Inclusion Criteria:

• Stiff Person Syndrome or Ataxia or Epilepsy with elevated anti-GAD serum antibody titers > 20 nM/L or CSF antibody titer greater than 0.02 nM/L.
• Ambulatory with or without gait aid (cane, walker).
• Willingness to wean IVIg/IST therapy and symptomatic therapies during final 6 months prior to screening for a phase II trial.
• Patients will be allowed to receive the ongoing non-immunosuppressive drugs used to treat SPS including diazepam, eurontin or baclofen. The dose of these drugs will remain unchanged final 6 months prior to screening for a phase II trial. Willingness and legal ability to give and sign informed study consent.
• Patients with diabetes (Type I) will be allowed to participate because up to 40% of SPS patients have diabetes.
• Concurrent enrollment in IRB#08-007846 with skin punch biopsy and lumbar puncture for research only.

Exclusion Criteria:

• Wheelchair bound.
• Candidates may not be taking prednisone, cyclosporine, tacrolimus, azathioprine, mycophenolate mofetil, anti-lymphocyte agents, cyclophosphamide, methotrexate, or other agents whose therapeutic effect is immunosuppressive in the final 6 month prior to screening for the phase II trial.
• Any medical or social condition that precludes follow-up visits.
• Any history of cardiac insufficiency, major vascular disease, or symptomatic coronary artery disease. Patients with cardiomyopathy grade III or IV by the New York Heart Classification will be excluded from this study. Systemic edema or pulmonary edema.
• Chronic liver disease or alcoholism.
• Any condition, including active infections, that would likely increase the risk of protocol participation or confuse the understanding of the data.
• Pregnancy. Serum pregnancy test will be performed and must be negative in all women of childbearing potential enrolled in the study.
• History of active psychiatric disorder that may interfere with participation in the study.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 8/24/23. Questions regarding updates should be directed to the study team contact.