Tokyo - (AFP) - A number of scientists expressed their satisfaction Wednesday that the detailed results of a clinical study on a new drug confirmed its effectiveness in slowing the cognitive decline of patients with neurodegenerative Alzheimer's disease , but also pointed out that it may lead to negative effects.

The full results of this advanced (Phase 3) clinical study of nearly 1,800 subjects followed over 18 months confirmed a 27 percent reduction in cognitive decline in patients treated with lecanemab, from the Japanese pharmaceutical group Esai. (Eisai) and the American "Biogen".

It was previously announced at the end of last September about this percentage, which is considered "statistically significant" according to the two groups.

But the full study, published Wednesday in the New England Journal of Medicine, also reported rates of side effects for licanimab, which are sometimes severe and significantly more frequent than the placebo group.

It was found that 17.3% of the patients who received "lecanimab" suffered a cerebral hemorrhage, while the rate was limited to 9% among those who took the placebo.

And 12.6 percent of people who received this experimental drug experienced cerebral edema, compared to just 1.7 percent in the placebo group.

However, the overall death rate was almost the same for the two groups of patients in the study (0.7 percent in those treated with licanimab, and 0.8 percent in those given placebo).

"This is the first drug that offers a real treatment option for people with Alzheimer's disease," said Bart de Strober, director of the Institute of Dementia Research at the British Institute.

"Although the clinical benefits appear to be somewhat limited, they are expected to become more pronounced if the drug is taken for a longer period," added the professor.

Alzheimer's patients suffer from plaques of a protein called amyloid that form around nerve cells and eventually destroy them. Two major proteins, tau and beta-amyloid, build up abnormally in the brain, causing its cells to die and shrink.

One of the most prominent consequences of this is memory loss and the inability to perform daily tasks. This disease is considered one of the most important public health problems, affecting more than 40 million people worldwide.

Licanimab targets deposits of the protein beta-amyloid but only in the early stages of Alzheimer's disease, which may limit its use because the disease is often diagnosed late.

Another drug developed by Biogen called Aduhelm, which also targets amyloid plaques, raised a lot of hopes in 2021 by being the first drug approved in the United States against the disease since 2003.

But it also caused controversy, as the US Medicines Agency disagreed with the opinion of an expert panel that considered that the treatment had not been sufficiently proven effective during clinical trials. The agency later restricted its use to people with mild cases of the disease.