Thrombopoietin Receptor Agonists as Second-Line Treatment in Children With Ongoing Immune Thrombocytopenia
Authors: CADTH  
Published: September 2024

What Is the Issue?

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelets and an increase in bleeding risk; in the pediatric population, the reported incidence rate varies between 2 and 5 per 100,000 children per year. Spontaneous remission may be observed in up to 70% of patients, while 20% of patients may experience severe bleeding symptoms.
In children whose ITP does not respond to first-line corticosteroids, IV immunoglobulin (IVIG), or anti-D immunoglobulin, guidelines recommend the use of thrombopoietin receptor agonists (TPO-RAs), i.e., eltrombopag or romiplostim (avatrombopag did not have a marketing authorization and Notice of Compliance at the time that the review was initiated). Rituximab is considered a subsequent-line of therapy. Splenectomy is not usually considered an appropriate treatment option in children.
The goal of therapy in pediatric patients with ITP is to reduce bleeding and improve quality of life. Platelet response is considered a valid and appropriate surrogate end point in studies and routine assessment in clinical practice.
Children whose ITP does not respond to available first-line drugs may require subsequent treatment with off-label drugs because they do not have access to TPO-RAs.

What Did We Do?

We searched key resources, including journal citation databases, and conducted a focused internet search for relevant evidence.
A systematic review of the literature identified 5 studies (4 randomized controlled trials [RCTs] and 1 observational study), which were synthesized narratively.
The review addressed the following policy questions:

In children with ongoing, active ITP, what is the overall body of evidence supporting the use of TPO-RAs and rituximab after failure of first-line therapies?
Based on the level and quality of clinical evidence, should TPO-RAs be reimbursed for use earlier in the treatment sequencing for children with ongoing, active ITP, instead of being reimbursed only after a course of rituximab?

What Did We Find?

Evidence from 2 RCTs (n = 159) suggests that eltrombopag likely increases and maintains platelet response over time, in addition to decreasing the use of rescue medication and clinically significant bleeding compared to placebo, which were considered clinically meaningful outcomes for pediatric patients with ITP. There was a low risk of bias in the studies, but uncertainty was introduced due to the small sample sizes.
Evidence from 1 RCT (n = 62) suggests that romiplostim may also increase and maintain platelet response, as well as reduce clinically significant bleeding compared to placebo. However, there was some concern due to a high risk of bias in the studies and uncertainty due to the small sample size, which suggests a need for caution in the interpretation of the findings.
The effectiveness of rituximab was inconclusive due to the lack of evidence, as no comparative RCTs could be identified, while the observational study included presented only descriptive comparisons. No evidence was identified in support of trying rituximab before accessing TPO-RAs.

What Does This Mean?

Given that ITP is rare in children, there is a gap in available relevant evidence, and robust evidence from large RCTs in this patient population are unlikely to be conducted.
Jurisdictions may consider requesting an implementation advice panel for use of eltrombopag and romiplostim after failure of first-line therapies in children with ongoing, active ITP.