from the now-where-did-I-put-my-keys dept.
The amyloid hypothesis is the theory that the accumulation of beta-amyloids in the brain leads to Alzheimer's Disease. These amyloids are "sticky" protein fragments, and the idea is that something in the body that normally regulates them fails and they accumulate in the brain. The idea was proposed in the early 1990s when it was observed that many Alzheimer's patients exhibited larger than normal amounts of amyloid plaques. This hypothesis has driven a very active area of research for drugs and treatments that address beta-amyloids.
In what some see as a fundamental blow to the hypothesis itself, it was recently announced that one of the leading drugs, solanezumab from Eli Lilly, has failed in a large trial of people with mild dementia. The clinical trial involved more than 2,100 people diagnosed with mild dementia due to Alzheimer’s disease, but the results showed only a small benefit of the drug. Eli Lilly has also been conducting prevention trials where the drug is given to people known genetically to be high-risk for the disease, and they said they will discuss with their clinical trial partners whether they will continue those studies.
Lilly’s result may say more about the characteristics of solanezumab than the accuracy of the underlying amyloid hypothesis, says Christian Haass, head of the Munich branch of the German Centre for Neurodegenerative Diseases. The antibody targets soluble forms of amyloid, he points out, so it “could be trapped in the blood without ever reaching the actual target in the brain in sufficient quantities”.
The appeal of the amyloid hypothesis is that it is a simple one. However, in the 25 years since it was proposed, it has led to essentially no progress in preventing or curing the disease. Criticism of the theory has grown with each failed result.
“We’re flogging a dead horse,” adds Peter Davies, an Alzheimer’s researcher at the Feinstein Institute for Medical Research in Manhasset, New York. “There’s no sign of anybody getting better, even for a short period, and that suggests to me that you have the wrong mechanism.”
Dr. Lowe, from In the Pipeline, writes of how the efficacy requirements of the FDA save US taxpayers money:
Remember solanezumab? That was the amyloid-targeting antibody that Eli Lilly kept on investigating in trial after trial, looking for some effect on Alzheimer’s. Last November, the final, final word finally came down that it really, truly, does not work. To recap, mouse model results with a similar antibody were published in 2001. Phase I results of solanezumab itself were published in 2010, and Phase II results were published in 2012.
The authors of the NEJM [New England Journal of Medicine] paper would like to point out that under the current system, the cost of investigating all this was largely borne by the drug’s developers, not the patients and not the taxpayers
[...] Under a system designed to speed up drug approvals, people might have started taking it back in 2010-2012, when the Phase I and II results showed no adverse effects.
[...] We have a very tightly regulated and opaque market indeed in this country for prescription drugs and every other form of health care, and it’s not a very good place to discover prices or utilities. You could imagine a system where these things could be done better than we’re doing them, but such a system would be pretty far from what we have going now.
[...] The NEJM paper estimates, pretty conservatively, that had solanezumab been given conditional approval back in 2012 or so, that we – meaning Medicare, for the most part, which is to say all taxpayers, but also insurance companies and patients – would have spent at least ten billion dollars injecting Alzheimer’s patients with an expensive placebo. No one would have gotten the tiniest bit better. False hope all around, with no benefit, and billions of dollars down the tubes.
Note: Bold added by submitter.
Merck has ended a trial for the experimental Alzheimer's treatment verubecestat, a BACE1 inhibitor, after it was found to be ineffective. Biogen has increased the sample size of a trial for aducanumab, worrying some investors. The news comes after the failure of drugs such as solanezumab and intepirdine to treat Alzheimer's and dementia.
In proposed new guidelines released on Thursday, the FDA appears open to trial goals that better match early patient populations, including people who have yet to display memory loss or functional impairment, such as the ability to wash or dress themselves or cook meals.
The draft guidelines suggest that improvement in biomarkers, such as amount of beta amyloid in the brain, a protein linked to the disease, may be an acceptable goal for deeming a drug successful in patients with no symptoms. FDA guidelines used in prior studies demanded that a drug demonstrate both cognitive and functional improvements.
A bipartisan group of Senators and Congressman have introduced the Concentrating on High-Value Alzheimer's Needs to Get to an End (CHANGE) Act, which would also reduce regulatory barriers faced by clinical trials. The annual cost of Alzheimer's and dementia care in the U.S. is projected to rise to $1.1 trillion by 2050.
Meanwhile, a group of researchers has found that targeting BACE1 enzymes could remove existing amyloid plaques (in mice):
Knocking back an enzyme swept mouse brains clean of protein globs that are a sign of Alzheimer's disease. Reducing the enzyme is known to keep these nerve-damaging plaques from forming. But the disappearance of existing plaques was unexpected [open, DOI: 10.1084/jem.20171831] [DX], researchers report online February 14 in the Journal of Experimental Medicine.
The brains of mice engineered to develop Alzheimer's disease were riddled with these plaques, clumps of amyloid-beta protein fragments, by the time the animals were 10 months old. But the brains of 10-month-old Alzheimer's mice that had a severely reduced amount of an enzyme called BACE1 were essentially clear of new and old plaques.