Thrombopoietin receptor agonists: ten years later

Effect of Cytokine Gene Polymorphisms on Eltrombopag Reactivity in Japanese Patients with Immune Thrombocytopenia

BACKGROUND

Immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by low platelet counts resulting from antiplatelet autoantibodies. Analysis of polymorphisms in cytokine-encoding genes is important for understanding the pathophysiology of ITP and selecting appropriate treatments. We investigated associations between polymorphisms in cytokine-encoding genes and responses to therapy in Japanese patients with ITP.

METHODS

The participants in this study comprised 153 patients with ITP and 70 healthy controls. We extracted data on sex, age, platelet counts, bleeding symptoms, and therapeutic responses, including those to prednisolone (PSL) and eltrombopag. Genomic DNA was isolated from peripheral blood and polymorphisms in TNF-α, IL-10, TGF-β1, and IFN-γ genes were analyzed using the PCR-SSP method.

RESULTS

Our results showed that the TGF-β1 +869 C/C genotype might be related to ITP in Japanese patients. The IL-10 -592 C/C and A/A, -819 C/C and T/T, and -1082, -819, -592 ATA/ATA genotypes might be associated with reactivity to PSL. Furthermore, the IL-10 -592 C/A -819 C/T genotypes, IL-10 ACC/ATA genotype, and TGF-β1 +869 T/T and T/C genotypes might be linked to the response to eltrombopag.

CONCLUSION

Our results indicate that analysis of polymorphisms in cytokine-encoding genes could aid in understanding PSL and eltrombopag responsiveness in Japanese patients with ITP.

Miniaturized 3D bone marrow tissue model to assess response to Thrombopoietin-receptor agonists in patients

Thrombocytopenic disorders have been treated with the Thrombopoietin-receptor agonist Eltrombopag. Patients with the same apparent form of thrombocytopenia may respond differently to the treatment. We describe a miniaturized bone marrow tissue model that provides a screening bioreactor for personalized, pre-treatment response prediction to Eltrombopag for individual patients. Using silk fibroin, a 3D bone marrow niche was developed that reproduces platelet biogenesis. Hematopoietic progenitors were isolated from a small amount of peripheral blood of patients with mutations in ANKRD26 and MYH9 genes, who had previously received Eltrombopag. The ex vivo response was strongly correlated with the in vivo platelet response. Induced Pluripotent Stem Cells (iPSCs) from one patient with mutated MYH9 differentiated into functional megakaryocytes that responded to Eltrombopag. Combining patient-derived cells and iPSCs with the 3D bone marrow model technology allows having a reproducible system for studying drug mechanisms and for individualized, pre-treatment selection of effective therapy in Inherited Thrombocytopenias.

Platelets are tiny cell fragments essential for blood to clot. They are created and released into the bloodstream by megakaryocytes, giant cells that live in the bone marrow. In certain genetic diseases, such as Inherited Thrombocytopenia, the bone marrow fails to produce enough platelets: this leaves patients extremely susceptible to bruising, bleeding, and poor clotting after an injury or surgery.

Certain patients with Inherited Thrombocytopenia respond well to treatments designed to boost platelet production, but others do not. Why these differences exist could be investigated by designing new test systems that recreate the form and function of bone marrow in the laboratory. However, it is challenging to build the complex and poorly understood bone marrow environment outside of the body.

Here, Di Buduo et al. have developed an artificial three-dimensional miniature organ bioreactor system that recreates the key features of bone marrow. In this system, megakaryocytes were grown from patient blood samples, and hooked up to a tissue scaffold made of silk. The cells were able to grow as if they were in their normal environment, and they could shed platelets into an artificial bloodstream. After treating megakaryocytes with drugs to stimulate platelet production, Di Buduo et al. found that the number of platelets recovered from the bioreactor could accurately predict which patients would respond to these drugs in the clinic.

This new test system enables researchers to predict how a patient will respond to treatment, and to tailor therapy options to each individual. This technology could also be used to test new drugs for Inherited Thrombocytopenias and other blood-related diseases; if scaled-up, it could also, one day, generate large quantities of lab-grown blood cells for transfusion.

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.

How I treat primary ITP in adult patients who are unresponsive to or dependent on corticosteroid treatment

Approximately 80% of adult patients with immune thrombocytopenia (ITP) have treatment failure with corticosteroids or become dependent on them and require second-line therapy. Several new and effective therapies have been introduced during the past decade and our understanding of disease burden and its effect on quality of life has expanded. It is now recommended that splenectomy, the standard second-line therapy for decades, be delayed for at least 12 to 24 months, allowing for more patients to achieve remission on medical therapies before considering surgery. It is highly recommended that medical therapies be used that have abundant clinical trial evidence, such as the thrombopoietin receptor agonists (TPO-RAs) rituximab and fostamatinib. Unfortunately, there are no reliable biomarkers that help in treatment selection. These therapeutic medical options have variable efficacy, safety profiles, mechanisms of action, and modes of administration. This enables and mandates an individualized approach to treatment, where patient involvement, preferences and values have become central to the process of choosing the appropriate therapy. Both TPO-RAs and fostamatinib are maintenance therapies, whereas rituximab is given for a limited number of doses. Although the response is usually maintained while receiving a TPO-RA or fostamatinib therapy, half of rituximab responders will no longer respond 1 to 2 years after administration and require retreatment or other therapy.

Platelet autoantibody specificity and response to rhTPO treatment in patients with primary immune thrombocytopenia

This retrospective study aimed to evaluate the relationship between plasma autoantibody species and rhTPO response in adult ITP patients who failed the first-line treatments. Plasma anti-glycoprotein (GP) IIb/IIIa and anti-GPIb/IX autoantibodies were detected in 47·2% and 40·6% of the 123 patients, respectively. Overall response rate to rhTPO treatment in patients without anti-GPIb/IX autoantibodies was significantly higher than patients with anti-GPIb/IX autoantibodies (82·2% vs. 60·0%, P = 0·006). By contrast, no statistical difference in response rate was observed between patients with or without anti-GPIIb/IIIa autoantibodies (74·1% vs. 72·3%, P = 0·819). Therefore, the presence of anti-GPIb/IX autoantibodies might serve as a predictive factor for poor response to rhTPO treatment in ITP.

Practical Recommendations for the Management of Patients with ITP During the COVID-19 Pandemic

The current COVID-19 pandemic requires revisiting our current approach to major blood disorders, including ITP (Immune Thrombocytopenia), stirring up the production of several disease-specific practical guidelines. This report describes an updated version of consensus-based practical guidelines on the management of ITP, adapted to the Italian health system and social context. It highlights the role of the hematologist in offering guidance for choosing differentiated approaches in relation to specific circumstances and is intended to provide them with a useful tool for sharing the decision-making process with their patients.

Probably, the greatest risk to avoid for a patient with suspected, ongoing or relapsed ITP - that is not severe enough to place him or her at risk for major bleeding - is to be infected in non-hospital and hospital healthcare settings. This risk must be carefully considered when adapting the diagnostic and therapeutic approach.

More in detail, the document first addresses the appropriate management for COVID-19 negative patients with newly diagnosed ITP or who experience a relapse of previous ITP, according to first and second lines of treatment and then the management of COVID-19 positive patients according to their severity, from paucisymptomatic to those requiring admission to Intensive Cure Units (ICU). The pros and cons of the different treatments required to correct platelet count are discussed, as are some specific situations, including chronic ITP, splenectomy, thromboembolic complication and anti COVID-19 vaccination.

Real-world use of thrombopoietin receptor agonists in elderly patients with primary immune thrombocytopenia

The efficacy and safety of thrombopoietin-receptor agonists (TRAs) in elderly patients with primary immune thrombocytopenia (ITP) is uncertain. In 384 ITP patients treated with TRAs when aged ≥60 years, we investigated TRAs response and switch, thrombotic/hemorrhagic risk, and sustained responses off-treatment (SROT). After 3 months, 82.5% and 74.3% of eltrombopag and romiplostim-treated patients achieved a response, respectively (p=0.09); 66.7% maintained the response (median follow-up: 2.7 years). Eighty-five (22.2%) patients switched to the alternative TRA; while no cross-toxicity was observed, 83.3% of resistant patients had a response after the switch. During TRA, 34 major thromboses (3 fatal) and 14 major hemorrhages (none fatal) occurred in 18 and 10 patients, respectively, and were associated with thrombosis history (SHR: 2.04, p=0.05) and platelet count <20x109/L at TRA start (SHR: 1.69, p=0.04), respectively. A recurrent event occurred in 15.6% of patients surviving thrombosis, in all cases but one during persisting TRA treatment (incidence rate: 7.7 per 100 patient-years). All recurrences occurred in the absence of adequate antithrombotic secondary prophylaxis. Sixty-two (16.5%) responding patients discontinued TRA; 53 (13.8%) patients maintained SROT, which was associated with TRA discontinuation in complete response (p<0.001). Very old age (≥75, 41.1%) was associated with more frequent TRAs start in persistent/acute phase but not with response or thrombotic/hemorrhagic risk. TRAs are effective in elderly ITP patients, with no fatal haemorrhages and with SROT in a significant portion of patients; in patients with thrombosis history caution is warranted and a careful risk/benefit balance should be carried out.

Role of Thrombopoietin Receptor Agonists in Inherited Thrombocytopenia

In the last decade, improvements in genetic testing have revolutionized the molecular diagnosis of inherited thrombocytopenias (ITs), increasing the spectrum of knowledge of these rare, complex and heterogeneous disorders. In contrast, the therapeutic management of ITs has not evolved in the same way. Platelet transfusions have been the gold standard treatment for a long time. Thrombopoietin receptor agonists (TPO-RA) were approved for immune thrombocytopenia (ITP) ten years ago and there is evidence for the use of TPO-RA not only in other forms of ITP, but also in ITs. We have reviewed in the literature the existing evidence on the role of TPO-RAs in ITs from 2010 to February 2021. A total of 24 articles have been included, 4 clinical trials, 3 case series and 17 case reports. A total of 126 patients with ITs have received TPO-RA. The main diagnoses were Wiskott–Aldrich syndrome, MYH9-related disorder and ANKRD26-related thrombocytopenia. Most patients were enrolled in clinical trials and were treated for short periods of time with TPO-RA as bridging therapies towards surgical interventions, or other specific approaches, such as hematopoietic stem cell transplantation. Here, we have carried out an updated and comprehensive review about the efficacy and safety of TPO-RA in ITs.

How I manage cyclic thrombocytopenia

Cyclic thrombocytopenia (CTP) is a rare disease, which is characterized by periodic fluctuation of the platelet count. The pathogenesis of CTP is unknown and most likely heterogeneous. Patients with CTP are almost always misdiagnosed as having primary immune thrombocytopenia (ITP). The interval between ITP and CTP diagnosis can be many years. CTP patients often receive ITP-specific therapies including corticosteroids, thrombopoietin receptor agonists, rituximab, and splenectomy, which are followed by a transient increase in platelet count that is wrongly attributed to treatment effect with inevitable "relapse." CTP can be diagnosed by frequent platelet count monitoring, which reveals a typical pattern of periodic platelet cycling. An early diagnosis of CTP will prevent these patients from being exposed to possibly harmful therapies. The bleeding phenotype is usually mild and consists of mucocutaneous bleeding at the time when the platelet count is at its nadir. Severe bleeding from other sites can occur but is rare. Some patients respond to cyclosporine A or to danazol, but most patients do not respond to any therapy. CTP can be associated with hematological malignancies or disorders of the thyroid gland. Nevertheless, spontaneous remissions can occur, even after many years.

Acquired severe aplastic anaemia: how medical therapy evolved in the 20th and 21st centuries

The progress in aplastic anaemia (AA) management is one of success. Once an obscure entity resulting in death in most affected can now be successfully treated with either haematopoietic stem cell transplantation (HSCT) or immunosuppressive therapy (IST). The mechanisms that underly the diminution of haematopoietic stem cells (HSCs) are now better elucidated, and include genetics and immunological alterations. Advances in supportive care with better antimicrobials, safer blood products and iron chelation have greatly impacted AA outcomes. Working somewhat 'mysteriously', anti-thymocyte globulin (ATG) forms the base for both HSCT and IST protocols. Efforts to augment immunosuppression potency have not, unfortunately, led to better outcomes. Stimulating HSCs, an often-sought approach, has not been effective historically. The thrombopoietin receptor agonists (Tpo-RA) have been effective in stimulating early HSCs in AA despite the high endogenous Tpo levels. Dosing, timing and best combinations with Tpo-RAs are being defined to improve HSCs expansion in AA with minimal added toxicity. The more comprehensive access and advances in HSCT and IST protocols are likely to benefit AA patients worldwide. The focus of this review will be on the medical treatment advances in AA.

Thrombocytopenia and Hemostatic Changes in Acute and Chronic Liver Disease: Pathophysiology, Clinical and Laboratory Features, and Management

Thrombocytopenia, defined as a platelet count <150,000/μL, is the most common complication of advanced liver disease or cirrhosis with an incidence of up to 75%. A decrease in platelet count can be the first presenting sign and tends to be proportionally related to the severity of hepatic failure. The pathophysiology of thrombocytopenia in liver disease is multifactorial, including (i) splenomegaly and subsequently increased splenic sequestration of circulating platelets, (ii) reduced hepatic synthesis of thrombopoietin with missing stimulation both of megakaryocytopoiesis and thrombocytopoiesis, resulting in diminished platelet production and release from the bone marrow, and (iii) increased platelet destruction or consumption. Among these pathologies, the decrease in thrombopoietin synthesis has been identified as a central mechanism. Two newly licensed oral thrombopoietin mimetics/receptor agonists, avatrombopag and lusutrombopag, are now available for targeted treatment of thrombocytopenia in patients with advanced liver disease, who are undergoing invasive procedures. This review summarizes recent advances in the understanding of defective but at low level rebalanced hemostasis in stable cirrhosis, discusses clinical consequences and persistent controversial issues related to the inherent bleeding risk, and is focused on a risk-adapted management of thrombocytopenia in patients with chronic liver disease, including a restrictive transfusion regimen.

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.

Use of thrombopoietin receptor agonists for immune thrombocytopenia in pregnancy: results from a multicenter study

Management of immune thrombocytopenia (ITP) during pregnancy can be challenging because treatment choices are limited. Thrombopoietin receptor agonists (Tpo-RAs), which likely cross the placenta, are not recommended during pregnancy. To better assess the safety and efficacy of off-label use of Tpo-RAs during pregnancy, a multicenter observational and retrospective study was conducted. Results from 15 pregnant women with ITP (pregnancies, n = 17; neonates, n = 18) treated with either eltrombopag (n = 8) or romiplostim (n = 7) during pregnancy, including 2 patients with secondary ITP, were analyzed. Median time of Tpo-RA exposure during pregnancy was 4.4 weeks (range, 1-39 weeks); the indication for starting Tpo-RAs was preparation for delivery in 10 (58%) of 17 pregnancies, whereas 4 had chronic refractory symptomatic ITP and 3 were receiving eltrombopag when pregnancy started. Regarding safety, neither thromboembolic events among mothers nor Tpo-RA-related fetal or neonatal complications were observed, except for 1 case of neonatal thrombocytosis. Response to Tpo-RAs was achieved in 77% of cases, mostly in combination with concomitant ITP therapy (70% of responders). On the basis of these preliminary findings, temporary off-label use of Tpo-RAs for severe and/or refractory ITP during pregnancy seems safe for both mother and neonate and is likely to be helpful, especially before delivery.

Challenges and Advances in Managing Thrombocytopenic Cancer Patients

Cancer patients have varying incidence, depth and duration of thrombocytopenia. The mainstay of managing severe chemotherapy-induced thrombocytopenia (CIT) in cancer is the use of platelet transfusions. While prophylactic platelet transfusions reduce the bleeding rate, multiple unmet needs remain, such as high residual rates of bleeding, and anticancer treatment dose reductions/delays. Accordingly, the following promising results in other settings, antifibrinolytic drugs have been evaluated for prevention and treatment of bleeding in patients with hematological malignancies and solid tumors. In addition, Thrombopoeitin receptor agonists have been studied for two major implications in cancer: treatment of severe thrombocytopenia associated with myelodysplastic syndrome and acute myeloid leukemia; primary and secondary prevention of CIT in solid tumors in order to maintain dose density and intensity of anti-cancer treatment. Furthermore, thrombocytopenic cancer patients are often prescribed antithrombotic medication for indications arising prior or post cancer diagnosis. Balancing the bleeding and thrombotic risks in such patients represents a unique clinical challenge. This review focuses upon non-transfusion-based approaches to managing thrombocytopenia and the associated bleeding risk in cancer, and also addresses the management of antithrombotic therapy in thrombocytopenic cancer patients.

Eltrombopag for the treatment of refractory thrombocytopenia associated with connective tissue disease

To assess the efficacy and safety of eltrombopag in connective tissue disease (CTD)-immune thrombocytopenia (ITP), we conducted this single-center retrospective observational study, including patients with refractory CTD-ITP who were treated with eltrombopag between January 2018 and August 2019. The characteristics of patients at baseline, and the efficacy and safety of the drug were analyzed. The predictors for a response were analyzed using a univariate analysis such as Chi-square or nonparametric test and a multiple correspondence analysis (MCA) method. A total of 15 patients with refractory CTD-ITP were included in the study. Their median age at the time of inclusion was 40.6 years. The median platelet count at initiation of eltrombopag was 11.53 × 10⁹/L. The median remission time was 3.42 weeks. The complete remission (CR) and overall response rate decreased with time. The factors that associated with response to eltrombopag in patients with CTD-ITP were protopathy, WBC counts, levels of hemoglobin, and characteristics of bone marrow findings in univariate analysis. In addition, MCA indicated that a poor response to eltrombopag in patients with refractory CTD-ITP was closely associated with a protopathy with SS, medium to severe degree of anemia, leukopenia, and bone marrow aspiration showing aplastic anemia, an absence of megakaryocytes or macrophage activation syndrome (MAS). In conclusion, eltrombopag was effective and well-tolerated in patients with CTD-associated thrombocytopenia. Some factors should be considered in the use of eltrombopag, including the protopathy, blood test, and bone marrow histology.

A multicenter, randomized phase III trial of hetrombopag: a novel thrombopoietin receptor agonist for the treatment of immune thrombocytopenia

Background

Hetrombopag, a novel thrombopoietin receptor agonist, has been found in phase I studies to increase platelet counts and reduce bleeding risks in adults with immune thrombocytopenia (ITP). This phase III study aimed to evaluate the efficacy and safety of hetrombopag in ITP patients.

Methods

Patients who had not responded to or had relapsed after previous treatment were treated with an initial dosage of once-daily 2.5 or 5 mg hetrombopag (defined as the HETROM-2.5 or HETROM-5 group) or with matching placebo in a randomized, double-blind, 10-week treatment period. Patients who received placebo and completed 10 weeks of treatment switched to receive eltrombopag, and patients treated with hetrombopag in the double-blind period continued hetrombopag during the following open-label 14-week treatment. The primary endpoint was the proportion of responders (defined as those achieving a platelet count of ≥ 50 × 10⁹/L) after 8 weeks of treatment.

Results

The primary endpoint was achieved by significantly more patients in the HETROM-2.5 (58.9%; odds ratio [OR] 25.97, 95% confidence interval [CI] 9.83–68.63; p < 0.0001) and HETROM-5 (64.3%; OR 32.81, 95% CI 12.39–86.87; p < 0.0001) group than in the Placebo group (5.9%). Hetrombopag was also superior to placebo in achieving a platelet response and in reducing the bleeding risk and use of rescue therapy throughout 8 weeks of treatment. The durable platelet response to hetrombopag was maintained throughout 24 weeks. The most common adverse events were upper respiratory tract infection (42.2%), urinary tract infection (17.1%), immune thrombocytopenic purpura (17.1%) and hematuria (15%) with 24-week hetrombopag treatment.

Conclusions

In ITP patients, hetrombopag is efficacious and well tolerated with a manageable safety profile.

Trial registration Clinical trials.gov NCT03222843, registered July 19, 2017, retrospectively registered.

Eltrombopag second-line therapy in adult patients with primary immune thrombocytopenia in an attempt to achieve sustained remission off-treatment: results of a phase II, multicentre, prospective study

Up to 30% immune thrombocytopenia (ITP) patients achieve a sustained remission off-treatment (SROT) after discontinuation of thrombopoietin receptor agonists (TPO-RAs). Factors predictive of response are lacking. Patients aged ≥18 years with newly diagnosed or persistent ITP were treated with eltrombopag for 24 weeks. Primary end-point was SROT: the proportion of responders that were able to taper and discontinue eltrombopag maintaining the response during a period of observation (PO) of six months. Secondary end-points included the association between some immunological parameters (TPO serum levels, cytokines and lymphocyte subsets) and response. Fifty-one patients were evaluable. Primary end-point was achieved in 13/51 (25%) treated patients and 13/34 (38%) patients who started the tapering. Baseline TPO levels were not associated with response at week 24 nor with SROT. Higher baseline levels of IL-10, IL-4, TNF-α and osteopontin were negative factors predictive of response (P = 0·001, 0·008, 0·02 and 0·03 respectively). This study confirms that SROT is feasible for a proportion of ITP patients treated with eltrombopag. Some biological parameters were predictive of response.

Eltrombopag inhibits Type I interferon-mediated antiviral signaling by decreasing cellular iron

Thrombocytopenia is common among patients with viral hepatitis, limiting the use of antiviral therapy. Eltrombopag (EP) is a thrombopoietin receptor (TPO-R) agonist that has been approved for treatment of immune thrombocytopenia patients with hepatitis virus infection. Interferon-α (IFN-α) plays a crucial role in the antiviral response, and is recommended as the first-line agent for chronic hepatitis B patients. Here, we investigated whether EP inhibits the production of IFN-stimulated genes (ISGs) induced by IFN-α through the TPO-R-independent pathway by mediating reactive oxygen species production by iron chelation. Our results assessed the inhibitory effect of EP on IFN-α signaling, which contributes to the downregulation of ISGs produced by monocytes and sheds light on the underlying mechanisms using iron chelation to treat patients with hepatitis-related immunological thrombocytopenia.

Generation and manipulation of human iPSC-derived platelets

The discovery of iPSCs has led to the ex vivo production of differentiated cells for regenerative medicine. In the case of transfusion products, the derivation of platelets from iPSCs is expected to complement our current blood-donor supplied transfusion system through donor-independent production with complete pathogen-free assurance. This derivation can also overcome alloimmune platelet transfusion refractoriness by resulting in autologous, HLA-homologous or HLA-deficient products. Several developments were necessary to produce a massive number of platelets required for a single transfusion. First, expandable megakaryocytes were established from iPSCs through transgene expression. Second, a turbulent-type bioreactor with improved platelet yield and quality was developed. Third, novel drugs that enabled efficient feeder cell-free conditions were developed. Fourth, the platelet-containing suspension was purified and resuspended in an appropriate buffer. Finally, the platelet product needed to be assured for competency and safety including non-tumorigenicity through in vitro and in vivo preclinical tests. Based on these advancements, a clinical trial has started. The generation of human iPSC-derived platelets could evolve transfusion medicine to the next stage and assure a ubiquitous, safe supply of platelet products. Further, considering the feasibility of gene manipulations in iPSCs, other platelet products may bring forth novel therapeutic measures.

[Management of multirefractory immune thrombocytopenia]

Multirefractory immune thrombocytopenia (ITP) is defined by the absence of response to TPO receptor agonists, rituximab and splenectomy (or contraindicated or refused) and the need of treatment. The approach to multirefractory ITP must be systematic and firstly involves reconsidering the diagnosis. Inherited thrombocytopenia, lymphoid hemopathies and myelodysplastic syndrome are the main causes to be mentioned. Multirefractory ITP is often associated with secondary ITP with signs of clinical or biological autoimmunity, monoclonal gammopathy of undetermined significance and a poor response to corticosteroids. Therapeutic management is complex and is based on the combination of treatments. New treatments are being developed.

On the Quest for In Vitro Platelet Production by Re-Tailoring the Concepts of Megakaryocyte Differentiation

The demand of platelet transfusions is steadily growing worldwide, inter-donor variation, donor dependency, or storability/viability being the main contributing factors to the current global, donor-dependent platelet concentrate shortage concern. In vitro platelet production has been proposed as a plausible alternative to cover, at least partially, the increasing demand. However, in practice, such a logical production strategy does not lack complexity, and hence, efforts are focused internationally on developing large scale industrial methods and technologies to provide efficient, viable, and functional platelet production. This would allow obtaining not only sufficient numbers of platelets but also functional ones fit for all clinical purposes and civil scenarios. In this review, we cover the evolution around the in vitro culture and differentiation of megakaryocytes into platelets, the progress made thus far to bring the culture concept from basic research towards good manufacturing practices certified production, and subsequent clinical trial studies. However, little is known about how these in vitro products should be stored or whether any safety measure should be implemented (e.g., pathogen reduction technology), as well as their quality assessment (how to isolate platelets from the rest of the culture cells, debris, microvesicles, or what their molecular and functional profile is). Importantly, we highlight how the scientific community has overcome the old dogmas and how the new perspectives influence the future of platelet-based therapy for transfusion purposes.

Inherited thrombocytopenias: an updated guide for clinicians

The great advances in the knowledge of inherited thrombocytopenias (ITs) made since the turn of the century have significantly changed our view of these conditions. To date, ITs encompass 45 disorders with different degrees of complexity of the clinical picture and very wide variability in the prognosis. They include forms characterized by thrombocytopenia alone, forms that present with other congenital defects, and conditions that predispose to acquire additional diseases over the course of life. In this review, we recapitulate the clinical features of ITs with emphasis on the forms predisposing to additional diseases. We then discuss the key issues for a rational approach to the diagnosis of ITs in clinical practice. Finally, we aim to provide an updated and comprehensive guide to the treatment of ITs, including the management of hemostatic challenges, the treatment of severe forms, and the approach to the manifestations that add to thrombocytopenia.

Investigation of the efficacy and safety of eltrombopag to correct thrombocytopenia in moderate to severe dengue patients - a phase II randomized controlled clinical trial

BACKGROUND

The dengue-infected patients with or without hemorrhagic manifestations, typically exhibit moderate to severe thrombocytopenia. A thrombopoietin receptor agonist - eltrombopag has been efficacious in correcting thrombocytopenia in patients with various pathological conditions including immune thrombocytopenia, chronic liver disease, and severe aplastic anemia. This study investigated the efficacy and safety of eltrombopag to correct dengue-mediated thrombocytopenia.

METHODS

In this open-label, randomized controlled phase-II trial, patients with dengue fever (DF) and dengue hemorrhagic fever (DHF) having platelet (PLT) count lower than 100 × 109/L without comorbidity, pregnancy, and liver abnormalities were enrolled in Dhaka Medical College Hospital, Better Life Hospital and AMZ hospital, Dhaka, Bangladesh. Between October 10, 2019, and December 30, 2019, 123 DF and DHF patients were assessed for eligibility to be enrolled in the trial. Fourteen patients were excluded as they failed to fulfill the inclusion criteria (N = 6) or refused to participate in the trial (N = 8). Finally, 109 patients were randomly assigned to either Group 1, (N = 36), Group 2 (N = 37), or Control-group (N = 36) in a 1:1:1 ratio. Two doses of eltrombopag - 25 mg/day and 50 mg/day were administered to Group-1 and Group-2 patients, respectively whereas the control-group patients received standard dengue treatment without eltrombopag. The management of all enrolled patients was according to WHO guidelines. The randomization procedure was performed by using a computerized system (STATA Inc.). CBC and immature platelet fraction (IPF) were monitored from Day-0 to Day-7. Absolute immature platelet count (A-IPC) was calculated from PLT count and IPF for each patient. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured on Day-0 and Day-4 and an Ultrasonogram (USG) of the abdomen was performed on Day-4 and Day-7 for each patient. The efficacy of eltrombopag as the primary outcome of the trial was investigated by the proportion of patients with recovered platelet count receiving eltrombopag with corrected platelet count (platelet count above the lower normal limit: 150 × 109/L) on Day-7 of the enrollment as compared to the Control-group. As the secondary outcomes, the reduction of bleeding tendency in response to eltrombopag as well as the safety of eltrombopag in dengue patients were assessed. The safety was evaluated in case of adverse events, liver function enzymes AST/ALT levels and USG. This trial is registered with the international clinical trial registry, number SLCTR/2019/037.

RESULTS

A total of 101 patients including 77 DF and 24 DHF patients completed the trial as eight patients left the trial without completing the follow-up. Patients of the different groups were compared with respect to mean age (26±8, 30±10 and 30±9 years for, Group-1,-2 and Control-group, respectively) (p-value= 0.23) and basal PLT count (Group-1: 58±24 × 109; Group-2: 52±29 × 109 and control-group: 55±30 × 109) (p-value= 0.63). The mean PLT counts for Group-1 (332 × 109/L ± 92) and Group-2 (371 × 109/L ± 111) were significantly higher than control-group (194 × 109/L ± 96) on Day-7 (adjusted p-value= 1.15 × 10-06 for Group-1 vs. Control-group, and adjusted p-value= 1.82 × 10-08 for Group-2 vs. Control-group).). On Day-7, 91% of Group-1 (N = 30) and Group-2 (N = 32) patients who received eltrombopag achieved primary endpoint of PLT count above than lower normal limit (150 × 109/L) (Group-1: 91%, OR: 8.33, 95% CI: 2.11 to 32.80, p-value: 0.0024 and Group-2: 91%, OR: 8.89, 95% CI: 2.26 to 34.89, p-value: 0.0017) compared to 55% (N = 18) of control-group patients who did not receive eltrombopag. The bleeding manifestations for thirteen out of fourteen grade-II DHF patients were subsided within Day-7 who received eltrombopag, whereas four out of ten grade-II DHF patients with PLT counts lower than the lower normal limit in the control group showed intermittent bleeding symptoms throughout the trial period. Mean A-IPC but not IPF was significantly higher for eltrombopag-treated groups in comparison to the Control-group. The frequency of the most common adverse events (vomiting and diarrheal tendencies) was similar in the treated-and control-groups (N = 5, 15%, and N = 3, 9% for Group-1 and -2, respectively vs. N = 4, 12% in the Control-group). Ten (30%) patients of Group-1 and, fourteen (40%) patients of Group-2 showed increased AST (U/L) as opposed to nine patients (27%) in the Control-group. Increased ALT levels were observed for three (9%), nine (26%), and seven (21%) patients belonging to the Group-1, -2, and Control-group, respectively. PLT counts higher than the upper normal limit (450 × 109/L) on Day-7 were observed for seven patients who were administered the higher dose (50 mg/day) in contrast to the three patients receiving the lower dose (25 mg/day). USG reports did not show thrombosis events in any of the patients.

INTERPRETATION

The trial revealed that the administration of eltrombopag in a short regimen for three days was efficacious to restore the PLT count in DF and DHF patients. The higher number of A-IPCs in eltrombopag treated patients underscored the possible mode of action of eltrombopag through stimulating megakaryopoiesis in dengue patients. The trial hints toward the positive effect of eltrombopag in the cessation of bleeding manifestation. Administration of the lower dose (25 mg/day) of eltrombopag was shown to be safer and equally efficacious to the higher dose (50 mg/day) in treating dengue-infected patients.

Romiplostim in adults with newly diagnosed or persistent immune thrombocytopenia

Introduction: Three distinct phases are recognized in immune thrombocytopenia (ITP): newly diagnosed (≤3 months after diagnosis), persistent (>3-12 months after diagnosis), and chronic (>12 months). Several international guidelines/expert recommendations have been released in the past 2 years regarding the treatment of newly diagnosed/persistent ITP. Areas covered: Across the guidelines/expert recommendations, thrombopoietin receptor agonists (TPO-RAs), including romiplostim (the focus of this review), are recommended in newly diagnosed or persistent ITP for patients who fail to respond to corticosteroids or intravenous immunoglobulin (or where these are contraindicated). To identify data relating to romiplostim in adults with newly diagnosed or persistent ITP, we conducted a search of PubMed (with no time limit applied) and abstracts from 2019 EHA/ASH meetings using the term 'romiplostim.' Expert opinion: The findings from nine clinical trials, six real-world studies and ten case reports provide insight into the early use of romiplostim, which could help to reduce exposure to the adverse effects associated with prolonged corticosteroid use, as well as reduce the risk of severe bleeding. Additionally, given the durable responses observed in patients with newly diagnosed/persistent ITP, as well as the potential for treatment-free responses following discontinuation, romiplostim might help to avoid the need for subsequent treatment.

Eltrombopag inhibits the proliferation of Ewing sarcoma cells via iron chelation and impaired DNA replication

Background

The treatment of Ewing sarcoma, an aggressive bone and soft tissue sarcoma, is associated with suboptimal outcomes and significant side-effects. Consequently, there is an urgent need to identify novel therapies that will improve outcomes for children and adults with Ewing sarcoma tumors while also decreasing treatment-related toxicities.

Methods

We analyzed data from the PRISM drug repurposing screen, which tested the activity of 4518 drugs across 578 cancer cell lines, to identify drugs that selectively inhibit the growth of Ewing sarcoma cell lines. We then tested the effects of a top hit from the screen on cell proliferation, cell cycle progression, and activation of the DNA damage pathway using Ewing sarcoma cell lines. We also used a CRISPR/Cas9 gene knockout approach to investigate the role of Schlafen 11 (SLFN11), a restriction factor for DNA replication stress that is overexpressed in Ewing sarcoma tumors, in mediating the sensitivity of Ewing sarcoma cells to the drug.

Results

We found that eltrombopag, an FDA-approved thrombopoietin-receptor agonist (TPO-RA) that is currently being evaluated as a treatment for chemotherapy-induced thrombocytopenia, inhibits the growth of Ewing sarcoma cell lines in vitro in proliferation and colony formation assays. However, from a mechanistic standpoint, the thrombopoietin receptor is not expressed in Ewing sarcoma cells and we show that eltrombopag impairs DNA replication and causes DNA damage in Ewing sarcoma cells by chelating iron, a known “off-target” effect of the drug. We also found that the sensitivity of Ewing sarcoma cells to eltrombopag is mediated, in part, by SLFN11, which regulates the cellular response to DNA replication stress.

Conclusions

Ewing sarcoma cell lines are sensitive to eltrombopag and this drug could improve outcomes for patients with Ewing sarcoma tumors by both targeting the tumor, via chelation of iron and inhibition of DNA replication, and reducing chemotherapy-induced thrombocytopenia, via stimulation of the thrombopoietin receptor.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12885-020-07668-6.

[Efficacy and safety of eltrombopag in aplastic anemia: A multi-center survey in China]

Objective: To evaluate the safety and efficacy of eltrombopag combined with immunosuppressive therapy in patients with aplastic anemia (AA) in China. Methods: We investigated and analyzed the clinical data of AA patients from 14 hematological treatment centers who were treated with oral eltrombopag for at least 3 mon. Results: We enrolled 56 AA patients, including 19 treatment-naïve patients and 37 IST-refractory patients. The median administration period for eltrombopag was 7 (3-31) months, and the median maximum stable dosage was 75 mg/d (50-150 mg/d) . The 3-month hematological response (HR) rate was 60%, and the complete response (CR) rate was 30% in 10 SAA patients who were treated with first-line eltrombopag and standard IST (ATG+CsA) . Eight of 9 eltrombopag and CsA ± androgen first-line treated SAA patients responded (8/9, 89%) and 4 (44%) gave CR. The overall HR and CR rates were 79% and 52.6%, respectively, among these 19 patients by the end of the follow-up period. Of the 19 AA patients who were refractory to CsA ± androgen, 11 achieved HR (57.9%) at 3 mon, and the best HR rate was 44% in standard IST (ATG+CsA) refractory 18 patients after eltrombopag treatment. Fifty-one percent of the patients experienced mild or moderate adverse events, and gastrointestinal discomfort was the most common adverse effect reported by the study subjects. Conclusion: Adding Eltrombopag in first-line IST can accelerate the acquisition and improve the quality of hematological responses in AA patients. AA with relatively more residual hematopoietic cells may be well treated with eltrombopag and non-ATG IST. Eltrombopag can be used as salvage therapy for CsA±androgen refractory patients. Eltrombopag was generally safe and well tolerated by AA patients in China.

Hemostatic changes by thrombopoietin-receptor agonists in immune thrombocytopenia patients

Thrombopoietin receptor agonist (TPO-RA) treatment increases the thrombosis rate in immune thrombocytopenia (ITP). We hypothesize that TPO-RAs influence platelet function, global and secondary hemostasis and/or fibrinolysis. A systematic review was performed. If possible, data were compared between responders (relevant increase in platelet count), and non-responders. Twelve observational studies with 305 patients were included (responders (127/150 (85%))). There were indications that TPO-RA treatment enhanced platelet function, with respect to platelet-monocyte aggregates, soluble P-selectin, GPVI expression, and adhesion under flow. Studies addressing global and secondary hemostasis and fibrinolysis were scarce. Overall, no changes were found during TPO-RA treatment, apart from an accelerated clot formation and conflicting data on levels of plasminogen activator inhibitor (PAI)-1. The parameters that increased have previously been associated with thrombosis in other patient groups, and might contribute to the increased rate of thrombosis observed in TPO-RA-treated ITP patients.

First-in-patient study of hetrombopag in patients with chronic idiopathic thrombocytopenic purpura

BACKGROUND

Idiopathic thrombocytopenic purpura (ITP) especially refractory and (or) relapsed ITP, is a serious and global health burden and its clinical treatment is far from being satisfied. Hetrombopag is a novel, small-molecule thrombopoietin receptor agonist for the treatment of chronic idiopathic thrombocytopenic purpura (CITP).

OBJECTIVES

This first-in-patient study aimed to investigate the safety, pharmacokinetics, and anticipated therapeutic dose of hetrombopag in CITP patients.

METHODS

In this multicenter, first-in-patient study, CITP patients received hetrombopag in a dose escalation (2.5 mg/day, 5 mg/day, or 7.5 mg/day) cohort. All patients received hetrombopag in fasting condition once daily for 2 weeks.

RESULTS

Of 44 patients screened, 32 were enrolled and treated. Most adverse events were graded 1 to 2 (ie, mild to moderate), and the incidence and severity were similar for three study cohorts. The pharmacokinetics of hetrombopag were found to be nonlinear with greater than dose-proportional: 12.5% of patients (1/8) in the 2.5 mg/d cohort, 58.3% of patients (7/12) in the 5 mg/d cohort, 66.7% of patients (8/12) in the 7.5 mg/d cohort reached the primary study endpoint of a platelet count exceeding 50 × 109 /L on day 28.

CONCLUSION

Hetrombopag was well tolerated and preliminarily efficacious. Efficacy, safety, and pharmacokinetic data suggest that 7.5 mg hetrombopag once daily was the anticipated therapeutic dose of hetrombopag in CITP patients and has been recommended for investigation in a later confirmatory clinical study of hetrombopag.

Cancer risk in patients with primary immune thrombocytopenia - A Swedish nationwide register study

BACKGROUND

Immune thrombocytopenia (ITP) is an autoimmune disease treated with immunosuppressive agents, thrombopoietin receptor agonists, immunomodulation drugs and/or splenectomy. Patients with ITP have been found to have increased risk ofhematological malignancies. Studies investigating stomach/liver cancer are contradictory and the risk of developing other solid tumors is largely unknown. We aimed at estimating risk of overall and organ-specific cancers in patients with primary ITP.

METHODS

The study population was Swedish patients with at least one ITP diagnosis recorded in the National Patient Register and a 1:10 matched comparison cohort from the population. The study period covers 1997-2016. The Cancer Register and the Cause of Death Register provided data on malignancies and deaths, respectively. Primary ITP was identified using an established algorithm. We used time-split Cox models to estimate hazard ratios (HRs) with 95 % confidence intervals (CIs), adjusted for age, sex, index-year, county, income, education, Charlson score and number of in- and outpatient contacts.

RESULTS

In total 66,134 individuals were included in the study. Patients with ITP had higher risk of gastro-intestinal, skin (all morphologies), lymphoid and hematological cancers. Adjusted HR (95 % CI) for cancer was 1.37 (1.27-1.48), with highest risk during the first year, but with increased risk remaining for up to 20 years for men. For women, the overall risk was increased during the first year, HR (95 % CI) 2.00 (1.55-2.60). A significantly increased liver cancer risk was seen up to 9 years after diagnosis.

CONCLUSION

Patients with primary ITP have higher risk of cancer than the population. The observed increased risk does not seem to be solely due to surveillance bias, but might be associated with ITP or its treatments. Treating hematologists need to have high index of suspicion for cancer.

Ribosomopathies: New Therapeutic Perspectives

Ribosomopathies are a group of rare diseases in which genetic mutations cause defects in either ribosome biogenesis or function, given specific phenotypes. Ribosomal proteins, and multiple other factors that are necessary for ribosome biogenesis (rRNA processing, assembly of subunits, export to cytoplasm), can be affected in ribosomopathies. Despite the need for ribosomes in all cell types, these diseases result mainly in tissue-specific impairments. Depending on the type of ribosomopathy and its pathogenicity, there are many potential therapeutic targets. The present manuscript will review our knowledge of ribosomopathies, discuss current treatments, and introduce the new therapeutic perspectives based on recent research. Diamond–Blackfan anemia, currently treated with blood transfusion prior to steroids, could be managed with a range of new compounds, acting mainly on anemia, such as L-leucine. Treacher Collins syndrome could be managed by various treatments, but it has recently been shown that proteasomal inhibition by MG132 or Bortezomib may improve cranial skeleton malformations. Developmental defects resulting from ribosomopathies could be also treated pharmacologically after birth. It might thus be possible to treat certain ribosomopathies without using multiple treatments such as surgery and transplants. Ribosomopathies remain an open field in the search for new therapeutic approaches based on our recent understanding of the role of ribosomes and progress in gene therapy for curing genetic disorders.

Romiplostim is effective for eltrombopag-refractory aplastic anemia: results of a retrospective study

Eltrombopag (EPAG) and romiplostim (ROM), thrombopoietin receptor-agonists with demonstrated efficacy against aplastic anemia (AA) in prospective controlled studies, were authorized in Japan for use in adults with aplastic anemia in 2017 and 2019, respectively. So far, no data are available on the potential contribution of switching from ROM to EPAG or vice versa in terms of efficacy or tolerance. Efficacies and tolerance profiles of ten patients, who failed to respond to the maximum dose of EPAG and then switched to ROM, were evaluated. All ten patients received a maximum dose of ROM (20 μg/kg/week). At a median follow-up of twelve months, seven of ten patients (70%) had achieved either neutrophil, erythroid, or platelet response, including one complete response. No patients showed platelet count fluctuations that were reported during ROM treatment for immune thrombocytopenia. In univariate analysis of the relationship between efficacy and demographics, the response had a correlation with neither factors. None of the patients stopped the ROM treatment because of adverse events. Although a larger number of patients and a longer follow-up period are needed to confirm our findings, our results show the efficacy of ROM in patients with EPAG-refractory AA.

Platelet Dysfunction Diseases and Conditions: Clinical Implications and Considerations

INTRODUCTION

Platelet diseases and dysfunction are taught early in medical school to all future physicians. Understanding of the coagulation cascade and hemostatic mechanisms has allowed for targeted pharmacological therapies that have been significantly impactful in clinical practice. Platelets are an early participant in hemostasis physiologically and under pathophysiological states.

METHODS

A review of literature involving platelet disfunction.

RESULTS

Various presentations of platelet diseases and dysfunction challenge clinicians and require a firm understanding of normal platelet function, drugs that mediate or modulate platelet effectiveness, and nonpharmacologic etiologies of platelet diseases and dysfunction with corresponding best practice treatment approaches.

CONCLUSION

This review summarizes normal and abnormal states associated with platelets and treatment strategies.

Thrombopoietin Receptor Agonists in Patients with Chronic Liver Disease

Thrombocytopenia is one of the most common hematologic complications in cirrhosis. Despite limited data linking platelet count and bleeding risk in patients with cirrhosis, the use of platelets transfusions for invasive procedures has been a common practice. Recently, thrombopoietin (TPO) receptor agonists have been approved for use in patients with chronic liver disease (CLD) undergoing invasive procedures. The aim of this study was to review current literature on bleeding risk in patients with cirrhosis and the use of platelet transfusions and TPO receptor agonists in the context of invasive procedures. PubMed search was conducted to find articles relating to cirrhosis, thrombocytopenia, and new novel treatments for this condition. Search terms included CLD, cirrhosis, thrombocytopenia, bleeding, thrombosis, coagulopathy, hemostasis, and TPO receptor agonists. Romiplostim, eltrombopag, avatrombopag, and lusutrombopag are approved TPO receptor agonists, with avatrombopag and lusutrombopag specifically approved for use in patients with CLD undergoing invasive procedures. In patients with platelet counts < 50,000/mm³, avatrombopag and lusutrombopag increased the platelet counts above this threshold in the majority of treated patients and reduced the frequency of platelet transfusions. At the approved doses, incidence of thrombosis was not increased and therapies were well tolerated. Studies were not powered to assess whether risk of bleeding complications was reduced and the fundamental question of whether correction of thrombocytopenia is warranted in patients undergoing invasive procedures remains unanswered. The use of TPO receptor agonists has resulted in less requirement for platelet transfusions. In patients with cirrhosis undergoing invasive procedures for whom platelet transfusion is planned, TPO receptor agonists are an alternative and avoid the risks associated with transfusions. However, there is need for a thoughtful approach to manage bleeding risk in patients with cirrhosis undergoing procedures, with the consideration of a comprehensive hemostatic profile, the severity of portal hypertension, and the complexity of the invasive procedure to guide decisions regarding transfusions or use of TPO receptor agonists.

[Evaluation of the efficacy of cyclosporin A combined with recombined human thrombopoietin for treating patients with non-severe aplastic anemia]

Objectives: To compare the efficacy of cyclosporin A (CsA) alone and CsA combined with recombined human thrombopoietin (rhTPO) in patients with non-severe aplastic anemia (NSAA) . Methods: Data from 83 patients with NSAA between August 2014 and February 2019 were collected retrospectively. The study population included 35 men and 48 women, with a median age of 45 years (14-85 years) . Among them, 57 had been treated with CsA + rhTPO, TPO was administered at 15 000 U QD for 7 days, once a month for 3 months, and the other 26 patients with compatible baseline characters were treated with CsA alone. All the enrolled patients had been treated with CsA for at least 6 months and were followed up for at least 1 year. The efficacy and outcome were compared between the two groups. Results: Total 23 men and 34 women, with a median age of 46 years (14-85 years) were treated with CsA + rhTPO. The median duration of CsA treatment was 17 (8-28) months, and the patients were followed up for a median of 27 (12-45) months. Total 12 men and 14 women, with a median age of 40 years (20-64) were treated with CsA alone. The median duration of CsA treatment was 19 months (9-30 months) , and the median follow-up duration was 29 months (16-66 months) . There was no significant difference in the baseline characteristics of the two groups (P>0.05) . There was no significant difference in the CR and OR rates of the two groups at 1, 3, 6, 12, and 24 months of treatment (P>0.05) . The change in the platelet level for the CsA + rhTPO treated group after 1 month[8 (-12-86) ×10(9)/L vs. 3 (16-57) ×10(9)/L, P=0.029) , 3 months[24 (-6-102) ×10(9)/L vs. 7 (-9-76) ×10(9)/L, P=0.006], and 6 months[33.5 (-4-123) ×10(9)/L vs. 12.5 (-14-109) ×10(9)/L, P=0.048] of treatment was higher than that in the CsA alone group, while no significant difference was found between the two groups at other time points. There was no significant difference in the change in the megakaryocyte level between the two groups[3 (0-4) vs. 2 (0-5) , z=-0.868, P=0.385] after 6 months of treatment. Apart from 10.5% (6/57) of the patients in the CsA + rhTPO treated group who reported soreness at the injection site, there was no other significant difference between the two groups in terms of adverse effects. During the follow-up period, there were two cases of increasing paroxysmal nocturnal hemoglobinuria clone to over 10%, one in the CsA + rhTPO treated group, the other in the CsA alone group; and there was one case of progression to SAA in the CsA + rhTPO treated group; while no case of death or thromboembolic event (TEE) , fibrosis or reticulin proliferation, progression to myelodysplastic syndrome (MDS) , or acute myeloid leukemia was observed in either group. There was one case of progression to SAA in the CsA + rhTPO treated group but none in the CsA alone group. Conclusion: Compared to CsA alone, CsA + rhTPO treatment can accelerate the recovery of the platelet level with acceptable adverse effects.

Impact of Anti-GPIIb/IIIa Antibody-Producing B Cells as a Predictor of the Response to Lusutrombopag in Thrombocytopenic Patients with Liver Disease

BACKGROUND

To make an accurate estimate of the response to thrombopoietin (TPO) receptor agonists for thrombocytopenia associated with chronic liver disease, we evaluated the influence of antiplatelet autoantibodies on the response to lusutrombopag in thrombocytopenic patients with liver disease.

METHODS

A prospective study was conducted at 2 hospitals. Thrombocytopenic patients with liver disease received oral lusutrombopag 3.0 mg once daily for up to 7 days. We analyzed changes in platelet counts from baseline to the maximum platelet count on days 9-14. The definition of clinical response was a platelet count of ≥5 × 104/μL with an increased platelet count of ≥2 × 104/μL from baseline. We assessed the correlation between the response to treatment drug and antiplatelet autoantibodies measured by anti-GPIIb/IIIa antibody-producing B cells.

RESULTS

Thirty patients received the trial drug. There were 25 responders and 5 nonresponders. The median change in platelet counts was 3.9 × 104/μL (95% CI 2.8-4.6, p < 0.0001). The correlation between change in platelet counts and the frequency of the anti-glycoprotein IIb/IIIa antibody-producing B cells was moderate (r = 0.414, 95% CI 0.064-0.674, p = 0.023). In multivariate analysis of factors affecting the change in platelet counts, the anti-GPIIb/IIIa antibody-producing B cells were identified as an independent factor (regression coefficient [B] = 0.089; CI 0.021-0.157, p = 0.013).

CONCLUSION

Anti-GPIIb/IIIa antibody-producing B cells may be a predictor for TPO receptor agonists in patients with chronic liver disease.

Proteomic changes by radio-mitigative thrombopoietin receptor agonist romiplostim in the blood of mice exposed to lethal total-body irradiation

PURPOSE

The thrombopoietin receptor agonist romiplostim (RP) is a therapeutic agent for immune thrombocytopenia that can achieve complete survival in mice exposed to a lethal dose of ionizing radiation. The estimated mechanism of the radio-protective/mitigative effects of RP has been proposed; however, the detailed mechanism of action remains unclear. This study aimed to elucidate the mechanism of the radio-protective/mitigative effects of RP, the fluctuation of protein in the blood was analyzed by proteomics.

MATERIALS AND METHODS

Eight-week-old female C57BL/6J mice were randomly divided into 5 groups; control at day 0, total-body irradiation (TBI) groups at day 10 and day 18, and TBI plus RP groups at day 10 and day18, consisting of 3 mice per group, and subjected to TBI with 7 Gy of ¹³⁷Cs γ-rays at a dose rate of 0.74 Gy/min. RP was administered intraperitoneally to mice at a dose of 50 µg/kg once daily for 3 days starting 2 hours after TBI. On day 10 and day 18 after TBI, serum collected from each mouse was analyzed by liquid chromatography tandem mass spectrometry.

RESULTS

Nine proteins were identified by proteomics methods from 269 analyzed proteins detected in mice exposed to a lethal dose of TBI: keratin, type II cytoskeletal 1 (KRT1), fructose-1, 6-bisphosphatase (FBP1), cytosolic 10-formyltetrahydrofolate dehydrogenase (ALDH1L1), peptidyl-prolyl cis-trans isomerase A (PPIA), glycine N-methyltransferase (GNMT), glutathione S-transferase Mu 1 (GSTM1), regucalcin (RGN), fructose-bisphosphate aldolase B (ALDOB) and betain-homocysteine S-methyltransferase 1 (BHMT). On the 10th day after TBI, KRT1 was significantly increased (p < 0.05) by 4.26-fold compared to the control group in the TBI group and significantly inhibited in the TBI plus RP group (p < 0.05). Similarly, the expression levels of other 8 proteins detected at 18th day after TBI were significantly increased by 4.29 to 27.44-fold in the TBI group, but significantly decreased in the TBI plus RP group compared to the TBI group, respectively.

CONCLUSION

Nine proteins were identified by proteomics methods from 269 analyzed proteins detected in mice exposed to a lethal dose of TBI. These proteins are also expected to be indicators of the damage induced by high-dose radiation.

Pathogenesis of Thrombocytopenia in Chronic HCV Infection: A Review

A large proportion of patients with chronic hepatitis C have associated thrombocytopenia (TCP). Due to bleeding risks, TCP, when severe, can limit diagnostic and therapeutic procedures, treatments, and increases risk of complications, especially excessive bleeding. It is important to understand the mechanisms that cause TCP in order to manage it. In general, TCP can be due to increased destruction or decreased production. Proposed mechanisms of increased destruction include autoantibodies to platelets and hypersplenism with sequestration. Proposed mechanisms of decreased production include virus-induced bone marrow suppression and decreased TPO production. Autoantibodies directed against platelet surface antigens have demonstrated an inverse correlation with platelet counts. Hypersplenism with sequestration involves the interaction of portal hypertension, splenomegaly, and platelet destruction. Decreased production mechanisms involve appropriate and inappropriate levels of TPO secretion. There is limited evidence to support viral-induced bone marrow suppression. In contrast, there is strong evidence to support low levels of TPO in liver failure as a major cause of TCP. TPO-agonists, specifically eltrombopag, have been shown in hepatitis C patients to increase platelet counts without reducing portal hypertension or splenomegaly. We conclude that TCP in hepatitis C virus-induced liver disease is often multifactorial, but an understanding of the mechanisms can lead to judicious use of new drugs for treatment.

Inherited thrombocytopenias: history, advances and perspectives

Over the last 100 years the role of platelets in hemostatic events and their production by megakaryocytes have gradually been defined. Progressively, thrombocytopenia was recognized as a cause of bleeding, first through an acquired immune disorder; then, since 1948, when Bernard-Soulier syndrome was first described, inherited thrombocytopenia became a fascinating example of Mendelian disease. The platelet count is often severely decreased and platelet size variable; associated platelet function defects frequently aggravate bleeding. Macrothrombocytopenia with variable proportions of enlarged platelets is common. The number of circulating platelets will depend on platelet production, consumption and lifespan. The bulk of macrothrombocytopenias arise from defects in megakaryopoiesis with causal variants in transcription factor genes giving rise to altered stem cell differentiation and changes in early megakaryocyte development and maturation. Genes encoding surface receptors, cytoskeletal and signaling proteins also feature prominently and Sanger sequencing associated with careful phenotyping has allowed their early classification. It quickly became apparent that many inherited thrombocytopenias are syndromic while others are linked to an increased risk of hematologic malignancies. In the last decade, the application of next-generation sequencing, including whole exome sequencing, and the use of gene platforms for rapid testing have greatly accelerated the discovery of causal genes and extended the list of variants in more common disorders. Genes linked to an increased platelet turnover and apoptosis have also been identified. The current challenges are now to use next-generation sequencing in first-step screening and to define bleeding risk and treatment better.

Real-world evidence on clinical outcomes in immune thrombocytopenia treated with thrombopoietin receptor agonists

Aim: Eltrombopag and romiplostim are US FDA approved for treatment of immune thrombocytopenia in patients with insufficient response to other treatments. Clinical or real-world data comparing outcomes of the two drugs are limited. Methods: This retrospective cross-sectional study sought information on bleeding-related episodes (BREs), adverse events (AEs) and other outcomes of eltrombopag or romiplostim treatment in immune thrombocytopenia. Results: Patients receiving eltrombopag experienced significantly reduced BREs, severe BREs, rescue medication use and platelet transfusions. Diarrhea and headache were significantly less frequent in patients receiving eltrombopag; other AEs occurred equally in both groups. Conclusion: There may be a potential advantage for the use of eltrombopag versus romiplostim in the practice settings studied, based on rates of BREs and AEs and rescue medication utilization.

Thrombopoietin enhances hematopoietic stem and progenitor cell homing by impeding matrix metalloproteinase 9 expression

We reported a novel function of recombinant human thrombopoietin (TPO) in increasing hematopoietic stem and progenitor cell (HSPC) homing to the bone marrow (BM). Single doses of TPO treatment to the recipients immediately after BM transplantation showed significantly improved homing of HSPCs to the BM, which subsequently resulted in enhanced short‐ and long‐term engraftment of HSPCs in mice. We found that TPO could downregulate the expression and secretion of matrix metalloproteinase 9 in BM cells. As a result, SDF‐1α level was increased in the BM niche. Blocking the interaction of SDF‐1α and CXCR4 on HSPCs by using AMD3100 could significantly reverse the TPO‐enhanced HSPC homing effect. More importantly, a single dose of TPO remarkably promoted human HSPC homing and subsequent engraftment to the BM of nonobese diabetic/severe combined immunodeficiency mice. We then performed a clinical trial to evaluate the effect of TPO treatment in patients receiving haploidentical BM and mobilized peripheral blood transplantation. Surprisingly, single doses of TPO treatment to patients followed by hematopoietic stem cell transplantation significantly improved platelet engraftment in the cohort of patients with severe aplastic anemia (SAA). The mean volume of platelet and red blood cell transfusion was remarkably reduced in the cohort of patients with SAA or hematological malignancies receiving TPO treatment. Thus, our data provide a simple, feasible, and efficient approach to improve clinical outcomes in patients with allogenic hematopoietic stem cell transplantation. The clinical trial was registered in the Chinese Clinical Trial Registry website (http://www.chictr.org.cn) as ChiCTR‐OIN‐1701083.

Management of immune thrombocytopenia in women: current standards and special considerations

Introduction: Immune thrombocytopenia (ITP) is an acquired autoimmune disorder, with an incidence rate of 20-40/million adults/year and an estimated prevalence in women of childbearing age of 24.5/million.Areas covered: Authors discuss management of ITP in pregnancy, treatment-related toxicity, delivery, neonatal thrombocytopenia and breastfeeding, and other women's specific issues. The search of papers published between January 1990 and December 2019 was done on PubMed using combinations of the keywords below. The distinction between ITP and other thrombocytopenias in pregnancy is of paramount importance. The current belief (at variance with the past) that ITP is a relatively benign disease pregnancy is emphasized.Expert opinion: The lack of randomized, prospective, controlled studies hampers evidence-based statements. Remarkably, ITP diagnosis is still one of exclusion, there are no clinical or laboratory criteria for prognosis and we still need more solid data on the risks related to neonatal thrombocytopenia. Corticosteroids and IVIG remain the mainstay of treatment, since rituximab, thrombopoietin-receptor agonists, fostamatinib may be toxic in pregnancy. Safety and efficacy of recombinant-human-thrombopoietin, available in China, require confirmation studies. Quality of life and women-related toxicity of treatments in young girls, adults, and elders are still an orphan area of investigation.