Single and Multiple Ascending Dose Study in Healthy Participants and Participants With an Autoimmune Disease

Inclusion Criteria:

(Applicable to Both Healthy and an Autoimmune Disease Participants Unless Indicated Otherwise)

1. Participant provides written informed consent prior to any protocol relatedprocedures, including screening evaluations. Participant must be able to understandthe consent form and instructions and to provide consent directly; no guardian/legalrepresentative or caregiver may provide consent for the participant.

2. Male or female, greater than or equal to (>=)18 and less than or equal to (<=) 65years of age, with a body mass index (BMI) within the range of 18.5 to 29.9 kilogramper square meter (kg/m^2) (inclusive) and body weight of >=50 kilograms (kg).

3. Participant is healthy, in the clinical judgement of the Investigator, based medicalhistory, physical examination, vital signs, ECG, and laboratory investigations (i.e., has clinical laboratory tests that are within the reference ranges or areclinically acceptable per Investigator judgment).

4. Participant has a seated systolic blood pressure (SBP) >=90 mm Hg and <=140 mm Hg ora seated diastolic BP (DBP) >=50 mm Hg or <=90 mm Hg.

5. Participant is willing and able to understand and comply with all aspects of theprotocol.

6. Participant must agree to the following requirements during the study:

• Women of childbearing potential (WOCBP) must have a negative serum pregnancytest result within 7 days prior to first dosing plus a negative urine pregnancytest pre-dose on Day 1 and must be willing to use a highly effective form ofcontraception (ICH E8 Guideline, 1997; (ICH M3 [R2] Guidance, 2009; (FDA M3 [R2] Guidance, 2010) for the duration of the study and for at least 3 monthsafter the last dose of study medication. Methods like periodic abstinence,post-ovulation procedures and withdrawal are not considered adequate.

• Males with partners of childbearing potential must be willing to use condoms incombination with a second effective method of contraception during the study.Male participants must continue to use contraception (condoms plus a secondeffective method) for 165 days following administration of the study drug.

• Male participants must agree not to donate sperm during the study and for 165days following administration of the study drug.

Participants with an Autoimmune Disease (Cohort 9 Only):

For participants with an autoimmune disease, the inclusion criteria for healthy participants listed above apply, with the following changes/additions:

1. Male or female, >=18 to <=65 years of age, with a BMI within the range 18.5 to 34.9kg/ m^2, and body weight of >=50 kg.

2. Current diagnosis of an autoimmune disease by the Investigator and with signs andsymptoms consistent with an autoimmune disease for at least 3 months prior to Day -1 (baseline).

Exclusion Criteria:

(Applicable to Both Healthy and an Autoimmune Disease Participants Unless Indicated Otherwise)

1. Participant has received treatment with LAD191 previously.

2. Known hypersensitivity to LAD191 or any of its excipients.

3. Hypersensitivity or reaction to a prior biologic (antibody-based) therapy (regardless of indication), that was clinically significant, as per judgment ofInvestigator.

4. History of clinically significant hematological, renal, endocrine, pulmonary,gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, inflammatory, orallergic disease (including drug allergies, any active seizure disorder requiringtherapy with antiepileptic drugs, active peptic ulcer disease, gastrointestinalbleeding, chronic gastritis, inflammatory bowel disease or chronic diarrhea, butexcluding mild seasonal allergies or stable, well-controlled thyroiditis). Note thatparticipants with thyroid hormone deficiency, hypertension, hyperlipidemia, ordiabetes mellitus may be included in Part 3 of the study.

5. Active chronic or acute infection requiring treatment with systemic antimicrobials,antivirals, antiparasitics, antiprotozoals, or antifungals within 2 weeks before Day -1, or superficial skin infections within 4 weeks prior to Day -1, or fever > 38°Cduring within 1 week before Day -1.

6. A positive test for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) onDay -1, or the second negative test after a previous SARS CoV-2 infection was <=14days before Day -1, or the participant's SARS CoV-2-associated symptoms resolved <=14 days before Day -1.

7. Presence of skin comorbidities that may interfere with study assessments, in theopinion of the Investigator.

8. Participant has current tuberculosis (TB) or any history of active or latent TB,regardless of prior treatment.

9. History of malignancy, regardless of outcome.

10. Participant has any condition that, in the opinion of the Investigator, wouldinterfere with the PK evaluation of LAD191 or participant safety or theinterpretation of study results

11. Clinically significant ECG abnormality, including, but not limited to, thefollowing:

• An abnormal PR interval (>=220 msec or <=100 msec).

• QTc prolongation (corrected QT interval by Fredericia's formula [QTcF] >=450msec).

• Mean heart rate <=45 bpm or >100 bpm.

12. Known history of liver disease or clinically significant abnormal (as per judgmentof Investigator) liver function test(s) at Screening (ALT, AST, alkaline phosphatase [ALP], or TBili >1.5 x ULN).

13. Impaired renal function (laboratory values out of the normal range that areclinically significant, as judged by the Investigator).

14. Congenital or acquired immunosuppressive condition that would put participant atrisk during the study, per Investigator judgment.

15. Neutropenia; defined as a neutrophil count <2.0 x 10^9/L, at Screening.

16. Participant has had major surgery (requiring general anesthesia) within 3 monthsprior to Day -1, or has major surgery planned during the study. For participantswith an autoimmune disease may have had incision and drainage of abscesses up to 1week before Day -1).

17. Participant has donated plasma or blood or has lost more than 450 ml blood in the 60days prior to Day -1, or intends to donate blood during the study or in the 60 daysafter the last scheduled study visit.

18. Participant is pregnant or breastfeeding (or is planning to become pregnant orbreastfeed during the study or within 90 days after the last dose of study drug).

19. History of, or positive test result at Screening for, hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBcAg), antibody to thehepatitis C virus (anti-HCV), or antibody to the human immunodeficiency virus (HIV-1/2).

20. Participant has taken any medications, including over-the-counter (OTC) medications,within 14 days (or at least 5 half-lives, whichever is longer) before Day -1. (Notethat hormonal contraceptives are allowed, and acetaminophen is permitted at doses <=2 g/day up to 48 hours prior to each study visit).

21. Participant has received any type of live or attenuated vaccinations within 28 daysprior to Screening, or is planning to receive any such vaccine during the study (inactive vaccines are allowed) or has received a SARS-CoV-2 vaccine within 14 daysof Day 1.

22. Participant has received any investigational drug in any clinical study within 30days (or at least 5 half-lives, whichever is longer) prior to Day -1, or is onextended follow-up from such a clinical study.

23. Participant has a history (within 2 years prior to Screening) of alcohol or drugabuse, as per Investigator judgment, or has a positive urine screen for drugs ofabuse (opiates, cocaine, amphetamines, cannabinoids, barbiturates, benzodiazepines,cotinine, phencyclidine) at Screening or on Day -1, or a positive urine alcohol testat Screening or on Day -1.

24. Consumption of alcohol within 48 hours (2 days) before Day -1.

25. Participant is involved in strenuous physical activity or contact sports within 96hours (4 days) prior to Day -1.

26. Consumption of any foods containing poppy seeds within 48 hours (2 days) prior toScreening and Day -1 as this could result in a false positive drug screen result.

27. Participant has any other serious or uncontrolled physical or mental dysfunctionthat, as judged by the Investigator, could place the participant at higher riskderived from his/her participation in the trial, could confound the results of thetrial or is likely to prevent the participant from complying with the requirementsof the trial or completing the trial.

28. Participant is an employee or relative of the Sponsor/vendors, clinical study site,or is an individual or employee directly involved with the conduct of the study oris an immediate family member of such an individual.

Participants with an Autoimmune Disease (Cohort 9 Only)

For participants with an autoimmune disease, the exclusion criteria for healthy participants listed above apply, with the following additions:

1. Concurrent use of the following medications/treatments:

• Systemic immunosuppressants/immunomodulators or other systemic treatments forautoimmune disease within 28 days or 5 half-lives (whichever is longer) before Day -1.

• Systemic antivirals or antifungals within 28 days prior to Day -1, or systemicantibiotics within 28 days prior to Day -1.

• Oral analgesics including opioids within 14 days prior to Day -1, except foracetaminophen at doses of <=2 g/day for relief of autoimmune disease-associatedpain.

• Prescription and OTC medications other than those used for the treatment of anautoimmune disease within 14 days or 5 half-lives (whichever is longer) before Day -1, except for hormonal contraceptives, thyroid replacement medications, andmedications used for the treatment of hypertension, diabetes mellitus (but notmetformin), or hyperlipidemia which are permitted provided the medication(s) anddosage (dose and frequency) have been stable for at least 6 weeks prior to Day -1.Note that participants with thyroid hormone deficiency, hypertension, diabetesmellitus, or hyperlipidemia may be included in Part 3 of the study.