I'm LongbridgeAI, I can summarize articles.Biogen's stock fell 4.97% to $194.37 after mixed Phase 2 results for its Alzheimer's therapy, diranersen, which showed cognitive benefits but missed its primary endpoint. Analysts remain optimistic about its potential, noting significant reductions in tau biomarkers. Additionally, Biogen completed its acquisition of Apellis Pharmaceuticals, adding two commercial drugs to its portfolio, expected to enhance revenue growth and EPS by 2027.
Biogen Inc. (NASDAQ:BIIB) on Thursday reported topline Phase 2 results for diranersen (BIIB080), its investigational tau-targeting antisense oligonucleotide therapy for early Alzheimer’s disease, highlighting cognitive benefits and reductions in tau biomarkers despite missing the study’s primary endpoint.
The stock fell following the announcement. Despite the decline, the outcome is viewed as mixed, as Biogen said it still plans to advance diranersen to registrational development after the drug delivered strong reductions in toxic tau biomarkers across all tested dose levels. Separately, the company also confirmed it completed its acquisition of Apellis Pharmaceuticals, Inc. (NASDAQ:APLS) on Thursday.
The company said the CELIA study marked the first randomized Phase 2 trial of a tau-directed therapy to show both biomarker impact and signs of cognitive benefit in patients with early Alzheimer’s disease.
Cognitive Decline Slowed Across Doses
Biogen said pre-specified analyses showed slowing of clinical decline across all tested doses of diranersen.
The effect appeared strongest in patients receiving the lowest dose, 60 mg administered every 24 weeks.
The therapy also demonstrated reductions in cerebrospinal fluid tau levels and tau pathology measured through positron emission tomography scans across all dose groups.
However, CELIA did not achieve its primary endpoint, which evaluated dose response for change from baseline on the Clinical Dementia Rating–Sum of Boxes (measures cognitive and functional impairment) scale at Week 76.
The safety and tolerability profile of diranersen across all studied doses was generally consistent with the Phase 1b study and the known profile of diranersen to date.
In December 2019, Biogen exercised a license option with Ionis Pharmaceuticals Inc. (NASDAQ:IONS) and obtained a worldwide, exclusive, royalty-bearing license to develop and commercialize diranersen.
Analysts Highlight Potential Despite Trial Miss
William Blair wrote Thursday, “We did not view meeting the primary endpoint as a requisite for advancing development. Instead, we are cautiously optimistic to see that the slowing of cognitive decline was observed across all studied doses and in the lowest dose (diranersen 60 mg administered every 24 weeks), where the benefit was highest.”
Analyst Myles Minter further wrote that follow-up discussions with management implied the result likely reached nominal statistical significance. He added that efficacy in the range of anti-amyloid therapies — roughly 27% to low-30% slowing of cognitive decline versus placebo — appeared to be a reasonable goal, although the magnitude of the benefit will not be disclosed until the Alzheimer’s Association International Conference.
Biogen Closes Apellis Deal, Adds Two Commercial Drugs
Separately, Biogen announced it completed the acquisition of Apellis Pharmaceuticals adding EMPAVELI and SYFOVRE to its portfolio and expanding its nephrology business.
The two drugs generated combined net product revenue of $689 million in 2025. Biogen said the deal is expected to boost revenue growth and become accretive to non-GAAP diluted EPS in 2027.
Under the transaction terms, Apellis shareholders received $41 per share in cash plus a contingent value right tied to future SYFOVRE sales milestones. About 82.4% of Apellis shares were tendered, and the stock has stopped trading on Nasdaq.
BIIB Price Action
BIIB Price Action: Biogen shares were down 4.97% at $194.37 at the time of publication on Thursday, according to Benzinga Pro data.
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