A First-in-human Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of UCB3101 in Healthy Participants

• Participants must be 18 to 65 years of age inclusive, at the time of signing theinformed consent form (ICF).

• Participants are overtly healthy as determined by medical evaluation includingmedical history, physical examination, laboratory tests, and electrocardiogram (ECG).

• Participants with clinical laboratory test results within the reference ranges ofthe laboratory. Isolated test results that are outside the specified ranges and thatare deemed clinically nonsignificant are allowed at the discretion of theinvestigator (except for liver enzymes). If a participant has 1 isolated test resultoutside the specific range for which the clinical significance is uncertain, repeattesting may be allowed at the discretion of the investigator.

• Participants are non-tobacco users or have given up smoking for at least 6 monthsprior to Screening.

• Participants have received a COVID-19 vaccine, including 2 boosters.

• Participants with body weight within 50.0 to 110.0kg and body mass index within therange 18.0 to 30.0kg/m2 (~40 to 66lbs/m2) (inclusive).

• Participant is male or female.

1. Male participants must refrain from donating sperm for the duration of thestudy and for 3 months after planned completion of the study. A maleparticipant with a female partner who is a woman of childbearing potential (WOCBP) must agree to use contraception for the duration of the study and for 3months after planned completion of the study.

2. A female participant is eligible to participate if she is not pregnant, notbreastfeeding, and either not a WOCBP or a WOCBP who agrees to follow thecontraceptive guidance for the duration of the study and for 1 month afterplanned completion of the study.

• Participant must be capable of giving signed informed consent which includescompliance with the requirements and restrictions listed in the ICF.

• Participant must be considered reliable and capable of adhering to the protocol,according to the judgment of the investigator, and capable of communicatingsatisfactorily with the investigator and complying with all study requirements.

Exclusion Criteria:

• Vulnerable individuals (eg, individuals kept in detention, serving soldiers),employees of the Sponsor or the contract research organization (CRO), with directinvolvement in the proposed study or other studies under the direction of theinvestigator or the CRO, as well as family members of the employees or theinvestigator

• Participant has any medical or psychiatric condition that jeopardize or wouldcompromise the study participant's ability to participate in this study.

• Participant has any clinically significant Electrocardiogram (ECG) abnormalities.

• Participant has a lifetime history of suicide attempt or has suicidal ideation inthe past 6 months.

• History or presence of clinically significant respiratory, neurological,gastrointestinal, renal, hepatic, pancreatic, hematological, cardiovascular,musculoskeletal, genitourinary, immunological, or dermatological disorders.

• Participant has had prior history of lymphoma, leukemia, or any malignancy.

• Participant has a clinically significant active infection (eg, sepsis, pneumonia,abscess) or has had a serious infection within 4 weeks before the first dose of IMP.

• Participant has had recurrent (at least 2) clinically relevant infections (eg, toothabscess, opportunistic infections, boils, etc) in the past 6 months.

• Participant has a history of recurrent headaches, including migraine.

• Participant has evidence or history of significant active bleeding or coagulationdisorder.

• Participant has a history of chronic alcohol or drug abuse within 12 months prior toBaseline.

• Participant has a history of skin disorders or extensive tattooing that preventclear visibility of the skin in case of a hypersensitivity reaction.

• Participant has scheduled surgery between Screening and 1 month after end of studyvisit.

• Participant has a history of clinically significant back pain, back pathology,and/or back injury that may predispose participant to complications or technicaldifficulty with lumbar puncture (LP).

• Participant has medical or surgical conditions for which LP is contraindicated.

• Participant is allergic to lidocaine or its derivatives.

• Participant has any clinically relevant brain magnetic resonance imaging (MRI)abnormality at Screening.

• Participant has received any prescription or nonprescription medicines, includingany monoclonal antibody (mAb) therapies and over the counter remedies or herbal anddietary supplements (other than vitamins within recommended daily dose limits)within 14 days (or 5 half-lives of the respective drug, whichever is longer) priorto Baseline, other than occasional use of analgesics such as paracetamol or topicalnasal corticosteroids for seasonal rhinitis.

• Participant has participated in another study of an investigational medicinalproduct (IMP) within 90 days (or 5 half-lives of the drug, whichever is longer)prior to Baseline or is currently participating in another study of an IMP.

• Participant has prior exposure to any IMP specifically targeting triggering receptorexpressed on myeloid cells 1 (TREM1).

• Participant has received any live vaccination within the 8 weeks prior to Day 1 oris anticipated to do so within 120 days after the final dose of IMP.

• Participant has any clinically relevant abnormal findings in physical examination,laboratory tests, vital signs, or ECG.

• Participant has total bilirubin >upper limit of normal (ULN).

• Participant has current or chronic history of liver disease or known hepatic orbiliary abnormalities (with the exception of Gilbert's syndrome or asymptomaticgallstones).

• Participant has a positive urine test for substances of abuse.

• Participant has a known active mycobacterium tuberculosis (TB) disease.

• Participant has a known history of active TB involving any organ system unlessadequately treated.

• Participant has a positive laboratory test results for human immunodeficiencyvirus-1/2 antibodies), hepatitis B surface antigen, or hepatitis B core antibodyresult at Screening.

• Participant has a positive hepatitis C antibody test result at Screening or within 3months prior to Baseline.

• Participant has clinically significant multiple or severe drug allergies,intolerance to topical corticosteroids, or severe post treatment hypersensitivityreactions (including, but not limited to, erythema multiforme major, linearimmunoglobulin A dermatosis, toxic epidermal necrolysis, and exfoliativedermatitis).

• Participant has symptomatic herpes zoster within 3 months prior to Screening.