Study summary
A drug blocking the LRRK2 enzyme did not slow Parkinson's
What was tested
BIIB122, a pill that blocks LRRK2, an enzyme overactive in some people with Parkinson's, tested in people without the LRRK2 gene variant.
What they found
- The drug did not slow worsening on the main movement-and-daily-living scale.
- Other measures showed no benefit either.
- Development was stopped for people without the gene variant. A separate trial in carriers of the variant continues.
- A second genetic-target drug, aimed at the GBA pathway, also missed in 2026.
What it means
Two of the most-watched "precision" approaches failed in the same year, at least in people without the matching gene variant.
Last reviewed 2026-11-14 by the Find a Trial editorial team.
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