Novartis and Bristol Myers pause autoimmune CAR-T trials due to safety concerns

Novartis and Bristol Myers Squibb have paused clinical trials of their respective autoimmune CAR-T therapies, rap-cel and zola-cel, due to safety concerns. Novartis halted its trials on August 24, 2026, after detecting three cases of a rare, life-threatening inflammatory reaction called IEC-HS. Bristol Myers Squibb voluntarily paused enrollment to review transient inflammatory events. Both therapies use accelerated manufacturing technology, which analysts suggest may drive cell expansion and toxicity.

CAR-T autoimmune trial pauses

• ▪Novartis paused multiple clinical trials evaluating its CAR-T cell therapy rap-cel in autoimmune conditions on August 24, 2026
• ▪Novartis is testing its CAR-T cell therapy rap-cel in eight different immunology and neuroscience indications, while its cancer trials for rap-cel remain ongoing
• ▪Bristol Myers Squibb voluntarily paused enrollment in clinical trials evaluating its CAR-T therapy zolacabtagene autoleucel (zola-cel) for autoimmune conditions
• ▪Bristol Myers Squibb was scheduled to begin a clinical trial of its CAR-T therapy zolacabtagene autoleucel (zola-cel) in patients with systemic sclerosis in August 2026

IEC-HS inflammatory side effects

• ▪Novartis paused its rap-cel trials after detecting three cases of immune effector cell-associated hemophagocytic syndrome (IEC-HS), a rare and potentially life-threatening reaction
• ▪Results published in February 2026 detailed one case of immune effector cell-associated hemophagocytic syndrome (IEC-HS) in a Phase 1 study of Bristol Myers Squibb's zolacabtagene autoleucel (zola-cel)
• ▪Bristol Myers Squibb paused enrollment in its zolacabtagene autoleucel (zola-cel) trials after detecting transient and reversible inflammatory events during routine safety surveillance

Accelerated CAR-T manufacturing technology

• ▪William Blair analyst Sami Corwin stated that the accelerated manufacturing technology could drive increased cell expansion and the reported toxicities, though other factors may be involved
• ▪Both Novartis's rap-cel and Bristol Myers Squibb's zolacabtagene autoleucel (zola-cel) utilize technology designed to accelerate production compared to earlier CAR-T products

Regulatory safety data review

• ▪Bristol Myers Squibb stated its voluntary pause was enacted out of an abundance of caution to review clinical data, with plans to resume testing as quickly as possible
• ▪Novartis is reviewing clinical findings and engaging with regulators during the temporary halt of its rap-cel trials to allow a comprehensive review of safety data

Competing autoimmune CAR-T programs

• ▪Kyverna Therapeutics is enrolling patients in a pivotal study for myasthenia gravis and could submit an approval application in stiff person syndrome by the end of 2026
• ▪Cabaletta Bio has multiple clinical trials underway for CAR-T therapies in autoimmune conditions, including a late-stage study in myositis

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