How Leqembi became the biggest news in Alzheimer’s disease in 40 years, and what comes next
Betsy Groves, 73, with her granddaughter. Groves learned in 2021 that she has Alzheimer's disease. She hopes to take Leqembi, a drug approved by the FDA last week.
A few months ago, Betsy Groves traveled less than a mile from her home in Cambridge, Mass. to give a talk to a bunch of scientists. The scientists, who worked for the pharmaceutical companies Biogen and Eisai, wanted to know how she lived her life, how she thought about her future, and what it was like when a doctor’s appointment in 2021 gave her the worst possible news. Groves, 73, has Alzheimer’s disease. She caught it early, through a lumbar puncture that showed evidence of amyloid, an Alzheimer’s hallmark, in her cerebrospinal fluid. As a way of dealing with her diagnosis, she joined the Alzheimer’s Association’s National Early-Stage Advisory Board, which helped her shift into seeing her diagnosis as something she could use to help others.
After her talk, Groves stayed for lunch with the scientists, who were eager to put a face to their work. Biogen and Eisai were about to release the first drug to successfully combat Alzheimer’s in 40 years of experimental disaster. Their drug, which is known by the scientific name lecanemab and the marketing name Leqembi, was granted accelerated approval by the U.S. Food and Drug Administration last Friday, Jan. 6, after a study in 1,800 people showed that it reduced cognitive decline by 27 percent over 18 months.
It is no exaggeration to say that this result is a huge deal. The field of Alzheimer’s drug development has been absolutely littered with failures. Almost everything researchers have tried has tanked in clinical trials. “Most of the things that we've done have proven not to be effective, and it's not because we haven’t been taking a ton of shots at goal,” says Anton Porsteinsson, director of the University of Rochester Alzheimer's Disease Care, Research, and Education Program, who worked on the lecanemab trial. “I think it's fair to say you don't survive in this field unless you're an eternal optimist.”
As far back as 1984, a cure looked like it was within reach: Scientists discovered that the sticky plaques that develop in the brains of those who have Alzheimer’s are made up of a protein fragment called beta-amyloid. Buildup of beta-amyloid seemed to be sufficient to disrupt communication between, and eventually kill, memory cells. If that was true, then the cure should be straightforward: Stop the buildup of beta-amyloid; stop the Alzheimer’s disease.
It wasn’t so simple. Over the next 38 years, hundreds of drugs designed either to interfere with the production of abnormal amyloid or to clear it from the brain flamed out in trials. It got so bad that neuroscience drug divisions at major pharmaceutical companies (AstraZeneca, Pfizer, Bristol-Myers, GSK, Amgen) closed one by one, leaving the field to smaller, scrappier companies, like Cambridge-based Biogen and Tokyo-based Eisai. Some scientists began to dismiss the amyloid hypothesis altogether: If this protein fragment was so important to the disease, why didn’t ridding the brain of it do anything for patients? There was another abnormal protein that showed up in the brains of Alzheimer’s patients, called tau. Some researchers defected to the tau camp, or came to believe the proteins caused damage in combination.
The situation came to a head in 2021, when the FDA granted provisional approval to a drug called aducanumab, marketed as Aduhelm, against the advice of its own advisory council. The approval was based on proof that Aduhelm reduced beta-amyloid in the brain, even though one research trial showed it had no effect on people’s symptoms or daily life. Aduhelm could also cause serious side effects, like brain swelling and amyloid related imaging abnormalities (known as ARIA, these are basically micro-bleeds that appear on MRI scans). Without a clear benefit to memory loss that would make these risks worth it, Medicare refused to pay for Aduhelm among the general population. Two congressional committees launched an investigation into the drug’s approval, citing corporate greed, lapses in protocol, and an unjustifiably high price. (Aduhelm was also produced by the pharmaceutical company Biogen.)
To be clear, Leqembi is not the cure Alzheimer’s researchers hope for. While the drug is the first to show clear signs of a clinical benefit, the scientific establishment is split on how much of a difference Leqembi will make in the real world.
So far, Leqembi is like Aduhelm in that it has been given accelerated approval only for its ability to remove amyloid from the brain. Both are monoclonal antibodies that direct the immune system to attack and clear dysfunctional beta-amyloid. The difference is that, while that’s all Aduhelm was ever shown to do, Leqembi’s makers have already asked the FDA to give it full approval – a decision that would increase the likelihood that Medicare will cover it – based on data that show it also improves Alzheimer’s sufferer’s lives. Leqembi targets a different type of amyloid, a soluble version called “protofibrils,” and that appears to change the effect. “It can give individuals and their families three, six months longer to be participating in daily life and living independently,” says Claire Sexton, PhD, senior director of scientific programs & outreach for the Alzheimer's Association. “These types of changes matter for individuals and for their families.”
To be clear, Leqembi is not the cure Alzheimer’s researchers hope for. It does not halt or reverse the disease, and people do not get better. While the drug is the first to show clear signs of a clinical benefit, the scientific establishment is split on how much of a difference Leqembi will make in the real world. It has “a rather small effect,” wrote NIH Alzheimer’s researcher Madhav Thambisetty, MD, PhD, in an email to Leaps.org. “It is unclear how meaningful this difference will be to patients, and it is unlikely that this level of difference will be obvious to a patient (or their caregivers).” Another issue is cost: Leqembi will become available to patients later this month, but Eisai is setting the price at $26,500 per year, meaning that very few patients will be able to afford it unless Medicare chooses to reimburse them for it.
The same side effects that plagued Aduhelm are common in Leqembi treatment as well. In many patients, amyloid doesn’t just accumulate around neurons, it also forms deposits in the walls of blood vessels. Blood vessels that are shot through with amyloid are more brittle. If you infuse a drug that targets amyloid, brittle blood vessels in the brain can develop leakage that results in swelling or bleeds. Most of these come with no symptoms, and are only seen during testing, which is why they are called “imaging abnormalities.” But in situations where patients have multiple diseases or are prescribed incompatible drugs, they can be serious enough to cause death. The three deaths reported from Leqembi treatment (so far) are enough to make Thambisetty wonder “how well the drug may be tolerated in real world clinical practice where patients are likely to be sicker and have multiple other medical conditions in contrast to carefully selected patients in clinical trials.”
Porsteinsson believes that earlier detection of Alzheimer’s disease will be the next great advance in treatment, a more important step forward than Leqembi’s approval.
Still, there are reasons to be excited. A successful Alzheimer’s drug can pave the way for combination studies, in which patients try a known effective drug alongside newer, more experimental ones; or preventative studies, which take place years before symptoms occur. It also represents enormous strides in researchers’ understanding of the disease. For example, drug dosages have increased massively—in some cases quadrupling—from the early days of Alzheimer’s research. And patient selection for studies has changed drastically as well. Doctors now know that you’ve got to catch the disease early, through PET-scans or CSF tests for amyloid, if you want any chance of changing its course.
Porsteinsson believes that earlier detection of Alzheimer’s disease will be the next great advance in treatment, a more important step forward than Leqembi’s approval. His lab already uses blood tests for different types of amyloid, for different types of tau, and for measures of neuroinflammation, neural damage, and synaptic health, but commercially available versions from companies like C2N, Quest, and Fuji Rebio are likely to hit the market in the next couple of years. “[They are] going to transform the diagnosis of Alzheimer's disease,” Porsteinsson says. “If someone is experiencing memory problems, their physicians will be able to order a blood test that will tell us if this is the result of changes in your brain due to Alzheimer's disease. It will ultimately make it much easier to identify people at a very early stage of the disease, where they are most likely to benefit from treatment.”
Learn more about new blood tests to detect Alzheimer's
Early detection can help patients for more philosophical reasons as well. Betsy Groves credits finding her Alzheimer’s early with giving her the space to understand and process the changes that were happening to her before they got so bad that she couldn’t. She has been able to update her legal documents and, through her role on the Advisory Group, help the Alzheimer’s Association with developing its programs and support services for people in the early stages of the disease. She still drives, and because she and her husband love to travel, they are hoping to get out of grey, rainy Cambridge and off to Texas or Arizona this spring.
Because her Alzheimer’s disease involves amyloid deposits (a “substantial portion” do not, says Claire Sexton, which is an additional complication for research), and has not yet reached an advanced stage, Groves may be a good candidate to try Leqembi. She says she’d welcome the opportunity to take it. If she can get access, Groves hopes the drug will give her more days to be fully functioning with her husband, daughters, and three grandchildren. Mostly, she avoids thinking about what the latter stages of Alzheimer’s might be like, but she knows the time will come when it will be her reality. “So whatever lecanemab can do to extend my more productive ways of engaging with relationships in the world,” she says. “I'll take that in a minute.”
Inside Scoop: How a DARPA Scientist Helped Usher in a Game-Changing Covid Treatment
Amy Jenkins is a program manager for the Defense Advanced Research Projects Agency's Biological Technologies Office, which runs a project called the Pandemic Prevention Platform.
Amy Jenkins was in her office at DARPA, a research and development agency within the Department of Defense, when she first heard about a respiratory illness plaguing the Chinese city of Wuhan. Because she's a program manager for DARPA's Biological Technologies Office, her colleagues started stopping by. "It's really unusual, isn't it?" they would say.
At the time, China had a few dozen cases of what we now call COVID-19. "We should maybe keep an eye on that," she thought.
Early in 2020, still just keeping watch, she was visiting researchers working on DARPA's Pandemic Prevention Platform (P3), a project to develop treatments for "any known or previously unknown infectious threat," within 60 days of its appearance. "We looked at each other and said, 'Should we be doing something?'" she says.
For projects like P3, groups of scientists—often at universities and private companies—compete for DARPA contracts, and program managers like Jenkins oversee the work. Those that won the P3 bid included scientists at AbCellera Biologics, Inc., AstraZeneca, Duke University, and Vanderbilt University.
At the time Jenkins was talking to the P3 performers, though, they didn't have evidence of community transmission. "We would have to cross that bar before we considered doing anything," she says.
The world soon leapt far over that bar. By the time Jenkins and her team decided P3 should be doing something—with their real work beginning in late February--it was too late to prevent this pandemic. But she could help P3 dig into the chemical foundations of COVID-19's malfeasance, and cut off its roots. That work represents, in fact, her roots.
In late February 2020, DARPA received a single blood sample from a recovered COVID-19 patient, in which P3 researchers could go fishing for antibodies. The day it arrived, Jenkins's stomach roiled. "We get one shot," she thought.
Fighting the Smallest Enemies
Jenkins, who's in her early 40s, first got into germs the way many 90s kids did: by reading The Hot Zone, a novel about a hemorrhagic fever gone rogue. It wasn't exactly the disintegrating organs that hooked her. It was the idea that "these very pathogens that we can't even see can make us so sick and bring us to our knees," she says. Reading about scientists facing down deadly disease, she wondered, "How do these things make you so sick?"
She chased that question in college, majoring in both biomolecular science and chemistry, and later became an antibody expert. Antibodies are proteins that hook to a pathogen to block it from attaching to your cells, or tag it for destruction by the rest of the immune system. Soon, she jumped on the "monoclonal antibodies" train—developing synthetic versions of these natural defenses, which doctors can give to people to help them battle an early-stage infection, and even to prevent an infection from taking root after an exposure.
Jenkins likens the antibody treatments to the old aphorism about fishing: Vaccines teach your body how to fish, but antibodies simply give your body the pesca-fare. While that, as the saying goes, won't feed you for a lifetime, it will last a few weeks or months. Monoclonal antibodies thus are a promising preventative option in the immediate short-term when a vaccine hasn't yet been given (or hasn't had time to produce an immune response), as well as an important treatment weapon in the current fight. After former president Donald Trump contracted COVID-19, he received a monoclonal antibody treatment from biotech company Regeneron.
As for Jenkins, she started working as a DARPA Biological Technologies Office contractor soon after completing her postdoc. But it was a suit job, not a labcoat job. And suit jobs, at first, left Jenkins conflicted, worried about being bored. She'd give it a year, she thought. But the year expired, and bored she was not. Around five years later, in June 2019, the agency hired her to manage several of the office's programs. A year into that gig, the world was months into a pandemic.
The Pandemic Pivot
At DARPA, Jenkins inherited five programs, including P3. P3 works by taking blood from recovered people, fishing out their antibodies, identifying the most effective ones, and then figuring out how to manufacture them fast. Back then, P3 existed to help with nebulous, future outbreaks: Pandemic X. Not this pandemic. "I did not have a crystal ball," she says, "but I will say that all of us in the infectious diseases and public-health realm knew that the next pandemic was coming."
Three days after a January 2020 meeting with P3 researchers, COVID-19 appeared in Seattle, then began whipping through communities. The time had come for P3 teams to swivel. "We had done this," she says. "We had practiced this before." But would their methods stand up to something unknown, racing through the global population? "The big anxiety was, 'Wow, this was real,'" says Jenkins.
While facing down that realness, Jenkins was also managing other projects. In one called PREPARE, groups develop "medical countermeasures" that modulate a person's genetic code to boost their bodies' responses to threats. Another project, NOW, envisions shipping-container-sized factories that can make thousands of vaccine doses in days. And then there's Prometheus—which means "forethought" in Greek, and is the name of the god who stole fire and gave it to humans. Wrapping up as COVID ramped up, Prometheus aimed to identify people who are contagious—with whatever—before they start coughing, and even if they never do.
All of DARPA's projects focus on developing early-stage technology, passing it off to other agencies or industry to put it into operation. The orientation toward a specific goal appealed to Jenkins, as a contrast to academia. "You go down a rabbit hole for years at a time sometimes, chasing some concept you found interesting in the lab," she says. That's good for the human pursuit of knowledge, and leads to later applications, but DARPA wants a practical prototype—stat.
"Dual-Use" Technologies
That desire, though, and the fact that DARPA is a defense agency, present philosophical complications. "Bioethics in the national-security context turns all the dials up to 10+," says Jonathan Moreno, a medical ethicist at the University of Pennsylvania.
While developing antibody treatments to stem a pandemic seems straightforwardly good, all biological research—especially that backed by military money—requires evaluating potential knock-on applications, even those that might come from outside the entity that did the developing. As Moreno put it, "Albert Einstein wasn't thinking about blowing up Hiroshima." Particularly sensitive are so-called "dual-use" technologies—those tools that could be used for both benign and nefarious purposes, or are of interest to both the civilian and military worlds.
Moreno takes Prometheus itself as an example of "dual-use" technology. "Think about somebody wearing a suicide vest. Instead of a suicide vest, make them extremely contagious with something. The flu plus Ebola," he says. "Send them someplace, a sensitive environment. We would like to be able to defend against that"—not just tell whether Uncle Fred is bringing asymptomatic COVID home for Christmas. Prometheus, Jenkins says, had safety in mind from the get-go, and required contenders to "develop a risk mitigation plan" and "detail their strategy for appropriate control of information."
To look at a different program, if you can modulate genes to help healing, you probably know something (or know someone else could infer something) about how to hinder healing. Those sorts of risks are why PREPARE researchers got their own "ethical, legal, and social implications" panel, which meets quarterly "to ensure that we are performing all research and publications in a safe and ethical manner," says Jenkins.
DARPA as a whole, Moreno says, is institutionally sensitive to bioethics. The agency has ethics panels, and funded a 2014 National Academies assessment of how to address the "ethical, legal, and societal issues" around technology that has military relevance. "In the cases of biotechnologies where some of that research brushes up against what could legitimately be considered dual-use, that in itself justifies our investment," says Jenkins. "DARPA deliberately focuses on safety and countermeasures against potentially dangerous technologies, and we structure our programs to be transparent, safe, and legal."
Going Fishing
In late February 2020, DARPA received a single blood sample from a recovered COVID-19 patient, in which P3 researchers could go fishing for antibodies. The day it arrived, Jenkins's stomach roiled. "We get one shot," she thought.
As scientists from the P3-funded AbCellera went through the processes they'd practiced, Jenkins managed their work, tracking progress and relaying results. Soon, the team had isolated a suitable protein: bamlanivimab. It attaches to and blocks off the infamous spike proteins on SARS-CoV-2—those sticky suction-cups in illustrations. Partnering with Eli Lilly in a manufacturing agreement, the biotech company brought it to clinical trials in May, just a few months after its work on the deadly pathogen began, after much of the planet became a hot zone.
On November 10—Jenkins's favorite day at the (home) office—the FDA provided Eli Lilly emergency use authorization for bamlanivimab. But she's only mutedly screaming (with joy) inside her heart. "This pandemic isn't 'one morning we're going to wake up and it's all over,'" she says. When it is over, she and her colleagues plan to celebrate their promethean work. "I'm hoping to be able to do it in person," she says. "Until then, I have not taken a breath."
Everyone Should Hear My COVID Vaccine Experience
Dr. Ranney immediately after receiving her first dose of the Pfizer vaccine on December 18, 2020.
On December 18th, 2020, I received my first dose of the Pfizer mRNA vaccine against SARS-CoV-2. On January 9th, 2021, I received my second. I am now a CDC-card-carrying, fully vaccinated person.
The build-up to the first dose was momentous. I was scheduled for the first dose of the morning. Our vaccine clinic was abuzz with excitement and hope, and some media folks were there to capture the moment. A couple of fellow emergency physicians were in the same cohort of recipients as I; we exchanged virtual high-fives and took a picture of socially distanced hugs. It was, after all, the closest thing we'd had to a celebration in months.
I walked in the vaccine administration room with anticipation – it was tough to believe this moment was truly, finally here. I got a little video of my getting the shot, took my obligate vaccine selfie, waited in the observation area for 15 minutes to ensure I didn't have a reaction, and then proudly joined 1000s of fellow healthcare workers across the country in posting #ThisIsMyShot on social media. "Here we go, America!"
The first shot, though, didn't actually do all that much for me. It hurt less than a flu shot (which, by the way, doesn't hurt much). I had virtually no side effects. I also knew that it did not yet protect me. The Pfizer (and Moderna) data show very clearly that although the immune response starts to grow 10-12 days after the first shot, one doesn't reach full protection against COVID-19 until much later.
So when, two days after my first shot, I headed back to work in the emergency department, I kept wondering "Will this be the day that I get sick? Wouldn't that be ironic!" Although I never go without an N95 during patient care, it just takes one slip – scratching one's eyes, eating lunch in a break room that an infected colleague had just been in – to get ill. Ten months into this pandemic, it is so easy to get fatigued, to make a small error just one time.
Indeed, I had a few colleagues fall ill in between their first and second shots; one was hospitalized. This was not surprising, but still sad, given how close they had come to escaping infection.
Scientifically speaking, one doesn't need to feel bad to develop an immune response. Emotionally, though, I welcomed the symptoms as proof positive that I would be protected.
This time period felt a little like we had our learner's permit for driving: we were on our way to being safe, but not quite there yet.
I also watched, with dismay, our failures as a nation at timely distribution of the vaccine. On December 18th, despite the logistical snafus that many of us had started to highlight, it was still somewhat believable that we would at least distribute (if not actually administer) 20 million doses by the New Year. But by December 31, my worst fears about the feds' lack of planning had been realized. Only 14 million doses had gone to states, and fewer than 3 million had been administered. Within the public health and medical community, we began to debate how to handle the shortages and slow vaccination rates: should we change prioritization schemes? Get rid of the second dose, in contradiction to what our FDA had approved?
Let me be clear: I really, really, really wanted my second dose. It is what is supported by the data. After living this long at risk, it felt frankly unfair that I might not get fully protected. I waited with trepidation, afraid that policies would shift before I got it in my arm.
At last, my date for my second shot arrived.
This shot was a little less momentous on the outside. The vaccine clinic was much more crowded, as we were now administering first doses to more people, as well as providing the second dose to many. There were no high fives, no media, and I took no selfies. I finished my observation period without trouble (as did everyone else vaccinated the same day, as is typical for these vaccines). I walked out the door planning to spend a nice afternoon outdoors with my kids.
Within 15 minutes, though, the very common side effects – reported by 80% of people my age after the second dose – began to appear. First I got a headache (like 52% of people my age), then body aches (37%), fatigue (59%), and chills (35%). I felt "foggy", like I was fighting something. Like 45% of trial participants who had received the actual vaccine, I took acetaminophen and ibuprofen to stave off the symptoms. There is some minimal evidence from other vaccines that pre-treatment with these anti-inflammatories may reduce antibodies, but given that half of trial participants took these medications, there's no reason to make yourself suffer if you develop side effects. Forty-eight hours later, just in time for my next shift, the side effects magically cleared. Scientifically speaking, one doesn't need to feel bad to develop an immune response. Emotionally, though, I welcomed the symptoms as proof positive that I would be protected.
My reaction was truly typical. Although the media hype focuses on major negative reactions, they are – statistically speaking – tremendously rare: fewer than 11/million people who received the Pfizer vaccine, and 3/million who received the Moderna vaccine, developed anaphylaxis; of these, all were treated, and all are fine. Compare this with the fact that approximately 1200/million Americans have died of this virus. I'll choose the minor, temporary, utterly treatable side effects any day.
Now, more than 14 days after my second dose, the data says that my chance of getting really sick is, truly, infinitesimally low. I don't have to worry that each shift will put me into the hospital. I feel emotionally lighter, and a little bit like I have a secret super-power.
But I also know that we are not yet home free.
I may have my personal equivalent of Harry Potter's invisibility cloak – but we don't yet know whether it protects those around me, at all. As Dr. Fauci himself has written, while community spread is high, there is still a chance that I could be a carrier of infection to others. So I still wear my N95 at work, I still mask in public, and I still shower as soon as I get home from a shift and put my scrubs right in the washing machine to protect my husband and children. I also won't see my parents indoors until they, too, have been vaccinated.
At the end of the day, these vaccines are both amazing and life-changing, and not. My colleagues are getting sick less often, now that many of us are a week or more out from our second dose. I can do things (albeit still masked) that would simply not have been safe a month ago. These are small miracles, for which I am thankful. But like so many things in life, they would be better if shared with others. Only when my community is mostly vaccinated, will I breathe easy again.
My deepest hope is that we all have – and take - the chance to get our shots, soon. Because although the symbolism and effect of the vaccine is high, the experience itself was … not that big a deal.