Until’s Series A

We’ve closed a $58M Series A, led by Founders Fund with Lux and Field Ventures joining, to support development of an organ cryopreservation product. In the near term, this will help transplant patients and surgeons access the organs they need. This also serves as an important step in our long-term roadmap to medical hibernation.

The timing of an organ donation is critical. Most organs remain viable for only hours after procurement — 4–12 for hearts, lungs, and livers; 24–36 for kidneys (Donor Alliance). That constraint shapes the entire system: patients must stay within two hours of their transplant center, surgeons often charter planes to personally pick up the donation, and thousands of organs are lost each year to logistical delays or lack of a timely match. In 2024, of the ~106,000 patients on transplant waitlist, ~46,000 received organs (HRSA). But this undercounts. Many patients with advanced organ failure are never even listed due to strict eligibility criteria, expected low donor availability, or institutional limits on the number of candidates they can realistically serve. We’re building reversible cryopreservation so that every donated organ with the potential to save a life, can.

At Until, we develop novel molecular agents, perfusion and surgical protocols, and cooling and rewarming hardware to support reversible cryopreservation of biological systems. We started our research in slices of neural tissue, and now we’re working on preclinical model organs. In addition to providing urgently needed help to patients in the near future, these milestones lay a foundation for our long-term vision of whole-body medical hibernation technology.

In the past year, we’ve spun up a cryoprotective agent (CPA) discovery engine, built a custom electromagnet, scaled to testing protocols in large animal organs, and iterated through multiple novel methods to reduce time spent cooling the organ. We’re currently focused on developing protocols that maximize organ quality post cryopreservation.

Our lab traverses disciplines — a single day at Until might span simulating molecular dynamics, running benchtop assays with high throughput liquid-handling robots, mapping vasculature, exploring the physics of high voltage electromagnets, or designing topologically optimized heat exchangers. Our perfusion experts and molecular biologists work in close collaboration with our hardware engineers and physicists.

The team is diverse by design because the problem is diverse by nature. We move between theory and practice, from first principles to functional prototypes. If you’re energized by deep technical problems, mission-driven science, and rendering technology to extend human well-being, join us.