Sustained response off-treatment in eltrombopag-treated adult patients with ITP who are refractory or relapsed after first-line steroids: Primary, final, and ad-hoc analyses of the Phase II TAPER trial

Abstract

Immune thrombocytopenia (ITP) is characterized by reduced platelet count due to increased destruction and is categorized according to the time following diagnosis (newly diagnosed, persistent, chronic). First-line corticosteroid therapy is associated with transient response, high relapse rates, and considerable toxicity. TAPER (NCT03524612) is a Phase II, prospective, single-arm trial investigating whether eltrombopag can induce a sustained response off-treatment (SRoT) in adult patients with ITP after first-line corticosteroid failure. This study defines SRoT as an off-treatment period wherein platelet count remains above 30 × 10⁹ /L in the absence of bleeding or rescue therapy. The primary endpoint was the proportion of patients who achieved SRoT until Month 12, which was 30.5% (n = 32/105; p < .0001 testing hypothesis H1: proportion >15%) following eltrombopag tapering and discontinuation, and median SRoT duration was ~8 months until Month 12. Median platelet count increased within 1 month of treatment and remained elevated until Month 12. Quality of life improved within 3 months and was maintained. Headache (21%) was the most common adverse event. None of the 4 deaths reported were considered treatment-related. In summary, ~one-third of patients achieved SRoT until Month 12 following eltrombopag tapering and discontinuation. An ad-hoc early-use analysis, stratified by ITP duration at baseline, assessed initial hematologic responses and safety. Results suggest that eltrombopag has similar efficacy in newly diagnosed and later stages of ITP. In follow-up until Month 24, a median SRoT duration of ~22 months was observed (n = 20). The safety profile was comparable across analyses and ITP duration groups and aligned with its well-established safety profile.