After filing hitch, Eisai and Biogen begin rolling FDA submission for subcutaneous Leqembi

After suffering a setback with U.S. regulators last month, Eisai and Biogen’s effort to deploy a more convenient version of their Alzheimer’s disease drug Leqembi appears to be back on track.

Late Tuesday, the partners said they kicked off a rolling FDA submission for the subcutaneous version of Leqembi—which is currently infused—after securing a fast track designation from the agency.  

If approved, the under-the-skin formulation would be used to deliver weekly maintenance doses of the amyloid-busting antibody at home or in medical facilities following a biweekly infused initiation phase, Eisai and Biogen said in a release.

The partners believe that the Leqembi autoinjector could help slash the time Alzheimer’s patients spend in infusion chairs and alleviate the burden on caregivers, too, potentially reducing the need for hospital visits and nursing care compared to the drug’s current intravenous administration route.

Analysts and industry watchers have previously pointed to subcutaneous Leqembi as a potential inflection point for the drug, both in terms of patient convenience and future sales.

Leqembi—which won a full FDA approval last summer—has seen its uptake hampered thanks to complicated logistics around diagnosis and treatment. Back in February, Eisai indicated that it was unlikely to meet its goal of reaching 10,000 patients with the drug by the end of its 2023 fiscal year, which wrapped up on March 31.

At the time, Eisai noted in an earnings presentation that just 2,000 patients in the U.S. were receiving Leqembi as of Jan. 26, with another 8,000 or so waiting in the wings, according to the company’s global Alzheimer’s disease officer, Keisuke Naito.

“We believe that as the diagnosis and the treatment pathways are established and implemented … then we will be able to administer Leqembi to these patients,” Naito said, adding that his company expected the number of patients who can receive Leqembi to “increase rapidly” in the coming months.

In early April, the FDA put a damper on Eisai and Biogen’s hopes for subcutaneous Leqembi when the agency forced a filing delay by requesting additional three-month immunogenicity data on the drug’s under-the-skin formulation.

Eisai, which leads development and regulatory work on Leqembi, had originally planned to start a rolling submission for the subcutaneous formulation in March, assuming it could do so under the existing fast-track tag for the infused version of the antibody. The FDA had other ideas and set a 60-day timeframe to decide on whether to grant the designation.

The subcutaneous Leqembi application is now cleared for a rolling submission is based on data from the open-label extension of Eisai’s Clarity AD study, plus modeling of observed data, Eisai and Biogen explained in their latest release.

Last fall, the partners showcased data from that phase 3 study that indicated a subcutaneous injection of Leqembi cleared 14% more amyloid plaque in the brain than the infused version among 71 patients who hadn’t received the drug before. That said, the rate of side effect amyloid-related imaging abnormalities was slightly higher for the drug’s injectable form.

Companies that win fast track designation for their drugs often enjoy more frequent meetings and written communication with the FDA, plus the potential for their candidates to snare an accelerated approval or priority review.

Filing interruption aside, Eisai and Biogen currently have the Alzheimer’s field all to themselves after the FDA in March delayed its approval decision on Eli Lilly’s would-be rival donanemab.

Earlier this month, Lilly revealed that it will be going to bat for its Alzheimer’s candidate at a June 10th meeting of the FDA’s Peripheral and Central Nervous Systems Drugs Advisory Committee. Lilly execs in April told Fierce Biotech that the voting questions will likely come down to labeling.

Enjoying a bit more breathing room thanks to the Lilly delay, Biogen in late April unveiled plans to grow its Leqembi field force in the U.S. by 30% as it works with Eisai on direct-to-patient and caregiver-specific marketing campaigns.

Over the first three months of 2024, Biogen reported global Leqembi sales of $19 million, nearly triple what the therapy made in the final quarter of 2023.  New starts in March represented more than 20% of the patients now on the drug, Biogen added.