This is a single-center, randomized, double-blind, placebo-controlled, phase 2 study. The purpose of the study is to initially evaluate the safety and efficacy of SM934 combined with steroids compared to placebo in adult subjects with active systemic lupus erythematosus (SLE) over a 12-week period.

Inclusion Criteria:

• Age: 18 to 70;
• Have a clinical diagnosis of SLE according to SLICC-2012 classification criteria;
• Have active SLE with SLEDAI-2k ≥ 6;
• Have positive anti-nuclear antibody (ANA) test results;
• Are on a stable steroids treatment (equals to prednison more than 7.5mg daily but no more than 0.5mg/kg/d) for SLE for at least 30 days prior to first dose of study agent;
• Females of childbearing age are willing to use appropriate contraception;
• Are voluntary to to provide and sign voluntary informed consent is given;

Exclusion Criteria:

• Have any unstable or progressive manifestation of SLE, including but not limited to Central nervous system (CNS) involvement, transverse myelitis, systemic vasculitis, vasculitis with GI involvement, severe or rapidly progressive lupus nephritis, lupus nephritis with proteinuria > 3g/24h, pulmonary hemorrhage, myocarditis;
• Have abnormal liver function test or renal function test: Alanine aminotransferase（ALT）or aspartate aminotransferase (AST) >2 upper limit of normal (ULN); Gamma-glutamyl transferase (GGT) >1.5 ULN; Creatinine or Blood urea nitrogen (BUN) >1.5 ULN;
• Have a history of acute myocardiac infarction, unstable angina, severe arrhythmias within 6 months prior to first dose of study agent;
• Have any major illness/condition or evidence of an unstable clinical condition not due to SLE (eg, cardiovascular, pulmonary, hematologic, gastrointestinal, hepatic, renal, psychiatric), which, in the Investigator's judgment, will substantially increase the risk to the participant if he or she participates in the study;
• Have any acute or chronic infectious disease, which requires medical intervention;
• Have a history of cancer within the last 5 years, except for adequately treated skin cancer, or carcinoma in situ of the uterine cervix;
• Have a planned surgical procedure;
• Have received a biologic investigational agent in the past one year;
• Have received the following treatment within 30 days prior to first dose of study agent: live vaccine; change of glucocorticoids dose; IV, intra-muscular (IM), intra-articular (IA) administration of glucocorticoids; other immunosuppressants/immunomodulators; anti-malarial drugs; traditional medicines which has proved to be effective in SLE;
• Have had a major organ transplant;
• Have a history of HIV, or test positive at screening for HIV;
• Test positive for Hepatitis B virus (HBV)-DNA or Hepatitis C virus (HCV)-RNA;
• Have or have had a substance abuse (drug, alcohol) problem in the past one year;
• Are currently using or planned to use estrogen-containing contraceptive methods;
• Have enrolled in an investigational study within 3 months prior to first dose of study agent;
• Investigator considers candidates not appropriating for the study.