Background: Among Systemic Lupus Erythematosus (SLE) manifestations, Lupus Nephritis (LN) is pivotal given its high morbidity and mortality. 21% to 58% of patients will develop LN, which poses risks of renal decline and even death. Therefore, assessing LN treatment response is crucial to prevent damage.

Objectives: Primary objective: assess renal response (RR) at the end of LN induction therapy.

Secondary Objectives: evaluate RR rates at 12- and 24-months post-LN induction and identify prognostic factors for RR during induction in LN patients.

Methods: Review of records of 538 SLE patients diagnosed by 2019 European Alliance of Associations for Rheumatology (EULAR)/ American College of Rheumatology (ACR) criteria. 266 (49.4%) had renal involvement and 137 (25.5%) had LN (class III, IV, and/or V confirmed by renal biopsy or inferred by clinical features) between January 1, 2016, and December 1, 2021.

Of the 137 patients, 37 were excluded (treatment abandonment, lack of records, and non-compliance with recommended induction therapy). In total, 100 were selected for the evaluation of RR post- induction.

LN was defined per ACR 2012. Induction therapy: intravenous corticosteroid pulse (500-1,000 mg/day for 3 consecutive days) followed by an immunosuppressant [cyclophosphamide (CYC), mycophenolate mofetil (MMF), tacrolimus (TAC), tacrolimus combined with mycophenolate mofetil (multi-target), or rituximab (RTX)].CYC could be administered in fixed doses (500 mg every 15 days for 6 doses - low-dose CYC) or 0.5 to 1.0 g/m2 of body surface area once a month for 6 months (high-dose CYC). Induction lasted 6 months, except low-dose CYC (3 months), and corticosteroid doses were reduced gradually and all received antiproteinuric and antimalarials drugs.

After induction, all patients retested 24-hour urine protein, with effective response (ER) if ≤ 0.7 g of proteinuria in 24 hours.

Of 100 LN patients, 55 had data on 24-hour proteinuria, C3, C4, and anti-dsDNA at induction start, week 8, and end. Good prognosis if, by week 8, C3/C4 normalized, anti-dsDNA negative, and 25-50% reduction in 24-hour proteinuria.

Statistical analysis: descriptive stats, normality tests, Student’s t-test for normal distribution, Mann-Whitney U test for non-normal, chi-square/Fisher’s exact test for qualitative variables (p<0.05 considered significant), analyzed using commercial software.

Results: Among 538 SLE patients, 92.6% were female, predominantly mixed race (40.2%). Mean age at SLE diagnosis: 26.8 years, disease duration: 12.3 years. Common manifestations: joint (88.7%), cutaneous (88.1%), hematological (54.3%), renal (49.4%), and neurological (13.6%).

Of 266 SLE patients with LN, 100 (37.6%) had LN during the evaluated period, 92% were female, predominantly mixed race (50%). Induction regimens: low-dose CYC (36%), high-dose CYC (35%), MMF (22%), RTX (4%), and multi-target (3%). Clinical manifestations: joint (92%), cutaneous (82%), hematological (50%), serositis (26%), and neurological (10%).

Among 100 patients, 67 (67%) achieved ER. After 12 months, 57 (85.07%) maintained ER, 7 (10.45%) had maintenance failure (MF), and 3 (4.48%) discontinued follow-up. After 24 months, 56 (98.25%) maintained ER, with only 1 (1.75%) had MF.

Comparison between ER and failure group (FG) showed no statistical differences in gender, race, age at diagnosis, disease duration, or therapies used (p>0.005).

Initial proteinuria in 24 hours differed significantly (ER: 2.3 g, FG: 4.1 g, p=0.001), neurological involvement was less prevalent in ER (60% vs. 18,2%, p=0.015), as CNS involvement (4.5% vs. 15,2%, p=0.031).

In 100 LN patients, 55 had 8th-week records. Of these, 35 (63.6%) achieved ER. 8th-week mean proteinuria: ER 1.0g, FG 2.38g, p<0.001. Reduction: ER 47.7%, FG 32.0%, p=0.031. C3/C4 normalization was non-significant. Anti-dsDNA persistence at 8th week: ER 65.7%, FG 30%, p=0.013.

Conclusion: In conclusion, the study demonstrated a post-induction ER rate of 67%, surpassing literature expectations, and over 80% maintained remission for LN after 24 months. Key indicators for ER included achieving 1g proteinuria in 24 hours and ≥47.7% reduction by the 8th week.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: Stephanie Murgio Bibikoff GSK, Julia Brito de Medeiros: None declared, Dawton Yukito Torigoe Lily, Janssen, Abbvie, Gabriela Munhoz GSK