Milestones
- Programs disclosed2023Complete.
- Studies needed before trialsNowCurrent milestone.
Physics limits
- Lab-made blood stem cells rarely engraftAfter decades of work, blood stem cells made from stem-cell lines still rarely rebuild a whole blood system long term the way donor marrow does; the natural signals are not fully known.
- New cells need roomTransplanted blood or brain immune cells usually only settle in if old ones are cleared first, often with chemotherapy or radiation, which is dangerous for frail older people.
- Every cell division risks a mutationGrowing billions of cells from one line takes many divisions, each adding DNA copying errors. Cancer-linked changes have to be screened out of every batch.
How it works
Source
Start from stem cells
Induced pluripotent stem cells, adult cells turned back into embryo-like cells, are grown in bulk as a renewable supply.
Guide
Steer them into the right cell
Chemical signals guide them to become blood stem cells (RTR890) or precursors of microglia, the brain's immune cells (RTR888).
Replace
Swap old cells for young ones
Transplanted young cells are meant to settle in and take over from aged, inflamed or faulty ones in blood or brain.
About Retro Biosciences
Retro Biosciences
Cell-cleanup pill, young cell transplants, AI
Bay Area company founded in 2021 by Joe Betts-LaCroix with $180M from Sam Altman, aiming to add ten healthy years to human life. It makes young replacement cells for blood and brain, and RTR242, a pill for Alzheimer's that entered trials in 2025.
- RTR242 went from choosing a disease to the first human dose in about 15 months (trial in Adelaide, Australia).
- In 2025 Retro and OpenAI reported AI-designed versions of two Yamanaka factors that worked better in lab cells.
- May 2026: first close of a new round at a $1.8B valuation, led by 4P Capital.
- Founded
- 20215 yrs
- Headquarters
- United States
- Status
- Private
- Valuation
- $1.8BprivateMay 2026
- Raised
- $180M2 rounds
- Last round
- New round (initial close)May 2026
- Coverage
- 3 programs · 5 updateslatest 1 May 2026checked 25 Sep
- Lead investors
- 4P CapitalSam Altman
- Partners
- OpenAI (opens openai.com)
- People
- Joe Betts-LaCroix (opens retro.bio)Co-founder and CEOSam Altman (opens en.wikipedia.org)Founding investor