Abstract Number: PB/LB05
Meeting: ISTH 2020 Congress
Background: Primary immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder, characterized by a low platelet count in the absence of other causes for thrombocytopenia and is in most patients caused by pathogenic IgG.
Aims: Targeted reduction of autoantibodies through FcRn blockade by efgartigimod may prevent their pathogenic actions and this was further investigated in a Phase 2 clinical trial (NCT03102593).
Methods: Thirty-eight adult confirmed primary ITP patients with an average of ˂30×109/L platelets, were randomized 1:1:1 for 4 weekly intravenous infusions of placebo (N=12), efgartigimod 5 mg/kg (N=13) or 10 mg/kg (N=13), followed by 8-week follow-up, 13 weeks extended follow-up and a 1-year open-label treatment period with 10 mg/kg efgartigimod (N=12). Concurrent therapies at stable doses were permitted.
Results: Patients were predominantly refractory to previous lines of therapy (median disease duration 4.8 [0.1-47.8] years and 20 patients [52.6%] had baseline platelet count < 15×109/L) and had insufficient response to prior ITP therapy (e.g., 14 [36.8%] patients had previously received a TPO-RA of whom 10 were continuing a TPO-RA at baseline) or failed splenectomy (N=6 [15.8%]). Efgartigimod was safe, consistent with previous observations in Phase 1 (NCT03457649). A rapid reduction of total IgG levels was obtained (up to 63.7% mean change from baseline), which was associated with clinically relevant increases in platelet counts (46% patients on efgartigimod vs. 25% on placebo achieved a platelet count of ≥50×109/L on at least 2 occasions and 38% vs. 0% achieved ≥50×109/L for at least 10 cumulative days, Figure 1), and a reduced proportion of patients with bleeding (Figure 2). In the open-label treatment period, 8/12 patients achieved platelet count ≥50×109/L on at least 2 occasions.
Conclusions: Targeted IgG reduction with efgartigimod is a potential new treatment modality in primary ITP and warrants evaluation of longer-term treatment in a Phase 3 study (NCT04225156).
To cite this abstract in AMA style:Newland AC, Sanchez-Gonzalez B, Rejtő L, Egyed M, Romanyuk N, Godar M, Verschueren K, Gandini D, Ulrichts P, Beauchamp J, Dreier T, Ward S, Michel M, Liebman HA, de Haard H, Leupin N, Kuter D. Phase 2 Study of Efgartigimod, a Novel FcRn Antagonist, in Adult Patients with Primary Immune Thrombocytopenia [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/phase-2-study-of-efgartigimod-a-novel-fcrn-antagonist-in-adult-patients-with-primary-immune-thrombocytopenia/. Accessed January 27, 2022.
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