Retro Biosciences, the longevity company funded by OpenAI chief Sam Altman, is expanding its first test in people of a pill it hopes could one day fight dementia1. The reason is unusual. According to the company’s CEO, the doses given so far have caused no major side effects, so researchers cannot yet tell where the best dose lies1.
What happened
In an interview published by Business Insider on August 26, 2026, CEO Joe Betts-LaCroix said Retro is adding two new groups of volunteers to its safety trial of the pill, called RTR2421. The trial is a Phase 1 study, the first stage of human testing, which mainly checks safety and dosing. Enrollment is growing by more than 42%, from 76 to 108 participants1.
The trial is running in Australia2. Betts-LaCroix said there have been “no major side effects, no safety signals” so far, according to Business Insider’s account1. He described this as a mixed result for the company:
“It’s sort of like a curse and a blessing for us, in that it makes it a little bit hard to measure that ‘Yay; it’s doing the thing,’”
He added: “Hopefully, at some point, we will at least get headaches or something”1. The goal is a dose strong enough to have an effect but without severe side effects1.
Coverage framed the news in different ways. One syndicated version of the Business Insider story ran under a headline saying the company was raising the dose “after disappointing trial results,” while Longevity Technology described the move as widening the trial after early doses “showed no red flags”3.
How the pill is meant to work
Cells constantly break down and reuse their own worn-out parts, a process called autophagy (from the Greek for “self-eating”). Retro says this recycling declines with age2. The final step happens in lysosomes, small sacs inside cells that use acid to break old proteins into reusable pieces1. Their cleaning power often weakens as we age, which is closely tied to biological aging, age-related disease and inflammation1.
RTR242 is meant to restore the acidity of these sacs so they work better again1. Retro calls it a “first-in-class” pill, meaning the first drug of its kind, and says it crosses the blood–brain barrier, the filter that keeps many drugs out of the brain2. The recycling process gets especially clogged in people with brain diseases such as Alzheimer’s and Parkinson’s, which is why the company is aiming first at Alzheimer’s12.
The evidence so far
The evidence rests on the company’s own description. Retro announced it had reached its “first in human” milestone in the last three months of 2025, becoming a company with a drug in clinical testing3. An encyclopedia entry based on the company’s website, accessed in October 2025, still listed RTR242 as being in preclinical development, the stage before human testing4.
Business Insider reported that the drug had been in trials in Australia for several months at the time of the interview1. No trial data have been published. The safety picture comes from the CEO’s statements, not from figures outsiders can check.
What it does not show yet
A safety trial in healthy people cannot show whether a drug slows dementia. The volunteers are aged 18 to 65, which makes it hard to know how the pill will perform in older adults with memory decline1. Business Insider noted that the lysosome idea is being explored by several startups but has not yet succeeded in the clinic1.
Paul Robbins, a biochemist and aging researcher at the University of Minnesota who is not involved in the trial, called the lysosome an “interesting target,” especially for memory decline and dementia1. “If they’re not seeing toxicity, that’s great,” he told Business Insider1. He was cautious because the company has shared few details about exactly how the drug works, and because it has not been tested in people with dementia1.
“There are other ways to stimulate autophagy. We’ll have to see if this is the right way or not.”
That was Robbins’s summary1.
Who is behind it
Retro Biosciences was founded in 2021 and is based in Redwood City, California5. About 90 people work there toward a goal of adding 10 healthy years to the human lifespan1. Its founders and leaders include Joe Betts-LaCroix, Jessica Sprueill, Sheng Ding, Alex Trapp and Peng Liu4.
Sam Altman provided the initial $180 million that seeded the company6. In January 2025, Fortune reported that Retro was raising a $1 billion round, with some money coming from Altman and the round led by Italian financier Sandro Salsano, who joined the board6. In May 2026, Retro announced the initial close of a financing round led by 4P Capital that values the company at $1.8 billion; the company said the money would fund RTR242’s clinical work, among other programs3.
The project is also personal for its CEO. Betts-LaCroix lost his father to Alzheimer’s earlier in 20261. “You make it into your 90s and then, damn. It comes along and strips your personhood out right from under you,” he told Business Insider1. In 2025 he set an ambitious timeline: “we’re going to have our first drug out in the 2020s”6.
How it fits the field
Retro is one of several well-funded Silicon Valley companies trying to treat aging itself. Business Insider reported that two others, the Bezos-backed Altos Labs and the Founders Fund-backed New Limit, had not announced any human trials, which arguably puts Retro ahead in reaching people1. Retro is not alone in targeting lysosomes for brain health; Boston-based Lysoway Therapeutics is also developing lysosome-targeting drugs1.
The pill is only one of Retro’s programs. The company is also working on replacing aging brain immune cells called microglia with young ones grown from stem cells, on making young blood stem cells from a patient’s own cells, on gene therapy for the knee and inner ear, and on proteins designed with OpenAI’s AI model2. It has built a blood cell manufacturing lab meant to meet Food and Drug Administration standards1.
Other groups are testing different routes to protecting the aging brain. Biohack recently covered an Alzheimer’s drug being tested in healthy people to see if it can prevent disease.
What to watch next
- Whether the two new groups on stronger doses produce side effects that help define a usable dose1.
- Whether Retro publishes any safety or dosing data from the Australian trial.
- When the company moves to testing in older adults or people with Alzheimer’s, which would be needed to show any benefit1.
- Progress on Retro’s cell therapies for the brain and blood, which the company lists as preparing for human testing2.
