Biogen and Denali Therapeutics’ LRRK2 inhibitor has flunked a Phase 2b trial in early Parkinson’s disease, leading the companies to drop the program in certain patients.
The small-molecule drug, known as BIIB122, missed the study’s primary endpoint of slowing time to disease progression compared with placebo, as measured by time to worsening in the modified Movement Disorder Society Unified Parkinson’s Disease Rating Scale.
Biogen also said in a Thursday
release
that no benefit was seen in the secondary endpoints, such as change from baseline in disability and impairment scores. The company didn’t share numbers.
The Phase 2b enrolled almost 650 adults with early-stage disease, including those with and without an LRRK2 mutation. These genetic mutations cause the LRRK2 protein to become overactive, which is believed to damage dopamine-producing neurons and trigger Parkinson’s symptoms.
Other study results suggested that BIIB122 did successfully hit its target. The drug led to a greater than 90% kinase inhibition of peripheral LRRK2, as well as a 30% drop in a biomarker of LRRK2 activity in spinal fluid called phosphorylated Rab10.
Biogen said it plans to present full results from the trial at an upcoming medical meeting.
Biogen and Denali are discontinuing BIIB122 for idiopathic Parkinson’s, which describes forms of the disease with no known genetic driver. Denali is still running a separate Phase 2a study of the candidate in patients with an LRRK2 variant. The trial, known as BEACON, is set to have data in the first half of 2027.
Jefferies analysts wrote Thursday that Denali’s decision to continue with BEACON has made them “curious if there was a subtle signal in the LRRK2-variant patient subgroup” of the failed Phase 2b trial.
Denali’s stock
$DNLI
dipped 7% before market open Friday, while Biogen’s
$BIIB
was down 1%.
This is not the first time Biogen has ended an LRRK2-targeting program. In 2025, the company dropped an antisense oligonucleotide called BIIB094 that was partnered with Ionis Pharmaceuticals as part of a
broader portfolio prioritization
. Denali, meanwhile, deprioritized an LRRK2-directed small molecule drug called DNL201 in 2020 to
focus
on advancing BIIB122.
Biogen and Denali first started working together on Parkinson’s in 2020, when they signed a deal that saw Biogen
pay over $1 billion
split between upfront cash and stock purchases.
Elsewhere, Neuron23’s bet in Parkinson’s is an LRRK2 inhibitor called NEU-411, which is in a Phase 2 study. The trial is selectively enrolling patients with LRRK2-driven disease.