Parkinson's disease is a progressive condition in which the brain gradually loses the nerve cells that make dopamine. Parkinson's UK reports that around 166,000 people in the UK have a diagnosis, and estimates that up to 21,000 more are living with the condition without one. A BMJ analysis published in 2025 projected that the number of people with Parkinson's worldwide would more than double, to 25.2 million, by 2050.
This page follows the science in three parts. It traces how treatment has developed and what it has not yet solved, then lays out the peptide and growth factor research linked to Parkinson's, study by study, and finally keeps the latest news in one place. Every statement links to a journal, trial registry, regulator, charity or major news outlet, and the page is updated as new results are published.
Latest news
- China's stem cell therapy for Parkinson's: inside XS411 and the trials the West is overlooking28 October 2026
29 September 2026
AC Immune reports week 100 data from the VacSYn trial
Complete Part 1 data from 34 people, 25 on ACI-7104 and 9 on placebo, were reported as meeting all primary goals. The trial continues into a two year extension.
22 June 2026
The Lancet flags the Exenatide-PD3 paper while an inspection finding is investigated
The Lancet publishes an Expression of Concern on the Exenatide-PD3 paper. The journal says that on 18 May 2026 the trial's corresponding author told it about findings from a regulatory inspection at King's College Hospital NHS Foundation Trust, one of the trial sites. While the investigation and any effect on the study data and conclusions are assessed, the paper stands as published with the notice attached. An Expression of Concern is not a retraction. The trial had reported no benefit from exenatide.
16 June 2026
Imperial study will look for early metabolic signs of Parkinson's
The first project funded by a new Medical Research Council fund for Our Future Health data will analyse patterns in volunteers who go on to develop Parkinson's. Researchers say a better model could make future GLP-1 trials more targeted. Of three clinical trials of GLP-1 drugs in Parkinson's so far, the organisation notes, two suggested the drugs may slow the disease and the larger third did not.
11 June 2026
A 4 million dollar grant extends the VacSYn trial
The Goradia family charitable foundation funds a further two years of Part 1 to assess the long term safety and efficacy of ACI-7104, with final Part 1 data expected in the second half of 2026.
January 2026
Herantis reports the full HER-096 phase 1b dataset
The complete phase 1b data, including exploratory biomarker results, follow the topline announcement of October 2025.
22 October 2025
Parkinson's UK publishes the largest ever UK prevalence study
Based on 18 million primary care records and published in Movement Disorders Clinical Practice, the study counts around 166,000 people in the UK with a diagnosis and estimates up to 21,000 more without one.
How treatment developed
1817
James Parkinson describes the condition
The London physician James Parkinson publishes An Essay on the Shaking Palsy, the first systematic description of the illness that now carries his name. Historians of the field note that effective drug treatment then took another 150 years to arrive.
1957 to 1960
Dopamine is linked to movement
In 1957 Arvid Carlsson shows that levodopa can relieve the immobility caused by reserpine in animals, and that reserpine empties the brain of dopamine while levodopa restores it. In 1960 Oleh Hornykiewicz reports a marked loss of dopamine in the striatum of people who had Parkinson's disease.
1961
The first levodopa injections
Walther Birkmayer and Hornykiewicz give levodopa intravenously to people with Parkinson's in Vienna and report a striking effect on movement, the first clinical demonstration of dopamine replacement.
16 February 1967
High dose oral levodopa
George Cotzias and colleagues report in the New England Journal of Medicine that gradually increased, high doses of oral levodopa produce a dramatic improvement in Parkinson's disease. A second drug, carbidopa, which blocks the breakdown of levodopa outside the brain, becomes a key part of the treatment in the years that follow.
18 December 2018
Focused ultrasound approved in the United States
The US Food and Drug Administration approves MRI guided focused ultrasound for tremor dominant Parkinson's disease, based on a randomised trial of 27 people in which 20 had the procedure and 7 had a sham procedure. The approval sits alongside deep brain stimulation as a surgical option that manages symptoms. It does not slow the underlying disease.
October 2023 to January 2024
Continuous under the skin infusion of levodopa
The National Institute for Health and Care Excellence recommends subcutaneous foslevodopa and foscarbidopa for advanced Parkinson's in October 2023, and the drug is approved in the European Union in January 2024. It is a new way of delivering levodopa, not a new target.
What conventional treatment has not solved
More than half a century after Cotzias, levodopa is still described as the most effective drug treatment for the movement symptoms of Parkinson's. The treatments that have followed, from newer drug combinations to pumps, deep brain stimulation and focused ultrasound, have mostly improved how well symptoms are managed.
What none of them has done is slow the disease itself. Reporting on the large UK platform trial launched in 2025 puts it plainly: there are no disease modifying treatments that can slow, stop or reverse the progression of Parkinson's. That gap is the backdrop to the research below, where scientists have tested whether molecules that protect nerve cells, including peptides and growth factors, can change the course of the condition.
The peptide and growth factor research, study by study
2003
GDNF delivered into the brain's fluid spaces: no benefit
GDNF is a growth factor protein that supports dopamine neurons in laboratory and animal studies. In a randomised, double blind trial in advanced Parkinson's, GDNF was given through an implanted catheter into the fluid spaces of the brain. The trial found no therapeutic benefit, and low blood sodium developed in more than half of the people who received doses of 75 micrograms or more. An open label extension, which followed 16 people for up to a further 20 months, also showed no benefit.
May 2013
Exenatide: the first small trial in Parkinson's
A University College London team led by Thomas Foltynie runs a single blind study of 45 people with moderate Parkinson's. Half receive the diabetes drug exenatide, a GLP-1 receptor agonist, by injection for 12 months, and half act as controls. Blinded video ratings of the motor score improved by 2.7 points in the exenatide group and worsened by 2.2 points in controls, a difference of 4.9 points (95% confidence interval 0.3 to 9.4). The authors describe it as a proof of concept, and weight loss was common in the exenatide group. The study was funded by the Cure Parkinson's Trust.
August 2017
Exenatide: the first placebo controlled trial
The Lancet publishes a single centre, double blind trial of 62 people with moderate Parkinson's, 32 given exenatide 2 mg once a week and 30 given placebo for 48 weeks. After a 12 week washout, the off medication motor score had improved by 1.0 point in the exenatide group and worsened by 2.1 points on placebo, an adjusted difference of 3.5 points (95% confidence interval 0.3 to 6.7, p = 0.0318). Six serious adverse events occurred in the exenatide group and two in the placebo group. The authors said it was unclear whether exenatide changes the underlying disease or has a lasting symptomatic effect. The trial was funded by the Michael J Fox Foundation.
February 2019
GDNF infused directly into the putamen: primary goal missed, brain scans changed
A Bristol team led by Alan Whone reports a randomised, double blind trial of GDNF given directly into the putamen every four weeks for 40 weeks through a skull mounted port. Forty one people took part, 6 in a pilot stage and 35 in the main stage, receiving 120 micrograms per putamen. The primary goal, the percentage change in the off medication motor score at week 40, was not met: the score fell by 17.3% in the GDNF group and 11.8% on placebo, a difference of 4.9% (p = 0.41). Brain imaging told a different story, with dopamine tracer uptake rising by between 25% and 100% in parts of the putamen in the GDNF group.
In an 80 week open label extension in which all 41 people received GDNF, the motor score fell by 26.7% in those on GDNF throughout and 27.6% in those switched from placebo. The authors concluded that future GDNF testing would probably need a longer treatment period, a higher dose, or both.
May 2023
CDNF: a first human trial of a second growth factor
Herantis Pharma and collaborators publish a phase 1 trial of CDNF, a protein that protected dopamine neurons in animal models, delivered monthly into the putamen through an implanted port. Seventeen people with moderate Parkinson's were randomised to placebo (6), 0.4 mg CDNF (6) or 1.2 mg CDNF (5), with a six month main study followed by six months of active treatment. The primary goals were safety and tolerability. The authors report that CDNF was safe and well tolerated and that possible signs of a biological response were seen in individual patients, including changes on dopamine transporter brain scans in a few people who received CDNF.
March 2023 and January 2024
NLY01: a brain penetrant GLP-1 drug misses its target
Neuraly announces in March 2023 that NLY01, a long acting form of exendin-4, the molecule behind exenatide, did not meet the primary goal of its phase 2 trial. The full results appear in The Lancet Neurology in January 2024. In 255 people with early, untreated Parkinson's at 58 US clinics, weekly NLY01 at 2.5 mg or 5.0 mg did not change the combined motor and daily living score over 36 weeks compared with placebo (difference of 0.39 points lower for 2.5 mg and 0.36 points higher for 5.0 mg). Nausea was the most common side effect. A subgroup analysis raised the possibility of a motor benefit in people under 60, which the authors said needs to be tested in further studies.
April 2024
Lixisenatide: a second GLP-1 drug shows a motor difference
The New England Journal of Medicine publishes LIXIPARK, a phase 2 trial led from Bordeaux. One hundred and fifty six people with early Parkinson's were randomised, 78 to daily lixisenatide 20 micrograms and 78 to placebo, for 12 months followed by a two month washout. On the main measure, the on medication motor score, the lixisenatide group stayed level (a change of minus 0.04 points) while the placebo group worsened by 3.04 points, a difference of 3.08 points (95% confidence interval 0.86 to 5.30, p = 0.007). After the washout, off medication motor scores were 17.7 on lixisenatide and 20.6 on placebo. Nausea occurred in 46% of people on lixisenatide and vomiting in 13%. The trial was funded by the French Ministry of Health and others, and the authors said longer and larger trials are needed.
20 June 2024
UB-312: a peptide vaccine aimed at alpha-synuclein
Nature Medicine publishes a phase 1 trial of UB-312, a synthetic peptide designed to make the immune system produce antibodies against clumped alpha-synuclein, the protein that builds up in the brains of people with Parkinson's. The part of the study in people with early Parkinson's included 20 patients followed for 24 weeks. Twelve of 13 patients who received the vaccine developed antibodies against the clumped protein. Exploratory spinal fluid tests, which the sponsor Vaxxinity highlighted, suggested lower levels of aggregated alpha-synuclein. The authors noted that antibodies reached the spinal fluid in only some participants and that the dose will need further optimisation.
4 February 2025
Exenatide-PD3: the largest GLP-1 trial finds no difference
The Lancet publishes Exenatide-PD3, a UK phase 3 trial run at six hospitals and led by Tom Foltynie at University College London. Between January 2020 and April 2022, 194 people were randomised, 97 to weekly extended release exenatide 2 mg and 97 to placebo, for 96 weeks. At 96 weeks the off medication motor score had worsened by 5.7 points on exenatide and 4.5 points on placebo (adjusted coefficient 0.92, 95% confidence interval minus 1.56 to 3.39, p = 0.47). Serious adverse events occurred in 9% of the exenatide group and 11% of the placebo group. The authors wrote that they found no evidence to support exenatide as a disease modifying treatment, and called for studies of agents with better target engagement or in specific subgroups. The trial was funded by the National Institute for Health and Care Research and Cure Parkinson's. In June 2026 The Lancet attached an Expression of Concern to the paper while an inspection finding at one site is investigated (see Latest news).
Foltynie said the team would examine whether blood test results such as pre-diabetes might predict a better response, because the earlier, smaller positive trials may have included more such people.
8 October 2025
HER-096: a small peptide based on CDNF reaches people
Herantis Pharma reports topline results from a phase 1b trial of HER-096, a small peptide derived from the active region of CDNF that can be given by injection under the skin instead of into the brain. The trial included 24 people with early Parkinson's, who received 200 mg or 300 mg of HER-096 or placebo twice a week for four weeks. The company reported that it met its primary and secondary goals, was generally safe and well tolerated, and reached the brain, with blood brain barrier penetration confirmed in patients. The full dataset, including exploratory biomarkers, followed in January 2026. Herantis said it planned to move into a phase 2 trial in early stage patients in 2026.
11 December 2025
ACI-7104.056: first interim data from an alpha-synuclein vaccine
AC Immune reports interim results from Part 1 of its phase 2 VacSYn trial of ACI-7104.056, an active immunotherapy designed to train the immune system against alpha-synuclein. Part 1 includes 34 people with early Parkinson's randomised 3 to 1 to the treatment or placebo. The company reported that every treated person produced antibodies, and that spinal fluid markers of nerve damage suggested stabilisation. At week 74 the treated group showed no meaningful progression on the motor score while the placebo group worsened as expected. Part 1 was designed to test safety and immune response rather than clinical benefit, and these are company reported results from a small trial that has not been peer reviewed.
Trials running now
Results awaited
MOST-ABLE: oral semaglutide in Parkinson's, Japan
A phase 2, randomised, double blind trial led from the University of Osaka is testing oral semaglutide at 7 mg or 14 mg against placebo in 99 people with early Parkinson's at eight Japanese sites. Treatment lasts 36 weeks followed by a 12 week washout, and the primary measure is the change in the off state motor score at 48 weeks. Recruitment ran from November 2023 to September 2024, and the protocol was published in BMJ Open in December 2025. The Japanese trial registry lists it as no longer recruiting. No results had been published in the sources checked as of 5 November 2026.
Recruiting and randomising
REGENERATE-PD: GDNF gene therapy (AB-1005)
AskBio, a Bayer company, is running a phase 2, randomised, double blind, surgery controlled trial of AB-1005, a gene therapy that delivers the gene for GDNF directly into the putamen, in people aged 45 to 75 with moderate Parkinson's. About 87 participants are planned across sites in the United States, UK, Germany and Poland, and the first were randomised in January 2025. The primary measure is the change in good on time recorded in a motor diary at 18 months. An earlier phase 1b study in 11 people reported no serious adverse events attributed to the treatment at 36 months, and the US regulator granted the therapy Regenerative Medicine Advanced Therapy designation.
Extension under way
VacSYn: the alpha-synuclein vaccine trial continues
AC Immune reported week 100 results from Part 1 on 29 September 2026. The data cover all 34 people enrolled, 25 on ACI-7104 and 9 on placebo. The company said all primary goals were met, every treated person had an antibody response, antibodies reached the spinal fluid in all patients, and a signal for total alpha-synuclein in spinal fluid suggested target engagement. Part 1 was designed to assess safety, tolerability and immune response, not clinical outcomes. The trial continues into a two year extension, supported by a 4 million dollar grant announced in June 2026.
Registered, listed as not yet recruiting
GLP1R in Parkinson's: semaglutide at the University of Oslo
A phase 2 trial planned to enrol 270 newly diagnosed people has been registered since 2018. It would test weekly semaglutide 1 mg or placebo for 24 months, followed by two years in which everyone receives semaglutide, with blood and spinal fluid samples to study inflammation and whether the drug crosses into the brain. The registry lists its status as not yet recruiting.
April 2026 to March 2027
STRAT-GLP1: which people might respond to GLP-1 drugs
Dr Cynthia Sandor at Imperial College London leads a Michael J Fox Foundation funded programme that asks a different question after the mixed trial results: not whether GLP-1 drugs work in Parkinson's overall, but which patients are likely to benefit and whether they can be identified before treatment. It uses genetics, large health databases and blood protein measurements, and is not a treatment trial. A linked study using Our Future Health data, announced in June 2026, looks for early metabolic warning signs in people who go on to develop Parkinson's.
Recruiting across the UK
EJS ACT-PD: the UK platform trial (not peptide based)
Listed for context because it is the largest disease modification trial in the UK. The £26 million EJS ACT-PD platform trial opened on 16 October 2025 to recruit 1,600 people from more than 40 hospitals. It tests telmisartan, a blood pressure drug, and terazosin, used for an enlarged prostate, against a shared placebo, with ursodeoxycholic acid, used in liver disease, planned as a third treatment in 2026.
What comes next
Early 2027
The next step for the alpha-synuclein vaccine
AC Immune plans to discuss the final design of Part 2 of VacSYn with the US Food and Drug Administration in early 2027.
Planned for 2026
A phase 2 trial of HER-096
Herantis said after its phase 1b results that it plans a phase 2 trial of HER-096 in early stage Parkinson's to assess efficacy, safety and tolerability. As of 5 November 2026 we have not found a registered start date.
To be reported
MOST-ABLE and the exenatide subgroup analyses
The first results from the oral semaglutide trial in Japan have not yet been published. The UCL team behind Exenatide-PD3 said it would keep examining the data, including whether pre-diabetes predicts a better response.
2026
A third arm for the UK platform trial
Ursodeoxycholic acid is due to be added to EJS ACT-PD as a third treatment arm in 2026.