Leqembi Wanted to Ditch the IV. The FDA Just Hit Pause.

The subcutaneous version is supposed to fix all of this.

What's Already Approved (and What Isn't)

This is where it gets a little layered, so let's break it into two pieces.

Already approved: In August 2025, the FDA greenlit Leqembi IQLIK as a 360 mg weekly subcutaneous injection for maintenance. That means after you finish the grueling 18-month IV induction, you can switch to a simple weekly shot at home. Think of it like finishing physical therapy at the clinic and then doing your exercises at home.

Not yet approved: The pending application is for a 500 mg weekly subcutaneous starting dose (delivered as two 250 mg injections, each taking about 15 seconds). If approved, patients could skip the IV entirely and do the whole treatment course at home from the start.

That second piece is the game-changer. Jefferies analyst Michael Yee has characterized the SC maintenance approval as a "nice to have" but called SC induction "critical" for maximizing the franchise's value. Getting patients started at home, not just finishing at home, is what could truly unlock adoption.

The Data Looks Solid

From a science perspective, the subcutaneous version checks the important boxes. Weekly 500 mg shots achieved plasma exposure comparable to IV dosing, and the 90% confidence interval for drug exposure fell within the standard bioequivalence window of 80–125%.

In Eisai's open-label extension studies, patients starting on subcutaneous Leqembi actually showed about 14% greater amyloid plaque removal at six months compared to IV patients. The safety profile looked similar too, with systemic injection reactions occurring in less than 2% of participants.

The drug still carries a boxed warning for ARIA (amyloid-related imaging abnormalities, essentially brain swelling or microbleeds that can occur when you clear amyloid). Patients will still need MRI monitoring regardless of how they receive the drug. But they won't need to drive to an infusion center twice a month.

The Competitive Chess Match

Leqembi doesn't exist in a vacuum. Eli Lilly's Kisunla (donanemab), approved in July 2024, is the main rival. Both drugs target amyloid plaques in early Alzheimer's, but they play the game differently.

Kisunla's pitch is "treat and done." It's an IV infusion once a month, and about 70% of patients can stop treatment entirely around 18 months once their amyloid PET scans come back clean. No indefinite maintenance. Lilly prices it at roughly $32,000 per year, compared to Leqembi's $26,500 for IV (and about $19,500 for the subcutaneous version).

Leqembi's counter-pitch is convenience through route of administration. Once SC induction is approved, the entire treatment journey could happen at home. No infusion center, no IV lines, no monthly hospital visits. For a patient population that struggles with transportation and caregiver logistics, that's a powerful argument.

Leqembi held roughly 67% of the anti-amyloid market in 2024, helped by its earlier approval and more established clinical pathways. The SC advantage could widen that lead.

But Lilly isn't standing still. Its next-generation candidate, remternetug, is in Phase 3 trials with both SC and IV options built in from the start. If it works, Lilly could match Leqembi's convenience while keeping the "finite course" appeal of donanemab.

What Happens Next

The anti-amyloid antibody market represents a massive prize, and how patients actually receive these drugs will determine who captures it.

The August 24 PDUFA date is now the binary event that analysts are circling on their calendars. A positive decision would mean Leqembi can be prescribed as an entirely at-home therapy.

For patients and their families, the stakes are simpler. Every two weeks, someone with early Alzheimer's has to organize a ride, sit in a clinic, and endure an infusion that reminds them they're sick. A 15-second shot at the kitchen table won't cure the disease. But it might keep a lot more people on the treatment that slows it down.

Three more months of waiting. For a drug designed to fight a disease that steals time, the irony stings.