094 Characterisation of the immunogenicity of spesolimab in patients with a generalized pustular psoriasis (GPP) flare

We investigated the immunogenicity of spesolimab, and its impact on PK, efficacy, safety in patients with a GPP flare. Plasma samples were analysed from three trials. In trial 1 (proof concept, NCT02978690), 7 received IV spesolimab 10 mg/kg. 2 (Effisayil 1, NCT03782792), 53 randomised 2:1 to receive 900 mg or placebo Day optional open-label (OL) 8 for persistent flare symptoms. At Week 12, could enroll into 3 ON, NCT03886246), 5-year OL extension, SC 300 Q12W Q6W; interim data are reported (N=39; September 2021). trials 3, additional new ADA available 56 spesolimab-treated (trial 6; 2, 50; 36 2). formed median onset 2.3 weeks; 24% (12/50) had an titer >4000 neutralising antibody-positive by Weeks 12–17. Higher responses (ADA >4000) seen females (30%; 10/33) compared males (12%; 2/17). There was no PK titers <4000, but plasma concentrations reduced significantly at >4000. Spesolimab efficacy similar ADA-positive ADA-negative up 12. Impact ADAs upon retreatment after 12 is be determined, as 77% (30/39) did not have 3. correlation between hypersensitivity reactions. Treatment led development maximum limited proportion minimal retreatment.