Who is closest to reversing aging?

Which startups are really trying to reverse aging?

The serious startup race to reverse aging comes down to eight private biotechs, and only three have placed an aging-biology drug into human trials.

We include companies trying to reset cellular age, restore youthful cell function, replace aged cell populations or remove a well-defined driver of aging. That gives us Life Biosciences, NewLimit, Altos Labs, Retro Biosciences, Rubedo Life Sciences, Turn Biotechnologies, Rejuvenate Bio and Shift Bioscience.

We leave out supplement brands, longevity clinics, biological-age testing companies and general preventive-health platforms. We also exclude public biotechs such as BioAge Labs, Unity Biotechnology and Longeveron because this comparison is about private startups. Calico sits outside the group as a long-established Alphabet research subsidiary. Loyal works on lifespan drugs for dogs, while Cambrian mainly builds a portfolio of separate aging companies. Both matter to longevity, but neither is a direct peer here.

Private-company funding is messy, so the amounts below are best read as public minimums. NewLimit’s total includes the founders’ original $105 million commitment. Retro announced the first close of a new round in May 2026 at a $1.8 billion pre-money valuation without disclosing its size. Altos launched with $3 billion, and The Wall Street Journal has reported that its total may be close to $6 billion; the company has not confirmed that figure.

Startup	What it is developing	Publicly disclosed or reported funding
Altos Labs	Cellular rejuvenation programs across several tissues and disease areas	At least $3B; nearly $6B reported
NewLimit	Cell-specific epigenetic reprogramming for the liver, immune system and vasculature	About $755M including founder capital; $3.1B valuation reported
Life Biosciences	Controlled OSK reprogramming, beginning with damaged retinal cells; preclinical liver work	About $230M, including an $80M Series D in April 2026
Retro Biosciences	Autophagy drugs, rejuvenated blood and brain cells, tissue reprogramming and AI-designed proteins	At least $180M plus a 2026 round of undisclosed size at a $1.8B pre-money valuation
Rubedo Life Sciences	Drugs that selectively target pathological senescent and stressed cells	About $52M
Turn Biotechnologies	Transient mRNA reprogramming combined with targeted delivery	About $30M
Rejuvenate Bio	Gene therapies for age-related disease, including partial reprogramming research	About $25M
Shift Bioscience	AI-discovered rejuvenation genes designed to avoid pluripotency, led by an anti-fibrotic siRNA	$18M disclosed

Is there a clear leader in aging reversal today?

Life Biosciences is ahead overall. It is alone in testing direct epigenetic rejuvenation in people, and it is the only one with human data from that approach.

The lead is clearer than it was a few months ago, but still narrow. Rubedo has the most controlled early efficacy result in people. Retro has the broadest visible pipeline and runs a Phase 1 program. NewLimit has far more capital than Life and plans to test a more scalable liver therapy in 2027. Altos has an unmatched research budget but still offers no public clinical candidate.

The gap looks very different depending on the metric. On direct human reprogramming, Life stands alone. On controlled efficacy, Rubedo still leads. On capital, Altos is at least 13 times larger than Life and may be more than 25 times larger. NewLimit has roughly 3.3 times Life’s disclosed funding but remains one full clinical stage behind it.

Life has earned first place. Three patients are not enough to make that position secure.

If you want more recent data on this point, see the latest figures in our Longevity report ↓.

Did Life Biosciences’ first eye data show aging reversal in humans?

No. Life’s first data are the most important human signal the field has produced, but they do not prove that a human tissue became younger.

In October 2026, Life reported interim results for three people with open-angle glaucoma who received the lowest dose of ER-100. The company said the treatment was well tolerated through Day 56, with no dose-limiting toxicities, serious adverse events or adverse events of special interest. Two of the three showed improvements on the Humphrey visual-field test, with at least 28% of tested points improving by more than 4 dB. The safety board recommended moving to a dose three times higher.

That is a real step, and it is also a fragile one. The study is open-label, has no control eye or placebo group, and visual-field tests are noisy and can improve as patients learn the test. Life itself says efficacy cannot be established from these findings. The data were presented at a meeting, not in a peer-reviewed paper, and they do not show that retinal cells regained a younger epigenetic state.

A credible human result needs more than a better score. We would want a biological change tied to the mechanism, a lasting functional gain, acceptable safety and controls. Rubedo’s lesion data have controls but cover a narrow skin target. Retro’s Alzheimer’s drug targets autophagy, not cellular age. Human testing has produced its first hints. Human age reversal remains unproven.

Does Life Biosciences now beat Rubedo on human evidence?

Not yet. Life now has the bigger human milestone, but Rubedo still has the better-controlled efficacy signal.

Rubedo reported that RLS-1496 reduced actinic keratosis lesions by 46% after four weeks, compared with 11% on untreated control areas, in the first 18 of 24 patients evaluated. The company reported no serious adverse events, no treatment discontinuations and little local irritation. In its earlier Phase 1 work in Europe, Rubedo also reported a 20% fall in epidermal thickness in treated psoriasis skin versus a 30% increase with vehicle.

Those lesions are visible and countable, which makes the result easy to judge. It is still preliminary and company-reported. Rubedo said in May 2026 that a Phase 2b dose-ranging study should begin in the fourth quarter of 2026, and in September 2026 it announced a separate clinical study of RLS-1496 in hair loss.

Life’s data carry more weight for the aging question because ER-100 aims to reset cellular age directly. They carry less weight as proof: three patients, no comparator and a noisy test. Retro’s RTR242 is also in Phase 1. Its CEO told STAT in May 2026 that no dose-limiting toxicities had been seen, but no RTR242 results have been released. We call this a split decision: Life for significance, Rubedo for rigor.

Startup	Most advanced disclosed program	Human stage today	What the human evidence shows
Rubedo Life Sciences	RLS-1496 for actinic keratosis and inflammatory skin disease	Phase 1 completed; Phase 1b/2a preliminary data; Phase 2b expected Q4 2026	46% lesion reduction versus 11% on untreated areas in an early analysis
Life Biosciences	ER-100 for glaucoma and NAION	Phase 1 active; escalating to second dose level	No serious adverse events in 3 patients through Day 56; visual-field gains in 2 of 3, uncontrolled
Retro Biosciences	RTR242 for Alzheimer’s disease	Phase 1	No dose-limiting toxicities reported by the CEO; no results released
NewLimit	Liver-cell reprogramming therapy	Preclinical	First human study planned for 2027
Altos Labs	Undisclosed rejuvenation programs	Preclinical or undisclosed	No named clinical candidate
Turn Biotechnologies	Transient mRNA reprogramming programs	Preclinical	No human data
Rejuvenate Bio	Human and animal gene-therapy programs	Preclinical in humans	No human data
Shift Bioscience	SB101 siRNA for fibrosis and other rejuvenation targets	Preclinical research	No human data

Why is Life Biosciences still closest to reversing aging?

Life Biosciences stays first because ER-100 is the only direct epigenetic-rejuvenation therapy in human testing, and its first patients have tolerated it.

ER-100 delivers OCT4, SOX2 and KLF4, usually shortened to OSK, to retinal ganglion cells. It leaves out MYC, the fourth classic Yamanaka factor and the one most closely tied to uncontrolled cell growth. Patients take oral doxycycline to switch OSK expression on for a limited period.

Life also has the cleanest path from mechanism to medicine. The underlying research restored youthful gene-expression and methylation patterns in mice, promoted optic-nerve regeneration and improved visual function. The company later reported visual recovery in non-human primates. The FDA cleared the trial in January 2026, the first patient was dosed in the first half of the year, and interim data followed in October.

The eye makes the program safer and easier to test. Doctors can inject one eye, monitor it directly and limit exposure to the rest of the body. Retinal ganglion cells divide very little, which reduces some of the risks of pushing cells toward a more plastic state.

That choice also limits what success would prove. Restoring vision in a damaged eye would be a major medical result, but it would say little about the liver, muscles, immune system or brain. Life has a preclinical liver program in metabolic disease, still far from patients. Life leads after clearing the hardest development hurdle first. Systemic aging is still unsolved.

If you want more recent data on this point, see the latest figures in our Longevity report ↓.

Can NewLimit overtake Life Biosciences in aging reversal?

NewLimit is the strongest threat to Life Biosciences, and the gap could shrink sharply once its liver program reaches the clinic in 2027.

NewLimit has assembled about $755 million from its founders and outside investors: an initial $105 million commitment, a $40 million Series A, a $130 million Series B, a $45 million extension and a $435 million Series C led by Founders Fund in June 2026. That round reportedly valued the company at $3.1 billion. NewLimit has more than three times Life’s capital and enough to run several organ-specific programs at once.

The timeline has also moved much faster than management once expected. In 2025, executives discussed first-in-human work as late as 2030. NewLimit now plans a Phase 1 study in patients with fatty liver disease in 2027, followed by a Phase 2 in alcohol-related liver disease. Cutting about three years from the public timeline matters more than the valuation jump.

The liver is a bold first target. Lipid nanoparticles naturally reach liver cells, so NewLimit can deliver temporary genetic instructions without installing a permanent switch. A successful liver therapy could reach far larger patient populations than an eye gene therapy and create a reusable model for metabolic disease.

NewLimit still has to clear the steps that break many promising biotechs: reproducible animal efficacy, toxicology, manufacturing and regulatory acceptance. Its detailed animal data remain private. On capital, NewLimit leads Life by more than three to one. On human evidence, Life now leads by a full stage and a first dataset.

Is Retro Biosciences’ $1.8 billion valuation backed by trial data?

Not yet. Investors are paying for Retro’s breadth and speed, but its first human drug targets autophagy rather than cellular age, and no results are public.

In May 2026, Retro announced the initial close of a new round led by 4P Capital at a $1.8 billion pre-money valuation, without disclosing the amount. STAT had reported in December 2025 that the company was seeking about $5 billion, so the agreed price came in well below that target.

RTR242 is an oral small molecule meant to restart autophagic flux, the recycling process cells use to clear damaged proteins. Retro moved it from indication selection to first-in-human dosing in about 15 months. Its CEO said in May 2026 that the trial was going well, with no dose-limiting toxicities, and that some data could come around August. No results have been released.

The rest of the pipeline covers several distinct bets. RTR888 uses lab-made microglial progenitors for brain disorders. RTR890 aims to create rejuvenated blood-forming stem cells. AAV programs target osteoarthritis and age-related hearing loss through tissue reprogramming. Retro also runs AI protein design, chemical rejuvenation work and its own cell-therapy manufacturing. The valuation rests on that portfolio and on team speed, not on evidence that any program reverses aging.

Is Altos Labs secretly ahead in reversing aging?

Altos Labs may have the best research machine in longevity, yet the public evidence still places it behind four smaller startups.

Altos began with $3 billion, and The Wall Street Journal has reported that the company has raised nearly twice that amount. It has recruited prominent researchers in reprogramming, stress resilience, epigenetics, computation and drug development. It hired Joan Mannick as chief medical officer and head of product development, launched an Institute of Computation and acquired senescence-focused Dorian Therapeutics.

Those moves point toward products. We still have no named candidate, disease indication, trial registration or expected first dose. After more than four years and several billion dollars, that gap is too large to wave away, especially now that Life has human data.

Altos could have advanced programs behind closed doors, but secrecy cannot count as evidence of leadership. The company has the highest ceiling, the deepest bench and the longest financial runway. It will move up as soon as it shows a therapy close to patients. Until then, companies producing observable clinical milestones deserve the higher positions.

If you want more recent data on this point, see the latest figures in our Longevity report ↓.

Which aging-reversal startup has the strongest animal evidence?

Life Biosciences has the best animal-to-human chain, while Rejuvenate Bio owns the most dramatic published lifespan result.

Life’s program progressed from old and injured mice to non-human primates and now to patients, using the same ocular logic at each step. The mouse work linked OSK treatment to optic-nerve regeneration, better visual function and younger molecular patterns. The primate data added a species with eyes and immune responses closer to humans. The first human visual-field signals are consistent with that chain, even if they cannot yet confirm it.

Rejuvenate Bio produced the more striking lifespan headline. Researchers gave very old male mice an inducible systemic OSK therapy and reported a 109% increase in median remaining lifespan, along with better frailty scores. Because treatment started near the end of life, the treated animals lived roughly twice as long from that late starting point. Their total lifespan did not double.

The Rejuvenate study was small and needs replication across larger groups, female animals and independent laboratories. Its commercial pipeline has leaned toward liver-directed gene therapies and companion-animal programs. Its $6 million financing and Merck Animal Health collaboration, announced in June 2026, strengthen the veterinary route more than direct human reprogramming.

We give Life the edge. Rejuvenate has a provocative organism-level result; Life has carried its animal work into people.

Which aging startup has the safest reprogramming and delivery system?

Life Biosciences has the safest-looking system for one eye, and nobody has solved safe rejuvenation across the body.

Life reduces risk through local AAV2 delivery, three reprogramming factors instead of four and a drug-controlled on-and-off switch, plus a steroid taper to limit inflammation. Its first three patients had no serious adverse events through Day 56, according to the company. That is early support for the design, not proof: the higher dose and longer follow-up still have to hold up.

NewLimit is pursuing a different safety design. It searches for cell-specific factor combinations and plans to deliver temporary instructions with lipid nanoparticles. Transient expression should reduce the danger of uncontrolled long-term reprogramming, and the liver is already a proven destination for this delivery technology. The trade-off is that repeated dosing may be needed.

Turn also favors transient mRNA and added microvesicle delivery through its acquisition of Vesigen’s ARMM technology. Shift looks for single genes that improve cellular age measures without activating pluripotency, and its lead SB101 is an siRNA aimed at liver fibrosis. Both ideas could prove safer than canonical Yamanaka factors, but neither has enough in-vivo evidence to win this comparison today.

The field has solved local delivery better than systemic delivery. Whole-body rejuvenation would require exceptional cell selectivity, careful dose control and proof that treated cells keep their identity. No startup has demonstrated all three.

Which aging startup could scale into a real medicine and find customers?

NewLimit has the most scalable direct-reprogramming design, Retro’s oral autophagy drug is the easiest to distribute, and no aging-reversal startup has real customers yet.

Life’s first product fits an existing medical workflow. Ophthalmologists already inject therapies into the eye, and a one-time treatment could command a high price if it restores lost vision. Viral-vector manufacturing remains expensive, and the same dose design becomes much harder when the target is a large organ.

NewLimit can draw on the industrial base built for mRNA and lipid-nanoparticle medicines. Temporary payloads are easier to modify than permanent gene therapies, and liver delivery is relatively efficient. If NewLimit can reuse the same discovery, formulation and manufacturing system across several liver diseases, its economics should improve with each program.

Retro’s small molecule has the clearest mass-market route because pills are cheap to make and need no specialist procedure. Its cell-replacement programs sit at the expensive end, with collection, manufacturing, conditioning and transplantation for each patient. The internal manufacturing facility gives Retro more control but cannot make those steps disappear.

No company has published usable pricing, payback or manufacturing-cost data. The delivery models are all we can compare, and they favor NewLimit for direct reprogramming and Retro for simple distribution.

Life has active trial sites, a manufacturing relationship with Forge Biologics and an $80 million Series D, raised in April 2026, that the company says funds operations into the second half of 2027. Rubedo has moved from a first human study into follow-on trials and plans a larger Phase 2b study. Those are the closest equivalents to commercial progress in this market.

NewLimit has attracted Eli Lilly Ventures, but an investment is weaker than a licensing deal. Retro works with the Murdoch Children’s Research Institute and has built internal manufacturing. Rejuvenate’s Merck Animal Health collaboration mainly advances therapies for companion animals. Turn’s licensing deal moved in May 2026, when Daewoong Pharmaceutical took over the rights to its rejuvenation platform from HanAll Biopharma, which keeps a Korean pharma partner engaged.

Pilots, investors and research collaborations should not be presented as customer demand. Nobody has shown repeat orders, reimbursement, hospital adoption or patient revenue. The aging-reversal market remains pre-commercial.

Which aging startup is getting the most from its funding?

Rubedo has turned the least capital into the most controlled human efficacy data, with Life Biosciences close behind on a much harder gene-therapy program.

Capital efficiency cannot be reduced to funding divided by trial phase, because a topical cream costs far less to develop than an eye gene therapy or a manufactured cell product. Even with that caveat, the spread is too large to ignore. Rubedo reached preliminary controlled human efficacy with about $52 million. Life opened a first-in-class gene-therapy study and produced first human data with roughly $230 million. NewLimit has about $755 million and remains preclinical, while Altos has spent years on a multibillion-dollar budget without revealing a candidate.

Retro sits in the middle. At least $180 million, before its 2026 round, produced one Phase 1 small molecule, several preclinical programs, a team of more than 90 and an internal manufacturing facility. Rejuvenate has generated unusually interesting mouse data and veterinary partnerships with about $25 million, but its human translation remains limited.

Startup	Approximate funding	Best disclosed development result	Our capital-efficiency view
Rubedo Life Sciences	$52M	Preliminary controlled human efficacy	Best result per dollar so far
Life Biosciences	$230M	First direct reprogramming trial and first human safety and visual-field data	Strong for a gene-therapy platform
Retro Biosciences	$180M plus undisclosed 2026 funding	Phase 1 drug and broad pipeline	Solid, with substantial infrastructure built
Rejuvenate Bio	$25M	Published lifespan and frailty result in old mice	Strong animal output, slow human translation
Turn Biotechnologies	$30M	Preclinical platform and licensing activity	Too early for a firm judgment
Shift Bioscience	$18M	Preclinical siRNA candidate and peer-reviewed AI methods	Too early for a firm judgment
NewLimit	$755M	Clinic-ready liver candidate; trial planned for 2027	Expensive, but development has accelerated sharply
Altos Labs	$3B to nearly $6B reported	No public clinical candidate	Weakest visible translation per dollar

If you want more recent data on this point, see the latest figures in our Longevity report ↓.

Which aging startup is hardest to copy?

Life Biosciences is the hardest aging startup to copy in the clinic, while NewLimit may be building the more valuable long-term data advantage.

Life has licensed intellectual property around therapeutic OSK use and is accumulating manufacturing, toxicology, primate, regulatory and now human know-how around a real product. That combination is harder to copy than the published reprogramming concept. Every patient dosed adds information a later entrant cannot buy.

NewLimit repeatedly designs factor combinations, tests thousands of them and feeds the results back into its models. If that process yields different minimal payloads for liver, immune and vascular cells, its private perturbation dataset could become the field’s strongest discovery asset. The advantage will only become convincing when the platform produces treatments that work in animals and people.

Altos has a different advantage: money, talent and internal data generated across several institutes. Those resources are formidable, although scientists can move and foundational biology spreads through publications. Altos still needs protectable candidates and delivery systems.

Rubedo’s protection comes from its map of pathological senescent-cell subtypes and compounds that target them selectively. Turn combines payload and delivery patents. Shift is building intellectual property around non-Yamanaka rejuvenation genes and in October 2026 announced a Nature Biotechnology paper on benchmarking the AI virtual-cell models it uses to find targets.

Which aging startups are moving fastest right now?

Life is moving fastest in the clinic, NewLimit has accelerated its development timeline the most, and Rubedo is widening its clinical program.

Life went from FDA clearance in January 2026 to first patient dosed, first human data in October and a recommendation to escalate the dose, all within the year. NewLimit brought its first planned trial forward from around 2030 to 2027 and closed a $435 million round in June 2026, one of the largest private biotech rounds of the year. Rubedo followed its first safety study with a measurable lesion result, added a hair-loss study and expects to start a larger dose-ranging trial in the fourth quarter.

Retro also belongs in the leading group. It moved RTR242 into Phase 1 in roughly 15 months, raised new money at a $1.8 billion pre-money valuation and says further first-in-human milestones are planned for 2026 and 2027. Its pace will be judged on whether RTR242 data appear. Rejuvenate’s recent progress, with Merck Animal Health as a research partner, stays concentrated in veterinary medicine.

Altos has added product-development leadership and computational capacity, but its momentum is hard to measure without a candidate. Turn and Shift continue to build useful technology at a much earlier stage.

The four companies gaining the most ground are Life, NewLimit, Rubedo and Retro. Life has the most important clinical position, while NewLimit is moving fastest toward challenging it.

How much of the aging-reversal evidence can we really trust?

Life Biosciences has the easiest evidence to check because its trial is publicly registered and its core animal work is peer-reviewed. Its human data, like most rival claims, still come from company announcements.

Life’s interim data cover three patients, with no control group, and were presented at a conference rather than published. We treat them as a safety signal with a hint of activity. Rubedo’s lesion counts include untreated comparison areas, which makes them more useful than a vague claim of improvement. That analysis covers only the first 18 evaluable patients and has not appeared as a complete peer-reviewed paper. We treat it as promising human evidence rather than a settled result.

NewLimit publishes unusually detailed operating updates, yet the animal safety and efficacy package behind its clinic-ready candidate remains private. Altos discloses even less. Retro shows a clear pipeline and clinical status, while human results are still pending. Turn and Shift rely heavily on platform descriptions and early laboratory findings.

Funding figures are easier to verify than scientific results, but even those differ across databases because founder commitments, grants and extensions are counted differently. That is why we use ranges for Altos and Retro and describe the other totals as approximate.

What could change the aging-reversal ranking?

One convincing human result could still reorder the top five because every current lead rests on early evidence.

Life would pull away if the higher dose stays safe and visual-field gains hold up in more patients, ideally with imaging that supports the intended mechanism. Serious toxicity, fading benefit or results that look like normal test noise would erode its main advantage.

Rubedo could challenge for first place if its Phase 2b study reproduces the early lesion reduction with strong controls, durable effects and tissue evidence that pathological senescent cells were selectively removed. It would then have validated an aging mechanism in people, even while treating a localized disease.

NewLimit has the biggest opportunity to overturn the order. Safe liver-cell rejuvenation would show that direct reprogramming can work in a large internal organ with a scalable delivery system. Retro could rise quickly if RTR242 produces a meaningful Alzheimer’s result and one of its reprogramming or cell-replacement programs reaches patients.

Altos needs one convincing candidate disclosure to re-enter the top group. Its resources make rapid progress possible once a program emerges. Rejuvenate would move up if independent teams reproduce its lifespan result or if the company returns systemic reprogramming to the center of its human pipeline.

Which startups are actually ahead in reversing aging?

Life Biosciences is closest to reversing aging, with Rubedo and NewLimit as the two strongest challengers for very different reasons.

Life ranks first because direct epigenetic rejuvenation has crossed into human testing and produced a first, clean safety readout with early visual-field signals. Rubedo ranks second because it has the clearest controlled human efficacy result against an aging-related cell population. NewLimit ranks third because its liver program combines direct reprogramming, a scalable delivery route and enough capital for a serious clinical campaign.

Retro takes fourth place. Its pipeline is broader and more clinically mature than NewLimit’s overall, but its lead human program does not reset cellular age and has released no results. Altos remains fifth because several billion dollars and exceptional scientists cannot outweigh the absence of a public candidate. Rejuvenate follows on the strength of its old-mouse lifespan result. Turn and Shift have credible ideas, with too little animal and clinical evidence to rank higher.

The distance between first and third is smaller than the funding numbers suggest, though Life widened it in October. Life leads NewLimit by one clinical stage and a first dataset, while NewLimit leads Life by more than threefold in capital and probably in systemic scalability. Rubedo could pass both if its early result survives a larger controlled study and expands beyond skin. For now, Life holds the milestone that matters most.

Rank	Startup	Why it ranks here now
1	Life Biosciences	Only direct epigenetic-rejuvenation therapy in human testing, with first safety data and early visual-field signals in 3 patients
2	Rubedo Life Sciences	Strongest controlled early human efficacy result against an aging-related cellular mechanism; Phase 2b expected Q4 2026
3	NewLimit	Best-positioned direct challenger, with a clinic-ready liver program, a 2027 trial plan and about $755M in capital
4	Retro Biosciences	Broadest visible aging pipeline, one Phase 1 drug and a $1.8B pre-money valuation, but no released human results
5	Altos Labs	Unmatched resources and scientific depth, but no public clinical candidate despite years of work
6	Rejuvenate Bio	Most dramatic published old-mouse lifespan result, with limited progress toward human reprogramming
7	Turn Biotechnologies	Sensible transient mRNA and delivery strategy, now partnered with Daewoong, still short on disclosed in-vivo validation
8	Shift Bioscience	Interesting non-Yamanaka target-discovery approach and a preclinical siRNA lead, with no animal-to-human data yet

If you want more recent data on this point, see the latest figures in our Longevity report ↓.