Australia’s Therapeutic Goods Administration (TGA) has approved a new treatment for early Alzheimer’s disease, called lecanemab, marketed under the brand name Leqembi. This decision follows the earlier approval of a similar drug, donanemab, earlier this year. Lecanemab has shown promise in slowing the progression of the disease in patients diagnosed at an early stage, but its high cost could limit access for many Australians.
Alzheimer’s disease is the leading cause of dementia, accounting for approximately 60–80% of all cases. Dementia is increasingly recognized as a significant health crisis, now the most common cause of death in Australia. The introduction of lecanemab provides a new option for those facing this challenging condition, which affects memory and cognitive function.
Understanding Lecanemab’s Mechanism
Lecanemab is classified as a monoclonal antibody, a type of treatment designed to target specific proteins in the body. In the case of Alzheimer’s, lecanemab binds to the amyloid protein, a key marker associated with the disease. This action allows the immune system to clear amyloid from the brain, potentially mitigating further damage.
The approval follows a comprehensive clinical trial involving 1,734 participants over a period of 18 months, funded by the drug manufacturer Eisai. The trial demonstrated a notable slowing of disease progression among patients diagnosed with early Alzheimer’s or mild cognitive impairment. Those administered lecanemab exhibited a 27% reduction in disease progression compared to those given a placebo, equating to roughly five months less decline on the Clinical Dementia Rating Sum of Boxes scale.
Participants receiving the drug also experienced substantial reductions in amyloid levels in the brain, as confirmed by positron emission tomography (PET) scans. By the end of the trial, many subjects were below the amyloid threshold typically indicative of Alzheimer’s, although the treatment did not reverse existing symptoms.
Safety Concerns and Cost Implications
Despite the potential benefits, safety concerns have been raised regarding lecanemab. The TGA previously rejected the drug’s approval in October 2022 due to its risk-benefit profile. Approximately 12.6% of trial participants experienced brain swelling, with the incidence rising to 32.6% among individuals with two copies of the Alzheimer-promoting gene, apolipoprotein E4 (ApoE4). While most cases of brain swelling presented mild symptoms such as headaches and dizziness, some patients on blood thinners experienced severe complications, including fatal brain bleeds.
To mitigate these risks, patients prescribed lecanemab will need to undergo three-monthly MRI scans to monitor their brain health. Additionally, 17.3% of those treated experienced small brain bleeds, compared to 9.0% in the placebo group.
Currently, lecanemab is not subsidized by Australia’s Pharmaceutical Benefits Scheme (PBS), costing around A$40,000 annually. This price places it out of reach for many potential patients. Treatment guidelines recommend dosing every two weeks for an initial 18-month period, followed by monthly maintenance doses. The PBS has yet to review lecanemab for its listing, and a similar drug, donanemab, was rejected in July due to concerns over uncertain benefits.
While lecanemab offers a new avenue for early-stage Alzheimer’s treatment, it is important to note that it is not a cure. The drug may slow disease progression but does not alleviate symptoms. It is crucial for patients experiencing early signs of Alzheimer’s, such as persistent short-term memory loss or confusion, to seek medical advice promptly for diagnosis and treatment options.
Dr. Steve Macfarlane, a consultant for Eisai, Janssen, and Eli Lilly, emphasized the importance of understanding the limitations of these treatments. As the landscape of Alzheimer’s research continues to evolve, the approval of lecanemab marks a significant step forward in combating this devastating disease.
