Two new drugs, the first of which appears to be able to slow the progression of Alzheimer’s disease, have become embroiled in one of the biggest medical controversies in recent years.

To their supporters, the drugs lecanemab and donanemab represent the first real chance to fight the disease after decades of research — while to critics, they are yet another disappointment after a long string of costly failures.

British biologist John Hardy, who has been studying Alzheimer’s since the 1990s, told AFP that thanks to these treatments “we have turned a corner.”

Rob Howard, professor of geriatric psychiatry at University College London, was on the other side.

“I think these medications have been used to raise false and unrealistic hopes in people with Alzheimer’s disease and their families,” he said.

These opposing statements express strong views on recently introduced drugs for Alzheimer’s, the most common form of dementia, which afflicts millions of people worldwide.

Lecanemab, sold as Lecambi, was developed by US pharma companies Biogen and Eisai. Donanemab, developed by pharma giant Eli Lilly, is sold as Kisunla.

This controversy has led to different countries taking varying stances on whether or not to approve the drugs.

The United States gave the green light to lecanemab in 2023 and donanemab earlier this year.

However, in July the European Union rejected lecanemab, a bad sign for donanemab’s chances of approval.

Britain took a middle path last month, approving the use of lecanemab but not making it available in the state’s National Health Service.

No one can deny that these two drugs are the most effective treatments for Alzheimer’s to date – but their effectiveness is limited.

Both drugs reduce cognitive decline in patients early in the disease by about 30 percent.

Although this figure may seem high, it represents a relatively small difference compared to the one-and-a-half-year period in which these studies were conducted.

“The benefits are so small they are practically invisible to any individual patient,” Howard said.

According to critics, the benefits of these drugs outweigh their risks, as they can sometimes cause swelling or bleeding in the brain, which has been fatal in rare cases.

And they are very expensive. At the prices being charged by Biogen and Eisai in the United States, lecanemab would cost 133 billion euros ($148 billion) if given to all eligible patients in the European Union, according to a 2023 study.

Proponents of these drugs, including many neurologists, believe they can provide patients with a few more precious months of autonomy.

He also believes that the effectiveness of these drugs can increase manifold if patients start taking them early in the disease progression. This may soon become more practical as there have been significant advances in research on Alzheimer’s diagnosis recently.

Differing national policies can also mean that poorer patients are left behind.

“We will see wealthy people going to the US for drugs,” Hardy said.

The debate traces its roots to a landmark article written by Hardy in 1992, in which he explained how the disease actually works.

The article argues that clumps of proteins called amyloid plaques – which are consistently found in the brains of Alzheimer’s patients – are not just one element among others, but the main factor driving the disease.

Over the decades, several drugs targeting these amyloid plaques have been developed, but all have failed — until lecanemab and donanemab.

There may be skepticism in some quarters about new drugs because previous drugs were defended and even praised by some, despite their ineffectiveness.

Christian Guy-Coichard, head of Formindep, a French organization that monitors medical conflicts of interest, accused Alzheimer’s groups, researchers and drug companies of being too close.

But Benoit Durand, deputy director of France Alzheimer’s, said very little of its funding comes from Biogen/Eisai or Eli Lilly, pointing instead to pressure for new treatments from patients’ families.

Durand told AFP that “they don’t understand” the EU’s decision to reject a new drug. He also feared that laboratories could lose interest in Alzheimer’s disease because of these setbacks.

Even some in the pharmaceutical industry admit that past failures have not helped build trust.

A doctor working for Eli Lilly, who asked not to be named, said its rival Biogen had exaggerated the benefits of a previous treatment, Aduhelm. The drug was controversially approved in the US in 2021 but was later withdrawn.

“The Eduhelm study was a mess,” the doctor said.

The doctor pointed the finger at Biogen, saying the ensuing situation “caused great damage and led to chaos in the discipline.”

In response, Biogen told AFP it was complying with “the principles of scientific research as well as legal and regulatory requirements”.

But an Eli Lilly doctor defended the new treatment and urged people to look to the future, not the past.

Like other experts, he believed that mechanisms other than amyloid needed to be explored that may be behind Alzheimer’s.

Given the complexity of the disease, it’s unlikely that “single-target therapies will achieve effects significantly larger than those of lecanemab and donanemab,” a group of experts wrote last month in the Journal of Prevention of Alzheimer’s Disease.

But he said the new drugs represent an “important step” in the treatment of Alzheimer’s.