Pos0260 Once-Monthly Sel-212 Demonstrates Efficacy and Safety for Up to 6-Months in Gout Refractory to Conventional Therapy: Combined Data From the Dissolve I & Ii Phase 3, Double-Blind, Placebo-Controlled Clinical Trials

Background: In gout refractory (RG) to conventional uric acid lowering therapy (ULT), sustained hyperuricemia increases the risk of painful flares, chronic gouty arthropathy, and tophi. Uricase-based therapy can effectively reverse these outcomes but is limited by immunogenicity, which impairs efficacy and compounds the risk of infusion reactions. SEL-212 is a novel, once-monthly therapeutic platform that consists of sequential infusions of immune-tolerising nanoparticles containing sirolimus (SEL-110), followed by a pegylated uricase (pegadricase, SEL-037). DISSOLVE I 23.0% (20/87) and 43.2% (38/88) in the HD and LD arms, respectively, met the stopping rule. Other key reasons for discontinuation in the HD, LD and placebo arms, respectively, were withdrawal of consent (10.3%, 8.0%, and 8.9%) and adverse events (13.8%, 6.8%, and 2.2%). Baseline characteristics were largely similar across arms (Table 1). The primary endpoint (response rate, RR), defined as sUA levels Figure 1). In those with tophi at baseline, SEL-212 RRs (HD: 41%; LD 43%) were significantly different from placebo (9%; p=0.0003 and 0.0002, respectively; Figure 1). Mean absolute (percentage) sUA reductions from baseline were 5.3 mg/dL (60.8%) for HD, 4.5 mg/dL (52.2%) for LD, and 0.3 mg/dL (2.1%) for placebo (pConclusion: Combined DISSOLVE I 82(suppl 1):200-201 (abstract LB0002). 2 Baraf HSB, et al. Arthritis Rheumatol. 2023;75(suppl 9): abstract number 0246. Acknowledgements: The DISSOLVE I & II (NCT04513366 and NCT04596540) studies were jointly funded by Sobi and Selecta BioSciences, Inc and this publication was funded by Sobi. Disclosure of Interests: Herbert S.B. Baraf Horizon Pharmaceuticals, Fresenius Kabi, Grunenthal, Olatec, SElecta BioSciences and Sobi, Horizon Pharmaceuticals, Sobi, Puja Khanna Horizon Pharmaceuticals, Sobi, Dyve Biosciences, Selecta Biosciences, Anand Patel Lexicon Pharmaceuticals, Atul Singhal: None declared, Joanna Sobierska Sobi, Hugues Santin-Janin Sobi, Rehan Azeem Selecta Biosciences, Sobi, Wesley DeHaan Selecta Biosciences, Sobi, Peter Traber Selecta Biosciences, Sobi, Alan Kivitz AbbVie, Eli Lilly, Flexion, GSK, Sanofi-Regeneron, Amgen, GKS, Gilead, Novartis, Pfizer, AbbVie, Chemocentryx, Coval, ECOR1, Fresenius Kabi, Genzyme, Gilead, Grunenthal, GSK, HOrizon Pharmaceuticals, Janssen, Prime, Prometheus, Selecta, Synact, Takeda-Nimbus, UCF, XBiotech.