Jan 27 (Reuters) - The U.S. Food and Drug Administration

has approved monthly maintenance dosing for Japan's Eisai ( ESALF )

and partner Biogen's Alzheimer's drug Leqembi,

the companies said on Monday.

The drug received

standard U.S. approval

in 2023 after showing it slowed cognitive decline in

patients with the brain-wasting disease but growth has been

slow, in part because its administration is time-consuming and

it requires regular MRIs and screenings.

Patients can switch to a monthly dose after having received

an intravenous infusion of the drug every two weeks for 18

months, the companies said in a joint statement. They can also

continue to dose once every two weeks.

Leqembi clears sticky deposits of a protein called

amyloid beta in the brain, believed to be a hallmark of

Alzheimer's disease. Patients receive the drug at an infusion

center in almost an hour-long process.

The companies said that modeling simulations of trial data

predicted that maintenance dosing would maintain benefits of the

therapy.

A rival drug from Eli Lilly ( LLY ), Kisunla, was

approved in July and is given by infusion once a month. Patients

stop taking the treatment once brain scans no longer show

amyloid plaques.

Both drugs have safety warnings regarding the potential for

brain swelling and bleeds. Patients are recommended to undergo

monitoring with scans.

Eisai ( ESALF ) has a collaboration agreement with BioArctic

on the drug.