Cytospire raises GBP 61m via Series A for gamma delta T-cell engagers

Cytospire Therapeutics, a UK-based biotech developing multispecific immune cell engager antibodies, has closed an oversubscribed Series A financing round of GBP 61 million (USD 83 million) to advance its pipeline of pan-gamma delta T-cell engagers into clinical development.

The round was led by 4BIO Capital, with participation from new investors Servier Ventures, Sound Bioventures, British Business Bank, Criteria Bio Ventures, Modi Ventures, Medical Incubator Japan, and Pathway Bioventures. Existing backers Abingworth, which originally seeded the company at founding in 2023, and LifeArc Ventures also participated. The seed round amount was not publicly disclosed. Cytospire said proceeds will be used to advance its pipeline in solid and hematologic malignancies, with a primary focus on progressing its lead candidate, CYT X300, through IND-enabling preclinical studies and GMP manufacturing toward a first-in-human clinical study.

CYT X300 is a pan-gamma delta T-cell engager targeting EGFR, designed for EGFR-positive solid tumors including colorectal cancer, head and neck cancer, and non-small cell lung cancer. No clinical trial registration for CYT X300 has been publicly filed to date. Cytospire's broader platform, described in a 2025 AACR abstract, is built around multispecific engager antibodies that simultaneously bind a tumor-associated antigen and a pan-gamma delta T-cell receptor sequence shared across all gamma delta T-cell subsets, forcing an immunological synapse between effector cells and tumor cells.

The scientific rationale for the platform centers on properties of gamma delta T cells that distinguish them from the conventional alpha beta T cells targeted by existing approved engager therapies. Unlike alpha beta T cells, gamma delta T cells kill tumor cells independently of HLA antigen presentation, a mechanism tumors frequently evade by downregulating surface HLA expression. Gamma delta T cells also reside within the tumor microenvironment, a characteristic the company argues gives them a functional advantage over circulating effectors in solid tumor settings, where conventional T-cell engagers have shown limited activity. Cytospire's pan-subset targeting approach is designed to engage both tissue-resident and blood-resident gamma delta T-cell populations simultaneously, addressing a limitation of earlier approaches that focused on only one gamma delta T-cell subtype.

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