Alethio Therapeutics raises $90M Series A for mutation-agnostic blood cancer antibody

Alethio Therapeutics (Oxford) has closed a $90 million (€80.5M) Series A to advance ATX-011 — its first-in-class G6B-targeting antibody for essential thrombocythemia — toward clinical trials. The round was co-led by Sofinnova Partners and RA Capital Management, both new investors, with Oxford Science Enterprises, Cancer Research Horizons, and the University of Oxford participating. The oversubscribed close, announced 5 November, is one of the larger European biotech Series A rounds of the autumn.

The target: G6B in blood cancers

Essential thrombocythemia (ET) is the most common myeloproliferative neoplasm (MPN), a family of blood cancers defined by the abnormal overproduction of blood cells. Current treatments — primarily hydroxyurea and JAK inhibitors — manage symptoms but do not eliminate the underlying clonal disorder; most patients face lifelong therapy with modest, incremental improvement.

Alethio, founded in 2024 as an Oxford spinout, is working on G6B, a platelet-inhibitory receptor whose agonism suppresses abnormal megakaryocyte proliferation. ATX-011 is an antibody designed to activate G6B independent of the JAK2, MPL, or CALR mutations that drive ET — which means, if the biology holds, it could treat the full patient population rather than a genetically defined subset. The company is currently pre-clinical and targets an IND filing as the first use of this capital.

Sofinnova, RA Capital, and the Oxford pipeline

Sofinnova Partners arrives at Alethio with established footing in European biotech: the firm co-led Bionyra's €143M Series A earlier this year, backing a Paris-based inflammatory disease programme from pre-clinical through clinical transition. RA Capital, the Boston-based life sciences investor, provides the US connection and a track record of backing both European and American programmes through clinical development.

Oxford Science Enterprises and Cancer Research Horizons — both early-stage backers from seed — carry forward, suggesting the science has held up through internal diligence. That continuity matters: seed-to-Series A rollover is not guaranteed in biotech, and both organisations have enough pipeline exposure to exercise their option deliberately.

Why it matters

Alethio is raising a large Series A on pre-clinical data alone — standard in oncology, but it concentrates the bet. The case for G6B is compelling on paper: a mutation-agnostic approach that suppresses the clonal driver rather than managing its consequences would be a step-change in ET treatment. The 18-month test is IND clearance. If ATX-011 enters a Phase 1 trial without safety signals that force a dose redesign, the €80.5M buys a Series B on credible clinical momentum. If the safety profile is complicated — G6B is expressed broadly in platelets and megakaryocytes — the thesis narrows fast.