A Study to Test the Efficacy, Safety, and Pharmacokinetics of Rozanolixizumab in Adult Study Participants With Leucine-Rich Glioma Inactivated 1 Autoimmune Encephalitis

Inclusion Criteria: * Study participant must be ≥18 to ≤89 years of age * Study participant must be seropositive for leucine-rich glioma inactivated 1 (LGI1) antibody * Study participant must have ≥2 seizures/week during the Screening Period or have experienced such seizures that stopped following high dose corticosteroids (500 to 1000 milligram (mg) methylprednisolone (MP) equivalent/day): * Either faciobrachial dystonic seizures (FBDS) with or without other focal (partial) seizures including focal to bilateral tonic clonic * Or focal (partial) seizures including focal to bilateral tonic clonic and fulfil the following new-onset Autoimmune encephalitis (AIE) criteria * Study participant has initiated or re-initiated corticosteroids at a dose of 500 to 1000 mg MP equivalent/day within 42 days prior to randomization. Participants re-initiating corticosteroids are eligible only if re-initiation is due to seizure rebound and within the timeframe outlined. If the study participant has initiated a steroid taper, the study participant cannot receive an oral steroid dose lower than 40mg/day when randomized * Study participant with onset of disease symptom between 0 to 12 months prior to Screening, per investigator's assessment. * Study participant weighs at least 35 kg at Screening * A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies: i) Not a woman of childbearing potential (WOCBP)…