Ambroxol

Phase 3: large human trials

A repurposed cough medicine being tested as a possible disease-modifier, with special interest in people who carry a GBA gene variant.

• Stage: Phase 3 (ASPro-PD)
• Type: Disease-modifying
• Developer: Academic / investigator-led (a repurposed cough medicine)
• Target: GCase enzyme / GBA pathway
• How it works: An old cough/mucus medicine being repurposed to boost an enzyme (GCase) that helps cells clear waste, especially relevant to people with GBA gene variants.
• Who it's for: Studied broadly in Parkinson's, with particular interest in people who carry a GBA gene variant.
• Key trials: NCT05778617
• Last reviewed: 2026-06-01

What it is

Ambroxol has been used for decades to loosen mucus. Researchers noticed it can raise the activity of GCase, an enzyme that helps brain cells clear waste proteins. Low GCase activity is linked to Parkinson's, especially in people with GBA gene variants, so the hope is that boosting it could be protective.

Where it stands

After encouraging early-stage work, a larger trial (ASPro-PD in the UK) has been testing whether it slows progression. Results are needed before any conclusions.

What the data shows so far

An earlier small study showed ambroxol reached the brain and engaged its target (raising GCase), and was well tolerated, but was not designed to prove it slows Parkinson's. The larger trial is the real test.

What families should know

Because it is a cheap, long-used drug, ambroxol attracts a lot of hope and DIY interest. It is not approved for Parkinson's, the dose used in trials is much higher than for cough, and self-medicating is not advised. Any benefit may be greatest in GBA carriers.

Caveats

Not proven to slow Parkinson's; pivotal results pending. Benefit may be limited to GBA-variant carriers. Trial doses are far higher than over-the-counter use. Do not self-treat.

Timeline

Most recent first.

• 2022-2023, Larger Phase 3 progression trial underway.
• 2020, Early-stage study shows target engagement and good tolerability.

Sources

• Cure Parkinson's (ambroxol programme)

Last reviewed: 2026-06-01. Back to the Parkinson's drug pipeline