This is a randomized, open-label, parallel-group, single-dose study comparing the pharmacokinetics of efgartigimod in blood following a single administration of efgartigimod PH20 SC via a prefilled syringe versus a vial + syringe in healthy participants.

Inclusion Criteria:

• Is at least the local legal age of consent for participation in a clinical study and ≤55 years when signing the ICF
• Is capable of providing signed informed consent, and complying with protocol requirements
• Agrees to use contraceptive measures consistent with local regulations and the following: Women Of Child-Bearing Potential must have a negative serum hCG pregnancy test at screening and a negative urine hCG pregnancy test at baseline before receiving IMP.
• Has a BMI between 18 and 30 kg/m2 , inclusive, and a weight between 50 and 100 kg (inclusive) at screening

Exclusion Criteria:

• Has a known autoimmune disease or any medical condition that, in the investigator's judgment, would interfere with an accurate assessment of clinical symptoms or puts the participant at undue risk
• Has a history of malignancy, unless considered cured by adequate treatment with no evidence of recurrence for ≥3 years before the administration of IMP. Adequately-treated participants with the following cancers can be included at any time: Basal cell or squamous cell skin cancer; Carcinoma in situ of the cervix; Carcinoma in situ of the breast; Incidental histological findings of prostate cancer.
• Has a clinically significant active infection that is not sufficiently resolved in the investigator's opinion.
• Has a positive serum test at screening for active infection with any of the following: HBV indicative of an acute or chronic infection, unless associated with a negative HBsAg or negative HBV DNA test; HCV based on HCV antibody assay unless a negative RNA test is available ; HIV based on test results (regardless of therapy treatment or not).
• Has a clinically significant disease, recent major surgery (within 3 months of screening), or intends to have surgery during the study; or any other medical condition that, in the investigator's opinion, would confound the results of the study or put the participant at undue risk.
• Received a different IMP in another clinical study <12 weeks or 5 half-lives (whichever is longer) before screening.
• Is currently participating in another interventional clinical study. Has a known hypersensitivity to IMP or its excipients.
• Has abdominal skin condition that does not allow for absorption and assessment of local safety of the planned SC injection, as determined by the investigator.
• Has a history of (within 12 months before screening) or current alcohol, drug, or medication abuse, as assessed by the investigator.
• Is pregnant or lactating or intends to become pregnant during the study.
• Previously participated in an efgartigimod clinical study and received at least 1 dose of IMP.
• Is taking concomitant medications (except for oral contraceptives or occasional acetaminophen).
• Has a total IgG of <4 g/L at screening.
• Had a positive COVID-19 test result on day -1 or contact with someone with a known COVID-19 infection within 2 weeks before receiving IMP.