The purpose of this study is to evaluate the safety and tolerability of single ascending doses of UCB5285 in healthy study participants, including healthy Japanese study participants

Inclusion Criteria:

• For study participants of Japanese origin: study participant who is born in Japan and of Japanese descent as evidenced in appearance and verbal confirmation of familial heritage with all 4 grandparents and both parents born in Japan and has not had a significant change in lifestyle or diet since leaving Japan
• For all study participants:
• Study participant must be 18 to 55 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, laboratory tests, and cardiac monitoring.
• Body weight within 40 kilograms (kg) to 110 kg and body mass index (BMI) within the range of 18 kilograms per meter square (kg/m2) to 30 kg/m2 (inclusive)

Exclusion Criteria:

• Study participant has a history or presence of any medical or psychiatric condition, physical examination finding, laboratory test result, electrocardiogram (ECG), or vital sign that, in the opinion of the investigator, could significantly alter the absorption, or elimination of drugs; constitute a risk when taking the study intervention; or interfere with the interpretation of data
• Study participant has a recent history (within 6 months of Screening) or currently active clinically significant bacterial, fungal, endoparasite, or viral infection.
• Study participant has a significant allergy to humanized monoclonal antibody (mAbs)

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