Understanding Lecanemab: A Newly Approved Treatment for Early Alzheimer's Disease

Dementia, a condition characterized by a gradual decline in memory and thinking skills, has become the leading cause of death in Australia. Among its various types, Alzheimer's disease accounts for approximately 60% to 80% of cases. Recently, Australia's Therapeutic Goods Administration (TGA) approved a new medication called lecanemab, marketed as Leqembi, for early-stage Alzheimer's disease, following the earlier approval of a similar drug, donanemab.

Lecanemab belongs to a class of drugs known as monoclonal antibodies. These laboratory-produced proteins are designed to target specific molecules—in this case, amyloid beta proteins that form microscopic plaques in the brains of Alzheimer's patients. Normally, our immune system produces antibodies to combat foreign invaders like bacteria and viruses. Monoclonal antibodies mimic this process by binding to specific targets, facilitating their removal by the immune system, which may help in reducing amyloid buildup.

The drug’s effectiveness was demonstrated through a large clinical trial involving 1,734 participants over 18 months. The study, funded by the pharmaceutical company Eisai, revealed that patients receiving lecanemab experienced a 27% slower progression of cognitive decline compared to those on a placebo. This reduction translated to about five months’ less deterioration over the 18-month period, measured by the Clinical Dementia Rating Scale. Continued treatment has shown evidence of sustained benefit for up to four years. Additionally, scans indicated significant reductions in brain amyloid levels, with most participants reaching levels below the Alzheimer's disease threshold. However, it's important to note that lecanemab does not reverse existing symptoms.

Safety concerns have been raised, prompting regulatory scrutiny. Approximately 12.6% of trial participants on lecanemab experienced brain swelling, a side effect more common in individuals carrying the ApoE4 gene. Some also experienced microhemorrhages, or small brain bleeds. Certain side effects, like headaches and dizziness, were mild, but severe cases including brain bleeds have been reported, especially in those on blood-thinning medications. Because of these risks, patients require regular MRI scans to monitor brain health. The safety and long-term outcomes data have been updated to four years, which was part of an appeal following initial rejection by the TGA.

Cost is another critical factor. Currently, lecanemab is not subsidized by Australia's Pharmaceutical Benefits Scheme (PBS) and costs approximately A$40,000 annually. The treatment involves biweekly doses for 18 months, followed by monthly maintenance, alongside ongoing monitoring expenses such as doctor visits and scans. The Pharmaceutical Benefits Advisory Committee has yet to approve PBS listing, citing concerns over the benefits versus costs. Similar drugs like donanemab face the same hurdles.

In summary, lecanemab offers a promising avenue for slowing early Alzheimer's progression, but it is not a cure. Its benefits are limited to early stages and are accompanied by significant safety considerations and high costs. Early diagnosis remains crucial. If you or your loved ones notice signs such as frequent short-term memory loss or confusion, consult a healthcare professional promptly to explore available options.

While lecanemab may help delay the advance of Alzheimer's, it does not improve existing symptoms or benefit those with later-stage disease. Ongoing research and careful assessment of risks and costs are essential as this new treatment becomes available.

Source: https://medicalxpress.com/news/2025-09-lecanemab-newly-alzheimer-drug-dementia.html