Kyverna to submit BLA for investigational CAR-T therapy for stiff-person syndrome

An investigational CAR-T cell therapy for the treatment of stiff-person syndrome led to symptom improvement in 81% of patients after four months of treatment, according to the results of a recent clinical trial released by drug developer Kyverna Therapeutics.

Kyverna plans to submit a Biologics License Application to the FDA called mivocabtagene autoleucel (miv-cel) in the first half of 2026, a news release states. If accepted, it would be the first FDA-approved CAR-T cell therapy for autoimmune disease.

Stiff-person syndrome is a rare, progressive neurological autoimmune disorder that affects approximately one in one million people. It is characterized by muscle stiffness, rigidity and painful spasms, which can be triggered by noise, touch or emotional distress.

Approximately 80% of patients lose mobility. Other long-term complications can include falls and isolation because of the fear that street noises, such as car horns, could trigger spasms. In 2022, recording artist Celine Dion revealed she has stiff-person syndrome, which increased disease awareness.

“I’m excited to see this trial bring to light a highly debilitating neurologic autoimmune disease that impacts 6,000 patients in the U.S.,” Amanda Piquet, M.D., Director of Autoimmune Neurology, University of Colorado Anschutz School of Medicine, Céline Dion Foundation Endowed Chair, and lead investigator of the KYSA-8 trial, said in the news release. “Patients with SPS often rely on burdensome, chronic treatments with significant side effects, and the majority still face progressive disease that can lead to loss of independence, diminished quality of life, and, in some cases, permanent disability. For these reasons, miv-cel’s ability to significantly improve mobility and reduce stiffness is both remarkable and unprecedented, bringing hope to patients and their families who deserve better treatment options.”

Miv-cel is a fully human autologous CD19-targeting CAR-T therapy. During KYSA-8, a total of 26 adult patients were given a single dose of miv-cel and followed through week 16. The primary endpoint was a significant improvement in a Timed 25-Foot Walk score, in which a patient must walk 25 feet as quickly and as safely as possible. This test is also commonly used to assess disability in multiple sclerosis patients.

Almost all (81%) of patients exceeded a 20% improvement, which is clinically meaningful. Almost half (46%) had a median 46% improvement from the trial’s start. More than half (67%) of the 12 patients that required a walking aid device prior to treatment no longer needed assistance at week 16.

Additionally, no patients required immunotherapies during the trial and there were no observed instances of high-grade cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome, which can be a complication of CAR-T therapies.

“We believe these unprecedented results, which support our BLA submission, will have a profound impact on patients,” Naji Gehchan, Chief Medical and Development Officer of Kyverna Therapeutics, also said in the news release. “We want to thank the patients, their families and the healthcare providers for participating in this important trial.”