This study aims to see how the body reacts to empasiprubart, administered using an autoinjector (AI). The study will also look at other effects of empasiprubart, how it works in the body, and if it is safe.

The study consists of 2 parts: parts A and B. In part A, eligible participants will be randomized to receive empasiprubart SC AI via abdomen, empasiprubart SC AI via thigh, or empasiprubart IV (intravenously). In part B, eligible participants will be randomized to receive empasiprubart SC AI via abdomen or empasiprubart IV.

Participants from part A will be in the study for approximately up to 37 weeks . Participants from part B will be in the study for up to approximately 43 weeks.

Inclusion Criteria:

• Is at least the local legal age of consent and aged 18 to 65 years, inclusive, when signing the ICF.
• Has a body weight between 50 and 120 kg and a BMI between 18 and 35 kg/m2, inclusive.

Exclusion Criteria:

• Has any current or past clinically meaningful medical or psychiatric condition that, in the investigator's opinion, would confound the study results or put the participant at undue risk.
• Clinical diagnosis of SLE. For participants with an antinuclear antibody titer of ≥1:80 and a positive anti-double-stranded DNA and/or positive anti-Smith result at screening, an SLE diagnosis must be ruled out before the first IMP administration.
• Previously participated in an empasiprubart clinical study and received at least 1 dose of IMP.