Inhibition of FcRn with rozanolixizumab in adults with immune thrombocytopenia: Two randomised, double‐blind, placebo‐controlled phase 3 studies and their open‐label extension.

Summary Primary immune thrombocytopenia (ITP) is an antiplatelet‐antibody‐mediated disorder with accelerated platelet clearance and decreased platelet production. Rozanolixizumab, a monoclonal IgG4 anti‐FcRn antibody, blocks IgG recycling and decreases IgG levels. We report efficacy and safety of rozanolixizumab in adults with persistent/chronic ITP in 24‐week phase 3 studies (TP0003; TP0006), and their 52‐week open‐label extension (OLE). Primary end‐point was durable clinically meaningful platelet response (DCMPR) of ≥50 × 109/L for 8/12 weeks during Weeks 13–25 in the double‐blind studies. Operational delays and evolving ITP treatment landscape led the sponsor to terminate these studies early; thus, only 21 and 12 (TP0003) and 20 and 10 (TP0006) patients were randomised to rozanolixizumab or placebo. Forty‐three patients enrolled in the OLE: 42 started on every 2‐week dosing; 21 later switched to weekly dosing. More rozanolixizumab‐treated than placebo‐treated patients achieved DCMPR: 4/21 versus 0 (TP0003) and 1/20 versus 0 (TP0006). Platelet increases to ≥50 × 109/L were observed on Day 8 in 52.4% (TP0003; 2/12 placebo) and 45.0% (TP0006; 1/10 placebo) of rozanolixizumab‐treated patients. OLE platelet increases were maintained while on weekly dosing. The most frequent treatment‐emergent adverse events overall were headache, pyrexia and nausea, as seen previously. Weekly dosing appears more efficacious than every 2‐week dosing. [ABSTRACT FROM AUTHOR]