Open-Label Extension Study of ATH434-DP2 in Patients with Multiple System Atrophy

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What is this study about?

This clinical trial is being done in Multiple System Atrophy, a rare disease that affects body movement, balance, and some automatic body functions such as blood pressure control. The study uses ATH434-DP2, a tablet taken by mouth, to provide continued access to this treatment and to look at its long-term safety and how well it is tolerated.

The purpose of the study is to assess the long-term safety and tolerability of ATH434-DP2 in people with Multiple System Atrophy. In this open-label extension study, treatment is given for an extended period, and participants continue taking the study medicine while the study team monitors general health, side effects, blood pressure changes when standing up, and other routine medical checks. The study is designed to follow how people do over time without using a placebo.

1 start of study treatment

After joining this extension study, you start open-label treatment, which means you receive ATH434 and the treatment is not blinded.

The study medicine is ATH434-DP2, a tablet taken by mouth.

The dose is 150 mg each time it is taken.

The medicine is taken for the long-term period of the study, as part of this extension study.

2 ongoing treatment and monitoring

During the study, you continue taking ATH434 as directed for the study period.

Your safety and how well you tolerate the medicine are checked over time.

The study looks at adverse events, which are unwanted medical problems that happen during treatment, and serious adverse events, which are more severe unwanted medical problems.

Your laboratory results are checked. Laboratory results are measurements from tests on blood or other body samples.

Your vital signs are checked. Vital signs are basic body measurements such as pulse and blood pressure.

Orthostatic measures are also checked. These are measurements taken when changing position, such as going from lying down or sitting to standing, to see how your body responds.

The amount of ATH434 you are exposed to during the study is assessed.

Any treatment discontinuation because of side effects is recorded. Treatment discontinuation means stopping the study medicine.

Any deaths during the study are recorded.

3 end of study period

Your participation continues through the study period until the extension study ends.

The estimated study period runs from 2026-03-26 to 2027-05-13.

Who Can Join the Study?

Must have completed the ATH434-201 study and followed the study rules as required.
Must be willing and able to give written informed consent before any study procedure. This means signing a form that says the person understands the study and agrees to take part.
Must be able to attend the planned study visits, including clinic visits and remote visits (visits done by phone or video), as scheduled.
Must be expected, in the study doctor’s judgment, to benefit from treatment with ATH434.
If female, must meet one of these conditions: postmenopausal (meaning no monthly periods for at least 12 months, with a blood test showing hormone levels that match menopause), surgically sterile (meaning unable to become pregnant because of surgery such as removal of the uterus or ovaries, done at least 6 months before joining), or of childbearing potential and willing to follow the required contraception rules. Contraception means using approved birth control to prevent pregnancy.
If male, must agree to follow the required contraception rules.

Who Cannot Join the Study?

People who stopped the earlier ATH434-201 treatment for any reason cannot take part.
People with any medical or mental health condition that, in the study doctor’s opinion, would make the treatment more risky than helpful cannot take part.
People with low hemoglobin cannot take part. Hemoglobin is a blood protein that carries oxygen. This means: men below 13 g/dL and women below 11 g/dL.
People with abnormal liver test results cannot take part. This includes ALT or AST higher than 3 times the upper normal limit, or total bilirubin higher than 1.5 times the upper normal limit. ALT and AST are liver enzymes, and bilirubin is a substance measured to check liver function.
People with kidney problems cannot take part if their creatinine clearance is below 50 mL/min. Creatinine clearance is a test that shows how well the kidneys filter waste from the blood.
People with other important abnormal test results or health problems that the study doctor considers significant cannot take part.
People with a history of certain neurological events or brain and nerve abnormalities cannot take part. Neurological means related to the brain, spinal cord, or nerves.
People taking medicines that are not allowed in the study cannot take part, especially medicines that may affect how ATH434 is broken down in the body.
People with a known allergy or sensitivity to ATH434 or to any ingredient in the study medicine cannot take part.
Pregnant or breastfeeding women cannot take part, and women who plan to become pregnant or breastfeed during the study cannot take part.
People who took part in another interventional medical study within the last 30 days or within 5 drug half-lives of the other treatment, whichever is longer, cannot take part. A half-life is the time it takes for half of a medicine to leave the body.
People who are planning to join another interventional medical study while in this study cannot take part.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Centre Hospitalier Universitaire De Bordeaux	Bordeaux	France
Oncopole Claudius Regaud	Toulouse	France

Other Sites

Site Name	City	Country	Status
Hopital Beaujon	Clichy	France
Amuydzfwfu Pnktyuta Hiaqzceg Dy Mpannymzj	Marseille	France

Trial status

Country	Status	Recruitment Start
France	Not yet recruiting	26.03.2026

Trial locations

Investigated drugs:

5,7-DICHLORO-2-((ETHYLAMINO)METHYL)-8-HYDROXY-3-METHYLQUINAZOLIN-4(3H)-ONE METHANESULFONATE

ATH434 is the study medicine being tested in this trial. It is taken by mouth as a tablet. The trial is looking at how safe it is for long-term use and how well people can tolerate it in patients with multiple system atrophy. This medicine is being given in an open-label extension study, which means everyone in the study receives the active treatment and knows what they are taking.

Investigated diseases:

Multiple system atrophy

Multiple System Atrophy – Multiple System Atrophy is a rare nervous system disease that gradually affects body functions controlled automatically, such as movement, balance, blood pressure, bladder control, and other basic body processes. It usually begins in adulthood and can start with problems like stiffness, slowed movement, unsteadiness, faintness on standing, or trouble with bladder function. As it progresses, symptoms become more widespread and more severe, with increasing difficulty walking, speaking, swallowing, and maintaining normal body control. The disease develops over time and can include a mix of movement problems and automatic body function problems.

Trial ID:

2025-524317-88-00

Trial Phase:

Therapeutic exploratory (Phase II)

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Open-Label Extension Study of ATH434-DP2 in Patients with Multiple System Atrophy

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?