Phase III Clinical Study of NPB-01 in Patients With Autoimmune Encephalitis

Inclusion Criteria * \< At 1st registration \> Patients meeting the possible diagnostic criteria for autoimmune encephalitis * \< At 1st registration \> Patients with a CASE score of 5 to 22 during the screening period * \< At 1st registration \> Patients with autoimmune encephalitis in progress (active and requiring therapeutic intervention) * \< At 1st registration \> IVIG therapy and steroid pulse therapy are considered necessary by the investigator. * \< At 1st registration \> Patients aged 15 years or older at the time of informed consent * \< At 2nd registration \> Patients who meet any of the following (1) to (6): 1. Definite diagnostic criteria for autoimmune limbic encephalitis 2. MRI evidence of demyelination (probable autoimmune encephalitis) 3. Probabilistic diagnostic criteria for anti-NMDAR encephalitis 4. Probabilistic diagnostic criteria for Bickerstaff brainstem encephalitis 5. Probabilistic diagnostic criteria for Hashimoto's encephalopathy 6. Diagnostic Criteria for Autoimmune Encephalitis with Negative but Probable Autoantibodies * \< At 2nd registration \> CASE score of 5 to 22 on Day 8 of the previous treatment period * \< At 2nd registration \> Patients who have had an inadequate response to steroid pulse therapy Exclusion Criteria: * \< At 1st registration \> Patients with strongly suspected infectious encephalitis * \< At 1st registration \> Patients who received immunoglobulin preparations within 8 weeks prior to informed consent * \< At 1st registration \> Patients who received plasma exchange within 4 weeks prior to informed consent * \< At 1st registration \> Patients who received immunosuppressants (Rituximab, cyclophosphamide, etc.) within 4 weeks prior to informed consent * \< At 1st registration \> Patients who have had tumor resection associated with autoimmune encephalitis within 4 weeks prior to informed consent * \< At 1st registration \> Patients with a history of shock or hypersensitivity to the ingredients of NPB-01 * \< At 1st registration \> Patients with known IgA deficiency * \< At 1st registration \> Patients with renal disorder * \< At 1st registration \> Patients with a current or previous history of cerebral or cardiovascular disorders (Asymptomatic cerebral infarction and myocardial infarction that occurred more than 5 years ago are not applicable.) * \< At 1st registration \> Patients at high risk of thromboembolism * \< At 1st registration \> Patients with haemolytic/blood loss anaemia * \< At 1st registration \> Immunosuppressed/immunocompromised patients * \< At 1st registration \> Patients with decreased cardiac function * \< At 1st registration \> Pregnant, expected (desired or planned) pregnant, or breastfeeding patients * \< At 1st registration \> Use of prohibited medications or treatment in this study * \< At 1st registration \> Patients who received investigational product in this study (re-enrollment prohibited) * \< At 1st registration \> Patients who have received treatment with investigational product other than this study within 4 months prior to informed consent * \< At 1st registration \> Patients with a history of hypersensitivity to methylprednisolone sodium succinate * \< At 1st registration \> Patients who have a tumor associated with autoimmune encephalitis and are considered to require resection during the study period. * \< At 1st registration \> Patients receiving intravenous general anesthetics or sedative hypnotics * \< At 1st registration \> Patients in coma * \< At 1st registration \> Ventilated patients * \< At 1st registration \> Patients who cannot undergo protocol-specified tests/assessments * \< At 1st registration \> Other patients considered ineligible for the study by the investigator * \< At 2nd registration \> Positive herpes simplex virus DNA qualitative test in the screening period. * \< At 2nd registration \> Serum creatinine ≥ 2 times the upper limit of normal during the screening period. * \< At 2nd registration \> Total protein ≥ 9 g/dL during the screening period. * \< At 2nd registration \> Patients with hematocrit ≥ 55% during the screening period * \< At 2nd registration \> Patients who meet any of the exclusion criteria at the time of first registration