Eisai, Biogen Face Delay to Subcutaneous Leqembi

Why It Matters

The delay postpones a pivotal product advantage that could broaden Leqembi’s market share versus Eli Lilly’s Kisunla and defer revenue upside for Biogen and Eisai.

Key Takeaways

• FDA delays Leqembi Iqlik start-dose decision to Aug 24.
• Subcutaneous launch could boost US sales, previously $86 M Q1.
• 80% of patients stay on therapy at 18 months.
• Competitor Kisunla lacks home‑dose option, Biotech sees advantage.
• Lilly's next‑gen subcutaneous amyloid drug in Phase 3 trials.

Pulse Analysis

The FDA’s three‑month extension for Leqembi Iqlik reflects the regulator’s heightened scrutiny of novel Alzheimer’s therapies, especially those shifting from intravenous to subcutaneous delivery. While the agency has not flagged safety issues, the request for a major amendment signals a need for additional data on dosing, immunogenicity, and real‑world administration logistics. For Eisai and Biogen, securing approval for a home‑based starting dose is critical to differentiate Leqembi in a crowded anti‑amyloid market and to simplify the care pathway for patients and providers.

Leqembi’s recent performance illustrates both the promise and challenges of Alzheimer’s biologics. Q1 sales climbed 74% to $168 million, driven largely by U.S. uptake, yet the drug’s modest efficacy and side‑effect profile have limited broader adoption. Retention data—nearly 80% of patients remaining on therapy at 18 months—suggests that once patients are on board, adherence is strong, likely due to the disease’s progressive nature and limited alternatives. A subcutaneous starter dose could lower infusion‑center burdens, reduce costs, and attract clinicians who currently favor Eli Lilly’s Kisunla, which, despite a fixed treatment duration, benefits from a simpler IV regimen.

Looking ahead, the competitive landscape is poised to evolve. Lilly is not pursuing a subcutaneous version of Kisunla but is advancing a next‑generation amyloid‑targeting candidate, remternetug, in Phase 3 trials. If successful, it could re‑ignite the race for home‑administered Alzheimer’s treatments, pressuring Biogen and Eisai to accelerate their own data submissions. The outcome of the FDA review will therefore shape not only Leqembi’s revenue trajectory but also broader industry dynamics, influencing investment decisions and the strategic focus on patient‑centric delivery models in neuro‑degenerative care.