Thrombopoietin Receptor Research Articles

Efficacy and Safety of Avatrombopag in Combination with Standard Immunosuppressive Therapy for Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a life-threatening bone marrow failure disease. The addition of eltrombopag to immunosuppressive therapy (IST) improves the response rate and response quality of SAAs, but its hepatotoxicity is concerning. Avatrombopag (AVA), another small-molecule thrombopoietin receptor agonist without hepatotoxicity, has unknown efficacy in SAA treatment. This retrospective study aimed to assess the efficacy and safety of AVA, a small-molecule thrombopoietin receptor agonist, when added to IST in SAA patients. A total of 42 patients treated with IST and AVA were compared to a historical cohort of 84 patients receiving IST alone, utilizing propensity score matching. The median age was 31.5 (6.0-67.0) years old in Group A and 26 (16.0-45.0) years old in Group B. At 3 months, Group A showed higher complete response (CR) and overall response (OR) rates than Group B (CR: 19.0% vs. 4.8%, P = 0.024; OR: 54.8% vs. 39.3%, P=0.145). Higher CR and OR rates were also found at 6 months in Group A than in Group B (CR 31.0% vs. 14.3%, P=0.145; OR 71.4% vs. 51.2%, P=0.048). In multivariate analysis of Group A, a shorter interval from disease onset to anti-thymocyte globulin (ATG) treatment (≤6 months) (P=0.005) predicted better responses rate at 6 months. Event free survival was also improved in Group A (60.7% vs. 49.6%). AVA was well-tolerated, with no hepatic injury observed during treatment, even in those with pre-existing hepatic impairment. The addition of AVA to IST improves both the response rate and response quality in SAA patients while ensuring safety.

A study of platelet function in patients with chronic immune thrombocytopenia treated with thrombopoietin receptor agonists

BackgroundThrombopoietin receptor agonists (TPO-RAs) are widely used in immune thrombocytopenia (ITP) and are associated with increased thrombotic risk. However, data regarding their impact on platelet function is scarce. MethodsPlatelet function was evaluated in chronic ITP patients enrolled over one year, using light transmission aggregometry and platelet-derived microparticle (PMP) levels measurement with flow cytometry. Aggregation responses to various concentrations of ADP, collagen, ristocetin, and PMP levels were compared between TPO-RA-treated patients, patients treated with other agents and healthy individuals. ResultsTPO-RA-treated patients (n = 24) displayed significantly reduced aggregation responses to 2.5 μM, 5 μM, and 10 μM of ADP and collagen compared to 15 healthy individuals (59.5 % vs. 87.6 %, p < .0001, 43.6 % vs. 79.9 %, p < .0001, 26.1 % vs. 75.2 %, p < .0001, 67.2 % vs. 86 %, p < .0001, respectively). Reduced responses to ADP and collagen were also recorded in patients treated with other agents (n = 16) compared to healthy controls but without difference between the two treatment groups. Aggregation response to ristocetin was normal in all three groups. None of the patients yielded enhanced platelet aggregation. In TPO-RA-treated patients, a strong positive correlation between platelet counts and aggregation response to ristocetin was observed (rs = 0.65, p = .0005). PMP levels were significantly elevated in TPO-RA-treated patients compared to patients treated with other agents (49.5 vs 4.5 events/uL, p < .0001) and healthy controls (5 events/uL, p < .0001). ConclusionsThese results suggest that TPO-RAs may not enhance platelet aggregation responses, whereas impaired responses may be a disease feature. Furthermore, TPO-RAs may increase PMP levels and thus be implicated in the modulation of platelet function in ITP patients.

Thrombopoietin mimetic reduces mouse lung inflammation and fibrosis after radiation by attenuating activated endothelial phenotypes.

Radiation-induced lung injury (RILI) initiates radiation pneumonitis and progresses to fibrosis as the main side effect experienced by patients with lung cancer treated with radiotherapy. There is no effective drug for RILI. Sustained vascular activation is a major contributor to the establishment of chronic disease. Here, using a whole thoracic irradiation (WTI) mouse model, we investigated the mechanisms and effectiveness of thrombopoietin mimetic (TPOm) for preventing RILI. We demonstrated that administering TPOm 24 hours before irradiation decreased histologic lung injury score, apoptosis, vascular permeability, expression of proinflammatory cytokines, and neutrophil infiltration in the lungs of mice 2 weeks after WTI. We described the expression of c-MPL, a TPO receptor, in mouse primary pulmonary microvascular endothelial cells, showing that TPOm reduced endothelial cell-neutrophil adhesion by inhibiting ICAM-1 expression. Seven months after WTI, TPOm-treated lung exhibited less collagen deposition and expression of MMP-9, TIMP-1, IL-6, TGF-β, and p21. Moreover, TPOm improved lung vascular structure, lung density, and respiration rate, leading to a prolonged survival time after WTI. Single-cell RNA sequencing analysis of lungs 2 weeks after WTI revealed that TPOm shifted populations of capillary endothelial cells toward a less activated and more homeostatic phenotype. Taken together, TPOm is protective for RILI by inhibiting endothelial cell activation.

LMAN1 serves as a cargo receptor for thrombopoietin.

Thrombopoietin (TPO) is a plasma glycoprotein that binds its receptor on megakaryocytes (MK) and MK progenitors, resulting in enhanced platelet production. The mechanism by which TPO is secreted from hepatocytes remains poorly understood. LMAN1 and MCFD2 form a complex at the endoplasmic reticulum membrane, recruiting cargo proteins into COPII vesicles for secretion. In this study, we showed that LMAN1 deficient mice (with complete germline LMAN1 deficiency) exhibited mild thrombocytopenia, whereas the platelet count was entirely normal in mice with approximately 7% Lman1 expression. Surprisingly, mice deleted for Mcfd2 did not exhibit thrombocytopenia. Analysis of peripheral blood from LMAN1 deficient mice demonstrated normal platelet size and normal morphology of dense and alpha granules. LMAN1 deficient mice exhibited a trend toward reduced MK and MK progenitors in the bone marrow. We next showed that hepatocyte-specific but not hematopoietic Lman1 deletion results in thrombocytopenia, with plasma TPO level reduced in LMAN1 deficient mice, despite normal Tpo mRNA levels in LMAN1 deficient livers. TPO and LMAN1 interacted by co-immunoprecipitation in a heterologous cell line and TPO accumulated intracellularly in LMAN1 deleted cells. Altogether, these studies confirmed the hepatocyte as the cell of origin for TPO production in vivo and were consistent with LMAN1 as the endoplasmic reticulum cargo receptor that mediates the efficient secretion of TPO. To our knowledge, TPO is the first example of an LMAN1-dependent cargo that is independent of MCFD2.

Extension of impurity profiling on Eltrombopag olamine to in-silico Predictions: An Effort to Exploit correlated forced degradation products and known Drug-Related substances in drug discovery

The recent pandemic has highlighted the impact of diseases on global health and the economy. The rapid discovery of new hit molecules remains a tough challenge. Pharmaceutical impurity profiling can be linked to drug discovery through the identification of new hits from compounds identified during the analytical profiling. The present study demonstrates this linkage through the extension of the impurity (forced degradation) profiling of eltrombopag (ELT) olamine, a thrombopoietin (TPO) receptor agonist. The drug was exposed to standard degradation and the degradation products were primarily resolved and identified by UPLC-ESI-MS. This led to the identification of five forced degradation products (FDP). Thirty-three other known related substances (RS) of ELT, identified in the literature, were also considered. Molecular similarity checks were performed using Tanimoto similarity searches. A set of structurally and topologically similar molecules, including ELT and 15 RS, was established and subjected to in-silico toxicity-, absorption-, distribution-, metabolism-, and elimination (ADME) predictions. The RS, predicted with similar or lower toxicity than ELT and a comparable ADME profile, were subjected to molecular docking to trace changes in TPO receptor affinity. The results indicated that five RS had a high Jaccard’s similarity with ELT and higher or comparable docking scores. These compounds, along with few other impurities were predicted to have lower toxicity, better or comparable absorption, distribution, metabolism, and a better excretion profile than ELT. This justifies their entry as potential novel TPO receptor agonists in drug discovery.

Analysis of Molecular Testing for Suspected Myeloproliferative Neoplasm at a Hybrid Community-Academic Health System

Testing for somatic mutations in JAK2, MPL, and CALR genes is a crucial element in the diagnosis of myeloproliferative neoplasms (MPN). This may have inadvertently led to increased requests for testing to “rule out MPN,” including clinical situations with low pre-test probability. This paper examines JAK2, MPL, and CALR testing by next generation sequencing (NGS) with the goal of formulating practical guidelines to make test utilization more efficient and effective. NGS results from 1482 patients tested between 2015 and March 2022 were retrieved, along with corresponding bone marrow biopsies and CBC results performed within 90 days prior to NGS and 245 (16.5%) cases were positive for pathogenic variants in JAK2, MPL, or CALR genes.The findings showed an increase in the proportion of positive cases with patient age, and a statistically significant difference in RBC counts and platelet counts among patients with positive versus negative results. Utilizing these factors, simple algorithms were constructed to predict positive results with a maximum sensitivity of 91%, while potentially eliminating 28% of negative tests. However, these models still failed to identify ∼9% of patients with MPNs. Among these “missed” patients, many had either primary myelofibrosis or MDS/MPN. Considering a simple triage model to help guide MPN testing could represent a more cost effective approach, particularly if “missed” patients could be further reduced.

Long term follow-up of the STOPAGO study

In an open prospective, multicenter study that enrolled 48 selected patients with chronic immune thrombocytopenia who achieved complete response for 1 year on thrombopoietin receptor agonists, half of the patients maintained a sustained response off treatment 4 years after treatment discontinuation. NCT03119974

Predictors for spontaneous remission in childhood chronic immune thrombocytopenia.

This study examined the factors associated with spontaneous remission in children with chronic immune thrombocytopenia (ITP). We retrospectively analyzed the medical records of patients diagnosed with ITP from January 1988 to December 2019 at our institute. A total of 104 children with chronic ITP were identified. The median follow-up time from diagnosis of chronic ITP was 3.6 years (IQR 1.2-8.3, range 0.1-31.4). Fifteen (14.4%) patients with severe symptoms received specific platelet-elevating therapies, including splenectomy, rituximab, and thrombopoietin receptor agonists. Seven of them achieved remission. Among the patients with a platelet count < 30 × 109/L at the time of diagnosis of chronic ITP, those who received specific platelet-elevating therapies had a higher remission rate compared to those who did not (HR: 4.66, 95% CI: 1.36-16.0). Sixteen patients (15.4%) developed systemic lupus erythematosus, 46 (44.2%) still had thrombocytopenia after a median follow-up of 6.8 years, and 42 (40.4%) achieved remission with a median time to remission of 2.0 years (IQR 0.6-4.1, range 0.1-15.7). The two independent predictive factors for spontaneous remission in childhood chronic ITP were platelet counts > 30 × 109/L at the time of diagnosis of chronic ITP (HR: 3.16, 95% CI: 1.51-6.62) and persistently negative ANA at follow-up (HR: 6.12, 95% CI: 1.46-25.7). The cumulative probabilities of spontaneous remission at 10 years post-diagnosis of chronic ITP were 72.2% for patients without risk factor compared to 0% for patients with two risk factors.

New approaches to standard of care in early-phase myeloproliferative neoplasms: can interferon-α alter the natural history of the disease?

The classical BCR::ABL-negative myeloproliferative neoplasms (MPN) include Polycythemia Vera (PV), Essential Thrombocytemia (ET), and Primary Myelofibrosis (PMF). They are acquired clonal disorders of the hematopoietic stem cells (HSC) leading to hyperplasia of one or several myeloid lineages. MPN are caused by three main recurrent mutations, JAK2V617F and mutations in the calreticulin (CALR) and the thrombopoietin receptor (MPL) genes. Here, we review the general diagnosis, the complications, and the management of MPN. Second, we explain the physiopathology of the natural disease development and its regulation, which contributes to MPN heterogeneity. Thirdly, we describe the new paradigm of the MPN development highlighting the early origin of driver mutations decades before the onset of symptoms and the consequence on early detection of MPN cases in the general population for early diagnosis and better medical management. Finally, we present the interferon alpha (IFNα) therapy as a potential early disease-modifying drug after reporting its good hematological and molecular efficacies in ET, PV and early MF in clinical trials as well as its mechanism of action in pre-clinical studies. As a result, we may expect that, in the future, MPN patients will be diagnosed very early during the course of disease and that new selective therapies under development, such as IFNα, JAK2V617F inhibitors and CALRmut monoclonal antibodies, would be able to intercept the mutated clones.

Avatrombopag for the treatment of patients with chemotherapy-induced thrombocytopenia: A case series.

Management of chemotherapy-induced thrombocytopenia (CIT) is challenging, often resulting in chemotherapy treatment delays, dose reduction, and treatment interruption. Randomized trials support the potential efficacy and safety of thrombopoietin receptor agonists in CIT management. A phase III trial of avatrombopag (AVA) demonstrated increased platelet counts (PC) in patients with solid tumours experiencing CIT. To complement those findings, this case series of six patients with solid tumours and CIT is presented. Results from these cases support the clinical benefit of AVA in improving PC and reducing the impact of CIT on tumour treatment, allowing continued therapy without dose reduction or treatment interruption.

Clinical research progress of lusutrombopag for the treatment of thrombocytopenia in chronic liver disease

Thrombocytopenia is one of the common complications with the hematologic system in patients with chronic liver disease, which often causes poor quality of life and high risk of bleeding, thereby affecting their diagnosis, treatment, and prognosis. Platelet transfusion can improve the patient's declining platelet count to a certain extent, but it has problems such as high price and being easy to cause immune rejection. Thrombopoietin (TPO), as an important cytokine that affects platelet production, can bind to TPO receptors and activate megakaryocytes to produce platelets. Lusutrombopag is a newly developed small-molecule TPO receptor agonist that can induce bone marrow progenitor cells to differentiate into megakaryocytes and increase platelet production, posing characteristics of oral convenience, safety and effectiveness; thus, it has been used in many countries and regions for the treatment of patients with chronic liver diseases concurrent with thrombocytopenia. Herein, the pharmacological features and clinical research are reviewed.

Thromboembolism adverse event profiles of thrombopoietin receptor agonists: a real-world, pharmacovigilance study

ABSTRACT Background Thrombopoietin receptor agonists (TPO-RAs) are currently approved for the treatment of thrombocytopenia in different conditions. The relationship between TPO-RAs and thromboembolic events (TEEs) remains controversial. Research design and methods We extracted TPO-RAs adverse reaction reports after their marketing until now, using the FDA adverse event reporting system (FAERS). Positive signals were detected by reporting odds ratios (RORs). And the Weibull shape parameter test was utilized to analyze the time-to-onset profiles. Result Thromboembolic events accounted for 8.97% among TPO-RAs reports. Increased reporting of TEEs was related to TPO-RAs treatment compared with the entire FAERS database [ROR = 2.65 (2.56, 2.73)]. In addition, venous thrombotic events [ROR = 4.13 (3.92, 4.35)] were reported more frequently than arterial events ROR = 1.81 (1.7, 1.93)]. Age over 60 years [odds ratio (OR) = 1.10 (1.01, 1.20), p = 0.029] and weight over 80 kg [OR = 1.36 (1.17, 1.58), p < 0.001] of patients might have higher risk of TEEs during TPO-RAs therapy. Conclusion Evidence from the real world suggested that TPO-RAs were associated with higher incidence of TEEs, particularly venous thrombosis. The risk of TPO-RAs-associated TEEs mostly happened in the early stages of treatment and decreased over time.

Possibilities for diagnosing essential thrombocythemia at the stage of primary health care

This clinical case presents a 39-year-old woman diagnosed with essential thrombocythemia, accompanied by a review of the epidemiology, clinical and diagnostic criteria, and patient management strategies. The case also includes a discussion of potential complications and prognosis associated with the condition. The importance of thorough outpatient monitoring is emphasized, which should include regular assessments of clinical symptoms, changes in blood count parameters, bone marrow trephine biopsy, and molecular genetic testing for MPL and CALR gene mutations. The report highlights gaps in the current medical examination process, suggesting that addressing these deficiencies could improve early detection of essential thrombocythemia and enable timely pathogenetic therapy with antiplatelet agents to prevent complications.

The Establishment of a Novel Murine Model of Immune Thrombocytopenia in Pregnancy and the Impacts of Thrombopoietin Receptor Agonist on Platelet Production.

Objective Immune thrombocytopenia (ITP) is frequently associated with pregnancy. However, treatment options for ITP in pregnancy are limited, and there are few animal models available for the establishment of treatments. Here, we aimed to establish a novel murine pregnant model of ITP and to investigate the impacts of thrombopoietin receptor agonist (TPO-RA) on platelet production and reproductive outcomes. Methods Anti-glycoprotein Ib-alpha (GPIbα) antibody, which binds to megakaryocytes and platelets, was subcutaneously administered to pregnant mice in order to develop an ITP model (ITP group). TPO-RA was given in doses of 1 µg/kg, 10 µg/kg, and 100 µg/kg (low-dose group, mid-dose group, and high-dose group, respectively) for the treatment of ITP in pregnancy. Results The ITP group showed a significant reduction of platelet counts of less than 15% of healthy pregnant mice (control group) and also showed a significant increase in miscarriage rate (control group, 3.8%; ITP group, 44.4%; p < 0.05). Striking increases in platelet counts were observed in every TPO-RA group without any negative effects on fetal growth and placental pathology. No abnormality was noted in the external examination of fetal mice. Interestingly, a significant recovery of miscarriage rate was observed in the mid-dose group (23.5%) compared with the ITP group (p < 0.05). Conclusion A novel ITP model in pregnant mice was induced by injection of an anti-GPIbα antibody, and sufficient effects of TPO-RA on platelet production were observed in the present study. Furthermore, the positive impacts of TPO-RA on reproductive outcomes were revealed in the ITP model.

Avatrombopag in immune thrombocytopenia: A real-world study of the Spanish ITP Group (GEPTI).

Avatrombopag is the newest thrombopoietin receptor agonist (TPO-RA) approved to treat immune thrombocytopenia (ITP). Real-world evidence regarding effectiveness/safety is limited. The Spanish ITP Group (GEPTI) performed a retrospective study with patients starting avatrombopag for the first time. A total of 268 ITP patients were recruited. The median (interquartile range [IQR]) follow-up time was 47.5 (30.4-58.9) weeks. Among the 193 patients with baseline platelet counts <50 × 109/L, 174 (90.1%) of them achieved response (PC ≥50 × 109/L), and 113 (87.6%) of the 129 who persisted on avatrombopag at last visit had platelet levels above such threshold. Results were similar when only those patients switching to avatrombopag due to previous treatment failure were considered (n = 104). Patients reached response in 13 (7-21) days. Among patients with baseline levels ≥50 × 109/L, 73/75 (97.3%) reported response, which was maintained by 53 (94.6%) of the 56 who continued on avatrombopag at the end of the study. Loss-of-response was always <10%. ITP duration did not influence response. Approximately 79% (34/43) of heavily pretreated (≥4 lines) patients with baseline platelet counts <50 × 109/L switching after previous failure achieved PC ≥50 × 109/L. Previous use of eltrombopag and/or romiplostim did not influence response, regardless of whether previous TPO-RA(s) succeeded or failed. Avatrombopag allowed dose-reduction/suspension of corticosteroids in 40/50 (80.0%) patients with baseline platelet counts <50 × 109/L. Overall, 40/268 (14.9%) thrombocytosis and 12/268 (4.5%) thromboembolic events were reported. Our real-world cohort supports the use of avatrombopag to manage ITP, regardless of disease severity and treatment history.

6601 A Case of Recurrent Painless Thyroiditis and Discussion of Management

Abstract Disclosure: M.C. Slack: None. S. Grock: None. Introduction: Painless (silent) thyroiditis is characterized as a subacute and generally self-limited disease process in which patients develop transient thyrotoxicosis, which is often followed by a hypothyroid phase before entering the recovery euthyroid phase. Given high frequency of positive thyroid antibodies, it may be autoimmune-mediated; recurrence is rare. Here we present a case of recurrent painless thyroiditis and discuss management options. Clinical Case: A Korean woman was followed by endocrinology from age 38 to 60 and experienced at least seven episodes of painless thyroiditis over this time. The episodes occurred without an identifiable trigger and were not preceded by viral illness. During episodes she developed palpitations, hair loss, and dyspnea on exertion and biochemical evidence of thyrotoxicosis with TSH suppressed to &amp;lt;0.2 mIU/mL (normal 0.3-4.7) and elevated free T4 levels as high as 5.4 ng/dL (normal 0.8-1.7). TSI, TPO, and TSH receptor antibodies were checked during multiple episodes and resulted negative, though thyroglobulin antibody was significantly elevated. A radioactive iodine uptake scan was obtained during an active episode of thyroiditis and revealed diffusely low uptake. The patient’s episodes lasted approximately two to three months before normalization of her TSH and FT4. She had at least one instance of transient hypothyroidism after thyrotoxicosis with a TSH of 13.2 and FT4 of 0.6 which subsequently normalized 6 weeks later. The patient did not have known cardiovascular disease and DXA scans revealed mild osteopenia with the lowest T-score -1.3. RAI was considered for the patient based on the total number and increasing frequency of her episodes. She ultimately declined treatment with RAI and continues to follow with endocrinology. Clinical Lessons: While the deleterious effects of prolonged hyperthyroidism (e.g. osteoporosis, arrhythmia, cardiovascular disease) are well known, it is unclear what risk recurrent painless thyroiditis episodes pose. As there are no guidelines regarding treatment, clinical gestalt incorporating frequency and duration of episodes, as well as symptoms, is often used to determine if definitive management is indicated. There are case reports in the literature of treatment of recurrent thyroiditis with RAI ablation performed during a euthyroid state, which eliminated recurrence of episodes but did lead to permanent hypothyroidism necessitating hormone replacement. Surgical thyroidectomy may also be considered in select patients. This case highlights the challenges in treating rare cases of recurrent painless thyroiditis given the lack of research or established guidelines. It is reasonable to consider the frequency, severity, and total number of episodes, as well as patient risk factors, symptoms, and preferences when making recommendations regarding management. Presentation: 6/1/2024

Real-world evidence of avatrombopag for the treatment of immune thrombocytopenia intolerant or ineffective to eltrombopag/hetrombopag.

Due to the limited real-world research on the application of avatrombopag (AVA) for immune thrombocytopenia (ITP) in China, we evaluated the effectiveness and safety of AVA in clinical practice. We included 121 adult ITP patients treated with AVA across three medical centres. Based on the reasons for choosing AVA, these patients were divided into eltrombopag (ELT)/hetrombopag (HET) intolerance group (IG), and ELT/HET unresponsive group (UG). Compared with UG, more patients in IG had a history of liver disease and received fewer treatments before AVA. Amongst all patients, 83% had platelet response (≥30 × 109/L) after AVA and 62% achieved complete response (≥100 × 109/L, CR). Sixty-two percent in IG and 56% in UG were able to discontinue more than one concomitant ITP medication. A total of 17 patients underwent multiple switches of thrombopoietin receptor agonists (TPO-RAs), resulting in an 88% platelet response rate. Sixty-three patients discontinued AVA, 27% were due to unaffordability. AVA was well tolerated in most patients. In the ITP population, AVA proved effective and safe, particularly in patients intolerant or unresponsive to ELT/HET. Patients benefited from TPO-RAs switches, particularly those undergoing multiple switches. However, many patients struggled with the long-term financial burden of AVA.

Efficacy and safety of TPO receptor agonists in treatment of ITP associated with predominantly antibody deficiencies

AbstractPredominantly antibody deficiencies have an estimated prevalence of >1 in 25 000. Their classical phenotype entails the association of autoimmune manifestations with increased susceptibility to infections. Up to 8% of these patients ultimately develop immune thrombocytopenic purpura (ITP). Reducing the risk for infections and considering nonimmunosuppressive treatments, such as thrombopoietin receptor agonists (TPO-RAs), are important considerations for these patients. This nationwide retrospective case series assessed the outcomes and safety of TPO-RAs as treatment for ITP in adults diagnosed with predominantly antibody deficiencies. Response and complete response to treatment were defined as platelet count reaching 30 × 109/L and 100 × 109/L, respectively. We analyzed data from 28 patients. The median follow-up time after introduction of the first TPO-RAs was 33 months (range, 2 weeks to 10.6 years). After 6 weeks of follow-up, response was achieved in 24 of the 28 patients (85.7%), and among those, 21 patients (75%) displayed a complete response. At the last available follow-up visit, only 7 patients (25%) needed second-line therapies for ITP, and among those, only 5 patients (17.9%) received immunosuppressants. Only 3 patients (10.7%) reported laboratory-confirmed hepatobiliary adverse events of light or mild severity and 3 patients (10.7%) reported thrombotic events. In conclusion, TPO-RAs seemed to be an effective and safe option of treatment in these case series. Our results suggest that eltrombopag or romiplostim should be considered as second-line therapy for ITP related to predominantly antibody deficiencies.

Research Advances in the Treatment of Eltrombopag for Adult Patients with Primary Immune Thrombocytopenia--Review

Primary immune thrombocytopenia (ITP) is an autoimmune disease characterized by thrombocytopenia, and T cell immune dysfunction plays an important role in the formation of ITP. As a thrombopoietin receptor agonist (TPO- RA), eltrombopag can not only directly stimulate megakaryocytes to produce platelets, but also play an immunomodulatory role by inducing regulatory T cell generation and reducing proinflammatory factors. As a second-line treatment drug for adult ITP, eltrombopag is increasingly widely used in clinical practice. This review summarized the latest research progress on the mechanism of action, efficacy, safety, and how to reduce the dosage of eltrombopag in ITP.

Effects of Down-Regulation of PAK1 on Differentiation and Apoptosis of MPN Cells with MPLW515L Gene Mutation and Survival of 6133/MPL Mice

To investigate the effects of down-regulation of p21 activated kinase 1 (PAK1) on the proliferation, differentiation, and apoptosis of myeloproliferative neoplasm (MPN) cells (6133/MPL) with thrombopoietin receptor MPL mutation at codon 515 (MPLW515L) and survival of 6133/MPL mice. Interference with the protein level of PAK1 in 6133/MPL cells was assessed using lentivirus-mediated shRNA transfection technology. CCK-8 assay was used to detect the effect of down-regulation of PAK1 on the proliferation viability of 6133/MPL cells, and colony-forming ability was measured by cell counting. Flow cytometry was used to detect the PAK1 kinase activity on the ability of polyploid DNA formation and cell apoptosis in 6133/MPL cells. The expression of cyclin D1, cyclin D3 and apoptosis-related protein Bax was detected by Western blot. The infiltration of tumor cells in spleen and bone marrow of 6133/MPL mice were detected by HE staining. Down-regulation of PAK1 inhibited the proliferation and reduced the ability of cell colony formation of 6133/MPL cells. After knocking down PAK1, the content of polyploid DNA in 6133/MPL cells increased from 31.8 to 57.5% and 48.0%, and the proportion of apoptosis increased approximately to 10.8%. Down-regulation of PAK1 led to a reduction of infiltration of tumor cells in liver and bone marrow of 6133/MPL mice, thereby prolonging survival time. Down-regulation of PAK1 can significantly inhibit the growth of 6133/MPL cells, promote the formation of polyploid DNA, induce 6133/MPL cell apoptosis, and prolong the survival time of 6133/MPL mice.