Aug 22 (Reuters) - Alzheimer's patients in Britain's

state-run health service are unlikely to get access to Eisai ( ESALF )

and Biogen's new Leqembi drug, after it was

approved on Thursday by the country's regulator but deemed too

expensive for wide use.

The Medicines and Healthcare products Regulatory Agency said

the drug, also known as Lecanemab, is the first treatment for

Alzheimer's licensed for use in the country "that shows some

evidence of efficacy in slowing progression of the disease."

But in its draft guidance published simultaneously, the

National Institute for Health and Care Excellence said the

medicine's high cost and need for intensive monitoring for side

effects "means it cannot be considered good value for the

taxpayer".

The UK cost effectiveness body's findings mark the latest

blow faced by the drugmakers amid slow take-up of the drug in

the U.S. It also highlights the complexities of a new class of

drugs that benefit early-stage Alzheimer patients but could

cause rare and serious side effects.

The therapy for early Alzheimer's disease has been approved

in the United States, China, Hong Kong, Israel, Japan, South

Korea and the UAE.

But last month the European Union's drugs regulator rejected

the drug, saying the risk of serious brain swelling did not

outweigh its small impact on slowing cognitive decline.

The companies said then that they will seek re-examination

of the recommendation, but did not disclose what information

they would provide the regulator.