Oxford spinout Alethio raises $90M Series A for chronic blood cancer trials

The Series A was co-led by Sofinnova Partners and RA Capital, alongside founding investor Oxford Science Enterprises, with additional support from Cancer Research Horizons and the University of Oxford.

Backstory: Founded as Alethiomics in late 2021, Alethio brought together two neighboring research groups at Oxford’s MRC Weatherall Institute of Molecular Medicine. Adam Mead studied malignant stem cells, while Beth Psaila investigated megakaryocytes, the platelet-producing cells implicated in bone marrow scarring.

“The starting point was really a clinical one,” Mead and Psaila told European Biotechnology in joint written responses. “We were frustrated that patients with myeloproliferative neoplasms were still largely being treated with medicines that control blood counts without addressing the abnormal cells that sustain the disease, and which can also cause significant side effects.”

Their academic research identified G6B as highly expressed on abnormal stem cells that propagate myeloproliferative neoplasms (MPNs), a group of chronic blood cancers, while absent from healthy blood stem cells. The finding suggested a potential route to selectively target the disease.

“What gave us confidence was the strength and consistency of the validation of G6B as a target,” the founders said. “Across large cohorts of patient samples, we repeatedly saw that G6B selectively marks the disease-driving cells.”

They saw two possible benefits: helping the body remove excess platelets, which contribute to clotting complications, and clearing cancer-driving stem cells while sparing healthy ones.

Essential thrombocythemia (ET), a type of MPN, is characterized by excessive platelet production and can cause clotting, bleeding and, in some patients, progression to myelofibrosis or acute leukemia. Existing treatments include hydroxyurea, interferon and anagrelide. Alethio aims to offer a more selective approach, initially focused on platelet control.

Inside ARTEMIS: ARTEMIS is Alethio’s platform for identifying and validating drug targets on the cells that sustain blood cancers. It draws on what the company describes as one of the largest and best-curated collections of MPN patient samples, combining single-cell analysis, computational methods and laboratory testing to find cell-surface proteins that antibodies could target.

Researchers examine individual cells to connect their mutations with gene activity and the proteins on their surfaces. This helps distinguish cancer-driving cells from healthy ones and reveal potential targets that might be missed when mixed cell populations are analyzed together. Machine-learning methods help prioritize those targets. The team then tests them using independent techniques, including protein measurements, patient-derived bone marrow organoids and animal models, to assess whether targeting them could produce a useful therapeutic effect.

“Only targets that consistently demonstrate therapeutic relevance progress into drug discovery,” CEO Rohit Batta told us.

G6B illustrates how that process works. After the founders identified the protein as a promising target in their academic research, ARTEMIS helped validate and expand those findings. The supporting research analyzed samples from more than 100 MPN patients with CALR or JAK2 mutations, alongside matched healthy donors, strengthening the evidence that G6B marks abnormal stem cells while being absent from healthy blood stem cells.

A change in priorities: When Alethio emerged from stealth under its new name in October 2025, it highlighted two antibody-drug conjugate (ADC) programs, AT-01 and AT-02. The Series A now centers on ATX-011, an antibody without that attached payload.

“The underlying biology remains unchanged; what has evolved is the way we are harnessing it,” Batta said. “AT-01 has since become our G6B-ADC programme for myelofibrosis, while AT-02 evolved into our mutant CALR programme.”

ATX-011 emerged when the team observed that an unconjugated G6B antibody produced controlled, reversible platelet reductions in nonhuman primates (NHP). Antibody exposure tracked the effect on platelet counts, giving the researchers a relationship they could use to guide further development. Combined with the founders’ experience treating ET, those results led Alethio to prioritize ATX-011 as its lead clinical program.

Oxford Science Enterprises (OSE) said that G6B had been central to its investment case from the beginning, with different drug formats intended to address different parts of the MPN disease spectrum.

“For OSE, a huge part of the investment thesis was those unique clinical insights from Adam and Beth that you only get by treating patients regularly,” the investor said in written responses. “When we first saw the NHP data with ATX-011, we knew we had to pursue this programme for patients with ET — it just made scientific sense.”

How it works: G6B is found on platelets and megakaryocytes as well as the abnormal stem cells Alethio hopes to target. Developing an antibody against it therefore required more than demonstrating that the antibody could bind.

The team modified the antibody’s Fc region, which helps recruit immune mechanisms, to reduce unwanted activity while retaining some ability to promote cellular clearance. In laboratory experiments presented at the American Society of
Hematology (ASH) 2026 Annual Meeting, ATX-011 did not directly activate human platelets or cause them to aggregate. It also did not disrupt megakaryocyte maturation in the tested cell model. The researchers concluded that the antibody binds without altering G6B’s normal function.

In a study involving two nonhuman primates, platelet counts fell by 80% after 96 hours and recovered as the antibody cleared. The researchers reported no effect on hemoglobin or white blood cell counts, and no changes in the measured markers of inflammation, platelet activation or disturbed coagulation.

The response suggests that ATX-011 enhances the body’s existing platelet-clearance processes. Modeling based on the primate data predicts that dosing every three to four weeks could maintain normal platelet counts in ET patients, although that remains a prediction to test clinically.

The investor perspective: For the new investors, the human evidence supporting the target was an important part of the financing rationale. “G6B is a highly differentiated target with compelling human data supporting its role in selectively identifying disease-driving cells in MPN,” RA Capital’s Maxwell DeNies said in the financing announcement.

For Sofinnova Partners’ Graziano Seghezzi, the investment case began with the evidence from patient samples. “For us, it was the data,” he told European Biotechnology. “G6B sits on the cells driving the disease but not on healthy stem cells, and Alethio’s founders, Professors Adam Mead and Beth Psaila, have shown this across a large number of patient samples, regardless of mutation.” ATX-011’s preclinical results provided evidence that the target could be drugged, he said, while ARTEMIS offered a route to additional programs.

“The main uncertainty is the one you have with any first-in-class drug: whether the results we see in the lab will translate in patients,” Seghezzi said. “The clinical study will tell us, and Alethio now has the financing to run it.”

Oxford Science Enterprises also pointed to pharmaceutical companies’ interest in MPNs. It said transactions such as Eli Lilly’s acquisition of Ajax Therapeutics, in a deal worth up to $2.3 billion, helped build conviction among new investors during the fundraise.

What’s next: Batta now expects enrollment to begin in the first half of 2028, subject to regulatory processes. The first part of the study will assess safety, the relationship between drug exposure and biological effects, and proof of mechanism through platelet control. “The second part will assess the depth and durability of response, including platelet normalisation at 12 weeks as an early proof-of-concept readout, alongside molecular and clonal biomarkers,” Batta said.

Those additional measurements could help assess effects on the abnormal cell populations underlying the disease. Platelet normalization alone would not establish that the treatment changes its course.

Batta said there is precedent in ET for moving directly into patient studies and progressing rapidly from proof of concept to registrational Phase 3 trials. Alethio must first establish whether the controlled platelet reductions that changed its development priorities can translate into a useful treatment for patients.