Scarlet Therapeutics raises £3.2m seed to reduce donor dependence with lab‑grown RBCs
This article covers Scarlet Therapeutics, a Bristol biotech startup, closing a £3.2m seed funding round after reporting preclinical evidence that its lab-grown universal red blood cells mature and circulate in vivo with a half-life comparable to donated blood. The funding and results aim to accelerate selection of a lead therapeutic candidate, in vivo proof-of-concept studies, manufacturing development and regulatory engagement, with potential implications for transfusion services, patients with rare blood types and therapeutic delivery for metabolic diseases.
Scarlet Therapeutics, a Bristol biotech startup, has closed a £3.2 million seed funding round after reporting preclinical evidence that its lab-grown, universal red blood cells (RBCs) mature and circulate in vivo with a half-life comparable to donated blood. The result and the funding together aim to accelerate selection of a lead therapeutic candidate, in vivo proof-of-concept work, manufacturing development and regulatory engagement.
Why it matters
Scarlet’s announcement addresses two persistent constraints in transfusion medicine: donor dependency and blood-type compatibility. A universal, cell-line derived RBC that survives and circulates like donated blood could simplify logistics for hospitals, reduce the need for matched donations, and create a consistent supply for patients with rare blood types or complex transfusion needs. For metabolic disease indications, engineered RBCs that carry therapeutic proteins could offer long-acting delivery with a familiar pharmacology and circulation profile.
The finding — comparable half-life to donated RBCs in vivo — is an important preclinical validation step. It does not equate to clinical proof of safety or efficacy, but it is a milestone that supports moving into animal and human proof-of-concept studies.
Inside the product
Scarlet’s platform is based on a proprietary cell line that generates manufactured RBCs intended to be universal across blood types. The company describes three application streams:
- Treat: long‑acting therapeutic RBCs (tRBCs) engineered to carry and release therapeutic proteins for diseases such as metabolic disorders.
- Transfuse: universal “off‑the‑shelf” transfusion products that aim to reduce reliance on donor blood and simplify compatibility requirements.
- Enhance: next‑generation RBCs designed to modify or improve physiological performance (a longer‑term research direction).
The company says the seed capital will be used to advance in vivo proof-of-concept studies, scale manufacturing processes, and engage with regulators ahead of clinical development. Scarlet also cites foundational research from the University of Bristol and references the RESTORE study, an ongoing first-in-human trial comparing survival of lab-grown RBCs with donated RBCs.
Who are the investors?
The seed round was led by Eos Advisory, with participation from existing investor SCVC and new investors Oshen Bio (Switzerland & Luxembourg) and Daft Capital (US). The financing totals £3.2 million and is earmarked for platform development and early translational work. The company also announced three board appointments: John Beadle representing Eos Advisory, Didier Cowling from Oshen Bio, and Tim Sparey as independent Chair of the Board.
In the announcement, Harry Destecroix, Managing Partner of SCVC, said:
These results mark a major milestone for Scarlet – moving from concept to in vivo validation is a genuine inflection point. Scarlet has the science and the ambition to become a defining company in engineered red blood cells, and we’re proud to continue backing that vision.
In the announcement, Anne Muir, Director of Portfolio at Eos, said:
Scarlet Therapeutics is developing technology that could genuinely change the way we treat a range of serious diseases – this is exactly the kind of first-in-class science, with the potential to transform human health, that we back at Eos. The idea of a universal, scalable red blood cell platform – free from donor dependence and compatibility constraints – is remarkable, and Alistair and his team have the science and vision to make it a reality. We are proud to have led this round and look forward to supporting the next phase of Scarletd’s journey.
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Founder perspective
In the announcement, Alistair Irvine, CEO of Scarlet Therapeutics, said:
Demonstrating that our lab-grown RBCs can mature and circulate in vivo – with a half-life matching donated blood – is a pivotal validation of what we’re building. Our proprietary cell line technology enables scalable, universal RBC manufacturing and opens the door to a new class of durable therapeutics and transfusion products. This financing puts us in a strong position to select our lead therapeutic candidate and move towards the clinic.
Irvine frames the result as a technical validation that supports a move from laboratory research toward selected therapeutic development and regulatory interactions.
The bigger picture
Engineered red blood cells sit at the intersection of cell therapy, biologics manufacturing and transfusion medicine. If clinical trials replicate these preclinical circulation results and demonstrate safety, manufactured universal RBCs could relieve pressure on blood services and offer new delivery modalities for chronic and rare diseases. The RESTORE study and other clinical comparisons will be critical to proving equivalence to donated blood.
The round also signals continued interest from biotech investors in engineered cell platforms that aim to replace donor‑sourced materials with reproducible, scalable products.
Scarlet is based in Bristol within the Science Creates ecosystem. The mix of UK-based development and international investors reflects growing cross-border engagement in biotech funding as companies seek capital, regulatory advice and manufacturing partnerships across Europe and North America.
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