A $77 Million Bet on Unlocking Cancer's Hidden Targets

Cambridge-based Crossbow Therapeutics has closed a $77 million Series B round to advance its pipeline of TCR-mimetic antibody therapies — a novel class of T-cell engagers (TCEs) that can reach intracellular cancer proteins conventional antibodies simply cannot touch. The round, co-led by Taiho Ventures and Arkin Bio Capital, brings total funding to $157 million and sets the stage for two critical clinical milestones in 2026.

The financing arrives at a pivotal moment for the immuno-oncology space. While approved T-cell engagers like Amgen's blinatumomab and the expanding CAR-T therapy market have demonstrated the power of redirecting T cells against cancer, both modalities remain fundamentally limited to extracellular surface targets. Crossbow's platform promises to shatter that ceiling — and investors from Big Pharma to mission-driven venture philanthropy organizations are lining up to back the thesis.

The Company: From MPM BioImpact Incubation to Clinical Stage

Crossbow was founded in 2021 by Patrick Baeuerle, Ph.D. — widely recognized as a pioneer of the BiTE (bispecific T-cell engager) technology — along with Todd Foley, Managing Director of MPM BioImpact, and Geraldine Paulus, Ph.D., who now serves as Vice President of Corporate Development and Operations. The company was seeded and incubated within MPM BioImpact before launching publicly in July 2023 with an $80 million Series A led by MPM BioImpact and Pfizer Ventures.

At the helm is CEO Briggs Morrison, M.D., a veteran pharmaceutical executive with over 30 years of experience spanning leadership roles at Syndax Pharmaceuticals, AstraZeneca, Pfizer, and Merck. Chief Scientific Officer Dmitri Wiederschain brings deep drug discovery expertise from prior positions at Jounce Therapeutics, Sanofi, and Novartis.

"Our revolutionary T-Bolt™ products strike cancer cells like a crossbow shoots bolts," Morrison has said, describing the company's ambition with characteristic directness.

The T-Bolt™ Platform: How TCR-Mimetic Antibodies Work

The core innovation behind Crossbow lies in its proprietary T-Bolt™ platform, which generates antibodies that mimic T-cell receptors (TCRs). Here's why that matters.

Traditional therapeutic antibodies bind to proteins expressed on the surface of cancer cells. But the vast majority of cancer-associated proteins — the ones driving tumor growth, evading immune surveillance, and conferring drug resistance — reside inside the cell, invisible to conventional antibodies.

T cells naturally solve this problem. Through the MHC/HLA antigen presentation pathway, fragments (peptides) of intracellular proteins are displayed on the cell surface bound to HLA molecules, forming peptide-HLA (pHLA) complexes. T cells recognize these complexes through their T-cell receptors. Crossbow's TCR-mimetic antibodies replicate this recognition ability in an antibody format, creating off-the-shelf, modular T-cell engagers that can be directed at virtually any intracellular cancer protein.

The advantages over CAR-T are significant: no patient-specific manufacturing, no cell collection, no lymphodepletion conditioning — just an infusible biologic. And compared to traditional BiTEs, TCR-mimetic antibodies can access a vastly expanded target space. Research has shown TCR-mimetic antibodies achieve 10 to 100 times higher sensitivity than CARs when targeting intracellular proteins like p53.

The Pipeline: Two First-in-Class Programs

CBX-250 — Targeting Myeloid Malignancies

Crossbow's lead candidate, CBX-250, is a first-in-class TCE that targets a cathepsin G-derived pHLA complex abundantly expressed on leukemic cells but not on normal cells. The CROSSCHECK-001 Phase 1 clinical trial is currently enrolling patients with relapsed or refractory myeloid malignancies, including:

• Acute myeloid leukemia (AML)
• Chronic myeloid leukemia (CML)
• Myelodysplastic syndromes (MDS)
• Chronic myelomonocytic leukemia (CMML)

Initial clinical data from CROSSCHECK-001 are expected by the end of 2026 — a critical readout that will serve as the first clinical validation of the entire T-Bolt™ platform.

CBX-663 — The Telomerase Play

The Series B's marquee story is CBX-663, a first-in-class TCE targeting a telomerase reverse transcriptase (TERT)-derived pHLA. TERT is a protein that drives tumor growth and is expressed in an estimated 95% of all cancers, making it one of the most broadly applicable targets in oncology — yet it has remained undruggable by conventional approaches because it's an intracellular protein.

CBX-663 aims to change that. By targeting a TERT-derived peptide presented on HLA, Crossbow can potentially address both hematologic and solid tumors with a single therapeutic. The IND application is planned for spring 2026, with Phase 1 trial initiation projected for Q3 2026. Preclinical data characterizing CBX-663 in solid tumor models will be presented at the AACR 2026 Annual Meeting.

The Investor Syndicate: Big Pharma Doubles Down

The composition of this round tells a compelling story about market confidence.

Co-leads:

• Taiho Ventures — the CVC arm of Japan's Taiho Pharmaceutical, an oncology-focused pharma company. Taiho Ventures has averaged $73.9M per Series B investment, suggesting this round aligns squarely with their sweet spot.
• Arkin Bio Capital — a leading global life sciences VC that closed the $100M Arkin Bio Ventures III fund in January 2026, focused on pre-clinical to early clinical-stage biotech.

New investors: Sixty Degree Capital, Hamilton Square Partners Management LP, LifeLink Ventures, Libbs Ventures, and Blood Cancer United's Therapy Acceleration Program® (TAP) — a mission-driven venture philanthropy initiative that has supported five FDA-approved therapies since 2017, screening 80-100 biotech companies annually.

Returning investors: MPM BioImpact, Pfizer Ventures, BVF Partners, Polaris Partners, Eli Lilly and Company, and Mirae Asset Venture Investment.

The continued participation of two of the world's largest pharmaceutical companies — Pfizer and Eli Lilly — signals more than financial conviction. It keeps both companies in a privileged position for potential future licensing deals or acquisitions if clinical data prove out.

New board members Sakae Asanuma (Taiho Ventures CEO) and Pini Orbach (Arkin Bio Capital Managing Partner) join the board, adding strategic depth from both the Japanese pharmaceutical and global VC ecosystems.

"Crossbow's T-cell engagers represent a differentiated approach by addressing intracellular targets and broadening TCE modality potential," Asanuma noted.

Market Context: The TCE Landscape Is Exploding

Crossbow is entering a rapidly expanding market. The global T-cell engager market was valued at approximately $2.5 billion in 2025 and is projected to reach $18.8 billion by 2034, growing at a CAGR of 21-31%. The adjacent CAR-T market is forecast to hit $13.78 billion by 2031.

The BiTE segment currently dominates, driven by blinatumomab's first-mover advantage. But the field is evolving rapidly, with next-generation designs incorporating trispecificity, extended half-lives, and novel immunomodulatory mechanisms.

Crossbow's TCR-mimetic approach occupies a distinct niche. Rather than competing head-to-head with existing BiTEs or CAR-Ts on the same surface targets (CD19, BCMA, etc.), the company is opening an entirely new target space — intracellular proteins presented via HLA. This positions Crossbow as complementary rather than competitive to existing modalities, potentially expanding the total addressable patient population dramatically.

The competitive moat is further strengthened by the technical complexity of generating high-quality TCR-mimetic antibodies with sufficient specificity and affinity — a barrier that has historically limited the field.

Strategic Outlook: Catalysts Ahead

The $77 million will fund three strategic priorities:

1. Completing the CROSSCHECK-001 Phase 1 trial for CBX-250, with initial data expected late 2026
2. Filing the IND and launching Phase 1 for CBX-663, the TERT-targeting program, in Q3 2026
3. Advancing additional T-Bolt™ candidates leveraging the platform's modular design

The end-of-2026 data readout for CBX-250 will be the single most important catalyst for the company. Positive safety and early efficacy signals would validate not just one drug, but the entire TCR-mimetic TCE platform — potentially unlocking significantly larger financing rounds or strategic partnerships.

Meanwhile, CBX-663's entry into the clinic targeting TERT — a protein found in 95% of cancers — could position Crossbow as one of the most broadly applicable immunotherapy platforms in oncology, a narrative that would resonate powerfully with both crossover investors and potential pharma acquirers.

Key Takeaways

Crossbow's $77M Series B represents a strong validation of TCR-mimetic antibodies as a next-generation immunotherapy modality. With $157 million in total funding, a platform that unlocks intracellular cancer targets, two first-in-class clinical programs, backing from Pfizer and Lilly, and a founding team that includes a BiTE technology pioneer, Crossbow is positioned at the intersection of scientific innovation and commercial opportunity. The critical question now is clinical execution — and with data readouts and a new IND filing both expected in 2026, investors won't have to wait long for answers.

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Sources:

• Crossbow Therapeutics Series B Press Release — BusinessWire
• Crossbow Series A Launch — GlobeNewsWire
• BioPharma Dive — Crossbow Raises $77M
• Fierce Biotech — Crossbow Series B
• Arkin Capital Closes $100M Bio Ventures III
• Blood Cancer United TAP Program
• CBX-663 Nomination — BusinessWire
• TCR Mimic Antibodies in Cancer Therapy — PMC
• T-Cell Engager Market — Custom Market Insights