Multiple Ascending Dose Study of MHS552 in Adults Participants With Systemic Lupus Erythematosus (SLE)

Inclusion Criteria:

• Fulfills the 2019 EULAR/American College of Rheumatology (ACR) classificationcriteria for SLE at least 3 months prior to and at screening.

• Patients with mild or moderately active SLE (SLEDAI-2K between 3 and 10, inclusive)at screening. Patients with cutaneous lupus are eligible as long as they satisfy thecriteria for systemic lupus.

• Patients must be on stable dose(s) of at least one of the following medications,unless the medication has been discontinued due to intolerance, inadequate response,or patient/physician decision:

• steroid at a dose ≥ 5mg but <30 mg of prednisone (or equivalent) per day,

• antimalarial (hydroxychloroquine/chloroquine/quinacrine) or thalidomide,

• disease modifying anti-rheumatic drugs (DMARDs):

• methotrexate (MTX),

• azathioprine (AZA),

• mizoribine,

• mycophenolate derivates. Steroid dose must be stable for at least 4 weeks priorto the first dosing. The dose of the other medications above must be stable forat least 12 weeks prior to the first dosing. If the patient is not on anymedications listed above, they must have been off these medications for atleast 12 weeks prior to dosing.

Exclusion Criteria:

• History of hypersensitivity to drugs of similar biological class, IL-2 proteinanalogues, or hypersensitivity to any components of the study drug, or history ofsevere hypersensitivity reaction or anaphylaxis to biological agents, e.g. humanmonoclonal antibody.

• Patients with central nervous system (CNS) lupus, active Lupus Nephritis, any typeof lupus flare requiring pulse steroid or immunosuppressive therapy withcyclophosphamide, rituximab, calcineurin inhibitors, or others except thosepermitted in the inclusion criteria.

• Systemic autoimmune disease other than lupus, which would interfere withparticipation in the study according to the Investigator's judgement. Treated,stable Hashimoto's thyroiditis is not exclusionary.

• Any of the following abnormal laboratory values at Screening or pre-dose Day 1assessment:

Hemoglobin levels below 8.0 g/dL at screening Eosinophil count >700 mm3 or >2 X Upper Limit of Normal (ULN), whichever is lower.

• History of capillary leak syndrome (CLS).

Other protocol-defined inclusion/exclusion criteria may apply