Efficacy and safety of QL0911 in adult patients with chronic primary immune thrombocytopenia: A multicenter, randomized, double-blind, placebo-controlled, phase III trial.

Objective: QL0911, a recombinant human thrombopoietin mimetic peptide-Fc fusion protein, is a romiplostim (Nplate) biosimilar used to treat primary immune thrombocytopenia (ITP). This phase III study aimed to assess the efficacy and safety of QL0911 in adult patients with chronic primary ITP over a 24-week treatment period.

Methods: We conducted a double-blind, placebo-controlled, phase III study in patients diagnosed with primary ITP for at least 12 months who had received at least one first-line ITP treatment with no response or recurrence after treatment, or who relapsed after splenectomy at 44 sites in China. Patients were randomly allocated (2:1 ratio) to QL0911 or placebo injection subcutaneously once weekly at an initial dose of 1 μg/kg for 24 weeks. The doses were adjusted to maintain the target platelet counts from 50 × 109/L to 200 × 109/L. Patients and investigators were blinded to the assignment. The primary endpoints were the proportion of patients who achieved a durable platelet response at week 24 (platelet count, ≥ 50 × 109/L during 6 of the last 8 weeks of treatment) and safety. The study was registered at ClinicalTrials.gov (NCT05621330).

Results: Between October 2019 and December 2021, 216 patients were randomly assigned (QL0911,144; placebo,72). A durable platelet response was achieved by significantly more patients in the QL0911 group (61.8%, 95% CI: 53.3-69.8; < 0.0001) than in the placebo group (0%). The mean duration of platelet responses was 15.9 (SE: 0.43) weeks with QL0911, and 1.9 (SE:0.26) week with placebo. Consistent results were achieved in subgroup analyses categorized by baseline splenectomy status (yes/no), concomitant ITP treatment (yes/no), and baseline platelet count (≤ 10 × 109/L, > 10 × 109/L, ≤ 20 × 109/L, > 20 × 109/L, and < 30 × 109/L). The incidence of TEAEs was comparable between the QL0911 and the placebo groups (91.7% and 88.9%, respectively). The most common adverse events overall were ecchymosis (28.5% for QL0911 . 37.5% for placebo), upper respiratory tract infections respiratory tract infections (31.9% for QL0911 . 27.8% for placebo), and gingival bleeding (17.4% for QL0911 . 26.4% for placebo).

Conclusion: QL0911 was well-tolerated and increased and maintained platelet counts in adults with ITP. QL0911, a biosimilar to romiplostim (Nplate®), may be a novel treatment option for patients with ITP who have failed or relapsed from first-line treatment in China. Ongoing studies will provide further data on long-term efficacy and safety in such patient populations.