As investors pour billions into the promise of longer, healthier lives, a new wave of longevity startups is pushing aging science out of the lab and toward the clinic. Companies like Retro Biosciences, NewLimit, and Insilico Medicine are using new tools including AI and cellular reprogramming to turn back the clock and prolong the span of a healthy, happy human life. Backed by Silicon Valley heavyweights, these companies are chasing ambitious timelines and enormous markets, even as the science moves cautiously. 

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BY MELISSA ANGELL, SENIOR STAFF WRITER

How Retro Biosciences, NewLimit, and Insilico Medicine are using novel techniques, from AI to cellular reprogramming, to unlock longer, healthier lifespans.

“How old would you like to be when you die?” That’s the question my primary care physician asked during my routine physical. It’s a complex question, one without a right answer. As long as possible, is what some people might automatically think. But most people would rather live a healthy and active 75 years rather than a 90-year lifespan punctuated with excruciating chronic pain and severe illness.

Joe Betts‑LaCroix, CEO and co‑founder of Retro Biosciences, has spent the past decade asking the same question. While working at the Health Extension Foundation, a nonprofit that invests in biomedical research, Betts‑LaCroix and his colleagues, with the help of a professional survey firm, canvassed thousands of people to ask how many years they wanted to live. 

They split respondents into two groups: The first was asked to name an age, with no additional context, and most of these answers clustered in the 80s. The second group was asked a different version of the question: How long would you want to live if you could feel as healthy as you did in your 20s, indefinitely? Many respondents said 150. Some checked the survey’s “forever” box.

Faced with the shift in questioning, “the psychology completely transformed,” Betts‑LaCroix says. “People suddenly realized, wait, health really matters.”

Retro Biosciences is focused on cellular reprogramming and cellular rejuvenation—making aging cells behave like younger ones. As we age, our cells wear out and begin to behave differently, turning certain genes on and off in ways that contribute to disease and decline. Scientists have discovered that a small set of proteins, known as Yamanaka factors, can partially reverse that process, nudging old cells back toward a younger state. Retro’s bet is that carefully controlling this reset could rejuvenate cells without the dangerous side effects that come from fully rewinding them.

This insight lies at the core of Retro Biosciences’ mission: add 10 healthy years to the human lifespan. “There’s no good to be brought into the world by taking someone who’s already miserable and keeping them miserable for longer,” Betts-LaCroix says.

Why 10 years, and not 8, or 12, or 150 years, like respondents said they wanted? Betts‑LaCroix says the number isn’t an exact science. Biology is messy, and there are plenty of unknowns. But there’s also a practical reason. Adding just a couple of healthy years to a lifespan is relatively easy. Ten, by contrast, is ambitious enough to matter and hard enough to force real breakthroughs.

In 2022, as Retro emerged from stealth mode, the company announced that the largest individual investment ever made in a longevity startup—$180 million—had been made by Sam Altman, CEO of OpenAI.

Retro has partnered with OpenAI to create an AI model specifically dedicated to improving those proteins. Using a model based on the GPT architecture, Retro scientists were able to tweak existing Yamanaka factors, greatly improving the number of cells the reprogramming process could successfully rejuvenate. The goal is to restore cellular health, not just add more years at any cost. 

In addition to its Altman-backed seed round, Retro is now raising a $1 billion Series A round at a reported $5 billion valuation. Last December, the company launched its first human trial in Australia of an autophagy enhancement-focused drug targeting diseases like Alzheimer’s.  

“The market size is incomprehensible–every human being on earth is a customer,” says Jordan Weiss, an assistant professor at New York University’s medical school within the Optimal Aging Institute. “Aging is the only sort of true universal condition that many of us face. There’s really no bigger market, and I think VCs figured that out.”

An increasing number of Silicon Valley tech entrepreneurs are making similar investments to extend and improve the quality of human life.

Oracle founder Larry Ellison, for example, created the Ellison Foundation to fund research aimed at slowing—or even preventing—biological aging, committing roughly $40 million a year to the effort. Google co‑founder Sergey Brin has taken a similar interest, backing Calico, a research company focused on understanding the biology of aging. Other billionaire‑backed efforts include Altos Labs, which launched in 2022 with $3 billion in funding, backed by Jeff Bezos, and Unity Biotechnology, supported by both Bezos and Peter Thiel.

NewLimit is a longevity biotech startup working on several longevity projects. The one that is furthest along involves developing technology to make old liver cells act young again. They do this by using lipid nanoparticles—tiny fat bubbles, a delivery system used in existing medicines—to carry mRNA into liver cells. Once inside, that mRNA tells the cells which genes to switch back on, restoring capabilities like breaking down alcohol and caffeine that the cells lose as they age.

In the same way GLP-1 drugs were first approved to treat diabetes and later expanded to treat obesity, NewLimit hopes to gain FDA approval for alcohol-related liver disease first, and then expand to broader conditions like metabolic syndrome over time.

In 2023, NewLimit raised $40 million in Series A funding, which they used to underwrite the discovery aspect of NewLimit’s work, says co-founder Jacob Kimmel, who has a PhD in developmental and stem cell biology. Its $140 million Series B round, led by Kleiner Perkins, will now enable the company to get one of its medicines into clinical trials and expand its pipeline. 

“For every dollar we invest, we actually discover more of these really interesting preclinical hits,” says Kimmel, acknowledging that the R&D here will take several years until NewLimit achieves its ultimate desired outcome—reversing aging at a cellular level through epigenetic reprogramming.

So what does that look like in a real-world scenario? When these treatments eventually reach the market, who will actually be able to afford them? Critics are already asking whether longevity will remain a luxury product, available only to those who can afford cutting-edge cellular therapies. Other concerns might emerge as overall lifespan is extended. Once these interventions become possible, where do we draw the line between extending life and distorting it?

Alex Zhavoronkov, the CEO and founder of Insilico Medicine, a longevity biotechnology company headquartered in Cambridge, Massachusetts, dismisses these concerns about equity and ethics. “Those arguments deprive this industry of the proper attention and funding it deserves,” Zhavoronkov says. “It’s kind of like arguing against airplanes because people would not be able to fly business class.”

Insilico went public on the Hong Kong Stock Exchange last December, raising nearly $293 million USD (HK$2.28 billion). The company prides itself on having more than 30 drugs within its pipeline, with its leading program, which targets lung fibrosis, completing a phase two clinical trial in China with a parallel phase two study ongoing in the United States. This kind of versatility in a drug pipeline has been a challenge for many biotech companies. While running multiple trials with different sets of focus areas can increase the odds of success, that approach also runs up costs and dilutes focus. And failure rates are high in the rigorous process of clinical trials, with one paper stating that nearly 60 percent of drugs fail to pass phase three trials.

AI may be accelerating discovery, and investors may be writing ever‑larger checks, but the science of longevity still moves on biology’s timeline, not Silicon Valley’s. Even optimistic scenarios put consumer‑ready therapies 10 to 15 years out, a reminder that aging, unlike software, doesn’t ship on a sprint schedule.