Solanezumab and Alzheimer’s

If you had been sitting in the main room of the 2015 Alzheimer's association international conference, you would have heard a remarkable announcement: a drug - Solanezumab - has been found to delay the course of Alzheimer's disease. Now that is a rare thing - 99.6% of all drugs designed to combat Alzheimer's have failed in trials since 2002. Just four have been approved for use. None of those four target the underlying cause of the disease (they just ameliorate the symptoms). But Solanezumab claims to be different.

The “plaques” and “tangles” found in the brains of Alzheimer’s patients are caused by two proteins behaving abnormally; beta-amyloid is thought to usually be involved in neuronal development, but in many Alzheimer’s patients the protein is not processed properly. The incorrect processing leads to a build-up of large amounts of beta-amyloid as the protein loses its solubility. The higher concentrations lead to this protein creating large aggregates known as “plaques”. “Tangles” are instead caused by the protein “tau”, which in Alzheimer’s patients has too many phosphate groups added to the protein, this makes tau clump together within the nerve cells.^[3] Image credit: National Institute on Aging (public domain)

Alzheimer's disease - the causes and consequences

Alzheimer’s disease is the most common form of dementia and affects almost half a million people in the UK alone - and the number is rising^[1]. Typical symptoms of Alzheimer’s include lapses in memory, mood swings, and difficulties performing everyday activities^[1], but the exact symptoms a patient will display are unique to the individual. The only thing that is consistent between all Alzheimer’s patients is the debilitating effects this disease has on the patient and their quality of life. Many patients suffer from extreme memory loss, losing the ability to recognise friends and loved ones. Some patients even lose the ability to feed themselves and rely on carers and family members for basic life skills that we take for granted.

Despite being identified in the early 20^th century, we are still not exactly certain why some of us will develop Alzheimer’s while others will not. Our brains are complex organs that provide us with memories, personalities and make each individual unique; any disease that affects this vital organ can lead to drastic changes in someone’s life. Alzheimer’s is no different; it’s a progressive disease meaning the damage to the brain worsens over time, leading to more pronounced symptoms and deterioration in a patient’s condition^[1].

Auguste Deter was the first person to be diagnosed with Alzheimer’s disease, in 1901. She died in 1906, aged 55. Photograph by unknown photographer, 1902. (Public domain)

There are many aspects of Alzheimer’s that makes finding a cause, and indeed a cure, more difficult. For example, Alzheimer’s is unique to each individual patient depending on which part of the brain is affected. There are many different types of dementia, of which Alzheimers is only one, and differentiating between them is difficult because the symptoms are similar and can be very vague in the early stages, and similar to other conditions such as depression. We’re currently able to diagnose Alzheimer’s with 90% accuracy; it’s impossible to achieve 100% without dissecting the brain itself ^[2], although other diagnosis methods are rapidly catching up!