This study was to compare the rate and extent of absorption of a single dose of nemolizumab administered with auto-injectors [AI] (test) versus dual-chamber syringes [DCS] (reference) under controlled conditions in healthy adult subjects.

Inclusion Criteria:

• Male and female participants aged 18 to 65 years at screening visit.
• Body weight >= 45 kilogram (kg) and body mass index between >=18.0 and <30.0 kilograms per meter squared (kg/m^2) at both screening and baseline visits.
• Medically healthy with normal clinical status as judged by the investigator based on medical history, physical examination, and clinical laboratory tests.
• Willing to abstain from all prescription medications during the study, (defined hereafter as after signing of informed consent form), except to treat AEs and contraception, and as permitted under Exclusion 2. Limited use of non-prescription medications/supplements that were not believed to affect participant's safety or the overall results of the study might be permitted at the discretion of investigator.
• Female participants of childbearing potential (i.e., fertile, after menarche and, until becoming postmenopausal unless permanently sterile) must agree either to be strictly abstinent throughout the study and for 12 weeks after the study drug injection, or to use an adequate and approved method of contraception throughout the study and for 12 weeks after the study drug injection. Males are not required to use contraception, and there is no restriction on sperm donation.
• Female participants of non-childbearing potential must meet one of these criteria; absence of menstrual bleeding for 1 year before the screening visit with no other medical reason, confirmed with follicle-stimulating hormone (FSH) level in the postmenopausal range or documented hysterectomy, bilateral salpingectomy, or bilateral oophorectomy at least 3 months before the study.
• Willing and able to comply with all of the time commitments and procedural requirements of the clinical study protocol.
• Understood and signed an informed consent form before any investigational procedure(s) are performed.

Exclusion Criteria:

• History of hypersensitivity (including anaphylaxis) to an immunoglobulin product (plasma-derived or recombinant, e.g., monoclonal antibody) or to any of the study drug excipients.
• Cutaneous infection within 1 week before the baseline visit or any infection requiring treatment with oral, parental antibodies, antivirals, antiparasitics, or antifungals within 2 weeks before the baseline visit.
• Any confirmed or suspected coronavirus disease (COVID-19) infection within 2 weeks before screening or baseline visit.
• Positive serology results (hepatitis B surface antigen [HBsAg] or hepatitis B core antibody [HBcAb], hepatitis C [HCV] antibody with positive HCV RNA, or human immunodeficiency virus [HIV] antibody) at the screening visit.
• Known or suspected immunosuppression or unusually frequent, recurrent, severe, or prolonged infections as per investigator judgment.
• History of lymphoproliferative disease or history of malignancy of any organ system within last 5 years, except for basal cell carcinoma, squamous cell carcinoma in situ (Bowen's disease), or carcinomas in situ of the cervix that have been treated and have no clinical evidence of recurrence in the last 12 weeks before baseline visit, or actinic keratoses that have been treated.
• Previous treatment with Nemolizumab.
• Known active or untreated latent tuberculosis infection.
• Any condition that may interfere with study assessments (e.g., poor venous access or needle phobia).
• Having received a live-attenuated or non-live vaccine within 4 weeks before the baseline visit or are expected to be vaccinated during the study or during the 12 weeks after the last study drug injection, except for non-live seasonal vaccinations, COVID-19 and /or emergency vaccinations.
• Planned or expected major surgical procedure during the clinical study.
• Pregnant women, breastfeeding women, or women planning a pregnancy during the study or 12 weeks after the study drug injection.
• Participating or participated in any other study with an investigational drug or device within the past 8 weeks before the screening visit, or is in an exclusion period from a previous study.
• Participants who have donated ≥ 500 mL of blood in the last 3 months before doing.
• History of alcohol or substance abuse within 6 months of the screening visit.