Why perfusion alone can't indefinitely preserve organs

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This is an interview with Hunter Davis, the CSO and co-founder (alongside Laura Deming) of Until Labs, which you may also know by its prior name, Cradle. They are a biotech startup devoted to organ-scale cryopreservation. They raised a $58M Series A back in September 2025, and are backed by Founders Fund (especially interesting!), Lux Ventures, and others.

In this interview, we mainly talk about the engineering and scientific difficulties in the cryopreservation field, including some background details on their September 2024 progress report on neural slice rewarming, how they characterize tissue damage in their attempts to do kidney cryopreservation, the potential economics of future cryopreservation protocols, and lots more.

One of the most interesting conversations I’ve had in a long time. If any of this work seems interesting, Until Labs is actively and aggressively hiring!

Enjoy!

Substack + Transcript: https://www.owlposting.com/p/bringing-organ-scale-cryopreservation

Spotify: https://open.spotify.com/episode/23g2lR7dWl8NXUn893KMgv?si=5628cd0e56184130

Apple Podcasts: https://podcasts.apple.com/us/podcast/bringing-organ-scale-cryopreservation-into-existence/id1758545538?i=1000738128994

Youtube: https://youtu.be/xaqwPd3ujHg

Timestamps:

[00:01:50] Introduction

[00:05:00] Why don’t we have reversible cryopreservation today?

[00:07:05] Why is freezing necessary at all for preservation?

[00:08:23] Let’s discuss cryoprotectant agents

[00:14:09] Until Lab’s 2024 progress report on neural tissue cryopreservation

[00:20:28] How do you measure cryopreserved tissue damage?

[00:22:34] Translation across species

[00:26:04] Why was the cryopreservation storage time so short in the progress report?

[00:30:47] Nuances of loading cryoprotectants into tissue

[00:37:03] Let’s discuss rewarming

[00:43:02] What scientific problems amongst vitrification and rewarming keep you up at night?

[00:45:58] Why are there so few cryoprotectants?

[00:48:11] How can you improve rewarming capabilities?

[00:53:03] What are the experimental costs of running cryopreservation studies?

[00:57:49] What happens to the cryoprotectants and iron oxide nanoparticles after the organ has been thawed?

[01:01:34] Cryopreservation and immune response

[01:03:25] How do you filter through the cryopreservation literature

[01:05:54] How much is molecular simulation used at Until Labs?

[01:10:04] What are the (expected) economics of Until Labs?

[01:14:49] How much does cryopreservation practically solve the organ shortage problem?

[01:17:04] Synergy between xenotransplantation and cryopreservation

[01:21:12] How much will the final cryopreservation protocol likely cost?

[01:21:58] Who ends up paying for this?

[01:23:28] What was it like to raise a Series A on such an unorthodox thesis?

[01:27:49] What are common misconceptions people have about cryopreservation?

[01:29:58] The beginnings of Until Labs

[01:34:07] What expertise is hardest to recruit for?

[01:39:27] What personality type do you most value when hiring?

[01:44:17] Why work in cryopreservation as opposed to anything else?

[01:46:26] Until Lab’s competitors

[01:49:30] What would an alternative universe version of Hunter worked on?

[01:51:33] What would you do with $100M?