The purpose of the study is to assess safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending doses of rozanolixizumab in japanese, chinese and caucasian healthy-volunteer study participants.

Inclusion Criteria:

• Study participant must be 18 to 65 years of age, inclusive, at the time of signing the Informed Consent form (ICF)
• Study participants who are overtly healthy in the opinion of the investigator as determined by medical history and a general clinical examination, including physical examination, laboratory tests, and cardiac monitoring
• Study participant must be considered reliable and capable of adhering to the protocol, according to the judgment of the investigator, and is able to communicate satisfactorily with the investigator and comply with all clinical study requirements
• Japanese or Chinese study participant is of Japanese or Chinese descent, determined by verbal confirmation of familial heritage with all 4 grandparents of Japanese or Chinese descent
• Caucasian study participant is of Caucasian descent as evidenced in appearance and verbal confirmation of familial heritage with all 4 grandparents of Caucasian descent
• Study participant is of normal weight as determined by a body mass index (BMI) between 18 and 32 kg/m2, inclusive, with a body weight of at least 50 kg (male) or 45 kg (female) and no greater than 100 kg

Exclusion Criteria:

• Any medical (acute or chronic illness) or psychiatric condition that, in the opinion of the investigator, could harm the study participant or would compromise the study participant's ability to participate in this study.
• History of known inflammatory bowel disease, active diverticular disease, or a history of confirmed duodenal, gastric, or esophageal ulceration in the previous 6 months
• Significant allergies to humanized monoclonal antibodies
• Known hypersensitivity to any components of the investigational medicinal product (IMP)
• Clinically significant multiple or severe drug allergies, intolerance to topical corticosteroids, or severe posttreatment hypersensitivity reactions (including, but not limited to, erythema multiforme major, linear immunoglobulin A [IgA] dermatosis, toxic epidermal necrolysis, and exfoliative dermatitis)
• Current or chronic history of liver disease, or known hepatic or biliary abnormalities
• Study participant is splenectomized, or has a clinically relevant active infection (eg, sepsis, pneumonia, abscess) or has had a serious infection (resulting in hospitalization or requiring parenteral antibiotic treatment) within 6 weeks prior to study treatment
• Treatment with biologic agents (such as monoclonal antibodies including marketed drugs) within 3 months or 5 half-lives (whichever is longer) prior to dosing
• Received a vaccination within 8 weeks prior to Day -1; or intends to have a vaccination during the course of the study. Prior/Concurrent clinical study experience
• Exposure to more than 3 new chemical entities within 12 months prior to dosing
• Previously participated in this clinical study or has previously been assigned to treatment in a clinical study of IMP under investigation in this clinical study
• Participated in another study of an IMP (or a medical device) within the previous 90 days or 5 half-lives prior to Day -1 (whichever is longer) or is currently participating in another study of an IMP (or a medical device)

Due to the small sample size in this trial, IPD cannot be adequately anonymized i.e., there is a reasonable likelihood that individual participants could be re-identified. For this reason, data from this trial will not be shared.