Besides, the approval of the earlier medicine called Aducanumab in 2021, developed by Japanese and American companies Eisai and Biogen, had come under the scanner for not being as effective as claimed. The drug Lecanemab, marketed as Leqembi, is the second such monoclonal antibody to receive an approval from the regulator. Its accelerated approval, a protocol used for serious conditions for which not many treatments exist, was based on a “surrogate endpoint” – there was a statistically significant reduction in amyloid beta plaques at week 79 in 856 Alzheimer’s patients who took the medicine, according to the statement from USFDA.

What has the doctors excited is that compared to earlier drugs, the results show there was a 27 per cent reduction in the rate of cognitive decline in patients who received Lecanemab after 18 months as compared to those who did not. Says Dr MV Padma Shrivastava, head of the neurosciences centre at the All India Institute of Medical Science (AIIMS), “There are various scales for measuring cognitive decline but it means nothing to the patient and caregiver unless they can see an improvement – a good example would be a patient, who is soiling, starting to tell the caregivers that they need to go to the bathroom. And in this context, the medicine approved now has an edge over the previous one.”

“In both the drugs, we saw the plaque clearing out, based on radiological findings, but there was no significant clinical improvement seen in the case of Aducanumab. But in the case of Lecanemab, a functional benefit has been observed that offsets the risk of brain bleed and swelling that was seen in both the medicines after the plaques reduced. This is the reason there is an excitement surrounding the drug because it comes after a long hiatus in Alzheimer’s drugs getting approved,” she adds.

Even in the US, Maria Carrillo, the Alzheimer’s Association’s chief science officer, was quoted as telling CNN: “We believe, based on the totality of positive data from clinical trials of this treatment, that the FDA should approve. Peer-reviewed, published results show Lecanemab will provide patients in the earliest stages of Alzheimer’s more time to participate in daily life and live independently. It could mean many months more of recognising their spouse, children and grandchildren.”

However, cost is a big barrier to access. The infusion will cost over $26,500 per year, making it unaffordable for most. “Whether the benefits from the medicine justify the costs is yet to be known. Plus, once there is increased production, the cost does go down. Still, it is a long way away for this drug,” says Dr Shrivastava.

The earlier drugs did not guarantee better cognition in patients. An article by the British Medical Journal, said, “While amyloid plaques are generally assumed to cause cognitive decline, there is uncertainty as to whether reducing amyloid plaques in the brain protects patients from cognitive decline. Previous trials of drugs which reduce amyloid plaques in the brain have shown no clinical benefit.”

In addition, the approval of the predecessor drug was also examined by US congressional committees that found it to be “rife with irregularities” – there was an unusually close collaboration of FDA officials with the manufacturing company. Besides, an approval was given despite the clinical trial being cancelled by the company and an expert panel’s recommendation against it.

Although the phase III trial data is not required for such accelerated approval, Lecanemab’s results of the trial with 1,795 participants are available in the public domain.

The new drug also comes with its caveats. Lecanemab will be available with a warning for amyloid-related imaging abnormalities (ARIA), swelling and blood spots in the brain when the plaques reduce, which are usually asymptomatic but can lead to serious and life-threatening events, according to FDA. It will also come with warnings for infusion-related reactions, with symptoms such as flu-like symptoms, nausea, vomiting and changes in blood pressure.

The prescribing information further states that it is meant for those in the early stages of the disease such as mild cognitive impairment or mild dementia just like the population on which the study was conducted. “The labelling states that there is no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied,” the FDA statement reads.