POS1122 PRELIMINARY FINDINGS OF THE PROTECT CLINICAL TRIAL: PEGLOTICASE EFFICACY AND SAFETY IN KIDNEY TRANSPLANT RECIPIENTS

Background:The prevalence of gout is high in kidney transplant (KT) recipients (up to 13%), largely because of decreased kidney function and calcineurin inhibitor use.1 Residual chronic kidney disease (CKD) leading to decreased urate lowering therapy clearance and drug interactions make managing gout in KT recipients challenging. Studies show that successful treatment with pegloticase, a pegylated uricase, leads to marked reductions in serum uric acid (sUA)2 and a subsequent decrease in overall urate load and tophi burden.3 However, pegloticase use in solid organ transplant recipients has not been systematically studied or well-characterized in the literature.4,5Objectives:To examine the safety and efficacy of pegloticase in KT recipients with uncontrolled gout.Methods:This ongoing multicenter, open-label, efficacy and safety study of pegloticase in KT recipients (NCT04087720) included patients with uncontrolled gout sUA ≥7 mg/dL, urate lowering therapy [ULT] contraindication/inefficacy, and with either visible tophi, chronic gouty arthritis, or ≥2 flares in past year, who were KT recipients (KT >1 year prior), had a functioning graft (estimated glomerular filtration rate [eGFR] ≥15 ml/min/1.73m2), and were on a stable immunosuppressant regimen. Pegloticase (8 mg infusion) was administered biweekly for 24 weeks (12 infusions) followed by a safety visit 30 days after the last infusion and 3-month post-treatment follow up visit. The primary endpoint was proportion of patients who were serum uric acid responders during Month 6 (sUA <6 mg/dL for ≥80% of time). Change from baseline (CFB) at 24 weeks was also evaluated for sUA, renal function, and health assessment questionnaire (HAQ) disability index (DI, maximum = 3) and pain (maximum = 100).Results:Preliminary findings of this study included 15 patients (12 male, 53.5±11.0 years of age) with uncontrolled gout (6.2±6.0 years since diagnosis) who had received a donor kidney 15.1±6.6 years earlier. At the time of analysis, 5 patients had completed the 24-week treatment period and 8 remained on therapy (last visit sUA <0.1 mg/dL in 6 patients, 1 had sUA of 7.4 mg/dL, 1 only received first infusion), and 2 had discontinued treatment (sUA rise [n=1], COVID-19 concerns [n=1]). Of the 5 patients who completed 24 weeks of therapy, all met response criteria and sUA was below detection limits (CFB: -10.2±1.3 mg/dL, baseline [BL]: 10.2±1.3 mg/dL). Patients also had less pain (HAQ-pain CFB: -33.6±22.2, BL: 35.9±22.0; n=5) and disability (HAQ-DI CFB: -0.3±0.6, BL: 0.7±0.8; n=5) at 24 weeks compared to BL. eGFR remained stable during 24 week treatment (eGFR CFB: -0.2±6.3 ml/min/1.73 m2, BL: 40.9±14.4 ml/min/1.73 m2; n=5). Urine albumin-to-creatinine ratio showed improvement at 24 weeks (CFB: -223±405 mg/g, BL: 664±870 mg/g; n=5). 80% of patients experienced an AE, and 4 SAEs (duodenal ulcer, cellulitis, dyspnea, skin bacterial infection) deemed unrelated to pegloticase were reported. AEs that occurred in >1 patient included gout flare, pyrexia, arthralgia, and nasal congestion. No anaphylaxis or infusion reactions occurred.Conclusion:Initial findings suggest that pegloticase therapy is effective at reducing sUA in most KT recipients while preserving renal function. Results suggest that in the setting of profound urate lowering with pegloticase in KT patients, eGFR remains stable and patients experience clinically beneficial reductions in pain and disability with an absence of unexpected safety findings.References:[1]Clive DM. J Am Soc Nephrol 2000;May11(5):974-9.[2]Sundy JS, et al. JAMA 2011;306:711-720.[3]Mandell BF, et al. Arthritis Res Ther 2018;20:286.[4]Freyne B. Transplant Proc 2018;50:4099-101.[5]Hershfield MS, et al. Arthritis Res Ther 2014;16:R63.Disclosure of Interests:Abdul Abdellatif Speakers bureau: Horizon Therapeutics plc, Consultant of: Horizon Therapeutics plc, Lin Zhao Shareholder of: Horizon Therapeutics plc, Employee of: Horizon Therapeutics plc, Paul M. Peloso Shareholder of: Horizon Therapeutics plc, Employee of: Horizon Therapeutics plc, Katya Cherny Shareholder of: Horizon Therapeutics plc, Employee of: Horizon Therapeutics plc, Brad Marder Shareholder of: Horizon Therapeutics plc, Employee of: Horizon Therapeutics plc, John Scandling Consultant of: Horizon Therapeutics plc, Kenneth Saag Consultant of: Arthrosi, Atom Bioscience, Horizon, LG Pharma, Mallinkrodt, SOBI, Takeda, Grant/research support from: Horizon, SOBI, Shanton.

THU0408 EFFECT OF NEW-ONSET GOUT ON KIDNEY TRANSPLANT OUTCOMES: A RETROSPECTIVE COHORT ANALYSIS OF THE UNITED STATES RENAL DATA SYSTEM

Background:Gout is a frequent comorbidity in kidney transplant (KT) recipients. However, assessing the independent effect of gout on KT outcomes is difficult because of multiple confounders (e.g., temporal changes in estimated glomerular filtration rate [eGFR], cyclosporine or tacrolimus dose, urate-lowering medication use) that obscure a clear picture of gout’s potential impact.Objectives:This investigation assessed if the development of new-onset gout after KT was an independent risk factor for loss of graft function, as assessed by the need for maintenance hemodialysis following KT.Methods:This retrospective cohort study analyzed data on patients in the United States Renal Data System (USRDS) who received a primary KT between 1/1/2008 and 12/31/2015. The date of transplantation was the ‘index’ date. Eligible patients were required to have ≥24 months of Medicare coverage and no prior history of gout, defined as ≥1 claim with a gout diagnosis code in the 24 months prior to the index date. All patients were also required to have ≥12 months of coverage post index. Patients who died, experienced graft failure, or returned to dialysis <12 months post index were excluded. Because the first year following transplant is associated with the highest frequency of rejections, we evaluated subjects beginning 1 year after transplant. The exposure of interest was new-onset gout, defined as the presence of ≥2 claims for gout post index, and the primary endpoint was return to dialysis >12 months post index. Baseline time-invariant confounders included recipient and donor demographics and clinical characteristics at index. Time-varying confounders included body mass index (BMI) adjusted tacrolimus and cyclosporine dose, eGFR, and urate-lowering medication use post index. Patients who died or lost Medicare coverage >12 months post index were censored; all patients remaining at the end of the study period (12/31/2016) were also censored. A marginal structural model (MSM) was fitted to determine the relative risk of new-onset gout on return to dialysis, while controlling for both time-invariant and time-varying confounders.Results:18,525 of 466,589 KT recipients in the USRDS met study eligibility. Within the observation period, 1,399 (7.6%) developed new-onset gout and 1,420 (7.7%) returned to dialysis >12 months post index. Median time from index to new-onset gout and from index to return to dialysis was 16.2 months (IQR: 33.4) and 32.8 months (IQR: 28.4), respectively. Adjusting for baseline time-invariant and time-varying confounders via the MSM showed new-onset gout was associated with a 51% increased risk of return to dialysis >12 months post index (RR: 1.51, 95% CI: 1.03, 2.20).Conclusion:New-onset gout was independently associated with a 51% increased risk of return to dialysis >12 months after primary KT compared to a control cohort without gout. To our knowledge, this is the first observation of this outcome in an appropriately controlled cohort study of KT recipients with gout. Results from this analysis may have important implications for the monitoring and management of new-onset gout in the kidney transplant population.References:[1]Mandell BF.Cleve Clin J Med2008;75(Suppl 5):S5-8.[2]Forbess LJ, Fields TR.Sem Arthritis Rheum2012;42:146-54.[3]Gibson T.Curr Opin Rheumatol2012;24:127-31.[4]Zhang L, et al.Nephrol Dial Transplant2012;27:1836-9.[5]Clive DM.J Am Soc Nephrol2000;11:974-9.[6]Kalantar E, et al.Transplant Proc2011;43:584-5.[7]Lin HY, et al.N Engl J Med1989;321:287-92.[8]Ben Hmida M, et al.Transplant Proc1995;27:2722-4.[9]Kanbay M, et al.Transplant Proc2005;37:3119-20.[10]Baroletti S, Bencivenga GA.Prog Transplant2004;14:143-7.[11]Kim ED, et al.Am J Transplant2015;15:482-8.[12]Kim DG, et al.PloS One2018;13:e0209156.Disclosure of Interests: :Justin Li: None declared, David Yin: None declared, Zheng Wang: None declared, Mark Brigham: None declared, Brian LaMoreaux Shareholder of: Horizon Therapeutics, Employee of: Horizon Therapeutics, Jeffrey Kent Shareholder of: Horizon Therapeutics, Employee of: Horizon Therapeutics, Megan Francis-Sedlak Shareholder of: Horizon Therapeutics, Employee of: Horizon Therapeutics, Richard Johnson Shareholder of: Colorado Research Partners LLC, XORTX Therapeutics, Consultant of: Horizon Therapeutics, Eli Lilly, Speakers bureau: Horizon Therapeutics, Nandini Hadker: None declared, Kevin Francis: None declared, Herman Sanchez: None declared, Gavin Miyasato: None declared

Intrahepatic bile duct variation: MR cholangiography and implication in hepatobiliary surgery

Background The aim of this study was to assess the prevalence of biliary anatomical variants using 3-T MR cholangiography (MRC) with its impact in reduction of the complication of hepatobiliary surgical techniques. Results MRC was applied to 120 subjects (24 potential liver donors and 96 volunteers) and the right posterior hepatic duct insertion was documented, and accordingly, the biliary variants were classified based on Huang classification (Huang et al, Transplant Proc 28: 1669–1670, 1996). Biliary anatomic variants were divided based on Huang classification: Huang A1, 65.83% (n = 79); Huang A2, 11.67% (n = 14); Huang A3, 13.3% (n = 16); Huang A4, 7.5% (n = 9); and Huang A5, 1.67% (n = 2). The total frequency for A2, A3, A4, and A5 was 34.17% (n = 41). The distance between RPHD insertion and the junction of right and left hepatic ducts (L) was measured, and Huang A1 cases were then subtyped into S1 subtype (L > 1 cm) and S2 subtype (L ≤ 1 cm). We had 52 subjects with subtype S1 (43.33%) and 27 subjects with subtype S2 (22.5%). Twenty-three subjects had bile duct exploration or intraoperative cholangiograms and showed Huang type A1 in 14 (60.87%), type A2 in 3 (13.05%), and type A3 in 6 (26.08%). Twenty-two (95.65%) had the same classification in MRC and intraoperative while only one case (4.35%) was considered as A2 at MRC but the intraoperative classification was Huang A3, which was attributed to the insertion of the RPHD insertion at the distal end of the left hepatic duct. Conclusion MRC is an accurate tool for biliary tract mapping before hepatobiliary surgery to provide excellent identification of biliary variants which can reduce the incidence of biliary complications.

A Novel Crosstalk Between Iron Homeostasis and mTOR Mediated By the Immunophilin FKBP12

Introduction Hepcidin, the liver hormone that regulates iron homeostasis, is mainly activated via the BMP/SMAD pathway. Among other stimuli, as erythropoiesis expansion, inflammation and hypoxia, hepcidin expression is influenced by drugs, including the mTOR inhibitor rapamycin (RAPA) (Mleczko-Sanecka et al., Blood 2014). In the liver, BMP type I receptors, ALK2 and ALK3, are both essential for hepcidin regulation (Steinbiecker et al., Blood 2012), whereas BMP type II receptors, BMPR2 and ACVR2A, have a redundant role (Mayeur et al., Blood 2014). The signaling is activated when BMP type II receptors phosphorylate residues of the glycine/serine rich (GS) domain of BMP type I receptors, which then activate SMAD1/5/8. Treatment with RAPA increases hepcidin expression in murine hepatocytes and may cause microcytic anemia in patients (Przybylowski P. et al., Transplant Proc. 2013). However, the mechanisms involved in hepcidin and mTOR crosstalk are unknown. Methods Hepcidin, BMP-SMAD and mTOR target genes were analyzed in human hepatoma cell lines and murine primary hepatocytes (HCs), treated with RAPA (100 nM), Torin1 (100 nM), tacrolimus (TAC, 1 μg/ml) in the presence or absence of the BMP pathway inhibitor DMH1 (0.5 μg/ml) or of the ligands BMP6, BMP2, Activin B (ActB) and Activin A (ActA) (1-100 ng/ml). ALK2wt was mutagenized in the GS domain (R206H, Q207E) or close to the GS domain (R258S) to generate ALK2mut with reduce binding to FKBP12 (Taylor et al., Cancer Res. 2014). SMAD1/5/8 phosphorylation was analyzed by Western Blotting in cells transfected with SMAD1 and ALK2wt or ALK2mut and treated or not with TAC, BMP6 and ActA. Binding of FKBP12 to ALK2wt and ALK2mut was assessed by coimmunoprecipitation of tagged proteins in transfected cells treated as above. Eight weeks old C57BL/6 wild type male mice were treated with a single dose of TAC (10 mg/kg) or vehicle and sacrificed at different time points (3-18 hrs). Hepcidin expression, LIC, SIC, serum iron and hematological parameters were analyzed by standard methods. Results We analyzed hepcidin expression in hepatoma cells and primary HCs treated with RAPA, an inhibitor of mTORC1, and Torin1, an ATP-competitive inhibitor of mTORC1 and 2. Hepcidin is increased by RAPA, but not Torin1, in a SMAD1/5/8 dependent way since DMH1 abrogates the effect. RAPA inhibits mTORC1 when complexed with FKBP12, an immunophilin that binds BMP receptors to avoid leakage activation of the pathway. To investigate whether hepcidin upregulation by RAPA is mediated by FKBP12 sequestration, we used genetic and pharmacologic approaches. First, we confirmed by coimmunoprecipitation that ALK2mut have a reduced ability to bind FKBP12. Then we transfected hepatoma cells with ALK2wt and ALK2mut and analyzed hepcidin and BMP pathway activation. Overexpression of ALK2mut increases hepcidin through SMAD1/5/8 as shown by high levels of SMAD1 phosphorylation, an effect abrogated by DMH1. Second, we treated hepatoma cells and primary HCs with TAC, a calcineurin inhibitor that binds FKBP12. This treatment increases hepcidin through SMAD1/5/8, suggesting a mechanism shared with RAPA. The same effect is observed in vivo since hepcidin is increased at 6 hrs post-injection in TAC-treated wt mice. Our results identify FKBP12 as a novel regulator of hepcidin. In addition, FKBP12 displacement alters the BMP receptor selectivity to ligands. Despite ALK2wt preferentially binds BMP6, ALK2mut become responsive to ActA, a TGF-β ligand that signals through SMAD2/3. Hepcidin activation by BMP6, BMP2 and ActB is comparable in ALK2wt and ALK2mut expressing cells. However, ActA upregulates hepcidin (through SMAD1/5/8) only in ALK2mut transfected cells. This effect is due to the impaired ability of ALK2mut to bind FKBP12, since it is observed even in ALK2wt transfected cells pretreated with TAC. Conclusions FKBP12 contributes to hepcidin regulation both in vitro and in vivo, thus adding a new player to the BMP-dependent hepcidin activation and a potential pharmacologic target for disorders characterized by low hepcidin and iron overload. Furthermore the ability of ALK2 to respond to Activin A, which is released in inflammation, links the BMP pathway-hepcidin activation to the inflammatory response. Disclosures No relevant conflicts of interest to declare.

Novel Additive Solution "Aayusol" Significantly Preserves Platelets in Lesion-Free State during Extended Storage

Introduction: We have recently demonstrated that hearts can be stored in a novel organ preservation solution Somah (Thatte HS et al, Circulation 2009), for an extended 24-hour period at ambient temperature, creating new paradigms in transplant surgery (Lowalekar SK et al, Transplant Proc 2013; Am J Transplant 2014). Somah was significantly modified to address the peculiarities of platelet biochemistry and metabolism, resulting in a novel platelet additive solution, Aayusol, that preserves platelets in a relatively lesion free state compared to PAS-IIIM during 9-day storage at ambient temperature. Methods: Platelets (20% PRP) were stored in transfer bags containing Aayusol or PAS-IIIM solution (20:80) at ambient temperature with gentle shaking under aseptic conditions. Immuno-Biochemical assays, flow cytometry, and semi-quantitative confocal microscopy were utilized to evaluate platelet viability and function (n=8) during 9-day storage. Results: The pH levels of both PASIIIM and Aayusol remained stable above 7.1 throughout 9-day storage. Significantly greater amount of platelet microparticles and aggregates were temporally formed, which peaked in PAS-IIIM (>8% & >4%) but not in Aayusol (<3% & <1.3%; *P < 0.05), at day 9 respectively (Figure 1 and Figure 2A and 2B). In contrast to PAS-IIIM platelets, Aayusol platelet morphology was well preserved during storage. Similarly, activation markers- PS exposure and P-selectin expression- (<15%) and (<5%) respectively, were significantly attenuated in Aayusol platelets, but not in PAS-IIIM at 9-day storage (Figure 2C and 2D). Furthermore, GPIba and GPIIb surface receptors, responsible for primary adhesion of circulating platelets to the thrombogenic surface, shed faster and decreased significantly in PAS-IIIM than in Aayusol at 9-day storage (GPIba: 30% vs. 60% and GPIIb: 40% vs. 60%; P < 0.05). Additionally, nitric oxide production was well preserved in Aayusol platelets, with NO fluorescence dye quantum yield of 190 units, which was significantly greater than the comparator, which yielded 105 units, at the end of storage (Figure 2E). As components in Aayusol specifically help modulate aerobic and anaerobic metabolism, lactic acid production was significantly lower in Aayusol (2.8±1.82 mmol/L) than in PAS-IIIM (3.9±0.32 mmol/L; P < 0.05). Correspondingly, high-energy phosphate synthesis (ATP+CP) was greater in Aayusol platelets compared to PAS-IIIM platelets. Temporal agonist (ADP and A23187) challenge resulted in greater activation of Aayusol platelets (over 70% PS and P-selectin expression) than PAS-IIIM (60% PS and 20% P-selectin; P < 0.05) on day 9 storage. Conclusion: Temporally assessed parameters showed superiority of Aayusol platelets compared to PAS-IIIM platelets. Therefore, based on conservation of structure and function, Aayusol platelet transfusion requirement will potentially be lower than PAS-IIIM platelets, thus increasing the availability of platelets to meet demand, with decreased costs and morbidity in patients. Thus, Aayusol may provide a more viable means of preserving platelets for transfusion. Disclosures No relevant conflicts of interest to declare.

Expansion and tissue infiltration of an allospecific CD4+CD25+CD45RO+IL-7Rαhigh cell population in solid organ transplant recipients

It has been recently shown (Seddiki, N., B. Santner-Nanan, J. Martinson, J. Zaunders, S. Sasson, A. Landay, M. Solomon, W. Selby, S.I. Alexander, R. Nanan, et al. 2006. J. Exp. Med. 203:1693–1700.) that the expression of interleukin (IL) 7 receptor (R) α discriminates between two distinct CD4 T cell populations, both characterized by the expression of CD25, i.e. CD4 regulatory T (T reg) cells and activated CD4 T cells. T reg cells express low levels of IL-7Rα, whereas activated CD4 T cells are characterized by the expression of IL-7Rαhigh. We have investigated the distribution of these two CD4 T cell populations in 36 subjects after liver and kidney transplantation and in 45 healthy subjects. According to a previous study (Demirkiran, A., A. Kok, J. Kwekkeboom, H.J. Metselaar, H.W. Tilanus, and L.J. van der Laan. 2005. Transplant. Proc. 37:1194–1196.), we observed that the T reg CD25+CD45RO+IL-7Rαlow cell population was reduced in transplant recipients (P &lt; 0.00001). Interestingly, the CD4+CD25+CD45RO+IL-7Rαhigh cell population was significantly increased in stable transplant recipients compared with healthy subjects (P &lt; 0.00001), and the expansion of this cell population was even greater in patients with documented humoral chronic rejection compared with stable transplant recipients (P &lt; 0.0001). The expanded CD4+CD25+CD45RO+IL-7Rαhigh cell population contained allospecific CD4 T cells and secreted effector cytokines such as tumor necrosis factor α and interferon γ, thus potentially contributing to the mechanisms of chronic rejection. More importantly, CD4+IL-7Rα+and CD25+IL-7Rα+ cells were part of the T cell population infiltrating the allograft of patients with a documented diagnosis of chronic humoral rejection. These results indicate that the CD4+CD25+IL-7Rα+ cell population may represent a valuable, sensitive, and specific marker to monitor allospecific CD4 T cell responses both in blood and in tissues after organ transplantation.