New Alzheimer’s drug: study gives hope – with limitations

The antibody drug donanemab, which binds to a special form of the protein beta-amyloid (Aβ), measurably slows the progression of Alzheimer’s dementia. This emerges from the preliminary results of a phase III study with the drug, which the pharmaceutical company Eli Lilly published in a press release.

According to this, the disease did not progress measurably in 47 percent of the participants, compared to 29 percent of the control group. The ability of those affected to carry out everyday tasks decreased by 40 percent more slowly, the press release continues. However, serious side effects have also occurred. The results have not yet been independently reviewed and published in a specialist journal.

New Alzheimer’s drug targets the causes

The drug targets pyroglutamate-Aβ, a protein fragment that is toxic to brain cells. It appears in the protein deposits, called plaques, typical of Alzheimer’s. These amyloid plaques are suspected to damage the brain and cause the mental decline characteristic of the disease. However, to date, most drugs targeting this mechanism have been ineffective.

In the studies, donanemab reduced the amount of amyloid plaques in the brain, with 71 percent of the test subjects measuring the values ​​for the protein accumulations returning to normal. The fact that the antibody also slows down mental decline supports this the hypothesis that has been questioned again and again because of the failures in treatmentthat the amyloid plaques play an essential role in Alzheimer’s.

The success of the monoclonal antibody confirms other positive results with antibodies against the plaques. So reduced the 2023 legal in the US Antibody preparation lecanemab , which binds to Aβ and thereby prevents plaque formation, reduces the progression of dementia by an average of 27 percent. However, according to the preliminary study results, donanemab is significantly more effective because it breaks down the plaques. However, the effect has so far been relatively small, and it is likely that such drugs are primarily useful for those affected in the early phases of the disease. The group of sufferers who benefited the most was those who only had moderate deposits of the tau protein in the brain – the protein indicates the severity of the disease and its progression.

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Some patients experience severe side effects

In addition, Eli Lilly reports serious side effects. Swelling of the brain occurred in a quarter of those treated, and bleeding in the brain in a third – a problem that generally occurs with antibody therapies against amyloid plaques. They were also found to be stronger with donanemab than with lecanemab. Of the total of 1736 subjects, two died from these complications, one more presumably in connection with it.

Despite side effects, this drug increases hope

This is why treatment with the antibody, even after approval has been granted, is a difficult decision that has to be made on a case-by-case basis. The greatest advance made by the antibodies is proving that Alzheimer’s can be treated causally, allowing future drugs to be tailored around this mechanism of action.