Sam Altman-backed Retro Biosciences is widening its Alzheimer’s trial after early doses showed no red flags.
Most drug trials pray for a boring readout. Retro Biosciences got exactly that, and now it has a problem precisely because nothing went wrong.
The Sam Altman-funded longevity startup is testing a pill called RTR-242, designed to help the brain clear out cellular junk that piles up with age and is thought to worsen conditions like Alzheimer’s and Parkinson’s [1].
According to Retro CEO Joe Betts-LaCroix, the drug’s early safety data has been almost suspiciously clean: no major side effects, no safety signals, nothing. Betts-LaCroix told Business Insider that’s a mixed blessing. Without any signal at all, it’s hard to know whether the drug is actually doing anything, or simply not doing enough.
So Retro is upping the dose and the headcount. The company is adding two new cohorts to its Phase 1 safety trial, expanding total enrollment by more than 42%, from 76 to 108 participants. The hope, somewhat counterintuitively, is to see something.
“Hopefully, at some point, we will at least get headaches or something,” Betts-LaCroix said, only half-joking about the search for a dose potent enough to matter without becoming unsafe.
How the pill is supposed to work
RTR-242 targets lysosomes, the recycling centers inside every cell that break down old, damaged proteins so the cell can reuse the parts. That recycling process, called autophagy, tends to slow down with age, and researchers increasingly view a sluggish cleanup system as one of the threads connecting general aging to specific neurodegenerative diseases. Retro’s drug is designed to restore the acidity that aging lysosomes lose, essentially sharpening a dulled tool rather than replacing it.
Retro isn’t alone in betting on this mechanism. Boston-based Lysoway Therapeutics began its own first-in-human trial targeting lysosomes in May, backed in part by the Michael J Fox Foundation. That same month, Chicago’s Vanqua Bio reported promising early safety results from a similar approach aimed at Parkinson’s. It’s a crowded corner of neuroscience, but crowded doesn’t mean solved; nobody has yet proven a lysosome-targeting drug works in patients.
Paul Robbins, a biochemist and longevity researcher at the University of Minnesota who isn’t involved in the Retro trial, called the lysosome an “interesting target,” particularly for cognitive decline. He said he’s encouraged by the lack of toxicity so far, but wants to see more before celebrating.
“If they’re not seeing toxicity, that’s great,” Robbins said, adding that he doesn’t yet know exactly how the drug works or whether it will help people who actually have dementia, since RTR-242 is currently being tested only in healthy volunteers ages 18 to 65.
The personal math behind the science
For Betts-LaCroix, the project isn’t abstract. He lost his father to Alzheimer’s earlier this year.
“You make it into your 90s and then, damn. It comes along and strips your personhood out right from under you,” he said.
That’s really the pitch behind the whole longevity category Retro competes in: not immortality, but more good years, and fewer of them lost to diseases that erase who a person is before the body gives out.
Retro Biosciences says its broader mission is adding ten healthy years to the human lifespan, and RTR-242 is its most concrete swing at that goal so far. Rivals like Altos Labs and New Limit are working on their own approaches to aging biology, but as of now, neither has announced a drug in human trials, which puts Retro, for the moment, a step ahead in the race to find the first genuine longevity drug. Whether that lead holds may come down to something as unglamorous as finding the right dose.
[1] https://www.businessinsider.com/retro-biotech-testing-higher-doses-of-rtr-242-alzheimers-drug-2026-8
