Until's near-term product is reversible cryopreservation of single human organs; the long-term goal is whole-body reversible cryopreservation for medical hibernation.
Deming frames the near-term work as solving a concrete, near-clinical problem (organ preservation) while treating it as a forcing function and proof point for the company's more speculative long-term goal.
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The core engineering problem is avoiding ice formation entirely, not managing it, because expanding ice physically ruptures cell membranes and tissue.
Water expands when it freezes, and that expansion is what causes irreversible tissue damage. Until's strategy is built around staying below roughly -130C while spending as little time as possible in the temperature band where ice can nucleate.
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Ice nucleation is a stochastic process, so minimizing time in the danger zone can prevent most ice damage even without fully eliminating cryoprotective chemicals.
Ice forms through random nucleation followed by extension rather than uniformly across a material. Because it is probabilistic, faster transit through the risky temperature range lowers the odds of significant ice formation, giving engineering (cooling/rewarming speed) real leverage over a biological outcome.
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Small-scale proof points already show reversible cryopreservation works: 30-year-old frozen embryos have produced viable pregnancies, and a reversibly cryopreserved rat kidney regained normal function after transplant.
Human embryos have been reversibly cryopreserved for over 30 years and later used to create successful pregnancies. Separately, researchers reversibly cryopreserved a rat kidney, rewarmed it, transplanted it into a rat with no other kidney, and saw normal kidney function return within about a month, establishing that whole-organ reversible cryopreservation is not purely hypothetical.
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Co-founder Hunter Davis's key contribution was recognizing that engineering difficulty and biological difficulty can be partially traded off against each other, but not entirely.
Better engineering, such as faster and more even cooling and rewarming, reduces how much cryoprotective agent chemistry is required. But engineering cannot fully substitute for solving the underlying biological questions; some of those could still resolve negatively for parts of the problem.
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Temperature is an unusually powerful conceptual lever for this problem because it links molecular-scale motion to a single measurable physical parameter.
Deming argues that most biology problems lack any comparably clean, physics-grounded parameter for reasoning about nanoscale behavior. Because temperature does this, Until can borrow decades of physics theory to model tissue behavior in ways that are rarely possible for other biological problems.
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Organ transplant logistics today are dangerously improvised: organs expire quickly, so hospitals charter private jets and patients wait on-call within a two-hour radius of a transplant center.
Because there is currently no way to pause an organ's biological clock, matching and transport happen at the last minute, with surgeons flown out overnight and patients tethered to a pager. Deming's goal is to remove time as a variable so decisions can be made deliberately instead of under emergency time pressure.
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Deming treats aging and longevity as a social blind spot problem rather than a purely technical one.
She argues longevity research is undervalued not because it is technically infeasible, but because aging isn't classified as a disease in a way that's socially recognized, which affects funding, career incentives, and what researchers feel is legitimate to work on.
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Deming's original venture thesis, that longevity's binding constraint was capital allocation rather than science, led her to start the Longevity Fund before later shifting to operating a company directly.
As a teenager she observed that longevity researchers' most common complaint was lack of funding, so her first move was to raise money for the field rather than to work on the science herself; that fund preceded her later decision to found Until and work on the problem directly.
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When recruiting for a company chasing an uncertain, long-horizon scientific goal, Deming deliberately anchors on a concrete near-term deliverable rather than overclaiming certainty about the moonshot.
She says claiming whole-body reversible cryopreservation is 100% certain to work would undermine credibility with skeptical scientists and hurt recruiting. Instead, Until uses reversible organ cryopreservation as a falsifiable near-term benchmark that tests whether the company's underlying models of the problem are correct.
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The largest unresolved unknown for whole-body reversible cryopreservation is the brain.
Deming says it is unclear what type or degree of neural injury is survivable or reversible under a whole-body hibernation protocol, even though the brain is known to tolerate various kinds of change and damage from aging; this uncertainty is explicitly on the neuroscience side, not the engineering side.
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Non-medical use cases like 'skipping to the future' or interstellar travel underestimate the social cost of losing one's current relationships and context.
Deming argues most people would resist hibernation not for technical reasons but because it means giving up their current social reality while it evolves without them. That cost is why she thinks the technology only clearly makes sense first for people who would otherwise die, where the alternative is worse.
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Media referenced
Pantheon - show - Sarah references watching the animated series together with Laura as a shared touchpoint for thinking about mind uploading and consciousness, a theme adjacent to Until's work on pausing biological time.
Companies
Until - Laura Deming's biotech startup, co-founded with Hunter Davis, building reversible cryopreservation technology, starting with human organs and aiming eventually at whole-body medical hibernation.
Longevity Fund - The venture fund Laura founded earlier in her career on the thesis that longevity research was underfunded, not undersolvable.
Thiel Fellowship - Laura left conventional schooling (referenced as MIT/TL fellow in the conversation) through the Thiel Fellowship, which shaped her early path into longevity work.
Techniques and frameworks
Reversible cryopreservation - Until's core technical approach: cooling tissue below roughly -130C while avoiding ice nucleation, then rewarming it, so the tissue survives structurally and functionally intact.
Ice nucleation avoidance - Because ice formation is stochastic (random nucleation plus extension), minimizing time spent in the temperature range where ice can nucleate reduces the probability of damaging ice formation without needing to eliminate it outright.
Cryoprotective agent (CPA) minimization - Faster, more even cooling and rewarming (an engineering lever) reduces how much chemical cryoprotectant is needed to prevent ice damage (a biology lever), illustrating the engineering-biology tradeoff at the center of Until's approach.
Summary
Laura Deming, CEO and co-founder of the biotech startup Until, joins Sarah Guo to explain how her company is trying to engineer time itself out of organ transplantation, and eventually out of terminal illness. Until's near-term product is reversible cryopreservation of single human organs: cooling an organ below roughly -130C while avoiding ice formation, then rewarming it undamaged, so transplant logistics stop being an emergency-room sprint. The company's longer-term ambition is whole-body reversible cryopreservation for medical hibernation, essentially buying a dying patient time to reach a cure that arrives too late for them otherwise.
Deming's path here runs through a decade of longevity work: she was a Thiel Fellow, founded the Longevity Fund on the belief that the field's binding constraint was capital rather than science, and only later concluded that aging and cryopreservation share a common problem, a "social blind spot" where the work isn't taken seriously because it isn't classified as addressing a recognized disease. Cryopreservation, she argues, is even more compelling on pure problem-selection grounds: it has clean physics (temperature is an unusually powerful conceptual lever linking molecular motion to a single measurable parameter), real proof points (30-year reversibly cryopreserved embryos producing viable pregnancies, a reversibly cryopreserved rat kidney regaining normal function after transplant), and a co-founder, Hunter Davis, whose first-principles skepticism turned into conviction once he worked through the ice-formation math himself.
Much of the conversation is a plain-language tour of the science: ice damages tissue because water expands as it freezes, but ice nucleation is stochastic, so minimizing time spent in the danger zone can prevent most ice formation without needing to eliminate cryoprotective chemicals entirely. That gives Until real engineering leverage (faster, more even cooling and rewarming) over what would otherwise be a purely biological problem, though Deming is careful to note engineering can't fully substitute for resolving genuine biological uncertainty, particularly around the brain, which remains the single biggest open question for whole-body hibernation.
The two also dig into the human cost of current organ transplant logistics: because organs expire quickly, hospitals charter private jets to retrieve them and patients wait on-call within a two-hour radius of a transplant center, essentially under "surgery center house arrest." Deming's stated goal is to make time not a variable in that process, a phrase she borrows from a transplant surgeon Until works with. Toward the end, they cover why Deming thinks non-medical hibernation use cases (skipping to the future, interstellar travel) carry an underappreciated social cost, since most people are more attached to their current relationships and context than they realize, and how she recruits scientists to a company whose ultimate goal remains genuinely uncertain by anchoring the pitch on a concrete, falsifiable near-term deliverable rather than overselling certainty about the moonshot.
Notable Quotes
"Making time not a variable changes the whole paradigm." - Laura Deming, quoting a transplant surgeon Until works with
"We already reversibly cryopreserved tissue, including human tissue, all the time, and we do it for very long time periods. There are kids who were literally cryopreserved for 30 years as tiny embryos." - Laura Deming
"I think longevity and aging kind of occupy this weird realm where, because they're not explicitly diseases in a way that's fully socially recognized yet, they're not seen as valid to work on." - Laura Deming
"It's crazy because they're one of the most precious resources we know of, and yet people regularly charter private jets... it's incredible that everyone is operating this way right now." - Laura Deming, on current organ transport logistics