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Sam Altman, Brian Armstrong and other tech billionaires are pouring a fortune into anti-aging therapies that could take years to hit the market. One startup underdog is beginning to treat customers who may not have the luxury of waiting that long.

The Takeaway

• Tech billionaires are pouring fortunes into cellular reprogramming to with the goal of extending life.
• Mitrix Bio is offering mitochondrial transplants to paying patient-investors.
• One 91-year-old patient has received treatments using his granddaughter’s mitochondria.

In Silicon Valley, some quests for the fountain of youth have most definitely won the backing of tech’s leading names.

Sam Altman, OpenAI’s CEO, personally invested $180 million to launch Retro Biosciences, which is working on ways to rejuvenate aging cells. CoinBase’s Brian Armstrong co-founded NewLimit, which has raised over $200 million for a similar pursuit from investors that include Peter Thiel’s Founders Fund. And Jeff Bezos reportedly helped bankroll a startup focused on life extension therapies, Altos Labs, which has amassed $3 billion in funding.

Then there are longevity startups like Mitrix Bio, a Pleasanton, Calif.–based company that’s working with only $4 million in funding, none of it coming from the tech billionaires who lately have become enthralled by the idea of treating death like a correctable software glitch.

And while the higher-profile companies still have years ahead of expensive clinical trials to try to get possible Food and Drug Administration approval, Mitrix is testing its proposed anti-aging treatment today on customers willing to pay $50,000 for a small share of equity in the company.

“This is patient-funded medicine,” said Tom Benson, founder and CEO of Mitrix.

Those patient-investors include people like John Cramer, a renowned experimental physicist and the author of three science fiction novels. At the age of 91, Cramer has decided he simply can’t wait any longer for treatments that he hopes will improve the quality—and quantity—of his remaining years. His hearing isn’t great, and he has already had cataract surgery and a knee replacement. A cardiologist monitors his irregular heartbeat.

So in February, Cramer flew from his home in Seattle to a clinic in Dallas to receive the third of several longevity treatments from Mitrix at a pain management clinic located in an office building a short drive from the Dallas airport.

While most of Mitrix’s rivals are exploring ways to reprogram the body’s cells to be youthful again, Mitrix focuses on transplanting a single yet crucial component of cells—the mitochondria—from young people to older ones to rejuvenate them. Cramer’s mitochondria donor is Selena Shea, his 26-year-old granddaughter, who accompanied him to Dallas.

Inside the clinic, Cramer lay down on an examination table. The nurse hung a bag of saline on a pole. The liquids would help the mitochondria circulate throughout the body.

“If there are effects,” he asked, “when will I feel them?”

The startups seeking to crack the code of longevity are the latest representation of humanity’s longstanding pursuit of immortality. Medieval alchemists concocted life-extending elixirs. And in the 17th century, doctors gave the ailing king of France blood transfusions from young donors in a bid to extend his life.

The idea that properties in blood can rejuvenate people even entered popular culture as a ghoulish pursuit of wealthy CEOs. A 2017 episode of the show “Silicon Valley” showed a billionaire executive receiving transfusions from a “blood boy” in the vain hope of reversing aging. The 2025 Netflix documentary, “Don’t Die: The Man Who Wants to Live Forever,” filmed software entrepreneur Bryan Johnson receiving a plasma infusion from his teenage son (and donating his own plasma to his father).

The FDA has tried to quash enthusiasm for plasma infusions from the young as a therapy against normal aging, saying there is no evidence it has any health benefits. But other scientific advances over the past decade or so have made the dream of extended longevity seem more viable.

In 2012, two biologists won the Nobel Prize for showing adult skin cells could be reprogrammed and returned to a youthful state. The work ignited further scientific efforts, and many of the longevity startups backed by tech billionaires focus on using cellular reprogramming techniques to treat age-related diseases, including in the eyes and the brain.

“Reprogramming cells really speaks to people here,” said Sonia Arrison, founder of Menlo Park, Calif.–based venture firm 100 Plus Capital and chair of the advocacy group Alliance for Longevity Initiatives. “If biology has a code, which it does, then it can be engineered, and that is exciting to people in Silicon Valley.”

Still, with so many scientists starting companies based on promising early discoveries, it isn’t always easy to know where to draw the line between breakthroughs and hype. Eric Verdin, CEO and president of the Novato, Calif.–based Buck Institute for Research on Aging, calls longevity “a hybrid animal,” combining mainstream biology and scientific research with “a whole series of actors and Instagram medicine influencers that don’t have much to add to the debate except amplify the enthusiasm in the broad public.”

Mitrix’s anti-aging therapy—mitochondrial transplantation—is still awaiting the kind of buzz the cellular reprogramming startups backed by tech billionaires have generated. Benson, the Mitrix CEO, said one reason investors are more excited about cellular reprogramming is the goal of startups in that category is a pill or medicine that can potentially be mass-produced.

“Mitochondrial transplantation is harder to scale,” Benson said. “It requires doctors and hospitals.”

Still, Mitrix believes its approach is crucial to effective anti-aging. That’s because mitochondria are the energy center for the entire cell, powering the activities of daily life. Mitrix’s scientists argue that trying to reprogram cells when age has depleted that energy won’t work. Before attempting to fix cells, they say, you first need to get their power system working again.

“I have quite a lot of sympathy for the idea that if the battery is not working, nothing works,” said Ronjon Nag, an inventor and tech entrepreneur whose Palo Alto, Calif.–based venture capital fund, R42 Group, was an early Mitrix investor.

Other prominent figures have shown interest in mitochondria treatments. Health and Human Services Secretary Robert F. Kennedy Jr. has described mitochondria dysfunction as an important driver of chronic disease. Researchers are pursuing mitochondria-based therapies as possible treatments for stroke, heart attacks and Alzheimer’s disease, conditions that happen more as people get older. Bill Gates has personally funded mitochondria research for Alzheimer’s disease.

Benson says the current mitochondria procedure can be prescribed by a doctor and doesn’t require FDA approval. Mitrix’s goal is to cut out the need for donations from family members and instead grow large quantities of mitochondria in bioreactors—large stainless-steel tanks and centrifuges—located in clinics and hospitals. Those machines will be available whenever someone needs an energy boost to stave off age-related decline.

At least that’s the idea. Benson will likely need a lot more investment to realize that vision. Catching investment waves can be key to success in Silicon Valley, he said, and Mitrix hasn’t done so yet. “Can I survive until the wave crests and I am fashionable after years of being invisible?” Benson asks. The answer isn’t clear yet.

Other forms of survival are on his mind as well. Benson said he feels an obligation to help people like Cramer, his nonagenarian patient, right now. As someone in his 60s, he feels he has more personally invested than some of his startup rivals in trying to turn back time for older people sooner rather than later.

“Maybe Sam Altman isn’t in a rush,” Benson said. “He is only 40.”

So far, Mitrix has performed its mitochondrial transplants on two people: Cramer and a 71-year-old Houston-based lawyer, Clay Rawlings, whose nephew was his mitochondria donor. Both men are expected to get another injection soon, after which Mitrix will analyze safety data and make changes if needed. The company is hoping to treat three more older participants by the end of the year, according to Benson.

The FDA has not said whether it permits people to use mitochondrial transplantation for anti-aging. In response to a question about it, the agency sent a link to a published advisory that bars the use of donor mitochondria in a fertility procedure that prevents mothers from transmitting mitochondrial diseases to their offspring.

Mitrix’s willingness to perform its longevity treatments on older patients sets it apart from drug companies, which historically have been reluctant to allow people in their 60s into clinical trials, let alone those who are decades older. The fear is that older people are more likely to already have multiple health problems and may have a reaction that puts them and the clinical program in jeopardy.

The field of medicine has also developed extensive ethical rules designed to protect research subjects from overenthusiastic investigators who might take too many risks, either because they are convinced they are right or because they have a financial stake in a drug’s success. Those rules get blurrier when the people taking the experimental drug are also investing in it.

Benson said researchers in the longevity field still debate about how—or if it is even possible—to measure whether a therapy reversed someone’s age. Benson said they will consider the current experiment a success if they can show the treatment is safe and the men’s blood and urine tests remain normal.

Duncan Davidson, a 73-year-old San Francisco venture capitalist who is considering getting Mitrix’s treatment, said he isn’t trying to live to 130. Davidson has already taken steps to improve his longevity by losing weight, working out on his Peloton bike and cutting sugar out of his diet, and he would be content if the treatment could help him avoid major health challenges in the coming years.

“I’d like to go back to 10 years younger and sustain that for at least another 10 years,” said Davidson, adding that both of his parents died when they were 80.

For Cramer, getting mitochondrial transplants was the culmination of years of personal research into aging and experimentation with various methods to mitigate its effects.

He dug into papers about the biology of aging and wrote a book about anti-aging treatments. He reached out to other scientists and joined the many online groups where people shared their longevity regimens. Over the years, he tried vitamins and other supplements, and he still takes a daily dose of metformin, a drug prescribed to Type 2 diabetes patients to lower glucose production that has become popular among longevity enthusiasts. He has also experimented with spending time in a hyperbaric oxygen chamber.

Cramer felt comfortable being a guinea pig. He spent his career as an experimental physicist, teaching at the University of Washington, then traveling across the country to New York to conduct research on the origins of the universe at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider. When thinking about the possible risks of getting mitochondria infusions, Cramer took into account his good fortune in making it to his 90s without any debilitating illnesses.

“I am not sure how much longer that will last,” Cramer said.

His wife of 64 years, Pauline, has not been so fortunate. A few years ago, she broke both of her hips over an 18-month period. Pauline, a scientist who had once worked in the aerospace industry, also suffers from advancing dementia. In 2023, their granddaughter Shea relocated to Seattle to live with the couple. The day after Christmas in 2024, Pauline moved to a small nursing home.

At the clinic in Dallas, Cramer’s spirits were high as he regaled nurses with stories of his adventures in life and science. But after the infusion, he looked tired. It had been a long day.

Shea and Cramer had already decided that after the procedure, they would go to a happy hour back at their hotel. Cramer planned to celebrate with a Scotch. First, though, the doctors at the clinic told them to wait a little longer to make sure he didn’t have an adverse reaction to the therapy, just to be on the safe side.

Shea remained by her grandfather’s side. The doctors’ words of caution reminded her, she said, that “I’m letting them do experiments on my grandpa.”