Thrombopoietic agents

Efficacy and Safety of Biosimilar Romiplostim Versus Innovator Romiplostim in Patients with Chronic Immune Thrombocytopenia

Romiplostim is a Food and Drug Administration (FDA)-approved therapy for immune thrombocytopenia (ITP). Biosimilar is a biological product that has no clinical meaningful difference from an existing FDA-approved reference product. It has a potential of lowering health-care-related cost. Biosimilar of romiplostim can be made available to patients with ITP at a low cost and can be beneficial in providing the best therapy. Thus, the efficacy and safety of biosimilar romiplostim (ENZ110) was compared with innovator romiplostim (Nplate) with respect to platelet response in patients with chronic ITP. This was a prospective, multicenter, randomized, and double-blind clinical trial. Patients with chronic ITP, aged 18-65 years, were enrolled in a study and were randomized to receive either ENZ110 or Nplate in a 3:1 ratio for a treatment period of 12 weeks, respectively. After completion of the treatment period, the patients were followed-up for one week to evaluate the platelet response and to monitor the adverse events (AEs). Over the duration of 12 weeks, platelet response of > 50 × 109/L was achieved in 85.3% patients treated with ENZ110 and in 75.0% patients treated with Nplate in per protocol population. In intent-to-treat population, 83.8% patients with ENZ110 and 76.9% patients with Nplate achieved a platelet response of > 50 × 109/L. In the ENZ110 group, 111 AEs were recorded in 66.7% patients, while 18 AEs were reported in 61.5% patients in the Nplate group. The study demonstrated non-inferiority with comparable efficacy and safety between biosimilar romiplostim and innovator romiplostim in patients with chronic ITP. Trial registration number and date of registration: CTRI/2019/04/018614.

Risk of thrombotic events in immune thrombocytopenia patients treated with thrombopoietic agents: a systematic review and meta-analysis

BACKGROUND

Immune thrombocytopenia (ITP), which is a well-known hemorrhagic disorder characterized by low platelet counts, has been shown to be associated with the risk of thrombosis. Thrombopoietic agents (TAs) are extensively used as second-line treatments for ITP, effectively reducing the risk of hemorrhage. However, thrombosis, a potential adverse effect of TAs, raises clinical challenges.

METHODS

The MEDLINE(PubMed), Embase, and the Cochrane Library databases were systematically searched for relevant studies, including both single-arm trials and randomized controlled trials (RCTs), without language restrictions.

RESULTS

A total of 17 RCTs comprising 2,105 patients and 29 single-arm trials comprising 3,227 patients were included. In the single-arm meta-analysis, the pooled rate of overall thrombotic events in ITP patients receiving TAs was 2.2% (95% CI 1.0% - 3.7%). In RCTs, a higher incidence of thrombosis (33/1425 vs. 4/680) and higher risk ratios (RR) of overall, arterial, and venous thrombotic events (1.73, 95% CI [0.88, 3.39], P = 0.113; RR 1.98, 95% CI [0.80, 4.92], P = 0.141; RR 1.06, 95% CI [0.46, 2.41], P = 0.895, respectively) were observed in the TAs group than in the control group, although the differences were not significant. Subgroup analysis demonstrated that hetrombopag was the only TA with no increased thrombotic risk (rate 0.3% 95% CI [0.0 - 1.5%]; RR 0.76, 95% CI [0.03, 18.41], P = 0.864) compared to eltrombopag, avatrombopag, romiplostim, and rhTPO. Subgroup analyses also revealed that ITP patients with advanced age (3.7% vs. 1.3%, P = 0.132) or with a thrombotic history (3.0% vs. 1.4%, P = 0.257), and patients who received TAs therapy for a long duration (4.7% vs. 0.1%, P < 0.001) had an increased risk of thrombosis.

CONCLUSION

Our findings suggest ITP patients treated with TAs have a nonsignificantly higher risk of overall, arterial, and venous thrombotic events. Furthermore, hetrombopag is the recommended TA to avoid thrombophilia. Patients receiving long-term TAs, as well as elderly ITP patients or those with a history of thrombosis, face an increased thrombotic risk. In general, clinicians should consider potential thrombotic risks, address underlying risk factors, and ensure ongoing monitoring and follow-up when treating ITP patients with TAs.

Novel chemical-structure TPOR agonist, TMEA, promotes megakaryocytes differentiation and thrombopoiesis via mTOR and ERK signalings

BACKGROUND

Non-peptide thrombopoietin receptor (TPOR) agonists are promising therapies for the mitigation and treatment of thrombocytopenia. However, only few agents are available as safe and effective for stimulating platelet production for thrombocytopenic patients in the clinic.

PURPOSE

This study aimed to develop a novel small molecule TPOR agonist and investigate its underlying regulation of function in megakaryocytes (MKs) differentiation and thrombopoiesis.

METHODS

A potential active compound that promotes MKs differentiation and thrombopoiesis was obtained by machine learning (ML). Meanwhile, the effect was verified in zebrafish model, HEL and Meg-01 cells. Next, the key regulatory target was identified by Drug Affinity Responsive Target Stabilization Assay (DARTS), Cellular Thermal Shift Assay (CETSA), and molecular simulation experiments. After that, RNA-sequencing (RNA-seq) was used to further confirm the associated pathways and evaluate the gene expression induced during MK differentiation. In vivo, irradiation (IR) mice, C57BL/6N-TPOR^em1cyagen (Tpor^-/-) mice were constructed by CRISPR/Cas9 technology to examine the therapeutic effect of TMEA on thrombocytopenia.

RESULTS

A natural chemical-structure small molecule TMEA was predicted to be a potential active compound based on ML. Obvious phenotypes of MKs differentiation were observed by TMEA induction in zebrafish model and TMEA could increase co-expression of CD41/CD42b, DNA content, and promote polyploidization and maturation of MKs in HEL and Meg-01 cells. Mechanically, TMEA could bind with TPOR protein and further regulate the PI3K/AKT/mTOR/P70S6K and MEK/ERK signal pathways. In vivo, TMEA evidently promoted platelet regeneration in mice with radiation-induced thrombocytopenia but had no effect on Tpor^-/- and C57BL/6 (WT) mice.

CONCLUSION

TMEA could serve as a novel TPOR agonist to promote MKs differentiation and thrombopoiesis via mTOR and ERK signaling and could potentially be created as a promising new drug to treat thrombocytopenia.

Analysis of predictors after partial splenic embolization for thrombocytopenia with liver cirrhosis

Blood transfusion, splenectomy, and partial splenic embolization (PSE) are generally performed for thrombocytopenia in patients with cirrhosis. Recently, thrombopoietin (TPO) agonists have become available, and investigations of patients who would benefit from them are necessary. Therefore, it is important to understand the fluctuations in cytokine levels associated with PSE. Therefore, fluctuations in platelet-associated immunoglobulin G (PAIgG), interleukin 6 (IL-6), and TPO levels with PSE were analyzed in this study. The study included 110 patients with liver cirrhosis and thrombocytopenia, with the aim of improving platelet counts. Fluctuations in PAIgG, IL-6, and TPO levels were investigated. The average splenic embolization ratio was 58.0% in patients with PSE. The platelet count rose significantly from 6.95 [5.40, 8.60] × 104/mL to 14.05 [10.43, 18.05] × 104/mL (P < .01), IL-6 rose significantly from 3.56 [2.53, 7.33] pg/mL to 18.90 [9.17, 32.95] pg/mL (P < .01), TPO rose significantly from 0.82 [0.52, 1.21] fmol/mL to 1.58 [0.97, 2.26] fmol/mL (P < .01), and PAIgG decreased significantly from 64.20 [38.33, 118.75] ng/107 cells to 37.50 [22.25, 70.00] ng/107 cells (P < .01). On multivariate analysis of factors related to the rate of platelet increase with PSE, primary biliary cholangitis (B = 0.475, P < .01), splenic embolization ratio (B = 0.75, P < .01), IL-6 change ratio (B = 0.019, P < .01), and PAIgG change ratio (B = -0.325, P < .01) were significant. When attempting to improve thrombocytopenia with PSE, adequate splenic embolization needs to be obtained together with improvements in IL-6, PAIgG, and TPO levels. With unsatisfactory improvement in thrombocytopenia, TPO agonist administration was considered.

Novel Therapies to Address Unmet Needs in ITP

Primary immune thrombocytopenia (ITP) is an autoimmune disorder that causes low platelet counts and subsequent bleeding risk. Although current corticosteroid-based ITP therapies are able to improve platelet counts, up to 70% of subjects with an ITP diagnosis do not achieve a sustained clinical response in the absence of treatment, thus requiring a second-line therapy option as well as additional care to prevent bleeding. Less than 40% of patients treated with thrombopoietin analogs, 60% of those treated with splenectomy, and 20% or fewer of those treated with rituximab or fostamatinib reach sustained remission in the absence of treatment. Therefore, optimizing therapeutic options for ITP management is mandatory. The pathophysiology of ITP is complex and involves several mechanisms that are apparently unrelated. These include the clearance of autoantibody-coated platelets by splenic macrophages or by the complement system, hepatic desialylated platelet destruction, and the inhibition of platelet production from megakaryocytes. The number of pathways involved may challenge treatment, but, at the same time, offer the possibility of unveiling a variety of new targets as the knowledge of the involved mechanisms progresses. The aim of this work, after revising the limitations of the current treatments, is to perform a thorough review of the mechanisms of action, pharmacokinetics/pharmacodynamics, efficacy, safety, and development stage of the novel ITP therapies under investigation. Hopefully, several of the options included herein may allow us to personalize ITP management according to the needs of each patient in the near future.

Craniofacial Bone Tissue Engineering: Current Approaches and Potential Therapy

Craniofacial bone defects can result from various disorders, including congenital malformations, tumor resection, infection, severe trauma, and accidents. Successfully regenerating cranial defects is an integral step to restore craniofacial function. However, challenges managing and controlling new bone tissue formation remain. Current advances in tissue engineering and regenerative medicine use innovative techniques to address these challenges. The use of biomaterials, stromal cells, and growth factors have demonstrated promising outcomes in vitro and in vivo. Natural and synthetic bone grafts combined with Mesenchymal Stromal Cells (MSCs) and growth factors have shown encouraging results in regenerating critical-size cranial defects. One of prevalent growth factors is Bone Morphogenetic Protein-2 (BMP-2). BMP-2 is defined as a gold standard growth factor that enhances new bone formation in vitro and in vivo. Recently, emerging evidence suggested that Megakaryocytes (MKs), induced by Thrombopoietin (TPO), show an increase in osteoblast proliferation in vitro and bone mass in vivo. Furthermore, a co-culture study shows mature MKs enhance MSC survival rate while maintaining their phenotype. Therefore, MKs can provide an insight as a potential therapy offering a safe and effective approach to regenerating critical-size cranial defects.

Eltrombopag for enhancement of platelet engraftment in patients undergoing allogeneic cord blood transplantation

Platelet recovery after allogeneic umbilical cord blood (UCB) transplantation is delayed compared to other graft sources. We conducted a multicenter phase 2a study to explore whether eltrombopag, a thrombopoietin-receptor agonist, would enhance platelet recovery after UCB transplantation. Between 02/2013 and 07/2016, 12 (10 adults, 2 children) individuals (median age 50; range 6-74 years) with hematological malignancies in complete remission were enrolled. Eltrombopag was given for a median of 76 (range 15-175) days and was safe even at doses of 300 mg/day. Median time to neutrophil engraftment was 23 (range 16-40) days. Median time to platelets >20,000/µl and >50,000/µl was 55 (range 25-199) and 66 (range 31-230) days, respectively. A historical cohort comparison did not reveal an advantage for eltrombopag. In conclusion, in the present study eltrombopag seems safe. Based on our limited data, it seems unlikely that eltrombopag could enhance platelet engraftment after UCB transplantation.

Idiopathic thrombocytopenic purpura (ITP) - new era for an old disease

Immune thrombocytopenia is an autoimmune hematological disorder characterized by severely decreased platelet count of peripheral cause: platelet destruction via antiplatelet antibodies which may also affect marrow megakaryocytes. Patients may present in critical situations, with cutaneous and/or mucous bleeding and possibly life-threatening organ hemorrhages (cerebral, digestive, etc.) Therefore, rapid diagnosis and therapeutic intervention are mandatory. Corticotherapy represents the first treatment option, but as in any autoimmune disorder, there is a high risk of relapse. Second line therapy options include: intravenous immunoglobulins, thrombopoietin receptor agonists, rituximab or immunosuppression, but their benefit is usually temporary. Moreover, the disease generally affects young people who need repeated and prolonged treatment and hospitalization and therefore, it is preferred to choose a long term effect therapy. Splenectomy - removal of the site of platelet destruction - represents an effective and stable treatment, with 70-80% response rate and low complications incidence. A challenging situation is the association of ITP with pregnancy, which further increases the risk due to the immunodeficiency of pregnancy, major dangers of bleeding, vital risks for mother and fetus, potential risks of medication, necessity of prompt intervention in the setting of specific obstetrical situations - delivery, pregnancy loss, obstetrical complications, etc. We present an updated review of the current clinical and laboratory data, as well as a detailed analysis of the available therapeutic options with their benefits and risks, and also particular associations (pregnancy, relapsed and refractory disease, emergency treatment).

RhTyrRS (Y341A), a novel human tyrosyl-tRNA synthetase mutant, stimulates thrombopoiesis through activation of the VEGF-R II/NF-κB pathway

BACGROUND AND PURPOSE

Tumor chemotherapy and radiotherapy induces hematopoietic cell damage, resulting in thrombocytopenia. Conventional platelet transfusion strategies or drug therapies are used to treat thrombocytopenia. However, these therapies may result in a several side effects, including heightened susceptibility to infectious diseases and the formation of anti-TPO-antibodies. Therefore, a more secure strategy should be explored to overcome and compensate for the shortcomings of conventional strategies.

EXPERIMENTAL APPROACH

Effects of rhTyrRS(Y341A) on the expression of VCAM-1 on the surface of HUVECs were determined by analysing mRNA expression, promoter activity, protein expression. The molecular mechanisms of the effects of rhTyrRS(Y341A) on the expression of VCAM-1 on the surface of HUVECs were investigated by determining the activation of VEGF-R II/NF-κB pathway.

KEY RESULTS

Our results provide evidence that rhTyrRS (Y341A) activates NF-κB to upregulate VCAM-1 in a VEGF-R II/NF-κB pathway-dependent, resulting in megakaryocyte adhering to PVECs to induce platelet production.

CONCLUSIONS

This study suggested that rhTyrRS (Y341A), a novel human tyrosyl-tRNA synthetase mutation, increased the platelet count under normal conditions. Further more, we confirmed that an NF-κB-mediated mechanism is involved in rhTyrRS (Y341A)-induced thrombopoiesis, which involves its interaction with VEGF-R II.

New Small Molecule Drugs for Thrombocytopenia: Chemical, Pharmacological, and Therapeutic Use Considerations

This review provides details about three small molecules that were recently approved by the FDA for the treatment of thrombocytopenia. The new treatments include lusutrombopag, avatrombopag, and fostamatinib. The first two drugs are orally active thrombopoietin receptor (TPO-R) agonists which are FDA-approved for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure. Fostamatinib is orally active prodrug that, after activation, becomes spleen tyrosine kinase (SYK) inhibitor. Fostamatinib is currently used to treat chronic and refractory immune thrombocytopenia in patients who have had insufficient response to previous treatment. Chemical structures, available dosage forms, recommended dosing, pharmacokinetics, results of toxicity studies in animals, most frequent adverse effects, significant outcomes of the corresponding clinical trials, and their use in specific patient populations are thoroughly described. Described also is a comparative summary of the different aspects of five currently available therapies targeting TPO-R or SYK for the treatment of thrombocytopenia.

Cytokine control of megakaryopoiesis

Platelets are anuclear blood cells required for haemostasis and are implicated in other processes including inflammation and metastasis. Platelets are produced by megakaryocytes, specialized cells that are themselves generated by a process of controlled differentiation and maturation of bone-marrow stem and progenitor cells. This process of megakaryopoiesis involves the coordinated interplay of transcription factor-controlled cellular programming with extra-cellular cues produced locally in supporting niches or as circulating factors. This review focuses on these external cues, the cytokines and chemokines, that drive production of megakaryocytes and support the terminal process of platelet release. Emphasis is given to thrombopoietin (Tpo), the major cytokine regulator of steady-state megakaryopoiesis, and its specific cell surface receptor, the Mpl protein, including normal and pathological roles as well as clinical application. The potential for alternative or supplementary regulatory mechanisms for platelet production, particularly in times of acute need, or in states of infection or inflammation are also discussed.

Thrombopoietin mimetics for patients with myelodysplastic syndromes

BACKGROUND

Myelodysplastic syndrome (MDS) is one of the most frequent haematologic malignancies of the elderly population and characterised by progenitor cell dysplasia with ineffective haematopoiesis and a high rate of transformation to acute myeloid leukaemia (AML). Thrombocytopenia represents a common problem for patients with MDS. ranging from mild to serious bleeding events and death. To manage thrombocytopenia, the current standard treatment includes platelet transfusion, unfortunately leading to a range of side effects. Thrombopoietin (TPO) mimetics represent an alternative treatment option for MDS patients with thrombocytopenia. However, it remains unclear, whether TPO mimetics influence the increase of blast cells and therefore to premature progression to AML.

OBJECTIVES

To evaluate the efficacy and safety of thrombopoietin (TPO) mimetics for patients with MDS.

SEARCH METHODS

We searched for randomised controlled trials in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (January 2000 to August 2017), trials registries (ISRCTN, EU clinical trials register and clinicaltrials.gov) and conference proceedings. We did not apply any language restrictions. Two review authors independently screened search results, disagreements were solved by discussion.

SELECTION CRITERIA

We included randomised controlled trials comparing TPO mimetics with placebo, no further treatment or another TPO mimetic in patients with MDS of all risk groups, without gender, age or ethnicity restrictions. Additional chemotherapeutic treatment had to be equal in both arms.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of trials, disagreements were resolved by discussion. Risk ratio (RR) was used to analyse mortality during study, transformation to AML, incidence of bleeding events, transfusion requirement, all adverse events, adverse events >= grade 3, serious adverse events and platelet response. Overall survival (OS) and progression-free survival (PFS) have been extracted as hazard ratios, but could not be pooled as results were reported in heterogenous ways. Health-related quality of life and duration of thrombocytopenia would have been analysed as standardised mean differences, but no trial reported these outcomes.

MAIN RESULTS

We did not identify any trial comparing one TPO mimetic versus another. We analysed six eligible trials involving 746 adult patients. All trials were reported as randomised and double-blind trials including male and female patients. Two trials compared TPO mimetics (romiplostim or eltrombopag) with placebo, one trial evaluated eltrombopag in addition to the hypomethylating agent azacitidine, two trials analysed romiplostim additionally to a hypomethylating agent (azacitidine or decitabine) and one trial evaluated romiplostim in addition to the immunomodulatory drug lenalidomide. There are more data on romiplostim (four included, completed, full-text trials) than on eltrombopag (two trials included: one full-text publication, one abstract publication). Due to small sample sizes and imbalances in baseline characteristics in three trials and premature termination of two studies, we judged the potential risk of bias of all included trials as high.Due to heterogenous reporting, we were not able to pool data for OS. Instead of that, we analysed mortality during study. There is little or no evidence for a difference in mortality during study for thrombopoietin mimetics compared to placebo (RR 0.97, 95% confidence interval (CI) 0.73 to 1.27, N = 6 trials, 746 patients, low-quality evidence). It is unclear whether the use of TPO mimetics induces an acceleration of transformation to AML (RR 1.02, 95% CI 0.59 to 1.77, N = 5 trials, 372 patients, very low-quality evidence).Thrombopoietin mimetics probably improve the incidence of all bleeding events (RR 0.92, 95% CI 0.86 to 0.99, N = 5 trials, 390 patients, moderate-quality evidence). This means that in the study population, 713 out of 1000 in the placebo arm will have a bleeding event, compared to 656 of 1000 (95% CI 613 to 699) in the TPO mimetics arm. There is little or no evidence for a difference that TPO mimetics significantly diminish the rate of transfusion requirement (RR 0.83, 95% CI 0.66 to 1.05, N = 4 trials, 358 patients, low-quality evidence). No studies were found that looked at quality of life or duration of thrombocytopenia.There is no evidence that patients given TPO mimetics suffer more all adverse events (RR 1.01, 95% CI 0.96 to 1.07, N = 5 trials, 390 patients, moderate-quality evidence). There is uncertainty whether the number of serious adverse events decrease under therapy with TPO mimetics (RR 0.89, 95% CI 0.54 to 1.46, N = 4 trials, 356 patients, very low-quality evidence).We identified one ongoing study and one study marked as completed (March 2015), but without publication of results for MDS patients (only results reported for AML and MDS patients together). Both studies evaluate MDS patients receiving eltrombopag in comparison to placebo.

AUTHORS' CONCLUSIONS

No trial evaluated one TPO mimetic versus another.Six trials including adult patients analysed one TPO mimetic versus placebo, sometimes combined with standard therapy in both arms. Given the uncertainty of the quality of evidence, meta-analyses show that there is little or no evidence for a difference in mortality during study and premature progress to AML. However, these assumptions have to be further explored. Treatment with TPO mimetics resulted in a lower number of MDS patients suffering from bleeding events.There is no evidence for a difference between study groups regarding transfusion requirement. Enlarged sample sizes and a longer follow-up of future trials should improve the estimate of safety and efficacy of TPO mimetics, moreover health-related quality of life should be evaluated. As two ongoing studies currently investigate eltrombopag (one already completed, but without published results), we are awaiting results for this drug.

Pathogenesis and Therapeutic Mechanisms in Immune Thrombocytopenia (ITP)

Immune thrombocytopenia (ITP) is a complex autoimmune disease characterized by low platelet counts. The pathogenesis of ITP remains unclear although both antibody-mediated and/or T cell-mediated platelet destruction are key processes. In addition, impairment of T cells, cytokine imbalances, and the contribution of the bone marrow niche have now been recognized to be important. Treatment strategies are aimed at the restoration of platelet counts compatible with adequate hemostasis rather than achieving physiological platelet counts. The first line treatments focus on the inhibition of autoantibody production and platelet degradation, whereas second-line treatments include immunosuppressive drugs, such as Rituximab, and splenectomy. Finally, third-line treatments aim to stimulate platelet production by megakaryocytes. This review discusses the pathophysiology of ITP and how the different treatment modalities affect the pathogenic mechanisms.

Expression, purification and biological activity assessment of romiplostim biosimilar peptibody

Background

Romiplostim is a peptibody analogue of thrombopoietin (TPO) which regulates platelet production. This molecule consists of two main parts: Peptide sequences which like wild type TPO, mimics stimulation of TPO receptor and IgG1Fc, (Peptide + Antibody = Peptibody). This drug is used in treatment of chronic Immune Thrombocytopenic Purpura (ITP).

Methods

In this project E. coli bacteria were transformed by a construct harboring peptibody fusion gene. This construct consisted of two repeated peptide sequences which have fused to Carboxyl group of IgG1Fc. Designed construct in E. coli host resulted in protein expression in cytoplasm as inclusion body. The inclusion bodies were separated, washed and after denaturation and solubilization, in the last stage the desired peptibodies were refolded and purified. The resulting peptibodies were characterized by SDS-PAGE and Western immunoblotting. The bioactivity were assessed in vivo using subcutaneous injection in mice.

Results

Results showed accurate molecules were produced and purified. Also, in vivo experiment showed significant increment (more than two fold) of platelets compared to control group.

Conclusion

In this study laboratory scale production of recombinant romiplostim showed proper in-vivo bioactivity. This new approach in expression and purification of this recently introduced thrombopoietin receptor agonist drug may be followed by scale up of its production to response the chronic ITP patient’s demand.

When and how to treat childhood immune thrombocytopenia

Childhood immune thrombocytopenia is an autoimmune process resulting in an isolated thrombocytopenia that puts the child at risk for bleeding and can negatively impact quality of life. Pharmacologic intervention aims to stabilize the platelet count, with the goal of achieving hemostasis and maximizing health-related quality of life.

Risk of thromboembolism with thrombopoietin receptor agonists in adult patients with thrombocytopenia: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

Romiplostim and eltrombopag are thrombopoietin receptor (TPOr) agonists that promote megakaryocyte differentiation, proliferation and platelet production. In 2012, a systematic review and meta-analysis reported a non-statistically significant increased risk of thromboembolic events for these drugs, but analyses were limited by lack of statistical power. Our objective was to update the 2012 meta-analysis examining whether TPOr agonists affect thromboembolism occurrence in adult thrombocytopenic patients.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs). Updated searches were conduced on PubMed, Cochrane Central, and publicly available registries (up to December 2014). RCTs using romiplostim or eltrombopag in at least one group were included. Relative risks (RR), absolute risk ratios (ARR) and number needed to harm (NNH) were estimated. Heterogeneity was analyzed using Cochran's Q test and I(2) statistic.

RESULTS

Fifteen studies with 3026 adult thrombocytopenic patients were included. Estimated frequency of thromboembolism was 3.69% (95% CI: 2.95-4.61%) for TPOr agonists and 1.46% (95% CI: 0.89-2.40%) for controls. TPOr agonists were associated with a RR of thromboembolism of 1.81 (95% CI: 1.04-3.14) and an ARR of 2.10% (95% CI: 0.03-3.90%) meaning a NNH of 48. Overall, we did not find evidence of statistical heterogeneity (p=0.43; I(2)=1.60%).

CONCLUSIONS

Our updated meta-analysis suggested that TPOr agonists are associated with a higher risk of thromboemboembolic events compared with controls, and supports the current recommendations included in the European product information on this respect.

Adipose-Derived Mesenchymal Stem Cells (ADSCs) With the Potential to Ameliorate Platelet Recovery, Enhance Megakaryopoiesis, and Inhibit Apoptosis of Bone Marrow Cells in a Mouse Model of Radiation-Induced Thrombocytopenia

Substantial damage to the bone marrow can be caused by exposure to radiation, which can then develop into severe thrombocytopenia. In this study, we investigated the in vivo impact of adipose-derived mesenchymal stem cells (ADSCs) on megakaryopoiesis and platelet recovery in irradiated mice. Radiation markedly reduced peripheral blood counts. Recovery of both platelets and WBCs was better in the ADSC-treated group compared with the saline group and the fibroblast group 21 days after irradiation. A significant increase in the total CFU and MK-CFU after irradiation was observed in the ADSC group compared with the saline group and the fibroblast group. Further, the proportion of CD41(+) cells in the ADSC group was significantly higher than that in the saline group and the fibroblast group. ADSC treatment significantly improved the cellularity and decreased the apoptotic cells in the bone marrow while normal fibroblasts did not. Administration of ADSCs upregulated protein expression of phosphorylated Akt and Bcl-xL, whereas the expression of Bax, a protein related to apoptosis, was significantly lower in the ADSC group. In conclusion, this study suggests that ADSCs were capable of promoting platelet recovery, improving megakaryopoiesis, and inhibiting apoptosis of bone marrow cells in irradiated mice. The antiapoptotic effect of ADSCs is likely to be mediated via the PI3K/Akt pathway. These findings may provide a scientific basis for using ADSCs as a new therapy after irradiation.

[Clinical analysis of recombinant human thrombopoietin for 92 adults with severe primary immune thrombocytopenia]

OBJECTIVE

To evaluate the efficacy of recombinant human thrombopoietin (rhTPO) and related factors which influencing the therapeutic effect in adults with severe immune thrombocytopenia (ITP).

METHODS

The efficacy of rhTPO in 92 hospitalized adult patients [35 males and 57 females, median age as 34 (18-65) years] with severe ITP, including 7 cases of newly diagnosed ITP, 29 cases of persistent ITP and 56 cases of chronic ITP from May 2012 to May 2014 was retrospectively investigated. All patients received subcutaneous rhTPO, the injected dosage was 300 U·kg⁻¹·d⁻¹ for 14 days, platelet counts were recorded and followed-up for a week.

RESULTS

The overall response rate of rhTPO treatment was 60.9%. The overall response rates in newly diagnosed, persistent and chronic ITP were 71.4%, 62.1% and 58.9% respectively. The median platelet counts on fourth，seventh, fourteenth days of treatment, and the seventh day of withdrawal were 27(5-49), 65(16-138), 133(28-208) and 67(15-134)×10⁹/L, respectively. The median time was 6(5-7) days when platelet counts reached 100×10⁹/L, the median peak time was 11(5-17) days, the median maximum peak of platelet counts was 194(132-274)×10⁹/L in patients who reached CR after treatment. Related factors which affected therapeutic effect were analyzed in patients who reached CR after treatment, and indicated that sex, age, disease stage, express of platelet membrane glycoprotein (GP) and relative number of CD19+ B, CD3+CD4+ T, CD3+CD8+ T lymphocyte in blood samples did not influence the probability of complete response (P>0.05). A few patients with fever, muscle aches, fatigue or dizziness could be self-recovery without special intervention.

CONCLUSION

Severe ITP in adults treated by rhTPO had satisfactory therapeutic effect and safety.

Developing a co-culture system for effective megakaryo/thrombopoiesis from umbilical cord blood hematopoietic stem/progenitor cells

BACKGROUND AIMS

Platelet transfusion can be a life-saving procedure in different medical settings. Thus, there is an increasing demand for platelets, of which shelf-life is only 5 days. The efficient ex vivo biomanufacturing of platelets would allow overcoming the shortages of donated platelets.

METHODS

We exploited a two-stage culture protocol aiming to study the effect of different parameters on the megakaryo/thrombopoiesis ex vivo. In the expansion stage, human umbilical cord blood (UCB)-derived CD34(+)-enriched cells were expanded in co-culture with human bone marrow mesenchymal stromal cells (BM-MSCs). The megakaryocytic commitment and platelet generation were studied, considering the impact of exogenous addition of thrombopoietin (TPO) in the expansion stage and a cytokine cocktail (Cyt) including TPO and interleukin-3 in the differentiation stage, with the use of different culture medium formulations, and in the presence/absence of BM-MSCs (direct versus non-direct cell-cell contact).

RESULTS

Our results suggest that an early megakaryocytic commitment, driven by TPO addition during the expansion stage, further enhanced megakaryopoiesis. Importantly, the results suggest that co-culture with BM-MSCs under serum-free conditions combined with Cyt addition, in the differentiation stage, significantly improved the efficiency yield of megakaryo/thrombopoiesis as well as increasing %CD41, %CD42b and polyploid content; in particular, direct contact of expanded cells with BM-MSCs, in the differentiation stage, enhanced the efficiency yield of megakaryo/thrombopoiesis, despite inhibiting their maturation.

CONCLUSIONS

The present study established an in vitro model for the hematopoietic niche that combines different biological factors, namely, the presence of stromal/accessory cells and biochemical cues, which mimics the BM niche and enhances an efficient megakaryo/thrombopoiesis process ex vivo.

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.

The effect of erythropoiesis-stimulating agents in patients with therapy-refractory autoimmune hemolytic anemia

BACKGROUND

Many patients with autoimmune hemolytic anemia (AIHA) do not respond to standard therapy and/or may develop severe complications which can be of fatal outcome. There is some evidence that erythropoiesis-stimulating agents (ESAs) may be helpful in the management of such patients.

METHODS

We describe the effect of ESAs in 12 new patients with therapy-refractory AIHA (7 of warm type and 5 of cold type) and review 5 previously reported cases. Serological testing was performed using standard methods.

RESULTS

All patients responded well to treatment with ESAs. At least 5 of the 17 patients demonstrated complete recovery, and none of the patients developed significant adverse reactions due to treatment with ESAs.

CONCLUSION

The mechanism by which ESAs improves hemolysis in AIHA is not completely clear. In addition to increased production and prolonged RBC survival, it may inhibit eryptosis (programmed cell death). ESAs represent a new option in the treatment of decompensated and/or refractory AIHA of warm and cold type. However, more information is required to assess which patients can be treated with ESAs.

Thrombopoietin receptor agonists in primary immune thrombocytopenia

Thrombopoietin (TPO) regulates thrombopoiesis through activation of TPO receptors on the megakaryocyte cell surface, resulting in increased platelet production. The TPO receptor agonists are novel treatments for patients with chronic ITP aimed at increasing platelet production through interactions with the TPO receptor on megakaryocytes. Two TPO receptor agonists, romiplostim and eltrombopag, have received regulatory approval. In patients with chronic ITP who remain at risk of bleeding following treatment with first-line therapies, these agents have been shown to increase platelet counts, decrease bleeding events, and reduce the need for adjunctive or rescue treatments. The TPO receptor agonists are well-tolerated, though uncertainty remains regarding the risk of thromboembolism and bone marrow fibrosis. Comparative clinical trial data addressing the efficacy, safety, cost-effectiveness, and impact on health-related quality of life of TPO receptor agonists relative to other second-line treatment options are needed to guide treatment decisions in chronic ITP patients who fail first-line therapies.

Novel treatments for immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is caused by platelet autoantibodies and T-cell dysregulation. Both platelets and their precursor megakaryocytes may be targeted leading to platelet destruction and underproduction. Current treatments for ITP are inadequate since they do not reverse the disease process and generally do not result in durable remissions. In addition, many treatments are limited by side effects including infection and potentially thrombosis. Novel agents that are currently in development target certain key steps in the disease process, including: (1) the interaction between T-cell and antigen presenting cells (CD40-CD154 interaction); (2) the binding of the Fc portion of platelet autoantibodies to Fc-receptors on macrophages (soluble Fc-RIIb); and (3) the signaling pathways leading to platelet phagocytosis by macrophages (Syk inhibition). Other strategies have been to augment platelet production by simulating thrombopoiesis or by neutralizing physiological inhibitors of megakaryopoiesis. Targeted therapies in ITP have the potential to improve disease morbidity and mortality while limiting systemic side effects. Before these agents can be used in practice, additional clinical studies are needed with rational study outcomes including platelet count, bleeding and quality of life. An individualized treatment strategy is needed for patients since ITP is a distinctly heterogeneous disease.

Immune thrombocytopenia

Immune thrombocytopenia (ITP) is a common hematologic disorder characterized by isolated thrombocytopenia. ITP presents as a primary or a secondary form. ITP may affect individuals of all ages, with peaks during childhood and in the elderly, in whom the age-specific incidence of ITP is greatest. Bleeding is the most common clinical manifestation of ITP. The pathogenesis of ITP is complex, involving alterations in humoral and cellular immunity. Corticosteroids remain the most common first line therapy for ITP. This article summarizes the classification and diagnosis of primary and secondary ITP, as well as the pathogenesis and options for treatment.

Clinical indications for thrombopoietin and thrombopoietin-receptor agonists

Thrombocytopenia is a common hematologic disorder. Stimulation of thrombopoiesis may reduce the risk for thrombocytopenia-induced bleeding, prevent severe thrombocytopenia, and reduce the need for platelet transfusion. The key cytokine is thrombopoietin (TPO). It regulates proliferation and maturation of megakaryocytes as well as platelet production. TPO is synthesized in the liver. Development of TPO from the laboratory into a therapeutic tool has turned out to be an unexpected challenge. Clinical trials on first-generation thrombopoietic growth factors were stopped in 2001. At present, second-generation thrombopoiesis-stimulating agents have only been approved as orphan drugs for third-line therapy of patients with chronic immune thrombocytopenia. Larger groups in need are patients with myelodysplastic syndrome, chemotherapy-induced thrombocytopenia, other forms of hereditary and acquired bone marrow failure, hepatitis C infections, or liver cirrhosis.

Use of Peptide Thrombopoietin Receptor Agonist Romiplostim (Nplate) in a Case of Primary HIV-Associated Thrombocytopenia

Thrombocytopenia is frequently encountered in HIV-infected patients, and the predominant cause is primary HIV-associated thrombocytopenia (PHAT). Standard treatment regimens include optimization of antiretroviral therapy, intravenous immunoglobulin, anti-D, and corticosteroids. Retreatment due to the inability to sustain remission or inferior responses is common, and investigation into the safety and efficacy of alternative therapies is warranted. We describe novel and effective treatment of PHAT with the peptide thrombopoietin receptor agonist romiplostim in a patient with a minimal response to conventional therapy.

Novel anti-c-Mpl monoclonal antibodies identified multiple differentially glycosylated human c-Mpl proteins in megakaryocytic cells but not in human solid tumors

Thrombopoietin and its cognate receptor, c-Mpl, are the primary molecular regulators of megakaryocytopoiesis and platelet production. To date the pattern of c-Mpl expression in human solid tumors and the distribution and biochemical properties of c-Mpl proteins in hematopoietic tissues are largely unknown. We have recently developed highly specific mouse monoclonal antibodies (MAb) against human c-Mpl. In this study we used these antibodies to demonstrate the presence of full-length and truncated human c-Mpl proteins in various megakaryocytic cell types, and their absence in over 100 solid tumor cell lines and in the 12 most common primary human tumor types. Quantitative assays showed a cell context-dependent distribution of full-length and truncated c-Mpl proteins. All forms of human c-Mpl protein were found to be modified with extensive N-linked glycosylation but different degrees of sialylation and O-linked glycosylation. Of note, different variants of full-length c-Mpl protein exhibiting differential glycosylation were expressed in erythromegakaryocytic leukemic cell lines and in platelets from healthy human donors. This work provides a comprehensive analysis of human c-Mpl mRNA and protein expression on normal and malignant hematopoietic and non-hematopoietic cells and demonstrates the multiple applications of several novel anti-c-Mpl antibodies.

Advances in megakaryocytopoiesis and thrombopoiesis: from bench to bedside

Megakaryocytopoiesis involves the commitment of haematopoietic stem cells, proliferation and terminal differentiation of megakaryocytic progenitors (MK-p) and maturation of megakaryocytes (MKs) to produce functional platelets. This complex process occurs in specialized niches in the bone marrow where MKs align adjacent to vascular endothelial cells, form proplatelet projections and release platelets into the circulation. Thrombopoietin (THPO, TPO) is the primary growth factor for the MK lineage and necessary at all stages of development. THPO is constitutively produced in the liver, and binds to MPL (c-Mpl) receptor on platelets and MKs. This activates a cascade of signalling molecules, which induce transcription factors to drive MK development and thrombopoiesis. Decreased turnover rate and platelet number result in increased levels of free THPO, which induces a concentration-dependent compensatory response of marrow-MKs to enhance platelet production. Newly developed thrombopoietic agents operating via MPL receptor facilitate platelet production in thrombocytopenic states, primarily immune thrombocytopenia. Other drugs are available for attenuating malignant thrombocytosis. Herein, we review the regulation of megakaryocytopoiesis and platelet production in normal and disease states, and the innovative drugs and therapeutic modalities to stimulate or decrease thrombopoiesis.

Kidney-limited thrombotic microangiopathy in patients with SLE treated with romiplostim

We present the case of a 19 year-old Caucasian female with history of systemic lupus erythematosus (SLE) and normal baseline kidney function who developed severe acute renal failure following treatment of thrombocytopenia with the thrombopoietic agent romiplostim. Percutaneous kidney biopsy revealed thrombotic microangiopathy (TMA) without immune complex lupus glomerulonephritis. We discuss pathogenesis and differential diagnosis of TMA in patients with SLE and raise concerns regarding the use of thrombopoietic agents in such patients. Based on favorable long-term outcome in our case aggressive treatment and in particular prolonged use of plasma exchange in these patients are advocated.

Revisiting use of growth factors in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematologic neoplasms characterized by morphologic dysplasia, aberrant hematopoiesis and peripheral blood refractory cytopenias. MDS is recognized to be associated with an increased risk of symptomatic anemia, infectious complications and bleeding diathesis, as well as a risk of progression to acute myeloid leukemia, particularly in patients with a high IPSS score. The advent of use of hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) and recombinant erythropoietin (EPO) has improved symptoms in MDS patients in addition to some data that suggest there might be an improvement in survival. G-CSF is an effective therapeutic option in MDS patients, and it should be considered for the management of refractory symptomatic cytopenias. G-CSF and EPO in combination can improve outcomes in appropriate MDS patients such as those with lower-risk MDS and refractory anemia with ring sideroblasts (RARS) . This article reviews use of growth factors for lower-risk MDS patients, and examines the data for G-CSF, EPO and thrombopietic growth factors (TPO) that are available or being developed as therapeutic modalities for this challenging disease.

Simultaneous romiplostin, eltrombopag, and prednisone were successful in severe thrombocytopenia of Evans syndrome refractory to hydrocortisone, splenectomy, intravenous IgG, and rituximab

A 58-year-old woman presented with rheumatoid arthritis-associated Evans syndrome (simultaneous autoimmune hemolytic anemia and autoimmune thrombocytopenic purpura); she was treated unsuccessfully with steroids, romiplostin, rituximab, immunoglobulin G, and splenectomy. The platelet count responded to the combined use of prednisone, eltrombopag, and romiplostin. It may be more reasonable to use combined treatments than sequential monotherapies.

Management of children and adolescents with primary immune thrombocytopenia: controversies and solutions

The management including diagnostic procedures, prophylaxis, treatment and follow-up of patients with primary immune thrombocytopenia (ITP) in childhood is controversial due to limited clinical data, difficulties in the estimation of individual bleeding risk and heterogeneity of pathophysiology potentially causing various treatment responses. Advances in the management of children include increased international collaborations, improved quality of diagnosis and treatment, increased clinical data, refinement of consensus statements where clinical evidence is absent, new drugs and last but not least establishment of watch-and-wait strategies. The Intercontinental Cooperative ITP Study Group promotes international collaboration since more than 10 years based on a worldwide network and experience in registries. Future considerations include concentration of available resources, strengthening international collaboration, focusing on most important scientific and clinical questions, such as identification of the subgroup of patients that benefits most from prophylactic platelet-enhancing treatments and investigation of treatment endpoints other than concepts solely based on the platelet count, including bleeding symptoms, health-related quality of life and economical aspects of treatments.

Influence of Intravenous Immunoglobulin Treatment on Thrombopoiesis

AIM: The mechanisms by which intravenous immunoglobulins (IVIg) result in an increase in platelet counts in most patients with autoimmune thrombocytopenia (ITP) have not yet been fully explained. One of these mechanisms may be related to stimulation of thrombopoiesis. METHODS: A total of 13 adult patients who received IVIg were studied: 11 patients with primary ITP, 1 patient with ITP related to common variable immunodeficiency (CVID), and 1 patient with uncharacterized thrombocytopenia. IVIg (0.5-1.5 g/kg body weight) was administered on consecutive days (days 1-3). Endogenous thrombopoietin (eTPO) was measured prior to and at least 1 day following treatment. In addition, IL-6 was measured in 5 of the treated patients. RESULTS: In 10 of 13 patients, IVIg treatment resulted in an increase in platelet counts. eTPO remained unchanged or elevated in almost all cases where the platelet count remained low (<100 × 10(3)/μ0. In all cases with normal or increased platelet counts (>100 × 10(3)/μ0, the eTPO concentration decreased. Furthermore, IVIg induced IL-6 synthesis in all 5 examined patients. CONCLUSION: Our data indicate that the induction of eTPO synthesis by IL-6 may be a potential mechanism in which IVIg may stimulate thrombopoiesis. Further studies are required to characterize this mechanism.

Rapid update on childhood immune thrombocytopenic purpure

Most childhood immune thrombocytopenic purpure is benign, self-limiting and requires no therapy. However, questions remain: (i) to treat or not; (ii) bone marrow examination or not; and (iii) admit to hospital or not. These questions have dominated the literature and we still need a prospective large multi-centre study of these issues to determine a useful bleeding score, quality of life measure and a measure of parental anxiety.

Romiplostim administration shows reduced megakaryocyte response-capacity and increased myelofibrosis in a mouse model of MYH9-RD

Macrothrombocytopenia in MYH9-related disease (MYH9-RD) results from defects in nonmuscular myosin-IIA function. Thrombopoietin receptor agonists (eltrombopag; romiplostim) seem to improve hemostasis, but little is known about their biologic effects in MYH9-RD. We administered romiplostim to Myh9−/− mice (100 μg/kg, every 3 days, during 1 month). MKs increased to similar numbers in Myh9−/− and wild-type (WT) mice (with an increase in immature MKs), but Myh9−/− platelet count response was much less (2.5-fold vs 8-fold increase). A strong increase in MK nuclei emboli in the lung, in WT and Myh9−/− mice, indicates increased transmigration of MKs from the BM. Prolonged (but not acute) treatment with romiplostim decreased expression of GPIb-IX-V complex and GPVI, but not of GPIIbIIIa, and bleeding time increased in WT mice. Microcirculation was not altered by the increased number of large platelets in any of the assessed organs, but in Myh9−/− mice a much stronger increase in BM reticulin fibers was present after 4 weeks of romiplostim treatment vs WT mice. These data further encourage short-term use of thrombopoietic agents in patients with MYH9-RDs; however, myelofibrosis has to be considered as a potential severe adverse effect during longer treatment. Reduction of GPIbIX/GPVI expression by romiplostim requires further studies.

The burden of immune thrombocytopenia in adults: evaluation of the thrombopoietin receptor agonist romiplostim

BACKGROUND

Immune thrombocytopenia (ITP) is a chronic, immune-mediated disease characterized by a transient or long-lasting decrease in platelet counts. ITP is associated with numerous serious clinical consequences. Discussed here are clinical aspects of ITP, the humanistic and economic burden of ITP, and current treatment options with a focus on romiplostim, a thrombopoietin (TPO) receptor agonist. The aim of this review is to provide decision-makers with the background information necessary to evaluate the value of romiplostim.

SCOPE

PubMed was searched for relevant, English-language papers published from January 2006 through November 2011 relating to the epidemiology and treatment options of chronic ITP, and, focusing on the TPO mimetic romiplostim, patient-reported outcomes (PRO) and economic burden. Recent select conference abstracts were also reviewed.

FINDINGS

The initial clinical management of ITP (e.g., corticosteroids, immunoglobulins) is often associated with adverse events and recommended for short-term use only. Splenectomy, a potentially curative second-line treatment, is associated with increased risks of bleeding and infection, and patients often require additional long-term drug intervention. ITP and its sequelae are associated with a substantial burden on patients' health-related quality-of-life (HRQoL) and increased medical costs. Use of TPO receptor agonists in ITP patients may represent a more efficient use of healthcare resources than existing therapies.

CONCLUSION

While this literature review is not a systematic review, e.g., it considers only approved therapies and published literature written in English, it provides a comprehensive overview of the clinical, humanistic, and economic factors that should be considered in treating ITP, particularly with new agents such as romiplostim. Among the limited number of safe and effective therapies currently available for chronic ITP, highly effective and well-tolerated medications such as romiplostim may reduce the healthcare resource utilization associated with ITP while improving patients' HRQoL.

Eltrombopag: an oral thrombopoietin receptor agonist for the treatment of idiopathic thrombocytopenic purpura

BACKGROUND

Idiopathic thrombocytopenic purpura (ITP) is a relatively rare acquired autoimmune disease characterized by either decreased platelet production or increased platelet destruction leading to reduced platelet counts and increased risk of bleeding. Immune modulators have been used in treatment; however, a novel class of thrombopoietin mimetics has recently been developed. Eltrombopag is approved for patients with chronic ITP who have failed initial treatments with traditional immune modulators or splenectomy.

OBJECTIVES

The goals of this review were to summarize the pharmacology, pharmacokinetic properties, efficacy, and tolerability of eltrombopag and review the approved and investigational uses of this drug.

METHODS

A search of Cochrane Central Register of Clinical Trials and clinicaltrials.gov was conducted using the terms eltrombopag or SB-497115-GR. In addition, all reviews and preclinical and clinical studies published in English between January 1980 and January 2011 were identified in PubMed and Cochrane Database of Systemic Reviews using the same terms.

RESULTS

A total of 153 publications and 13 clinical trials were identified; 14 publications were excluded because they were not published in English. A Phase III trial randomized 114 patients with ITP 2:1 to eltrombopag 50 mg or placebo and demonstrated by day 43 a significantly greater proportion of patients responding in the eltrombopag group than in the placebo group (59% vs 16%, odds ratio [OR] = 9.61; 95% CI, 3.31-27.86; P < 0.0001). The mean percentage change of platelets from baseline in the eltrombopag group was double that of the placebo group at day 8 and was sustained several-fold higher throughout the remainder of the treatment period. Another Phase III trial evaluated the efficacy and safety of eltrombopag compared with placebo over 6 months. The odds of responding (defined as a platelet count of 50-400 × 10(9)/L) were 8 times higher in patients receiving eltrombopag than in those in the placebo group (95% CI, 3.59-18.73; P < 0.0001). Bone marrow fibrosis and hepatotoxicity are the most serious adverse effects, and nausea and vomiting are the most common. Eltrombopag is also being evaluated in the treatment of thrombocytopenia secondary to hepatitis C infection, chemotherapy, acute leukemia, and myelodysplasias.

CONCLUSION

Eltrombopag is well tolerated and effective in raising platelet counts in patients with chronic ITP.