The purpose of this study is to evaluate the efficacy and safety of QIVIGY (Intravenous Human Normal Immune Globulin 10%) compared with placebo in adult participants with stiff person syndrome (SPS).
Male or female, 18-70 years of age.
Patient has signed the Informed Consent Form (ICF).
Patients must have paravertebral stiffness and torso/lower extremity predominance.
Distribution of stiffness index score of ≥ 2, including stiffness in the legs or trunk.
Patients incapable of giving informed consent.
Patients with SPS-plus or variants of SPS such as paraneoplastic or progressive encephalomyelitis with rigidity and myoclonus (PERM). Patients with pure cerebellar ataxia, ocular motor apraxia.
Patients who are bed-bound or wheelchair-dependent.
Ongoing/active infection with hepatitis B virus (HBV), hepatitis C virus (HCV) or HIV Type 1/2 infection. Subjects with chronic hepatitis B or hepatitis C infection currently on treatment may participate if they have undetectable viral load within 12 months of screening date.