The study is a Phase II clinical trial to evaluate the efficacy and safety of SHR-2173 in patients with lupus nephritis (LN). It adopts a randomized, double-blind, placebo-controlled, multicenter trial design.

Inclusion Criteria:

1. Age 18-70 years (inclusive) at informed consent signing, regardless of sex;
2. Body weight ≥ 40.0 kg and body mass index (BMI) ≥ 16 kg/m² to ≤ 28 kg/m² at screening;
3. Diagnosed with systemic lupus erythematosus (SLE) per 1997 ACR criteria or 2019 EULAR/ACR classification criteria;
4. Positive antinuclear antibody (titer ≥ 1:80) and/or anti-dsDNA antibody and/or anti-Sm antibody at screening;
5. Histologically confirmed active lupus nephritis (LN) class III or IV ± class V by renal biopsy, per 2018 International Society of Nephrology/Renal Pathology Society (ISN/RPS) standards within 1 year preceding or during screening.

Exclusion Criteria:

1. Received renal dialysis within 12 months preceding screening, or anticipated requirement for dialysis/renal transplantation within 6 months post-enrollment;
2. Renal biopsy demonstrating > 50% globally sclerosed glomeruli;
3. Active severe/unstable neuropsychiatric SLE (NPSLE);
4. Catastrophic antiphospholipid syndrome (APS) within 12 months pre-screening, or APS-related thrombotic events (except non-catastrophic/mild APS cases with stable anticoagulation ≥12 weeks prior to screening);
5. Non-LN renal diseases potentially confounding disease assessment (e.g., diabetic nephropathy per investigator judgment);
6. Inflammatory/autoimmune diseases beyond SLE/LN that may interfere with efficacy/safety interpretation.