New research led by the University of Colorado Anschutz is offering hope to people living with stiff person syndrome (SPS), showing that a promising CAR T-cell therapy may help change the course of the disease, with patients experiencing significant improvements in mobility and overall disability that lasted at least one year after treatment.
SPS is a rare, progressive autoimmune neurological disease that causes debilitating muscle stiffness, painful spasms and difficulty walking. An estimated 80% of patients eventually require walking assistance or a wheelchair, and many face a risk of permanent disability.
The phase 2 clinical trial, sponsored by Kyverna Therapeutics and led by principal investigator Amanda Piquet, MD, director of the autoimmune neurology program at the CU Anschutz School of Medicine, evaluated an experimental CAR T-cell therapy called mivocabtagene autoleucel (miv-cel). The one-year findings were presented today at MSToronto26 , an international conference focused on advances in multiple sclerosis and related neurological conditions.
Piquet shared that one year after receiving a single treatment of the experimental therapy, patients with SPS demonstrated significant improvements in mobility, completing a 25-foot walking test in nearly half the time it took before treatment. Also, two-thirds of patients who initially needed walking aids were able to complete a walking test without assistance. Beyond walking improvements, patients also experienced lasting reductions in muscle stiffness, sensitivity to stimuli and overall disability.
“What makes these findings so exciting is that we’re seeing patients regain independence and do things they previously couldn’t do without assistance. For a progressive disease with no approved therapies, these findings represent a major step forward,” said Piquet, who is also the Céline Dion Foundation Endowed Chair in Autoimmune Neurology at CU Anschutz.
The treatment uses a patient's own immune cells, which are modified to target cells involved in the disease. Unlike conventional treatments that often require ongoing medication to manage symptoms and suppress immune activity, this approach aims to address the underlying autoimmune processes driving SPS, potentially offering longer-lasting benefits after a single treatment.
All 26 patients treated in the clinical trial completed the one-year study, allowing researchers to evaluate whether the improvements seen in the first several months continued over time.
The findings from this registrational clinical trial are helping advance miv-cel toward potential FDA approval. Kyverna, the biopharmaceutical company who developed the CAR T-cell therapy, has stated its intention to complete its rolling Biologics License Application (BLA) submission in the fourth quarter of 2026.
If approved, miv-cel could become the first FDA-approved treatment specifically for stiff person syndrome and the first CAR T-cell therapy approved for an autoimmune disease.
“CAR T-cell therapy has the potential to change how we treat autoimmune diseases, offering lasting improvements without the need for ongoing immunotherapy,” Piquet said. “We’re hopeful this could lead to the first FDA-approved treatment for stiff person syndrome and open the door to an entirely new approach to treating autoimmune diseases.”
Key Points:
- A CU Anschutz-led clinical trial found that experimental CAR T-cell therapy produced lasting improvements in patients with stiff person syndrome (SPS).
- Patients completed a 25-foot walking test in a median of nearly half the time it took before treatment.
- Patients experienced greater mobility, reduced muscle stiffness and improved independence.
- At one year, 92% of patients no longer required ongoing immunotherapy to manage SPS.
- The findings could pave the way for the first FDA-approved treatment specifically for stiff person syndrome.