A Study to Evaluate Mosunetuzumab in Participants With Systemic Lupus Erythematosus With or Without Active Lupus Nephritis

Prior treatment

• Treatment with investigational therapy within 30 days or 5 drug-elimination half-lives (whichever is longer) prior to initiation of study treatment and during the study
• Major surgery requiring hospitalization during the 4 weeks prior to screening or during screening, or any planned surgery or procedure requiring hospitalization during the 12 weeks following study drug administration
• Alcohol or substance abuse within the 12 months prior to screening
• Active overlap syndrome with mixed connective tissue disease or systemic sclerosis within the 12 months prior to screening or during screening
• Catastrophic or severe antiphospholipid syndrome within the 12 months prior to screening or during screening. Antiphospholipid syndrome adequately controlled by anticoagulant therapy for at least 2 months prior to screening is acceptable
• Active severe or unstable lupus-associated neuropsychiatric disease or where, in the opinion of the investigator, it is likely to require treatment with protocol-disallowed therapies. Examples of neuropsychiatric SLE manifestations include, but are not limited to the following: meningitis, retinitis, cerebral vasculitis, myelopathy, demyelination syndromes, acute confusional state, psychosis, acute stroke or stroke syndrome, cranial neuropathy, status epilepticus or seizures, cerebellar ataxia, and mononeuritis multiplex
• History of any non-SLE disease treated with oral, intravenous, or intramuscular corticosteroids for more than 14 days in total during the one year prior to Day 1
• History of treatment with any T cell-engaging bispecific antibodies or CAR-T therapy within the past 2 years
• Receipt of any live or attenuated vaccine in the 28 days prior to or during screening

Other illness

• Active infection of any kind, excluding fungal infection of the nail beds
• Any major episode of infection as defined by the protocol
• History of serious recurrent or chronic infection
• History of progressive multifocal leukoencephalopathy (PML)
• Tuberculosis (TB) infection
• History of cancer, including solid tumors, hematological malignancies, and carcinoma in situ, within the past 5 years
• High risk for clinically significant bleeding or any condition requiring plasmapheresis, IV immunoglobulin, or acute blood product transfusions

Other

• Pregnant or breastfeeding, or intention of becoming pregnant during the study or within the time frame in which contraception is required

• Diagnosis of SLE for ≥ 6 months as assessed using the 2019 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) Classification Criteria at screening