ArsenalBio sheds most of staff in pivot to in vivo CAR-T

Brought to you by: Biotech ArsenalBio sheds most of staff in pivot to in vivo CAR-T By Darren Incorvaia Sep 1, 2026 9:59am Arsenal Biosciences in vivo CAR-T biotech layoffs Cell & Gene Therapy About a year after halving its staff in a clinical push, Arsenal Biosciences is now making a hard pivot, laying off most of its employees and seeking new homes for its assets. ArsenalBio is turning to the red-hot field of in vivo CAR-T therapy, the company announced in a release yesterday. That means saying goodbye to 99 employees, a spokesperson confirmed to Fierce, “representing the majority of the company across all teams, functions, and locations.” As part of the restructuring, all development of the company's ex vivo clinical assets has stopped, the spokesperson added.

After its last big layoff round in September 2025, the biotech was left with 127 workers. “We plan to apply our foundational understanding of T cell biology and compositions to in vivo, where we believe our technology will advance the field and help patients win,” ArsenalBio CEO Ken Drazan, M.D., said in the company’s release. “This decision was not made lightly, knowing the impact on our colleagues who have worked tirelessly to build ArsenalBio.” The downsizing marks another low moment for a biotech that was once a fundraising powerhouse.

ArsenalBio raised $325 million two years ago with the backing of Bristol Myers Squibb and Regeneron, and also boasted a partnership with Roche’s Genentech. ArsenalBio’s goal at the time was to develop CAR-T therapies for solid tumors, an area of notable difficulty. There are currently no approved CAR-T medicines for any solid tumors, only blood cancers.

Last September, the company shed staff to focus its efforts on a phase 1/2 trial of lead asset AB-2100 in recurrent clear-cell renal cell carcinoma. Now, AB-2100 is no longer listed on ArsenalBio’s pipeline, which instead features an early clinical-stage prostate cancer prospect called AB-3028 and preclinical candidate AB-7000. In its release, ArsenalBio said it was launching a hunt for strategic opportunities for its existing technology and assets as it makes the switch to in vivo CAR-T.

ArsenalBio is choosing to enter a crowded arena, with notable in vivo cancer contenders including Eli Lilly, Johnson & Johnson, AstraZeneca and Gilead Sciences’ Kite Pharma. Editor's note: This story was updated at 11:05am E.T. with further information on ArsenalBio's pipeline.

Arsenal Biosciences in vivo CAR-T biotech layoffs Cell & Gene Therapy layoffs strategic review strategic options Biotech