Long-term fostamatinib treatment of adults with immune thrombocytopenia during the phase 3 clinical trial program

Real-life clinical practice in Spain in the setting of new drug availability for ITP treatment. A Delphi-based Spanish expert panel consensus

Immune thrombocytopenia (ITP) is a common autoimmune hematological disorder. Despite this, diagnosis is still challenging due to clinical heterogeneity and the lack of a specific diagnostic test. New findings in the pathology and the availability of new drugs have led to the development of different guidelines worldwide. In the present study, the Delphi methodology has been used to get a consensus on the management of adult patients with ITP in Spain and to help in decision-making. The Delphi questionnaire has been designed by a scientific ad hoc committee and has been divided into 13 topics, with a total of 127 items, covering the maximum possible scenarios for the management of ITP. As a result of the study, a total consensus of 81% has been reached. It is concluded that this Delphi consensus provides practical recommendations on topics related to diagnosis and management of ITP patients to help doctors to improve outcomes. Some aspects remain unclear, without consensus among the experts. Thus, more advances are needed to optimize ITP management.

2025 update on clinical trials in immune thrombocytopenia

Although the development and regulatory approval of the thrombopoietin receptor agonists revolutionized aspects of the immune thrombocytopenia (ITP) treatment landscape over the past two decades, there remain many areas of high unmet need. Therefore, a number of investigational and repurposed agents are currently undergoing clinical development in ITP. In a departure from historical trials, which largely focused on the indefinite treatment of persistent or chronic ITP, ongoing trials run the gamut of disease phases, and include novel agents being evaluated in early phases of the disease to attempt to modify the disease course. Many agents in development target disease pathophysiologic mechanisms not previously targeted by agents in current use, including platelet autoantibody recycling, B-cell maturation and differentiation, long-lived plasma cells, and the complement system, among others. These agents represent promising treatment options for patients with otherwise refractory disease or who are intolerant of currently available therapies. Additionally, with our increasing understanding of the diverse immune mechanisms at play in ITP, the expansion of the therapeutic armamentarium to include agents targeting diverse pathophysiologic mechanisms may allow a more personalized therapeutic selection in the future. This manuscript provides an up-to-date, in-depth overview of recently completed and ongoing clinical trials in ITP.

Activation of the HMGB1-TLR4 pathway impacts the functionality of bone marrow mesenchymal stem cells and disrupts macrophage polarization in immune thrombocytopenia

Recent evidence suggests that immune thrombocytopenia (ITP), a common bleeding disorder, is linked to an imbalance in macrophage polarization and impaired bone marrow mesenchymal stem cells (BMSCs). However, the relationship between macrophage polarization imbalance and functional defects in BMSCs, as well as the involvement of associated molecules in BMSCs' defects, is not well understood. This study aimed to investigate the regulatory effects of high mobility group protein 1 (HMGB1) on the physiological functions of BMSCs, specifically in relation to macrophage polarization imbalance. Patients with ITP showed dysregulation in monocyte/macrophage polarization and impaired BMSCs function. HMGB1 was found to have a negative impact on the ability of BMSCs to regulate the imbalance in macrophage polarization, especially when inflammatory factors are present. The MyD88-dependent pathway downstream of BMSCs was found to be significantly enhanced with HMGB1 treatment. Furthermore, treatment with toll-like receptor 4 (TLR4) inhibitors successfully restored the regulatory capacity of BMSCs in ameliorating macrophage polarization imbalance and effectively inhibited the activation of the MyD88-dependent pathway. Meanwhile, infusion of si-TLR4-BMSCs reversed HMGB1-induced platelet dysfunction and reduced over-polarization to M1-like macrophages in the ITP mouse model. Consequently, targeting the HMGB1-TLR4 pathway could be a potential approach to restore the immunoregulatory function of BMSCs.

Efficacy and safety of fostamatinib in refractory immune thrombocytopenia: a meta-analysis from randomized controlled trials

BACKGROUND

Immune thrombocytopenia (ITP) is an immune-mediated disease that results in low platelet counts. Despite appropriate treatment, many patients continue to experience refractory disease. Fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, has emerged as a promising option for refractory ITP.

OBJECTIVE

This meta-analysis aims to evaluate the efficacy and safety of fostamatinib compared to conventional therapy in adults aged ≥ 18 years with refractory ITP.

MATERIALS AND METHODS

Literature search was conducted in PubMed, Scopus, Embase, and clinicaltrials.gov databases from inception to March 31, 2024. Randomized controlled trials (RCTs) assessing the safety and efficacy of fostamatinib in adults with refractory ITP were included. Data extraction, risk of bias assessment, and statistical analysis were performed following PRISMA guideline.

RESULTS

A total of 495 articles were screened, with three RCTs meeting the inclusion criteria. Fostamatinib therapy demonstrated superior efficacy in achieving stable platelet response by week 24 (ORR 0.80; 95%CI 0.72-0.88), platelet count ≥ 50,000/µL at weeks 12 (ORR 0.80; 95%CI 0.72-0.90) and week 24 (ORR 0.82; 95%CI 0.72-0.90). Additionally, fostamatinib improves platelet counts in subjects with a baseline count of < 15,000/µL. The Number Needed to Treat (NNT) was calculated as 10. Adverse effects include diarrhea (RR 2.32; 95%CI 1.11-4.84), hypertension (RR 2.33; 95%CI 1.00-5.43), and abnormal liver function tests (RR 4.18; 95% CI 1.00-17.48). Interestingly, the occurrences of nausea (RR 1.77; 95% CI 0.33-9.67) and rash (RR 2.28; 95% CI 0.50-10.29) did not achieve statistical significance.

CONCLUSION

This meta-analysis provides robust evidence supporting the efficacy of fostamatinib in improving platelet counts and achieving therapeutic goals in adults with refractory ITP. However, fostamatinib's safety profile warrants consideration due to higher rates of diarrhea, hypertension, and abnormal liver function tests.

Novel treatments for immune thrombocytopenia: targeting platelet autoantibodies

INTRODUCTION

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by low platelets and an increased risk of bleeding. Platelet autoantibodies target major platelet glycoproteins and cause Fc-mediated platelet destruction in the spleen and reticuloendothelial systems. As mechanisms of disease, platelet autoantibodies are important therapeutic targets. Neonatal Fc receptor (FcRn) antagonists are a new class of therapeutics that reduce the half-life of immunoglobulin G including pathogenic platelet autoantibodies. Spleen tyrosine kinase (Syk) inhibitors interfere with Fc-mediated platelet clearance. Bruton's tyrosine kinase (BTK) inhibitors and B-cell activating factor (BAFF) inhibitors reduce antibody production. The efficacy of these targeted therapies provides new support for the role of platelet autoantibodies in pathogenesis of ITP even these antibodies can be difficult to detect.

AREAS COVERED

This review includes an in-depth exploration of the pathophysiologic mechanisms of ITP, focusing on autoantibodies. Treatments outlined in this review include a) FcRn antagonists, b) complement inhibitors, c) B-cell directed therapies such as BTK inhibitors, and anti-BAFF agents, d) Syk inhibitors, e) plasma-cell directed therapies, and f) novel cellular therapeutic products.

EXPERT OPINION

Platelet autoantibodies are often elusive in ITP, yet novel treatments targeting this pathway reinforce their role in the pathogenesis of this autoimmune platelet disorder.

Real-world clinical outcomes with fostamatinib for the treatment of refractory chronic immune thrombocytopenia: a single-center experience

Fostamatinib is a spleen tyrosine kinase inhibitor indicated for the treatment of chronic immune thrombocytopenia (ITP) unresponsive to a previous treatment. Real-world studies evaluating the utilization and effectiveness of fostamatinib outside the context of a clinical trial are lacking. The objective of this analysis was to evaluate the effectiveness of fostamatinib for the treatment of ITP in a real-world cohort. We conducted a single-center, retrospective, observational study to evaluate the effectiveness of fostamatinib for the treatment of ITP. The primary endpoint was durable response as defined by the American Society of Hematology ITP response criteria. Secondary endpoints included overall response rate, time to response, and safety. Subgroup analysis was performed to assess frequency of durable response in key subgroups of patients based on prior therapies. Thirty-one patients treated with fostamatinib for ITP were included in our analysis. Patients had received a median of four prior lines of therapy. Ten patients (32%) achieved a durable response. Most durable responders maintained their response at 24 months ( n  = 7; 70%). The median time to response was 9 days. Four patients (13%) discontinued fostamatinib due to an adverse event. Subgroups who had higher rates of durable responses included those who had received two to three prior lines of therapy (40%), splenectomized patients (50%), and those who had not received prior rituximab (55%). Fostamatinib therapy in a real-world population of patients with heavily pretreated ITP led to a durable response in a third of patients, which was maintained for most responders.

Fostamatinib effectiveness and safety for immune thrombocytopenia in clinical practice

ABSTRACT

Fostamatinib, a recently approved Syk inhibitor used in adult primary immune thrombocytopenia (ITP), has been shown to be safe and effective in this disorder. However, clinical trial results may not be similarly reproduced in clinical practice. Here, 138 patients with ITP (both primary and secondary) from 42 Spanish centers who had been treated with fostamatinib were evaluated prospectively and retrospectively. The median age of our cohort (55.8% women) was 66 years (interquartile range [IQR], 56-80). The median time since ITP diagnosis at fostamatinib initiation was 51 months (IQR, 10-166). The median number of therapies before fostamatinib initiation was 4 (IQR, 2-5), including eltrombopag (76.1%), romiplostim (57.2%), and IV immunoglobulins (44.2%). Fifty-eight patients (42.0%) had signs/symptoms of bleeding in the month before treatment initiation. Seventy-nine percent of patients responded to fostamatinib with 53.6% complete responses (platelet count > 100 × 109/L). Eighty-three patients (60.1%) received fostamatinib monotherapy, achieving a high response rate (85.4%). The proportion of time in response during the 27-month period examined was 83.3%. The median time to platelet response was 11 days (IQR, 7-21). Sixty-seven patients (48.5%) experienced adverse events, mainly grade 1 to 2; the commonest of which were diarrhea (n = 28) and hypertension (n = 21). One patient had deep venous thrombosis, and one patient developed acute myocardial infarction. Fostamatinib was shown to be effective with good safety profile in patients with primary and secondary ITP across a wide age spectrum in this real-world study.

Fostamatinib for immune thrombocytopenic purpura in adult patients: A systematic review and meta-analysis

Immune thrombocytopenic purpura (ITP) is an immune disorder characterized by thrombocytopenia. Fostamatinib is an orally administered spleen tyrosine kinase inhibitor intended to treat refractory ITP. To evaluate the efficacy and safety of fostamatinib as a subsequent-line therapy for ITP in adults. We searched four electronic databases for primary studies of any design. Primary efficacy outcomes included proportions of patients achieving overall (≥30 × 109 cells/L), partial (≥50 × 109 cells/L), and stable (as defined in original studies) platelet response. Safety outcomes included rescue medication use and other adverse events. We used narrative synthesis and Mantel-Haenszel random effect meta-analysis to summarize results. Our systematic review included 11 studies for analyses (n = 722). Weighted mean proportions of patients achieving overall, partial, and stable responses with fostamatinib treatment were 0.70 [0.62, 0.76], 0.48 [0.36, 0.61], and 0.28 [0.16, 0.44], respectively. Fostamatinib was favored over placebo for partial (relative risk [RR] = 3.04, 95% confidence interval [CI] [1.53, 6.06]) and stable (RR = 6.43, 95% CI [1.58, 26.23]) responses. Patients on fostamatinib required less rescue medication and were more likely to experience hypertension. Fostamatinib is a viable subsequent-line therapy option for refractory ITP. Given the heterogeneous data and large number of small studies, these results should be interpreted cautiously.

Post-marketing safety surveillance of fostamatinib: an observational, pharmacovigilance study leveraging FAERS database

OBJECTIVE

Fostamatinib, an FDA-approved oral small-molecule spleen tyrosine kinase (SYK) inhibitor, is used to treat thrombocytopenia in adults with chronic immune thrombocytopenia (ITP) who have not responded to previous treatments. However, comprehensive safety data is lacking. This study uses the FDA Adverse Event Reporting System (FAERS) database to explore real-world adverse events (AEs) related to fostamatinib, aiming to inform its clinical use.

METHODS

The FAERS database was retrospectively queried to extract reports associated with fostamatinib from 2019 to 2023. To identify and evaluate potential AEs in patients receiving fostamatinib, various disproportionality analyses such as the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multi-item gamma Poisson shrinker (MGPS) were employed.

RESULTS

A total of 23 AE signals were included in our analysis. Among them, hypertension, blood pressure increase, blood pressure abnormality, hepatic enzyme increase, and diarrhea were consistent with the common AEs described for fostamatinib in clinical trials. In addition, unexpected serious AEs were detected including cerebral thrombosis and necrotizing soft tissue infection. The median time to onset of fostamatinib-related AEs was 86 days.

CONCLUSION

Our investigation revealed several possibly emergent safety concerns associated with fostamatinib in real-world clinical practice, which might provide essential vigilance evidence for clinicians and pharmacists to manage the safety issues of fostamatinib.

The 2022 review of the 2019 American Society of Hematology guidelines on immune thrombocytopenia

ABSTRACT

The 2019 American Society of Hematology (ASH) guidelines for immune thrombocytopenia (ITP) included recommendations on the management of adults (recommendations 1-9) and children (recommendations 10-21) with primary ITP . We describe here the results of a review of the 2019 guidelines by a working group of experts requested by ASH to inform decision-making about the need for and timing of a guideline revision. An updated Medline and Embase search applied the same search terms as in the 2019 ASH guidelines, limited to systematic reviews and clinical trials, from May 2017 to July 2022. There were 193 studies identified, 102 underwent abstract reviews, and 54 full reviews. Each study was assessed based on relevance to the previous recommendation with regard to the population, prioritized outcomes, new outcomes, and study design. Reviewers assessed if the data would change the strength or the directionality of the existing recommendation or merit development of a new recommendation. Based on this review, the ASH Committee on Quality endorsed a focused update on second-line management for adults with ITP. In addition, there will be continued annual monitoring and reviewing of the 2019 ASH guidelines on ITP in full to evaluate when there is sufficient new evidence to warrant additional revisions.

Phase I study of the Syk inhibitor sovleplenib in relapsed or refractory mature B-cell tumors

Sovleplenib (HMPL-523) is a selective spleen tyrosine kinase (Syk) inhibitor with anti-tumor activity in preclinical models of B-cell malignancy. We conducted a dose-escalation and dose-expansion phase I study of sovleplenib in patients with relapsed/ refractory mature B-cell tumors. Dose escalation followed a 3+3 design; patients received oral sovleplenib (200-800 mg once daily [q.d.] or 200 mg twice daily [b.i.d.], 28-day cycles). During dose expansion, patients were enrolled into four cohorts per lymphoma classification and treated at the recommended phase II dose (RP2D) (clinicaltrials gov. Identifier: NCT02857998). Overall, 134 Chinese patients were enrolled (dose escalation, N=27; dose expansion, N=107). Five patients experienced dose-limiting toxicities: one each of amylase increased (200 mg q.d.), febrile neutropenia (800 mg q.d.), renal failure (800 mg q.d.), hyperuricemia and blood creatine phosphokinase increased (200 mg b.i.d.) and blood bilirubin increased and pneumonia (200 mg b.i.d.). RP2D was determined as 600 mg (>65 kg) or 400 mg (≤65 kg) q.d.. The primary efficacy end point of independent review committee-assessed objective response rate in indolent B-cell lymphoma was 50.8% (95% confidence interval: 37.5- 64.1) in 59 evaluable patients at RP2D (follicular lymphoma: 60.5%, marginal zone lymphoma: 28.6%, lymphoplasmacytic lymphoma/Waldenström macroglobulinemia, 0%). The most common (≥10% patients) grade ≥3 treatment-related adverse events in the dose-expansion phase were decreased neutrophil count (29.9%), pneumonia (12.1%) and decreased white blood cell count (11.2%). Pharmacokinetic exposures increased dose-proportionally with ascending dose levels from 200-800 mg, without observed saturation. Sovleplenib showed anti-tumor activity in relapsed/refractory B-cell lymphoma with acceptable safety. Further studies are warranted.

Daucosterol regulates JAK2-STAT3 signaling pathway to promote megakaryocyte differentiation

Immune thrombocytopenia (ITP) is an autoimmune disease caused by the loss of immune tolerance to platelet autoantigens, resulting in reduced platelet production and increased platelet destruction. Impaired megakaryocyte differentiation and maturation is a key factor in the pathogenesis and treatment of ITP. Sarcandra glabra, a plant of the Chloranthaceae family, is commonly used in clinical practice to treat ITP, and daucosterol (Dau) is one of its active ingredients. However, whether Dau can treat ITP and the key mechanism of its effect are still unclear. In this study, we found that Dau could effectively promote the differentiation and maturation of megakaryocytes and the formation of polyploidy in the megakaryocyte differentiation disorder model constructed by co-culturing Dami and HS-5 cells. In vivo experiments showed that Dau could not only increase the number of polyploidized megakaryocytes in the ITP rat model, but also promote the recovery of platelet count. In addition, through network pharmacology analysis, we speculated that the JAK2-STAT3 signaling pathway might be involved in the process of Dau promoting megakaryocyte differentiation. Western blot results showed that Dau inhibited the expression of P-JAK2 and P-STAT3. In summary, these results provide a basis for further studying the pharmacological mechanism of Dau in treating ITP.

Treatment with fostamatinib in patients with immune thrombocytopenia: Experience from the Andalusian region in Spain-The Fostasur Study

Immune thrombocytopenia (ITP) is characterized by low platelet counts (PLTs) and an increased risk of bleeding. Fostamatinib, a spleen tyrosine kinase inhibitor, has been approved as a second-line treatment for ITP. Real-world data on fostamatinib are lacking. This observational, retrospective, multicentre study, conducted in the Andalusia region of Spain, evaluated 44 adult primary ITP patients (47.7% female; median age 58 years; newly diagnosed ITP 6.8%; persistent 13.6%; chronic 79.5%; median four prior treatments) after ≥ 4 weeks of fostamatinib therapy. The median PLT at the initiation of fostamatinib was 15 × 109/L. Common reasons for starting fostamatinib were refractoriness or intolerance to prior therapy, oral medication preference, history of thrombosis and cardiovascular risk. Dosing was individualized based on efficacy and tolerance. After 2 weeks, global response rate was 56.8% (response and complete response). Response rates were 70.5%, 62.5% and 64% at 4 weeks, 12 weeks and at the end of the study respectively. Adverse events were mild, and no patients discontinued as a result. This real-world study demonstrated a response rate similar to fostamatinib as seen in the pivotal clinical trials while including newly diagnosed patients and allowing for individualized dosing.

Long-term treatment with rilzabrutinib in patients with immune thrombocytopenia

ABSTRACT

Immune thrombocytopenia (ITP) is an autoimmune disease associated with autoantibody-mediated platelet destruction and impaired platelet production, resulting in thrombocytopenia and a predisposition to bleeding. The ongoing, global phase 1/2 study showed that rilzabrutinib, a Bruton tyrosine kinase inhibitor specifically developed to treat autoimmune disorders, could be an efficacious and well-tolerated treatment for ITP. Clinical activity, durability of response, and safety were evaluated in 16 responding patients who continued rilzabrutinib 400 mg twice daily in the long-term extension (LTE) study. At LTE entry, the median platelet count was 87 × 109/L in all patients, 68 × 109/L in those who had rilzabrutinib monotherapy (n = 5), and 156 × 109/L in patients who received concomitant ITP medication (thrombopoietin-receptor agonists and/or corticosteroids, n = 11). At a median duration of treatment of 478 days (range, 303-764), 11 of 16 patients (69%) continued to receive rilzabrutinib. A platelet count of ≥50 × 109/L was reported in 93% of patients for more than half of their monthly visits. The median percentage of LTE weeks with platelet counts ≥30 × 109/L and ≥50 × 109/L was 100% and 88%, respectively. Five patients discontinued concomitant ITP therapy and maintained median platelet counts of 106 × 109/L at 3 to 6 months after stopping concomitant ITP therapy. Adverse events related to treatment were grade 1 or 2 and transient, with no bleeding, thrombotic, or serious adverse events. With continued rilzabrutinib treatment in the LTE, platelet responses were durable and stable over time with no new safety signals. This trial is registered at www.clinicaltrials.gov as #NCT03395210 and www.clinicaltrialsregister.eu as EudraCT 2017-004012-19.

Identification of miRNAs that target Fcγ receptor-mediated phagocytosis during macrophage activation syndrome

Macrophage activation syndrome (MAS) is a life-threatening complication of systemic juvenile arthritis, accompanied by cytokine storm and hemophagocytosis. In addition, COVID-19-related hyperinflammation shares clinical features of MAS. Mechanisms that activate macrophages in MAS remain unclear. Here, we identify the role of miRNA in increased phagocytosis and interleukin-12 (IL-12) production by macrophages in a murine model of MAS. MAS significantly increased F4/80+ macrophages and phagocytosis in the mouse liver. Gene expression profile revealed the induction of Fcγ receptor-mediated phagocytosis (FGRP) and IL-12 production in the liver. Phagocytosis pathways such as High-affinity IgE receptor is known as Fc epsilon RI -signaling and pattern recognition receptors involved in the recognition of bacteria and viruses and phagosome formation were also significantly upregulated. In MAS, miR-136-5p and miR-501-3p targeted and caused increased expression of Fcgr3, Fcgr4, and Fcgr1 genes in FGRP pathway and consequent increase in phagocytosis by macrophages, whereas miR-129-1-3p and miR-150-3p targeted and induced Il-12. Transcriptome analysis of patients with MAS revealed the upregulation of FGRP and FCGR gene expression. A target analysis of gene expression data from a patient with MAS discovered that miR-136-5p targets FCGR2A and FCGR3A/3B, the human orthologs of mouse Fcgr3 and Fcgr4, and miR-501-3p targets FCGR1A, the human ortholog of mouse Fcgr1. Together, we demonstrate the novel role of miRNAs during MAS pathogenesis, thereby suggesting miRNA mimic-based therapy to control the hyperactivation of macrophages in patients with MAS as well as use overexpression of FCGR genes as a marker for MAS classification.

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.

Fostamatinib for warm antibody autoimmune hemolytic anemia: Phase 3, randomized, double-blind, placebo-controlled, global study (FORWARD)

Warm antibody autoimmune hemolytic anemia (wAIHA) is characterized by hemolysis and symptomatic anemia with no approved treatment options. Fostamatinib is an oral spleen tyrosine kinase inhibitor approved in the US and Europe for treatment of adults with chronic immune thrombocytopenia. In this phase 3 study, patients with an insufficient response to ≥1 prior wAIHA treatment were randomized to fostamatinib or placebo. The primary endpoint was the proportion of patients to achieve a durable hemoglobin (Hgb) response (Hgb ≥10 g/dL and increase from baseline of ≥2 g/dL on 3 consecutive visits) during the 24-week treatment period. Ninety patients were randomized, 45 to each arm. Of the fostamatinib-treated patients, 35.6% achieved a durable Hgb response versus 26.7% on placebo (p = .398). A post hoc analysis revealed a large placebo response in Eastern European patients. Significantly more patients on fostamatinib from North America, Australia and Western Europe exhibited a durable Hgb response compared to placebo (36% vs. 10.7%, p = .030). After censoring for Hgb values impacted by steroid rescue received during screening and excluding 2 placebo patients found to likely not have wAIHA, a reanalysis demonstrated a difference in durable Hgb response between fostamatinib and placebo (15/45 [33.3%] vs. 6/43 [14.0%], p = .0395). At least 1 AE was reported in 42 (93.3%) and 40 (88.9%) patients receiving fostamatinib and placebo, respectively. The most common AEs in the fostamatinib group were diarrhea (26.7%), hypertension (24.4%), and fatigue (15.6%). In this study, fostamatinib demonstrated a clinically meaningful benefit for patients in Western regions, and no new safety signals were identified.

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.

Randomized Trial on the Effect of an Oral Spleen Tyrosine Kinase Inhibitor in the Treatment of IgA Nephropathy

Introduction

We reported increased spleen tyrosine kinase (SYK) expression in kidney biopsies of patients with IgA nephropathy (IgAN) and that inhibition of SYK reduces inflammatory cytokines production from IgA stimulated mesangial cells.

Methods

This study was a double-blind, randomized, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomized to receive placebo, fostamatinib at 100 mg or 150 mg twice daily for 24 weeks on top of maximum tolerated dose of renin-angiotensin system inhibitors. The primary end point was reduction of proteinuria. Secondary end points included change from baseline in estimated glomerular filtration rate (eGFR) and kidney histology.

Results

Although we could not detect significant reduction in proteinuria with fostamatinib overall, in a predetermined subgroup analysis, there was a trend for dose-dependent reduction in median proteinuria (from baseline to 24 weeks by 14%, 27%, and 36% in the placebo, fostamatinib 100 mg, and 150 mg groups, respectively) in patients with baseline urinary protein-to-creatinine ratios (UPCR) more than 1000 mg/g. Kidney function (eGFR) remained stable in all groups. Fostamatinib was well-tolerated. Side effects included diarrhea, hypertension, and increased liver enzymes. Thirty-nine patients underwent repeat biopsy showing reductions in SYK staining associated with therapy at low dose (-1.5 vs. 1.7 SYK+ cells/glomerulus in the placebo group, P < 0.05).

Conclusions

There was a trend toward reduction in proteinuria with fostamatinib in a predefined analysis of high risk patients with IgAN despite maximal care, as defined by baseline UPCR greater than 1000 mg/g. Further study may be warranted.

Rilzabrutinib versus placebo in adults and adolescents with persistent or chronic immune thrombocytopenia: LUNA 3 phase III study

Background

Immune thrombocytopenia (ITP) is characterized by primarily autoantibody-mediated platelet destruction and impaired platelet production resulting in thrombocytopenia and an increased risk of bleeding. Other manifestations include increased risk of thrombosis and diminished quality of life. Current treatment approaches are directed toward lowering the rate of platelet destruction or stimulating platelet production to prevent bleeding. Rilzabrutinib is an oral, reversible, potent Bruton tyrosine kinase inhibitor that was specifically designed to treat immune-mediated diseases and mediates its therapeutic effect through a dual mechanism of action: (1) inhibiting B-cell activation and (2) interrupting antibody-coated cell phagocytosis by Fc gamma receptor in spleen and liver. A 24-week dose-finding phase I/II study of rilzabrutinib in patients with ITP showed a 40% platelet response (⩾2 consecutive platelet counts of ⩾50 × 109/L and increase from baseline ⩾20 × 109/L without rescue medication use) and a well-tolerated safety profile with only grade 1/2 transient adverse events across dose levels.

Objectives

Assess the efficacy and safety of oral rilzabrutinib in adult and adolescent patients with persistent or chronic ITP.

Design

Rilzabrutinib 400 mg BID is being evaluated in the ongoing LUNA 3 multicenter, double-blind, placebo-controlled phase III study.

Methods and analysis

The primary endpoint is durable platelet response, defined as achieving platelet counts of ⩾50 × 109/L for at least two-thirds of ⩾8 available weekly scheduled platelet measurements during the last 12 weeks (including ⩾2 available measurements within the last 6 weeks) of the 24-week blinded treatment period in the absence of rescue therapy.

Ethics

Ethical guidelines and informed consent are followed.

Discussion

The LUNA 3 trial will further investigate rilzabrutinib's safety and efficacy in adult and adolescent patients, with the primary goal of addressing a major objective in treating patients with ITP: durability of platelet response.

Trail Registration

ClinicalTrials.gov NCT04562766: https://clinicaltrials.gov/ct2/show/NCT04562766; EU Clinical Trials Register EudraCT 2020-002063-60: https://www.clinicaltrialsregister.eu/ctr-search/search?query=2020-002063-60.

Recommendations for the Clinical Approach to Immune Thrombocytopenia: Spanish ITP Working Group (GEPTI)

Primary immune thrombocytopenia (ITP) is a complex autoimmune disease whose hallmark is a deregulation of cellular and humoral immunity leading to increased destruction and reduced production of platelets. The heterogeneity of presentation and clinical course hampers personalized approaches for diagnosis and management. In 2021, the Spanish ITP Group (GEPTI) of the Spanish Society of Hematology and Hemotherapy (SEHH) updated a consensus document that had been launched in 2011. The updated guidelines have been the reference for the diagnosis and management of primary ITP in Spain ever since. Nevertheless, the emergence of new tools and strategies makes it advisable to review them again. For this reason, we have updated the main recommendations appropriately. Our aim is to provide a practical tool to facilitate the integral management of all aspects of primary ITP management.

Primary and secondary immune thrombocytopenia (ITP): Time for a rethink

There are not many publications that provide a holistic view of the management of primary and secondary ITP as a whole, reflecting the similarities and differences between the two. Given the lack of major clinical trials, we believe that comprehensive reviews are much needed to guide the diagnosis and treatment of ITP today. Therefore, our review addresses the contemporary diagnosis and treatment of ITP in adult patients. With respect to primary ITP we especially focus on establishing the management of ITP based on the different and successive lines of treatment. Life-threatening situations, "bridge therapy" to surgery or invasive procedures and refractory ITP are also comprehensively reviewed here. Secondary ITP is studied according to its pathogenesis by establishing three major differential groups: Immune Thrombocytopenia due to Central Defects, Immune Thrombocytopenia due to Blocked Differentiation and Immune Thrombocytopenia due to Defective Peripheral Immune Response. Here we provide an up-to-date snapshot of the current diagnosis and treatment of ITP, including a special interest in addressing rare causes of this disease in our daily clinical practice. The target population of this review is adult patients only and the target audience is medical professionals.

Rituximab resistance in ITP and beyond

The pathophysiology of immune thrombocytopenia (ITP) is complex and encompasses innate and adaptive immune responses, as well as megakaryocyte dysfunction. Rituximab is administered in relapsed cases and has the added benefit of inducing treatment-free remission in over 50% of patients. Nevertheless, the responses to this therapy are not long-lasting, and resistance development is frequent. B cells, T cells, and plasma cells play a role in developing resistance. To overcome this resistance, targeting these pathways through splenectomy and novel therapies that target FcγR pathway, FcRn, complement, B cells, plasma cells, and T cells can be useful. This review will summarize the pathogenetic mechanisms implicated in rituximab resistance and examine the potential therapeutic interventions to overcome it. This review will explore the efficacy of established therapies, as well as novel therapeutic approaches and agents currently in development.

Two Refractory Immune Thrombocytopenia Case Reports Showing Responsiveness to Fostamatinib

Immune thrombocytopenia (ITP) is immune-mediated platelet loss due to increased destruction and insufficient production. Treatment guidelines provide for first-line steroid-based therapies followed by thrombopoietin receptor agonists (TPO-RAs) and fostamatinib for chronic ITP. Fostamatinib demonstrated efficacy in phase 3 FIT trials (FIT1 and FIT2) mainly in second-line therapy resulting in the maintenance of stable platelet values. Here, we describe two patients with extremely heterogeneous characteristics that responded to fostamatinib after two and nine previous treatments. Responses were complete with stable platelet counts ≥50,000/μL and without any grade ≥3 adverse reactions. As in the FIT clinical trials, we confirm better responses to fostamatinib when used in the second or third line. However, its use should not be excluded in patients with longer and more complicated drug histories. Given the different mechanism of action of fostamatinib compared to TPO-RAs, it would be interesting to identify predictive factors of responsiveness applicable to all patients.

Spleen tyrosine kinase (SYK) signals are implicated in cardio-cerebrovascular diseases

Post-translational modifications regulate numerous biochemical reactions and functions through covalent attachment to proteins. Phosphorylation, acetylation and ubiquitination account for over 90% of all reported post-translational modifications. As one of the tyrosine protein kinases, spleen tyrosine kinase (SYK) plays crucial roles in many pathophysiological processes and affects the pathogenesis and progression of various diseases. SYK is expressed in tissues outside the hematopoietic system, especially the heart, and is involved in the progression of various cardio-cerebrovascular diseases, such as atherosclerosis, heart failure, diabetic cardiomyopathy, stroke and others. Knowledge on the role of SYK in the progress of cardio-cerebrovascular diseases is accumulating, and many related mechanisms have been discovered and validated. This review summarizes the role of SYK in the progression of various cardio-cerebrovascular diseases, and aims to provide a theoretical basis for future experimental and clinical research targeting SYK as a therapeutic option for these diseases.

Recent progress in ITP treatment

In this review, the recently approved drugs avatrombopag and fostamatinib, which were not extensively covered within 2019 international recommendations for ITP, will be discussed in some detail. Avatrombopag appears more convenient than eltrombopag as it does not require dietary restrictions or subcutaneous administration like romiplostim. However, data on quality of life (QoL) are lacking and the rate of thromboembolic events in exposed patients is not negligible. Efficacy of fostamatinib, an inhibitor of macrophagic activity, is supported by placebo-controlled trials in patients refractory to several therapies, including TPO-RA. While hypertension and diarrhea have been reported, only one minor thrombotic event occurred in 146 exposed patients. In addition, several new treatment combinations and new agents entered clinical investigation in recent years. In a UK trial, combining mycophenolate mofetil with corticosteroids as first line therapy was more effective than corticosteroids alone, but at the cost of worse QoL. No combination, including oseltamivir or all-trans retinoic acid or danazol, resulted in convincing evidence of superior efficacy and safety when used in first or later lines of treatment. Agents targeting specific mechanisms are also discussed: sutimlimab (complement inhibitor); rilzabrutinib (BTK inhibitor) and efgartigimod (modified Fc fragment inhibiting FcRn). Only efgartigimod has completed phase 3 investigation.

Fostamatinib for the treatment of Japanese patients with primary immune thrombocytopenia: A phase 3, placebo-controlled, double-blind, parallel-group study

Fostamatinib, a spleen tyrosine kinase inhibitor, has been approved for the treatment of chronic primary immune thrombocytopenia (ITP) in the United States, Canada and some European countries. We conducted a phase 3, placebo-controlled, double-blind, parallel-group study to evaluate the efficacy and safety of fostamatinib in Japanese patients with primary ITP. Thirty-four patients were randomised to fostamatinib (n = 22) or placebo (n = 12) at 100-150 mg twice a day for 24 weeks. Stable responses (platelet ≥50 000/μl at ≥4 of the 6 visits from weeks 14 to 24) were observed in eight (36%) patients on fostamatinib and in none of the patients on placebo (p = 0.030). Overall responses (platelet ≥50 000/μl at ≥1 of the 6 visits from weeks 2 to 12) were seen in 10 (45%) patients on fostamatinib and in none of the patients on placebo (p = 0.006). Patients on fostamatinib required rescue medication less often and experienced fewer bleeding symptoms than patients on placebo. Adverse events observed were mild or moderate and were manageable. No new safety signals were identified in Japanese patients with ITP.

Use and positioning of fostamatinib in the management of primary chronic immune thrombocytopenia: an Italian expert opinion

Fostamatinib, a spleen tyrosine kinase (Syk) inhibitor, represents a new therapeutic opportunity for patients with immune thrombocytopenia (ITP) in Europe and Italy. However, the positioning of this drug in patient's therapeutic sequence is undefined within the most recent international guidelines. The conclusions from a consensus meeting between Italian experts, whose task was to outline the profile of the ideal candidate to receive fostamatinib, are reported here. A modified Delphi methodology was used to achieve shared statements, which were reported in a narrative form. In particular, the panelists examined the strengths and weaknesses of the registration studies in terms of clinical outcomes, the safety profile of fostamatinib, the drug's impact on the quality of life of patients with chronic ITP, and the potential benefits of its use in the pandemic era. Although the experience with thrombopoietin receptor agonists (TPO-RAs) and the amount of data from real-world studies suggest the preferential use of these drugs as a second-line treatment in most patients, the absence of an increased thrombotic risk in the clinical trials could make fostamatinib a reasonable choice in patients with an increased risk of vascular events. An unstable platelet count during TPO-RAs might also justify a switch to the Syk inhibitor, which is more likely to stabilize the platelet count in responders. Fostamatinib may be preferred to immunosuppressors during the SARS-CoV-2 pandemic, in patients at infectious risk, or in case of contraindication to splenectomy. Finally, the novel mechanism of action makes it an attractive drug in multi-refractory patient.

A bibliometric analysis of primary immune thrombocytopenia from 2011 to 2021

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

Sustained response off therapy after fostamatinib: A chronic refractory ITP case report

Fostamatinib is a SYK-inhibitor drug recently approved by the FDA and EMA for treating chronic immune thrombocytopenia. This drug induces a response in about 40% of patients and has a good toxicity profile. It is known that discontinuing thrombopoietin receptor agonists (TRAs) with the maintenance of sustained response off therapy is possible. On fostamatinib, we do not yet have such information. In this case report, we describe the story of a woman with a multirefractory immune thrombocytopenia (steroids, splenectomy, rituximab, both available TRAs). After 16 years from diagnosis, she started fostamatinib therapy within a clinical trial and achieved a complete response. Grade 1-2 headache and diarrhea occurred during the first months of therapy. These adverse events were resolved with dose reduction of fostamatinib. Despite the dose reduction, the platelet count remained steadily above 80 × 10⁹/L. After 4 years, fostamatinib was gradually reduced and finally discontinued with no drop in platelet count. This is the first case in which fostamatinib discontinuation resulted in a sustained response off therapy.

Current approaches for the diagnosis and management of immune thrombocytopenia

Immune thrombocytopenia (ITP), is an acquired autoimmune disorder characterized by the destruction of platelets and megakaryocytes, resulting in thrombocytopenia (platelet count <100 × 10⁹/L). This review focuses on the diagnosis and current management of ITP. The diagnosis of ITP is based principally on the exclusion of other causes of isolated thrombocytopenia using patient history, physical examination, blood count, and evaluation of the peripheral blood film. The clinical treatment goals should be to resolve bleeding events and to prevent severe bleeding episodes. The platelet count should be improved to attain a minimum of > 20-30 × 10⁹/L. Therapy should be given as an inpatient in newly diagnosed ITP with a platelet count of > 20 × 10⁹/L or if there is active bleeding. Corticosteroids are considered the standard initial treatment for newly diagnosed patients. Subsequent medical therapies with robust evidence include thrombopoietin receptor agonists (TPO-RAs), rituximab and fostamatinib. Surgical therapy with splenectomy may be considered for patients failing medical therapy. The choice between therapy options is highly dependent upon patient values and preferences.

How we treat primary immune thrombocytopenia in adults

Primary immune thrombocytopenia (ITP) is an immune-mediated bleeding disorder characterized by decreased platelet counts and an increased risk of bleeding. Multiple humoral and cellular immune abnormalities result in accelerated platelet destruction and suppressed platelet production in ITP. The diagnosis remains a clinical exclusion of other causes of thrombocytopenia. Treatment is not required except for patients with active bleeding, severe thrombocytopenia, or cases in need of invasive procedures. Corticosteroids, intravenous immunoglobulin, and anti-RhD immunoglobulin are the classical initial treatments for newly diagnosed ITP in adults, but these agents generally cannot induce a long-term response in most patients. Subsequent treatments for patients who fail the initial therapy include thrombopoietic agents, rituximab, fostamatinib, splenectomy, and several older immunosuppressive agents. Other potential therapeutic agents, such as inhibitors of Bruton's tyrosine kinase and neonatal Fc receptor, are currently under clinical evaluation. An optimized treatment strategy should aim at elevating the platelet counts to a safety level with minimal toxicity and improving patient health-related quality of life, and always needs to be tailored to the patients and disease phases. In this review, we address the concepts of adult ITP diagnosis and management and provide a comprehensive overview of current therapeutic strategies under general and specific situations.

Efgartigimod alfa for the treatment of primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by isolated thrombocytopenia. Most patients with ITP have antiplatelet antibodies of the immunoglobulin G (IgG) subtype which through interaction with platelet and megakaryocyte glycoproteins result in increased platelet destruction and inhibition of platelet production. There are a variety of therapeutic options available for the treatment of ITP including corticosteroids, IVIgG, TPO-RA, rituximab, fostamatinib, and splenectomy. Long-term remissions with any of these therapies can vary widely and patients may require additional therapy. The neonatal Fc receptor (FcRn) plays a pivotal role in IgG and albumin physiology through recycling pathways. Efgartigimod is a human IgG1-derived fragment that has been modified by ABDEG technology to increase its affinity for FcRn at both physiologic and acidic pH. The binding of efgartigimod to FcRn blocks the interaction of IgG with FcRn facilitating increased lysosomal degradation of IgG and decreasing total IgG levels. Based on the mechanism of action and the known pathophysiology of ITP as well as the efficacy of other therapies such as intravenous immunoglobulin (IVIG), the use of efgartigimod in patients with ITP is attractive. This article will briefly discuss the pathophysiology of ITP, current treatments, and the data available on efgartigimod in ITP.

The Efficacy and Safety of Fostamatinib in Elderly Patients with Immune Thrombocytopenia: A Single-Center, Real-World Case Series

Fostamatinib is a small molecule spleen tyrosine kinase (Syk) inhibitor that was approved for the treatment of adult patients with immune thrombocytopenia (ITP) in second-line therapy. Syk inhibition prevents cytoskeletal rearrangements during phagocytosis, allowing platelet survival in ITP. However, fostamatinib treatment in elderly patients with ITP has not been well established. We performed a retrospective review of all elderly patients (age greater than or equal to 65 years) who had started on fostamatinib for the treatment of ITP at a single tertiary care centre to evaluate its efficacy and safety. Seven patients, median age 80 years (range 78–94), four women and three men, all of Caucasian background, with various comorbidities, started fostamatinib 100 mg orally twice daily as second or subsequent line therapy. Patients had a diagnosis of ITP for a median of 6 years (range approximately 6 months–30 years), had six comorbidities (range 2–14), and experienced 2 unique prior lines of ITP therapy (range 1 to 6). Over 1290 days of fostamatinib exposure, two patients required dose escalation to 150 mg orally twice daily, while five patients remained on the initial starting dose of 100 mg twice daily. The median platelet count at the time of initiating fostamatinib was 25 × 10⁹/L (range less than 10–193). The median time to response (defined as any first platelet count greater than or equal to 30 × 10⁹/L) was 19 days (range 0–181 days), with two patients responding rapidly (5 days and 19 days). Two patients required dose escalation and rescue therapy, and these same two patients discontinued fostamatinib after 175 days and 216 days of treatment. Treatment was tolerated in all patients with no thromboembolic events observed. One death was noted and unrelated to treatment. Overall, fostamatinib was effective and safe for the majority of these very elderly patients with ITP.

New Therapies for the Treatment of Warm Autoimmune Hemolytic Anemia

In this review article we provide a critical insight into recent reports evaluating innovative therapies for warm type autoimmune hemolytic anemia (wAIHA). Among published articles, we selected two reports on the use of the proteasome inhibitor bortezomib in association with dexamethasone or rituximab, one study on the spleen tyrosine kinase inhibitor fostamatinib, and a retrospective study on recombinant erythropoietin (rEPO). Among recent scientific communications, we discussed a report on the phosphoinositide 3-kinase delta inhibitor (PI3Kδi) parsaclisib. All studies highlighted a good efficacy although to be confirmed in larger trials and with limitations due to the heterogeneity of wAIHA patients enrolled, the small number of subjects, the concomitant medications allowed, and the short follow-up. Ongoing trials include new B-cell/plasma-cell targeting agents such as the Bruton tyrosine kinase inhibitors ibrutinib and rilzabrutinib, and the anti-CD38 MoAbs daratumumab and its analogue isatuximab. Further drugs in clinical trials target the complement cascade in wAIHA with complement activation, such as the C3 inhibitor pegcetacoplan and the C1q inhibitor ANX005. Finally, an interesting and non-immuno-toxic strategy is to remove the pathogenic autoantibodies via blocking the neonatal Fc receptor, by intravenous nipocalimab and subcutaneous RVT-1401. Such novel agents targeting the several immunopathological mechanisms acting in wAIHA and their possible combination, will increase the therapeutic armamentarium and possibly fill the gap of wAIHA relapsed after/refractory to rituximab. Moreover, these new target therapies may represent a tool for the unmet need of very acute cases.

An updated evaluation of avatrombopag for the treatment of chronic immune thrombocytopenia

INTRODUCTION

Multiple agents are available for the management of chronic immune thrombocytopenia (ITP), including thrombopoietin-receptor agonists (TPO-RAs), rituximab, and fostamatinib. Although TPO-RAs are often selected as treatments for chronic ITP, when choosing between the TPO-RAs, clinicians must balance safety profile, dosing restrictions, and method of administration incorporating patient preference.

AREAS COVERED

We provide an overview of the thrombopoietin receptor agonists with a particular focus on avatrombopag, the newest agent in this class. In phase II and III clinical trials, avatrombopag was shown to offer durable improvement in platelet counts. We also include recent real-world evidence describing avatrombopag effectiveness in patients with poor response to prior treatments (including other TPO-RAs).

EXPERT OPINION

Compared with other TPO-RAs used to treat ITP, avatrombopag offers practical oral dosing with a single pill strength, does not require long-term dietary restrictions, and has no warning for hepatotoxicity. It is frequently effective after use of other TPO-RAs in ITP. The primary downside with avatrombopag use at present is the lack of longer-term safety data in ITP that presently exists for romiplostim and eltrombopag.

Clinical Pharmacokinetics and Pharmacodynamics of Fostamatinib and Its Active Moiety R406

Fostamatinib is the first approved spleen tyrosine kinase inhibitor for chronic immune thrombocytopenia. This review summarizes the clinical development, pharmacokinetics, pharmacodynamics, drug-drug interactions, adverse events, and comprehensive analyses of fostamatinib. While integrating these findings, we discuss the fostering and improvement of fostamatinib for further clinical applications. Fostamatinib is designed as a prodrug and cleavage of its active moiety R406 in the intestine. As R406 is the major product in the blood, this review mainly discusses the pharmacokinetics and pharmacodynamics of R406. It is metabolized by cytochrome 3A4 and UGT1A9 in the liver and is dominantly excreted in feces after anaerobic modification by the gut microbiota. As fostamatinib and R406 strongly inhibit the breast cancer resistance protein, the interaction with those substrates, particularly statins, should be carefully monitored. In patients with immune thrombocytopenia, fostamatinib administration started at 100 mg twice daily, and most patients increased to 150 mg twice daily in the clinical trial. Although responders showed a higher R406 concentration than non-responders, the correlation between R406 exposure and achievement of the platelet count as a pharmacodynamic marker was uncertain in the pharmacokinetic/pharmacodynamic analysis. Additionally, R406 concentration was almost halved in patients with a heavy body weight; hence, the exposure-efficacy study for suitable dosing should be continued with post-marketing data. In contrast, the pharmacokinetic/pharmacodynamic analysis for exposure safety revealed that R406 exposure significantly correlated with the incidence of hypertension. Even though the influence of elevated exposure on other toxicities, including diarrhea and neutropenia, is still unclear, careful management is required with dose escalation to avoid toxicity-related discontinuation.

Novel Therapies to Address Unmet Needs in ITP

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

Antithrombotic Effects of Fostamatinib in Combination with Conventional Antiplatelet Drugs

New antithrombotic medications with less effect on haemostasis are needed for the long-term treatment of acute coronary syndromes (ACS). The platelet receptor glycoprotein VI (GPVI) is critical in atherothrombosis, mediating platelet activation at atherosclerotic plaque. The inhibition of spleen tyrosine kinase (Syk) has been shown to block GPVI-mediated platelet function. The aim of our study was to investigate if the Syk inhibitor fostamatinib could be repurposed as an antiplatelet drug, either alone or in combination with conventional antiplatelet therapy. The effect of the active metabolite of fostamatinib (R406) was assessed on platelet activation and function induced by atherosclerotic plaque and a range of agonists in the presence and absence of the commonly used antiplatelet agents aspirin and ticagrelor. The effects were determined ex vivo using blood from healthy volunteers and aspirin- and ticagrelor-treated patients with ACS. Fostamatinib was also assessed in murine models of thrombosis. R406 mildly inhibited platelet responses induced by atherosclerotic plaque homogenate, likely due to GPVI inhibition. The anti-GPVI effects of R406 were amplified by the commonly-used antiplatelet medications aspirin and ticagrelor; however, the effects of R406 were concentration-dependent and diminished in the presence of plasma proteins, which may explain why fostamatinib did not significantly inhibit thrombosis in murine models. For the first time, we demonstrate that the Syk inhibitor R406 provides mild inhibition of platelet responses induced by atherosclerotic plaque and that this is mildly amplified by aspirin and ticagrelor.

Fostamatinib for the treatment of warm antibody autoimmune hemolytic anemia: Phase 2, multicenter, open-label study

Patients with relapsed warm antibody autoimmune hemolytic anemia (wAIHA) have limited treatment options. Fostamatinib is a potent, orally administered spleen tyrosine kinase inhibitor approved in the United States and Europe for the treatment of adults with chronic immune thrombocytopenia (ITP). This phase 2 study evaluated the response to fostamatinib, administered at 150 mg BID orally with or without food in adults with wAIHA and active hemolysis with hemoglobin (Hgb) <10 g/dL who had failed at least one prior treatment. Hemoglobin levels and safety assessments were performed at visits every 2 weeks. The primary endpoint was Hgb >10 g/dL with an increase of ≥2 g/dL from baseline by week 24 without rescue therapy or red blood cell transfusion. Eleven of 24 (46%) patients achieved the primary endpoint. Increases in median Hgb were detected at week 2 and sustained over time. Median lactate dehydrogenase levels and reticulocyte counts generally declined over time with little change in median haptoglobin levels. The most common adverse events (AEs) were diarrhea (42%), fatigue (42%), hypertension (27%), dizziness (27%), and insomnia (23%). AEs were manageable and consistent with the fostamatinib safety database of over 3900 patients across multiple diseases (rheumatoid arthritis, B-cell lymphoma, COVID-19, and ITP). No new safety signals were detected. Fostamatinib may be a promising therapeutic option for wAIHA. A randomized, double-blind, phase 3 study is nearing completion.

Evaluating fostamatinib disodium as a treatment option for immune thrombocytopenia in adult patients

INTRODUCTION

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by increased platelet destruction and decreased platelet production, leading to thrombocytopenia with or without bleeding manifestations. The majority of patients experiencing treatment need will eventually need secondary treatment following first line therapy with steroids. In 2018, the oral spleen tyrosine kinase inhibitor fostamatinib received US Food and Drug Administration approval for ITP patients with an insufficient response to a previous treatment.

AREAS COVERED

This review outlines pharmacological characteristics of fostamatinib and provides an overview of its efficacy and safety results in phase II and III trials, followed by the expert opinion of the authors.

EXPERT OPINION

Increasing knowledge on the role of different players and mechanisms in the pathophysiology of autoimmune disorders in general and of ITP in particular, has led to the development of several new treatment options, as illustrated by the introduction of fostamatinib in the treatment of ITP. However, lacking direct comparison with other recent treatment options (in particular thrombopoietin receptor agonists), its use should be evaluated critically taking into account the unique toxicity and potential drug-drug interaction profile.

Development of New Drugs for Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a rare disorder characterized by the autoantibody-mediated destruction of red blood cells, and treatments for it still remain challenging. Traditional first-line immunosuppressive therapy, which includes corticosteroids and rituximab, is associated with adverse effects as well as treatment failures, and relapses are common. Subsequent lines of therapy are associated with higher rates of toxicity, and some patients remain refractory to currently available treatments. Novel therapies have become promising for this vulnerable population. In this review, we will discuss the mechanism of action, existing data, and ongoing clinical trials of current novel therapies for AIHA, including B-cell-directed therapy, phagocytosis inhibition, plasma cell-directed therapy, and complement inhibition.

Primary immune thrombocytopenia in adults: Belgian recommendations for diagnosis and treatment anno 2021 made by the Belgian Hematology Society

The Belgian Hematology Society (BHS) updated the 2013 guidelines for diagnosis and treatment of primary immune thrombocytopenia (ITP) [1]. As knowledge about ITP pathophysiology is increasing, the mode of action of old therapies is better understood and novel drugs are introduced to target more specific pathways.Corticosteroids with or without intravenous immunoglobulins (IgIV) remain the first-line treatment. According to the updated international guidelines a short course of corticosteroids rather than a prolonged treatment has to be recommended. The same guidelines stress that consequent therapies as thrombopoietic agents (TPO-RAs) and rituximab should be available independent of duration of ITP.Although the majority of recommendations is based on very low-quality evidence, it is strongly advised to individualize the ITP management taking patient values. and preferences in account. The main treatment goal in all ITP patients must be to maintain a safe platelet count to prevent or stop bleeding with a minimum of toxicity and not to normalize the platelet count.

Src-related thrombocytopenia: a fine line between a megakaryocyte dysfunction and an immune-mediated disease

Src-related thrombocytopenia (SRC-RT) is a rare autosomal dominant inherited platelet disorder due to the p.E527K heterozygous germline gain-of-function variant of Src. To date, genetic diagnosis of the disease has only been reported in seven patients from three unrelated families. The clinical features ranged from isolated thrombocytopenia to complex syndromic manifestations characterized by thrombocytopenia, bleeding, myelofibrosis, splenomegaly, and bone disease. We report a new three-generation kindred with the Src p.E527K variant. Patients presented with rather variable platelet counts (38 - 139 x 109/L), mildly impaired platelet function, >15% immature platelet fraction, and with a significant proportion of large-giant platelets. Four adults from the family were diagnosed with immune thrombocytopenia (ITP) and underwent splenectomy, achieving sustained platelet counts above 75 x 109/L for several years; increases in platelet counts were also observed after corticosteroid therapy. Four of seven Src p.E527K variant carriers showed immune defects and recurrent infections. In addition, a range of neurological symptoms, from specific language impairment to epilepsy was seen in some family members. Patient platelets exhibited constitutive Src, BTK, and PLC2 activation, and after stimulating CD19 cells by crosslinking surface IgM, phosphorylated ERK was significantly increased in B cells from individuals carrying the Src p.E527K substitution. In summary, in addition to causing impaired platelet production, SRC-RT may associate immune dysregulation, and increased platelet consumption. In families in whom several members are responsive to ITP directed therapies, an underlying Src p.E527K variant should be excluded.

In silico Analysis of Publicly Available Transcriptomics Data Identifies Putative Prognostic and Therapeutic Molecular Targets for Papillary Thyroid Carcinoma

Background

Purpose

Methods

Results

Conclusion

Refractory primary immune thrombocytopenia (ITP): current clinical challenges and therapeutic perspectives

Chronic primary immune thrombocytopenia (ITP) can today benefit from multiple therapeutic approaches with proven clinical efficacy, including rituximab, thrombopoietin receptor agonists (TPO-RA), and splenectomy. However, some ITP patients are unresponsive to multiple lines of therapy with prolonged and severe thrombocytopenia. The diagnosis of refractory ITP is mainly performed by exclusion of other disorders and is based on the clinician's expertise. However, it significantly increases the risk of drug-related toxicity and of bleedings, including life-threatening events. The management of refractory ITP remains a major clinical challenge. Here, we provide an overview of the currently available treatment options, and we discuss the emerging rationale of new therapeutic approaches and their strategic combination. Particularly, combination strategies may target multiple pathogenetic mechanisms and trigger additive or synergistic effects. A series of best practices arising both from published studies and from real-life clinical experience is also included, aiming to optimize the management of refractory ITP.

Recent advances in the mechanisms and treatment of immune thrombocytopenia

Primary immune thrombocytopenia is an autoimmune disease associated with a reduced peripheral blood platelet count. The phenotype is variable with some patients suffering no bleeding whilst others have severe bleeding which may be fatal. Variability in clinical behaviour and treatment responses reflects its complex underlying pathophysiology. Historically the management has relied heavily on immune suppression. Recent studies have shown that the older empirical immune suppressants fail to alter the natural history of the disease and are associated with a poor quality of life for patients. Newer treatments, such as the thrombopoietin receptor agonists, have transformed ITP care. They have high efficacy, are well tolerated and improve patients’ quality of life. A greater understanding of the underlying pathophysiology of this disorder has helped develop a number of new targeted therapies. These include inhibitors of the neonatal Fc receptor inhibitors, Bruton tyrosine kinase and complement pathway. Here we discuss the mechanisms underlying ITP and the new approach to ITP care.