Glossary

A protein found in nerve cells, mostly at the tips where they pass on signals. In Parkinson's it folds into the wrong shape and sticks together in clumps.

Also called: α-synuclein, synuclein

Read more: Clear the bad protein

Tests in cells or animals, done before any trial in people. Many treatments that work in animals do not work in people.

Also called: lab studies, preclinical studies, lab only

A Y-shaped protein the immune system makes to latch on to one target. Lab-made antibodies are used as drugs, given by drip or injection. Their names often end in -mab.

Also called: antibody drug, monoclonal antibody

Read more: Clear the bad protein

A substance that mops up harmful, reactive molecules made inside cells. The damage they cause is called oxidative stress. Antioxidant supplements such as coenzyme Q10 have been tested in Parkinson's and did not slow it.

Also called: oxidative stress

Read more: Help cells clean up

Permission from a regulator, such as the FDA in the US or the MHRA in the UK, to sell a treatment for one use. Some approvals are time-limited while more proof is gathered.

Also called: licence, conditional approval, time-limited approval

Read more: Replace or repair what's lost

Something measured in the body, such as a blood level or a brain scan, that shows what a disease or a drug is doing. A change in a marker is not proof of benefit.

Also called: marker

An enzyme inside cells. When it is too active it may help alpha-synuclein build up. Drugs that block it, such as nilotinib, were first made to treat leukaemia.

Also called: c-Abl inhibitor, Abl kinase

Read more: Keep vulnerable cells alive

A medicine that slows the flow of calcium into cells, used for high blood pressure. Isradipine was tested to ease the strain on fragile dopamine cells. It did not slow Parkinson's.

Also called: isradipine

Read more: Keep vulnerable cells alive

Someone who has a particular gene change. Being a carrier can raise the chance of getting Parkinson's, but many carriers never get it.

Also called: gene carrier

Read more: Treat the inherited causes

A study that tests a treatment in people, under strict rules, to find out whether it is safe and whether it works. Trials go through phases, from small to large.

Also called: trial, study

The people in a trial who do not get the treatment being tested. They may get a placebo or their usual care. Without them, it is hard to tell whether the treatment made the difference.

Also called: control group

A brain scan that shows how many working dopamine nerve endings are left. Trials sometimes use it to measure loss, but the scan and a person's symptoms do not always agree.

Also called: DaTscan, dopamine transporter scan

A trial in which some people start a drug at once and others start it later. If the early starters stay ahead, the drug may slow the disease, not just ease symptoms.

Also called: delayed start design

A treatment that slows, stops or reverses the disease itself, not just its symptoms. No treatment has yet been shown to do this for Parkinson's.

Also called: slowing the disease, neuroprotection

A chemical messenger in the brain that helps control smooth movement. The cells that make it are the ones lost in Parkinson's. Levodopa works because the brain turns it into dopamine.

Read more: Replace or repair what's lost · Keep vulnerable cells alive

A medicine that acts like dopamine on the brain cells that receive it. It eases symptoms but has not been shown to slow Parkinson's.

Also called: pramipexole, ropinirole, rotigotine

A trial in which neither the people taking part nor their doctors know who is getting the real treatment. This stops what people expect from colouring the results.

Also called: masked, double-masked

Uncontrolled writhing or jerky movements. In Parkinson's they are most often a side effect of levodopa. Some early cell grafts also caused them.

Also called: dyskinesias

Read more: Replace or repair what's lost

A protein that does a job in the body, such as breaking something down or switching something on. The proteins made by the LRRK2 and GBA genes are enzymes.

Read more: Treat the inherited causes · Help cells clean up

Putting stool from a healthy donor into a person's bowel, to change their gut bacteria. Trials in Parkinson's have given mixed results, and none has shown that it slows the disease.

Also called: FMT, faecal microbiota transplant, stool transplant

Read more: Look beyond the brain

A gene that makes an enzyme called GCase, which works inside lysosomes. A change in GBA is the commonest inherited risk for Parkinson's. Many people with a change never get it.

Also called: GBA1, GCase, glucocerebrosidase

Read more: Help cells clean up · Treat the inherited causes

A stretch of DNA that holds the instructions for making one protein. A change in some genes can cause Parkinson's, or raise the chance of getting it.

Also called: gene change, variant, mutation

Read more: Treat the inherited causes

A treatment that puts a gene into cells, usually carried by a harmless virus. The cells then make a helpful protein. In Parkinson's it is given by surgery or an injection near the brain.

Also called: gene delivery

Read more: Replace or repair what's lost · Help cells clean up

A hormone the gut makes after eating. It helps control blood sugar. Drugs that copy it treat type 2 diabetes and obesity. In Parkinson's, the largest trials found no benefit. Smaller trials continue.

Also called: GLP-1 drugs, exenatide, lixisenatide, semaglutide

Read more: Look beyond the brain

Living cells or tissue placed in the body by surgery. In Parkinson's research, grafts of cells that make dopamine are put into the brain to replace the ones that were lost.

Also called: transplant, cell transplant

Read more: Replace or repair what's lost

A natural protein that helps nerve cells survive and grow. GDNF is the best-known one tested in Parkinson's. It does not easily reach the brain, and trials that pumped it in did not improve symptoms.

Also called: GDNF, neurotrophic factor

Read more: Replace or repair what's lost

The body's defence against germs, made of white blood cells, antibodies and the signals between them. In the brain, immune cells called microglia keep watch.

Also called: microglia, immune cells

Read more: Look beyond the brain

A drug that damps down the immune system. People with donor cell grafts may need one, so the body does not reject the cells. It raises the risk of infection.

Also called: anti-rejection drug

Read more: Replace or repair what's lost

The body's alarm response to injury or infection. Immune cells gather and send out signals. It helps healing, but if it goes on too long it may harm nearby cells, including brain cells.

Read more: Look beyond the brain

Stem cells made in a lab by reprogramming blood or skin cells, from a donor or the patient. They can be grown into dopamine-making cells for grafts. Donor cells usually need drugs to stop rejection.

Also called: iPSC, induced pluripotent stem cells, own-cell graft

Read more: Replace or repair what's lost

The main medicine for Parkinson's symptoms. The brain turns it into dopamine. It eases movement problems but does not slow the disease.

Also called: L-dopa, co-careldopa, co-beneldopa

Clumps inside nerve cells, made mostly of misfolded alpha-synuclein. They are found in the brains of most people with Parkinson's. They are named after Friedrich Lewy, who first described them.

Read more: Clear the bad protein

A gene that makes an enzyme, also called LRRK2. Some changes in the gene make the enzyme overactive and raise the chance of Parkinson's. Drugs that turn it down are being tested.

Also called: LRRK2 inhibitor

Read more: Treat the inherited causes

A small sac inside a cell that breaks down worn-out parts and waste. The GBA gene makes an enzyme that does its work inside lysosomes.

Also called: the cell's recycling bin

Read more: Help cells clean up · Treat the inherited causes

The one result a trial is designed to measure, chosen before it starts. A trial that misses its main goal has not shown that the treatment works.

Also called: primary endpoint, primary outcome

The trillions of bacteria and other microbes that live in the gut. Some studies find that people with Parkinson's have a different mix of gut bacteria.

Also called: gut bacteria

Read more: Look beyond the brain

A protein that has folded into the wrong shape. Misfolded proteins can stick together in clumps, and may make other copies misfold too. In Parkinson's the main one is alpha-synuclein.

Also called: misfolding, protein clumps, aggregates

Read more: Clear the bad protein

Tiny parts inside every cell that make its energy. Some genes linked to Parkinson's help keep them healthy.

Also called: mitochondrion, the cell's power plants

Read more: Help cells clean up

A protein inside immune cells that acts as an alarm switch. When it is set off, it drives inflammation. Drugs that block it are being tested in Parkinson's.

Also called: NLRP3 inflammasome

Read more: Look beyond the brain

A trial in which everyone knows which treatment they are getting, often with no placebo. Results can look better than they really are.

Also called: no placebo

Checking by other scientists before a study is published in a journal. Results shared only by a company, or at a meeting, have usually not been through it yet.

Also called: peer-reviewed, checked by other scientists

The first tests of a treatment in people. They are usually small. They check whether it is safe and what dose to use. They cannot show whether it works.

Also called: first tests in people

Medium-sized trials that look for early signs that a treatment works, and check its safety in more people. Most are too small or too short to show that it slows Parkinson's.

Also called: testing whether it helps

Large, final trials that test whether a treatment really works. Regulators usually need a clear Phase 3 result before they approve a drug.

Also called: final large trial

A dummy treatment that looks like the real one but has no active drug. Comparing the two shows whether the drug itself made the difference.

Also called: dummy treatment

Drugs that tell cells to make less of a protein, by blocking the message its gene sends. Two kinds are antisense drugs and siRNA. Most are injected into the spinal fluid.

Also called: antisense, ASO, siRNA, gene silencing

Read more: Clear the bad protein · Treat the inherited causes

A trial in which chance decides who gets the treatment and who is in the comparison group. This makes the groups alike, so the comparison is fair.

Also called: randomised controlled trial, RCT

Looking for people to take part. A trial that is not recruiting has not started yet, is full, or has ended.

Also called: enrolling

A sleep disorder in which people act out their dreams, sometimes shouting or lashing out. Many people with it later get Parkinson's or a related disease, so it can be an early sign.

Also called: RBD, iRBD

Repeating a study, often with more people, to see if the result holds up. Many early findings do not.

Also called: repeat study

A lab test that finds misfolded alpha-synuclein in a sample of spinal fluid, or sometimes skin. Trials use it to check that people have the protein problem before they join.

Also called: SAA, alpha-synuclein seed test, spinal-fluid test

Read more: Clear the bad protein

A pretend operation, used for comparison in trials of surgery. People can feel better after any operation, so a sham shows whether the real treatment made the difference.

Also called: fake operation, placebo surgery

Read more: Replace or repair what's lost

An unwanted effect of a treatment, such as feeling sick. Trials record every unwanted event, whether or not the treatment caused it.

Also called: adverse event

The clear fluid around the brain and spinal cord. A sample is taken with a needle in the lower back, called a lumbar puncture. Some drugs are injected into it.

Also called: cerebrospinal fluid, CSF, lumbar puncture

Read more: Clear the bad protein · Treat the inherited causes

Cells that can grow into many other kinds of cell. Scientists use them to grow new dopamine-making cells for grafts. Avoid clinics that sell untested stem-cell treatments.

Also called: embryonic stem cells, stem-cell treatment

Read more: Replace or repair what's lost

A small area deep in the brain where most of the dopamine-making cells lost in Parkinson's are found. The name means "black substance", from the dark colour of these cells.

Read more: Keep vulnerable cells alive · Replace or repair what's lost

A treatment that eases symptoms, such as stiffness or slow movement, without slowing the disease. Levodopa is one. Easing symptoms can make a drug look as if it slows Parkinson's.

Also called: symptomatic treatment, symptom relief

A public website that lists trials, what they test and when they expect to finish. ClinicalTrials.gov is the largest. This site checks each trial against its registry entry.

Also called: ClinicalTrials.gov, ISRCTN, trial register

The standard score doctors use to rate how severe Parkinson's is, covering movement, daily life and mood. A higher score is worse. Trials often measure how fast it rises.

Also called: MDS-UPDRS, symptom score, rating scale

A treatment that trains the body's own immune system to make antibodies. In Parkinson's, vaccines aim to make antibodies against alpha-synuclein.

Also called: active immunisation

Read more: Clear the bad protein

A virus emptied of its own genes and used to carry a new gene into cells. It cannot cause an infection. The most common kind is called AAV.

Also called: virus shell, AAV, vector

Read more: Replace or repair what's lost