Based in the United Kingdom, Cytospire Therapeutics is developing antibody-based immune cell engagers with potentially improved response in cancer patients. It’s the kind of paradigm-shifting medicine that CEO Natalie Mount has been drawn to throughout her career.

With a biochemistry degree from Cambridge and a PhD from University College London, Mount started in research and development at Pfizer. She spent 16 years at the pharmaceutical giant, including helping to set up the company’s cell and gene therapy unit, Pfizer Regenerative Medicine. 

“We had a lot of opportunities to explore things differently and take very novel approaches. And that really got me excited about the kind of transformational medicines that you can develop in a very innovative way,” says Mount.

In 2011, her interest in cell and gene therapy led her to leave big pharma for a succession of founding management roles in biotech startups. Mount’s first time as CEO was at Adaptate Biotherapeutics, which also marked a pivot to developing antibody-based engager approaches for oncology.

“I’ve gone from always being the only woman in the boardroom and the only woman in senior management to now having lots of friends who are women CEOs.”

Developing new cancer therapies has been frequent throughout Mount’s biotech career. In fact, at the 2025 Cancer Research Horizons Innovation and Entrepreneurship Awards – an annual event organized by Cancer Research UK – she won the Woman Entrepreneur of the Year award.

“It was obviously great to win the award, but also to reflect on how we’ve seen huge change and progress in terms of women being in leadership positions,” says Mount. “I’ve gone from always being the only woman in the boardroom and the only woman in senior management to now having lots of friends who are women CEOs.”

And while it was in recognition of Mount’s previous achievements, the award was also for her current work with Cytospire.

A different take on immune-based oncology

Mount led Adaptate Biotherapeutics from its founding in 2019 to its 2022 acquisition by the Japanese pharmaceutical giant Takeda, but soon gravitated back to antibody-based engager therapies. In 2023, she started talking about another project with both Adaptate’s former CTO and board chair.

“The three of us came up with ideas on new ways to really enhance the immune response to cancer,” says Mount. “And those ideas came together in the foundation of Cytospire.”

Currently based at the Kadans Canary Wharf London Innovation Centre with 18 employees, Cytospire Therapeutics is preparing the first of its immune cell engagers to enter the clinical phase of development.

Most immune cell engagers for cancer use CD3-based antibodies that broadly activate all T cells and direct them to target a specific antigen, like the tumor-expressed epidermal growth factor receptor (EGFR). This approach not only targets both exhausted and immunosuppressive T cells but also often causes cytokines to be released at a toxic level and T cells to attack healthy, non-tumor cells expressing EGFR.

Cytospire’s platform instead engages a specific subset of immune cells known as gamma-delta T cells. Gamma delta T cells can discriminate between tumor cells and healthy cells expressing the same antigen using a mix of innate and adaptive immune response receptors to detect stress ligands expressed on the cancer cell surface. In this way, healthy tissue is spared, there’s less of a cytokine release, and a more targeted and long-lasting immune response to cancer cells.

“We only activate the immune effector cells, the ones that can kill the tumor cells,” she explains. “So we have an approach which brings potentially much better potency, but also much better safety.”

Next year, clinical trials will begin for Cytospire’s lead asset, CYT-X300, an immune engager targeting EGFR-positive solid tumors, like those associated with colorectal and non-small cell lung cancer. And there’s a whole pipeline of pan-gamma-delta T-cell engagers being developed to help cancer patients who haven’t responded to conventional treatments such as surgery, chemotherapy, or radiotherapy.

“These are patients for whom those approaches are not enough, and their tumor is still there and still growing,” says Mount. “That’s where we come in, activating their immune system to try and clear the cancer and provide long-lasting responses for them.

The right kind of investment partner

In early May of 2026, Cytospire Therapeutics announced the closing of its series A financing round at £61 million ($83 million). The funds will be used for CYT X300’s preclinical studies, manufacturing and first-in-human trial, as well as to accelerate Cytospire’s entire pipeline. Sound Bioventures was among the syndicate of investors and will have a seat on the board.

“They were very much focused on understanding the science,” says Mount. “They run a really great diligence process, very thorough, really wanting to understand the details, and asking good questions in a focused way.

For Mount, Sound Bioventures is the right kind of investor for Cytospire. One that truly understands what it takes to develop novel therapies, including the essential as well as subtle questions that clinical studies need to answer. More importantly, Sound Bioventures and Cytospire align in values and vision for collaborating on novel therapies to address unmet needs.

“This is actually, I think, a really exciting time in terms of new innovation in oncology therapies,” she says. “And that’s driven by advances in the science and great teams who work together to really deliver.”

Want to find more companies and CEOs like this? Read some of the profiles from the Sound Bioventures portfolio.