Evaluating Efgartigimod in Patients With Guillain-Barré Syndrome

Inclusion Criteria: * Provision of signed and dated informed consent form * Stated willingness to comply with all study procedures and availability for the duration of the study * Male or female, aged 18 years or older * Have a diagnosis of GBS according to the National Institute of Neurological Disorders and Stroke Diagnostic Criteria for Guillain-Barré Syndrome * Onset of GBS-related weakness ≤14 days prior to infusion * GBS-DS score of 3, 4, or 5 Exclusion Criteria: * Pregnant and lactating women, and those intending to become pregnant during the trial or within 90 days after the last dosing. Women of childbearing potential should have a negative serum pregnancy test at Screening and a negative urine pregnancy test at Baseline prior to administration of IMP. Note: Women of childbearing potential should use a highly effective method of contraception (i.e., pregnancy rate of less than 1% per year) during the trial and for 90 days after the last administration of the IMP. They must be on a stable regimen, for at least 1 month, of combined estrogen and progestogen hormonal contraception with inhibition of ovulation, progestogen-only hormonal contraception associated with inhibition of ovulation, intrauterine device (IUD), intrauterine hormone-releasing system, bilateral tubal occlusion, vasectomized partner, or agree upon continuous abstinence from heterosexual sexual contact. * Male patients who are sexually active and do not intend to use effective methods of contraception (as mentioned above) during the trial or within 90 days after the last dosing or male patients who plan to donate sperm during the trial or within 90 days after the last dosing. Note: Sterilized male patients who have had vasectomy with documented aspermia post-procedure, or male patients who have a partner of non-childbearing potential, can be included. * GBS DS of 2 or less. * Patients with any known severe bacterial, viral or fungal infection or any major episode of infection that required hospitalization or injectable antimicrobial therapy in the last 8 weeks prior to Screening. * Patients with more than 14 days after onset of symptoms. * Patients with known IgG deficiency. * Patients with recurrent GBS. * Use of investigational drug within 3 months or 5 half-lives of the drug (whichever is longer) prior to Screening. * Patients who have a history of malignancy, including malignant thymoma, or myeloproliferative or lymphoproliferative disorders, unless deemed cured by adequate treatment with no evidence of recurrence for ≥ 3 years before Screening. Patients with completely excised non-melanoma skin cancer (such as basal cell carcinoma or squamous cell carcinoma) or cervical carcinoma in situ would be permitted at any time. * Patients with clinical evidence of other significant serious disease or patients who underwent a recent major surgery, which could confound the results of the trial or put the patient at undue risk. Patients with renal/hepatic function impairment can be included.