Donanemab, an Alzheimer's disease drug from Eli Lilly (LLY.US), has been rejected by the UK's health regulator.

Donanemab, an Alzheimer's disease drug from Eli Lilly (LLY.US), will not be available to patients using the UK's National Health Service (NHS) because the cost regulator said the benefits were too small to justify the price.

The National Institute for Health and Care Excellence (NICE), which decides whether drugs should be made available to NHS patients, said in a draft guidance published on Wednesday that the cost and intensive testing required for the drug outweighed its relatively small benefits for patients.

Donanemab delayed the progression of Alzheimer's disease by four to seven months, according to clinical trials. "The cost-effectiveness estimates for Donanemab are five to six times higher than what NICE typically considers acceptable use of NHS resources," said Helen Knight, director of NICE's medicines evaluation.

Leqembi, a joint venture between Japan's Eisai and Biogen (BIIB.US), was also rejected by NICE for the same reason, that the drug's benefits were too small to justify its high cost.

Both drugs only modestly slow the progression of Alzheimer's disease, and are currently approved only for patients with early-stage Alzheimer's, a small fraction of the total number of people with the disease. Side effects include brain swelling and bleeding, which means patients need to be closely monitored, including with regular recent brain scans.

Fiona Carragher, chief policy and research officer at the Alzheimer's Society in London, said the NICE decision was "disappointing". "Over time, treatments for cancer and other diseases have become more effective, safer and cheaper, and we would hope to see similar progress in dementia treatment," she said.