After downsizing by 50% last year, Arsenal Biosciences is again laying off employees. This time, 99 people are getting cut as part of a strategic shift to focus the company’s R&D efforts on in vivo CAR T therapies.
Arsenal Biosciences is implementing a “significant strategic shift” to focus efforts on the development of in vivo CAR T therapies—a process that will involve a dramatic reduction in the company’s workforce.
Ninety-nine employees will lose their jobs, a spokesperson for ArsenalBio confirmed to BioSpace via email on Monday evening. This number represents “the majority of the company across all teams, functions, and locations.” As of September 2025, ArsenalBio had 127 employees after downsizing by 50%.
BioSpace has reached out to the biotech to ask how many employees will be left at the company after the latest round of layoffs.
As part of the shift, announced Monday, ArsenalBio will be left with “a core team” of people who will work to advance the in vivo strategy, while also looking for strategic alternatives for the company’s assets and technologies.
ArsenalBio’s previous lead asset was called AB-2100, an autologous integrated circuit cell therapy in early-stage development for renal cell carcinoma. Topline data were expected to read out in March, but no disclosures have been made as of yet. ArsenalBio raised $325 million in series C money in September 2024 to support the development AB-2100. The biotech also had a Phase 1 study for a candidate called AB-1015.
While still categorized as active but not recruiting on clinicaltrials.gov, both of these assets have been dropped from ArsenalBio’s pipeline page. Instead, the biotech’s most mature candidate is AB-3028, which according to the company’s website uses a similar approach as AB-2100 and AB-1015 and is currently in early clinical development for prostate cancer. ArsenalBio is also advancing a program called AB-7000 for an undisclosed indication.
In late 2020, ArsenalBio partnered with Bristol Myers Squibb to advance programmable cell therapies for cancer indications. That deal involved an upfront payment of $70 million and undisclosed milestones, one tranche of which was paid out in January 2025 after the pharma exercised an exclusive option to license one program.
It is unclear what the strategic shift will mean for the BMS partnership.
