survival, frequency of rejection or haematological complications. However, KTMG patients with an abnormal kappa/lambda ratio at the time of KT tended to have poorer overall survival than those with normal kappa/lambda ratio and controls (respective medians 72, 87 and 103 months; P = 0.08) (Figure 2). CONCLUSION: We report here the largest cohort of KT recipients who underwent systematic SPEP screening at the time of KT and yearly during post-transplant follow- up. We observed that MGUS prevalence in KT candidates is close to that reported in the general population. We confrm that outcomes of patients harboring MGUS at the time of KT are similar to those of matched controls without MGUS, supporting that MGUS should not be a contraindication for KT. Nevertheless, we observed that KTMG patients developed more frequently and earlier solid cancers and infections, suggesting that MGUS is associated with a relative immunodefciency in these patients. We also showed that patients with abnormal sFLC kappa/lambda ratio experienced poor outcomes, claiming for systematic measurement of sFLC in the pre-KT workup. Clinical last follow-up is represented by dots: red dot for death, blue dot for graft loss and green dot for last follow-up alive with functional graft. FC 115 LONG-TERM OUTCOMES IN ECULIZUMAB-TREATED KIDNEY TRANSPLANT PATIENTS ENROLLED IN THE GLOBAL ATYPICAL HAEMOLYTIC URAEMIC SYNDROME REGISTRY Maria Gema Ariceta Iraola 1 , Imad Al-Dakkak 2 , Katerina Anokhina 3 , Gianluigi Ardissino 4 , Laurence A. Greenbaum 5 , Gurinder Kumar 6 , Christoph Licht 7 , Andrew Siedlecki 8 and Johan Van de Walle 9 1 Hospital Universitari Vall d’Hebron, Barcelona, Spain, 2 Alexion Global & Regional Headquarters, Boston, MA, USA, 3 Alexion Pharma GmBH, Zurich, Switzerland, 4 Pediatric Nephrology, Dialysis and Transplantation Unit, Center for HUS Control, Prevention and Management, Fondazione IRCCS Cà Granda Foundation Ospedale Maggiore Policlinico, Milano, Italy, 5 Emory University, Atlanta, GA, USA, 6 Department of Paediatrics, Sheikh Khalifa Medical City, Abu Dhabi, UAE, 7 The Hospital for Sick Children, Toronto, Canada, 8 Department of Medicine, Brigham and Women’s Hospital, Boston, MA, USA and 9 Department of Paediatrics and Medical Genetics, Ghent University Hospital, Ghent, Belgium BACKGROUND AND AIMS: The global atypical haemolytic uraemic syndrome (aHUS) registry (NCT01522183), the largest repository of real-world data on patients with aHUS, provides key insights into disease course, natural history, and patient (pt) outcomes with and without complement inhibitor therapy. Prior to eculizumab availability, pts with aHUS had a reportedly high risk of disease recurrence and graft loss following a kidney transplant (KTx). We report the long-term clinical outcomes of eculizumab-treated pts who received a KTx. METHOD: This analysis included pts enrolled from April 2012–November 2021. Pts were included in a long-term treatment outcomes study if they had ever been treated with eculizumab and were excluded if they had DGKE mutations or their diagnosis was later revised to any condition other than aHUS. The current analysis set included pts who had received a KTx no more than 30 days prior to eculizumab start or up to 60 days post eculizumab start date, had ≥3 years of follow-up (FU) post-transplant and had serum creatinine (SCr) measurements at baseline (BL) and post 3 years FU. Changes in kidney function, haematological parameters and clinical characteristics at last follow-up (LFU) were assessed. RESULTS: A total of 329/1970 adult and paediatric registry pts met the inclusion criteria and received a KTx; 78 pts from 12 countries met sub-group inclusion criteria. BL demographics are shown in Table 1. Mean (SD) treatment duration was 5.7 (2.4) years and 47 (60%) pts had pathogenic genetic variants. Lab parameters at BL (closest measurement at or following KTx) and LFU are reported in Table 2. Despite large ranges, median SCr levels remained stable at LFU. Median eGFR and platelet levels were similar at BL and LFU, while lower median lactose dehydrogenase levels were seen at LFU. At LFU: four pts (5%)—three adult—had subsequent KTx(s); eight (10%)—seven adults—had received dialysis by last observation; and two (3%) had received plasma exchange/infusion. Two pts (3%) died during the observation period. CONCLUSION: This study assessed a large, real-world population of pts at high risk of KTx failure. Lab parameters suggest most pts beneftted from eculizumab treatment, with few TMA-related complications and stable kidney function and haematological parameters for ≥3 years. Overall, the proportions of female pts and of pts with pathogenic genetic variants were consistent with previous studies. A potential study limitation was the relatively stringent sub-population-specifc inclusion criteria. However, these data further demonstrate the benefcial impact of eculizumab treatment in the long-term management of aHUS in pts requiring KTx. Table 1. Patient demographics and characteristics at aHUS onset Characteristic All, N = 78 Paediatric a ,n = 25 Adult a ,n = 53 Age, years; median (min–max) 28 (0, 70) 3 (0, 17) 33 (19, 70) Female 43 (55) 6 (24) 37 (70) Treatment duration, years; mean (SD) 5.7 (2.4) 6.6 (2.3) 5.3 (2.3) Any pathogenic variant 47 (60) 15 (60) 32 (60) No pathogenic variants when tested for more than or equal to five complement genes b 17 (22) 4 (16) 13 (25) Anti-CFH antibody 12 (15) 3 (12) 9 (17) No anti-CFH antibody 45 (58) 16 (64) 29 (55) Data: n (%) unless otherwise specifed. a Based on age at onset. b Gene panel included complement C3 and CD46, factors H, I and B, and thrombomodulin. Table 2. Laboratory parameters and clinical characteristics at BL and LFU All Paediatric Adult Variable BL LFU BL LFU BL LFU Serum creatinine μmol/L 114 (34–903) 113 (56–1282) 106 (34–796) 122 (56–718) 123 (55–903) 110 (60–1282) eGFR mL/min/1.73 m 2 58 (5–130) 61 (3–136) 65 (6–130) 62 (8–136) 53 (5–113) 56 (3–115) Platelet count x10 3 /μL 222 (22–407) 221 (97–414) 259 (98–374) 245 (108–414) 211 (22–407) 217 (97–343) Lactate dehydrogenase U/L 215 (110–1126) 188 (128–1106) 265 (110–931) 222 (128–1106) 195 (123–1126) 185 (143–315) Thrombotic microangiopathy complications a — 1.5 (1–6) — 1 (14) — 2 (1–6) Kidney transplants a , n (%) — 4 (5) — 1 (4) — 3 (6) Dialysis a , n (%) — 8 (10) — 1 (4) — 7 (13) Plasma exchange/infusion a , n (%) — 2 (3) — 0 — 2 (4) No. deaths b , n (%) — 2 (3) — 1 (4) — 1 (2) Data: median (min–max) unless specifed. a By end of observation. b From treatment initiation. 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