A Billionaire-Backed Startup Wants to Grow 'Organ Sacks' to Replace Animal Testing | WIREDSkip to main contentMenuSECURITYPOLITICSTHE BIG STORYBUSINESSSCIENCECULTUREREVIEWSMenuAccountAccountNewslettersSecurityPoliticsThe Big StoryBusinessScienceCultureReviewsChevronMoreExpandThe Big InterviewMagazineEventsWIRED InsiderWIRED ConsultingNewslettersPodcastsVideoLivestreamsMerchSearchSearchEmily MullinScienceMar 23, 2026 3:46 PMA Billionaire-Backed Startup Wants to Grow 'Organ Sacks' to Replace Animal TestingR3 Bio has a bold idea for replacing lab animals: genetically-engineered whole organ systems that lack a brain. The long-term goal, says a cofounder, is to make human versions.Photo-Illustration: WIRED Staff; Getty ImagesCommentLoaderSave StorySave this storyCommentLoaderSave StorySave this storyAs the Trump administration phases out the use of animal experimentation across the federal government, a biotech startup has a bold idea for an alternative to animal testing: nonsentient “organ sacks.”Bay Area-based R3 Bio has been quietly pitching the idea to investors and in industry publications as a way to replace lab animals without the ethical issues that come with living organisms. That’s because these structures would contain all of the typical organs—except a brain, rendering them unable to think or feel pain. The company’s long-term goal, cofounder Alice Gilman says, is to make human versions that could be used as a source of tissues and organs for people who need them.For Immortal Dragons, a Singapore-based longevity fund that’s invested in R3, the idea of replacement is a core strategy for human longevity. “We think replacement is probably better than repair when it comes to treating diseases or regulating the aging process in the human body,” says CEO Boyang Wang. “If we can create a nonsentient, headless bodyoid for a human being, that will be a great source of organs.”For now, R3 is aiming to make monkey organ sacks. “The benefit of using models that are more ethical and are exclusively organ systems would be that testing can be meaningfully more scalable,” Gilman says. (R3’s name comes from the philosophy in animal research known as the three R’s—replacement, reduction, and refinement—developed by British scientists William Russell and Rex Burch in 1959 to promote humane experimentation.)New drugs are often tested in monkeys before they’re given to human participants in clinical trials. For instance, monkeys were critical during the Covid-19 pandemic for testing vaccines and therapeutics. But they’re also an expensive resource, and their numbers are dwindling in the US after China banned the export of nonhuman primates in 2020.Animal rights activists have long pushed to end research on monkeys, and one of the seven federally funded primate research facilities across the country has signaled it would consider shutting down and transitioning into a sanctuary amid growing pressure. The US Centers for Disease Control and Prevention is also winding down monkey research, part of a bigger trend across the government to reduce reliance on animal testing.As a result, Gilman says, there aren’t enough research monkeys left in the US to allow for necessary research if another pandemic threat emerges. Enter organ sacks.Organ sacks would in theory offer advantages over existing organs-on-chips or tissue models, which lack the full complexity of whole organs, including blood vessels.Gilman says it’s already possible to create mouse organ sacks that lack a brain, though she and cofounder John Schloendorn deny that R3 has made them. (For the record, Gilman doesn’t like the term “brainless” to describe the organ sacks. “It's not missing anything, because we design it to only have the things we want,” she says.) Gilman and Schloendorn would not say how exactly they plan to create the monkey and human organ sacks, but said they are exploring a combination of stem-cell technology and gene editing.It’s plausible that organ sacks could be grown from induced pluripotent stem cells, says Paul Knoepfler, a stem cell biologist at the University of California, Davis. These stem cells come from adult skin cells and are reprogrammed to an embryonic-like state. They have the potential to form into any cell or tissue in the body and have been used to create embryo-like structures that resemble the real thing. By editing these stem cells, scientists could disable genes needed for brain development. The resulting embryo could then be incubated until it grows into organized organ structures.Gilman envisions monkey organ sacks initially being used for drug toxicity testing. Eliminating pain and suffering that research animals experience is a major motivation for the startup.The US Animal Welfare Act requires minimizing pain and distress for research animals, but it’s not always possible. In fiscal year 2024, US research facilities reported using more than 60,000 nonhuman primates for testing and experimentation, according to the Animal and Plant Health Inspection Service, part of the Department of Agriculture. More than 33,000 of those animals were not subjected to pain, while nearly 26,000 experienced minimal pain. For about 1,200 of those animals, pain was not minimized due to the nature of the experiments. The federal government does not keep statistics on how many nonhuman primates are euthanized every year as a result of research.R3’s ambitions go beyond replacing animal testing, though. The company is eyeing replacement of human parts, an emerging idea in the longevity field. The startup aims to create nonsentient human organ sacks that could provide blood, tissue, and organs to people when their own bodies fail them.“We have things that no one has invented before to create designer organs,” says Gilman, who was inspired in part by her father’s experience undergoing a heart transplant. Around the world, demand for donor organs outstrips supply. In the US alone, more than 100,000 people are awaiting an organ transplant and 13 people die each day waiting for one.Gilman points to the well-documented illegal organ-harvesting trade in Asia and Africa as a reason for why ethically sourced body parts are desperately needed. In the US, an investigation last year by the Department of Health and Human Services alleged instances where hospitals authorized the organ procurement process to begin when some patients may still have shown neurological signs compatible with life.Genetically engineered pig organs are being explored as one way to help alleviate the organ shortage. But so far, the longest someone has lived with a pig organ is just under nine months.Growing human organs from scratch has been a longtime goal of regenerative medicine, but the idea of body sacks raises a number of ethical questions about how these entities would be created, stored, and maintained—and if they would be capable of having awareness or feeling pain.“If you make a living entity without a brain at all, I think we’d be pretty comfortable with thinking it can’t feel pain,” says Hank Greely, a bioethicist at Stanford University, who has written about the potential for human “bodyoids” that lack sentience. “It’s highly possible that none of this will ever work, but it's also possible that it could.”Greely thinks it will be important to get buy-in from the public, since the concept is so unsettling. “I think the ‘yuck factor’ will be strong,” he says, “but that depends in part on what any resulting things look like and how they behave.”All of this is still highly theoretical. R3 says it is currently only working in monkey cells, although a job ad posted by Gilman shows that the company is seeking a veterinarian in Puerto Rico to “implant embryos, monitor pregnancies and help deliver healthy births” in nonhuman primates. In addition to Immortal Dragons, the company is backed by billionaire Tim Draper and LongGame Ventures in the UK, according to R3.“We are all better off than we were 150 years ago,” Draper told WIRED via email, “and because of forward-thinking entrepreneurs, we will be a lot better off 150 years from now.”CommentsBack to topTriangleYou Might Also LikeIn your inbox: Upgrade your life with WIRED-tested gearNvidia plans to launch an open-source AI agent platformBig Story: He built the Epstein database—it consumed his lifeShould you leave your phone charging overnight?Watch: How right wing influencers infiltrated the governmentEmily Mullin is a staff writer at WIRED, covering biotechnology. 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R3 Bio is pursuing a radical approach to animal testing, proposing the creation of “organ sacks”—genetically engineered, brainless animal-like structures designed to mimic human organs. Co-founder Alice Gilman envisions these sacks as a significant advancement over existing models like organ-on-a-chip, offering greater scalability and ethical advantages, particularly in drug toxicity testing. The company’s long-term goal is to develop human versions for potential tissue and organ replacement, aligning with the broader longevity research field where “replacement is probably better than repair.” Immortal Dragons, the investment firm backing R3, sees these bodyoids as a crucial component of its strategy for treating diseases and regulating the aging process.

The startup’s immediate focus is on creating monkey organ sacks, driven by the comparative ethical concerns and scalability benefits. R3’s approach centers on combining stem-cell technology and gene editing, potentially starting with mouse organ sacks lacking a brain – though Gilman and co-founder John Schloendorn deny having fully realized this. Paul Knoepfler, a stem cell biologist at UC Davis, suggests that induced pluripotent stem cells, reprogrammed from adult skin cells, offer a viable pathway for creating these structures, effectively disabling genes responsible for brain development. Gilman’s inspiration, stemming from her father’s heart transplant, underscores the significant demand for donor organs—over 100,000 individuals await transplants in the US alone, with 13 deaths occurring daily due to organ scarcity. The company's ambition extends to creating replacement human organs, recognizing the ethical and logistical issues surrounding organ sourcing, including illegal organ harvesting.

Despite the theoretical potential, considerable challenges and ethical considerations surround R3’s endeavor. The “yuck factor” associated with creating artificial entities, even without a brain, is anticipated, and the company’s current efforts are limited to working with monkey cells. The prospect of creating potentially sentient or feeling bodyoids raises serious bioethical questions about their creation, maintenance, and potential for awareness or pain. Hank Greely, a bioethicist at Stanford University, highlights the importance of public buy-in, acknowledging the significant hurdles and the potentially unsettling nature of the concept. The company has secured funding from billionaire Tim Draper and LongGame Ventures, demonstrating confidence in its innovative approach, and is currently seeking a veterinarian in Puerto Rico to assist with embryo implantation and monitoring.