A randomized, double-blind study of romiplostim to determine its safety and efficacy in children with immune thrombocytopenia

Treatment of Immune Thrombocytopenia: Contextualization from a Historical Perspective

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by an isolated decrease in platelet count and an increased risk of bleeding. The pathogenesis is complex, affecting multiple components of the immune system and causing both peripheral destruction of platelets and inadequate production in the bone marrow. In this article, we review the treatment of ITP from a historical perspective, discussing first line and second line treatments, and management of refractory disease.

Thrombopoietin-receptor agonists for adult patients with immune thrombocytopenia: a narrative review and an approach for managing patients fasting intermittently

Introduction

Thrombopoietin-receptor agonist (TPO-RAs) currently represent the state of art for treating immune thrombocytopenia. Their different molecular structures contribute to the difference in their pharmacodynamics and pharmacokinetics. This narrative review aims to provide an overview of the current TPO-RAs approved for primary immune thrombocytopenia (romiplostim, eltrombopag, avatrombopag) and the effect of intermittent fasting in adult patients receiving TPO-RAs.

Areas covered

Literature was searched with no limits on date or language, using various combinations of keywords. Data on the pharmacokinetics, pharmacodynamics, efficacy, and safety of TPO-RAs and the effect of intermittent fasting were summarized.

Expert opinion

Switching between TPO-RAs is a useful strategy to tackle some associated limitations. Romiplostim and avatrombopag have an advantage over eltrombopag as they do not require any dietary restrictions. In cases where romiplostim and avatrombopag are unavailable, patients should be educated on the appropriate administration, possible interactions, and dietary restrictions before initiating eltrombopag.

Unraveling the potential of M13 phages in biomedicine: Advancing drug nanodelivery and gene therapy

M13 phages possessing filamentous phage genomes offer the benefits of selective display of molecular moieties and delivery of therapeutic agent payloads with a tolerable safety profile. M13 phage-displayed technology for resembling antigen portions led to the discovery of mimetic epitopes that applied to antibody-based therapy and could be useful in the design of anticancer vaccines. To date, the excremental experiences have engaged the M13 phage in the development of innovative biosensors for detecting biospecies, biomolecules, and human cells with an acceptable limit of detection. Addressing the emergence of antibiotic-resistant bacteria, M13 phages are potent for packaging the programmed gene editing tools, such as CRISPR/Cas, to target multiple antimicrobial genes. Moreover, their display potential in combination with nanoparticles inspires new approaches for engineering targeted theragnostic platforms targeting multiple cellular biomarkers in vivo. In this review, we present the available data on optimizing the use of bacteriophages with a focus on the to date experiences with M13 phages, either as monoagent or as part of combination regimens in the practices of biosensors, vaccines, bactericidal, modeling of specific antigen epitopes, and phage-guided nanoparticles for drug delivery systems. Despite increasing research interest, a deep understanding of the underlying biological and genetic behaviors of M13 phages is needed to enable the full potential of these bioagents in biomedicine, as discussed here. We also discuss some of the challenges that have thus far limited the development and practical marketing of M13 phages.

Safety of romiplostim and eltrombopag for children with immune thrombocytopenia: a pharmacovigilance study of the FDA adverse event reporting system database

BACKGROUND

Romiplostim and eltrombopag are thrombopoietin receptor agonists (TPORAs) that have been approved by the FDA on 22 August 2008 and 20 November 2008 for pediatric immune thrombocytopenia (ITP). However, postmarketing pharmacovigilance of TPORAs in children still attracts much attention. We aimed to evaluate the safety of the TPORAs romiplostim and eltrombopag using data from the Adverse Event Reporting System database of FDA (FAERS).

RESEARCH DESIGN AND METHODS

We conducted a disproportionality analysis and analyzed data from the FAERS database to characterize the key features of adverse events (AEs) associated with TPO-RAs approved for children under 18 years of age.

RESULTS

Since their approval in the market in 2008, 250 and 298 reports of romiplostim and eltrombopag use in children have been published in the FAERS database, respectively. The most frequent AE associated with romiplostim and eltrombopag was epistaxis. Neutralizing antibodies and vitreous opacities showed the strongest signals for romiplostim and eltrombopag, respectively.

CONCLUSIONS

The labeled AEs for romiplostim and eltrombopag in children were analyzed. Unlabeled AEs may reflect the potential of new clinical individuals. Early recognition and management of AEs that appear in children treated with romiplostim and eltrombopag are of key importance in clinical practice.

A bibliometric analysis of primary immune thrombocytopenia from 2011 to 2021

Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia. This bibliometric analysis was applied to identify the characteristics of global scientific output, the hotspots, and frontiers of ITP over the past 10 years. We retrieved publications from 2011 to 2021 from the Web of Science Core Collection (WoSCC). Bibliometrix package, VOSviewer, and Citespace were used to analyse and visualize the trend, distribution, and hotspots of research on ITP. Altogether, there were 2084 papers, written by 9080 authors from 410 organizations in 70 countries/regions, published in 456 journals with 37 160 co-cited references. In the last decades, the most productive journal was British Journal of Haematology, China was the most productive country. and the most cited journal was Blood. Shandong University was the most productive institution in the field of ITP. NEUNERT C, 2011, BLOOD, CHENG G, 2011, LANCET, and PATEL VL, 2012, BLOOD were the top three most cited documents. "Thrombopoietin receptor agonist", "regulatory T cell" and "sialic acid" were three hotspots of the last decade. And "immature platelet fraction", "Th17", and "fostamatinib" would be research frontiers in the feature. The present study provided a novel insight for future research directions and scientific decision-making.

Safety and efficacy of romiplostim in children and adolescents with Immune thrombocytopenia: A systematic review

OBJECTIVE

To evaluate the efficacy and safety of romiplostim (thrombopoietin-receptor agonist) in the treatment of pediatric immune thrombocytopenia (ITP).

METHODS

Searches were conducted in MEDLINE, EMBASE, LILACS, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov (from January 2011 to August 2021). Randomized controlled trials (RCTs), double-blind, comparing romiplostim with a placebo in pediatric persistent or chronic ITP were included. The primary outcome was the overall response rate (platelets ≥ 50 × 10⁹/L) in the absence of rescue therapy for at least two consecutive weeks. The secondary endpoints were the minimization of clinically significant bleeding and the necessity for rescue treatments and the maximization of safety (incidence of overall adverse events) and durable response (maintaining platelet counts for at least twelve weeks).

RESULTS

Two double-blind randomized placebo-controlled trials (84 participants) were included in this systematic review. Our data showed that, compared to the placebo group, the proportion of patients achieving durable platelet response was significantly higher in the romiplostim group (p = 0.003, RR = 6.34, 95%CI = 1.89 - 21.23), as was the overall response in the romiplostim group (p = 0.002, RR = 3.62, 95%CI = 1.63 - 8.03). Significant bleeding incidents (p = 0.49), overall adverse events (p = 0.71) and the need for rescue treatment (p = 0.13) were not statistically different between the romiplostim and placebo groups.

CONCLUSIONS

Romiplostim might improve both durable and overall platelet response in children and adolescents with ITP, compared to a placebo. More clinical trials are needed to evaluate the efficacy and safety of romiplostim and to compare it with other second-line treatments that are being used in pediatric ITP.

Romiplostim use in pregnant women with immune thrombocytopenia

Treatment for immune thrombocytopenia (ITP) in pregnancy is hampered by the lack of fetal safety evidence of maternally-administered medications. The Pregnancy Surveillance Program (PSP) collected patient information from 2017-2020 for pregnancy, birth outcomes, and adverse events (AEs) for 186 women exposed to romiplostim from 20 days before pregnancy to the end of pregnancy. Timing of exposure was available in 128 women. Seventy-one mothers (38%) had prepregnancy exposure to romiplostim; intrapartum exposure was known for the first (for many mothers when they discovered their pregnancy), second, and third trimesters for 74 (40%), 22 (12%), and 44 (24%) mothers, respectively, with 15 mothers exposed during >1 trimester. Among the 86 mothers with known pregnancy outcomes, 46 (53%) had at least one pregnancy-related serious AE (SAE); approximately 2/3 of SAEs were due to underlying ITP. Of 92 mothers with known birth outcomes, 60 (65%) had a normal pregnancy and 16 (17%) had complications, with both categories including term and preterm births; there were 12 (14%) spontaneous miscarriages/stillbirths, 3 (3%) ectopic pregnancies, and 1 (1%) molar pregnancy. Most abnormal births resulted from abnormal pregnancies. There were five neonatal/postnatal AEs of note: inguinal hernia, cytomegalovirus infection, trisomy 8 (third trimester single-dose romiplostim exposure), single umbilical artery without known anomalies, and development of autism at age 2 years. Seven of 12 infants with neonatal thrombocytopenia had resolution of thrombocytopenia before discharge; all 12 were discharged. Review of pregnancies in women exposed to romiplostim did not reveal any specific safety concerns for mothers, fetuses, or infants.

Efficacy and quality of life of Romiplostim in adults and children with immune thrombocytopenia: A review

BACKGROUND

To systematically evaluate the clinical efficacy, drug safety and health-related quality of life (HRQoL) of Romiplostim in adult and child immune thrombocytopenia (ITP) patients.

METHODS

PubMed, EMBASE and Cohrane library databases were searched for all randomized controlled trials published until 2022, and the Review Manager 5.3 was used for meta-analysis.

RESULTS

A total of 9 randomized controlled trials were included in this study. The results of meta-analysis showed that the total platelet response rate and long-term platelet response rate in treatment group were significantly higher than those in control group (P<0.05). There was no statistical significance in the side effects, serious side effects, bleeding events and serious bleeding events between 2 groups (P>0.05). Compared with control group, the HRQoL in ITP adults and children, and parents of ITP children had no statistical significance (P>0.05).

CONCLUSION

Romiplostim has a certain clinical efficacy in ITP adults and children, and relatively small adverse drug reactions. The improvement of Romiplostim on HRQoL in ITP adults and children is not clear.

Treatment of drug-induced immune thrombocytopenias

Several therapeutic agents can cause thrombocytopenia by either immune-mediated or non-immune-mediated mechanisms. Non-immune-mediated thrombocytopenia is due to direct toxicity of drug molecules to platelets or megakaryocytes. Immune-mediated thrombocytopenia, on the other hand, involves the formation of antibodies that react to platelet-specific glycoprotein complexes, as in classic drug-induced immune thrombocytopenia (DITP), or to platelet factor 4, as in heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombotic thrombocytopenia (VITT). Clinical signs include a rapid drop in platelet count, bleeding or thrombosis. Since the patient's condition can deteriorate rapidly, prompt diagnosis and management are critical. However, the necessary diagnostic tests are only available in specialized laboratories. Therefore, the most demanding step in treatment is to identify the agent responsible for thrombocytopenia, which often proves difficult because many patients are taking multiple medications and have comorbidities that can themselves also cause thrombocytopenia. While DITP is commonly associated with an increased risk of bleeding, HIT and VITT have a high mortality rate due to the high incidence of thromboembolic complications. A structured approach to drug-associated thrombocytopenia/thrombosis can lead to successful treatment and a lower mortality rate. In addition to describing the treatment of DITP, HIT, VITT, and vaccine-associated immune thrombocytopenia, this review also provides the pathophysiological and clinical information necessary for correct patient management.

Treatment of chemotherapy-induced thrombocytopenia in patients with non-hematologic malignancies

Chemotherapy-induced thrombocytopenia (CIT) is a common complication of the treatment of non-hematologic malignancies. Many patient-related variables (e.g., age, tumor type, number of prior chemotherapy cycles, amount of bone marrow tumor involvement) determine the extent of CIT. CIT is related to the type and dose of chemotherapy, with regimens containing gemcitabine, platinum, or temozolomide producing it most commonly. Bleeding and the need for platelet transfusions in CIT are rather uncommon except in patients with platelet counts below 25x10⁹/L in whom bleeding rates increase significantly and platelet transfusions are the only treatment. Nonetheless, platelet counts below 70x10⁹/L present a challenge. In patients with such counts, it is important to exclude other causes of thrombocytopenia (medications, infection, thrombotic microangiopathy, post-transfusion purpura, coagulopathy and immune thrombocytopenia). If these are not present, the common approach is to reduce chemotherapy dose intensity or switch to other agents. Unfortunately decreasing relative dose intensity is associated with reduced tumor response and remission rates. Thrombopoietic growth factors (recombinant human thrombopoietin, pegylated human megakaryocyte growth and development factor, romiplostim, eltrombopag, avatrombopag and hetrombopag) improve pretreatment and nadir platelet counts, reduce the need for platelet transfusions, and enable chemotherapy dose intensity to be maintained. National Comprehensive Cancer Network guidelines permit their use but their widespread adoption awaits adequate phase III randomized, placebo-controlled studies demonstrating maintenance of relative dose intensity, reduction of platelet transfusions and bleeding, and possibly improved survival. Their potential appropriate use also depends on consensus by the oncology community as to what constitutes an appropriate pretreatment platelet count as well as identification of patient-related and treatment variables that might predict bleeding.

Safety, tolerance, pharmacokinetic and pharmacodynamic properties of thrombopoietin mimetic peptide for injection in Chinese healthy volunteers: a randomized, placebo-controlled, double-blind study

The thrombopoietin mimetic peptide for injection is a second-generation thrombopoietin receptor agonist (TPO-RA) used in the treatment of patients with immune thrombocytopenia. The aim of the present study was to assess the safety, tolerance, pharmacokinetic and pharmacodynamic properties of thrombopoietin mimetic peptide for injection in Chinese healthy volunteers. A randomized, placebo-controlled, double-blind, dose-escalation study was conducted in healthy Chinese subjects aged 18-50 years. Thirty subjects received single subcutaneous injection of 0.3 μg/kg, 1.0 μg/kg, 2.0 μg/kg thrombopoietin mimetic peptide or placebo. Thrombopoietin mimetic peptide was safe and well tolerated at doses of 0.3-2.0 μg/kg. There was no significant change in mean platelet count (PLT) from baseline at the 0.3 μg/kg or placebo groups. The mean PLT of subjects in the 1.0 μg/kg and 2.0 μg/kg groups peaked at day 12 (± 1), began to decline around day 17, and returned to the baseline level at day 28 (± 1). Platelet aggregation rates of the three dose groups showed no significant change before and after administration. Serum concentrations of thrombopoietin mimetic peptide in all subjects were below the quantization limit. This was the first study to demonstrate that subcutaneous injection of thrombopoietin mimetic peptide at doses of 0.3-2.0 μg/kg was safe and well tolerated in Chinese healthy subjects. As a second-generation TPO-RA, thrombopoietin mimetic peptide is effective at improving PLT after single subcutaneous injection at dose of ≥1 μg/kg.Plain language summaryWhat is the context?● Immune thrombocytopenia (ITP) is a rare, serious autoimmune disorder characterized by low platelet count (PLT) without an alternate cause. The treatment goal of ITP is to increase the platelet count to a safe level that can stop active bleeding and reduce the risks of future bleeding.● Thrombopoietin receptor agonists (TPO-RAs, e.g. eltrombopag, avatrombopag, hetrombopag, and romiplostim) have shown high response rates in stimulating platelet production and reducing the risk of bleeding. TPO-RAs provide ITP patients with well-tolerated, long-term treatment choices.What is new?● The thrombopoietin mimetic peptide for injection is a new TPO-RAs developed by Shandong Quangang Pharmaceutical Co., Ltd. (China).● This study showed that thrombopoietin mimetic peptide is effective at improving PLT after a single subcutaneous injection.● The thrombopoietin mimetic peptide is safe and well-tolerated in Chinese healthy subjects.What is the impact?● This study provides evidence for the further development potential of the thrombopoietin mimetic peptide.

Generic romiplostim for children with persistent or chronic immune thrombocytopenia: Experience from a tertiary care centre in North India

Thrombopoietin receptor agonists are important therapeutic option in children with immune thrombocytopenia (ITP). We evaluated the response, efficacy, safety of a generic form of romiplostim manufactured in India for treating children with persistent/chronic ITP at our centre. Study of 45 children with persistent/chronic ITP was conducted of which 5 discontinued and 40 were included between 2019-2020. Patients received romiplostim for 20 weeks, at a dose of 5 mcg/kg/week. Platelet count at week 1, 3, 20 and 26 was assessed. Predesigned algorithm was used for dose adjustment. After 20 weeks, patients who had platelet count of 50 × 109/L or above were tapered off medication and monitored till 26 weeks. Median platelet count at enrolment was 11 x 109/L (IQR 23 X 109/L). 13/40 children had received >/= three lines of prior ITP therapy. Platelet response (platelet count rise to more than 50×109/L without rescue medications) observed in 26 (65%) patients at week 20. Rescue medication was used in 12/40 children. Sustained platelet response after tapering and stopping romiplostim observed in 22/40 children. No adverse events were considered serious or led to discontinuation of treatment. Our data demonstrated generic romiplostim is well tolerated and efficacious in children with persistent/chronic ITP.

A single-arm, long-term efficacy and safety study of subcutaneous romiplostim in children with immune thrombocytopenia

Romiplostim is a thrombopoietin (TPO) receptor agonist approved for children and adults with immune thrombocytopenia (ITP) for ≥6 months, recommended as second-line treatment. This phase 3b, single-arm, multicenter study investigated long-term efficacy and safety of romiplostim in children ≥1 to <18 years old with ≥6 months' ITP duration and platelet counts ≤30 × 109/L. Children received weekly subcutaneous romiplostim (1 μg/kg titrated to 10 μg/kg) to maintain platelets within 50 to 200 × 109/L. A subset underwent bone marrow examinations. The primary end point was percentage of time with platelet response during the first 6 months' treatment (counts ≥50 × 109/L without rescue medication within the preceding 4 weeks). Overall, 203 patients (median age, 10.0 years) received ≥1 dose of romiplostim, median treatment duration was ∼3 years, and median average weekly dose was 6.9 μg/kg. Ninety-five (46.8%) discontinued (lack of efficacy, n = 43 [21.2%]). Platelet responses were achieved a median (interquartile range) of 50.0% (16.7%-83.3%) of the time during the first 6 months, increasing to 78.2% (26.7%-90.4%) during the overall 36-month treatment period. Eleven patients (5.4%) achieved sustained responses (consecutive counts ≥50 × 109/L without ITP medications for ≥24 weeks). Treatment-related adverse events (AEs) occurred in 56 patients (27.6%), with 8 (3.9%) experiencing serious treatment-related AEs; all of these led to discontinuation, including 4 cases of neutralizing antibodies (romiplostim, n = 3; TPO, n = 1). Bleeding occurred in 141 patients (69.5%), decreasing over time; grade ≥3 bleeding events occurred in 20 (9.9%). At year 2, eight of 63 evaluable patients (12.7%) had grade 2 reticulin. Long-term romiplostim resulted in sustained on-treatment platelet responses with an overall safety profile consistent with previous studies. This trial was registered at www.clinicaltrials.gov as #NCT02279173.

Management of immune thrombocytopenia: 2022 update of Korean experts recommendations

Despite the availability of therapies to treat patients with immune thrombocytopenia (ITP), there is currently little data from randomized trials to assist clinicians in managing patients. The evidence-based guidelines of the Korean Society of Hematology Aplastic Anemia Working Party (KSHAAWP) are intended to support patients and physicians in the management of ITP. Experts from the KSHAAWP discussed and described this guideline according to the current treatment situation for ITP in Korea and finalized the guidelines. The expert panel recommended the management of ITP in adult and pediatric patients with newly diagnosed, persistent, and chronic disease refractory to first-line therapy with minor bleeding. Management approaches include observation and administration of corticosteroids, intravenous immunoglobulin, anti-D immunoglobulin, and thrombopoietin receptor agonists. Currently, evidence supporting strong recommendations for various management approaches is lacking. Therefore, a large focus was placed on shared decision-making, especially regarding second-line treatment.

Thrombopoietin receptor agonists and rituximab for treatment of pediatric immune thrombocytopenia: A systematic review and meta-analysis of prospective clinical trials

BACKGROUND

Children with immune thrombocytopenia (ITP) may require second-line ITP therapies. The high remission rate in pediatric patients, need for extended-duration use of thrombopoietin receptor agonists (TPO-RAs), drug adherence, potential side effects, monitoring, and cost effectiveness are factors that should be considered in decision-making about second-line therapies. Rituximab (RTX) has been used off-label for years to treat ITP but there are limited studies about its efficacy and safety in children. To date, no studies have directly compared TPO-RAs with RTX for the treatment of childhood ITP.

METHODS

This systematic review analyzed the overall platelet response, durability of treatment effect, and safety for RTX use in comparison to TPO-RAs in pediatric ITP. MEDLINE/PubMed, EMBASE, Cochrane Library, and Web of Science databases were searched through December 2020 and meta-analysis was conducted using proportions of success/failure for each intervention in the selected studies.

RESULTS

The proportion of participants achieving the primary endpoint of a platelet response above 50,000 was similar for TPO-RAs (proportion = 0.71, 95% CI: 0.63-0.78) and RTX (proportion = 0.68, 95% CI: 0.53-0.82). However, considerable variation was found between the two groups with regards to the sustainability of the response and other secondary outcomes such as need for rescue and adverse events. RTX was associated with higher rates of rescue therapy.

CONCLUSIONS

In this analysis of prospective pediatric ITP studies, RTX and TPO-RAs had similar rates of overall platelet response but differed in other important measures. Prospective comparative studies are needed to better characterize second-line treatments for pediatric ITP.

Assessment of romiplostim immunogenicity in pediatric patients in clinical trials and in a global postmarketing registry

Development of first-generation thrombopoietins (TPOs) was halted due to antibodies that neutralized endogenous TPO, causing protracted thrombocytopenia in some patients. The second-generation TPO receptor agonist romiplostim, having no homology to TPO, was developed to circumvent potential immunogenicity. We examined the development of binding and neutralizing antibodies to romiplostim and TPO among pediatric patients with primary immune thrombocytopenia (ITP) in 5 clinical trials and a global postmarketing registry. In the trials, 25 of 280 (8.9%) patients developed anti-romiplostim binding antibodies. The first positive result was detected 67 weeks (median) after romiplostim treatment was initiated. The median romiplostim dose was 8 µg/kg, and the median platelet count was 87 × 109/L. Most patients who developed anti-romiplostim binding antibodies (18 of 25 [72%]) had ≥90% of platelet assessments showing a response. Anti-romiplostim neutralizing antibodies developed in 8 of 280 (2.9%) patients. The development of anti-romiplostim neutralizing antibodies was unrelated to the romiplostim dose, and most patients who developed the antibodies (7 of 8 [88%]) had platelet response. Nine of 279 (3.2%) patients developed anti-TPO binding antibodies, and 1 (0.4%) developed transient anti-TPO neutralizing antibodies. In 8 patients who developed anti-romiplostim neutralizing antibodies, no TPO cross-reactivity was observed. In the postmarketing registry, 3 of 19 (15.8%) patients developed anti-romiplostim binding antibodies; 1 (5.3%) patient developed anti-romiplostim neutralizing antibodies. These results suggest that immunogenicity to romiplostim occurs infrequently in pediatric patients with ITP and is generally not associated with loss of platelet response or other negative clinical sequelae.

The structure, function, and clinical use of the thrombopoietin receptor agonist avatrombopag

Thrombopoietin regulates platelet production through activation of the thrombopoietin receptor (TPO-R). TPO-R agonists (TPO-RAs) are available to treat thrombocytopenia in chronic immune thrombocytopenia (ITP), chronic liver disease (CLD) patients who are undergoing a procedure, severe aplastic anemia (SAA), and hepatitis C virus (HCV) infection. There are four TPO-RAs approved in the US and Europe: romiplostim (ITP), eltrombopag (ITP, SAA, HCV), avatrombopag (ITP, CLD), and lusutrombopag (CLD). It is important to understand pharmacological characteristics of these agents when evaluating treatment options. Avatrombopag interacts with the transmembrane domain of the TPO-RA and does not compete with endogenous thrombopoietin for TPO-R binding. Structural differences between avatrombopag and other TPO-RAs may impart differential downstream effects on cell signaling pathways, potentially resulting in clinically relevant differences in outcome. Avatrombopag has a favorable pharmacological profile with similar exposure in Japanese, Chinese, or Caucasian patients and no drug-drug interactions, food interactions, or potential for chelation.

An Update on Pediatric Immune Thrombocytopenia (ITP): Differentiating Primary ITP, IPD, and PID

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia in children and is caused by both immune-mediated decreased platelet production and increased platelet destruction. In the absence of a diagnostic test, ITP must be differentiated from other thrombocytopenic disorders, including inherited platelet disorders (IPD). In addition, a diagnosis of secondary ITP due to a primary immune deficiency (PID) with immune dysregulation may not be apparent at diagnosis but can alter management and should be considered in an expanding number of clinical scenarios. The diagnostic evaluation of children with thrombocytopenia will vary based on the clinical history and laboratory features. Access to genotyping has broadened the ability to specify the etiology of thrombocytopenia, while increasing access to immunophenotyping, functional immunologic and platelet assays, and biochemical markers has allowed for more in-depth evaluation of patients. With this greater availability of testing, diagnostic algorithms in patients with thrombocytopenia have become complex. In this article, we highlight the diagnostic evaluation of thrombocytopenia in children with a focus on ITP, including consideration of underlying genetic and immune disorders, and utilize hypothetical patient cases to describe disease manifestations and strategies for treatment of pediatric ITP.

Sequential Use of Romiplostim after Eltrombopag for Refractory Thrombocytopenia in Hydrocarbon-Induced Myelodysplasia

We describe the clinical course of a 65-year-old male patient who suffered from hydrocarbon-induced myelodysplasia and was successfully treated with the thrombopoietin receptor agonist (TPO-RA), romiplostim. Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis, cytopenias, and increased risk of leukemic transformation. Here, we present a clinical vignette of MDS-associated thrombocytopenia refractory to first-line drugs as well as the TPO-RA, eltrombopag. To date, romiplostim is an U.S. Food and Drug Administration (FDA)-approved drug for idiopathic thrombocytopenic purpura and thrombocytopenia secondary to liver disease. Of note, currently the FDA advises against its use in MDS based on previous long-term safety concerns. Since the therapeutic options for thrombocytopenia in MDS patients are sparse, repurposing and reassessing romiplostim in this setting have been the focus of recent studies. At the time of writing, no published double-blind randomized clinical trials have conducted a head-to-head comparison between romiplostim and eltrombopag in thrombocytopenic MDS patients. To the best of our knowledge, for a thrombocytopenic patient in the setting of MDS, this is the first documented report of refractory clinical response after a 2-year use of eltrombopag in which replacement of treatment with romiplostim resulted in sustained physiological counts of thrombocytes within four weeks.

Romiplostim in children with newly diagnosed or persistent primary immune thrombocytopenia

Immune thrombocytopenia (ITP) is a disease of heterogenous origin characterized by low platelet counts and an increased bleeding tendency. Three disease phases have been described: newly diagnosed (≤ 3 months after diagnosis), persistent (> 3-12 months after diagnosis), and chronic (> 12 months after diagnosis). The majority of children with ITP have short-lived disease and will not need treatment. For children with newly diagnosed ITP, who have increased bleeding symptoms, short courses of steroids are recommended. In children who do not respond to first-line treatment or who become steroid dependent, thrombopoietin receptor agonists (TPO-RAs) are recommended because of their efficacy and safety profiles. In this narrative review, we evaluate the available evidence on the use of the TPO-RA romiplostim to treat children with newly diagnosed or persistent ITP and identify data from five clinical trials, five real-world studies, and a case report. While the data are more limited for children with newly diagnosed ITP than for persistent ITP, the collective body of evidence suggests that romiplostim is efficacious in increasing platelet counts in children with newly diagnosed or persistent ITP and may result in long-lasting treatment-free responses in some patients. Furthermore, romiplostim was found to be well tolerated in the identified studies. Collectively, the data suggest that earlier treatment with romiplostim may help children to avoid the side effects associated with corticosteroid use and reduce the need for subsequent treatment.

Experts' review: the emerging roles of romiplostim in immune thrombocytopenia (ITP)

INTRODUCTION

The management of ITP has in recent years been transformed from reliance on immunosuppressants and splenectomy to targeted therapy with thrombopoietin receptor agonists (TPO-RA) that directly stimulate platelet production in the bone marrow. This has reduced the long-term infective complications and toxicities associated with the use of potent immunosuppressants and splenectomy. The welltolerated romiplostim, itself a novel drug construct called peptibody, has established itself, alongside other TPO-RA as the preferred 2nd line therapy in major international guidelines on treatment of ITP.

AREAS COVERED

This review summarizes the data from early licensing trials of romiplostim and discusses the real-world experience to date, the unexpected emerging data on treatment-free long-term remission achieved using TPO-RA, and the case for its early introduction in the therapeutic pathway. The emerging risk of thrombosis is also discussed.

EXPERT OPINION

The use of romiplostim and other TPO-RA will be increasingly brought forward in the management pathway of ITP with the prospect of modifying the long-term outcome of the disease by increasing sustained treatment-free remission. With the prospect of several new targeted therapies been introduced into clinical practice, TPO-RA will likely be a key component of future combination therapies for difficult cases.

A Review of Romiplostim Mechanism of Action and Clinical Applicability

Thrombocytopenia results from a variety of conditions, including radiation, chemotherapy, autoimmune disease, bone marrow disorders, pathologic conditions associated with surgical procedures, hematopoietic stem cell transplant (HSCT), and hematologic disorders associated with severe aplastic anemia. Immune thrombocytopenia (ITP) is caused by immune reactions that accelerate destruction and reduce production of platelets. Thrombopoietin (TPO) is a critical component of platelet production pathways, and TPO receptor agonists (TPO-RAs) are important for the management of ITP by increasing platelet production and reducing the need for other treatments. Romiplostim is a TPO-RA approved for use in patients with ITP in the United States, European Union, Australia, and several countries in Africa and Asia, as well as for use in patients with refractory aplastic anemia in Japan and Korea. Romiplostim binds to and activates the TPO receptor on megakaryocyte precursors, thus promoting cell proliferation and viability, resulting in increased platelet production. Through this mechanism, romiplostim reduces the need for other treatments and decreases bleeding events in patients with thrombocytopenia. In addition to its efficacy in ITP, studies have shown that romiplostim is effective in improving platelet counts in various settings, thereby highlighting the versatility of romiplostim. The efficacy of romiplostim in such disorders is currently under investigation. Here, we review the structure, mechanism, pharmacokinetics, and pharmacodynamics of romiplostim. We also summarize the clinical evidence supporting its use in ITP and other disorders that involve thrombocytopenia, including chemotherapy-induced thrombocytopenia, aplastic anemia, acute radiation syndrome, perisurgical thrombocytopenia, post-HSCT thrombocytopenia, and liver disease.

Phase 2 multiple-dose study of an FcRn inhibitor, rozanolixizumab, in patients with primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is a predominantly immunoglobulin G (IgG)-autoantibody-mediated disease characterized by isolated thrombocytopenia. Rozanolixizumab, a subcutaneously infused humanized monoclonal anti-neonatal Fc receptor (FcRn) antibody, reduced serum IgG in healthy volunteers. In this phase 2, multicenter, open-label study, patients with persistent/chronic primary ITP received 1 to 5 once-weekly subcutaneous infusions of rozanolixizumab (cumulative doses, 15-21 mg/kg). Primary objectives were safety and tolerability, and secondary objectives were clinical efficacy (change in platelet count) and pharmacodynamic effect (change in IgG). In all, 51 (77.3%) of 66 patients reported 1 or more adverse events (AEs), all mild-to-moderate, most commonly headaches (26 [39.4%] of 66), of which 15 were treatment related. Four patients had serious AEs, but none were treatment related. No AEs resulted in discontinuation of the study drug. No serious infections occurred. Platelet counts of ≥50 × 109/L were achieved at least once at any time after multiple infusions (5 × 4, 3 × 7, or 2 × 10 mg/kg: 35.7%, 35.7%, and 45.5% of patients, respectively) or single infusions (15 or 20 mg/kg: 66.7% and 54.5% patients, respectively). Minimum mean IgG levels and maximum mean platelet counts both occurred by day 8 in the higher (15 and 20 mg/kg) single-dose cohorts and maximum platelet count occurred by day 11 onward in the multiple-dose cohorts. No clinically meaningful changes occurred in IgA, IgM, IgE, or albumin levels. In patients with persistent/chronic primary ITP, rozanolixizumab demonstrated a favorable safety profile and rapid, substantial platelet increases concordant with substantial IgG reductions, especially with single doses. By day 8, in the 15 and 20 mg/kg single-dose cohorts, >50% patients achieved clinically relevant platelet responses (≥50 × 109/L), coinciding with the lowest mean IgG levels. These data support phase 3 development of rozanolixizumab in persistent/chronic primary ITP. This trial was registered at www.clinicaltrials.gov as #NCT02718716.

Thrombosis in immune thrombocytopenia - current status and future perspectives

Immune thrombocytopenia (ITP) is an autoimmune disorder in which a combination of defective platelet production and enhanced clearance leads to thrombocytopenia. The primary aim for therapy in patients with this condition is the prevention of bleeding. However, more recently, increased rates of venous and arterial thrombotic events have been reported in ITP, even in the context of marked thrombocytopenia. In this review we discuss the epidemiology, aetiology and management of thrombotic events in these patients. We consider the impact of ITP therapies on the increased thrombotic risk, in particular the use of thrombopoietin-receptor agonists (TPO-RAs), as well as factors inherent to ITP itself. We also discuss the limited evidence available to guide clinicians in the treatment of these complex cases.

Clinical overview and practical considerations for optimizing romiplostim therapy in patients with immune thrombocytopenia

The fundamental treatment goal for patients with immune thrombocytopenia (ITP) is reduced or ameliorated bleeding. Although various treatment options exist for the management of ITP, recent advances have led to the approval of three thrombopoietin receptor agonists (TPO-RAs; romiplostim, eltrombopag, and avatrombopag) in the United States and European Union. Current treatment guidelines for ITP indicate that medical therapy is preferred over surgical therapy and support the use of TPO-RAs as early as 3 months after disease onset. More recent data are available on the use of romiplostim in patients who have had ITP for <1 year, and romiplostim is now indicated for the treatment of adults who have not responded adequately to initial treatment, as well as children aged ≥1 year who have had ITP for ≥6 months. Here we review the role of romiplostim in the management of ITP, with a focus on efficacy and safety data, emerging data on early use (beginning within 3 months of disease onset) and treatment-free remission, and practical considerations for optimal management of ITP.

Successful Use of Eltrombopag in a Young Child With Chronic Immune Thrombocytopenia

The disease course in a young girl with chronic immune thrombocytopenia (ITP) at the initial age of 19 months, treated with eltrombopag, was evaluated retrospectively and is presented as a case record and discussed against the background of the available literature. A stable response and reduction in clinical symptoms, over several years and without frequent dose changes, was achieved. Bleeding symptoms were mild to moderate and occurred particularly frequently in combination with low platelet counts. Raising the platelet count, in turn, was accompanied by a decreased bleeding tendency. Eltrombopag was tolerated well. No new safety signals were observed during the treatment. Based on a follow-up of more than 2.5 years, our case confirms that a child with chronic ITP can benefit from treatment with eltrombopag in the regular care setting. We assume that early treatment with a thrombopoietin receptor agonist could save many children from repeated and lengthy hospitalizations with intravenous immunoglobulins and prolonged administration of corticosteroids.

Romiplostim treatment for children with immune thrombocytopenia: Results of an integrated database of five clinical trials

BACKGROUND

Treatment for chronic immune thrombocytopenia (cITP) in children is largely limited to immunosuppressive agents. Thrombopoietin receptor agonists (TRAs) have been used to treat cITP in adults for over a decade. The objective of this integrated analysis was to examine the safety and efficacy of the TRA romiplostim in children with ITP.

METHODS

We examined efficacy and safety in children with ITP across five romiplostim trials: final data from two double-blind placebo-controlled trials and two open-label extensions, and interim data from an ongoing single-arm trial.

RESULTS

Patients (n = 24 initially placebo; n = 262 initially romiplostim) had a median age of 10.0 years (Q1: 6.0, Q3: 13.0), ITP duration of 1.9 years (Q1: 1.0, Q3: 4.0), and baseline platelet count of 14.3 × 10⁹ /L (Q1: 7.5, Q3: 23.0). Among 282 patients receiving romiplostim, median treatment duration was 65 weeks (range 8-471 weeks) and median weekly dose was 6.6 μg/kg (range 0.1-9.7 μg/kg). Overall, 89% of romiplostim-treated patients had platelet responses. Nineteen patients (7%) maintained treatment-free responses for ≥6 months while withholding all ITP therapy. Grade 3 and 4 adverse events of bleeding occurred in 10% and <1% of romiplostim-treated patients, respectively. Twenty-five percent of patients had a serious adverse event, most commonly epistaxis (6%). Seven patients (2%) had neutralizing antibodies against romiplostim postbaseline and none had neutralizing antibodies against endogenous thrombopoietin. Efficacy and safety results appeared similar between children with ITP for ≤12 months and >12 months at baseline.

CONCLUSIONS

Across five pediatric clinical trials, romiplostim was well tolerated. Most patients had a platelet response; some maintained responses for at least 6 months while withholding all ITP therapy.

American Society of Hematology 2019 guidelines for immune thrombocytopenia

BACKGROUND

Despite an increase in the number of therapies available to treat patients with immune thrombocytopenia (ITP), there are minimal data from randomized trials to assist physicians with the management of patients.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about the management of ITP.

METHODS

In 2015, ASH formed a multidisciplinary guideline panel that included 8 adult clinical experts, 5 pediatric clinical experts, 2 methodologists with expertise in ITP, and 2 patient representatives. The panel was balanced to minimize potential bias from conflicts of interest. The panel reviewed the ASH 2011 guideline recommendations and prioritized questions. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including evidence-to-decision frameworks, to appraise evidence (up to May 2017) and formulate recommendations.

RESULTS

The panel agreed on 21 recommendations covering management of ITP in adults and children with newly diagnosed, persistent, and chronic disease refractory to first-line therapy who have non-life-threatening bleeding. Management approaches included: observation, corticosteroids, IV immunoglobulin, anti-D immunoglobulin, rituximab, splenectomy, and thrombopoietin receptor agonists.

CONCLUSIONS

There was a lack of evidence to support strong recommendations for various management approaches. In general, strategies that avoided medication side effects were favored. A large focus was placed on shared decision-making, especially with regard to second-line therapy. Future research should apply standard corticosteroid-dosing regimens, report patient-reported outcomes, and include cost-analysis evaluations.

Outcomes of Eltrombopag Treatment and Development of Iron Deficiency in Children with Immune Thrombocytopenia in Turkey

Objective

Immune thrombocytopenia (ITP) is a rare autoimmune disease and hematologic disorder characterized by reduced platelet counts that can result in significant symptoms, such as bleeding, bruising, epistaxis, or petechiae. The thrombopoietin receptor agonist eltrombopag (EPAG) is a second-line agent used to treat chronic ITP purpura in adults and children.

Materials and Methods

The present retrospective study evaluated the efficacy, safety, and side effects of EPAG treatment in pediatric patients with acute refractory and chronic immune thrombocytopenia, particularly focusing on iron-deficiency anemia.

Results

The diagnosis was chronic ITP in 89 patients and acute refractory ITP in 16 patients. The mean age of patients was 9.5±4.5 years (minimum-maximum: 1.2-18 years) at the beginning of EPAG treatment. The overall response rate was 74.3% (n=78). The mean time for platelet count of ≥50x109/L was 11.6±8 weeks (range: 1-34 weeks). The treatment was stopped for 27 patients (25.7%) at an average of 6.8±9 months (range: 1-38 months). The reason for discontinuation was lack of response in 18 patients, nonadherence in 4 patients, and hepatotoxicity in 2 patients. Response to treatment continued for an average of 4 months after cessation of EPAG in 3 patients.

Conclusion

Results of the current study imply that EPAG is an effective therapeutic option in pediatric patients with acute refractory and chronic ITP. However, patients must be closely monitored for response and side effects during treatment, and especially for iron deficiency.

Romiplostim for the management of pediatric immune thrombocytopenia: drug development and current practice

Since successful cloning of thrombopoietin (TPO) in 1994, significant advances have been made in the development of recombinant TPO receptor agonists. The US Food and Drug Administration (FDA) has approved 2 agents for use in patients with immune thrombocytopenia (ITP): eltrombopag and romiplostim. Romiplostim is a once-weekly subcutaneous injection that has been shown to increase the platelet count, lessen bleeding, and reduce concurrent medication use in adults with ITP. In December 2018, the US FDA approved romiplostim for use in pediatric patients ≥1 year of age with ITP of >6 months' duration and insufficient response to corticosteroids, immunoglobulins, or splenectomy, based on similarly favorable clinical trial data. In addition, romiplostim is well tolerated, making it an attractive option for the treatment of children. Expansion of off-label romiplostim use is being reported in children for ITP <6 months, neonatal thrombocytopenia, hereditary thrombocytopenias, and chemotherapy- and bone marrow transplant-associated thrombocytopenia. We review here the development of romiplostim with a focus on pediatric use.

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.

The role of romiplostim for pediatric patients with immune thrombocytopenia

The thrombopoietin receptor agonists (TPO-RAs) are a class of platelet growth factors used to treat immune thrombocytopenia (ITP) in children and adults. Romiplostim is a peptide TPO-RA approved for over a decade to treat adults with ITP but was just recently US Food and Drug Administration approved to manage ITP in children 1 year of age and older who have had an inadequate response to corticosteroids, intravenous immunoglobulin, or splenectomy. Like the small molecule TPO-RA eltrombopag, romiplostim offers a high clinical response rate in pediatric patients with ITP, but requires use over an extended, and possibly indefinite, duration. This review is a critical appraisal of the role of romiplostim in pediatric ITP, discussing the safety and efficacy of this agent in clinical trials of children and adults and defining the patients most likely to benefit from romiplostim treatment. The treating hematologist is additionally provided guidance with treatment goals, dosing strategies, toxicity management, and indications for discontinuation.

Thrombopoietin receptor agonists for the treatment of primary immune thrombocytopenia: a meta-analysis and systematic review

Previous meta-analyses reported discordant results on the efficacy and safety of thrombopoietin receptor agonists (TPO-RA) as second-line treatment in patients with immune thrombocytopenia (ITP). We conducted a meta-analysis of primary ITP treatment with the TPO-RA Romiplostim, Eltrombopag and Avatrombopag, including additional studies and relevant endpoints. We searched MEDLINE, EMBASE and CENTRAL for randomized clinical trials (RCTs) and cohort studies on TPO-RA in ITP published until December 31, 2018. The primary endpoints were: risk ratio (RR) of treatment failure and bleeding of WHO grade ≥2; rate of remission after discontinuation of treatment. The principal safety outcome was RR and incidence of thrombotic events and liver damage. From 1044 identified records we selected 16 RCTs and 19 cohort studies. RCTs included 909 patients assigned to TPO-RA and 427 to the control arm. Treatment failure was observed in 21% TPO-RA-treated patients and 47% control arm patients (RR = 0.42, 95% CI 0.33-0.53) in RCTs during a median follow-up of 13 weeks, and in 29% TPO-RA-treated patients in cohort studies, during a median follow-up of 69 weeks. The incidence of remission after TPO discontinuation was 18% (5-36%). RR of WHO grade ≥2 bleeding was 0.58 (0.38-0.86) in TPO-RA-treated patients, compared to control arm patients. Adverse events were rare and not significantly different in the two groups of patients. All-cause mortality was significantly lower with TPO-RA (RR 0.21, 95% CI, 0.06-0.68). In conclusion, TPO-RA are effective and safe in patients with ITP, even in the long term.

Use of Eltrombopag in Children With Chronic Immune Thrombocytopenia (ITP): A Real Life Retrospective Multicenter Experience of the Italian Association of Pediatric Hematology and Oncology (AIEOP)

Background: The thrombopoietin receptor agonist eltrombopag has been shown to be safe and effective for children with chronic immune thrombocytopenia (ITP). The aim of the present study was to characterize eltrombopag use in current clinical practice.

Material and Methods: This is a retrospective multicenter study conducted in 17 centers affiliated to the Italian Association of Pediatric Hematology and Oncology (AIEOP). The primary objective of the study was to determine the prevalence of eltrombopag use in Italian children affected by chronic ITP, after EMA authorization for pediatric age. The secondary objective was to assess efficacy in the first 6 months and safety during the whole period of eltrombopag treatment in current clinical practice. A total of 386 children with chronic ITP were retrospectively enrolled and eligible for analysis. Among these patients, 71 received eltrombopag.

Results: The prevalence of eltrombopag use was 19% (95% CI 0.15–0.23). Thirty-one patients (44%) were male and 40 patients (56%) were female. The median age at the first dose of eltrombopag was 12 years (3–17 years). The median duration of eltrombopag treatment was 11 months (1–32 months) and the median starting dose was 50 mg/day (12, 5–75 mg/day). Thirty-two patients (45%) required one or more concomitant ITP medications during the first 6 months of treatment with eltrombopag. Thirty-nine patients (55%) never required concomitant medications. Median platelet counts and proportion of patients achieving the target platelet count of at least 30 × 10⁹/L and 100 × 10⁹/L significantly increased during the first 6 months of treatment (p < 0.0001). Additionally, eltrombopag has been proved effective in the absence of concomitant therapies. The most common Adverse Events were headache (7%) and thrombocytosis (6%).

Conclusion: Our study highlighted the crucial role of eltrombopag as second line treatment in children with chronic ITP.

Updated international consensus report on the investigation and management of primary immune thrombocytopenia

Over the last decade, there have been numerous developments and changes in treatment practices for the management of patients with immune thrombocytopenia (ITP). This article is an update of the International Consensus Report published in 2010. A critical review was performed to identify all relevant articles published between 2009 and 2018. An expert panel screened, reviewed, and graded the studies and formulated the updated consensus recommendations based on the new data. The final document provides consensus recommendations on the diagnosis and management of ITP in adults, during pregnancy, and in children, as well as quality-of-life considerations.

Current Advance in Thrombopoietin Receptor Agonists in the Management of Thrombocytopenia Associated With Chronic Liver Disease: Focus on Avatrombopag

Chronic liver disease (CLD) is a condition that progresses over time toward advanced disease state which is known as liver cirrhosis. Liver cirrhosis leads to dangerous health problems among people living across the world. One such problem that observed in about 75% of cirrhotic patients is thrombocytopenia; which in turn associated with poor prognosis and recovery from CLD. Beyond these, thrombocytopenia in cirrhotic patients led to impairment of coagulation cascade and significantly influenced the utilization of effective mechanism in the management of CLD. By nature, treatment of CLD involves invasive diagnostic and treatment procedures; therefore, in the presence of thrombocytopenia implementing these methods put the lives of patients in a critical health problem due to increased risk of bleeding and mortality. Because of these reasons, prophylactic transfusion of platelets is considered to be one of the most effective options that reduce the risk of bleeding in patients with CLD that required to undergo an invasive procedure. Although platelet transfusion presented with significant advantages in facilitating the invasive procedure in patients with CLD, refractoriness with repeated use and various problems associated with its transfusion limit the continuous utilization of this important option. With these challenges and current advance in the knowledge of thrombopoiesis, the development of relatively safe and alternative drugs that enhance the production of platelets by interacting with thrombopoietin receptor agonists provides a promising option to platelet transfusion. The discovery and approval of romiplostim and eltrombopag in August 2008 and November 2008, respectively, for the treatment of chronic immune thrombocytopenia paved a way and followed by the Food and Drug Administration (FDA) approval of 2 potentially advantageous drugs, lusutrombopag, and avatrombopag, in 2018 for the treatment of thrombocytopenia in patients with CLD that required to undergo elective surgery. Therefore, this review aims to assess pathogenesis of thrombocytopenia and its challenges in the management of liver-related issues and, more importantly, gives emphasis to address the potential use of avatrombopag in the treatment of thrombocytopenia underlying CLD, its pharmacokinetics and pharmacodynamics, as well as its toxicological profiles by presenting the most commonly reported adverse events in various trials.

Mechanisms and therapeutic prospects of thrombopoietin receptor agonists

The second-generation thrombopoietin (TPO) receptor agonists eltrombopag and romiplostim are potent activators of megakaryopoiesis and represent a growing treatment option for patients with thrombocytopenic hematological disorders. Both TPO receptor agonists have been approved worldwide for the treatment of children and adults with chronic immune thrombocytopenia. In the EU and USA, eltrombopag is approved for the treatment of patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy and in the USA for the first-line treatment of severe aplastic anemia in combination with immunosuppressive therapy. Eltrombopag has also shown efficacy in several other disease settings, for example, chemotherapy-induced thrombocytopenia, selected inherited thrombocytopenias, and myelodysplastic syndromes. While both TPO receptor agonists stimulate TPO receptor signaling and enhance megakaryopoiesis, their vastly different biochemical structures bestow upon them markedly different molecular and functional properties. Here, we review and discuss results from preclinical and clinical studies on the functional and molecular mechanisms of action of this new class of drug.

Current and emerging treatments for immune thrombocytopenia

Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease. Even though there are many treatments available, some patients remain resistant to multiple treatments. Therefore, it is very important to develop new treatment options. Areas covered: Here, the authors summarize several current and emerging treatments developed for ITP in recent years. They include a summary of their mechanisms of action and clinical trial results. Expert opinion: At present, the first-line treatment of ITP is glucocorticoid and intravenous immunoglobulin (IVIg). Other traditional therapies include splenectomy, thrombopoietin (TPO), rituximab and other immunosuppressive agents. The several emerging treatments developed recently for ITP may change the treatment pattern in the future.

Acquired amegakaryocytic thrombocytopenia as a rare cause of thrombocytopenia during pregnancy

A rare case of acquired amegakaryocytic thrombocytopenia (AATP) in a 35-year-old woman who presented with anaemia and thrombocytopenia at 22 weeks gestation. The first diagnostic impression was of an evolving aplastic anaemia; however, the patient was simultaneously diagnosed with severe vitamin B₁₂ deficiency in the setting of vegetarianism. Once the cyanocobalamin deficiency was corrected, a repeat bone marrow biopsy revealed an isolated depletion of megakaryocytes, which suggested the diagnosis of AATP. Supportive care was provided for her anaemia and thrombocytopenia and she delivered a healthy baby girl with a normal platelet count. The patient was subsequently started on romiplostim with steady improvement in her platelet counts. This rare AATP case presentation highlights the importance of a well-structured diagnostic approach to thrombocytopenia during pregnancy and supports the successful use of thrombopoietin agonists for the management of AATP.

Thrombopoietin receptor agonists: ten years later

The two thrombopoietin receptor agonists (TPO-RA), eltrombopag and romiplostim, were licensed in the US for treatment of immune thrombocytopenia (ITP) in 2008 and, since then, their use has progressively increased around the world; they are currently used in more than 100 countries. The six largest randomized controlled trials conducted in ITP have used one of these two agents. All studies have demonstrated a platelet response rate between 50-90%, depending on the criteria used, with good safety and tolerability. TPO-RA were shown to be effective in reducing bleeding and the need for concomitant or rescue medication. Many other investigations of their mechanism of effect, prospective and retrospective trials, and studies focusing on toxicity have been performed widening our knowledge of these two agents. Initial concerns on issues such as myelofibrosis have not been confirmed. Only a small number of patients develop moderate-severe reticulin fibrosis and/or collagen fibrosis; however, these are usually reversed after discontinuation of TPO-RA. Studies indicate, however, that TPO-RA may increase the risk of venous thromboembolism. Both TPO-RA are currently approved in patients with chronic ITP aged >1-year who are refractory to at least one other treatment. Eltrombopag has acquired two additional indications: severe aplastic anemia refractory to first-line treatment and hepatitis C patients undergoing treatment with interferon-ribavirin. Despite these wide-ranging studies, important questions still need to be answered. This summary review on TPO-RA will summarize what is known regarding efficacy in ITP, evaluate safety concerns in more depth, and focus on the questions that remain.

Thrombopoietin receptor agonist switch in children with persistent and chronic severe immune thrombocytopenia: A retrospective analysis in a large tertiary center

We retrospectively analyzed sequential therapy with romiplostim and eltrombopag in 23 children with immune thrombocytopenia: switching from romiplostim to eltrombopag (10 patients) or vice versa (13 patients). The median age of patients at enrollment in the study was 5.6 years (2-15 years). Switching from romiplostim to eltrombopag was effective in eight (80%) patients, whereas switching from eltrombopag to romiplostim was effective in eight (62%) patients. The response rate was similar in patients failing the first thrombopoietin receptor agonist and those who had previous response. To date, all responders continue to maintain platelets over 50 × 10⁹ /L at 13-39 months after switching.

Romiplostim for Immune Thrombocytopenia in Neuroblastoma Patients Receiving Chemotherapy

Thrombocytopenia, a serious complication of myelosuppressive chemotherapy in cancer patients, is managed with platelet transfusions until recovery of platelet counts. However, children receiving chemotherapy can rarely develop immune thrombocytopenia (ITP) that is refractory to transfused platelets. This limits the ability to achieve adequate platelet counts and administer further myelosuppressive chemotherapy safely, especially if first-line ITP therapy is ineffective. We report 2 cases of intravenous immunoglobulin refractory ITP in children receiving chemotherapy for high-risk neuroblastoma. ITP was successfully treated with the thrombopoietin-receptor-agonist romiplostim, allowing safe and timely continuation of antineuroblastoma therapies in these high-risk patients.

Long-term treatment with romiplostim and treatment-free platelet responses in children with chronic immune thrombocytopenia

Children with immune thrombocytopenia for ≥6 months completing a romiplostim study received weekly subcutaneous romiplostim (1-10 μg/kg targeting platelet counts of 50-200×10⁹/L) in this extension to examine romiplostim’s long-term safety and efficacy. Sixty-five children received romiplostim for a median of 2.6 years (range: 0.1-7.0 years). Median baseline age was 11 years (range: 3-18 years) and platelet count was 28×10⁹/L (range: 2-458×10⁹/L). No patient discontinued treatment for an adverse event. Median average weekly dose was 4.8 mg/kg (range: 0.1-10 mg/kg); median platelet counts remained >50×10⁹/L, starting at week 2. Nearly all patients (94%) had ≥1 platelet response (≥50×10⁹/L, no rescue medication in the previous 4 weeks), 72% had responded at ≥75% of visits, and 58% had responded at ≥90% of visits. Treatment-free response (platelets ≥50×10⁹/L ≥24 weeks without immune thrombocytopenia treatment) was seen in 15 of 65 patients while withholding romiplostim doses. At onset of treatment-free response, the nine girls and six boys had a median immune thrombocytopenia duration of four years (range: 1-12 years) and had received romiplostim for two years (range: 1-6 years). At last observation, treatment-free responses lasted for a median of one year (range: 0.4-2.1 years), with 14 of 15 patients still in treatment-free response. Younger age at first dose and platelet count >200×10⁹/L in the first four weeks were associated with treatment-free responses. In this 7-year open-label extension, three-quarters of the patients responded ≥75% of the time, and romiplostim was well tolerated, with no substantial treatment-related adverse events. Importantly, 23% of children maintained treatment-free platelet responses while withholding romiplostim and all other immune thrombocytopenia medications for ≥6 months. (Registered at clinicaltrials.gov identifier: 01071954)

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.

Evidence-based management of immune thrombocytopenia: ASH guideline update

In 1996 and 2011, the American Society of Hematology (ASH) supported efforts to create guidelines for the diagnosis and management of patients with immune thrombocytopenia (ITP). These guidelines used different approaches to arrive at recommendations for testing and treatment. Despite differences in methodology, in both cases there was a paucity of randomized trials to inform recommendations. As data on the diagnosis and management of ITP expands, the ASH Committee on Quality is dedicated to maintaining updated guidelines representing recent evidence and guideline methodology. Here, we will review the updated ASH guidelines on ITP with a focus on recommendations with new understanding and future research to close knowledge gaps.