Approach 4 of 6
Look beyond the brain
Do the gut, the immune system or metabolism drive it?
60 steps since 1967. 6 moved us forward. Many leads, few clear wins. The final-stage diabetes-drug trial, Exenatide-PD3, did not slow Parkinson's. Drugs that calm the immune system are now in larger trials, the biggest due in 2027. As of Oct 2026
Facts on this page checked 18–22 Oct 2026
Each dot is one step in this approach: a discovery, a new tool or a trial, by the year it started.
- 6 moved us forward
- 5 waiting for results
- 36 still open
- 2 overtaken by better ideas
- 11 dead ends
Where it stands
- How far it has got
- Step 4 of 5 · Final large trials
- Has it slowed Parkinson's?
- Not yet shown
- Tried and did not work
- 9 trials
- Next result
- Nov 2026TB006 · Phase 2
The idea in brief
Parkinson's may not start only in the brain. Some researchers think the gut, the immune system, how the body handles sugar, or things in our surroundings may play a part. This page looks at all four.
The gut
Gut problems often come first. In 2001, a large study found that men with constipation had a higher chance of later Parkinson's. In 2016, mouse work tied gut bacteria, called the microbiome, to Parkinson's-like disease.
So scientists tried changing the bacteria. The main method was a faecal transplant, which puts donor stool into the bowel. Most of these trials did not work.
The immune system
Researchers found active immune cells in Parkinson's brains as long ago as 1988. Many now ask whether inflammation (the body's alarm response) helps damage brain cells.
Two kinds of drug are being tried. Some dampen the whole immune system. Others block one alarm switch, called NLRP3. The NLRP3 blockers are now in larger trials, such as TARBELA-PD.
Diabetes drugs
People with type 2 diabetes are more likely to get Parkinson's. So scientists tested diabetes drugs that copy a gut hormone called GLP-1. These include exenatide, lixisenatide and semaglutide.
Exenatide looked helpful in a small trial with no placebo in 2013. The large trial, Exenatide-PD3, did not slow Parkinson's in 194 people. The result has not been withdrawn. The journal has published a concern about one trial site.
Lixisenatide, in LixiPark, was positive but small, with 156 people. Nausea was common. It needs a larger test. Semaglutide results are expected from Mar 2027, but dates are expected, not promised.
Surroundings and lifestyle
Some things are linked to Parkinson's, but none is proven to cause it. They include pesticides (Pesticides and solvents linked to Parkinson's), head injury (Head injury raises Parkinson's risk) and air pollution (Air pollution and Parkinson's). Most people with Parkinson's have no single known cause. Nobody should feel to blame.
Smokers and coffee drinkers get Parkinson's less often. This does not mean anyone should take it up. The nicotine patch did not work, and smoking is harmful (Smoking and coffee: protective associations). Exercise is good for health and symptoms. Whether it slows Parkinson's is not yet shown (Exercise (SPARX and SPARX3)).
How we got here
What has been tried
Each row is one trial in people. Its dot shows how it turned out, using the same key as the chart above.
Results already in
21 trials
Grouped by the line of research they belong to. Open a group to see its trials.
The gut5 finished trials2 did not work3 mixed or early
-
Soroka faecal transplant pilot · a faecal transplant, which puts donor gut bacteria into the bowel
Mixed or early results
Only 10 people took part and no results are public. Too small to show whether it slows Parkinson's.
-
ENT-01 (KARMET) · squalamine, a pill aimed at gut nerves
Mixed or early results
Eased constipation in 150 people, with more nausea. It tested a symptom, not whether Parkinson's slows.
-
Finnish faecal transplant trial · a faecal transplant, given once by colonoscopy
Did not work
No benefit at six months in 48 people. Stomach side effects were more common with donor stool.
-
GUT-PARFECT · a faecal transplant, given through a tube into the bowel
Mixed or early results
In 46 people, movement scores improved more with donor stool at 12 months. It is small, and later trials did not repeat it.
-
EFFACE-PD · a faecal transplant, given once by colonoscopy
Did not work
Did not change movement scores over 12 months in 59 people.
The immune system7 finished trials2 did not work5 mixed or early
-
Sargramostim · sargramostim, a white blood cell growth drug
Mixed or early results
Raised immune cells that act as brakes in 20 people. Later steady scores in 5 people had no comparison group. A larger controlled trial is needed.
-
GRF6021 · an infusion made from donated blood plasma
Mixed or early results
Tolerated in 79 people with memory problems, but no clear gain over placebo. Too small and short to say anything about slowing.
-
AKST4290 (TEAL) · a pill that blocks an immune receptor called CCR3
Did not work
Did not beat placebo in 110 people over 12 weeks. Both groups improved a little, and placebo slightly more.
-
VTX3232 · an NLRP3 blocker, a pill that calms inflammation
Mixed or early results
Lowered inflammation markers in about 10 people over 28 days, with no comparison group. It shows the drug acts on its target, not that it helps.
-
VENT-02 · an NLRP3 blocker, a pill
Mixed or early results
The company stopped it early after 29 people and gave no reason or results. We cannot say if it worked.
-
AZA-PD · azathioprine, a drug that dampens the immune system
Did not work
Did not meet its main goal in 66 people over 12 months. Immune markers moved, but symptoms did not clearly improve.
-
HCQ-PD · hydroxychloroquine, an arthritis and malaria drug
Mixed or early results
A study of 40 people, all given the drug and none given placebo. Its registry has not been updated, and no results exist.
Diabetes drugs8 finished trials5 did not work2 mixed or early1 replaced
-
Exenatide pilot · exenatide, a diabetes drug
Replaced by a newer approach
A small study in 44 people, with no placebo injections. It seemed to help, but the authors said it was not proof. The larger trial later found no benefit.
-
Pioglitazone (FS-ZONE) · pioglitazone, a diabetes pill
Did not work
Unlikely to slow early Parkinson's at either dose in 210 people. The researchers did not recommend a larger trial.
-
PT320 · a slow-release form of exenatide
Mixed or early results
A Korean trial planned for 99 people. No result has been shared since 2021, so we cannot say if it worked.
-
PD STAT · simvastatin, a cholesterol drug
Did not work
Did not slow Parkinson's in 235 people. Movement scores worsened slightly more on the drug than on placebo.
-
NLY01 · a long-acting diabetes-type drug aimed at brain immune cells
Did not work
Did not beat placebo in 255 people over 36 weeks, according to the company. No journal paper has been published.
-
LixiPark · lixisenatide, a diabetes drug
Mixed or early results
In 156 people, movement scores stayed flat while placebo scores worsened by 3 points. The gap was small, and nausea was common. It needs a larger test.
-
Stockholm exenatide trial · exenatide, a diabetes drug
Did not work
Brain scans changed, but movement scores did not, in 59 people. This matches the larger UK trial.
-
Exenatide-PD3 · exenatide, a diabetes drug
Did not work
Did not slow Parkinson's in 194 people over two years. The journal has published a concern about one trial site.
Surroundings and lifestyle1 finished trial1 mixed or early
-
Exercise (SPARX and SPARX3) · hard treadmill exercise
Mixed or early results
In 128 people, hard treadmill exercise kept movement scores nearly steady over six months. SPARX3, in 370 people, compares two exercise levels and has not reported.
Still to come
5 trials · dates are expected, not promised
The next result is due in Nov 2026, from TB006. The largest trial still to report, BHV-8000, is expected in Aug 2027.
-
TB006 · an antibody drug aimed at inflammation
Result due Nov 2026
Will tell us, early on, whether an antibody against galectin-3 changes symptom scores compared with placebo. It cannot prove slowing.
Who: People aged 50 to 80 with early Parkinson's; enrolment is closed · Last checked 19 Oct 2026
-
MOST-ABLE (Osaka) · semaglutide, a diabetes drug, as a daily tablet
Result due Mar 2027
Will tell us whether a daily semaglutide tablet slows the decline in movement in 99 people over 48 weeks, compared with placebo.
Who: People with early Parkinson's, in Japan · Last checked 19 Oct 2026
-
DAPA-PD · dapansutrile, a tablet that blocks NLRP3
Result due May 2027
Will tell us whether the tablet is safe and lowers inflammation in 36 people over six months. Too small to show slowing.
Who: People aged 50 to 80 with early Parkinson's and raised inflammation in the blood, at one site in Cambridge · Last checked 18 Oct 2026
Details and sources: DAPA-PD Check if it is recruiting: DAPA-PD
-
BHV-8000 · a pill that calms the immune system
Result due Aug 2027
Will tell us whether an immune-calming pill delays worsening of everyday movement over 48 weeks, in 550 people.
Who: People aged 40 to 80 diagnosed within two years; smokers are not included · Last checked 19 Oct 2026
Details and sources: BHV-8000 Check if it is recruiting: BHV-8000
-
TARBELA-PD · RO7568282, a capsule that blocks NLRP3
Result due Dec 2028
Will tell us whether the capsule delays worsening of movement in 474 people with early Parkinson's.
Who: Adults aged 40 to 85 on levodopa alone, without movement complications · Last checked 19 Oct 2026
Details and sources: TARBELA-PD Check if it is recruiting: TARBELA-PD
In words
Of the 26 trials in people, 9 did not work, 11 had mixed or early results, 1 was replaced by newer approaches, and 5 have results due. The first is due in Nov 2026; the largest, BHV-8000, in Aug 2027.
What the dead ends taught us
- A good early result is not proof. Exenatide seemed to help in a small trial with no placebo, then did not slow Parkinson's in a large one. (Exenatide pilot; Exenatide-PD3; Stockholm exenatide trial)
- Changing the brain is not the same as helping. Exenatide changed brain scans but not movement scores. (Stockholm exenatide trial)
- Faecal transplants mostly did not work. One small trial showed a gain, but two later trials did not. (GUT-PARFECT; Finnish faecal transplant trial; EFFACE-PD)
- Calming the immune system was not enough on its own. Azathioprine and a CCR3 blocker did not work. (AZA-PD; AKST4290 (TEAL))
- Links and animal results are not proof. A cholesterol drug, tried because users had lower risk, did not slow Parkinson's. Nor did a diabetes pill that protected brain cells in animals. (PD STAT; Pioglitazone (FS-ZONE))
Most drugs tested against any brain disease do not work. Each one that fails rules something out and shapes the next trial.
What it would mean for you
If one of these approaches works, it would most likely slow Parkinson's down. It would not bring back cells already lost. It would probably help most if started early.
These treatments vary. Some are weekly injections, some are tablets, and some are drips. Safe is not the same as works. Many of the immune trials so far only check safety.
The biggest trial, BHV-8000, is expected to report in Aug 2027. Another, TARBELA-PD, is expected in 2028. Even with a good result, approval would take further time.
Should I try this now?
No. Please talk to your doctor before changing any treatment.
- Do not start exenatide, lixisenatide, semaglutide or any diabetes drug for Parkinson's without your doctor. These drugs have side effects, and they are not approved for Parkinson's.
- Do not seek faecal transplants or probiotics from clinics. The trials mostly did not work.
- Do not take supplements that claim to treat Parkinson's. None has been shown to work.
- Do not take up smoking. It is harmful.
Can I take part?
Most of these trials look for people with early Parkinson's. One, DAPA-PD, looks for raised inflammation in the blood. Each trial sets its own rules. Ask your neurologist or Parkinson's nurse.
Related approaches
Sources, and the same lanes for researchers
This page is built from 61 research landmarks. Each has its own sources; follow "Details and sources" on any trial. Facts were checked 18–22 Oct 2026. The summary was written on 22 Oct 2026.
- Gut–brain origin (14 landmarks)
- Inflammation & immunity (23 landmarks)
- Metabolic drug repurposing (13 landmarks)
- Environment & lifestyle (11 landmarks)
- See these lanes on the full map
How this project checks its facts · Report an error on this page