Leqembi and Kisunla: Two Years Later, What Have We Actually Learned?

In the world of neurodegeneration, we mark time by the "before" and the "after." For twenty years, we lived in the "before"—an era where our only tools were medications that masked symptoms without touching the underlying disease. Then, in 2023 and 2024, the landscape shifted. With the arrival of Leqembi (lecanemab) and Kisunla (donanemab), we entered the "after."

I have long maintained that these drugs represent a monumental leap forward—not because they are "cures," but because they finally prove that the biology of Alzheimer's is a target we can actually hit. Now that we have roughly two years of "real-world" data, it is time to look at the facts: what are these drugs, why do they matter, and what is actually happening in the exam room as of March 2026?

The Mechanism: Why These Meds Changed the Conversation

To understand the progress, we have to look at what these drugs actually do. Alzheimer's is characterized by a buildup of amyloid-beta proteins that clump together into "plaques." For decades, we theorized that if we could clear these plaques, we could slow the destruction of neurons.

Leqembi and Kisunla are monoclonal antibodies. Think of them as precision-guided missiles programmed to seek out and bind to amyloid. Once they latch on, they signal the body’s own immune system to come in and "clean up" the debris. In clinical trials, this translated to a 27% to 35% slowing of cognitive decline.

Real-World Evidence: The March 2026 Check-In

Now that these therapies have moved from controlled trials to community clinics, several key insights have emerged:

1. The "Stability" Factor

Recent real-world data from over 3,000 patients shows that the drugs are performing remarkably well. We are seeing roughly a 37% slowing in the risk of progressing to the next stage of the disease. Most impressively, for patients caught in the very early "low tau" stage, up to 69% had no further cognitive decline at all over four years of treatment, which dates back from present to the initial enrollment of the clinical trials.

2. The Early Window is Non-Negotiable

The data is clear: these drugs are highly time-sensitive. They are designed for the Mild Cognitive Impairment (MCI) or Mild Dementia stages. We are catching patients earlier now because we finally have high-accuracy blood-based biomarkers (like p-tau217) that tell us who is a candidate.

3. The ARIA Reality (Safety Profile)

The biggest hurdle remains ARIA (Amyloid-Related Imaging Abnormalities)—swelling or tiny micro-bleeds in the brain.

• The Good News: Most cases are asymptomatic and discovered only via mandatory MRIs.

• The Caveat: Patients with two copies of the APOE4 gene are at a higher risk. In 2026, genetic testing is a mandatory safety step.

  
  

4. The Shift to At-Home Convenience

As of January 2026, the FDA granted Priority Review for a subcutaneous (under the skin) version of Leqembi (Leqembi Iqlik). By May 2026, we expect full approval for at-home weekly autoinjectors, moving treatment away from the infusion center and into the living room (noting that it is notoriously difficult to predict FDA approval and clearance guidelines).

The Pillar Integration: No Drug is an Island

The most important thing we've learned is that these drugs do not work in a vacuum. A patient on Leqembi with uncontrolled diabetes or hypertension will not see the same benefits as a patient with an optimized Metabolic Engine. The medication clears the Toxic Load, but the patient's lifestyle maintains the Heart-Vessel & Brain Link.

Takeaways

• Timing is Everything: These meds are for the earliest stages only.

• Genetic Testing is Mandatory: Know your APOE4 status before starting.

• Home Administration is Coming: May 2026 is the target for at-home "pen" delivery for Leqembi.

• The "Stop" Criteria: With Kisunla, treatment can often stop once the amyloid is cleared.

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Citations and References

• BrightFocus Foundation (2026): Leqembi and Kisunla: Your Questions Answered.

• Eisai/Biogen (Jan 2026): FDA Accepts LEQEMBI® IQLIK™ Application for Subcutaneous Starting Dose.

• Washington University Medicine (2025): Next-gen Alzheimer's drugs extend independent living.