Biogen Inc. (BIIB) and its partner Eisai are trying to make Alzheimer's treatment a whole lot easier. On Friday, Eisai filed an application with Japan's Pharmaceuticals and Medical Devices Agency seeking approval for a subcutaneous autoinjector version of Leqembi (lecanemab), which would let patients take their medication at home instead of trekking to the hospital every couple weeks.

Here's why this matters: Right now, Leqembi requires intravenous infusions every two weeks at a healthcare facility, complete with infusion preparation, nurse monitoring, and all the logistics that come with that. The new subcutaneous formulation would be a once-weekly injection patients could give themselves at home. Two quick shots, 15 seconds each, and you're done.

The filing draws on data from multiple subcutaneous administration sub-studies conducted as part of the Phase 3 Clarity AD open-label extension, which followed the 18-month core study in people with early Alzheimer's disease or mild stage Alzheimer's dementia.

The results looked solid. Once-weekly administration of the 500mg subcutaneous autoinjector produced equivalent drug exposure to the biweekly IV infusions, with similar clinical benefits and biomarker outcomes. Safety-wise, the subcutaneous version performed comparably to IV administration, showing less than 2% incidence of systemic injection or infusion-related reactions.

If Japan's regulators sign off, patients could start treatment immediately with the at-home weekly shots rather than committing to hospital visits for IV infusions. Beyond patient convenience, the subcutaneous formulation could ease the burden on healthcare systems by eliminating the need for infusion preparation and nursing supervision, potentially streamlining the entire Alzheimer's treatment pathway.

The push isn't limited to Japan. Earlier this week, Biogen and Eisai completed their rolling submission of a Supplemental Biologics License Application to the U.S. Food and Drug Administration for the same subcutaneous autoinjector formulation.

Biogen shares slipped 0.24% to $181.50 on Friday, still trading close to the stock's 52-week high of $185.17.