KYSA-8: A Study of Anti-CD19 Chimeric Antigen Receptor T-Cell (CD19 CAR T) Therapy, in Subjects With Treatment Refractory Stiff Person Syndrome

Key Inclusion Criteria: * Subject must have been diagnosed SPS per the following criteria: * Rigidity of limb and axial (trunk) muscles prominent in the abdominal and thoracolumbar paraspinal areas and making bending difficult * Clinical or electrophysiological evidence of continuous contraction of agonist and antagonist muscles * Episodic spasms precipitated by unexpected noises, tactile stimuli, or emotional upset * Absence of any other neurologic disease that could explain the stiffness and rigidity * High titer serum anti-GAD65 antibodies shown at screening -OR- seropositive for anti-glycine antibodies. If anti-GAD65 antibodies are lower than the high titer threshold peripherally but positive in the cerebrospinal fluid (CSF), the subject can be included. A prior documented high titer anti-GAD65 antibody level may be acceptable subject to sponsor review. * Active symptoms with inadequate response to at least one immunomodulatory therapy. * Stiffness index ≥2. * At least 20 of the 25 enrolled subjects should be ambulatory. Key Exclusion Criteria: * Bedridden subjects for more than 3 months. * History of CNS or spinal cord tumor, metabolic or infectious cause of myelopathy, genetically inherited progressive CNS disorder, sarcoidosis, non-SPS progressive neurologic condition or progressive multifocal leukoencephalopathy (PML). * History of stroke, seizure, dementia, Parkinson's disease, cerebellar diseases, psychosis, aphasia, and any other neurologic disorder that is of a nature and severity that the investigator considers would increase the risk for the subject. * Cardiac ejection fraction ≤ 40%.