POS0702 PREGNANCY IN SLE PATIENTS TREATED WITH BELIMUMAB: EXPERIENCE FROM 3 ITALIAN CENTERS

Background:Belimumab (BEL) is a monoclonal antibody approved for SLE treatment but few data are available about its use before or during pregnancy.Objectives:Our study aims to describe pregnancies in SLE patients who have discontinued BEL before conception, at positive pregnancy test or during pregnancy.Methods:Data from prospectively-followed pregnancies (2014-2020) in SLE patients treated with BEL in 3 Italian centers where retrospectively collected, focusing on maternal disease activity, obstetric and neonatal outcome. Continuous data are expressed as median [min-max].Results:Thirteen SLE pregnancies were analyzed (median age at conception 32 [24-41] years; 77% spontaneous, 69% primigravidae). All patients had positive ANA and anti-dsDNA antibodies; 4 had anti-Ro antibodies (31%); 4 had anti-phospholipid antibodies (aPL; 1 single, 2 double and 1 triple positivity). Seven patients (54%) had a history of lupus nephritis (LN); 2 patients (15%) had a concomitant diagnosis of antiphospholipid syndrome (1 thrombotic-APS and 1 thrombotic+obstetric-APS).Ten (77%) pregnancies were planned and the use of BEL with regard to pregnancy was agreed with the patient during preconception counseling. At preconception visit, 8 patients were in remission while 5 had active disease (median SLEDAI 3 [0-8]).BEL (11 intravenous, 2 subcutaneous) was stopped in 2 cases before conception, in 7 at positive pregnancy test and in 4 during pregnancy (2 at 11th week, 1 at 22nd, 1 at 24th); median duration of treatment at discontinuation was 29 [4-68] months. Other treatments during pregnancy were: oral prednisone in 12 cases (92%); intravenous methylprednisolone in 1 (8%); hydroxychloroquine in 10 (77%); chloroquine in 1 (8%); azathioprine in 5 (39%); calcineurin inhibitors in 5 (39%); low-dose acetylsalicylic acid in 10 (77%); low molecular weight heparin in 9 (69%).Three flares occurred during the 3rd trimester in patients who stopped BEL at positive pregnancy test.Live-births occurred in 92% of the pregnancies. A patient with thrombotic+obstetric-APS and LN, underwent assisted reproductive technology (embryo donation) and developed eclampsia (25thweek), an urgent cesarean section was performed and the newborn died after 3 days. One pre-eclampsia occurred in a patient with history of LN, double aPL positivity and active disease. One miscarriage at 11th week occurred; no early miscarriages (<10th week) were recorded. Pregnancy complications and outcomes are reported in Table 1.Table 1.Pregnancy complications and outcomes according to the timing of discontinuation of BEL.BEL STOPPED PRECONCEPTIONALLY(2)BEL STOPPED AT POS PREGNANCY TEST(7)BEL STOPPED DURING PREGNANCY(4)Pre-eclampsia0/20/71/4 (25%)Eclampsia0/20/71/4* (25%)Gestational Diabetes0/21/7 (14%)0/4IUGR0/21/7 (14%)1/4* (25%)pPROM/PROM0/20/71/4 (25%)Live birth1/2 (50%)7/7 (100%)4/4 (100%)Severe pre-term birth(≤ 34thweek)0/20/71/4* (25%)Late pre-term birth(35th- 37thweek)0/23/7 (43%)0/4Small for Gestational age neonate0/24/7 (54%)1/4 (25%)Late miscarriage (>10thweek)1/2 (50%)0/70/4Perinatal death0/20/71/4* (25%)IUGR: IntraUterine Growth Restriction; PROM: Premature Rupture of Membrane; pPROM: pretermPROM; *in the same patient (history of thrombotic and obstetric-APS and lupus nephritis) who underwent Assisted Reproductive Technologies (embryo donation).No malformations were recorded. Two newborns were transferred to the Intensive Care Unit (1 for milk protein intolerance and 1 for desaturation).Eight newborns received vaccinations according to national schedule (missing data for 3). Five newborns were breastfed, 1 received formula milk and 5 mixed-feeding. BEL was resumed in 7/13 patients after pregnancy (in 4 cases for flare), after a median period of 5 [4-22] months.Conclusion:While more data are needed, this small series suggests that BEL might be a therapeutic option for SLE patients during pregnancy planning, similarly to other biological drugs used in chronic forms of arthritis.Disclosure of Interests:None declared