Elan Corporation has announced a new research agreement, the second this year, in its quest for a treatment for Alzheimer's Disease. This latest is with Pharmacia Corporation and will complement a research link-up with American Home Products Corporation via its Wyeth subsidiary.

The Dublin-based company has three divisions. Elan Pharmaceutical Technologies employs 400 researchers on its site in Trinity College where it conducts advanced work on drug delivery. Its worldwide pharmaceutical manufacturing base, Elan Pharmaceutical Operations, is in Athlone.

Its third division is Elan Pharmaceuticals which specialises in neuroscience, pain and cancer research via recent company acquisitions.

In 1996 Elan bought Athena Neurosciences Corp and Neurex Corp, both of San Francisco and this year it bought the Liposome Company of Princeton, New Jersey.

Alzheimer's Disease is a devastating condition, both for the sufferer and also for close family and friends. The patient's memory slowly degrades to the point where they may be unable to recognise their spouse or children. This is profoundly upsetting for the very people who visit the patient in hospital and who might eventually become nothing more than a pleasant stranger. The disease itself is progressive and irreversible. It is the single most common cause of dementia, a general term for a decline in mental ability. It is responsible for 75 per cent of dementia cases in people over 65.

Recent research has shown that there is a strong genetic component to the onset of the disease. Alzheimer's in later life in particular seems to be associated with mutations in three genes that produce certain proteins in the blood.

The genes are associated with protein substances known as beta amyloid which are produced in the brain. This material becomes deposited as "plaques" on essential brain tissues, blocking their function and bringing on a cascade of neurological symptoms which become progressively worse over time.

The company is attempting to open up several research pathways on the road to a cure for Alzheimer's Disease, and this is reflected in the research alliances it has announced.

This approach serves to bolster share value but also protects against collapsing values should one of the pathways prove unusable.

The arrangement with Wyeth/ American Home Products involves the development of a vaccine against the disease that uses an amino acid developed by Elan called AN-1792.

This vaccine has been shown in mice to reduce pre-existing plaque on brain tissues and to inhibit further plaque formation.

AN-1792 is now undergoing "phase I" human trials in Britain and the US. The initial tests will show if it can help patients. Phase II trials involving larger numbers would come next year if these early trials succeeded.

The deal with Pharmacia Corp involves a different research tack based on blocking the action of an enzyme called "beta secretase". This enzyme enables a key step in the process that leads to the formation of amyloid plaques.

The companies have identified a chemical that can interfere with beta secretase, and this hopefully would either stop or slow the plaque process.

Significantly the new chemical is a relatively small molecule, an important consideration in drug delivery.

Large, complex drug molecules often won't pass through the stomach intact and have to be injected. Small molecules more readily survive the stomach and so can be taken orally, which in turn makes the drug easier to take.

There are 34,000 individuals registered with dementia in Ireland and Alzheimer's patients make up the largest group within this total.

There are an estimated four million Alzheimer's sufferers in the US and this is expected to more than treble by 2025 given today's longer lifespan.

In addition the Alzheimer's Society of Ireland estimates that the disease costs families in the US between $80 billion (€89 billion) and $100 billion a year for medical care, medication and home help.

Any safe and effective drug that could negate these costs and deliver better quality of life for patients would therefore be worth a fortune, certainly hundreds of millions of dollars if not more.

It will be some time before these profits can be realised however. Elan estimates that its AN1792-based treatment approach won't be on the market before 2006 and possibly as late as 2010.

It will have to pass through a battery of tests to prove its effectiveness and its long-term safety before it can be given to patients on a regular basis.

This can only be done following large-scale, long-term human trials.