No one’s sure if synthetic mirror life will kill us all

For four days in February 2019, some 30 synthetic biologists and ethicists hunkered down at a conference center in Northern Virginia to brainstorm high-risk, cutting-­edge, irresistibly exciting ideas that the National Science Foundation should fund. By the end of the meeting, they’d landed on a compelling contender: making “mirror” bacteria. Should they come to be, the lab-created microbes would be structured and organized like ordinary bacteria, with one important exception: Key biological molecules like proteins, sugars, and lipids would be the mirror images of those found in nature. DNA, RNA, and many other components of living cells are chiral, which means they have a built-in rotational structure. Their mirrors would twist in the opposite direction. 

Researchers thrilled at the prospect. “Everybody—everybody—thought this was cool,” says John Glass, a synthetic biologist at the J. Craig Venter Institute in La Jolla, California, who attended the 2019 workshop and is a pioneer in developing synthetic cells. It was “an incredibly difficult project that would tell us potentially new things about how to design and build cells, or about the origin of life on Earth.” The group saw enormous potential for medicine, too. Mirror microbes might be engineered as biological factories, producing mirror molecules that could form the basis for new kinds of drugs. In theory, such therapeutics could perform the same functions as their natural counterparts, but without triggering unwelcome immune responses. 

After the meeting, the biologists recommended NSF funding for a handful of research groups to develop tools and carry out preliminary experiments, the beginnings of a path through the looking glass. The excitement was global. The National Natural Science Foundation of China funded major projects in mirror biology, as did the German Federal Ministry of Research, Technology, and Space.

By five years later, in 2024, many researchers involved in that NSF meeting had reversed course. They’d become convinced that in the worst of all possible futures, mirror organisms could trigger a catastrophic event threatening every form of life on Earth; they’d proliferate without predators and evade the immune defenses of people, plants, and animals. 

“I wish that one sunny afternoon we were having coffee and we realized the world’s about to end, but that’s not what happened.”

Kate Adamala, synthetic biologist, University of Minnesota

Over the past two years, they’ve been ringing alarm bells. They published an article in Science in December 2024, accompanied by a 299-page technical report addressing feasibility and risks. They’ve written essays and convened panels and cofounded the Mirror Biology Dialogues Fund (MBDF), a broadly funded nonprofit charged with supporting work on understanding and addressing the risk. The issue has received a blaze of media attention and ignited dialogues among not only chemists and synthetic biologists but also bioethicists and policymakers.  

What’s received less attention, however, is how we got here and what uncertainties still remain about any potential threat. Creating a mirror-life organism would be tremendously complicated and expensive. And although the scientific community is taking the alarm seriously, some scientists doubt whether it’s even possible to create a mirror organism anytime soon. “The hypothetical creation of mirror-­image organisms lies far beyond the reach of present-day science,” says Ting Zhu, a molecular biologist at Westlake University, in China, whose lab focuses on synthesizing mirror-image peptides and other molecules. He and others have urged colleagues not to let speculation and anxiety guide decision-making and argued that it’s premature to call for a broad moratorium on early-stage research, which they say could have medical benefits. 

But the researchers who are raising flags describe a pathway, even multiple pathways, to bringing mirror life into existence—and they say we urgently need guardrails to figure out what kinds of mirror-biology research might still be safe. That means they’re facing a question that others have encountered before, multiple times over the last several decades and with mixed results—one that doesn’t have a neat home in the scientific method. What should scientists do when they see the shadow of the end of the world in their own research? 

Looking-glass life

The French chemist and microbiologist Louis Pasteur was the first to recognize that biological molecules had built-in handedness. In the late 19th century, he described all living species as “functions of cosmic asymmetry.” What would happen, he mused, if one could replace these chiral components with their mirror opposites? 

Scientists now recognize that chirality is central to life itself, though no one knows why. In humans, 19 of the 20 so-called “standard” amino acids that make up proteins are chiral, and all in the same way. (The outlier, glycine, is symmetrical.) The functions of proteins are intricately tied to their shapes, and they mostly interact with other molecules through chiral structures. Almost all receptors on the surface of a cell are chiral. During an infection, the immune system’s sentinels use chirality to detect and bind to antigens—substances that trigger an immune response—and to start the process of building antibodies. 

By the late 20th century, researchers had begun to explore the idea of reversing chirality. In 1992, one team reported having synthesized the first mirror-image protein. That, in turn, set off the first clarion call about the risk: In response to the discovery, chemists at Purdue University pointed out, briefly, that mirror-life organisms, if they escaped from a lab, would be immune to any attack by “normal” life. A 2010 story in Wired highlighting early findings in the area noted that if a such a microbe developed the ability to photosynthesize, it could obliterate life as we know it. 

The synthetic biology community didn’t seriously weigh those threats then, says David Relman, a specialist who bridges infectious disease and microbiology at Stanford University and a trailblazer in studying the gut and oral microbiomes. The idea of a mirror microbe seemed too far beyond the actual progress on proteins. “This was almost a solely theoretical argument 20 years ago,” he says. 

Now the research landscape has changed. 

Scientists are quickly making progress on mirror images of the machinery cells use to make proteins and to self-replicate. Those components include DNA, which encodes the recipes for proteins; DNA polymerases, which help copy genetic material; and RNA, which carries recipes to ribosomes, the cell’s protein factories. If researchers could make self-replicating mirror ribosomes, then they would have an efficient way to produce mirror proteins. That could be used as a biological manufacturing method for therapeutics. But embedded in a self-­replicating, metabolizing synthetic cell, all these pieces could give rise to a mirror microbe. 

When synthetic biologists convened in Northern Virginia in 2019, they didn’t recognize how quickly the technology was advancing, and if they saw a threat at all, it may have been obscured by the blinding appeal of pushing the science forward. What’s become apparent now, says Glass, is that scientists in different disciplines, all related to mirror life, were largely unaware of what other scientists had been doing. Chemists didn’t know that synthetic biologists had made so much progress on creating mirror cells with natural chirality from scratch. Biologists didn’t appreciate that chemists were building ever-larger mirror macromolecules. “We tend to be siloed,” Glass says. And nobody, he says, had thought to seriously examine the immune system concerns that had already been raised in response to earlier work. “There was not an immunologist or an infectious disease person in the room,” Glass says, reflecting on the 2019 meeting. “I may have come closest, given that I work with pathogenic bacteria and viruses,” he adds, but his work doesn’t address how they cause infections in their hosts.

on the left, a hand with petri dish and the same image inverted on the right

GETTY IMAGES

These scientists also didn’t know that around the same time as their meeting, another conversation about mirror life was happening—a darker dialogue that was as focused on danger as it was on discovery. Starting around 2016, researchers with a nonprofit called Open Philanthropy had begun compiling research files on catastrophic biological risks. The organization, which rebranded as Coefficient Giving in 2025, funds projects across a range of focus areas; it adheres to a divisive philanthropic philosophy called effective altruism, which advocates giving money to projects with the highest potential benefit to the most people. While that might not sound objectionable, critics point out that the metrics devotees use to gauge “effectiveness” can prioritize long-term solutions while neglecting social injustices or systemic problems. 

Someone in Open Philanthropy’s bio­security group had suggested looking into the risks posed by mirror life. In 2019 the organization began funding research by Kevin Esvelt, who leads the Sculpting Evolution group at the MIT Media Lab, on biosecurity issues, including mirror life. He began reading up to see whether mirror life was something to worry about.

Esvelt made waves in 2013 for pioneering the use of CRISPR to develop a gene drive, a technology that could spread genetic changes introduced into a living organism through a whole population. Researchers are exploring its use, for example, to make mosquitoes hostile to the parasite that causes malaria—and, as a result, lower their chance of spreading it to humans. But almost immediately after he developed the tool, Esvelt argued against using it for profit, at least until proper safeguards could be set and its use in fighting malaria had been established. “Do you really have the right to run an experiment where if you screw up, it affects the whole world?” he asked, in this magazine, in 2016. At the Media Lab, Esvelt leads efforts to safely develop gene drives that can be deployed locally but prevented from spreading globally. 

Esvelt says he’s often thinking about the security risks posed by self-sustaining genetically engineered technologies, and research led him to suspect that the threat of mirror organisms hadn’t been seriously interrogated. The more he learned about microbial growth rates, predator-prey and microbe-microbe interactions, and immunology, the more he began to worry that mirror organisms, if impervious to the innate defenses of natural ones, could cause unstoppable infections in the event that they escaped the lab. 

Even if the first experimental iteration of such a germ were too fragile to survive in the environment or a human body, Esvelt says, it would be a light lift to genetically engineer new, more resilient versions with existing technology. Even worse, he says, the results could be weaponized. The possible path from 2019 to global annihilation seemed almost too direct, he found. 

But he wasn’t an expert in all the scientific fields involved in research on mirror life, so he started making calls. He first described his concerns to Relman one night in February 2022, at a restaurant outside Washington, DC. Esvelt hoped Relman would tell him he was wrong, that he’d missed something over the years of gathering data. Instead, he was troubled. 

The concern spreads

When Relman returned to California, he read more about the technology, the risks, and the role of chirality in the immune system and the environment. And he consulted experts he knew well—ecologists, other microbiologists, immunologists, all of them leaders in their fields—in an attempt to assuage his concerns. “I was hoping that they’d be able to say, I’ve thought about this, and I see a problem with your logic. I see that it’s really not so bad,” he says. “At every turn, that did not happen. Something about it was new to every person.” 

The concern spread. Relman worked with Jack Szostak, a professor of chemistry at the University of Chicago, and a group of researchers to see if it was possible to make an argument that mirror life wasn’t going to wipe out humanity. Included in that group was Kate Adamala, a synthetic biologist at the University of Minnesota. She was a natural choice: Adamala had shared the initial grant from the NSF, in 2019, to explore mirror-life technologies. 

She also became convinced the risk was real—and was dumbfounded that she hadn’t seen it earlier. “I wish that one sunny afternoon we were having coffee and we realized the world’s about to end, but that’s not what happened,” she says. “I’m embarrassed to admit that I wasn’t even the one that brought up the risks first.” Through late 2023 and early 2024, the endeavor began to take on the form of a rigorous scientific investigation. Experts were presented with a hypothesis—namely, that if mirror cells were built, they would pose an existential threat—and asked to challenge it. The goal was to falsify the hypothesis. “It would be great if we were wrong,” says Vaughn Cooper, a microbiologist at the University of Pittsburgh and president-elect of the American Society for Microbiology. 

Relman says that as the chemists and biologists learned more about one another’s work and began to understand what immunologists know about how living things defend themselves, they started to connect the dots and see an emerging picture of an unstoppable synthetic threat.

Some scientists have pushed back against the doomsday scenario, suggesting that the case against mirror life offers an “inflated view of the danger.”

Timothy Hand, an immunologist at the University of Pittsburgh who hadn’t participated in the 2019 NSF meeting, wasn’t initially worried when he heard about mirror life, in 2024. “The mammalian immune system has this incredible capability to make antibodies against any shape,” he says. “Who cares if it’s a mirror?” But when he took a closer look at that process, he could see a cascade of potential problems far upstream of antibody production. Start with detection: Macrophages, which are cells the immune system uses to identify and dispatch invaders, use chiral sensing receptors on their surfaces. The proteins they use to grab on to those invaders, too, are chiral. That suggests the possibility that an organism could be infected with a mirror organism but not be able to detect it or defend against it. “The lack of innate immune sensing is an incredibly dangerous circumstance for the host,” Hand says.

By early 2024, Glass had become concerned as well. Relman and James Wagstaff, a structural biologist from Open Philanthropy, visited him at the Venter Institute to talk about the possibility of using synthetic cell technology—Glass’s specialty—to build mirror life. “At first I thought, This can’t be real,” Glass says. They walked through arguments and counterarguments. “The more this went on, the more I started feeling ill,” he says. “It made me realize that work I had been doing for much of the last 20 years could be setting the world up for this incredible catastrophe.” 

In the second half of 2024, the growing group of scientists assembled the report and wrote the policy forum for Science. Relman briefed policymakers at the White House and members of the national security community. Researchers met with the National Institutes of Health and the National Science Foundation. “We briefed the United Nations, the UK government, the government of Singapore, scientific funding organizations from Brazil,” says Glass. “We’ve talked to the Chinese government indirectly. We were trying to not blindside anybody.” 

A year and a half on, the push has had an impact. UNESCO has recommended a precautionary global moratorium on creating mirror-life cells, and major philanthropic organizations that fund science, including the Alfred P. Sloan Foundation, have announced they will not finance research leading to a mirror microorganism. The Bulletin of the Atomic Scientists highlighted considerations about mirror life in its most recent report on the Doomsday Clock. In March, the United Nations Secretary-General’s Scientific Advisory Board issued a brief highlighting the risks—noting, for example, that recent progress on building mirror molecules could reduce the cost of creating a mirror microbe. 

“I think no one really believes at this stage that we should make mirror life, based on the evidence that’s available,” says James Smith, the scientist who leads the MBDF, the nonprofit focused on assessing the risks of mirror life, which is funded by Coefficient Giving, the Sloan Foundation, and other organizations. The challenge now, Smith says, is for scientists to work with policymakers and bioethicists to figure out how much research on mirror life should be permitted—and who will enforce the rules.

Drawing the line

Not everyone is convinced that mirror organisms pose an existential threat. It’s difficult to verify predictions about how mirror microbes would fare in the immune system—or the larger world—without running experiments on them. Some scientists have pushed back against the doomsday scenario, suggesting that the case against mirror life offers an “inflated view of the danger.” Others have noted that carbohydrates called glycans already exist in both left- and right-handed forms—even in pathogens—and the immune system can recognize both of them. Experiments focused on interactions between the immune system and mirror molecules, they say, could help clarify the risks of mirror organisms and reduce uncertainty. 

Even among those convinced that the worst-case scenario is possible, researchers still disagree over where to draw the line. What inquiries should be allowed and what should be prohibited?

Andy Ellington, a biotechnologist and synthetic biologist at the University of Texas at Austin, doesn’t think mirror organisms will come to fruition anytime soon. Even if they do, he isn’t sure they will pose a threat. “If there is going to be harm done to the human race, this is about position 382 on my list,” he says. But at the same time, he says it’s a complicated issue worth studying more, and he wants to see the conversations continue: “We’re operating in a space where there’s so much unknown that it’s very difficult for us to do risk assessment.” 

Even among those convinced that the worst-case scenario is possible, researchers still disagree over where to draw the line. What inquiries should be allowed and what should be prohibited? 

Adamala, of the University of Minnesota, and others see a natural line at ribosomes, the cellular factories that transform chains of amino acids into proteins. These would be a critical ingredient in creating a self-replicating organism, and Adamala says the path to getting there once mirror ribosomes are in place would be pretty straightforward. But Zhu, at Westlake, and others counter that it’s worth developing mirror ribosomes because they could possibly produce medically useful peptides and proteins more efficiently than traditional chemical methods. He sees a clear distinction, and a foundational gap, between that kind of technology and the creation of a living synthetic organism. “It is crucial to distinguish mirror-image molecular biology from mirror-image life,” he says. That said, he points out that many synthetic molecules and organisms containing unnatural components, including but not limited to the mirror-image subset, might pose health risks. Researchers, he says, should focus on developing holistic guidelines to cover such risks—not just those from mirror molecules. 

Even if the exact risk remains uncertain, Esvelt remains more convinced than ever that the work should be paused, perhaps indefinitely. No one has taken a meaningful swing at the hypothesis that mirror life could wipe out everything, he says. The primary uncertainties aren’t around whether mirror life is dangerous, he points out; they have more to do with identifying which bacterium—including what genes it encodes, what it eats, how it evades the immune system’s sentinels—could lead to the most serious consequences. “The risk of losing everything, like the entire future of humanity integrated over time, is not worth any small fraction of the economy. You just don’t muck around with existential risk like that,” he says. 

In some ways, scientists have been here before, working out rules and limits for research. Two years after the start of the covid-19 pandemic, for example, the World Health Organization published guidelines for managing risks in biological research. But the history is much deeper: Horrific episodes of human experimentation led to the establishment of institutional review boards to provide ethical oversight. In the early 1970s, in response to concerns over lab-acquired infections and growing use of biological warfare, the US Centers for Disease Control and Prevention established biohazard safety levels (BSLs), which govern work on potentially dangerous biological experiments.

And in 1975—at the dawn of recombinant DNA research, which allows researchers to put genetic material from one organism into another—geneticists met at the Asilomar conference center in Pacific Grove, California, to hammer out rules governing the work. There were concerns over what would happen if some virus or bacterium, genetically engineered to have traits that would make it particularly dangerous for people, escaped from a lab. Scientists agreed to self-imposed restrictions, like a moratorium on research until new safety guidelines were in place. As a result of the meeting, in June 1976 the NIH issued rules that, among other things, categorized the risks associated with rDNA experiments and aligned them with the newly adopted BSL system.

Asilomar is often hailed as a successful model for scientific self-governance. But that perception reflects a tendency to recall the meeting through a nostalgic haze. “In fact, it was incredibly messy and human,” says Luis Campos, a historian of science at Rice University. Equally brilliant Nobelists argued on either side of the question of whether to rein in rDNA research. Technical discussions dominated; talks about who would be affected by the technology were missing. The meeting didn’t start establishing guidelines, says Campos, until the lawyers mentioned liability and lab leaks. 

For now it’s unclear whether these examples of self-­governance, which arose from the demonstrated risks of existing technologies, hold useful lessons for the mirror-life community. Three competing images of the future are coming into focus: Mirror life might not be possible, it might be possible but not threatening, or it might be possible and capable of obliterating all life on Earth. 

Scientists may be censoring themselves out of fear and speculation. To some, shutting down the work seems necessary and urgent; to others, it is unnecessarily limiting. What’s clear is that the question of what to do about mirror life has been both illuminating and disorienting, pushing scientists to interrogate not only their current research but where it might lead. This is uncharted territory. 

Stephen Ornes is a science writer based in Nashville, Tennessee.

Correction (April 15): An earlier version of this article incorrectly stated that David Relman briefed the National Security Agency. Relman says he briefed members of the national security community.

What’s in a name? Moderna’s “vaccine” vs. “therapy” dilemma

Is it the Department of Defense or the Department of War? The Gulf of Mexico or the Gulf of America? A vaccine—or an “individualized neoantigen treatment”?

That’s the Trump-era vocabulary paradox facing Moderna, the covid-19 shot maker whose plans for next-generation mRNA vaccines against flus and emerging pathogens have been dashed by vaccine skeptics in the federal government. Canceled contracts and unfriendly regulators have pushed the Massachusetts-based biotech firm to a breaking point. Last year, Robert F. Kennedy Jr., head of the Department of Health and Human Services, zeroed in on mRNA, unwinding support for dozens of projects—including a $776 million award to Moderna for a bird flu vaccine. By January, the company was warning it might have to stop late-stage programs to develop vaccines against infections altogether.

That raises the stakes for a second area of Moderna’s research. In a partnership with Merck, it’s been using its mRNA technology to destroy tumors through a very, very promising technique known as a cancer vacc—

“It’s not a vaccine,” a spokesperson for Merck jumped in before the V-word could leave my mouth. “It’s an individualized neoantigen therapy.”

Oh, but it is a vaccine. And here’s how it works. Moderna sequences a patient’s cancer cells to find the ugliest, most peculiar molecules on their surface. Then it packages the genetic code for those same molecules, called neoantigens, into a shot. The patient’s immune system has its orders: Kill any cells with those yucky surface markers.

Mechanistically, it’s similar to the covid-19 vaccines. What’s different, of course, is that the patient is being immunized against a cancer, not a virus.

And it looks like a possible breakthrough. This year, Moderna and Merck showed that such shots halved the chance that patients with the deadliest form of skin cancer would die from a recurrence after surgery.

In its formal communications, like regulatory filings, Moderna hasn’t called the shot a cancer vaccine since 2023. That’s when it partnered up with Merck and rebranded the tech as individualized neoantigen therapy, or INT. Moderna’s CEO said at the time that the renaming was to “better describe the goal of the program.” (BioNTech, the European vaccine maker that’s also working in cancer, has shifted its language too, moving from “neoantigen vaccine” in 2021 to “mRNA cancer immunotherapies” in its latest report.)

The logic of casting it as a therapy is that patients already have cancer—so it’s a treatment as opposed to a preventive measure. But it’s no secret what the other goal is: to distance important innovation from vaccine fearmongering, which has been inflamed by high-ranking US officials. “Vaccines are maybe a dirty word nowadays, but we still believe in the science and harnessing our immune system to not only fight infections, but hopefully to also fight … cancers,” Kyle Holen, head of Moderna’s cancer program, said last summer during BIO 2025, a big biotech event in Boston.

Not everyone is happy with the word games. Take Ryan Sullivan, a physician at Massachusetts General Hospital who has enrolled patients in Moderna’s trials. He says the change raises questions over whether trial volunteers are being properly informed. “There is some concern that there will be patients who decline to treat their cancer because it is a vaccine,” Sullivan told me. “But I also felt it was important, as many of my colleagues did, that you have to call it what it is.”

But is it worth going to the mat for a word? Lillian Siu, a medical oncologist at the Princess Margaret Cancer Centre, in Toronto, who has played a role in safety testing for the new shots, watches US politics from a distance. She believes name change is acceptable “if it allows the research to continue.”

Holen told me the doctors complaining to Moderna were basically motivated by a desire to defend vaccines—which are, of course, among the greatest public health interventions of all time. They wanted the company to stand strong. 

But that’s not what’s happening. When Moderna’s latest results were published in February, the paper’s main text didn’t use the word “vaccine” at all. It was only in the footnotes that you could see the term—in the titles of old papers and patents.

All this could be a sign that Kennedy’s strategy is working. His agencies often appear to make mRNA vaccines a focus of people’s worries, impede their reach, devalue them for companies, and sideline their defenders. 

Still, Moderna’s strategy may be working too. So far, at least, the government hasn’t had much to say about the company’s cancer vacc— I mean, its individualized neoantigen therapy.

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.

Inside the stealthy startup that pitched brainless human clones

After operating in secrecy for years, a startup company called R3 Bio, in Richmond, California, suddenly shared details about its work last week—saying it had raised money to create nonsentient monkey “organ sacks” as an alternative to animal testing.

In an interview with Wired, R3 listed three investors: billionaire Tim Draper, the Singapore-based fund Immortal Dragons, and life-extension investors LongGame Ventures.

But there is more to the story. And R3 doesn’t want that story told.

MIT Technology Review discovered that the stealth startup’s founder John Schloendorn also pitched a startling, medically graphic, and ethically charged vision for what he’s called “brainless clones” to serve the role of backup human bodies.

Imagine it like this: a baby version of yourself with only enough of a brain structure to be alive in case you ever need a new kidney or liver.

Or, alternatively, he has speculated, you might one day get your brain placed into a younger clone. That could be a way to gain a second lifespan through a still hypothetical procedure known as a body transplant.

The fuller context of R3’s proposals, as well as activities of another stealth startup with related goals, have not previously been reported. They’ve been kept secret by a circle of extreme life-extension proponents who fear that their plans for immortality could be derailed by clickbait headlines and public backlash.

And that’s because the idea can sound like something straight from a creepy science fiction film. One person who heard R3’s clone presentation, and spoke on the condition of anonymity, was left reeling by its implications and shaken by Schloendorn’s enthusiastic delivery. The briefing, this person said, was like a “close encounter of the third kind” with “Dr. Strangelove.”

A key inspiration for Schloendorn is a birth defect in which children are born missing most of their cortical hemispheres; he’s shown people medical scans of these kids’ nearly empty skulls as evidence that a body can live without much of a brain. 

And he’s talked about how to grow a clone. Since artificial wombs don’t exist yet, brainless bodies can’t be grown in a lab. So he’s said the first batch of brainless clones would have to be carried by women paid to do the job. In the future, though, one brainless clone could give birth to another.

Last Monday, the same day it announced itself to the world in Wired, R3 sent us a sweeping disavowal of our findings. It said Schloendorn “never made any statement regarding hypothetical ‘non-sentient human clones’ [that] would be carried by surrogates.” The most overarching of these challenges was its insistence that “any allegations of intent or conspiracy to create human clones or humans with brain damage are categorically false.”

But even Schloendorn and his cofounder, Alice Gilman, can’t seem to keep away from the topic. Just last September, the pair presented at Abundance Longevity, a $70,000-per-ticket event in Boston organized by the anti-aging promoter Peter Diamandis. Although the presentation to about 40 people was not recorded and was meant to be confidential, a copy of the agenda for the event shows that Schloendorn was there to outline his “final bid to defeat aging” in a session called “Full Body Replacement.”

According to a person who was there, both animal research and personal clones for spare organs were discussed. During the presentation, Gilman and Schloendorn even stood in front of an image of a cloning needle. Pressed on whether this was a talk about brainless clones, Gilman told us that while R3’s current business is replacing animal models, “the team reserves the right to hold hypothetical futuristic discussions.”

MIT Technology Review found no evidence that R3 has cloned anyone, or even any animal bigger than a rodent. What we did find were documents, additional meeting agendas, and other sources outlining a technical road map for what R3 called “body replacement cloning” in a 2023 letter to supporters. That road map involved improvements to the cloning process and genetic wiring diagrams for how to create animals without complete brains. 

light passing through an infant's skull
A child with hydranencephaly, a rare condition in which most of the brain is missing. Could a human clone also be created without much of a brain as an ethical source of spare organs?
DIMITRI AGAMANOLIS, M.D. VIA WIKIPEDIA

A main purpose of the fundraising, investors say, was to support efforts to try these techniques in monkeys from a base in the Caribbean. That offered a path to a nearer-term business plan for more ethical medical experiments and toxicology testing—if the company could develop what it now calls monkey “organ sacks.” However, this work would clearly inform any possible human version. 

Though he holds a PhD, Schloendorn is a biotech outsider who has published little and is best known for having once outfitted a DIY lab in his Bay Area garage. Still, his ties to the experimental fringe of longevity science have earned him a network in Silicon Valley and allies at a risk-taking US health innovation agency, ARPA-H. Together with his success at raising money from investors, this signals that the brainless-clone concept should be taken seriously by a wider community of scientists, doctors, and ethicists, some of whom expressed grave concerns. 

“It sounds crazy, in my opinion,” said Jose Cibelli, a researcher at Michigan State University, after MIT Technology Review described R3’s brainless-clone idea to him. “How do you demonstrate safety? What is safety when you’re trying to create an abnormal human?”

Twenty-five years ago, Cibelli was among the first scientists to try to clone human embryos, but he was trying to obtain matched stem cells, not make a baby. “There is no limit to human imagination and ways to make money, but there have to be boundaries,” he says. “And this is the boundary of making a human being who is not a human being.” 

“Feasibility research”

Since Dolly the sheep was born in 1996, researchers have cloned dogs, cats, camels, horses, cattle, ferrets, and other species of mammal. Injecting a cell from an existing animal into an egg creates a carbon-copy embryo that can develop, although not always without problems. Defects, deformities, and stillbirths remain common. 

Those grave risks are why we’ve never heard of a human clone, even though it’s theoretically possible to create one. 

But brainless clones flip the script. That’s because the ultimate aim is to create not a healthy person but an unconscious body that would probably need life support, like a feeding tube, to stay alive. Because this body would share the DNA of the person being copied, its organs would be a near-perfect immunological match. 

Backers of this broad concept argue that a nonsentient body would be ethically acceptable to harvest organs from. Some also believe that swapping in fresh, young body parts—known as “replacement”—is the likeliest path to life extension, since so far no drug can reverse aging. 

And then there’s the idea of a complete body transplant. “Certainly, for the cryonics patients, that sounds like something really promising,” says Anders Sandberg, a prominent Swedish transhumanist and expert in the ethics of future technologies. He notes that many people who opt to be stored in cryonic chambers after death choose the less expensive “head only” option, so “there might be a market for having an extra cloned body.”

MIT Technology Review first approached Schloendorn two years ago after learning he’d led a confidential online seminar called the Body Replacement Mini Conference, in which he presented “recent lab progress towards making replacement bodies.” 

According to a copy of the agenda, that 2023 session also included a presentation by a cloning expert, Young Gie Chung. And there was another from Jean Hébert, who was then a professor at the Albert Einstein College of Medicine and is now a program manager at ARPA-H, where he oversees a project to use stem cells to restore damaged brain tissue. Hébert popularized the so-called replacement solution to avoiding death in a 2020 book called Replacing Aging

In an interview prior to joining the government in 2024, Hébert described an informal but “very collaborative” relationship with Schloendorn. The overall idea was that to stop aging, one of them would determine how to repair a brain, while the other would figure out how to create a body without one. “It’s a perfect match, right? Body, brain,” Hébert told MIT Technology Review at the time. 

Schloendorn, by working outside the mainstream, had the huge advantage of “not being bound by getting the next paper out, or the next grant,” Hébert said, adding, “It’s such a wonderful way of doing research. It’s just clean and pure.” R3 now appears on the ARPA-H website on a list of prospective partners for Hébert’s program.

In a LinkedIn message exchanged with Schloendorn that same year, he described his work as “feasibility research in body replacement.”

“We will try to do it in a way that produces defined societal benefits early on, and we need to be prepared to take no for an answer, if it turns out that this cannot be done safely,” Schloendorn wrote at the time. He declined an interview then, saying that before exiting stealth mode, he wants to be sure the benefits are “reasonably grounded in reality.”

That could prove challenging. While body-part replacement sounds logical, like swapping the timing belt on an old car, in reality there’s scant evidence that receiving organs from a younger twin would make you live any longer. 

A complete body transplant, meanwhile, would probably be fatal, at least with current techniques. In the latest test of the concept, published last July, Russian surgeons removed a pig’s head and then sewed it back on. The animal did live—breathing weakly and lapping water from a syringe. But because its spinal cord had been cut, it was otherwise totally paralyzed. (As yet, there’s no proven method to rejoin a severed spinal cord.) In an act of mercy, the doctors ended the pig’s life after about 12 hours. 

Even some of R3’s investors say the endeavor is a risky, low-odds project, on par with colonizing Mars. Boyang Wang, head of Immortal Dragons, has spoken at longevity conferences about body-swapping technology, referring to the chance that “when the time comes, you can transplant your brain into a new body.” Wang confirmed in a January Zoom call that he’d been referring to R3 and that he invested $500,000 in the company during a 2024 fundraising round.

But since making his investment, Wang says, he’s become less bullish. He now views whole-body transplant as “very infeasible, not even very scientific” and “far away from hope for any realistic application.” 

Still, he says, the investment in R3 fits with his philosophy of making unorthodox bets that could be breakthroughs against aging. “What can really move the needle?” he asks. “Because time is running out.”

Stealth mode

Clonal bodies sit at the extreme frontier of an advancing cluster of technologies all aimed at growing spare parts. Researchers are exploring stem cells, synthetic embryos, and blob-like organoids, and some companies are cloning genetically engineered pigs whose kidneys and hearts have already been transplanted into a few patients. Each of these methods seeks to harness development—the process by which animal bodies naturally form in the womb—to grow fully functional organs. 

There’s even a growing cadre of mainstream scientists who say nonsentient bodies could solve the organ shortage, if they could be grown through artificial means. Two Stanford University professors, calling these structures “bodyoids,” published an editorial in favor of manufacturing spare human bodies in MIT Technology Review last year. While that editorial left many details to the imagination, they called the idea “at least plausible—and possibly revolutionary.” 

“There are a lot of variations on this where they’re trying to find a socially acceptable form,” says George Church, a Harvard University professor who advises startups in the field. But Church says gestating an entire body is probably taking things too far, especially since nearly all patients on transplant lists are waiting for just a single organ, like a heart or kidney. 

“There’s almost no scenario where you need a whole body,” he says. “I just think even if it’s someday acceptable, it’s not a good place to start.” For the moment, Church says, brainless human bodies are “not very useful, in addition to being repulsive.”

That’s arguably why body replacement technology still feels risky to talk about, even among life-extension enthusiasts who are otherwise ready to inject Chinese peptides or have their bodies cryogenically frozen. “I think it’s exciting or interesting from a scientific perspective, but I think the world is not fully ready for it yet,” says Emil Kendziorra, CEO of Tomorrow Bio, a company in Berlin that stores bodies at -196 °C in the hope they can be restored to life in the future. 

“Everybody’s like, yeah, you know, cryopreservation makes total sense,” he says. “And then you talk about total body replacement. And then everybody’s like, Whoa, whoa, whoa.”

Even so, “replacement” technology has found a fervent base of support among a group of self-described “hardcore” longevity adherents who follow a philosophy called Vitalism, which holds that society should redirect resources toward achieving unlimited lifespans. The growing influence of this movement, achieved through lobbying, investment, recruiting, and public messaging, was detailed earlier this year in MIT Technology Review.

Last spring, during a meetup for this community, Kendziorra was among the attendees at an invite-only “Replacement Day” gathering that took place off the public schedule. It was where more radical ideas could be discussed freely, since to some in the Vitalist circle, replacing body parts has emerged as the most plausible, least expensive way to beat death. 

At least that was the conclusion of a road map for anti-aging technology produced by one Vitalist group, the Longevity Biotech Fellowship, which reckoned that a proof-of-concept human clone lacking a neocortex would cost $40 million to create—a tiny amount, relatively speaking. 

Its report cited the existence of two stealth companies working on cloning whole nonsentient bodies, although it took care not to name them. If these companies’ activities become public, “there will be a huge backlash—people will hate it,” the entrepreneur Kris Borer said while presenting the road map at a French resort last August. 

“There are a ton of dystopian movies and novels about this kind of stuff. That is why I didn’t talk about any of the companies working on it. They are trying to hide from public attention,” he said. “We have to have the angel investors and other people invest kind of in secret until things are ready.” 

Borer did say what he sees as the best way to go public: first, to slowly ease body replacement into society’s awareness by disclosing more limited aims, which will be palatable. “We are not going to start with Let’s clone you and give you a body. We are going to start with Let’s solve the organ shortage,” he said. “Eventually people will warm up to it, and then we can go to the more hardcore stuff.”

In an interview earlier this month, Borer declined to name the companies involved in his immortality road map, or to say if R3 is one of them. But we did identify one additional stealthy startup, this one focused on replacing a person’s internal organs, not the whole body. Called Kind Biotechnology, it is a New Hampshire–based company headed by the anti-aging researcher Justin Rebo, a sometime collaborator of Schloendorn’s.

Fig 13 from a patent application
A patent image from Kind Biotechnology shows a mouse pup engineered to lack anatomical features (left) next to a normal animal. The company’s goal is to grow organ “sacks” with a “complete lack of ability to feel, think, or sense.”
WO2025260099 VIA WIPO

According to patent applications filed by the company, Rebo’s team is working to create animals with a “complete lack of ability to feel, think, or sense the environment.” Images included in the patents show mice the company produced that lack a complete brain, and others that don’t have faces or limbs. They did that by deleting genes in embryos using the gene-editing technology CRISPR with the goal of creating a “sack of organs that grows mostly on its own,” with only a minimal nervous system. A cartoon rendering submitted to the patent office shows what looks like a fleshy duffel bag connected to life support tubes. 

In an email, Rebo said his company is working on an “ethical and scalable” way to create animal organs for experimental transplant to humans. He notes that “thousands die while waiting” for an organ. 

Some of Kind’s patent applications do cover the possibility of producing these organ sacks from human cells. Rebo says that’s more of a speculative possibility. But he does see his work as part of the “replacement” approach to longevity. Firstly, that’s because a “scalable production of young, high-quality organs” would let surgeons try transplants in more types of patients, including many with heart disease in old age who aren’t candidates for a transplant now. 

“With abundant high-quality organs, replacement could become a direct form of rejuvenation by replacement of failing parts,” he says. 

And Rebo imagines that simultaneously replacing multiple internal organs (grown together in the sack) could have even broader rejuvenating effects. “Ultimately, replacing failing parts is a direct path to extending healthy human lifespan,” he says. 

Church, who agreed earlier this year to advise Kind Bio, sees this work as part of an effort to “nudge” these technologies “toward something that is more useful and more acceptable from the get-go,” he says. “And then let’s see how society responds to that—rather than jumping to the most repulsive and most useless form, which some of them seem to be aiming for.” 

“There’s one way to find out”

People who know Schloendorn describe a dynamo-like presence who is “100% dedicated” to the goal of extreme life extension. In 2006, he penned a paper in a bioethics journal outlining why the “desire to live forever” is rational, and his doctoral research at the University of Arizona was sponsored by a longevity research organization called the SENS Foundation.  

He’s also well connected. In an interview, Aubrey de Grey, the influential and controversial fundraiser and prognosticator who cofounded SENS, called Schloendorn “one of my protégés.” And around 2010, Peter Thiel reportedly invested $1.5 million in ImmunePath, a company started by Schloendorn to develop stem-cell treatments, though it soon failed. (A representative for Thiel did not respond to a request to confirm the figure.)

By 2021, Schloendorn had moved on, founding R3 Biotechnologies. He began to circulate the body replacement idea and discuss a step-by-step scheme to get there: assess techniques in the lab first, then in monkeys, and maybe eventually in humans. 

A 2023 “letter to stakeholders” signed by Schloendorn begins by saying that “body replacement cloning will require multicomponent genetic engineering on a scale that has never been attempted in primates.” Fortunately, it adds, molecular techniques for “brain knockout” are well known in mice and should also be expected to function in “birthing whole primates,” a class that includes both monkeys and humans. 

Would it work? “There’s one way to find out,” the letter says. 

Wang, the investor at Immortal Dragons, says he put money into R3 after it showed him it is possible to create mice without complete brains. “There were imperfections, but the resulting mice survived, grew up, and to me, that is a pretty strong experiment,” he says; it was evidence enough for him to fund R3’s attempt to “replicate the result in primates.” 

(In its emailed statement, R3 said the company and its founders “never produced any degree of brain alterations in any species, did not attempt to do so, did not hire another party to do so, and have no specific plans to do so in the future.” It added: “We do not work with live non-human primates.”) 

The bigger technical obstacle, though, remains the cloning. Out of 100 attempts to clone an animal, only a few typically succeed. That fact alone makes cloning a human—or a monkey—almost infeasible.

But R3 does seem to have made an effort to tackle the efficiency problem. In one document reviewed by MIT Technology Review, it claims to have implemented improvements to the basic procedure in rodents, referencing a protein, called a histone demethylase, that helps erase a cell’s genetic memory. Adding it can greatly increase the chance that the cell will form a cloned embryo after being injected into an egg in the lab.

Those molecules were used in the first successful cloning of a monkey, which occurred in 2018 in China. But it still wasn’t easy—in fact, it was a huge and costly effort to handle a crowd of monkeys in estrus and perform IVF on them. According to Michigan State’s Cibelli, monkey cloning remains nearly impossible, at least on US territory, just because it’s “unaffordable.”

Nevertheless, success in monkeys did help prove, at least biologically, that human reproductive cloning could be possible. 

The company may also have tried to tackle a second long-standing obstacle to cloning: defects in how the placenta works. Because of such problems, some cloned animals die quickly after birth.

The R3 document refers to a “birthing fix” it developed to further improve the cloning success rate. While MIT Technology Review didn’t learn what R3’s process entails, we found a reference to it on the LinkedIn page of Maitriyee Mahanta, a scientist who cosigned the 2023 letter to R3 stakeholders and is a former research assistant to Hébert. (We were unable to reach Mahanta for comment.)

Her page described her current role as “molecular lead” studying cloning, “birth rate fixing,” and cortical development using cells from nonhuman primates. Her job affiliation is given as the Longevity Escape Velocity Foundation, a nonprofit where de Grey is the president and chief science officer. But de Grey says his foundation only arranged a work visa for Mahanta as part of a partnership “with the company she actually spends her time at.”

Like several other people interviewed for this article, de Grey made a resourceful effort to avoid directly confirming the existence of R3 when we spoke, while at the same time freely discussing theoretical aspects of body cloning technology. For instance, he talked about ways to shorten the wait for your double to grow up to a size suitable for organ harvesting; a further genetic mutation could be added to cause “central precocious puberty” in the clone, he said. This condition causes a growth spurt, even pubic hair, in a toddler. 

Cloning dictators

Who would clone a body and pay to keep it alive for years, until it’s needed? The first customers for this costly technology (if it ever proves feasible) would likely be the ultra-rich or the ultra-powerful. 

Indeed, somehow the world’s top dictators seem to have gotten the memo about replacement parts. In September, a hot mic picked up a conversation between Russian president Vladimir Putin and Chinese leader Xi Jinping as they walked through Beijing with North Korean autocrat Kim Jong Un; in the exchange, the Russian speculated on life extension.  

“Biotechnology is continuously developing. Human organs can be continuously transplanted. The longer you live, the younger you become, and [you can] even achieve immortality,” Putin said through an interpreter.

“Some predict that in this century, humans will live to 150 years old,” Xi responded agreeably.

How the leaders learned of these possibilities is unknown. But scenarios involving dictators are a constant topic among body replacement enthusiasts. 

“There are companies working on this. They are in stealth—we can’t reveal too much about them—but the general concept on this is if you didn’t have any ethical qualms, you could do most of it today,” Will Harborne, the chief investment officer of LongGame Advisors, said last year, during an interview with the podcaster Julian Issa. “If you were the dictator of some country and wanted a clone of yourself, you can already go grow one. You can create a cloned embryo of yourself, you can get a surrogate to carry it to term, and you can grow [a] body until age 18 with a brain, and eventually, if you were a dictator, you could kill them and try to transplant your head on their body.”

“And now no one is suggesting you do that—it’s very unethical—but most of the technology is there,” he said. He noted that the reason for removing the cortex of a clone created for such a purpose is that “we don’t want to kill other people to live forever.” 

Harborne subsequently confirmed to MIT Technology Review that the fund invested $1 million in R3 about a year and a half ago.

In order to make the body replacement process ethical, the clone’s brain needs to be stunted so it lacks consciousness. That is where the interest in birth defects comes in. Remarkable medical scans of kids with a rare condition, hydranencephaly, show a total absence of the cerebral hemispheres. Yet if they are cared for, they may be able to live into their 20s, even though they cannot speak or engage in purposeful movement. 

The technical question, then, is how to intentionally produce such a condition in a clone. Sandberg, the futurist, says he’s visited R3’s lab, talked to Gilman, and sat through a presentation about how genetic engineering can be used to shape brain growth. Previous work has shown that by adding a toxic gene, it is possible to kill specific cell types in a growing embryo but spare others, leading to a mouse without a neocortex.

While Sandberg isn’t an expert in biotechnology, he says R3’s theory looked sensible to him. “I think it’s possible to actually prevent the development of the brain well enough that you can say ‘Yeah, there is almost certainly no consciousness here,’” Sandberg says. “Hence, there can’t be any suffering, or any individual, in a practical sense.”

“I think the overall aim—actually, it looks ethically pretty good,” he says. 

Two monkeys with stuffed animals in a plastic research container
Monkeys were successfully cloned in China for the first time in 2018. Although it was was a costly and difficult undertaking, the feat suggested human cloning is biologically possible.
QIANG SUN AND MU-MING POO/CHINESE ACADEMY OF SCIENCES VIA AP

Yet it could be difficult to really determine where consciousness starts and ends. Under current medical standards, taking the organs of people with hydranencephaly isn’t allowed because they don’t meet the standard of brain death: They have a functioning brain stem. An even more serious problem is evidence that the brain stem alone produces a basic form of consciousness. If that is so, says Bjorn Merker, a neuroscientist who surveyed caretakers of more than a hundred children with hydranencephaly, a plan “to harvest organs from organisms modeled on this condition would be unethical.”

Of course, the most extreme version of the replacement dream isn’t just to take organs. It’s to take over the body entirely. Sergio Canavero, a controversial Italian surgeon who has proposed head and brain transplants, says he was approached for advice by Schloendorn and others a few years ago. “They told me they were looking at a head transplant on a two- or three-year-old,” he says. “I stopped short. How could you even conceive of that? The biomechanical compatibility is not there. You have to wait until at least 14. And I would say 16. It was very clear to me these guys are not surgeons—they are biologists.” 

Canavero says he’s not opposed to cloning bodies for transplant—he thinks it could work. “But if you want to use a clone,” he says, “it must be a nonsentient clone. Otherwise it’s murder, a homicide.”    

MIT Technology Review has not found any evidence that R3 has yet created an “organ sack,” much less a brainless human clone. And there are many reasons to believe their hypothetical future of “full body replacement” will never come to pass—that it is just a live-forever fantasy.

“There are so many barriers,” says Cibelli. It’s a long list: Human cloning is illegal in many countries, it’s unsafe, and few competent experts would want, or dare, to participate. And then there’s the inconvenient fact that for now, there’s no way to grow a brainless clone to birth, except in a woman’s body. Think about it, Cibelli says: “You’d have to convince a woman to carry a fetus that is going to be abnormal.”

Sandberg agrees that is where things could start to get tricky. “The problem here, of course,” he says, “is that the yuck factor is magnificent.”

A woman’s uterus has been kept alive outside the body for the first time

<div data-chronoton-summary="

  • A uterus survived outside the body for the first time: Scientists in Spain kept a donated human uterus alive for 24 hours using a machine that mimics the body’s circulatory system, pumping modified blood through the organ.
  • The researchers hope to someday keep a uterus alive for a full menstrual cycle: Researchers also want to study how embryos implant into the uterine lining, by observing the process in a living organ outside the body.
  • Bigger ambitions are already on the table: The team’s founder envisions a future where a machine like this could gestate a human fetus entirely outside the body, offering a new path to parenthood for those unable to carry a pregnancy.

” data-chronoton-post-id=”1134766″ data-chronoton-expand-collapse=”1″ data-chronoton-analytics-enabled=”1″>

“Think of this as a human body,” says Javier González.

In front of me is essentially a metal box on wheels. Standing at around a meter in height, it reminds me of a stainless-steel counter in a restaurant kitchen. It is covered in flexible plastic tubing—which act as veins and arteries—connecting a series of transparent containers, the organs of this machine.

What makes it extra special is the role of the cream-colored tub that sits on its surface. Ten months ago, González, a biomedical scientist who developed the device with his colleagues at the Carlos Simon Foundation, carefully placed a freshly donated human uterus in the tub. The team connected it to the device’s tubes and pumped in modified human blood.

The device kept the uterus alive for a day—a new feat that could represent the first step to the long-term maintenance of uteruses outside the human body. The work has not yet been published. 

The team members want to keep donated human uteruses alive long enough to see a full menstrual cycle. They hope this will help them study diseases of the uterus and learn more about how embryos burrow their way into the organ’s lining at the start of a pregnancy. They also hope that future iterations of their device might one day sustain the full gestation of a human fetus.

The machine is technically called PUPER, which stands for “preservation of the uterus in perfusion.” But González’s colleague Xavier Santamaria says the team has adopted a nickname for it: “We call it ‘Mother.’”

The organ in the machine

González and Santamaria, medical vice president of the Carlos Simon Foundation, demonstrated how the device might work when I visited the foundation in Valencia, Spain, earlier this month (although it held no organs on that day). 

Both are interested in learning more about implantation, the moment at which an embryo attaches itself to the lining of a uterus—essentially, the very first moment of pregnancy.

The foundation’s founder and director, Carlos Simon, believes it’s a sticking point in IVF: Scientists have made many improvements to the technology over the years, but the failure of embryos to implant underlies plenty of unsuccessful IVF cycles, he says. Being able to carefully study how the process works in a real, living organ might give the team a better idea of how to prevent those failures.

a person in gloves stands next to a machine with lots of tubing coming in and out of the metal exterior

JESS HAMZELOU
a sheep uterus resting on gauze connected to several tubes

JAVIER GONZALES/CARLOS SIMON FOUNDATION

Javier González demonstrates the perfusion machine. A previous iteration of the device kept a sheep’s uterus (right) alive for a day.

The team took inspiration from advances in technologies designed to maintain donated organs for transplantation. In recent years, researchers around the world have created devices that deliver nutrients and filter waste so that organs can survive longer after being removed from donors’ bodies.

The main goal here is to buy time. A human organ might last only a matter of hours outside the body, so a transplant may require frantic preparation for the recipient, sometimes in the middle of the night. With a little more time, doctors could find better donor-patient matches and potentially test the quality of donated organs.

This approach is called normothermic or machine perfusion, and it is already being used clinically for some liver, kidney, and heart transplants.

The team at the Carlos Simon Foundation built a similar machine for uteruses. A blood bag hangs on one side. From there, blood is ferried via plastic tubing to a pump, which functions as the heart. The pump shunts the blood through an oxygenator, which adds oxygen and removes carbon dioxide as the lungs would in a human body.

The blood is warmed and passed through sensors that monitor the levels of glucose and oxygen, along with other factors. It passes through a “kidney” to remove waste. And finally the blood reaches the uterus, hooked up to its own plastic “arteries” and “veins.” The organ itself sits at a tilt, just as in the body, and is kept in a humid environment to stay moist.

Mother’s first uterus

The team first began testing an early prototype of the device with sheep uteruses around four years ago. That meant carting the machine to an animal research center in Zaragoza, around 200 miles away. Over the course of the preliminary study, veterinary surgeons removed the uteruses of six sheep and hooked them up to the machine. They kept each uterus alive for a day, using blood from the same animals.

After the sheep experiments, the researchers carted their machine back to Valencia and modified it to achieve its current incarnation, “Mother.” They started working with a local hospital that performed hysterectomies. And in May last year, they were offered their first human uterus.

The team needed to be quick. “You need to put [the uterus in the machine] within a couple of hours, maximum, of the extraction,” says Santamaria. He and his colleagues also needed to connect the uterus’s blood vessels to the tubing delicately, taking care to avoid any blockages (clotting is a major challenge in organ perfusion). The organ was hooked up to human blood obtained from a blood bank.

It seemed to work—at least temporarily. “We kept it alive for one day,” says Santamaria.

“As a proof of concept, it is impressive,” says Keren Ladin, a bioethicist who has focused on organ transplantation and perfusion at Tufts University. “These are early days.”

It might not sound like much, but 24 hours is a long time for an organ to be out of the body. Maintaining a donated uterus for that long could expand the options for uterus transplant, a fairly new procedure offered to some people who want to be pregnant but don’t have a functional uterus, says Gerald Brandacher, professor of experimental and translational transplant surgery at the Medical University of Innsbruck in Austria.

“It is better than what we currently have, because we have only a couple of hours,” he says. So far, most uterus transplants have been planned operations involving organs from living donors. A technology like this could allow for the use of more organs from deceased donors, he says.

That work is “not in the immediate pipeline” for the team in Spain, says Santamaria. “We are working on other problems.”

Pregnancy in the lab?

Santamaria, González, and their colleagues are more interested in using sustained human uteruses for research. 

They’ve mounted a camera to a wall in the corner of the room, pointed at their machine. It allows the team to monitor “Mother” remotely, and to check if any valves disconnect. (That happened once before—a spike in pressure caused the blood bag to come loose, spilling a liter of blood on the floor, Santamaria says.)

They’d like to be able to keep their uteruses alive for around 28 days to study the menstrual cycle and disorders that affect the uterus, like endometriosis and fibroids.

It won’t be easy to maintain a uterus for that long, cautions Brandacher. As far as he knows, no one has been able to maintain a liver for more than seven days. “No studies out there … have shown 30-day survival in a machine perfusion circuit,” he says.

But it’s worth the effort. The team’s main interest is learning more about how embryos implant in the uterine lining at the start of a pregnancy. They hope to be able to test the process in their outside-the-body uteruses.

They won’t be allowed to use human embryos for this, says González—that would cross an ethical boundary. Instead, they plan to use embryo-like structures made from stem cells. The structures closely resemble human embryos but are created in a lab without sperm or eggs.

Simon himself has grander ambitions.

He sees a future in which a machine like “Mother” will be able to fully gestate a human, all the way from embryo to newborn. It could offer a new path to parenthood for people who don’t have a uterus, for example, or who are not able to get pregnant for other reasons.

He appreciates that it sounds futuristic, to say the least. “I don’t know if we will end up having pregnancies inside of the uterus outside of the body, but at least we are ready to understand all the steps to do that,” he says. “You have to start somewhere.”

Here’s why some people choose cryonics to store their bodies and brains after death

This week I reported on some rather unusual research that focuses on the brain of L. Stephen Coles.

Coles was a gerontologist who died from pancreatic cancer in 2014. He had spent the latter part of his career specializing in human longevity. And before he died, he decided to have his brain preserved by a cryonics facility. Today, it’s being stored at −146 °C at a center in Arizona, where it sits covered in a thin layer of frost.

Coles also tasked his longtime friend Greg Fahy with studying pieces of his brain to see how they had fared (partly because he was worried his brain might crack). Fahy, a renowned cryobiologist, has found that the brain is “astonishingly well preserved.”

But that doesn’t mean Coles could be reanimated. Over the past few years, I’ve spoken to people who run cryonics facilities, study cryopreservation, or just want to be cryogenically stored. All those I’ve spoken to acknowledge that the chance they’ll one day be brought back to life is vanishingly small. So why do they do it?

The first person to be cryonically preserved was James Hiram Bedford, a retired psychology professor who died of kidney cancer in 1967. Affiliates of the Cryonics Society of California, an organization headed by a charming TV repairman with no scientific or medical training, perfused his body with cryoproctective chemicals to protect against harmful ice formation and “quick-froze” him.

Today, Bedford’s body is still in storage at Alcor, a cryonics facility based in Scottsdale, Arizona. It’s one of a handful of organizations that offer to collect, preserve, and store a person’s whole body or just their brain—pretty much indefinitely. It’s where Coles’s brain is stored.

Both men died from cancer. Medicine could not cure them. But in the future, who knows? One of the premises of cryonics is that modern medicine will continue to advance over time. Cancer death rates have declined significantly in the US since the early 1990s. I don’t know what exactly drove Coles and Bedford to their decisions, but they might have hoped to be reanimated at some point in the future when their cancers became curable.

Others simply don’t want to die, period. Last year, I attended Vitalist Bay, a gathering for people who believe that life is good and that death is “humanity’s core problem.” Emil Kendziorra, CEO of the cryonics organization Tomorrow.Bio, spoke at the event, and a healthy interest in cryonics was obvious among the attendees.

Many of them believe that science will find a way to “obviate” aging. And some were keen on the idea of being preserved until that happens. Think of it as a way to cheat not only death but aging itself.

This sentiment might have support beyond the realms of Vitalist Bay, according to research by Kendziorra and his colleagues. In 2021, they surveyed 1,478 US-based internet users who were recruited via Craigslist. They found that men were more aware of cryonics than women, and more optimistic about its outcomes. Just over a third of the men who completed the survey expressed interest “a desire to live indefinitely.”

Still, cryonics is a niche field. Worldwide, only around 5,000 or 6,000 people have signed up for cryopreservation when they die, Kendziorra told me when we chatted at Vitalist Bay. He also told me that his company gets between 20 and 50 new signups every month.

And there are plenty of reasons why people don’t do it. A small fraction of the people who responded to Kendziorra’s survey said that they thought the idea of cryonics was dystopian, and some even said it should be illegal.

Then there’s the cost. Alcor charges $80,000 to store a person’s brain, and around $220,000 to store a whole body. Tomorrow.Bio’s charges are slightly higher. Many people, including Kendziorra himself, opt to cover this cost via a life insurance policy.

Perhaps the main reason people don’t opt for cryonic preservation is that we don’t have any way to bring people back. Bedford has been in storage for more than 50 years, Coles for more than a decade. All the scientists I’ve spoken to say the likelihood of reanimating remains like theirs is vanishingly small.

The fact that the possibility—however tiny—is above zero is enough for some, including Nick Llewellyn, the director of research and development at Alcor. As a scientist, he says, he acknowledges that the chances reanimation will actually work are “pretty low.” Still, he’s interested in seeing what the future will look like, so he has signed himself up for the cryonic preservation of his brain.

But Shannon Tessier, a cryobiologist at Massachusetts General Hospital, tells me that she wouldn’t sign up for cryonic preservation even if it worked. “It turns into a philosophical question,” she says.

“Do I want to be revived hundreds of years later when my family is gone and life is different?” she asks. “There are so many complicated philosophical, societal, [and] legal complications that need to be thought through.”

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.

This scientist rewarmed and studied pieces of his friend’s cryopreserved brain

L. Stephen Coles’s brain sits cushioned in a vat at a storage facility in Arizona. It has been held there at a temperature of around −146 degrees °C for over a decade, largely undisturbed.

That is, apart from the time, a little over a year ago, when scientists slowly lifted the brain to take photos of it. Years before, the team had removed tiny pieces of it to send to Coles’s friend. Coles, a researcher who studied aging, was interested in cryogenics—the long-term storage of human bodies and brains in the hope that they might one day be brought back to life. Before he died, he asked cryobiologist Greg Fahy to study the effects of the preservation procedure on his brain. Coles was especially curious about whether his cooled brain would crack, says Fahy.

Coles’s brain was preserved shortly after he died in 2014, but Fahy has only recently got around to analyzing those samples. He says that Coles’s brain is “astonishingly well preserved.”

“We can see every detail [in the structure of the brain biopsies],” says Fahy, who is chief scientific officer at biotech companies Intervene Immune and 21st Century Medicine (where he is also executive director). He hopes this means that Coles’s brain still stands a chance of reanimation at some point in the future.

Other cryobiologists are less optimistic. “This brain is not alive,” says John Bischof, who works on ways to cryopreserve human organs at the University of Minnesota.

Still, Fahy’s research could help provide a tool to neuroscientists looking for new ways to study the brain. And while human reanimation after cryopreservation may be the stuff of science fiction, using the technology to preserve organs for transplantation is within reach.

Banking a brain

Coles, a gerontologist who spent the latter part of his career studying human longevity, opted to have his brain cryogenically preserved when he died of pancreatic cancer.

After he was declared dead, Coles’s body was kept at a low temperature while he was transferred to Alcor, a cryonics facility in Arizona. His head was removed from his body, and a team perfused his brain with “cryoprotective” chemicals that would prevent it from freezing. They then removed it from his skull and cooled it to −146 °C.

Coles had another request. As a scientist, he wanted his cryopreserved brain to be studied. Hundreds of people have opted to have their brains—with or without the rest of their bodies—stored at cryonic facilities (the remains of 259 individuals are currently stored as either whole bodies or heads at Alcor). But scientists know very little about what has happened to those brains, and there’s no evidence to suggest they could be revived. Coles had met Fahy through their shared interest in longevity, and he asked him to investigate.

“He thought that if he had himself cryopreserved, we could learn from his brain whether cracking was going to happen or not,” says Fahy. That’s what typically happens when organs are put into liquid nitrogen at −196 °C, he says. The extreme cooling creates “tension in the system,” he says. “If you tap it, it’ll just shatter.” This cracking is less likely at the slightly warmer temperatures used for preservation. 

Fahy was involved from the time the samples were taken.

“We had Greg Fahy on the phone coordinating the whole thing, [including] where the biopsies were taken,” says Nick Llewellyn, who oversees research at Alcor. (Llewellyn was not at Alcor at the time but has discussed the procedure with his colleagues.) The biopsied samples were stored in liquid nitrogen and earmarked for Fahy. The rest of the brain was cooled and kept in a temperature-controlled storage container at Alcor.

Bouncing back

It wasn’t until years later that Fahy got around to studying those biopsies. He was interested in how the cryoprotectant—which is toxic—might have affected the brain cells. Previous research has shown that flooding tissues with cryoprotectant can distort the structure of cells, essentially squashing them.

It’s one of the many challenges facing cryobiologists interested in storing human tissues at very low temperatures. While the vitrification of eggs and embryos—which cools them to −196 °C and essentially turns them to glass—has become relatively routine (thanks in part to Fahy’s own work on mouse embryos back in the 1980s), preserving whole organs this way is much harder. It is difficult to cool bigger objects in a uniform way, and they are prone to damaging ice crystal formation, even when cryoprotectants are used, as well as cracking.

Fahy found that when he rewarmed and rehydrated Coles’s brain cells, their structure seemed to bounce back to some degree. Fahy demonstrated the effect over a Zoom call: “It looks like this,” he said with his hands as if in prayer, “and it goes back to this,” he added, connecting his forefingers and thumbs to create a triangle shape.

The structure of the tissue looks pretty intact, too, to him at least, though he admits a purist expecting a pristine structure would be disappointed. He and his colleagues have been able to see remarkable details in the cells and their component parts. “There’s nothing we don’t see,” says Fahy, who has shared his results, which have not yet been peer reviewed, at the preprint server bioRxiv. “It seems that [by taking the cryogenic approach] you can preserve everything.”

As for the cracking, “from what I was told, no cracks were observed [by the team that initially preserved the brain],” says Fahy. The team at Alcor took photographs of the brain when they took the biopsies, but the images were later lost due to a server malfunction, he says. In the more recent photos, the brain is covered in a layer of frost, which makes it impossible to see if there are any cracks, he adds. Attempts to remove the frost might damage the brain, so the team has decided to leave it alone, he says.

Back to life?

Fahy and his colleagues used chemicals to “fix” Coles’s brain samples once they had been rewarmed. That process is typically used to stop fresh tissue samples from decaying, but it also effectively kills them.

But he thinks his results suggest that it might be possible to cryopreserve small pieces of brain tissue and reanimate them to learn more about how they work. Functional recovery seems to be possible in mice—a few weeks ago a team in Germany showed that they were able to revive brain slices that had been stored at −196 °C. Those brain samples showed electrical activity after being cooled and rewarmed.

If cryobiologists can achieve the same feat with human brain samples, those samples could provide neuroscientists with new insights into how living brains work.

Brain cryopreservation “can capture a little bit more of the complexities of the brain,” says Shannon Tessier, a cryobiologist at Massachusetts General Hospital who is developing technologies to preserve hearts, livers, and kidneys for transplantation. “[Being] able to use human brains from deceased individuals [could] add another layer to the research tool kit,” she says.

And Fahy’s paper shows “what happens when we try and vitrify a one-liter, dense, massive goop,” says Matthew Powell-Palm, a cryobiologist at Texas A&M University. “We now have a strong indication that quite large [tissues and organs] can be vitrified by perfusion [without forming too much ice],” he says.

All of the scientists I spoke to, including Fahy, are also working on ways to cool and preserve organs for transplantation. These are in short supply partly because once an organ is removed from a donor, it usually must be transplanted into its recipient within a matter of hours. 

Cryopreservation could buy enough time to make use of more organs, find better organ-donor matches, and potentially even prepare recipients’ immune systems and save them from a lifetime of immunosuppressant drugs, says Bischof, who has also been developing new technologies for organ cryopreservation.

Bischof, Fahy, and others have made huge strides in their attempts so far, and they have managed to remove, cryopreserve, and transplant organs in rabbits and rats, for example. “We’re at the cusp of human-scale organ cryopreservation,” says Bischof.

But when it comes to preserving brains, donation isn’t the aim. Coles had hoped to be reanimated—a far more ambitious goal that hinges on the ability to restore brain function.

Brain reanimation

Fahy acknowledges that while the structure of Coles’s brain samples did bounce back, there is no evidence to suggest the cells could be brought back to life and regain electrical activity and a functioning metabolism. “Restoring it to function … that’s a whole other story,” he says.

But he thinks that successful cryopreservation of the brain “is the gateway to human suspended animation, which [could allow] us to get to the stars someday.” Figuring out human preservation would also allow people to avoid death through what he calls “medical time travel”—journeying to an unspecified time in the future when science will have found a cure for whatever was due to kill that person. “That would be an ultimate goal to pursue,” he says.

“I put the chances [of brain reanimation] at pretty low,” says Alcor’s own Llewellyn. “The kind of technology we need is practically unfathomable.”

The brains already in storage at Alcor and other facilities have been preserved in ways that “have not been validated to work for reanimation,” says Tessier. An expectation that they’ll one day be brought back to life in some form is “quite a jump of faith and hope that’s not based on science,” she says.

As Powell-Palm puts it: “There are so many ways in which those neurons could be toast.”

Mind-altering substances are (still) falling short in clinical trials

This week I want to look at where we are with psychedelics, the mind-altering substances that have somehow made the leap from counterculture to major focus of clinical research. Compounds like psilocybin—which is found in magic mushrooms—are being explored for all sorts of health applications, including treatments for depression, PTSD, addiction, and even obesity.

Over the last decade, we’ve seen scientific interest in these drugs explode. But most clinical trials of psychedelics have been small and plagued by challenges. And a lot of the trial results have been underwhelming or inconclusive.

Two studies out earlier this week demonstrate just how difficult it is to study these drugs. And to my mind, they also show just how overhyped these substances have become.

To some in the field, the hype is not necessarily a bad thing. Let me explain.

The two new studies both focus on the effectiveness of psilocybin in treating depression. And they both attempt to account for one of the biggest challenges in trialing psychedelics: what scientists call “blinding.”

The best way to test the effectiveness of a new drug is to perform a randomized controlled trial. In these studies, some volunteers receive the drug while others get a placebo. For a fair comparison, the volunteers shouldn’t know whether they’re getting the drug or placebo.

That is almost impossible to do with psychedelics. Almost anyone can tell whether they’ve taken a dose of psilocybin or a dummy pill. The hallucinations are a dead giveaway. Still, the authors behind the two new studies have tried to overcome this challenge.

In one, a team based in Germany gave 144 volunteers with treatment-resistant depression either a high or low dose of psilocybin or an “active” placebo, which has its own physical (but not hallucinatory) effects, along with psychotherapy. In their trial, neither the volunteers nor the investigators knew who was getting the drug.

The volunteers who got psilocybin did show some improvement—but it was not significantly any better than the improvement experienced by those who took the placebo. And while those who took psilocybin did have a bigger reduction in their symptoms six weeks later, “the divergence between [the two results] renders the findings inconclusive,” the authors write.

Not great news so far.

The authors of the second study took a different approach. Balázs Szigeti at UCSF and his colleagues instead looked at what are known as “open label” studies of both psychedelics and traditional antidepressants. In those studies, the volunteers knew when they were getting a psychedelic—but they also knew when they were getting an antidepressant.

The team assessed 24 such trials to find that … psychedelics were no more effective than traditional antidepressants. Sad trombone.

“When I set up the study, I wanted to be a really cool psychedelic scientist to show that even if you consider this blinding problem, psychedelics are so much better than traditional antidepressants,” says Szigeti. “But unfortunately, the data came out the other way around.”

His study highlights another problem, too.

In trials of traditional antidepressant drugs, the placebo effect is pretty strong. Depressive symptoms are often measured using a scale, and in trials, antidepressant drugs typically lower symptoms by around 10 points on that scale. Placebos can lower symptoms by around eight points.

When a drug regulator looks at those results, the takeaway is that the antidepressant drug lowers symptoms by an additional two points on the scale, relative to a placebo.

But with psychedelics, the difference between active drug and placebo is much greater. That’s partly because people who get the psychedelic drug know they’re getting it and are expecting the drug to improve their symptoms, says David Owens, emeritus professor of clinical psychiatry at the University of Edinburgh, UK.

But it’s also partly because of the effect on those who know they’re not getting it. It’s pretty obvious when you’re getting a placebo, says Szigeti, and it can be disappointing. Scientists have long recognized the “nocebo” effect as placebo’s “evil twin”—essentially, when you expect to feel worse, you will.

The disappointment of getting a placebo is slightly different, and Szigeti calls it the “knowcebo effect.” “It’s kind of like a negative psychedelic effect, because you have figured out that you’re taking the placebo,” he says.

This phenomenon can distort the results of psychedelic drug trials. While a placebo in a traditional antidepressant drug trial improves symptoms by eight points, placebos in psychedelic trials improve symptoms by a mere four points, says Szigeti.

If the active drug similarly improves symptoms by around 10 points, that makes it look as though the psychedelic is improving symptoms by around six points compared with a placebo. It “gives the illusion” of a huge effect, says Szigeti.

So why have those smaller trials of the past received so much attention? Many have been published in high-end journals, accompanied by breathless press releases and media coverage. Even the inconclusive ones. I’ve often thought that those studies might not have seen the light of day if they’d been investigating any other drug.

“Yeah, nobody would care,” Szigeti agrees.

It’s partly because people who work in mental health are so desperate for new treatments, says Owens. There has been little innovation in the last 40 years or so, since the advent of selective serotonin reuptake inhibitors. “Psychiatry is hemmed in with old theories … and we don’t need another SSRI for depression,” he says. But it’s also because psychedelics are inherently fascinating, says Szigeti. “Psychedelics are cool,” he says. “Culturally, they are exciting.”

I’ve often worried that psychedelics are overhyped—that people might get the mistaken impression they are cure-alls for mental-health disorders. I’ve worried that vulnerable people might be harmed by self-experimentation.

Szigeti takes a different view. Given how effective we know the placebo effect can be, maybe hype isn’t a totally bad thing, he says. “The placebo response is the expectation of a benefit,” he says. “The better response patients are expecting, the better they’re going to get.” Tempering the hype might end up making those drugs less effective, he says.

“At the end of the day, the goal of medicine is to help patients,” he says. “I think most [mental health] patients don’t care whether they feel better because of some expectancy and placebo effects or because of an active drug effect.”

Either way, we need to know exactly what these drugs are doing. Maybe they will be able to help some people with depression. Maybe they won’t. Research that acknowledges the pitfalls associated with psychedelic drug trials is essential.

“These are potentially exciting times,” says Owens. “But it’s really important we do this [research] well. And that means with eyes wide open.”

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.

Peptides are everywhere. Here’s what you need to know.

MIT Technology Review Explains: Let our writers untangle the complex, messy world of technology to help you understand what’s coming next. You can read more from the series here.

Want to lose weight? Get shredded? Stay mentally sharp? A wellness influencer might tell you to take peptides, the latest cure-all in the alternative medicine arsenal. People inject them. They snort them. They combine them into concoctions with superhero names, like the Wolverine stack.  

Matt Kaeberlein, a longevity researcher, first started hearing about peptides a few years ago. “At that point it was mostly functional medicine doctors that were using peptides,” he says, referring to physicians who embrace alternative medicine and supplements. “In the last six months, it’s kind of gone crazy.”

Peptides have gone mainstream. At the health-technology startup Superpower in Los Angeles, employees can get free peptide shots on Fridays. At a health food store in Phoenix, a sidewalk sign reads, “We have peptides!” At a tae kwon do center in South Carolina, a peptide wholesaler hosts an informational evening. On social media, they’re everywhere. And that popularity seems poised to grow; Department of Health and Human Services secretary Robert F. Kennedy Jr. has promised to end the FDA’s “aggressive suppression” of peptides.

The benefits and risks of many of these compounds, however, are largely unknown. Some of the most popular peptides have never been tested in human trials. They are sold for research purposes, not human consumption. Some are illegal knockoffs of wildly successful weight-loss medicines. The vast majority come from China, a fact that has some legislators worried. Last week, Senator Tom Cotton urged the head of the FDA to crack down on illegal shipments of peptides from China. In the absence of regulatory oversight, some people are sending the compounds they purchase off for independent testing just to ensure that the product is legit. 

What is a peptide?

A peptide is simply a short string of amino acids, the building blocks of proteins. “Scientists generally think of peptides as very small protein fragments, but we don’t really have a precise cutoff between a peptide and a protein,” says Paul Knoepfler, a stem-cell researcher at the University of California, Davis. Insulin is a peptide, as is human growth hormone. So are some neurotransmitters, like oxytocin. 

But when wellness influencers talk about peptides, they’re often referring to particular compounds—formulated as injections, pills, or nasal sprays—that have become trendy lately. 

Some of these peptides are FDA-approved prescription medications. GLP-1 medicines, for example, are approved to treat diabetes and obesity but are also easily accessible online to almost anyone who wants to use them. Many sites sell microdoses of GLP-1s with claims that they can “support longevity,” reduce cognitive decline, or curb inflammation. 

Many more peptides are experimental. “The majority fall into the unapproved bucket,” says Kaeberlein, who is chief executive officer of Optispan, a Seattle-based health-care technology company focused on longevity. That bucket includes drugs that promote the release of growth hormones, like TB-500, CJC-1295, and ipamorelin, and compounds said to promote tissue repair and wound healing, like BPC-157 and GHK-Cu. It’s primarily these unapproved compounds that have raised concerns. “Anybody can set up an online shop selling research-grade peptides,” says Tenille Davis, a pharmacist and chief advocacy officer at the Alliance for Pharmacy Compounding, a trade organization representing more than 600 pharmacies. “And nobody knows what’s even in the vials.”  

It’s not just fitness gurus, biohackers, and longevity fanatics who are taking these experimental drugs. Kaeberlein recalls hearing about an acquaintance whose doctor prescribed her unapproved peptides. She was “just a typical upper-middle-class woman,” he says. “That’s when it really hit me that this has sort of gone relatively mainstream.”

What do peptides do?

All kinds of things, purportedly. GHK-Cu is supposed to help with wound healing and collagen production. BPC-157 is said to promote tissue repair and curb inflammation, TB-500 to foster blood vessel formation. Here’s the caveat: The evidence for these benefits comes largely from animal studies and online testimonials, not human trials. “There’s no human clinical evidence to show that they even do what people are claiming that they do,” says Stuart Phillips, a muscle physiologist at McMaster University in Hamilton, Ontario. “So it could be just a giant rip-off.”

Some experimental peptides probably do have beneficial wound healing properties or regenerative effects, Kaeberlein says. For BPC-157, for example, “the animal data is compelling,” he says. But there are still plenty of unknowns: What is the right dosage? How long should you take it? What’s the best way to administer it? Those are questions that can be answered only through rigorous clinical trials. In the absence of those studies, doctors “just make up their own protocols,” he says. Some consumers go the DIY route, reconstituting powdered peptides and injecting their own concoctions at home. 

So why am I seeing ads for these peptide therapies if they’re not approved? 

Federal law prohibits companies from marketing medications that haven’t been approved. That includes most peptides, which are regulated as small molecules, not dietary supplements. (Two notable exceptions are collagen peptides and creatine peptides, often sold as powders.) The law is designed to protect consumers from drugs that haven’t been proved safe and effective.

But it doesn’t stop labs from making peptides for research purposes. “Most of the peptides being consumed in the marketplace now are being sold by these online companies that are selling them labeled for research use only,” Davis says. The vials often bear disclaimers that clearly say as much: “For research use only” or “Not for human consumption.” It’s illegal to market these products for human use, but “the websites make it pretty clear that the buyers are intended to be using these products themselves,” she says.

The practice isn’t legal, but enforcement has been sporadic. “FDA sends warning letters, shuts down companies. But because it’s all online, they have a really hard time keeping up with these entities,” Davis says. And companies have plenty of incentive to keep illegally marketing the products. “They can make millions of dollars without having to spend money and time doing research,” Knoepfler says. “It’s a cash grab.”

Compounding pharmacies, which are legally allowed to create bespoke medications by mixing bulk active ingredients, often get requests to dispense peptides, but most peptides don’t meet the eligibility criteria for compounding. This has always been the case, but in 2023 the FDA explicitly added several common experimental peptides to the list of bulk substances that cannot be compounded because of safety concerns. “It put an exclamation point on policy that was already in place,” Davis says.  

Many GLP-1 medications are available from compounding pharmacies. That used to be accepted because the drugs were in short supply. Now, however, supplies of most of these medications are stable, and sellers are under increasing pressure from regulators to stop mass-marketing these drugs. 

What’s the harm in trying them? 

Peptides sold for research purposes come from labs with little regulatory oversight. “When you buy stuff online intended for research grade, you have no idea what’s in the vial that you’re getting. You have no idea the sterility practices that it was manufactured under, or what sort of impurities might be in the vial,” Davis says.

Phillips has heard some people say they send their peptides for third-party testing to ensure that they’re pure, “like it’s some kind of flex,” he says. “And I’m like, ‘Well, you just proved that this stuff lives in the shadows, for crying out loud.’”

Finnrick Analytics, a peptide-testing startup in Austin, Texas, has analyzed the purity and potency of more than 5,000 samples of 15 different peptides from 173 vendors. The results show that the quality varies substantially from vendor to vendor and even batch to batch. For example, the company tested nearly 450 samples of BPC-157 from 64 vendors. In some cases, the vials sold as BPC-157 didn’t contain the compound at all. In those that did, the purity varied from about 82% to 100%. 

Perhaps more worrying, 8% of all the peptide samples Finnrick tested had measurable levels of endotoxins, bacterial fragments that can cause fever and chills or, in larger doses, septic shock. 

The health risks aren’t just hypothetical. In 2025, two women had to be hospitalized and placed on ventilators after receiving peptide injections at a longevity conference in Las Vegas. Both recovered, and it’s still not clear whether they reacted to the peptides themselves or to some impurity in the vials. 

“The idea that all peptides are safe and all peptides are natural is just nonsense,” Kaeberlein says. “I tend to consider myself fairly libertarian when it comes to what people want to do for their health,” he adds. “If you want to take an experimental drug, that’s up to you.” But the problem with unregulated experimental therapies is that it’s exceedingly difficult to assess benefit and harm. “The relatively small percentage of people that are bad actors will be bad actors, and they will dishonestly market this stuff to people who aren’t equipped to really understand the true risks and rewards,” he says.

And, like any drug, peptides come with a risk of side effects. For approved medications, these are detailed right on the package insert. But for many experimental peptides, there hasn’t been enough research to understand what those side effects might be. Some researchers have warned that peptides that promote growth or blood vessel formation might also foster the growth of cancers.  

For competitive athletes who use peptides, meanwhile, the risks include not just possible health problems but suspension. Some peptides, like BPC-157, are banned by the World Anti-Doping Agency. 

The FDA has undergone a pretty substantial overhaul under the Trump administration. Are the regulations around peptides likely to change? 

I don’t have a crystal ball, but it seems likely. In May 2025, US health secretary Robert F. Kennedy Jr. joined the longevity enthusiast and biohacker Gary Brecka on his podcast The Ultimate Human and promised to “end the war at FDA against alternative medicine—the war on stem cells, the war on chelating drugs, the war on peptides.”

Knoepfler anticipates that Kennedy will force the FDA to allow compounding of some of the most popular peptides, like BPC-157 and GHK-Cu. “Such a step would put public health at great risk, while giving compounders and likely wellness influencers a lot more profit,” he says. 

The FDA seems intent on cracking down on GLP-1 copycats, however. In early February, commissioner Marty Makary posted on X that the agency would take “swift action against companies mass-marketing illegal copycat drugs, claiming they are similar to FDA-approved products.”

Measles cases are rising. Other vaccine-preventable infections could be next.

There’s a measles outbreak happening close to where I live. Since the start of this year, 34 cases have been confirmed in Enfield, a northern borough of London. Most of those affected are children under the age of 11. One in five have needed hospital treatment.

It’s another worrying development for an incredibly contagious and potentially fatal disease. Since October last year, 962 cases of measles have been confirmed in South Carolina. Large outbreaks (with more than 50 confirmed cases) are underway in four US states. Smaller outbreaks are being reported in another 12 states.

The vast majority of these cases have been children who were not fully vaccinated. Vaccine hesitancy is thought to be a significant reason children are missing out on important vaccines—the World Health Organization described it as one of the 10 leading threats to global health in 2019. And if we’re seeing more measles cases now, we might expect to soon see more cases of other vaccine-preventable infections, including some that can cause liver cancer or meningitis.

Some people will always argue that measles is not a big deal—that infections used to be common, and most people survived them and did just fine. It is true that in most cases kids do recover well from the virus. But not always.

Measles symptoms tend to start with a fever and a runny nose. The telltale rash comes later. In some cases, severe complications develop. They can include pneumonia, blindness, and inflammation of the brain. Some people won’t develop complications until years later. In rare cases, the disease can be fatal.

Before the measles vaccine was introduced, in 1963, measles epidemics occurred every two to three years, according to the WHO. Back then, around 2.6 million people died from measles every year. Since it was introduced, the measles vaccine is thought to have prevented almost 59 million deaths.

But vaccination rates have been lagging, says Anne Zink, an emergency medicine physician and clinical fellow at the Yale School of Public Health. “We’ve seen a slow decline in people who are willing to get vaccinated against measles for some time,” she says. “As we get more and more people who are at risk because they’re unvaccinated, the higher the chances that the disease can then spread and take off.”

Vaccination rates need to be at 95% to prevent measles outbreaks. But rates are well below that level in some regions. Across South Carolina, the proportion of kindergartners who received both doses of the MMR vaccine, which protects against measles as well as mumps and rubella, has dropped steadily over the last five years, from 94% in 2020-2021 to 91% in 2024-2025. Some schools in the state have coverage rates as low as 20%, state epidemiologist Linda Bell told reporters last month.

Vaccination rates are low in London, too. Fewer than 70% of children have received both doses of their MMR by the time they turn five, according to the UK Health Security Agency. In some boroughs, vaccination rates are as low as 58%. So perhaps it’s not surprising we’re seeing outbreaks.

The UK is one of six countries to have lost their measles elimination status last month, along with Spain, Austria, Armenia, Azerbaijan, and Uzbekistan. Canada lost its elimination status last year.

The highly contagious measles could be a bellwether for other vaccine-preventable diseases. Zink is already seeing signs. She points to a case of polio that paralyzed a man in New York in 2022. That happened when rates of polio vaccination were low, she says. “Polio is a great example of … a disease that is primarily asymptomatic, and most people don’t have any symptoms whatsoever, but for the people who do get symptoms, it can be life-threatening.”

Then there’s mumps—another disease the MMR vaccine protects against. It’s another one of those infections that can be symptom-free and harmless in some, especially children, but nasty for others. It can cause a painful swelling of the testes, and other complications include brain swelling and deafness. (From my personal experience of being hospitalized with mumps, I can attest that even “mild” infections are pretty horrible.)

Mumps is less contagious than measles, so we might expect a delay between an uptick in measles cases and the spread of mumps, says Zink. But she says that she’s more concerned about hepatitis B.

“It lives on surfaces for a long period of time, and if you’re not vaccinated against it and you’re exposed to it as a kid, you’re at a really high risk of developing liver cancer and death,” she says.

Zink was formerly chief medical officer of Alaska, a state that in the 1970s had the world’s highest rate of childhood liver cancer caused by hepatitis B. Screening and universal newborn vaccination programs eliminated the virus’s spread.

Public health experts worry that the current US administration’s position on vaccines may contribute to the decline in vaccine uptake. Last month the US Centers for Disease Control and Prevention approved changes to childhood vaccination recommendations. The agency no longer recommends the hepatitis B vaccine for all newborns. The chair of the CDC’s vaccine advisory panel has also questioned broad vaccine recommendations for polio.

Even vitamin injections are being refused by parents, says Zink. A shot of vitamin K at birth can help prevent severe bleeding in some babies. But recent research suggests that parents of 5% of newborns are refusing it (up from 2.9% in 2017).

“I can’t tell you how many of my pediatric [doctor] friends have told me about having to care for a kiddo in the ICU with … bleeding into their brain because the kid didn’t get vitamin K at birth,” says Zink. “And that can kill kids, [or have] lifelong, devastating, stroke-like symptoms.”

All this paints a pretty bleak picture for children’s health. But things can change. Vaccination can still offer protection to plenty of people at risk of infection. South Carolina’s Department of Public Health is offering free MMR vaccinations to residents at mobile clinics.

“It’s easy to think ‘It’s not going to be me,’” says Zink. “Seeing kiddos who don’t have the agency to make decisions [about vaccination] being so sick from vaccine-preventable diseases, to me, is one of the most challenging things of practicing medicine.”

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.

The scientist using AI to hunt for antibiotics just about everywhere

When he was just a teenager trying to decide what to do with his life, César de la Fuente compiled a list of the world’s biggest problems. He ranked them inversely by how much money governments were spending to solve them. Antimicrobial resistance topped the list. 

Twenty years on, the problem has not gone away. If anything, it’s gotten worse. Infections caused by bacteria, fungi, and viruses that have evolved ways to evade treatments are now associated with more than 4 million deaths per year, and a recent analysis, published in the Lancet, predicts that number could surge past 8 million by 2050. In a July 2025 essay in Physical Review Letters, de la Fuente, now a bioengineer and computational biologist, and synthetic biologist James Collins warned of a looming “post­antibiotic” era in which infections from drug-resistant strains of common bacteria like Escherichia coli or Staphylococcus aureus, which can often still be treated by our current arsenal of medications, become fatal. “The antibiotic discovery pipeline remains perilously thin,” they wrote, “impeded by high development costs, lengthy timelines, and low returns on investment.”

But de la Fuente is using artificial intelligence to bring about a different future. His team at the University of Pennsylvania is training AI tools to search genomes far and deep for peptides with antibiotic properties. His vision is to assemble those peptides—molecules made of up to 50 amino acids linked together—into various configurations, including some never seen in nature. The results, he hopes, could defend the body against microbes that withstand traditional treatments. 

His quest has unearthed promising candidates in unexpected places. In August 2025 his team, which includes 16 scientists in Penn’s Machine Biology Group, described peptides hiding in the genetic code of ancient single-celled organisms called archaea. Before that, they’d excavated a list of candidates from the venom of snakes, wasps, and spiders. And in an ongoing project de la Fuente calls “molecular de-­extinction,” he and his collaborators have been scanning published genetic sequences of extinct species for potentially functional molecules. Those species include hominids like Neanderthals and Denisovans and charismatic megafauna like woolly mammoths, as well as ancient zebras and penguins. In the history of life on Earth, de la Fuente reasons, maybe some organism evolved an antimicrobial defense that could be helpful today. Those long-gone codes have given rise to resurrected compounds with names like ­mammuthusin-2 (from woolly mammoth DNA), mylodonin-2 (from the giant sloth), and hydrodamin-1 (from the ancient sea cow). Over the last few years, this molecular binge has enabled de la Fuente to amass a library of more than a million genetic recipes.

At 40 years old, de la Fuente has also collected a trophy case of awards from the American Society for Microbiology, the American Chemical Society, and other organizations. (In 2019, this magazine named him one of “35 Innovators Under 35” for bringing computational approaches to antibiotic discovery.) He’s widely recognized as a leader in the effort to harness AI for real-world problems. “He’s really helped pioneer that space,” says Collins, who is at MIT. (The two have not collaborated in the laboratory, but Collins has long been at the forefront of using AI for drug discovery, including the search for antibiotics. In 2020, Collins’s team used an AI model to predict a broad-­spectrum antibiotic, halicin, that is now in preclinical development.) 

The world of antibiotic development needs as much creativity and innovation as researchers can muster, says Collins. And de la Fuente’s work on peptides has pushed the field forward: “César is marvelously talented, very innovative.” 

A messy, noisy endeavor

De la Fuente describes antimicrobial resistance as an “almost impossible” problem, but he sees plenty of room for exploration in the word almost. “I like challenges,” he says, “and I think this is the ultimate challenge.” 

The use, overuse, and misuse of antibiotics, he says, drives antimicrobial resistance. And the problem is growing unchecked because conventional ways to find, make, and test the drugs are prohibitively expensive and often lead to dead ends. “A lot of the companies that have attempted to do antibiotic development in the past have ended up folding because there’s no good return on investment at the end of the day,” he says.

Antibiotic discovery has always been a messy, noisy endeavor, driven by serendipity and fraught with uncertainty and misdirection. For decades, researchers have largely relied on brute-force mechanical methods. “Scientists dig into soil, they dig into water,” says de la Fuente. “And then from that complex organic matter they try to extract antimicrobial molecules.” 

But molecules can be extraordinarily complex. Researchers have estimated the number of possible organic combinations that could be synthesized at somewhere around 1060. For reference, Earth contains an estimated 1018 grains of sand. “Drug discovery in any domain is a statistics game,” says Jonathan Stokes, a chemical biologist at McMaster University in Canada, who has been using generative AI to design potential new antibiotics that can be synthesized in a lab, and who worked with Collins on halicin. “You need enough shots on goal to happen to get one.” 

Those have to be good shots, though. And AI seems well suited to improving researchers’ aim. Biology is an information source, de la Fuente explains: “It’s like a bunch of code.” The code of DNA has four letters; proteins and peptides have 20, where each “letter” represents an amino acid. De la Fuente says his work amounts to training AI models to recognize sequences of letters that encode antimicrobial peptides, or AMPs. “If you think about it that way,” he says, “you can devise algorithms to mine the code and identify functional molecules, which can be antimicrobials. Or antimalarials. Or anticancer agents.” 

Practically speaking, we’re still not there: These peptides haven’t yet been transformed into usable drugs that help people, and there are plenty of details—dosage, delivery, specific targets—that need to be sorted out, says de la Fuente. But AMPs are appealing because the body already uses them.They’re a critical part of the immune system and often the first line of defense against pathogenic infections. Unlike conventional antibiotics, which typically have one trick for killing bacteria, AMPs often exhibit a multimodal approach. They may disrupt the cell wall and the genetic material inside as well as a variety of cellular processes. A bacterial pathogen may evolve resistance to a conventional drug’s single mode of action, but maybe not to a multipronged AMP attack.

From discovery to delivery

De la Fuente’s group is one of many pushing the boundaries of using AI for antibiotics. Where he focuses primarily on peptides, Collins works on small-molecule discovery. So does Stokes, at McMaster, whose models identify promising new molecules and predict whether they can be synthesized. “It’s only been a few years since folks have been using AI meaningfully in drug discovery,” says Collins. 

Even in that short time the tools have changed, says James Zou, a computer scientist at Stanford University, who has worked with Stokes and Collins. Researchers have moved from using predictive models to developing generative approaches. With a predictive approach, Zou says, researchers screen large libraries of candidates that are known to be promising. Generative approaches offer something else: the appeal of designing a new molecule from scratch. Last year, for example, de la Fuente’s team used one generative AI model to design a suite of synthetic peptides and another to assess them. The group tested two of the resulting compounds on mice infected with a drug-resistant strain of Acinetobacter baumannii, a germ that the World Health Organization has identified as a “critical priority” in research on antimicrobial resistance. Both successfully and safely treated the infection. 

But the field is still in the discovery phase. In his current work, de la Fuente is trying to get candidates closer to clinical testing. To that end, his team is developing an ambitious multimodal model called ApexOracle that’s designed to analyze a new pathogen, pinpoint its genetic weaknesses, match it to antimicrobial peptides that might work against it, and then predict how an antibiotic, built from those peptides, would fare in lab tests. It “converges understanding in chemistry, genomics, and language,” he says. It’s preliminary, he adds, but even if it doesn’t work perfectly, it will help steer the next generation of AI models toward the ultimate goal of resisting resistance. 

Using AI, he believes, human researchers now have a fighting chance at catching up to the giant threat before them. The technology has already saved decades of human research time. Now he wants it to save lives, too: “This is the world that we live in today, and it’s incredible.” 

Stephen Ornes is a science writer in Nashville, Tennessee.