Romiplostim in children with chronic immune thrombocytopenia (ITP): the French experience

Pediatric refractory immune thrombocytopenia: A systematic review

Pediatric immune thrombocytopenia (ITP) is an acquired disorder associated with autoimmune destruction and impairment of platelet production in children. Some children exhibit poor or transient response to ITP-directed treatments and are referred to as having refractory ITP (rITP). There is currently no consensus on the definition of rITP, nor evidence-based treatment guidelines for patients with rITP. After a survey of pediatric ITP experts demonstrated lack of consensus on pediatric rITP, we pursued a systematic review to examine the reported clinical phenotypes and treatment outcomes in pediatric rITP. The search identified 253 relevant manuscripts; following review, 11 studies proposed a definition for pediatric rITP with no consensus amongst them. Most definitions included suboptimal response to medical management, while some outlined specific platelet thresholds to define this suboptimal response. Common attributes identified in this study should be used to propose a comprehensive definition, which will facilitate outcome comparisons of future rITP studies.

SAFETY STUDY OF ROMIPLOSTIM BIOSIMILAR

Idiopathic thrombocytopenic purpura is a chronic autoimmune hematological disease caused by an increased destruction of platelets and associated thrombocytopenia, for the treatment of which the imported drug romiplostim is used. Сreation of the drug biosimilar provides a reduction in the cost of therapy and an access for the treatment to more patients.

The aim of the study was to compare the safety indicators of the reference drug and its biosimilar in vivo and in vitro.

Materials and methods. In the in vitro study, a model of “complement-dependent cytotoxicity” induced by the complement was formed on the 32D hTPOR clone 63-cell line, followed by a cell viability measurement with the CellTitter Glo® kit. An in vivo part of the study was carried out on Javanese macaque monkeys (Macaca fascicularis). During the experiment, the clinical condition, mortality, appetite of the animals, their body weight, body temperature, respiratory rate were assessed, the clinical parameters of blood and urine of the animals were also monitored, and the hemostasis indicators were additionally measured.

Results. In the in vitro experiment, the original drug romiplostim and its biosimilar GP40141 were compared in terms of EC50 values. The indicatirs did not show complement-dependent cytotoxicity. According to the in vivo results, no deviations were recorded in the clinical status of the animals and their feed intake, and no lethality was fixed out in the groups either. For all the parameters studied (body weight and temperature, respiratory rate, clinical urinalysis, clinical and biochemical blood tests, coagulation hemostasis), GP40141 and romiplostim, when administered at the doses equivalent to 10 toxic doses (TDs), had comparable effects.

Conclusion. In the comparison of safety performance both in vitro and in vivo, the original drug romiplostim and its biosimilar GP40141 showed similar results.

Prospective Evaluation of the First Option, Second-Line Therapy in Childhood Chronic Immune Thrombocytopenia: Splenectomy or Immunomodulation

OBJECTIVE

To describe 4 subgroups of pediatric patients treated with splenectomy, hydroxychloroquine, azathioprine, or rituximab as the first-option, second-line treatment for chronic immune thrombocytopenia.

STUDY DESIGN

Selection of patients with chronic immune thrombocytopenia from the French national prospective cohort of pediatric autoimmune cytopenia OBS'CEREVANCE and VIGICAIRE study, treated by splenectomy, hydroxychloroquine, azathioprine, or rituximab as a first second-line treatment.

RESULTS

For 137 patients, treated between 1989 and 2016, the median follow-up after diagnosis and after treatment initiation was 8.5 (2.8-26.4) years and 4.7 (1.1-25.1) years, respectively. Median age at diagnosis and at initiation of treatment were 9 (0.7; 16) and 12 (2; 18.1) years, respectively without significant difference between subgroups. For the whole cohort, 24-month event-free survival was 62% (95% CI 55; 71). It was 85% (95% CI 77; 95) for the 56 patients treated with splenectomy, 60% (95% CI 44; 84) for the 23 patients treated with rituximab, 46% (95% CI 30; 71) for the 24 patients treated with azathioprine, and 37% (95% CI 24; 59) for the 34 patients treated with hydroxychloroquine (log-rank P < .0001). For the splenectomy subgroup, being older than 10 years at splenectomy tended to improve event-free survival (P = .05). Female teenagers with antinuclear antibody positivity benefited from hydroxychloroquine therapy.

CONCLUSIONS

This national study, limiting pitfalls in the analysis of the effects of second-line therapies, showed that splenectomy remains the treatment associated with the better response at 24 months.

Wall shear rates in human and mouse arteries: Standardization of hemodynamics for in vitro blood flow assays: Communication from the ISTH SSC subcommittee on biorheology

Hemodynamics play a central role in hemostasis and thrombosis by affecting all aspects linked to platelet functions and coagulation. In vitro flow devices are extensively used in basic research, pharmacological studies, antiplatelet agent screening, and development of diagnostic tools. Because hemodynamic conditions vary tremendously throughout the vascular tree and among different (patho)physiological processes, it is important to use flow conditions based on relevant biorheological reference ranges. Surprisingly, it is particularly difficult to find a concise overview of relevant hemodynamic parameters in various human and mouse vessels. To our knowledge, this is the first time an inventory of flow conditions in healthy, non-diseased, human and mouse vessels has been created. The objective of providing such a repertoire is to aid researchers in the field of hemostasis and thrombosis in choosing rheological conditions relevant in in vitro flow experiments and to promote harmonization of flow-based assays to facilitate comparative evaluations between studies. With reference to the human, we discuss relevant similarities and discrepancies in wall shear rates in the mouse, which are typically one order of magnitude greater in agreement with allometric scaling laws between species. Importantly, we bring the attention of the researchers to the fact that the relevant range of average wall shear rates in human arteries where clinically relevant arterial thrombosis occurs may fall as low as 100 to 200 s-1, thus significantly overlapping with what are considered "venous" shear rates. The same range for the murine arteries used for arterial thrombosis models may significantly exceed 1000 s-1 reaching values considered to be "pathological."

Thrombopoietin Receptor Agonists in Children with Immune Thrombocytopenia: A New Therapeutic Era

BACKGROUND AND OBJECTIVE

Immune thrombocytopenia (ITP) is a common bleeding disorder in childhood. The management of ITP in children is controversial, requiring personalized assessment of patients and therapeutic choices. Thrombopoietin receptor agonists (TPO-RAs), eltrombopag and romiplostim, have been shown to be safe and effective for the treatment of pediatric ITP. The aim of our research is to define the role of thrombopoietin receptor agonists in the management of pediatric ITP.

METHODS

This review focuses on the use of TPO-RAs in pediatric ITP, in randomized trials and in clinical routine, highlighting their key role in the management of the disease.

RESULTS

Eltrombopag and romiplostim appear effective treatment options for children with ITP. Several clinical studies have assessed that the use of TPO-RAs increases platelet count, decreases bleeding symptoms and improves health-related quality of life. Moreover, TPO-RAs are well tolerated with minor side effects.

CONCLUSION

Although long term efficacy and safety of TPO-RAs still require further investigations, their use is gradually expanding in the clinical practice of children with ITP.

Second-line treatment trends and long-term outcomes of 392 children with chronic immune thrombocytopenic purpura: the French experience over the past 25 years

Childhood chronic immune thrombocytopenic purpura (cITP) is a rare disease. In severe cases, there is no evidence for the optimal therapeutic strategy. Our aim was to describe the real-life management of non-selected children with cITP at diagnosis. Since 2004, patients less than 18 years old with cITP have been enrolled in the national prospective cohort, OBS'CEREVANCE. From 1990 to 2014, in 29 centres, 392 children were diagnosed with cITP. With a median follow-up of six years (2·0-25), 45% did not need second-line therapy, and 55% (n = 217) received one or more second lines, mainly splenectomy (n = 108), hydroxychloroquine (n = 61), rituximab (n = 61) or azathioprine (n = 40). The overall five-year further second-line treatment-free survival was 56% [95% CI 49·5-64.1]. The use of splenectomy significantly decreased over time. Hydroxychloroquine was administered to children with positive antinuclear antibodies, more frequently older and girls, and reached 55% efficacy. None of the patients died. Ten years after the initial diagnosis, 55% of the 56 followed children had achieved complete remission. Children with cITP do not need second-line treatments in 45% of cases. Basing the treatment decision on the pathophysiological pathways is challenging, as illustrated by ITP patients with positive antinuclear antibodies treated with hydroxychloroquine.

Efficacy and safety of thrombopoietin receptor agonists in children with chronic immune thrombocytopenic purpura: meta-analysis

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder presenting with low platelet count <100 × 10⁹/L. The condition affects both adults and children. Thrombopoietin receptor agonists (TPO-RAs) are second-line of therapy that includes Romiplostim and Eltrombopag, which stimulate the production of normally functioning platelets. Although the biological effect of these drugs is well established, there has not been a meta-analysis in children. To estimate the efficacy and safety of Romiplostim and Eltrombopag, we performed a systematic review and meta-analysis in children with chronic ITP. Systematic literature search was conducted in the following database: PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL). Review Manager 5.3 for Windows was used to analyze the data. Five randomized controlled trials with total of 261 pediatric patients from 1-17 years of age were included. The efficacy and safety analysis showed TPO-RA groups were superior over placebo, and there was no difference in adverse event occurrence between TPO-RA (Romiplostim and Eltrombopag) and placebo groups. The efficacy and safety of Eltrombopag did not differ significantly from those of Romiplostim. Both drugs were effective in treatment of children with chronic ITP. Our findings extend the currently available data on ITP treatment and is helpful for pediatric health providers and for the design of future clinical trials.

Evans syndrome: clinical perspectives, biological insights and treatment modalities

Evans syndrome (ES) is a rare and chronic autoimmune disease characterized by autoimmune hemolytic anemia and immune thrombocytopenic purpura with a positive direct anti-human globulin test. It is classified as primary and secondary, with the frequency in patients with autoimmune hemolytic anemia being 37%–73%. It predominates in children, mainly due to primary immunodeficiencies or autoimmune lymphoproliferative syndrome. ES during pregnancy is associated with high fetal morbidity, including severe hemolysis and intracranial bleeding with neurological sequelae and death. The clinical presentation can include fatigue, pallor, jaundice and mucosal bleeding, with remissions and exacerbations during the person’s lifetime, and acute manifestations as catastrophic bleeding and massive hemolysis. Recent molecular theories explaining the physiopathology of ES include deficiencies of CTLA-4, LRBA, TPP2 and a decreased CD4/CD8 ratio. As in other autoimmune cytopenias, there is no established evidence-based treatment and steroids are the first-line therapy, with intravenous immunoglobulin administered as a life-saving resource in cases of severe immune thrombocytopenic purpura manifestations. Second-line treatment for refractory ES includes rituximab, mofetil mycophenolate, cyclosporine, vincristine, azathioprine, sirolimus and thrombopoietin receptor agonists. In cases unresponsive to immunosuppressive agents, hematopoietic stem cell transplantation has been successful, although it is necessary to consider its potential serious adverse effects. In conclusion, ES is a disease with a heterogeneous course that remains challenging to patients and physicians, with prospective clinical trials needed to explore potential targeted therapy to achieve an improved long-term response or even a cure.

Eltrombopag versus romiplostim in treatment of children with persistent or chronic immune thrombocytopenia: a systematic review incorporating an indirect-comparison meta-analysis

In absence of direct comparison, we conducted an indirect-comparison meta-analysis to evaluate the efficacy and safety of thrombopoietin-receptor agonists(TPO-RAs) in treatment of pediatric persistent or chronic immune thrombocytopenia(ITP). PubMed, Embase, Cochrane Library, Clinical Trials.gov, China National Knowledge Infrastructure, and Chinese Biomedical Literature Database were searched from their earliest records to May 2017. Randomized controlled trials comparing the TPO-RAs with placebo in pediatric ITP were included. Outcomes included overall response rate(primary), durable response, overall or clinically significant bleeding, the proportion of patients receiving rescue medication, and safety. Five randomized placebo-controlled studies(N = 261) were analyzed. The overall response[Risk Ratio(RR) 0.57, 95% confidence interval(CI) 0.21–1.56], the incidence of adverse events (RR 0.96, 95%CI 0.66–1.39), durable response(RR 2.48, 95%CI 0.31–19.97), and the proportion of patients receiving rescue treatment(RR 0.73, 95%CI 0.20–2.73) were similar between eltrombopag and romiplostim group. Nevertheless, eltrombopag might have lower risk of overall bleeding(RR 0.43, 95%CI 0.23–0.80) and clinically significant bleeding(RR 0.33, 95%CI 0.12–0.89) than romiplostim. This meta-analysis suggests that eltrombopag might be similar to romiplostim in efficacy and safety, but seems to reduce the risk of bleeding compared to romiplostim. Furthermore, cost of the treatment, comorbidity of patients and drug compliance should also be considered in clinical decision making.

Thrombopoietin and its receptor expression in pediatric patients with chronic immune thrombocytopenia

OBJECTIVES

Chronic immune thrombocytopenia (cITP) is common in children. However, the pathogenesis has not been fully elucidated. This study aimed to determine whether thrombopoietin (TPO) and its receptor c-mannosylation of the TPO receptor (c-Mpl) have an impact on childhood cITP.

METHODS

Sixty-four patients with newly diagnosed ITP (nITP), 64 patients with persistent ITP, 80 patients with cITP, and 64 healthy children (control) were enrolled in this study. Plasma TPO was measured with an ELISA, and c-Mpl was determined by flow cytometry.

RESULTS

Plasma TPO levels showed differences among the four groups (p = 0.001). TPO levels in the cITP group were significantly decreased compared to those in the nITP group (p < 0.05). The mean fluorescence intensity (MFI) of c-Mpl was significantly different among the four groups (p = 0.0275). c-Mpl MFI was lower in the cITP group than in the nITP group(p < 0.05). Quantitative real-time PCR analysis showed that TPO mRNA expression was higher in the control group than in the ITP groups (p < 0.0001). The c-Mpl mRNA levels also showed significant differences among the four groups (p = 0.023). The control group, compared with the other groups, had lower levels of c-Mpl mRNA.

CONCLUSIONS

The expression of TPO and c-Mpl was significantly decreased in the cITP group compared to the nITP group, suggesting that TPO and its receptor may play important roles in childhood cITP pathogenesis.

Childhood immune thrombocytopenia: A nationwide cohort study on condition management and outcomes

OBJECTIVES

Nationwide prospective cohort study exploring (i) the factors associated with treatment initiation (vs. watchful waiting) in children with primary immune thrombocytopenia (ITP) followed in routine clinical practice and (ii) the predictors of chronicity at 12 months.

PROCEDURE

Between 2008 and 2013, 23 centers throughout France consecutively included 257 children aged 6 months-18 years and diagnosed with primary ITP over a 5-year period. Data on ITP clinical features along with medical management were collected at baseline and 12 months. Multivariate logistic regressions were used to determine (i) and (ii) as defined above, providing odds ratio (OR) with 95% confidence interval (95% CI).

RESULTS

One hundred thirty-seven (53%) children were males, median age was 4.6 years, median platelet count was 7 × 109/l, and 214 (81%) patients initiated medication. Factors independently associated with treatment initiation included platelet counts <10 × 109/l (P < 0.0001) and mucocutaneous bleeding symptoms at baseline (P < 0.001). At 12 months, data were available for 211 (82%) children, of whom 160 (74%) had recovered. Predictors of chronicity included female gender (OR = 2.2; 95% CI = 1.0-4.8), age ≥10 years (OR = 2.6; 95% CI = 1.1-6.0), and platelet counts ≥10 × 10⁹ /l (OR = 3.2; 95% CI = 1.5-6.9).

CONCLUSIONS

In routine clinical practice, the decision to apply a watchful waiting strategy seems to be driven by platelet counts even in the absence of bleeding symptoms, resulting in treatment being initiated in more than 80% of the children surveyed. Overall, younger children with ITP showed good prognosis, with lower platelet counts and, to a lesser extent, male gender predicting more favorable outcomes.

Spotlight on romiplostim in the treatment of children with chronic immune thrombocytopenia: design, development, and potential place in therapy

Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia. In approximately one-third of cases, the duration of thrombocytopenia will extend beyond 12 months consistent with a diagnosis of chronic ITP. Minor bleeding manifestations are common in chronic ITP while severe or life-threatening bleeding complications are uncommon. Moreover, spontaneous resolution occurs in the majority of children with chronic ITP necessitating treatment in only those children with ongoing bleeding manifestations or impairment in health-related quality of life (HRQOL). The characterization of thrombopoietin (TPO) and remarkable advancements in our understanding of the pathophysiology of ITP has led to the development of a new class of agents, the TPO-receptor agonists that have documented efficacy in the amelioration of thrombocytopenia and bleeding manifestations in chronic ITP. Romiplostim is a second-generation TPO-receptor agonist that has undergone limited evaluation in the treatment of chronic ITP in children. Evolving data suggest that romiplostim may be a safe and effective agent in the treatment of chronic ITP in children. Additional data are needed to confirm its ability to increase platelet counts, decrease bleeding manifestation, and improve the HRQOL of children and caregivers impacted by chronic ITP.

The Centenary of Immune Thrombocytopenia-Part 2: Revising Diagnostic and Therapeutic Approach

Primary immune thrombocytopenia (ITP) is the most common cause of thrombocytopenia in children and adolescents and can be considered as a paradigmatic model of autoimmune disease. This second part of our review describes the clinical presentation of ITP, the diagnostic approach and overviews the current therapeutic strategies. Interestingly, it suggests an algorithm useful for differential diagnosis, a crucial process to exclude secondary forms of immune thrombocytopenia (IT) and non-immune thrombocytopenia (non-IT), which require a different therapeutic management. Advances in understanding the pathogenesis led to new therapeutic targets, as thrombopoietin receptor agonists, whose role in treatment of ITP will be discussed in this work.

Thrombopoietin Receptor Agonist Use in Children: Data From the Pediatric ITP Consortium of North America ICON2 Study

BACKGROUND

Data on second-line treatment options for pediatric patients with immune thrombocytopenia (ITP) are limited. Thrombopoietin receptor agonists (TPO-RA) provide a nonimmunosuppressive option for children who require an increased platelet count.

PROCEDURE

We performed a multicenter retrospective study of pediatric ITP patients followed at ITP Consortium of North America (ICON) sites to characterize TPO-RA use.

RESULTS

Seventy-nine children had a total of 87 treatments (28 eltrombopag, 43 romiplostim, and eight trialed on both). The majority had primary ITP (82%) and most (60.8%) had chronic ITP. However, 22% had persistent ITP and 18% had newly diagnosed ITP. During the first 3 months of treatment, 89% achieved a platelet count ≥ 50 × 10(9) /l (86% romiplostim, 81% eltrombopag, P = 0.26) at least once in the absence of rescue therapy. The average time to a response was 6.4 weeks for romiplostim and 7.0 weeks for eltrombopag (P = 0.83). Only 40% of patients demonstrated a stable response with consistent dosing over time. An intermittent response with constant dose titration was seen in 15%, and an initial response that waned to no response was seen in 13%. Significant adverse events were minimal with the exception of two patients with thrombotic events and one who developed a neutralizing antibody.

CONCLUSIONS

Our results demonstrate that TPO-RA agents are being used in children with ITP of varying duration and severity. The response was similar to clinical trials, but the sustainability of response varied. Future studies need to focus on the ideal timing and rationale for these medications in pediatric patients.

Romiplostim in children with immune thrombocytopenia: a phase 3, randomised, double-blind, placebo-controlled study

BACKGROUND

The thrombopoietin receptor agonist romiplostim could be an effective treatment in symptomatic children with persistent or chronic immune thrombocytopenia. We aimed to assess whether romiplostim is safe and effective in children with immune thrombocytopenia of more than 6 months' duration.

METHODS

In this phase 3 double-blind study, eligible participants were children with immune thrombocytopenia aged 1 year to 17 years and mean platelet counts 30 × 10(9)/L or less (mean of two measurements during the screening period) with no single count greater than 35 × 10(9)/L, and were recruited from 27 sites in the USA, Canada, and Australia. Participants were randomly assigned (2:1) through the interactive voice response system to receive weekly romiplostim or placebo for 24 weeks stratified by age (1 year to <6 years, 6 years to <12 years, 12 years to <18 years), adjusting the dose weekly from 1 μg/kg to 10 μg/kg to target platelet counts of 50-200 × 10(9)/L. Patients and investigators were blinded to the treatment assignment. The primary analysis included all randomised patients and the safety analysis included all randomised patients who received at least one dose of investigational product. The primary endpoint, durable platelet response, was defined as achievement of weekly platelet responses (platelet counts ≥50 × 10(9)/L without rescue drug use in the preceding 4 weeks) in 6 or more of the final 8 weeks (weeks 18-25). This study is registered with ClinicalTrials.gov, NCT 01444417.

FINDINGS

Between Jan 24, 2012, and Sept 3, 2014, 62 patients were randomly assigned; 42 to romiplostim and 20 to placebo. Durable platelet response was seen in 22 (52%) patients in the romiplostim group and two (10%) in the placebo group (p=0·002, odds ratio 9·1 [95% CI 1·9-43·2]). Durable platelet response rates with romiplostim by age were 38% (3/8) for 1 year to younger than 6 years, 56% (10/18) for 6 years to younger than 12 years, and 56% (9/16) for 12 years to younger than 18 years. One (5%) of 19 patients in the placebo group had serious adverse events compared with 10 (24%) of 42 patients in the romiplostim group. Of these serious adverse events, headache and thrombocytosis, in one (2%) of 42 patients in the romiplostim group, were considered treatment related. No patients withdrew due to adverse events.

INTERPRETATION

In children with chronic immune thrombocytopenia, romiplostim induced a high rate of platelet response with no new safety signals. Ongoing romiplostim studies will provide further information as to long-term efficacy, safety, and remission in children with immune thrombocytopenia.

FUNDING

Amgen Inc.

Long-term safety and efficacy of romiplostim for treatment of immune thrombocytopenia

Inhibition of platelet production and mediated by antiplatelet antibodies is a well-known mechanism causing low platelet counts in immune thrombocytopenia (ITP). Use of thrombopoietin receptor agonists increases platelet counts and decreases the risk of bleeding in patients with ITP. Two such thrombopoietin receptor agonists, romiplostim and eltrombopag, are approved by the US Food and Drug Administration to treat thrombocytopenia in adults, and most recently, children with persistent or chronic ITP. This review focuses on the efficacy data and safety analysis of the pooled data from the clinical trials evaluating romiplostim for treatment of adults with ITP. The rates of hemorrhage, thrombosis, hematologic and nonhematologic cancers, and myelodysplastic syndrome were not overrepresented among the groups who received romiplostim versus placebo or other standard-of-care treatments. Yet, as after-market experience with thrombopoietin receptor agonists increases, there are emerging reports of increased incidence of thrombosis and bone marrow reticulin among patients who are treated with long-term use of these agents. Ongoing clinical research will continue to evaluate romiplostim's efficacy and safety in other primary and secondary thrombocytopenic states.

Romiplostim as a treatment for immune thrombocytopenia: a review

“Immune thrombocytopenia” (ITP) is an autoimmune disorder that leads to peripheral destruction, as well as a decreased production of platelets. ITP most commonly presents as mild mucocutaneous bleeding. Though it is rare, the leading cause of mortality in persons with ITP is intracranial hemorrhage and those that do not respond to therapy are at increased risk. Our understanding of the pathophysiology of ITP has evolved immensely, especially over the last 60 years. The discovery of the platelet-production stimulator, thrombopoietin (TPO), lent clarity to an earlier hypothesis that inhibition of platelet production at the level of the megakaryocyte, at least in part, accounts for thrombocytopenia in adults with ITP. This facilitated the development of TPO-based therapies to treat ITP. Thrombopoietin receptor agonists are one of the most recent treatments to enter the landscape. Original production of a recombinant human TPO was halted after clinical trials revealed the untoward effect of autoantibodies to the recombinant human TPO with cross-reactivity to endogenous TPO. Next-step development focused on stimulation of the TPO receptor with fewer immunogenic agents. Currently, two such thrombopoietin receptor agonists, romiplostim and eltrombopag, are licensed in the USA to treat thrombocytopenia in adults with persistent or chronic ITP. Ongoing research will assess their efficacy in other immune-mediated and nonimmune-mediated primary and secondary thrombocytopenias.

Use of Thrombopoietin Receptor Agonists in Childhood Immune Thrombocytopenia

Most children with immune thrombocytopenia (ITP) will have spontaneous remission regardless of therapy, while about 20% will go on to have chronic ITP. In those children with chronic ITP who need treatment, standard therapies for acute ITP may have adverse effects that complicate their long-term use. Thus, alternative treatment options are needed for children with chronic ITP. Thrombopoietin receptor agonists (TPO-RA) have been shown to be safe and efficacious in adults with ITP, and represent a new treatment option for children with chronic ITP. One TPO-RA, eltrombopag, is now approved for children. Clinical trials in children are ongoing and data are emerging on safety and efficacy. This review will focus on the physiology of TPO-RA, their clinical use in children, as well as the long-term safety issues that need to be considered when using these agents.

Treatment of pediatric primary immune thrombocytopenia with thrombopoietin receptor agonists

Chronic immune thrombocytopenia (ITP) occurs in approximately one fifth of children with primary ITP and is characterized by a significant lack of clinical data. A minority of these children exhibit bleeding and need treatment. Often standard therapy used for patients with newly diagnosed ITP is administered to stop bleeding and to increase the platelet count. These drugs are associated with adverse effects, which is particularly evident when used during long time. In adult patients with chronic ITP, thrombopoietin receptor agonists (TPO-RAs) demonstrated efficacy in approximately 80% of patients. These drugs have been studied intensely for registration purposes; however, for children and adolescents they are not yet approved and studies are ongoing. First experiences with these drugs show similar effects and safety as in adults, though based on very small numbers of children. These drugs have the potential to be used during long time, in order to increase platelets, to stop or prevent bleeding and to augment quality of life, making long-term safety an important issue.