Anakinra for palmoplantar pustulosis: results from a randomized, double-blind, multicentre, two staged, adaptive placebo controlled trial (APRICOT).

Background Palmoplantar pustulosis (PPP) is a rare, debilitating, chronic inflammatory skin disease affecting the hands and feet. Clinical, immunological and genetic findings suggest a pathogenic role for interleukin (IL)-1. Objective To determine whether anakinra (an IL-1 receptor antagonist) delivers therapeutic benefit for PPP. Methods A randomised (1:1), double-blind, two-staged, adaptive, UK multi-centre, placebo-controlled trial. Participants had a diagnosis of PPP (>6 months) requiring systemic therapy. Treatment was eight weeks of anakinra or placebo via daily self-administered subcutaneous injections. The primary outcome was the Palmoplantar Pustulosis Psoriasis Area and Severity Index (PPPASI) at 8 weeks. Results A total of 374 patients were screened and 64 were enrolled (31 anakinra, 33 placebo) with mean baseline PPPASI 17.8 (SD=10.5); PPP investigator's global assessment severe (50%) or moderate (50%). The baseline adjusted mean difference in PPPASI favoured anakinra but did not demonstrate superiority in intention-to-treat analysis, -1.65, 95% CI [-4.77 to 1.47], p=0.300. Secondary objective measures including fresh pustule count (2.94, 95% CI [-26.44 to 32.33] favouring anakinra), total pustule count (-30.08, 95% CI [-83.20 to 23.05] favouring placebo), and patient-reported outcomes, similarly did not show superiority of anakinra. When modelling the impact of adherence, the PPPASI complier average causal effect (CACE) for an individual who receives ≥90% total treatment (48% anakinra group), was -3.80, 95% CI [-10.76 to 3.16], p=0.285. No serious adverse events occurred. Conclusions No evidence for superiority of anakinra was found. IL-1 blockade is not a useful intervention for the treatment of PPP.