Biogen Shares Climb on New LEQEMBI Alzheimer's Data
Data from the CTAD 2025 conference confirms the drug's direct impact on neurotoxic proteins, bolstering confidence in its mechanism of action amid fierce market competition.
Biogen Inc. (BIIB) shares advanced Tuesday after the biotechnology firm and its partner Eisai presented new data that, for the first time, confirms their Alzheimer's drug LEQEMBI directly engages with a key neurotoxic protein in the nervous system. The findings, unveiled at the Clinical Trials on Alzheimer’s Disease (CTAD) conference in San Diego, provide critical validation of the drug's underlying mechanism and could strengthen its position in an increasingly competitive market.
Shares of Biogen climbed 1.35% to $180.18 in afternoon trading, pushing the stock near its 52-week high. The data appears to be reinforcing investor confidence in LEQEMBI's role as a cornerstone of the company's growth strategy.
The new analysis from a sub-study of the pivotal Phase 3 Clarity AD trial showed a statistically significant effect on amyloid-beta (Aβ) protofibrils, the toxic protein aggregates believed to be a primary driver of cognitive decline in Alzheimer's disease. According to the company's announcement, treatment with LEQEMBI resulted in a marked increase in the concentration of these protofibrils in the cerebrospinal fluid (CSF). This suggests the drug is actively binding to the toxic proteins in the brain and clearing them into the spinal fluid, a long-held hypothesis that now has direct clinical evidence.
The effect was substantial, with a 59% increase in CSF protofibril concentration in the LEQEMBI group at 12 months, compared to a 19% increase in the placebo group. The result carried a high degree of statistical significance (p=0.0126), providing a robust answer to questions about the drug's method of action.
This scientific validation is crucial for Biogen as it battles for market share against Eli Lilly, whose own Alzheimer's treatment, donanemab, competes directly with LEQEMBI. With both drugs targeting amyloid plaque, granular data that differentiates their effects and reinforces their efficacy is a key tool for persuading physicians and health systems.
The news comes at an opportune time for the anti-amyloid class of treatments. Just last month, the field received an indirect boost when Novo Nordisk announced that its widely-used GLP-1 drug failed to show a benefit in Alzheimer's trials. Analysts at the time noted this removed a potential competitive threat and solidified amyloid-targeting therapies as the primary disease-modifying option available to patients.
Biogen's commercial strategy for LEQEMBI is multifaceted, focusing on both robust clinical data and improved patient convenience. The company recently launched a subcutaneous auto-injector version of the drug for weekly maintenance dosing, a move designed to make the treatment more accessible than intravenous infusions. The company reported global LEQEMBI sales of $121 million in the third quarter of 2025, an 82% year-over-year increase, signaling growing momentum.
With a market capitalization of approximately $26 billion, Biogen is navigating a critical transition period, relying on new products like LEQEMBI and the spinal muscular atrophy drug Spinraza to offset declining revenue from its older multiple sclerosis franchise.
Investors will now be watching closely to see how this new data translates into prescription trends and sales figures in the coming quarters. While the scientific validation is a significant step, the ultimate success of LEQEMBI will be determined by its real-world adoption by doctors and patients navigating the complexities of Alzheimer's care. The detailed findings from the CTAD conference provide Biogen with a more compelling narrative as it seeks to establish LEQEMBI as a standard of care in a market projected to be worth billions.