An injectable gene therapy that promises to make people live longer will soon become available in certain nations. This is despite the fact that it hasn’t been tested in rigorous clinical trials and doesn’t have approval from the US Food and Drug Administration (FDA) or other major regulators.

The gene therapy, developed by Minicircle – a company headquartered in Austin, Texas – is designed to make cells produce more of an anti-ageing protein called klotho. To get around the extensive clinical testing required by the FDA to approve a therapeutic product in the US, Minicircle will offer the largely untested gene therapy to those willing to travel to Honduras, the Bahamas or Panama. The company has opened a waitlist on its website and says it will make the treatment available in the next six months.

Medical ethicists warn that it is reckless to sidestep regulations put in place to protect people from potentially dangerous or useless therapies. “This is the ‘move fast and break things’ mentality of Silicon Valley encroaching on medicine, but the risk is that moving fast with drug development may break people,” says Christopher Rudge at the University of Sydney, Australia.

The anti-ageing effects of klotho, named after a mythological Greek goddess said to spin the thread of life, have been known since the 1990s, when mice lacking the protein were found to age rapidly and die young. Since then, mice that have been genetically engineered to produce excess klotho have been shown to live up to 30 per cent longer. Injections of the protein have also been found to improve memory in older monkeys.

In people, klotho levels naturally decline with age, leading Minicircle and others to try to find ways to replenish them. However, “there have been so many things that have been found to extend lifespan in mice that don’t work in humans”, says Christopher Gyngell at the University of Melbourne, Australia. What’s more, a case report of an infant with excess klotho levels due to a rare genetic condition found she had weak bones and growth problems, suggesting that too much of the protein may be harmful.

Minicircle’s website says its “life-extension” gene therapy contains small, circular DNA called minicircle DNA that provides instructions on how to synthesise the klotho protein. It is injected into a person’s abdominal fat, where the minicircle DNA is absorbed into fat cells. This prompts them to produce klotho, which then circulates around the body. The introduced DNA enters the nucleus of the fat cell, but stays outside the chromosomes, meaning it doesn’t integrate into a person’s genome and eventually breaks down and gets cleared from the body. The company estimates the effects could last for up to a year.

Minicircle says it would cost more than $300,000 to file an application with the FDA to conduct a clinical trial of the gene therapy in the US, and it would take up to three years to get approval to begin one. As a workaround, it recently conducted a “proof of concept” trial in around 24 people in the US who travelled to “international partner clinics” to receive the gene therapy, starting in October 2025. One of the company’s partner clinics is in an experimental “innovation-friendly” city in Honduras called Próspera that allows drug developers to “opt in to the regulations that most suit your business needs”. The others are in Panama City and Paradise Island, Bahamas.

The company hasn’t published the results of its klotho gene-therapy trial, but its website states it is “preparing clinical trial data for publication”. The company’s founder and CEO, Mac Davis, told The New Republic last year that he had received it himself and experienced some dizziness and odd, altered perceptions of time, but that these symptoms resolved. He also said his immune system felt stronger and he had reduced food sensitivities. The company didn’t respond to requests from New Scientist for information about the study results or to a request for a comment more generally.

A trial in just 24 people lasting less than a year and without a control group isn’t adequate to confirm safety or efficacy, says Gyngell. “If you’ve got this thing in your body that is continuously producing a protein, maybe in five years’ time you’ll start to see serious adverse effects,” he says. “People have died in trials of other gene therapies, even rigorously controlled ones with independent oversight, because it’s still a novel area with a high risk of adverse effects.”

No other klotho-boosting gene therapy has been tested in people to date. Miguel Chillón at the Autonomous University of Barcelona, Spain, and his colleagues recently developed another klotho gene therapy, but they have only tested it in mice. These mice lived 20 per cent longer than usual, but also experienced anal bleeding and skin ulcers. Chillón and his colleagues are now focusing on a gene therapy based on a smaller version of klotho that, so far, appears to have fewer side effects. If it enters clinical trials, they will be conducted within the “normal regulatory framework”, says Chillón.

If a company like Minicircle moves too fast and something goes wrong, it will affect everyone else in the field who is playing by the rules, says Alex John London at Carnegie Mellon University in Pittsburgh, Pennsylvania. “If you’ve been investing years trying to find an intervention that might be safe and effective, and then somebody else goes off and, without careful preparation and controls, they administer something like [this gene therapy] and there’s a bad adverse effect, it could derail the whole thing and tarnish you as well.”

While it is true that the development of new medicines is eye-wateringly expensive, this is because “human biology is hard and it’s incredibly difficult to make something that works and is safe”, says London. Extensive clinical testing is necessary because therapies that seem promising in small trials often end up failing in larger, more rigorous ones, he says.

“The regulatory rules these companies [like Minicircle] complain of are not the red tape of overzealous bureaucrats,” says Rudge. “They’re the direct inheritance of past tragedies, and that’s easy to forget when you’re focused only on the opportunities.”

Since 2022, Minicircle has also offered another non-FDA-approved gene therapy at its offshore clinics that is meant to build muscle by increasing levels of a protein called follistatin. In preliminary testing, 43 people aged 23 to 88 received the follistatin gene therapy at the Próspera clinic.

The company reported that it increased their lean muscle mass by an average of 770 grams after 3 months, without adverse effects, but the trial didn’t include a control group, so it is unclear whether this was just a placebo effect. Bryan Johnson, the tech millionaire famous for going to extreme lengths to enhance his longevity, received the follistatin gene therapy in the documentary Don’t Die, and claimed it increased his muscle mass by 7 per cent. The treatment reportedly costs $25,000.

“If people want to be guinea pigs for these kinds of things, then I’m actually sympathetic to that, but only if they have a good understanding of the potential risks and benefits,” says Gyngell. “In the case of these gene therapies, I think there’s too much uncertainty to meet that benchmark.”