Sad sack or serious salvation?
A small group of scientists is angling to replace laboratory animals with living “organ sacks” grown from human cells.
R3 Bio, a billionaire-backed biotech startup, is committed to designing “complete organ systems” to be used in the research and development of drugs and potentially, as a source of tissues and organs for humans.
Based in San Francisco, R3 aims to eliminate animal suffering by replacing the use of lab animals with these systems.
The company takes its name from the animal testing philosophy of the three R’s—replacement, reduction, and refinement—developed in the 1950’s to promote humane experimentation.
The organ systems that R3 Bio proposes to engineer would contain all organs except the brain, making these sacks incapable of consciousness, sentience, or pain processing.
Ostensibly leaving the brain off the table, or out of the sack as it were, would remove the ethical issues that arise from extracting from living organisms.
Despite the obvious absence, R3 CEO co-founder Alice Gilman prefers not to refer to said sacks as “brainsless.”
“It’s not missing anything, because we design it to only have the things we want,” she told Wired.
These brain-free organ sacks have caught the attention and secured the financing of investors who see them as integral to the future of longevity medicine.
“We think replacement is probably better than repair when it comes to treating diseases or regulating the aging process in the human body,” said CEO Boyang Wang of Singapore-based investment fund Immortal Dragons, one of R3 Bio’s chief backers.
“If we can create a non-sentient, headless bodyoid for a human being, that will be a great source of organs.”
While Gilman shared that R3 now has the technology to create mouse organ sacks, she said they have yet to implement the science.
However, once vermin organ sacks are made, the company hopes to expand into monkey organ sacks and, ultimately, bodyoids made from human cells.
“The benefit of using models that are more ethical and are exclusively organ systems would be that testing can be meaningfully more scalable,” said Gilman.
Gilman shared that ideally, the monkey organ sacs could be used to test for drug toxicity, specifically in vaccine trials, a substitution that could spare a legion of monkeys from lives of captivity and laboratory experimentation.
According to the Animal and Plant Health Inspection Service, part of the Department of Agriculture, 60,000 nonhuman primates were used in experiments at various research facilities in 2024.
While more than half were not subjected to pain, 26,000 experienced minimal pain, and 1,200 endured extreme pain or denied pain relief as part of the protocol of the experimentation.
Gilman maintains that, in addition to sparing our primate brethren pain, bodyoids would allow researchers to see how drugs affect the human body en masse and at once, a clear advantage over current organs-on-chips or tissue models.
“The human body is not a collection of parts; it’s a system. We can’t keep studying diseases in pieces and hoping the results will scale,” she wrote in a blog post.
‘Whether we’re testing new drugs, mapping rare disorders, or training AI models, the biology we use needs to reflect the biology we live with.”
Gilman believes that to move beyond animal testing and toward system-level modelling, such technology should be part of the national infrastructure.
“That means funding it like a public good, validating it like a regulatory standard, and building it with the urgency of a moonshot.”
Gilman emphasized that while monkey and human organ sacks have yet to be developed, they would, in theory, be created using stem cell and gene-editing technology.
Ideally, these organs could also be used as viable transplants for the millions awaiting a life-saving transplant.
