Nearly 900,000 people suffer from Alzheimer’s disease in France. This number is only increasing from year to year. Because the main risk factor for this pathology is age and as life expectancy increases, the number of Alzheimer’s cases increases.
Although this disease was first described more than a hundred years ago, there is currently no treatment to reverse the degeneration of the brain of those affected. And even less to make it disappear.
A delay in the onset of symptoms
If it is so difficult to find a drug against this disease, it is primarily because the first symptoms appear twenty, even thirty years after the onset of the condition. During this time, the neurons have significantly degraded. “In these patients, the brain is already too damaged. Even if we stop the process of the disease, they cannot live with satisfactory intellectual and cognitive functions”, explains Philippe Amouyel, general manager of the Alzheimer Foundation and hospital practitioner at the Lille University Hospital.
However, several drugs have shown their effectiveness against lesions in neurons. “The last three currently in development clean up to 80% of patient lesions, at the end of the trial”, assures Bruno Dubois, professor of neurology and member of the Academy of Medicine. Unfortunately, even if these treatments made it possible to reduce these lesions, the researchers realized that the memory of the patients did not return. “However, we are not there to treat lesions, but symptoms, recalls the professor. So we were very disappointed. »
Trials on patients at too advanced a stage
If these trials showed no effect on symptoms, it may be because, until the mid-2010s, the drugs were tested on patients whose disease was already well advanced. As with other illnesses, the researchers waited until there were symptoms to perform the tests. “When you have advanced Alzheimer’s disease, you have such brain damage. It was illusory to hope that we could go back or even block things, “ says Bruno Dubois to himself today.
Once this observation was made, the researchers decided to include in their trials patients at a less advanced stage of their disease. “For five to six years, we have been doing clinical trials on people either at very early stages of Alzheimer’s disease, or at stages of mild impairment of cognitive functions who we know will become Alzheimer’s” , explains Philippe Amouyel. With this new approach, the trials are starting to bear fruit.
But he prefers to warn, “even if we manage to find a treatment that works, it will only benefit patients with extremely early Alzheimer’s or those for whom the disease is already there but whose symptoms have not yet appeared. »
Low financial means
About 55.2 million people have Alzheimer’s disease or a related disease worldwide, according to the World Health Organization. A very broad target – and a real financial windfall – for pharmaceutical companies. Very large laboratories have therefore embarked on the search for a treatment against this degenerative disease. Especially since in 2000, promising work showed on a mouse model a disappearance of Alzheimer’s lesions after the injection of monoclonal antibodies. “At the time, it was spectacular, recalls the professor of neurology. The laboratories have all embarked on this path, telling themselves that they have found the solution. »
But from the late 1990s until 2015, every drug tested by big companies turned out to be failures. Zero response. No use. No marketing. “It gave the idea that it was difficult to develop a drug against Alzheimer’s”, regrets Philippe Amouyel. A big financial loss for the pharmaceutical companies which had invested billions of euros and dollars in this research. “They then invested less in this sector and preferred to turn to cancer or infectious diseases, for which the research was more promising”, analyzes Philippe Amouyel.
New tests and drugs
But according to the director general of the Alzheimer Foundation, in recent years, small laboratories, start-ups or biotechnology companies have taken over. They develop molecules which are then tested in phases 1 and 2 on earlier patients. “If the results are interesting, the major laboratories are interested in them and set up major clinical trials. »
A new experimental drug, Lecanemab, has just received marketing authorization in the United States. While it shows promising results in fighting Alzheimer’s disease, it can cause heavy side effects. “We can’t say that we don’t have a result. They are relatively modest, but they are coming,” concludes Bruno Dubois.
