Research Translation Podcast
Neuroscientists are not famous for being dumb. So when the following timeline unfolded, they should have understood exactly what it meant: First, autopsy studies in 1991 [https://onlinelibrary.wiley.com/doi/abs/10.1002/ana.410300410] and 1992 [https://www.neurology.org/doi/10.1212/wnl.42.3.631] found that amyloid plaques—supposedly the cause of Alzheimer’s, as the centerpiece of the Amyloid Hypothesis—did not scale with the disease. Then, in 2001 [https://www.jneurosci.org/content/21/2/372] and 2002 [https://www.jneurosci.org/content/22/5/1858], researchers published data showing that an Alzheimer’s mouse model developed dementia—before ever developing plaques. Finally, in 2004 [https://www.neurology.org/doi/10.1212/01.WNL.0000159740.16984.3C] a vaccine successfully removed plaques from the brains of Alzheimer’s patients—yet their dementia continued to spiral, unabated. RT is fully reader-supported. For the price of a cup of coffee once a month from you, I can continue RT—please become a paid subscriber. It is hard to imagine a more obvious demise for the Amyloid Hypothesis. Some researchers, however, particularly those with funding and livelihoods tied to it, concentrated on the possibility that amyloid precursors might still be involved. If true, such a finding could preserve a role for amyloid researchers and their laboratories. But most precursors, detailed above, were well known, well studied, and stubbornly non-toxic. They could not explain the Alzheimer’s hallmarks of damaged tissue, lost synapses, and tangled detritus. Except, perhaps, for one, which remained a mystery. ‘Soluble oligomers’, theoretically the building blocks of fibrils, are exceedingly difficult to isolate because they are transient, tiny, and live in a dissolved state. Few labs had ever found them, much less studied their effects. Which is why it was blockbuster news in 2006 when Sylvain Lesné, at the University of Minnesota lab, pulled off a miracle with the potential to energize (read: fund) amyloid theorists everywhere. Despite the world’s prior work yielding—at best—messy, shaky evidence of oligomers, Lesné reported a clean, concrete, and copious yield of a new oligomer named beta-amyloid-*56, or ‘star-56’. Based on gel photos in Lesné’s paper [https://www.nature.com/articles/nature04533] the oligomer was clearly detectable in a mouse’s brain just days before the onset of dementia. Based entirely on this 2006 paper (since no other lab has ever reproduced the star-56 finding), for 16 years the star shone bright, offering an exciting new offshoot: The Amyloid Precursor Hypothesis. Then, barely in its adolescence, the new star flickered—and died. Matthew Schrag, an MD/PhD neuroscientist at Vanderbilt University, was hired by investors who suspected that an anti-amyloid drug maker’s claims were exaggerated. Schrag dug deep into the Amyloid Hypothesis and its derivatives, and came to Lesné’s study. In 2022, on a geeky post-publication review site called PubPeer [https://pubpeer.com/publications/8FF7E6996524B73ACB4A9EF5C0AACF], Schrag posted the following images and coolly accused the report of being a fraud. Soon, other super-sleuths jumped in. By the end, multiple forensic investigators and leading researchers flagged over 70 images from Lesné papers as likely to have been tampered with. For those interested in a full anatomy of the fraud, you can find it in Science [https://www.science.org/content/article/potential-fabrication-research-images-threatens-key-theory-alzheimers-disease], where the story [https://www.science.org/content/article/potential-fabrication-research-images-threatens-key-theory-alzheimers-disease] broke. On PubPeer you can also read the often cringe-worthy, years-long dialogue [https://pubpeer.com/publications/8FF7E6996524B73ACB4A9EF5C0AACF] between the researchers, Schrag, and others. In 2024 the paper was retracted after the Minnesota group (sans Lesné) finally conceded it had to be. Then, in a real head-scratcher, the senior author Dr. Ashe published a new paper [https://www.cell.com/iscience/fulltext/S2589-0042(24)00460-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2589004224004607%3Fshowall%3Dtrue] purporting to show that the original claims were all correct. The whole saga, she seemed to suggest, was just a silly misunderstanding. Who cares if you can’t see our friend Snuffleupagus—we can! The response from the research community was a collective eye roll. Dr. Schrag, for one, wasn’t having it. When Ashe touted their new paper in the PubPeer string [https://pubpeer.com/publications/8FF7E6996524B73ACB4A9EF5C0AACF], Schrag eviscerated each and every claim, concluding that the new version “objectively falls short of reproducing the earlier result.” Awkward. In any case, with the Amyloid Hypothesis dead, the crucial question was whether the Amyloid Precursor Hypothesis was viable, and the best answer is this: It’s been two decades, and no other research group has been able to even confirm the existence of star-56, much less replicate its effects. The few other oligomers that have been isolated suffer the same problem. The cherry on this debunking pie is the story of the BACE and GSI drugs, which inhibit the ‘secretase’ enzymes and therefore reduce virtually every precursor: monomers, oligomers, fibrils, and plaques. In clinical trials comparing them to a placebo, neither [https://www.nejm.org/doi/full/10.1056/NEJMoa1210951] drug class improved dementia—they both worsened [https://www.nejm.org/doi/full/10.1056/NEJMoa1812840] it. So, um, no. The Amyloid Precursor Hypothesis is no more viable than its fallen father. Next week, we’ll examine the unblushing audacity of anti-amyloid drug makers, who continue to make it clear that for them, amyloid IS the disease. Get full access to Research Translation at researchtranslation.substack.com/subscribe [https://researchtranslation.substack.com/subscribe?utm_medium=podcast&utm_campaign=CTA_4]
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