Does it work? Can homotaurine help to combat alzheimer's disease?

BACKGROUND:Alzheimer's disease is a devastating condition, both for those with it and for those caring for loved ones. The number of people with the condition is expected to triple over the next 40 years. Much remains uncertain about its cause and what happens as the person's memory and cognitive function deteriorate. Current drug treatments target neurotransmitters in the brain. These sometimes give modest, but temporary, improvements.

Homotaurine is a food supplement with a controversial reputation for preventing memory loss. The small organic compound is found in several types of seaweed. Last month, Italian scientists announced that homotaurine from seaweed had helped a number of patients with Alzheimer’s. Details have not been published, but homotaurine has already been on the market as a food supplement to prevent memory loss. Ironically, this form of homotaurine does not have natural origins, but is the result of 15 years of pharmaceutical research.

EVIDENCE FROM STUDIES

Homotaurine was developed to treat Alzheimer’s disease by a Canadian pharmaceutical company. Alzheimer’s appears to cause problems involving two brain proteins which undergo abnormal changes. One of these, the amyloid or A-protein, is normally soluble and harmless. In Alzheimer’s patients it forms insoluble “plaques” in the brain which cause damage.

The Canadian company found that homotaurine could prevent insoluble A-protein plaques from forming in mice. It was given to patients and found to be safe, other than sometimes causing nausea and vomiting. A trial involving 58 Alzheimer’s patients again found it safe, but also found no clinical differences between patients taking homotaurine or placebo. However, the study lasted only 12 weeks as its purpose was to test safety, not whether the treatment was effective.

A large randomised controlled trial was conducted in North America, enrolling more than 1,000 patients with mild to moderate Alzheimer’s. After 18 months of treatment, no significant differences were found between those taking homotaurine and placebo. On this basis, the Food and Drug Administration denied approval of homotaurine.

Only parts of the studies have been published, with the manufacturers claiming some patients benefited. However, the primary findings were that patients’ memory and cognitive function were not protected by homotaurine.

A UNIQUE TWIST

Having failed to get approval as a pharmaceutical drug, the manufacturer decided to market the product as a food supplement. Under Canadian and US regulations, food supplements do not have to be shown to be effective. In addition, products cannot claim to prevent or treat diseases, so homotaurine is being marketed as something that protects memory function.

RECOMMENDATIONS

A product that has failed to show itself to be effective for Alzheimer’s is now being sold as a food supplement to protect healthy people from memory loss. Such are the ironies and contradictions found with homotaurine.

At the moment, the evidence is that homotaurine is no more effective than placebo. That is why it hasn’t been approved as a drug, and it won’t become effective just because it is sold as a food supplement.

Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University