The $83M Bet on Your Body's Forgotten Immune Cells
A London startup just raised $83 million to weaponize your body's most overlooked immune cells against cancer. Cytospire's "pan-gamma delta" approach bets that the quiet, tissue-dwelling T cells nobody talks about might outperform the famous ones that power today's immunotherapies.
The Immune System Has a B-Team. Someone Just Bet Big on It.
Your immune system has celebrity fighters: the killer T cells that oncologists have spent decades training to attack tumors. They're the alpha beta T cells, and they've powered blockbuster cancer drugs from Blincyto to teclistamab. They get all the attention.
But lurking in your tissues, quietly patrolling your gut lining and skin, is a lesser-known squad called gamma delta T cells. They make up just 1-5% of your circulating T cells, but they punch above their weight. They don't need the usual ID badge (called MHC presentation) to recognize a cancer cell. They just know when something's wrong. Think of them as bouncers who spot trouble by vibe, not by checking the guest list.
Now a London-based startup called Cytospire Therapeutics just raised $83 million to build weapons that unleash these cells against tumors. It's the largest Series A in the gamma delta space, and it signals that investors think the B-team might actually be the better team.
What Cytospire Is Actually Building
Cytospire is developing what they call "pan-gamma delta T cell engagers." Let's unpack that.
T cell engagers are bispecific antibodies: Y-shaped molecules with one arm that grabs a cancer cell and another arm that grabs an immune cell, forcing them together like an aggressive matchmaker. Existing engagers grab alpha beta T cells by their CD3 receptor. It works, but it comes with baggage. Cytokine release syndrome (basically an immune system meltdown), neurotoxicity, and poor performance in solid tumors are all common headaches.
Cytospire's twist: instead of grabbing alpha beta T cells, their engagers grab all subtypes of gamma delta T cells (Vδ1, Vδ2, Vδ3, the whole family). That's the "pan" part. And the lead candidate, CYT X300, connects these gamma delta cells to EGFR-positive cancer cells found in colorectal, head and neck, and non-small cell lung cancers.
CEO Natalie Mount put it plainly: "Immune cell engagers are an important type of cancer immunotherapy, but we know that there are significant limitations... Our pan-gamma delta T cell engagers are an exciting, differentiated modality."
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Why Go After Gamma Delta? The Case for the Underdogs.
The logic is surprisingly intuitive. Most existing T cell engagers recruit alpha beta T cells from the bloodstream and hope they infiltrate the tumor. That's like trying to Uber soldiers into a warzone; getting them there is half the battle.
Gamma delta T cells are already inside the tumor. They're tissue-resident, meaning they naturally hang out in epithelial layers where many solid cancers grow. They're already on the battlefield. You just need to hand them a weapon.
Beyond location, gamma delta cells have another trick: they're better at telling friend from foe. Scientists call it "normality sensing." These cells naturally spare healthy tissue while targeting stressed or abnormal cells. That translates to fewer side effects, less collateral damage, and potentially none of the cytokine storms that plague conventional engagers.
For solid tumors specifically (colorectal, lung, head and neck), the alpha beta T cell approach has been frustrating. Those tumors create immunosuppressive environments that exhaust conventional T cells. Gamma delta cells, with their innate-like properties, appear more resistant to that exhaustion.
The Money and Who's Behind It
The $83 million (£61 million) Series A was oversubscribed, which in VC-speak means more investors wanted in than could fit. That's a vote of confidence, especially in a biotech funding environment that's been tighter than a closed fist since 2022.
4BIO Capital led the round. But the most interesting name on the cap table might be Servier Ventures, which made this its very first investment from a new corporate venture fund. When a pharma company's VC arm picks you as their debut bet, that says something about conviction.
Other participants included Sound Bioventures, British Business Bank, Criteria Bio Ventures, and existing backers Abingworth and LifeArc Ventures. Abingworth is notable as the founding investor in Cytospire, and their Global Head of Life Sciences and CIO Bali Muralidhar sits on the board.
The money will fund IND-enabling studies (the preclinical work needed to file for human trials), GMP manufacturing, and a first-in-human clinical trial for CYT X300.
A Team That's Done This Before
Cytospire's leadership roster reads like a reunion tour of gamma delta T cell companies that already got acquired.
CEO Natalie Mount previously ran Adaptate Biotherapeutics (bought by Takeda in 2022). Before that, she spent 16 years at Pfizer leading their cell therapy portfolio. CTO Mark Uden came from Adaptate too, after 17 years at GSK. Head of Biology Robert Good was founding R&D at Adaptate.
This is a team that built gamma delta platforms, sold them to a $70 billion pharma company, and came back to do it differently. The fact that Takeda later wrote off ¥58 billion on its gamma delta platform (reported October 2025) adds an interesting wrinkle: Cytospire's engager approach is fundamentally different from the cell therapy strategy that Takeda struggled with.
The Competitive Landscape: Small but Heating Up
Cytospire isn't alone in the gamma delta space, but the field is still early.
Lava Therapeutics has LAVA-051, a gamma delta engager targeting CD1d-positive blood cancers, currently in Phase 1. They've shown tumor infiltration data and plan Phase 1b combination studies. IN8bio is developing its DeltEx platform combining gamma delta expansion with engager approaches.
The broader market tells a story of growing momentum. Over 25 gamma delta T cell therapies are currently in clinical trials worldwide. Market projections for the gamma delta therapy sector range from $2.1 billion by 2030 to $5.5 billion by 2033, depending on which analyst you ask.
But no gamma delta T cell engager has been approved yet. Zero. This is still a field of potential, not proven winners.
The Challenge: Can It Actually Work in Patients?
Gamma delta therapies have a history of beautiful preclinical data that gets humbled by clinical reality. The problems are well-documented: poor trafficking to tumors, rapid exhaustion, manufacturing inconsistency, and the simple challenge of getting enough effector cells into the right place.
Cytospire's "pan" approach is designed to solve at least one of those problems. Previous gamma delta therapies mostly targeted just Vδ2 cells (the main circulating subtype), which are scarce in some patients and exhaustion-prone. By engaging all subtypes, including the Vδ1 cells already resident in tumors, Cytospire theoretically accesses a much larger army. It's the difference between calling one friend for help versus texting the entire group chat.
The engager format also sidesteps manufacturing headaches that plague cell therapies. Instead of extracting, expanding, and reinfusing cells (expensive, slow, variable), you just infuse an antibody that activates cells already in the patient. It's an off-the-shelf approach without needing off-the-shelf cells.
Still, the fundamental question remains unanswered: will activating gamma delta T cells in patients actually shrink tumors? The first-in-human trial will start answering that question, likely in 2026 or 2027.
Why This Matters Beyond Cytospire
This raise is a signal flare for the entire innate immune oncology space. While most cancer immunotherapy dollars have chased alpha beta T cells (CAR-T, bispecifics, checkpoint inhibitors), $83 million for a preclinical gamma delta platform suggests the market is diversifying its bets.
In a challenging cell therapy funding environment, Cytospire's oversubscribed round stands out.
If CYT X300 shows even modest efficacy in solid tumors with a clean safety profile, it could validate an entirely new class of cancer immunotherapy. And if it doesn't, well, at least we'll know more about whether the immune system's quiet professionals can be turned into effective assassins.
The B-team is suiting up. Now we wait to see if they can play.
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