Phase II study of avatrombopag in thrombocytopenic patients with cirrhosis undergoing an elective procedure

Background & Aims This is a phase II multicentre study to investigate the efficacy and safety of avatrombopag (E5501), an investigational second-generation thrombopoietin receptor agonist, administered one week prior to elective procedures in patients with thrombocytopenia secondary to cirrhosis. Methods Adults with cirrhosis and platelet counts ≥10 to ≤58 × 10⁹/L were randomized to placebo or avatrombopag in two sequential cohorts. Cohort A: placebo vs. one of 3 different doses (100 mg loading dose followed by 20, 40, or 80 mg/day on days 2-7) of a first-generation avatrombopag formulation. Cohort B: placebo vs. one of 2 different doses (80 mg loading dose followed by 10 mg/day for days 2-7, or 20 mg/day for days 2-4) of a second-generation avatrombopag formulation. Primary end point was achievement of a platelet increase of ≥20 × 10⁹/L from baseline and >50 × 10⁹/L at least once during days 4-8. Results A total of 130 patients were randomized: 93 patients (51, cohort A; 42, cohort B) to avatrombopag and 37 (16, cohort A; 21 cohort B) to placebo. The primary end point was achieved by 49.0% of treated patients in cohort A and 47.6% in cohort B compared to 6.3% and 9.5% of controls; a dose response was seen. Each avatrombopag regimen had a higher proportion of responders compared with their respective cohort placebo arms (p <0.01), except for the 100/40 mg group in cohort A (p = 0.17). The most common adverse events were nausea, fatigue, and headache. One patient in the (100/80) avatrombopag group, without a Doppler assessment at screening was diagnosed with portal vein thrombosis during post-treatment follow-up. Conclusions In this study avatrombopag was generally well-tolerated and increased platelet counts in patients with cirrhosis undergoing elective invasive procedures.