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Hetrombopag Achieves Platelet Response in 61% of Pediatric ITP Patients vs 10% Placebo
In a placebo-controlled phase 3 trial, once-daily oral hetrombopag produced platelet counts of at least 50 × 10⁹/L at Week 10 in 61.4% of children and adolescents with immune thrombocytopenia, compared with just 9.7% receiving placebo — an absolute difference of 52.7 percentage points (95% CI 35.9–69.5; P<0.0001). The magnitude and statistical precision of this difference indicate a clinically meaningful treatment effect, though the modest sample size and limited follow-up duration warrant caution in drawing long-term conclusions.
What Was Studied
The trial investigated whether hetrombopag — an oral thrombopoietin receptor agonist (TPO-RA) — could safely raise platelet counts to a clinically meaningful threshold (≥50 × 10⁹/L) in pediatric patients with primary immune thrombocytopenia (ITP) who had either failed to respond adequately to, or relapsed following, prior treatment. This patient population represents a particularly difficult management challenge, as established first-line therapies have already proven insufficient.
How It Was Studied
This was a randomized, double-blind, placebo-controlled phase 3 trial enrolling 88 children and adolescents aged 6 to 17 years with primary ITP who had experienced inadequate response or relapse after prior therapy. Participants were assigned in a 2:1 ratio to receive either once-daily oral hetrombopag (starting dose 2.5 mg) or placebo for 12 weeks, after which all participants entered a 12-week open-label extension phase during which all received hetrombopag. The primary endpoint was assessed at Week 10, with a key secondary endpoint measuring sustained platelet response across Weeks 5 through 12. The trial was conducted across multiple centers and registered under NCT04737850.
What Was Observed
- Primary endpoint — platelet count ≥50 × 10⁹/L at Week 10: More than six times as many hetrombopag-treated patients met this threshold compared to placebo (61.4% vs. 9.7%), representing an absolute difference of 52.7 percentage points (95% CI 35.9–69.5; P<0.0001). This large and statistically robust separation between groups indicates a strong treatment signal.
- Sustained platelet response over Weeks 5–12: Nearly half of hetrombopag-treated patients (43.9%) maintained a platelet count ≥50 × 10⁹/L for at least 6 of those weeks without needing rescue therapy, while no placebo patients achieved this outcome (absolute difference 43.7 percentage points; 95% CI 28.5–58.9; P<0.0001). This finding suggests the response is durable across the double-blind treatment window, not simply a transient effect.
- Rescue therapy requirement: Fewer patients on hetrombopag required rescue therapy during the double-blind phase compared to those on placebo (21.1% vs. 45.2%), consistent with the improvement in platelet counts and indicating a reduction in acute bleeding management needs.
- Hepatotoxicity signal: Treatment-related liver enzyme elevations or hepatic function abnormalities occurred over 24 weeks in 17.5% (10 of 57) of patients receiving continuous hetrombopag. All events were low-grade (grade 1–2) and none resulted in treatment discontinuation, though this rate warrants ongoing monitoring in larger and longer-duration studies. Alanine aminotransferase elevations were observed in 7.0% of hetrombopag patients versus 0% on placebo during the double-blind period.
Why This Matters
Primary ITP is described in this study as the most common acquired bleeding disorder in children, and management becomes particularly difficult once first-line treatments have failed — leaving clinicians with limited options. The results position hetrombopag as a candidate oral TPO-RA for this unmet need in the pediatric age group. The efficacy and safety data generated here may support regulatory review and inform the development of treatment guidelines for children and adolescents with relapsed or refractory ITP.
How to Read This Result
Although the effect sizes are large and statistically compelling, the relatively small overall sample of 88 patients and the 24-week maximum observation period mean that the durability of response beyond this window and the full scope of the hepatotoxicity signal — present in nearly one in five continuously treated patients — remain incompletely characterized.
Limitations
The abstract does not explicitly report study limitations.