BIIB122 (LRRK2 inhibitor)
Phase 2: mid-stage testing
A pill targeting the LRRK2 enzyme. Its large Phase 2b trial in early Parkinson's (LUMA) failed in 2026; a smaller trial in people who carry a LRRK2 variant is still running.
- Stage: Phase 2b failed; Phase 2 ongoing
- Type: Disease-modifying
- Developer: Biogen and Denali Therapeutics
- Target: LRRK2 enzyme
- How it works: A pill that dials down an overactive enzyme called LRRK2, which is linked to some inherited and non-inherited Parkinson's.
- Who it's for: Two programs: one in people with a LRRK2 gene variant, one in people with early Parkinson's regardless of genetics.
- Key trials: NCT05348785, NCT05418673
- Last reviewed: 2026-06-23
What it is
Overactivity of the LRRK2 enzyme is one of the best-understood genetic contributors to Parkinson's, and may matter even in people without a LRRK2 mutation. BIIB122 is designed to reduce that overactivity, in the hope of protecting brain cells over time.
Where it stands
The large LUMA trial in early Parkinson's reported in 2026 that it missed its main goal, so the broad early-disease version of this approach did not work. An earlier trial in people carrying a LRRK2 variant (LIGHTHOUSE) was stopped in 2023. A smaller trial in LRRK2-variant carriers is still running.
What the data shows so far
The drug clearly lowers markers of LRRK2 activity and was generally tolerated, but in the LUMA trial that did not translate into slower disease progression. Whether it helps the narrower group of people who carry a LRRK2 mutation is still being tested.
What families should know
The broad bet that this drug could help early Parkinson's regardless of genetics did not pan out in LUMA. The remaining hope is the narrower group of people who carry a LRRK2 variant, where a smaller trial continues. Enrollment criteria for that trial are specific.
Caveats
The main early-Parkinson's trial (LUMA) did not show a slowing of the disease. Any remaining benefit may be limited to people with LRRK2 variants rather than all Parkinson's, and that is still unproven. Long-term safety of suppressing LRRK2 (including possible lung effects seen in early studies) is still being monitored.
Timeline
Most recent first.
- 2026, LUMA reports it missed its main goal in early Parkinson's.
- 2023, LIGHTHOUSE (LRRK2-variant Phase 3) is stopped.
- 2022, LUMA and LIGHTHOUSE trials begin enrolling.
Sources
Last reviewed: 2026-06-23. Back to the Parkinson's drug pipeline