The primary objective of the study is to evaluate the pharmacokinetics (PK) of rocatinlimab given as a single subcutaneous (SC) dose in a vial compared to a prefilled syringe in healthy participants.

Inclusion Criteria

1. Participant has provided informed consent before initiation of any study-specific activities/procedures.
2. Healthy male or female participants, between 18 and 65 years of age (inclusive)
3. Body mass index between 18 and 32 kg/m^2 (inclusive)

Exclusion Criteria

1. History or evidence, at Screening or Check-in, of clinically significant disorder, condition, or disease not otherwise excluded that, in the opinion of the Investigator (or designee), would pose a risk to participant safety or interfere with the study evaluation, procedures, or completion.

2. History or evidence of clinically significant arrhythmia at Screening, including any clinically significant findings on the electrocardiogram (ECG) taken at Check-in.

3. A QT interval corrected for heart rate using Fridericia's method (QTcF) > 450 msec in male participants or > 470 msec in female participants or history/evidence of long QT syndrome at Screening or Check-in.

4. Systolic blood pressure > 140 mmHg or < 90 mmHg, or diastolic blood pressure > 90 mmHg, or pulse rate > 100 bpm

5. History of hypersensitivity, intolerance, or allergy to any drug compound, food, or other substance, unless approved by the Investigator (or designee). Participants with seasonal allergies will be permitted.

6. Estimated glomerular filtration rate less than 70 mL/min/1.73 m^2

7. Alanine aminotransferase or aspartate aminotransferase > 1.5 times the upper limit of normal at Screening or Check-in.

8. Positive hepatitis B or hepatitis C panel (including positive hepatitis B surface antigen [HBsAg] and/or positive hepatitis C antibody) and/or positive human immunodeficiency virus test at Screening. Participants whose results are compatible with prior hepatitis B vaccination (positive hepatitis B surface antibody, negative hepatitis B core antibody, negative HBsAg) or prior infection (positive hepatitis B core antibody, positive hepatitis B surface antibody, negative HBsAg) may be included.

9. Participants who have received live vaccines within 5 weeks prior to Screening, or plan to receive live vaccines within 90 days after administration of an investigational product.

   Inactive vaccination (e.g., non-live or nonreplicating agent), including coronavirus-2019 (COVID-19) vaccination, is allowed.

10. History of latent tuberculosis or active chronic, recurrent, or acute infection requiring treatment with systemic antibiotics, antiviral, antiparasitic, antiprotozoal, or antifungals which has not completely resolved, or for which therapy has not been completed, within 4 weeks before Screening.

11. Use of any over-the-counter or prescription medications within 30 days or 5 half-lives (whichever is longer) before Check-in, excluding the following:

    1. Acetaminophen (paracetamol) (up to 2 g per day) for analgesia will be allowed.
    2. Hormonal contraception listed in Appendix 3 will be allowed.
    3. Hormone replacement therapy (e.g., estrogen) and hormonal contraceptives will be allowed.

12. All herbal medicines (e.g., St. John's wort), vitamins, and supplements consumed by the participant within the 30 days prior to Check-in, unless deemed acceptable by the Investigator (or designee) and in consultation with the Sponsor.

13. Participant has received a dose of an investigational drug within the past 90 days or 5 half-lives, whichever is longer, prior to Check-in.

14. Have previously completed or withdrawn from this study or any other study investigating rocatinlimab or have previously received rocatinlimab.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request.

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors. If not approved, a Data Sharing Independent Review Panel will arbitrate and make the final decision. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.