a study to evaluate the efficacy, safety, pharmacokinetics (pk), and pharmacodynamics (pd) of satralizumab in participants with anti-n-methyl-d-aspartic acid receptor (nmdar) or anti-leucine-rich glioma-inactivated 1 (lgi1) encephalitis

Conditions: NMDAR Autoimmune Encephalitis; LGI1 Autoimmune Encephalitis

Summary: the purpose of this study is to assess the efficacy, safety, pk, and pd of satralizumab in participants with nmdar and lgi1 encephalitis.


Eligibility criteria:
inclusion criteria: * reasonable exclusion of tumor or malignancy before baseline visit (randomization) * onset of aie symptoms ≤ 9 months before randomization * meet the definition of "new onset" or "incomplete responder" aie * for women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use adequate contraception during the treatment period and for at least 3 months after the final dose of satralizumab or placebo * for participants enrolled in the extended china enrollment phase at china's sites: participants who are current residents of mainland china, hong kong, or taiwan, and of chinese ancestry nmdar aie cohort: * age ≥ 12 years * diagnosis of probable or definite nmdar encephalitis lgi1 aie cohort * age ≥ 18 years * diagnosis of lgi1 encephalitis exclusion criteria: * any untreated teratoma or thymoma at baseline visit (randomization) * history of carcinoma or malignancy, unless deemed cured by adequate treatment with no evidence of recurrence for ≥ 5 years before screening * for participants with nmdar aie, history of negative anti-nmdar antibody in cerebrospinal fluid (csf) using a cell-based assay within 9 months of symptom onset * historically known positivity to an intracellular antigen with high cancer association or glutamate decarboxylase 65 (gad-65) * historically known positivity to any cell surface neuronal antibodies other than nmdar and lgi1, in the absence of nmdar and lgi1 antibody positivity * confirmed paraneoplastic encephalitis * confirmed central or peripheral nervous system demyelinating disease * alternative causes of associated symptoms * history of herpes simplex virus encephalitis in the previous 24 weeks * any previous/concurrent treatment with interleukin-6 (il-6) inhibitory therapy (e.g., tocilizumab), alemtuzumab, total body irradiation, or bone marrow transplantation * any previous treatment with anti-cluster of differentiation 19 antibody (cd19 antibody), complement inhibitors, neonatal fc receptor antagonists, anti-b-lymphocyte stimulator monoclonal antibody * any previous treatment with t-cell depleting therapies, cladribine, or mitoxantrone * treatment with oral cyclophosphamide within 1 year prior to baseline * treatment with any investigational drug (including bortezomib) within 24 weeks prior to screening * concurrent use of more than one immunosuppressive therapy (ist) as background therapy * contraindication to all of the following rescue treatments: rituximab, intravenous immunoglobulin (ivig), high-dose corticosteroids, or intravenous (iv) cyclophosphamide * any surgical procedure, except laparoscopic surgery or minor surgeries within 4 weeks prior to baseline, excluding surgery for thymoma or teratoma removal * planned surgical procedure during the study * evidence of progressive multifocal leukoencephalopathy * evidence of serious uncontrolled concomitant diseases * congenital or acquired immunodeficiency, including human immunodeficiency virus (hiv) infection * active or presence of recurrent bacterial, viral, fungal, mycobacterial infection, or other infection * infection requiring hospitalization or treatment with iv anti-infective agents within 4 weeks prior to baseline visit * positive hepatitis b (hbv) and hepatitis c (hcv) test at screening * evidence of latent or active tuberculosis (tb) * history of drug or alcohol abuse within 1 year prior to baseline * history of diverticulitis or concurrent severe gastrointestinal (gi) disorders that, in the investigator's opinion, may lead to increased risk of complications such as gi perforation * receipt of live or live-attenuated vaccine within 6 weeks prior to baseline visit * history of blood donation (1 unit or more), plasma donation or platelet donation within 90 days prior to screening * history of severe allergic reaction to a biologic agent * history of suicide attempt within 3 years prior to screening except if this is clearly associated with and occurs during the acute phase of lgi-1 or nmdar encephalitis * any serious medical condition or abnormality in clinical laboratory tests that, in the investigator's judgment, precludes safe participation in and completion of the study * pregnant or breastfeeding, or intending to become pregnant during the study or within 3 months after the final dose of study drug