Thrombopoietin receptor agonists: ten years later

Switching from eltrombopag to hetrombopag in patients with primary immune thrombocytopenia: a post-hoc analysis of a multicenter, randomized phase III trial

While studies have explored the feasibility of switching between various thrombopoietin receptor agonists in treating immune thrombocytopenia (ITP), data on the switching from eltrombopag to hetrombopag remains scarce. This post-hoc analysis of a phase III hetrombopag trial aimed to assess the outcomes of ITP patients who switched from eltrombopag to hetrombopag. In the original phase III trial, patients initially randomized to the placebo group were switched to eltrombopag. Those who completed this 14-week eltrombopag were eligible to switch to a 24-week hetrombopag. Treatment response, defined as a platelet count of ≥ 50 × 109/L, and safety were evaluated before and after the switch. Sixty-three patients who completed the 14-week eltrombopag and switched to hetrombopag were included in this post-hoc analysis. Response rates before and after the switch were 66.7% and 88.9%, respectively. Among those with pre-switching platelet counts below 30 × 109/L, eight out of 12 patients (66.7%) responded, while eight out of nine patients (88.9%) with pre-switching platelet counts between 30 × 109/L and 50 × 109/L responded post-switching. Treatment-related adverse events were observed in 50.8% of patients during eltrombopag treatment and 38.1% during hetrombopag treatment. No severe adverse events were noted during hetrombopag treatment. Switching from eltrombopag to hetrombopag in ITP management appears to be effective and well-tolerated. Notably, hetrombopag yielded high response rates, even among patients who had previously shown limited response to eltrombopag. However, these observations need to be confirmed in future trials.

Real-world experience of thrombopoietin receptor agonists in pediatric immune thrombocytopenia: a report from a Chinese tertiary children's hospital

Background

Primary immune thrombocytopenia (ITP) is the most common bleeding disorder in children. There are approximately 20% pediatric ITP patients respond poor to corticosteroids as first-line treatment. Recently thrombopoietin receptor agonists (TPO-RAs) have been used to treat refractory ITP and have achieved certain therapeutic effects. To investigate the efficacy and safety of TPO-RAs in the treatment of pediatric ITP, we conducted this real-world study.

Methods

Fifty-three pediatric patients with ITP who did not respond well to corticosteroids were treated with TPO-RAs. Clinical data, including therapeutic response rate, changes in platelet (PLT) count, and adverse events (AEs) were collected.

Results

Of the 51 evaluable patients, 37 (72.5%) responded to TPO-RAs. Patients aged >4 years had a higher response rate than those aged ≤4 years (81.1% vs. 50.0%, P=0.04). There was no effect of sex, duration of disease, prior therapy, Mycoplasma pneumoniae (MP) immunoglobulin M (IgM) positivity, antinuclear antibody (ANA) positivity, CD4/CD8 ratio or baseline PLT count on the response rate (P>0.05). Other than 10 patients with PLT counts that exceeded the upper limit of normal, AEs were sporadic, including increased aminotransferase levels, cough, headache, and vomiting.

Conclusions

TPO-RAs exhibited good clinical efficacy in pediatric ITP patients who failed to respond to first-line treatment, especially patients aged >4 years, and the side effects were minor.

Treatment of Immune Thrombocytopenia: Contextualization from a Historical Perspective

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

Splenomegaly and Response to Splenectomy in Immune Thrombocytopenia

Background: Immune thrombocytopenia (ITP) is an acquired autoimmune disorder affecting patients of all ages and backgrounds. While current standards favor medical therapy in the frontline setting, splenectomy remains an integral part of treatment in refractory cases. Ideal parameters for patient selection for surgery remain elusive. Methods: Data for 40 adult patients undergoing splenectomy for ITP at a large urban center between 1 January 2010 and 1 July 2021 were collected and analyzed. Results: Most patients underwent uneventful laparoscopic splenectomy (95%). Complete or partial response at the time of last follow-up occurred in most patients (92.5%), with 60.0% requiring no additional medical therapy following surgery. Thrombosis was the predominant adverse event and the leading cause of death for two patients. Age and presence of splenomegaly appear to be associated with response to splenectomy. Conclusions: Splenectomy remains an effective therapy for selected patients with ITP. Predictors of positive response to splenectomy, such as younger age and the presence of splenomegaly, may help inform clinicians during patient selection for therapy. With strict attention paid to postoperative thromboprophylaxis, the diminishing use of splenectomy may not be warranted.

Alternative Dosing of Eltrombopag for the Treatment of Chronic, Steroid-Refractory Immune Thrombocytopenia

Idiopathic thrombocytopenic purpura (ITP) presents challenges in management, particularly in cases refractory to corticosteroids. Thrombopoietin receptor (TPO-R) agonists, such as eltrombopag, offer alternative therapeutic options. We report a case of a 72-year-old South Asian male with steroid-refractory chronic ITP who achieved a favorable response with biweekly eltrombopag dosing. Platelet response was comparable to daily dosing, suggesting the efficacy of less frequent administration schedules. This approach may enhance patient adherence and reduce treatment-related financial burdens. Biweekly eltrombopag dosing presents a promising alternative for chronic ITP management, warranting further investigation.

The thrombopoietin mimetic JNJ-26366821 reduces the late injury and accelerates the onset of liver recovery after acetaminophen-induced liver injury in mice

Acetaminophen (APAP)-induced hepatotoxicity is comprised of an injury and recovery phase. While pharmacological interventions, such as N-acetylcysteine (NAC) and 4-methylpyrazole (4-MP), prevent injury there are no therapeutics that promote recovery. JNJ-26366821 (TPOm) is a novel thrombopoietin mimetic peptide with no sequence homology to endogenous thrombopoietin (TPO). Endogenous thrombopoietin is produced by hepatocytes and the TPO receptor is present on liver sinusoidal endothelial cells in addition to megakaryocytes and platelets, and we hypothesize that TPOm activity at the TPO receptor in the liver provides a beneficial effect following liver injury. Therefore, we evaluated the extent to which TPOm, NAC or 4-MP can provide a protective and regenerative effect in the liver when administered 2 h after an APAP overdose of 300 mg/kg in fasted male C57BL/6J mice. TPOm did not affect protein adducts, oxidant stress, DNA fragmentation and hepatic necrosis up to 12 h after APAP. In contrast, TPOm treatment was beneficial at 24 h, i.e., all injury parameters were reduced by 42-48%. Importantly, TPOm enhanced proliferation by 100% as indicated by PCNA-positive hepatocytes around the area of necrosis. When TPOm treatment was delayed by 6 h, there was no effect on the injury, but a proliferative effect was still evident. In contrast, 4MP and NAC treated at 2 h after APAP significantly attenuated all injury parameters at 24 h but failed to enhance hepatocyte proliferation. Thus, TPOm arrests the progression of liver injury by 24 h after APAP and accelerates the onset of the proliferative response which is essential for liver recovery.

Romiplostim use in immune thrombocytopenia: Experience in Cuenca, Ecuador

Introduction. The international consensus and the American Society of Hematology guidelines from 2019 established thrombopoietin analogues as the second-line therapy for primary immune thrombocytopenia cases. Objectives. To describe romiplostim usefulness in patients with immune thrombocytopenia in a third-level hospital in Cuenca, Ecuador. Materials and methods. We conducted a descriptive and retrospective study in patients with immune thrombocytopenia treated with romiplostim. We evaluated the following variables: age, gender, previous therapies to romiplostim, dose, frequency, complications, change of thrombopoietin analogue, and treatment discontinuation. Results. We included 21 patients with immune thrombocytopenia treated with romiplostim, with a median age of 49 years. All patients received corticosteroids as first-line treatment. Three patients required longer administration intervals (over a week), with weekly doses lower than those recommended (< 1 μg/kg). Due to lack of efficacy, six patients replaced elthrombopag with romiplostim. Of the total, three suffered thrombotic complications: two had portal venous thrombosis, and one had pulmonary thromboembolism; five of the patients discontinued romiplostim scheme without resuming it. Conclusions. Romiplostim constitutes a convenient second-line therapy in immune thrombocytopenia. Despite the small sample size, romiplostim early use can minimize toxicities and infectious risks.

Acute Renal Thrombotic Microangiopathy Caused by Eltrombopag and Romiplostim in a Patient with Myelodysplastic Syndromes (MDS) and Underlying Antiphospholipid Syndrome

Romiplostim and eltrombopag are synthetic agonists of the thrombopoietin receptor (TPO-R), commonly used for immune thrombocytopenic purpura (ITP) and sometimes in myelodysplastic syndrome (MDS). They are rarely associated with kidney injury. We report a case of acute kidney injury caused by romiplostim and eltrombopag in an 80-year-old male patient with MDS and ITP. He did not have systemic haemolysis syndrome but isolated acute renal thrombotic microangiopathy confirmed by kidney biopsy. He was treated with steroids, plasmapheresis and anticoagulation, with improvement in renal function. Interestingly, the patient had high antiphospholipid (aPL) antibodies noted upon screening, indicating a possible new antiphospholipid syndrome (APS) diagnosis. In the presence of circulating aPL antibodies, eltrombopag may have served as a trigger, causing endothelial injury and subsequent renal microangiopathy; aPL antibodies were still significantly positive at four weeks of outpatient testing. This case and a few others reported in the literature highlight the importance of screening for aPL antibodies before initiating TPO-R agonists in patients with ITP. We suspect that using TPO-R agonists, rather than underlying aPL, caused renal failure.

LEARNING POINTS

Synthetic agonists of the thrombopoietin receptor, such as romiplostim or eltrombopag, can cause acute renal failure.Preexisting antiphospholipid (aPL) antibodies may increase the risk of renal failure.Screening for aPL antibodies should be considered before initiating thrombopoietin-receptor agonists (TPO-R agonists) in patients with immune thrombocytopenic purpura (ITP).

Data mining and safety analysis of avatrombopag: a retrospective pharmacovigilance study based on the US food and drug administration's adverse event reporting system

With its increasing use in the treatment of thrombocytopenia, avatrombopag's associated adverse events (AEs) pose a major challenge to its clinical application. This study aims to comprehensively study AEs associated with avatrombopag by using real-world evidence. We curated AE reports for avatrombopag from the first quarter of 2018 to the fourth quarter of 2023 in the US Food and Drug Administration's Adverse Event Reporting System (FAERS) database. AEs were coded using the Medical Dictionary for Regulatory Activities of Preferred Terms and System Organ Classes. The reporting odds ratio, proportional reporting ratio, Bayesian confidence propagation neural network, and multi-item Gamma-Poisson Shrinker were used to investigate the relationship between avatrombopag and AE reports. Among 9,060,312 reported cases in the FAERS database, 1211 reports listed avatrombopag as "primary suspected" drug. Disproportionality analysis identified 44 preferred terms across 17 organ systems met the criteria for at least one of the four algorithms. The most commonly reported AEs were platelet count decreased (20.2%), headache (16.7%), platelet count increased (11.9%), platelet count abnormal (6.3%), contusion (2.7%), pulmonary embolism (2.3%), and deep vein thrombosis (2.1%). Unexpected AEs such as seasonal allergy, rhinorrhea, antiphospholipid syndrome, ear discomfort, and photopsia were also observed. Excluding the other serious outcomes, hospitalization (34.6%) was the most frequently reported serious outcome, followed by death (15.4%). Most reported AEs occurred within the first 2 days of initiating avatrombopag therapy, and the median onset time was 60 days. We identified new and unexpected AEs with clinical use of avatrombopag, and our results may provide valuable information for clinical monitoring and identifying risks associated with avatrombopag.

Treatment patterns and outcomes among adults with immune thrombocytopenia receiving pharmaceutical second-line therapies: a retrospective cohort study using administrative claims data

OBJECTIVES

To describe and compare real-world treatment patterns and clinical outcomes among individuals with immune thrombocytopenia (ITP) receiving second-line therapies (rituximab, romiplostim, or eltrombopag).

METHODS

A retrospective cohort study was conducted using a large administrative claims database (January 2013-May 2020) among continuously enrolled patients ≥18 years prescribed second-line ITP therapies. The index date was the date of the first claim of the study medications. Treatment patterns and outcomes were measured during the 12-month follow-up period. Inverse probability of treatment weighting (IPTW) was used to balance covariates across treatment groups. Multivariable logistic regression was used to compare treatment patterns and bleeding risk outcomes.

RESULTS

A total of 695 patients were included (rituximab, N = 285; romiplostim, N = 212; eltrombopag, N = 198). After IPTW, all baseline covariates were balanced. Compared to eltrombopag, patients in the rituximab cohort were 57% more likely to receive other ITP therapies (systematic corticosteroids or third-line therapies) during the follow-up period (odds ratio [OR] = 1.571, p = .030). There was no significant difference in the odds of receiving a different second-line therapy or experiencing a bleeding-related episode among three groups (p > .050). Patients in the romiplostim cohort were 69% more likely to receive rescue therapy compared to those in the rituximab cohort (OR = 1.688, p = .025).

CONCLUSION

Patients with ITP receiving rituximab were more likely to need other ITP therapies but did not experience higher risk of bleeding compared to those receiving eltrombopag or romiplostim. Benefits, risks, cost-effectiveness, and patient preference should all be considered in optimizing second-line therapy for ITP.

Activating SRC/MAPK signaling via 5-HT1A receptor contributes to the effect of vilazodone on improving thrombocytopenia

Thrombocytopenia caused by long-term radiotherapy and chemotherapy exists in cancer treatment. Previous research demonstrates that 5-Hydroxtrayptamine (5-HT) and its receptors induce the formation of megakaryocytes (MKs) and platelets. However, the relationships between 5-HT1A receptor (5-HTR1A) and MKs is unclear so far. We screened and investigated the mechanism of vilazodone as a 5-HTR1A partial agonist in promoting MK differentiation and evaluated its therapeutic effect in thrombocytopenia. We employed a drug screening model based on machine learning (ML) to screen the megakaryocytopoiesis activity of Vilazodone (VLZ). The effects of VLZ on megakaryocytopoiesis were verified in HEL and Meg-01 cells. Tg (itga2b: eGFP) zebrafish was performed to analyze the alterations in thrombopoiesis. Moreover, we established a thrombocytopenia mice model to investigate how VLZ administration accelerates platelet recovery and function. We carried out network pharmacology, Western blot, and immunofluorescence to demonstrate the potential targets and pathway of VLZ. VLZ has been predicted to have a potential biological action. Meanwhile, VLZ administration promotes MK differentiation and thrombopoiesis in cells and zebrafish models. Progressive experiments showed that VLZ has a potential therapeutic effect on radiation-induced thrombocytopenia in vivo. The network pharmacology and associated mechanism study indicated that SRC and MAPK signaling are both involved in the processes of megakaryopoiesis facilitated by VLZ. Furthermore, the expression of 5-HTR1A during megakaryocyte differentiation is closely related to the activation of SRC and MAPK. Our findings demonstrated that the expression of 5-HTR1A on MK, VLZ could bind to the 5-HTR1A receptor and further regulate the SRC/MAPK signaling pathway to facilitate megakaryocyte differentiation and platelet production, which provides new insights into the alternative therapeutic options for thrombocytopenia.

Risk-based and individualised management of bleeding and thrombotic events in adults with primary immune thrombocytopenia (ITP)

Although bleeding is one of the main symptoms of primary immune thrombocytopenia (ITP), risk factors for bleeding have yet to be fully established. Low platelet count (PC; <20-30 × 109 /L) is generally indicative of increased risk of bleeding. However, PC and bleeding events cannot be fully correlated; many other patient- and disease-related factors are thought to contribute to increased bleeding risk. Furthermore, even though ITP patients have thrombocytopenia and are at increased risk of bleeding, ITP also carries higher risk of thrombotic events. Factors like older age and certain ITP treatments are associated with increased thrombotic risk. Women's health in ITP requires particular attention concerning haemorrhagic and thrombotic complications. Management of bleeding/thrombotic risk, and eventually antithrombotic therapies in ITP patients, should be based on individual risk profiles, using a tailored, patient-centric approach. Currently, evidence-based recommendations and validated tools are lacking to support decision-making and help clinicians weigh risk of bleeding against thrombosis. Moreover, evidence is lacking about optimal PC for achieving haemostasis in invasive procedures settings. Further research is needed to fully define risk factors for each event, enabling development of comprehensive risk stratification approaches. This review discusses risk-based and individualised management of bleeding and thrombosis risk in adults with primary ITP.

Safety and efficacy of eltrombopag in patients with post-CAR T cytopenias

BACKGROUND

While chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment outcomes of relapsed/refractory hematological malignancies, this therapy is associated with post-treatment cytopenias, which can pose a challenge to its safe administration. This study describes the management of post-CAR T cytopenias using the thrombopoietin mimetic eltrombopag.

METHODS

This retrospective analysis included adult patients with lymphoma or myeloma who received CAR T-cell therapy at two academic medical centers. Eltrombopag was initiated for patients who had persistent high-grade leukopenia and/or thrombocytopenia beyond 21 days post-CAR T infusion. Risk factors and outcomes were assessed and compared for patients who did or did not receive eltrombopag.

RESULTS

Among the 185 patients analyzed, a majority (88%) experienced thrombocytopenia or leukopenia at day +30 post-CAR T infusion. A total of 42 patients met the criteria for eltrombopag treatment and initiated therapy. Patients who received eltrombopag were more likely to have pre-existing cytopenias at lymphodepletion, receive bridging therapy, experience an infection, or require intensive care. Recovery from cytopenias occurred within 180 days for a majority (94%) of patients.

CONCLUSIONS

The use of eltrombopag for post-CAR T leukopenia and thrombocytopenia was considered safe without any significant toxicities. The use of eltrombopag for post-CAR T cytopenias might be effective in a high-risk patient population but requires further study.

Thrombopoietin receptor agonist and rituximab combination therapy in patients with refractory primary immune thrombocytopenia

The aim of our study was to evaluate the efficacy of this therapy in patients with refractory primary immune thrombocytopenia. It is crucial to develop alternative treatment methods for this patient group in order to achieve better response. This combination therapy combines two different mechanisms of action, which is promising in terms of targeting pathophysiology of immune thrombocytopenia. We conducted a retrospective study, which included all patients who were diagnosed with refractory primary immune thrombocytopenia and received TPO-RA and rituximab at the General Hematology Department, Copernicus Memorial Hospital in Lodz, Poland. We assessed the response, time to response and treatment-free remission (TFR). After 1 month of treatment, the complete response (CR1, PLT >100 g/l) was achieved in 62.5% patients, and response (R1, PLT >30 g/l) was achieved in 62.5% patients. The median PLT was 175 × 10 9 /l. Within 1 month of treatment, 87.5% of patients achieved TFR. Adequately, after 6 months, CR6 and R6 was 62.5 and 75%. The median PLT was 182 × 10 9 /l. Treatment-free remission 6 months after completion was in 50% of patients. The study group achieved response to treatment, which suggests that combination of TPO-RA and rituximab is effective and relatively well tolerated. Prospective study on larger group of patients is needed to better evaluate the efficiency and safety of this treatment.

Genistin: A Novel Estrogen Analogue Targeting ERβ to Alleviate Thrombocytopenia

Thrombocytopenia, a prevalent hematologic challenge, correlates directly with the mortality of numerous ailments. Current therapeutic avenues for thrombocytopenia are not without limitations. Here, we identify genistin, an estrogen analogue, as a promising candidate for thrombocytopenia intervention, discovered through AI-driven compound library screening. While estrogen's involvement in diverse biological processes is recognized, its role in thrombopoiesis remains underexplored. Our findings elucidate genistin's ability to enhance megakaryocyte differentiation, thereby augmenting platelet formation and production. In vivo assessments further underscore genistin's remedial potential against radiation-induced thrombocytopenia. Mechanistically, genistin's efficacy is attributed to its direct interaction with estrogen receptor β (ERβ), with subsequent activation of both ERK1/2 and the Akt signaling pathways membrane ERβ. Collectively, our study positions genistin as a prospective therapeutic strategy for thrombocytopenia, shedding light on novel interplays between platelet production and ERβ.

Antithrombotic and hemostatic stewardship: Evaluation of romiplostim for treatment of thrombocytopenia at a large academic medical center

Romiplostim is indicated for immune thrombocytopenia (ITP), though is often used off-label for other indications such as chemotherapy-induced thrombocytopenia (CIT) and thrombocytopenia post hematopoietic stem cell transplantation (HSCT). Although romiplostim is FDA approved at a starting dose of 1 mcg/kg, it is often initiated at 2-4 mcg/kg depending on the severity of thrombocytopenia in clinical practice. Given the limited data, but interest in higher doses of romiplostim for indications other than ITP, we aimed to assess our inpatient romiplostim utilization at NYU Langone Health.This was a single-center, retrospective review of 84 adult patients from January 2019 to July 2021. The top three indications were ITP (51, 60.7%), CIT (13, 15.5%), and HSCT (10, 11.9%). The median initial romiplostim dose was 3.8 mcg/kg (range, 0.9-10.8). 51% of patients achieved a platelet count of ≥50 × 109/L by the end of week 1 of therapy. For patients achieving goal platelets by the end of week 1, the median dose of romiplostim was 2.4 mcg/kg (range, 0.9-10.8). There was 1 episode of thrombosis and 1 episode of stroke.We found that higher than FDA-recommended initial doses should be considered to achieve a platelet response. It appears to be safe to initiate romiplostim as higher doses, and to increase doses by greater increments than 1 mcg/kg in order to achieve a platelet response. Future prospective studies are needed to confirm the safety and efficacy of romiplostim in off-label indications and should evaluate clinical outcomes such as bleeding and need for transfusions.

Spotlight on eltrombopag concentration in pediatric immune thrombocytopenia: A single-center observational study in China

Importance

Eltrombopag has been recommended for pediatric immune thrombocytopenia (ITP). Response and adverse drug reactions (ADRs) varied widely between individuals, even at the same dose of eltrombopag. The appropriate eltrombopag concentration in ITP has not been reported.

Objective

This study aims to explore the appropriate eltrombopag concentration in pediatric ITP.

Methods

This was a single-center, prospective cohort study. Children diagnosed with refractory persistent/chronic ITP and platelet count < 30×109/L were treated with eltrombopag and followed up for at least 2 months. Concentration was detected by high-performance liquid chromatography-mass spectrometry at least 2 weeks after eltrombopag. The clinical characteristics-concentration, concentration-response, and concentration-ADRs were analyzed.

Results

A total of 30 patients were enrolled, comprising 13 males and 17 females, with a median age of 72 (45‒94) months. The median dose and concentration were 1.39 (1.09‒1.56) mg/kg and 2.70 (2.25‒4.13) mg/L, respectively. Of the enrolled patients, 14 responded to treatment, whereas 16 did not. Additionally, five experienced adverse drug reactions. No linear correlation was observed between eltrombopag concentration and clinical characteristics. The concentration was lower in the response group than in the nonresponse group, but there was no significant difference (t = 0.755, P = 0.457). Patients who experienced ADRs had a higher concentration than those without ADRs (t = 2.538, P = 0.017). The area under the receiver operating characteristic curve of ADRs was 0.78 (95% confidence interval: 0.56‒1.00). Youden's index identified the cutoff point as 4.33 mg/L, with a sensitivity of 88% and a specificity of 60%. Logistic regression analysis demonstrated that a higher platelet count before eltrombopag predicted a favorable response.

Interpretation

Eltrombopag proves efficacious and well-tolerated for treating pediatric ITP. However, prolonged and high-dose administration may increase the likelihood of ADRs. Thus, examining the appropriate eltrombopag concentration assists in directing individualized management of pediatric ITP.

Thrombopoietin Receptor Agonists and Other Second-Line Therapies for Immune Thrombocytopenia: A Narrative Review With a Focus on Drug Access in Canada

INTRODUCTION

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by low platelet counts and increased risk of bleeding. After corticosteroids with or without intravenous immune globulin (first-line treatment), second-line treatment options include rituximab, splenectomy, thrombopoietin receptor agonists (TPO-RAs), and fostamatinib. In Canada, the choice of second-line therapy is influenced by access to medications. The goals of this narrative review are to 1) summarize the evidence for the use of TPO-RAs and other second-line therapies in ITP and 2) highlight differences in public funding criteria for TPO-RAs across provinces and territories in Canada.

METHODS

We conducted a literature review of second-line therapies for ITP. We solicited information on public funding programs for TPO-RAs in Canada from health care providers, pharmacists, and provincial ministries of health.

RESULTS

Head-to-head trials involving TPO-RAs, rituximab, splenectomy, and fostamatinib are lacking. There is substantial evidence of effect for TPO-RAs in improving platelet count levels, health-related quality of life, bleeding, and fatigue from placebo-controlled trials and observational studies; however, access to TPO-RAs through provincial funding programs in Canada is variable. Splenectomy failure is a prerequisite for the funding of TPO-RAs in Ontario, Manitoba, and Saskatchewan, but not in Alberta or Quebec. Other provinces either do not have access to public funding or funding is provided on a case-by-case basis.

DISCUSSION

TPO-RAs are effective second-line therapies for the treatment of ITP; however, access is variable across Canada, which results in health disparities and poor uptake of international treatment guidelines.

Translating mechanisms into therapeutic strategies for immune thrombocytopenia (ITP): Lessons from clinical trials

Immune thrombocytopenia (ITP) is an autoimmune disorder that causes a significant reduction in peripheral blood platelet count. Fortunately, due to an increased understanding of ITP, there have been significant improvements in the diagnosis and treatment of these patients. Over the past decade, there have been a variety of proven therapeutic options available for ITP patients, including intravenous immunoglobulins (IVIG), Rituximab, corticosteroids, and thrombopoietin receptor agonists (TPO-RAs). Although the effectiveness of current therapies in treating more than two-thirds of patients, still some patients do not respond well to conventional therapies or fail to achieve long-term remission. Recently, a significant advancement has been made in identifying various mechanisms involved in the pathogenesis of ITP, leading to the development of novel treatments targeting these pathways. It seems that new agents that target plasma cells, Bruton tyrosine kinase, FcRn, platelet desialylation, splenic tyrosine kinase, and classical complement pathways are opening new ways to treat ITP. In this study, we reviewed the pathophysiology of ITP and summarized updates in this population's management and treatment options. We also took a closer look at the 315 ongoing trials to investigate their progress status and compare the effectiveness of interventions. May our comprehensive view of ongoing clinical trials serve as a guiding beacon, illuminating the path towards future trials of different drugs in the treatment of ITP patients.

An Innovative Inducer of Platelet Production, Isochlorogenic Acid A, Is Uncovered through the Application of Deep Neural Networks

(1) Background: Radiation-induced thrombocytopenia (RIT) often occurs in cancer patients undergoing radiation therapy, which can result in morbidity and even death. However, a notable deficiency exists in the availability of specific drugs designed for the treatment of RIT. (2) Methods: In our pursuit of new drugs for RIT treatment, we employed three deep learning (DL) algorithms: convolutional neural network (CNN), deep neural network (DNN), and a hybrid neural network that combines the computational characteristics of the two. These algorithms construct computational models that can screen compounds for drug activity by utilizing the distinct physicochemical properties of the molecules. The best model underwent testing using a set of 10 drugs endorsed by the US Food and Drug Administration (FDA) specifically for the treatment of thrombocytopenia. (3) Results: The Hybrid CNN+DNN (HCD) model demonstrated the most effective predictive performance on the test dataset, achieving an accuracy of 98.3% and a precision of 97.0%. Both metrics surpassed the performance of the other models, and the model predicted that seven FDA drugs would exhibit activity. Isochlorogenic acid A, identified through screening the Chinese Pharmacopoeia Natural Product Library, was subsequently subjected to experimental verification. The results indicated a substantial enhancement in the differentiation and maturation of megakaryocytes (MKs), along with a notable increase in platelet production. (4) Conclusions: This underscores the potential therapeutic efficacy of isochlorogenic acid A in addressing RIT.

Current Understanding of Immune Thrombocytopenia: A Review of Pathogenesis and Treatment Options

The management of immune thrombocytopenia (ITP) and the prediction of patient response to therapy still represent a significant and constant challenge in hematology. ITP is a heterogeneous disease with an unpredictable evolution. Although the pathogenesis of ITP is currently better known and its etiology has been extensively studied, up to 75% of adult patients with ITP may develop chronicity, which represents a significant burden on patients' quality of life. A major risk of ITP is bleeding, but knowledge on the exact relationship between the degree of thrombocytopenia and bleeding symptoms, especially at a lower platelet count, is lacking. The actual management of ITP is based on immune suppression (corticosteroids and intravenous immunoglobulins), or the use of thrombopoietin receptor agonists (TPO-RAs), rituximab, or spleen tyrosine kinase (Syk) inhibitors. A better understanding of the underlying pathology has facilitated the development of a number of new targeted therapies (Bruton's tyrosine kinase inhibitors, neonatal Fc receptors, strategies targeting B and plasma cells, strategies targeting T cells, complement inhibitors, and newer TPO-RAs for improving megakaryopoiesis), which seem to be highly effective and well tolerated and result in a significant improvement in patients' quality of life. The disadvantage is that there is a lack of knowledge of the predictive factors of response to treatments, which would help in the development of an optimized treatment algorithm for selected patients.

Systemic immunosuppression depletes peripheral blood regulatory B cells in patients with immune thrombocytopenia

Regulatory B (Breg) cells are potentially implicated in the pathogenesis of immune thrombocytopenia (ITP). We analysed a prospective cohort of newly diagnosed steroid naïve ITP patients enrolled in the multicentre FLIGHT trial and found that the numbers of Bregs in their peripheral blood were similar to healthy controls. In contrast, Breg numbers were significantly reduced in ITP patients treated with systemic immunosuppression (glucocorticoids or mycophenolate mofetil). We also demonstrate that glucocorticoid treatment impairs Breg interleukin-10 production via an indirect T-cell-mediated mechanism.

Association of thrombopoietin-related drugs with thromboembolic events: Mendelian randomization and a real-world study

Background

Studies have shown conflicting results when using thrombopoietin-related drugs (TPORD) for thromboembolic events (TEEs). Our study aimed to explore the correlation between TPORDs and TEEs.

Method

Drug-targeted Mendelian randomization (MR) and multivariate MR (MVMR) analysis were used to explore the causal relationship between TPORDs and TEEs such as venous thromboembolism (VTE), deep vein thrombosis (DVT), pulmonary embolism (PE), myocardial infarction (MI) and ischemic stroke (STR). At the same time, a real-world study was conducted by extracting adverse events (AEs) from the FDA Adverse Event Reporting System database included in AERSMine to further validate our findings.

Outcome

In drug-target MR, TPORDs were associated with VTE (OR = 1.193, 95% confidence interval (CI): 1.001-1.423, p = 0.049], DVT (OR = 1.321, 95% CI: 1.027-1.700, p = 0.030), MI (OR = 1.216, 95% CI: 1.010-1.464, p = 0.039), STR (OR = 1.224, 95% CI: 1.021-1.468, p = 0.029). VTE/DVT/STR remained stable in MVMR (VTE: OR = 1.3, 95% CI: 1.187-1.422, p < 0.001; DVT: OR = 1.465,95% CI:1.285-1.671, p < 0.001; STR: OR = 1.119, 95% CI: 1.018-1.229, p = 0.019) and real-world studies [lower bound of proportional reporting ratio (ROR) greater than 1]. The significance of myocardial infarction disappeared in MVMR (OR = 0.996, 95% CI: 0.894-1.109, p = 0.942) and in real-world studies (lower ROR lower than 1). There was no evidence of a causal relationship between TPORD and PE (OR = 1.244, 95% CI: 0.969-1.597, p = 0.087), but it generated a signal from a real-world study (lower bound of ROR greater than 1).

Conclusion

This study suggests that TPORDs may be associated with an increased risk of TEEs, particularly AEs leading to VTE/DVT/STR. In addition, the relationship between TPORDs and PE/MI is debatable and requires more research.

Knowledge map of thrombopoietin receptor agonists: A bibliometric analysis

Thrombopoietin receptor agonists (TPO-RAs) have been widely used to treat thrombocytopenia, however, a scientometric profile of TPO-RAs research is lacking. Methods: This study uses VOSviewer, CiteSpace, and R software to provide an overview of current research, highlight study hotspots, and predict future research directions of TPO-RAs. Results: One thousand seven hundred and nineteen relevant studies from 1993 to 2022 with 43962 citations were identified from the Web of Science Core Collection. Over three decades, the USA has been leading TPO-RAs publications. Industries and academic institutions have been actively involved in TPO-RAs research, with funding provided by pharmaceutical companies and public funding bodies. The most productive and cited journals are British Journal of Hematology and Blood, respectively. When author keywords were categorised into three clusters, i.e., cluster 1 (immune thrombocytopenic purpura (ITP)), cluster 2 (avatrombopag, lusutrombopag, and thrombocytopenia), and cluster 3 (TPO-RAs for ITP and off-label drug use), ITP was found to be the current research hotspot, while oral TPO-RAs and licensed or unlicensed drug indications of thrombocytopenic diseases require further investigation. Conclusion: This study has generated the knowledge map of TPO-RAs, which provides a dynamic roadmap for future research in this field.

Interleukins in Platelet Biology: Unraveling the Complex Regulatory Network

Interleukins, a diverse family of cytokines produced by various cells, play crucial roles in immune responses, immunoregulation, and a wide range of physiological and pathological processes. In the context of megakaryopoiesis, thrombopoiesis, and platelet function, interleukins have emerged as key regulators, exerting significant influence on the development, maturation, and activity of megakaryocytes (MKs) and platelets. While the therapeutic potential of interleukins in platelet-related diseases has been recognized for decades, their clinical application has been hindered by limitations in basic research and challenges in drug development. Recent advancements in understanding the molecular mechanisms of interleukins and their interactions with MKs and platelets, coupled with breakthroughs in cytokine engineering, have revitalized the field of interleukin-based therapeutics. These breakthroughs have paved the way for the development of more effective and specific interleukin-based therapies for the treatment of platelet disorders. This review provides a comprehensive overview of the effects of interleukins on megakaryopoiesis, thrombopoiesis, and platelet function. It highlights the potential clinical applications of interleukins in regulating megakaryopoiesis and platelet function and discusses the latest bioengineering technologies that could improve the pharmacokinetic properties of interleukins. By synthesizing the current knowledge in this field, this review aims to provide valuable insights for future research into the clinical application of interleukins in platelet-related diseases.

Addressing thrombosis concerns in immune thrombocytopenia: the role of fostamatinib in immune thrombocytopenia management

INTRODUCTION

Immune thrombocytopenia (ITP), a disease that commonly presents with an increased risk of bleeding, can also paradoxically produce an increased risk of thromboembolic events. The risk of thromboembolism can be associated with patient-related factors (e.g. co-morbidities, age and history of thrombosis), disease-related factors (e.g. a greater proportion of younger, more reactive platelets, and the presence of microparticles and pro-inflammatory cytokines) and treatment-related factors (e.g. splenectomy, thrombopoietin receptor agonists, and IVIg).

AREAS COVERED

Aspects of the pathophysiology of ITP and the effects of treatment are discussed with emphasis on individualizing treatment based on the patient's thromboembolic risk, treatment options and preferences.

EXPERT OPINION

An increased understanding of the pathophysiology of ITP has led to the development of new agents such as fostamatinib, a spleen tyrosine kinase inhibitor. Further research into the factors contributing to the risks for bleeding and thromboembolic events can contribute to the development of more specific therapies for ITP and allow greater individualization of therapy based on each patient's medical history and clinical status.

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

Introduction

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

Areas covered

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

Expert opinion

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

Avatrombopag-induced lactic acidosis in a patient with severe thrombocytopenia

A woman in her 60s was admitted for refractory thrombocytopenia, initially presumed to be from immune thrombocytopenia (ITP). She was treated with the thrombopoietin receptor agonist (TPO-RA) avatrombopag, as well as prophylactic ciprofloxacin and fluconazole for neutropenia. She developed an anion gap metabolic acidosis with a significantly elevated lactate level peaking at 7.5 mmol/L. Other causes of lactic acidosis including hypovolaemia, sepsis, ischaemia and diabetic ketoacidosis were ruled out. Avatrombopag was discontinued, with quick resolution of the lactic acidosis. Fluconazole and ciprofloxacin were found to inhibit the metabolism of avatrombopag and were also discontinued. Worsening thrombocytopenia prompted a rechallenge with increased dose avatrombopag and severe lactic acidosis again developed, with subsequent quick resolution after drug discontinuation. We conclude that a dose-dependent lactic acidosis occurred with avatrombopag in this case. While other TPO-RAs including eltrombopag have been associated with lactic acidosis, to our knowledge, this is the first report of avatrombopag-induced lactic acidosis.

Recombinant human thrombopoietin (rhTPO) of different dosing regimens for refractory/relapsed primary immune thrombocytopenia: a multicenter, randomized controlled trial and pharmacokinetics study

Recombinant human TPO (rhTPO) is effective for refractory/relapsed primary immune thrombocytopenia (ITP), but optimal dosing regimen remains elusive. In this multicenter, randomized, controlled trial, a total of 282 adult ITP patients (mean age 47.3 years; 82 men) with a platelet count ≤30 × 10⁹/L or >30 × 10⁹/L with active bleeding randomly received a once daily (QD) subcutaneous injection of 7500 U (n = 64) or 15000 U rhTPO for 14 injections, or 15000 U or 30000 U rhTPO once every other day (QOD) for 7 injections. The primary outcomes included change from baseline in platelet count and total response rate (TRR) on day 14. On day 14, the median increase of platelet count from baseline was the highest in the 15000-U QD group (167.5 × 10⁹/L, interquartile range [IQR] 23.0-295.0 × 10⁹/L), followed by the 30000-U QOD group (57.5 × 10⁹/L, IQR 9.0-190.0 × 10⁹/L) (ANCOVA P < .001; P = .266 with baseline count as a covariate). The TRR on day 14 was also the highest in the 15000-U QD group (63.2%), followed by the 30000-U QOD group (59.7%). The rate of grade 3 and above adverse events did not differ among the four groups. There were no new safety concerns. All 4 regimens are safe and well-tolerated. The 30000-U QOD regimen is practically indistinguishable in efficacy to the 15000-U QD regimen.

Efficacy and safety of QL0911 in adult patients with chronic primary immune thrombocytopenia: A multicenter, randomized, double-blind, placebo-controlled, phase III trial

Objective

QL0911, a recombinant human thrombopoietin mimetic peptide-Fc fusion protein, is a romiplostim (Nplate®) biosimilar used to treat primary immune thrombocytopenia (ITP). This phase III study aimed to assess the efficacy and safety of QL0911 in adult patients with chronic primary ITP over a 24-week treatment period.

Methods

We conducted a double-blind, placebo-controlled, phase III study in patients diagnosed with primary ITP for at least 12 months who had received at least one first-line ITP treatment with no response or recurrence after treatment, or who relapsed after splenectomy at 44 sites in China. Patients were randomly allocated (2:1 ratio) to QL0911 or placebo injection subcutaneously once weekly at an initial dose of 1 μg/kg for 24 weeks. The doses were adjusted to maintain the target platelet counts from 50 × 109/L to 200 × 109/L. Patients and investigators were blinded to the assignment. The primary endpoints were the proportion of patients who achieved a durable platelet response at week 24 (platelet count, ≥ 50 × 109/L during 6 of the last 8 weeks of treatment) and safety. The study was registered at ClinicalTrials.gov (NCT05621330).

Results

Between October 2019 and December 2021, 216 patients were randomly assigned (QL0911,144; placebo,72). A durable platelet response was achieved by significantly more patients in the QL0911 group (61.8%, 95% CI: 53.3-69.8; P < 0.0001) than in the placebo group (0%). The mean duration of platelet responses was 15.9 (SE: 0.43) weeks with QL0911, and 1.9 (SE:0.26) week with placebo. Consistent results were achieved in subgroup analyses categorized by baseline splenectomy status (yes/no), concomitant ITP treatment (yes/no), and baseline platelet count (≤ 10 × 109/L, > 10 × 109/L, ≤ 20 × 109/L, > 20 × 109/L, and < 30 × 109/L). The incidence of TEAEs was comparable between the QL0911 and the placebo groups (91.7% and 88.9%, respectively). The most common adverse events overall were ecchymosis (28.5% for QL0911 vs. 37.5% for placebo), upper respiratory tract infections respiratory tract infections (31.9% for QL0911 vs. 27.8% for placebo), and gingival bleeding (17.4% for QL0911 vs. 26.4% for placebo).

Conclusion

QL0911 was well-tolerated and increased and maintained platelet counts in adults with ITP. QL0911, a biosimilar to romiplostim (Nplate®), may be a novel treatment option for patients with ITP who have failed or relapsed from first-line treatment in China. Ongoing studies will provide further data on long-term efficacy and safety in such patient populations.

Thrombopoietin level predicts the response to avatrombopag treatment for persistent thrombocytopenia after haploidentical haematopoietic stem cell transplantation

Persistent thrombocytopenia (PT) has an unsatisfactory response to therapy after haploidentical haematopoietic stem cell transplantation (haplo-HSCT). We retrospectively evaluated the safety and efficacy of avatrombopag treatment in 69 patients with PT following haplo-HSCT and assessed whether baseline thrombopoietin (TPO) levels could predict treatment response. Overall response (OR) and complete response (CR) were defined as increased platelet levels to over 20 × 109/L or 50 × 109/L independent of platelet transfusion during or within 7 days of the end of avatrombopag treatment, respectively. The incidences of OR and CR were 72.5% and 58.0%, with a median of 11 and 29 days to OR and CR, respectively. ROC analysis suggested that the optimally discriminant baseline TPO level threshold for both OR and CR to avatrombopag was ≤ 1714 pg/mL. In multivariate analysis, a lower baseline TPO level (P = 0.005) was a significant independent factor of response to avatrombopag. For patients resistant to other TPO receptor agonists (TPO-RAs), 9/16 (56.3%) exhibited a response after switching to avatrombopag. Avatrombopag was well tolerated, and responders achieved improved overall survival (79.0% vs. 91.1%, P = 0.001). In conclusion, avatrombopag is a potential safe and effective treatment for PT after haplo-HSCT, and lower baseline TPO levels predicted a better response.

Romiplostim use for thrombocytopenia following allogeneic hematopoietic stem cell transplantation: a case series from a single center in Qatar

Thrombocytopenia is a common and serious complication that can occur following hematopoietic stem cell transplantation (HSCT), and it contributes to increased morbidity and mortality. The mechanisms of post-HSCT thrombocytopenia are multifactorial and complex. There are no clear consensus and guidelines for managing thrombocytopenia post-HSCT. Recently, there has been promising use of thrombopoietin receptor agonists (TPO-RAs), particularly eltrombopag and romiplostim, as treatments for post-HSCT thrombocytopenia. Notably, that this indication is considered off-label, and data in this use are limited. Based on the existing body of evidence, romiplostim emerges as a safe and effective option for individuals with transfusion-dependent thrombocytopenia after HSCT. In this context, we present a summary of our experience at a single center, where romiplostim was used in the management of post-HSCT thrombocytopenia due to poor graft function. Notably, all four cases responded positively to romiplostim treatment, and no significant adverse events were observed.

Efficacy and safety of thrombopoietin receptor agonists in solid tumors with chemotherapy-induced thrombocytopenia: a meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of thrombopoietin receptor agonists (TPO-RAs) in solid tumors with chemotherapy-induced thrombocytopenia (CIT).

METHODS

We conducted a comprehensive search of PubMed, FMRS, Cochrane Library, Web of Science, EMBASE, and ClinicalTrials.gov for randomized controlled trials (RCTs) reporting the efficacy and safety of TPO-RAs in solid tumors with CIT. The search was limited to articles published before April 30, 2022. Primary outcomes included chemotherapy dose reduction or delays, platelet transfusion, the incidence of grade 3 or 4 thrombocytopenia, and bleeding events. Secondary outcomes encompassed the incidence of platelet count > 400 × 109/L, adverse events (AEs), serious AEs, thrombosis, and mortality.

RESULTS

Our analysis encompassed six studies: five rigorous RCTs and one unique study comparing romiplostim to an observation group, involving a total of 489 patients. For primary outcomes, TPO-RAs significantly reduced the incidence of grade 3 or 4 thrombocytopenia (RR = 0.69, 95% CI: 0.52-0.91). After applying the Bonferroni correction for multiple comparisons, the significance of the reduction in grade 3 or 4 thrombocytopenia incidence persisted (P = 0.008). TPO-RAs showed no significant impact on chemotherapy dose reduction or delays (RR = 0.81, 95% CI: 0.65-1.01), platelet transfusion (RR = 1.04, 95% CI: 0.48-2.27), or bleeding events (RR = 0.50, 95% CI: 0.23-1.10). In terms of safety, there were no significant difference in the incidence of any AEs (RR = 0.98, 95% CI:0.92-1.04), serious AEs (RR = 0.79, 95% CI:0.45-1.40), thrombotic events (RR = 1.20, 95% CI:0.51-2.84) and mortality (RR = 1.15, 95% CI:0.55-2.41).

CONCLUSIONS

This meta-analysis suggests that TPO-RAs are generally well-tolerated. However, their efficacy in solid tumors with CIT appears limited, as they only demonstrate a reduction in the incidence of grade 3 or 4 thrombocytopenia.

Avatrombopag, a promising novel thrombopoietin receptor agonist for refractory/relapsed/intolerant non-severe aplastic anemia: a phase 2 single-arm clinical trial

INTRODUCTION

The therapeutic options for thrombocytopenia in non-severe aplastic anaemia (NSAA) are limited. Avatrombopag (AVA) is prescribed for thrombocytopenic diseases but not for NSAA.

METHODS

Herein, we conducted a phase 2, non-randomized, single-arm trial to explore the efficacy and safety of AVA in refractory/relapsed/intolerant NSAA. AVA dose was initiated at 20 mg/d and titrated to a maximum of 60 mg/d. The primary endpoint was the haematological response at 3 months.

RESULTS

Twenty-five patients were analyzed. The overall response rate (ORR) at 3 months was 56% (14/25), with 12% (3/25) achieving a complete response (CR). At a median follow-up of 7 (3-10) months, the OR and CR rates were 52% and 20%, respectively. Responders had a shorter duration of diagnosis of AVA administration than non-responders (10 (6-80) vs 37 (6-480) months, p = 0.027) and belonged to the relapsed/intolerant NSAA type (71% vs 27%, p = 0.047); 44% (8/18) patients previously treated with eltrombopag before enrollment responded at 3 months, with an average prior eltrombopag dose of median 72.5 (50-100) mg/d and an average AVA dose for a response of median 43.5 (20-60) mg/d. 3-month ORR had no significant correlation with eltrombopag exposure (p = 0.09), prior eltrombopag length (R²=0.11), or cumulative eltrombopag dose (R²=0.30). Only one patient relapsed after stopping AVA for 1 month. No serious AVA-related side effects or clone evolution were detected.

CONCLUSION

AVA is effective and well-tolerated in NSAA patients who are refractory, relapsed, or intolerant to CsA/tacrolimus ± eltrombopag. Earlier treatment and relapsed/intolerant AA may show a better short-term response rate. More studies are needed to define the optimal dose and the long-term efficacy (NCT04728789).

Complement activation negatively affects the platelet response to thrombopoietin receptor agonists in patients with immune thrombocytopenia: a prospective cohort study

Increased platelet destruction is central in the pathogenesis of immune thrombocytopenia. However, impaired platelet production is also relevant and its significance underlies the rationale for treatment with thrombopoietin receptor agonists (TPO-RAs). Previous studies have associated enhanced complement activation with increased disease severity. Additionally, treatment refractoriness has been demonstrated to resolve by the administration of complement-targeted therapeutics in a subset of patients. The association between complement activation and the platelet response to TPO-RA therapy has previously not been investigated. In this study, blood samples from patients with immune thrombocytopenia (n = 15) were prospectively collected before and two, six and 12 weeks after the initiation of TPO-RA therapy. Plasma levels of complement degradation product C4d and soluble terminal complement complexes were assessed. Patients with significantly elevated baseline levels of terminal complement complexes exhibited more often an inadequate platelet response (p = .04), were exclusively subjected to rescue therapy with intravenous immunoglobulin (p = .02), and did not respond with a significant platelet count increase during the study period. C4d showed a significant (p = .01) ability to distinguish samples with significant terminal complement activation, implying engagement of the classical complement pathway. In conclusion, elevated levels of complement biomarkers were associated with a worse TPO-RA treatment response. Larger studies are needed to confirm these results. Biomarkers of complement activation may prove valuable as a prognostic tool to predict which patients that potentially could benefit from complement-inhibiting therapy in the future.

Treatment of immune thrombocytopenia during pregnancy with thrombopoietin receptor agonists

The introduction of thrombopoietin receptor agonists (TPO-RAs) led to a paradigm shift in the management of immune thrombocytopenia (ITP). However, TPO-RAs are not approved for use during pregnancy due to the absence of evidence and concerns for possible effects on the fetus due to their expected transplacental transfer. This comprehensive review examines the safety and efficacy of TPO-RA in 45 pregnancies of women with ITP (romiplostim n = 22; eltrombopag n = 21; both in the same pregnancy n = 2). Mothers experienced failure of the median of three treatment lines during pregnancy prior to TPO-RA administration. A platelet response (>30 × 109 /L) was seen in 86.7% of cases (including a complete response >100 × 109 /L in 66.7%) and was similar between eltrombopag and romiplostim (87.0% and 83.3%, p = 0.99). The maternal safety profile was favourable, with no thromboembolic events encountered. Neonatal thrombocytopenia was noted in one third of cases, with one case of ICH grade 3, and neonatal thrombocytosis was observed in three cases. No other neonatal adverse events attributable to TPO-RAs were seen. This review suggests that the use of TPO-RA during pregnancy is associated with a high response rate and appears safe. Nevertheless, TPO-RA should not be routinely used in pregnancy and should be avoided in the first trimester until further evidence is accumulated.

Patient preferences and experiences regarding thrombopoietin-receptor agonists for immune thrombocytopenia in The Netherlands (TRAPeze Netherlands study)

OBJECTIVE

Identify patient experience and preference towards thrombopoietin-receptor agonists (TPO-RAs) in treatment of immune thrombocytopenia (ITP) in the Netherlands.

METHODS

The Thrombopoietin-Receptor Agonist Patient experience (TRAPeze) survey used a discrete choice experiment (DCE) to elicit patient preferences and a patient burden survey (PBS) to evaluate the clinical and social impact of ITP. TRAPeze collected responses from 6th October to 19th November 2021.

RESULTS

Seventy-six respondents completed the DCE: treatment preference appeared to be driven by method of administration (odds ratio [OR] 4.33; 95% confidence interval [CI] 2.88-6.52), frequency of dosing (OR 2.33; 95% CI 1.86-2.92) and drug-food interactions (OR 1.91; 95% CI 1.54-2.37). Respondents preferred therapies delivered orally over subcutaneous injection (OR 4.22; 95% CI 2.76-6.46), dosed once weekly over once daily (OR 2.37; 95% CI 1.58-3.54) and without food restrictions over with restrictions (OR 1.90; 95% CI 1.52-2.38). Sixty-nine respondents completed the DCE and PBS (mean [range] age 53 [19-83] years, 65% female). Seven incomplete PBS responses were excluded from analysis. Respondents were currently, or most recently, receiving eltrombopag (n = 43) or romiplostim (n = 26), of which 30% (n = 21/69) had previously received another TPO-RA. Loss (29%, n = 6/21) and lack (29%, n = 6/21) of response were the most common reasons for switching TPO-RA. Only 28% (n = 18/65) of respondents felt their TPO-RA increased energy levels.

CONCLUSION

Patients preferred therapies delivered orally, dosed less frequently and without food restrictions. QoL of ITP patients on TPO-RAs can be improved; the burden analyses presented can inform future efforts towards this.

Simultaneous analysis of avatrombopag, eltrombopag, and hetrombopag in human plasma by UPLC-MS/MS for therapeutic drug monitoring

Avatrombopag, eltrombopag, and hetrombopag are three oral thrombopoietin receptor agonists used to treat thrombocytopenia. To investigate the pharmacokinetic properties, a fast and robust UPLC-MS/MS method was developed and validated for simultaneous determination of avatrombopag, eltrombopag, and hetrombopag in human plasma. Chromatographically separation was achieved on an Acquity BEH C18 column using a gradient elution of methanol-water (20:80, v/v) and acetonitrile containing 0.1% formic acid at a flow rate of 0.4 mL/min within 4.5 min. The linearity was assessed over the range of 7.5-1500 ng/mL for avatrombopag, 50-10,000 ng/mL for eltrombopag, and 5-1000 ng/mL for hetrombopag. This method was validated with adequate results in terms of selectivity, precision (intra- and inter-day CV from 4.2% to 12.2%), accuracy (RE from -6.6% to 7.5%), dilution integrity, carryover, recovery, matrix effects, as well as stability of the analytes under various conditions. The developed approach has been successfully applied to the therapeutic drug monitoring of avatrombopag, eltrombopag, and hetrombopag in patients with immune thrombocytopenia.

Immunomodulation with romiplostim as a second-line strategy in primary immune thrombocytopenia: The iROM study

Thrombopoietin receptor agonists (TPO-RAs) stimulate platelet production, which might restore immunological tolerance in primary immune thrombocytopenia (ITP). The iROM study investigated romiplostim's immunomodulatory effects. Thirteen patients (median age, 31 years) who previously received first-line treatment received romiplostim for 22 weeks, followed by monitoring until week 52. In addition to immunological data, secondary end-points included the sustained remission off-treatment (SROT) rate at 1 year, romiplostim dose, platelet count and bleedings. Scheduled discontinuation of romiplostim and SROT were achieved in six patients with newly diagnosed ITP, whereas the remaining seven patients relapsed. Romiplostim dose titration was lower and platelet count response was stronger in patients with SROT than in relapsed patients. In all patients, regulatory T lymphocyte (Treg) counts increased until study completion and the counts were higher in patients with SROT. Interleukin (IL)-4, IL-9 and IL-17F levels decreased significantly in all patients. FOXP3 (Treg), GATA3 (Th2) mRNA expression and transforming growth factor-β levels increased in patients with SROT. Treatment with romiplostim modulates the immune system and possibly influences ITP prognosis. A rapid increase in platelet counts is likely important for inducing immune tolerance. Better outcomes might be achieved at an early stage of autoimmunity, but clinical studies are needed for confirmation.

Early immunomodulation in immune thrombocytopenia-A report of the ICIS meeting in Lenzerheide, Switzerland 2022

The only way to prevent immune thrombocytopenia (ITP) from becoming refractory would be to restore tolerance to platelets at an early phase of the disease. Numerous immune alterations probably accumulate in chronic ITP; thus, the chances of cure decrease significantly with time. Currently, sustained remission off treatment (SROT) is a clinical definition describing patients who can discontinue their ITP treatment without risk and maintain a state of remission. Different treatment strategies are presently being evaluated with the goal of attaining SROT, mostly combining drugs targeting the innate and/or the adaptive immune system, the inflammation state, so as increasing the platelet load. In this sense, thrombopoietin receptor agonists (TPO-RAs) have shown promising results if used as upfront treatment. TPO-RAs seem to exhibit immunomodulation and immune tolerance properties, increasing not only the platelet antigen mass but also increasing the transforming growth factor-β concentration, and stimulating regulatory T and B lymphocytes. However, more immunological studies are needed to establish accurate molecular alterations in ITP that are potentially reversed with treatments.

Markers of refractory primary immune thrombocytopenia

Refractory immune thrombocytopenia (ITP) is a challenging disease that can be defined by refractoriness to second-line treatments. In this review, we list and comment available evidence about clinical and biological factors associated with refractoriness to splenectomy, thrombopoietin receptor agonists (TPO-RAs), rituximab and fostamatinib, as well as those associated with multirefractory ITP (active disease with failure of rituximab, TPO-RAs and splenectomy).

Eltrombopag for Low-Risk Myelodysplastic Syndromes With Thrombocytopenia: Interim Results of a Phase II, Randomized, Placebo-Controlled Clinical Trial (EQOL-MDS)

PURPOSE

In myelodysplastic syndromes (MDS), severe thrombocytopenia is associated with poor prognosis. This multicenter trial presents the second-part long-term efficacy and safety results of eltrombopag in patients with low-risk MDS and severe thrombocytopenia.

METHODS

In this single-blind, randomized, placebo-controlled, phase-II trial of adult patients with International Prognostic Scoring System low- or intermediate-1-risk MDS, patients with a stable platelet (PLT) count (<30 × 103/mm3) received eltrombopag or placebo until disease progression. Primary end points were duration of PLT response (PLT-R; calculated from the time of PLT-R to date of loss of PLT-R, defined as bleeding/PLT count <30 × 103/mm3 or last date in observation) and long-term safety and tolerability. Secondary end points included incidence and severity of bleeding, PLT transfusions, quality of life, leukemia-free survival, progression-free survival, overall survival and pharmacokinetics.

RESULTS

From 2011 to 2021, of 325 patients screened, 169 patients were randomly assigned oral eltrombopag (N = 112) or placebo (N = 57) at a starting dose of 50 mg once daily to maximum of 300 mg. PLT-R, with 25-week follow-up (IQR, 14-68) occurred in 47/111 (42.3%) eltrombopag patients versus 6/54 (11.1%) in placebo (odds ratio, 5.9; 95% CI, 2.3 to 14.9; P < .001). In eltrombopag patients, 12/47 (25.5%) lost the PLT-R, with cumulative thrombocytopenia relapse-free survival at 60 months of 63.6% (95% CI, 46.0 to 81.2). Clinically significant bleeding (WHO bleeding score ≥ 2) occurred less frequently in the eltrombopag arm than in the placebo group (incidence rate ratio, 0.54; 95% CI, 0.38 to 0.75; P = .0002). Although no difference in the frequency of grade 1-2 adverse events (AEs) was observed, a higher proportion of eltrombopag patients experienced grade 3-4 AEs (χ2 = 9.5, P = .002). AML evolution and/or disease progression occurred in 17% (for both) of eltrombopag and placebo patients with no difference in survival times.

CONCLUSION

Eltrombopag was effective and relatively safe in low-risk MDS with severe thrombocytopenia. This trial is registered with ClinicalTrials.gov identifier: NCT02912208 and EU Clinical Trials Register: EudraCT No. 2010-022890-33.

Recent advances in therapies for primary myelofibrosis

Primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET) form the classical BCR-ABL1-negative myeloproliferative neoplasms (MPNs) that are driven by a constitutive activation of JAK2 signaling. PMF as well as secondary MF (post-ET and post-PV MF) are the most aggressive MPNs. Presently, there is no curative treatment, except allogenic hematopoietic stem cell transplantation. JAK inhibitors, essentially ruxolitinib, are the therapy of reference for intermediate and high-risk MF. However, presently the current JAK inhibitors behave mainly as anti-inflammatory drugs, improving general symptoms and spleen size without major impact on disease progression. A better understanding of the genetics of MF, the biology of its leukemic stem cells (LSCs), the mechanisms of fibrosis and of cytopenia and the role of inflammatory cytokines has led to new approaches with the development of numerous therapeutic agents that target epigenetic regulation, telomerase, apoptosis, cell cycle, cytokines and signaling. Furthermore, the use of a new less toxic form of interferon-α has been revived, as it is presently one of the only molecules that targets the mutated clone. These new approaches have different aims: (a) to provide alternative therapy to JAK inhibition; (b) to correct cytopenia; and (c) to inhibit fibrosis development. However, the main important goal is to find new disease modifier treatments, which will profoundly modify the progression of the disease without major toxicity. Presently the most promising approaches consist of the inhibition of telomerase and the combination of JAK2 inhibitors (ruxolitinib) with either a BCL2/BCL-xL or BET inhibitor. Yet, the most straightforward future approaches can be considered to be the development of and/or selective inhibition of JAK2V617F and the targeting MPL and calreticulin mutants by immunotherapy. It can be expected that the therapy of MF will be significantly improved in the coming years.

Phenotypic screening of signaling motifs that efficiently induce cell proliferation

Since cell proliferation is one of the fundamental cell fates, artificial control of cell proliferation based on a receptor-engineering approach is increasingly important in therapeutic and industrial applications. Since the signal transduction properties of cytokine receptors are greatly influenced by the amino acid sequence of tyrosine motifs, here we develop a phenotypic screening approach that can directly select cell proliferation-inducing tyrosine motifs from a synthetic library. In the tyrosine motif library, amino acid sequences around the tyrosine are randomized to attain diverse binding patterns of signaling molecules. Theoretically, engineered receptors with distinct tyrosine motifs would activate signaling molecules in diverse patterns. Thus, we investigated whether tyrosine motif sequences capable of inducing cell proliferation could be selected from the cellular library expressing the motif-engineered receptors. Consequently, the selected motifs induced similar levels of cell proliferation compared to the cytoplasmic signaling domain of a native receptor. The motif-screening system was applicable to cells that may differentiate or proliferate depending on cytokine signals. To our best knowledge, this is the first report demonstrating phenotypic screening of tyrosine motifs in living cells. Our approach would open up new possibilities in the field of artificial control of cell fate based on signal transduction engineering.

Structure of the thrombopoietin-MPL receptor complex is a blueprint for biasing hematopoiesis

Thrombopoietin (THPO or TPO) is an essential cytokine for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Here, we report the 3.4 Å resolution cryoelectron microscopy structure of the extracellular TPO-TPO receptor (TpoR or MPL) signaling complex, revealing the basis for homodimeric MPL activation and providing a structural rationalization for genetic loss-of-function thrombocytopenia mutations. The structure guided the engineering of TPO variants (TPOmod) with a spectrum of signaling activities, from neutral antagonists to partial- and super-agonists. Partial agonist TPOmod decoupled JAK/STAT from ERK/AKT/CREB activation, driving a bias for megakaryopoiesis and platelet production without causing significant HSC expansion in mice and showing superior maintenance of human HSCs in vitro. These data demonstrate the functional uncoupling of the two primary roles of TPO, highlighting the potential utility of TPOmod in hematology research and clinical HSC transplantation.

Eltrombopag in patients with chronic immune thrombocytopenia in Asia-Pacific, the Middle East, and Turkey: final analysis of CITE

CITE was a prospective, noninterventional study in adult patients with chronic immune thrombocytopenia treated with eltrombopag under routine clinical care in Asia-Pacific, the Middle East, and Turkey. Data to assess eltrombopag usage, compliance, and outcomes were collected from May 2017 to December 2020. Platelet response was defined as platelet count ≥50 × 103/μL in the absence of rescue medications and splenectomy. Quality of life was evaluated using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) questionnaire. Noncompliance was defined as the number of missed doses and number of days where the patient did not follow food instructions. A total of 231 patients were enrolled; the median (range) duration of eltrombopag treatment was 484.5 (1-642) days. Compliance to prescribed eltrombopag dose since the previous routine visit was high at ≥96.0%. Baseline median platelet count was 19.0 × 103/μL, which increased to ≥50 × 103/μL at month 2 and mostly fluctuated between 70 × 103/μL and 100 × 103/μL thereafter. The median time to first platelet response was 1.05 (95% confidence interval: 0.92-1.28) months, and the median (interquartile range) maximum duration of platelet response was 193 (57-456) days. FACIT-F scores improved from a mean (standard deviation) 34.4 (12.1) at baseline to 38.5 (9.1) at month 18. Adverse events occurred in 50.9% of patients (n = 116), the most common being upper respiratory tract infection (8.3%) and headache (6.6%). These findings confirmed the effectiveness of eltrombopag treatment in routine practice and reassured that real-world compliance to eltrombopag-prescribed doses and dietary instructions in Asia-Pacific, the Middle East, and Turkey were in line with current recommendations.

[Use of Thrombopoetin-Receptor-Agonists (TPO-RA) in patients with liver cirrhosis before invasive procedures]

Advanced chronic liver disease is accompanied with relevant changes in the corpuscular and plasmatic coagulation system. Due to thrombocytopenia that is regularly observed in these patients, platelet transfusions are often performed prior invasive procedures to prevent possible bleeding complications. However, platelet transfusions are associated with clinically significant adverse events and economically relevant health care costs. Thus, avoiding unnecessary platelet transfusions remains pivotal in daily clinical practice. The first step is to carefully check if increasing platelet counts prior to a planned invasive procedure is really necessary. Nowadays, two well-tolerated thrombopoetin-receptor agonists (TPO-RAs), Avatrombopaq and Lusutrombopaq, to treat thrombocytopenia preemptively before an invasive procedure in patients with liver cirrhosis are available. This review provides a guide for clinician when to increase platelet counts prior an invasive procedure in patients with liver cirrhosis and helps to identify situations in which the use of TPO-RA may be reasonable.

Mitral valve replacement in patients of rheumatic heart disease associated with immune thrombocytopenia

Immune thrombocytopenia in association with rheumatic heart disease is not commonly seen. Surgical management of rheumatic heart disease becomes more challenging in the presence of immune thrombocytopenia. The risk of complications increases manifold and judicious medical management before, during, and after surgery is imperative. We discuss two such cases, the complications we faced and the problems we anticipated before, and their prevention. Both patients were managed without using immunoglobulins or doing splenectomy. The literature on valve replacement in patients of immune thrombocytopenia and the implications of immune thrombocytopenia in the management of patients with rheumatic heart disease is also reviewed.