Briggs Morrison's Crossbow unveils $77M Series B for T cell engagers

Veteran drug developer Briggs Morrison takes another shot at the clinic — with $77M and T cell engagers in tow

Crossbow Therapeutics has raised a $77 million Series B round to push two T cell engager programs into and through clinical trials, the company announced Wednesday. CEO Briggs Morrison — a longtime hand in pharmaceutical development who previously ran Syndax Pharmaceuticals — described the strategy in characteristically blunt terms: "Always be in the clinic."

The ABCs of biotech, he calls it.

Crossbow's two lead programs are CBX-250 and CBX-663 — both bispecific T cell engagers designed to redirect a patient's immune cells to attack cancer. T cell engagers work by binding simultaneously to a tumor cell and to a T cell, bringing them into close proximity so the immune system can kill the cancer. The field has grown rapidly since the first bispecific antibodies gained regulatory approval, with companies now racing to improve on the original designs by selecting better target antigens, engineering conditional activation, and trying to manage the cytokine release syndrome that remains a significant toxicity concern with the modality.

The $77 million Series B will fund IND-enabling work and early clinical studies for both programs. Morrison did not disclose the specific cancer indications the company is targeting, the anticipated trial timelines, or which programs will enter the clinic first.

Crossbow was founded with a focus on what Morrison has called "conditionally active" T cell engagers — a design principle intended to focus the therapy's activity where it's needed most and reduce off-target effects. The concept has attracted attention as the broader bispecific T cell engager field matures and companies look for ways to expand beyond the hematologic malignancy settings where the first generation of these drugs found success, into solid tumors where the immunosuppressive tumor microenvironment creates new challenges.

Morrison's track record is a significant part of the story. At Syndax, he led the development of several pipeline programs from early clinical stages through partnerships and acquisitions. His return to the T cell engager space — where he spent earlier parts of his career at companies including MedImmune — reflects a bet that the next generation of these molecules can overcome the tolerability and efficacy ceiling that has limited the first generation.

The Series B was led by an undisclosed syndicate of institutional investors. Crossbow had previously raised a seed round; this is the company's first disclosed Series B.