A New Alzheimer's Drug Is Going After a Different Target. Here Is Why Scientists Are Paying Attention

A New Alzheimer's Drug Is Going After a Different Target. Here Is Why Scientists Are Paying Attention

If someone in your family has Alzheimer's, you have probably already heard of amyloid, the sticky protein that most existing drugs try to clear from the brain. A new Alzheimer's tau drug is taking a different route, and the early results are turning heads in a field that has mostly chased the same target for decades.

What Is Tau and Why Does It Matter

Alzheimer's involves two proteins that damage the brain over time. Amyloid builds up into plaques years before symptoms show. Tau forms tangled clumps inside brain cells, and unlike amyloid, tau buildup lines up closely with when memory loss actually starts and how fast it progresses. Most researchers think amyloid buildup eventually triggers tau to spread, roughly when symptoms begin.

Amyloid-clearing drugs are already approved in the US and show modest benefit early on. Diranersen, developed by Biogen with Ionis Pharmaceuticals, is a tau protein Alzheimer's drug instead, the subject of new results presented at the Alzheimer's Association International Conference this month.

How Diranersen Actually Works

Diranersen belongs to a drug class called antisense oligonucleotides: instead of clearing tau after it builds up, these drugs tell the gene that makes tau to produce less of it in the first place. Dr. Cath Mummery of University College London, who led the research, explained that lowering tau production leaves less abnormal tau for the brain's natural clearance system, called microglia, to keep up with, giving it more room to work. The drug is injected into the fluid around the spinal cord, a more direct route to the brain than the IV infusions used for amyloid drugs.

What the Study Actually Showed

The trial, in roughly 400 people with mild cognitive impairment or early Alzheimer's, found the lowest dose (given every six months) reduced tau levels and was tied to about a 26 percent slowing of cognitive decline on one measure, in a similar range to earlier amyloid drugs. Side effects included injection site pain and temporary confusion lasting about a week. One encouraging sign: no cases of brain swelling, a side effect seen with some amyloid drugs.

Where This Actually Stands Right Now

Diranersen is not approved in Canada and is not available as a treatment here. These are mid-stage results that still need confirmation in larger, longer trials before any regulator considers approval. Other anti-tau efforts are gaining momentum too: the University of California, San Francisco recently opened an Alzheimer's Tau Platform, funded by the US National Institutes of Health, testing several tau-targeting therapies. Dr. Reisa Sperling of Mass General Brigham, unconnected to this study, told reporters these results should help pull more research investment back toward tau.

None of this changes anything for someone managing Alzheimer's today. But for the estimated 600,000 Canadians currently living with the disease, it is a real signal that more than one biological path forward exists.

What is the difference between amyloid and tau in Alzheimer's disease?

Amyloid forms plaques that build up years before symptoms start. Tau forms tangles inside brain cells and is more closely tied to when memory loss and decline actually begin. Most approved drugs target amyloid; diranersen is one of the first serious attempts to target tau.

Is diranersen available in Canada?

No. It has not been approved by Health Canada or any regulator and is only available through clinical trials. These mid-stage results would need confirmation in larger trials before approval could be considered.

How is diranersen given to patients?

It is injected into the fluid around the spinal cord, roughly every six months at the lowest dose tested. That is a more direct route to the brain than the IV infusions used for current amyloid-targeting drugs.

This article is general health information, not medical advice, and no one should start or stop an Alzheimer's medication based on it. If you have concerns about memory or cognitive changes, a family doctor or neurologist can help. If you are trying to sort out normal age-related forgetfulness from something worth checking, Medimap's guide to a quick at-home memory test walks through what a screening actually involves. Find a provider at medimap.ca, or browse more explainers on the Health Hub.