The case is the latest in a series of legal challenges to Britain's National Health Service, which offers free health care and low-cost medicines to all Britons — but is regularly accused of rationing access to treatment.
Drug companies Eisai Co. Ltd. and Pfizer Inc., along with the Alzheimer's Society, want to overturn a decision by the government's medicines watchdog not to approve a group of drugs known as acetyl cholinesterase inhibitors for patients in early stages of the disease.
The National Institute for Health and Clinical Excellence (NICE), which regulates use of prescription drugs, recommended last year that three drugs — donepezil, rivastigmine and galantamine — not be prescribed for patients with early stage Alzheimer's.
It said the treatment was not particularly effective for people with mild Alzheimer's and at about 2.50 pounds ($5) per patient, per day was not cost effective. It recommended the drugs for patients with moderate-stage Alzheimer's.
"The reality is that, for Alzheimer's disease, drugs are only part of the care that needs to be offered," said Andrew Dillon, chief executive of NICE.
"Non-drug interventions have an important part to play and the evidence indicates that drugs are simply not effective for some patients."
The companies and the Alzheimer's Society accuse NICE of telling patients they must get worse before they can be treated.
Eisai's lawyer, David Pannick, told the court that the decision meant "that the opportunity is lost for delaying the onward march of this appalling disease and maintaining a relatively good quality of life for patients for as long as possible."
Several Alzheimer's patients and their supporters sat in the public gallery at the start of the four-day High Court hearing.
Bob Noble, 58, said the drugs had been like "a stay of execution" after he was diagnosed two years ago.
"The drugs give me a way forward, to rebuild my life to an acceptable level," he said. "It is absolutely critical. Without the drugs I would not be capable of looking after myself.
"They are being unfair because they are discriminating against young people, newly diagnosed, by not approving drugs that would give them a good quality of life."
Last year NICE agreed to widen use of the breast cancer drug Herceptin after several patients went to court demanding treatment with the drug.