Prasinezumab
Phase 3: large human trials
An antibody aimed at the alpha-synuclein protein, being tested to see if it can slow Parkinson's. Results so far are mixed and not yet conclusive.
- Stage: Phase 2b (PADOVA)
- Type: Disease-modifying
- Developer: Roche and Prothena
- Target: Alpha-synuclein
- How it works: An antibody infusion designed to grab onto alpha-synuclein, the misfolded protein that builds up in Parkinson's, and help clear it.
- Who it's for: People with early Parkinson's, most on a stable dopamine medication.
- Key trials: NCT04777331, NCT03100149
- Last reviewed: 2026-06-01
What it is
Prasinezumab is a lab-made antibody given by infusion. The idea is to target alpha-synuclein, the protein that clumps abnormally in Parkinson's, in hopes of slowing the loss of brain cells. This is one of the most-watched attempts at a disease-modifying treatment.
Where it stands
An earlier Phase 2 study (PASADENA) missed its main goal but hinted at slower worsening of movement on some secondary measures. The follow-on Phase 2b study, PADOVA, in people on symptomatic medication, reported a result that did not reach statistical significance on its primary endpoint, with a signal the developers consider worth pursuing.
What the data shows so far
PASADENA enrolled around 316 people over 52 weeks and did not beat placebo on its pre-specified primary endpoint. PADOVA enrolled roughly 575 people; its primary endpoint (time to meaningful motor progression) narrowly missed statistical significance overall, with a larger apparent effect in a subgroup on levodopa. These are exactly the kind of results that need a confirmatory trial before drawing conclusions.
What families should know
This is research aimed at the disease itself, not at quick symptom relief. Any benefit would show up as slower decline over years, not as feeling better next week. It has not been shown to clearly slow Parkinson's yet.
Caveats
No trial has yet hit its primary endpoint with statistical significance, so it is not proven to slow the disease. Subgroup signals (e.g. in people on levodopa) can disappear in a properly designed confirmatory study and should not be over-read.
Timeline
Most recent first.
- 2024, PADOVA Phase 2b reported as narrowly missing its primary endpoint, with a subgroup signal.
- 2020, PASADENA Phase 2 misses its primary endpoint.
Sources
Last reviewed: 2026-06-01. Back to the Parkinson's drug pipeline