The purpose of the study is to compare the pharmacokinetics (PK), safety and tolerability of a single subcutaneous (sc) dose of bimekizumab (BKZ) when administered using bimekizumab-autoinjector (AI)-2mL presentation versus bimekizumab-AI-2x1mL presentation in healthy study participants.

Inclusion Criteria:

• Study participant must be ≥18 years and ≤65 years of age inclusive, at the time of signing the informed consent
• Study participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, vital signs, 12-lead electrocardiogram (ECG), and laboratory tests, during the Screening Period and on admission
• Study participant has a body temperature between 35.0°C and 37.5°C, inclusive, at Screening and on admission
• Body weight minimum of 50 kg for male and 45 kg for female study participants and a maximum of 100 kg for all study participants, and body mass index (BMI) within the range 18 to 32 kg/m^2 (inclusive) at the Screening Visit
• Male or female. Contraception guidelines (as per the standard UCB contraceptive guideline) will be applicable.

Exclusion Criteria:

• Study participant has a known hypersensitivity to any components of the bimekizumab (and/or an investigational device) as stated in this protocol
• Study participant has an active infection or history of infections as follows:
• Any active infection (except common cold) within 14 days prior to Screening Visit
• A serious infection, defined as requiring hospitalization or iv anti-infectives within 2 months prior to the Screening Visit
• A history of opportunistic, recurrent, or chronic infections that, in the opinion of the Investigator, might cause this study to be detrimental to the study participant. Opportunistic infections are infections caused by uncommon pathogens (eg, pneumocystis jirovecii, cryptococcosis) or unusually severe infections caused by common pathogens (eg, cytomegalovirus, herpes zoster)
• Study participant has a history of a positive TB test or evidence of possible TB or latent TB infection at Screening Visit. Refer to Tuberculosis Detection Procedure Guideline for details regarding TB infection status, detection procedures, and the related exclusion criteria
• Study participants receiving any live (includes attenuated) vaccination within the 8 weeks prior to the Screening Visit (eg, inactivated influenza and pneumococcal vaccines are allowed, but nasal influenza vaccination is not permitted). Live vaccines are not allowed during the study or for 20 weeks after the last dose of the investigational medicinal product (IMP)
• Study participant has previously participated in this study or a study participant has previously been assigned to bimekuzimab treatment in any other study
• Exposure to 3 or more new chemical entities within 12 months prior to dosing
• Current enrollment or past participation within the last 30 days before signing the informed consent form (ICF) in any other clinical study involving an investigational study intervention or any other type of medical research
• Study participant has concurrent acute or chronic viral hepatitis B or C or human immunodeficiency virus (HIV) infection. Study participants who have evidence of, or tested positive for hepatitis B or hepatitis C are excluded
• Study participant has made a blood donation of a blood loss of more than 400 mL of blood or blood products within 90 days prior to admission (Day -1) or plans to donate blood during the study
• Female study participant who is pregnant, or plans to become pregnant during the study, or lactating, or sexually active with childbearing potential who is not using a medically accepted birth control method
• Study participant has an alcohol consumption of more than 21 units (males) or 14 units (females) of alcohol per week (1 unit of alcohol is equivalent to 12.5 mL ethanol at room temperature)
• Study participant tests positive for alcohol or drugs (urine test) at Screening or Day -1
• Vulnerable study participants (eg, participants kept in detention, protected adults under guardianship or trusteeship, and soldiers or participants committed to an institution by governmental or juridical order), employees of the Sponsor or the contract research organization (CRO) with direct involvement in the proposed study or other studies under the direction of the Investigator or the CRO, as well as family members of the employees or the Investigator
• Study participant has a positive test result for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in real-time reverse transcriptase polymerase chain reaction (RT-PCR) on the admission sample
• Study participant has clinical signs and symptoms consistent with COVID-19, eg fever, dry cough, dyspnea, sore throat, fatigue, or confirmed infection by appropriate laboratory test within the previous 14 days prior to Screening or on admission
• Study participant who had severe course of COVID-19 (ie, hospitalization, extracorporal membrane oxygenation, mechanically ventilated)

Data from Phase 1 trials in Healthy Volunteers is outside of UCB's data sharing policy and is unavailable for sharing.

Baseline characteristics refer to the SS which consisted of all study participants randomized and received full or partial IMP according to the treatment the participants actually received.

From Baseline (Day 1) to end of Safety Follow-Up (up to Day 140)

TEAEs are defined as AEs not present prior to the administration of IMP or any unresolved event already present before administration of IMP that worsens in intensity following exposure to study treatment. The SS consisted of all study participants who randomized and received full or partial IMP according to the treatment the study participants actually received.