here [1].
Until then, the 2025 paper remains published and flagged, with the notice listed alongside it [1].
Sources
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