Emerging Therapies in Immune Thrombocytopenia

The role of immunoglobulin transport receptor, neonatal Fc receptor in mucosal infection and immunity and therapeutic intervention

The neonatal Fc receptor (FcRn) can transport IgG and antigen-antibody complexes participating in mucosal immune responses that protect the host from most pathogens' invasion via the respiratory, digestive, and urogenital tracts. FcRn expression can be triggered upon stimulation with pathogenic invasion on mucosal surfaces, which may significantly modulate the innate immune response of the host. As an immunoglobulin transport receptor, FcRn is implicated in the pathophysiology of immune-related diseases such as infection and autoimmune disorders. In this review, we thoroughly summarize the recent advancement of FcRn in mucosal immunity and its therapeutic strategy. This includes insights into its regulation mechanisms of FcRn expression influenced by pathogens, its emerging role in mucosal immunity and its potential probability as a therapeutic target in infection and autoimmune diseases.

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.

Graves disease: latest understanding of pathogenesis and treatment options

Graves disease is the most common cause of hyperthyroidism in iodine-sufficient areas. The main responsible mechanism is related to autoantibodies that bind and activate the thyrotropin receptor (TSHR). Although Graves hyperthyroidism is relatively common, no causal treatment options are available. Established treatment modalities are antithyroid drugs, which reduce thyroid hormone synthesis, radioactive iodine and surgery. However, emerging drugs that target the main autoantigen (monoclonal antibodies, small molecules, peptides) or block the immune pathway have been recently tested in clinical trials. Graves disease can involve the thyroid exclusively or it can be associated with extrathyroidal manifestations, among which Graves orbitopathy is the most common. The presence of Graves orbitopathy can change the management of the disease. An established treatment for moderate-to-severe Graves orbitopathy is intravenous glucocorticoids. However, recent advances in understanding the pathogenesis of Graves orbitopathy have allowed the development of new target-based therapies by blocking pro-inflammatory cytokine receptors, lymphocytic infiltration or the insulin-like growth factor 1 receptor (IGF1R), with several clinical trials providing promising results. This article reviews the new discoveries in the pathogenesis of Graves hyperthyroidism and Graves orbitopathy that offer several important tools in disease management.

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.

The role of BAFF and BAFF-R inhibitors in the treatment of immune thrombocytopenia; a focused review

Immune thrombocytopenia (ITP) is an autoimmune-driven disease characterized by increased destruction and impaired platelet production resulting in an enhanced risk of bleeding. Immunosuppressant agents are the most common treatment strategies for ITP. Despite their efficacy, these medications often cause unpredictable side effects. Recent investigations revealed that patients with ITP exhibit elevated B-cell activating factor (BAFF) levels in both their spleens and serum. Belimumab, a BAFF inhibitor, illustrated a promising therapeutic avenue for managing ITP by interfering with BAFF activity and long-lived plasma cell production. Both clinical and experimental studies have yielded positive outcomes when combining rituximab with an anti-BAFF monoclonal antibody in treating ITP. In addition, ianalumab, a monoclonal antibody with a dual mechanism that targets BAFF-R and deletes peripheral BAFF-R+ B cells, is currently being used for ITP treatment [NCT05885555]. The upcoming results from novel BAFF inhibitors, such as ianalumab, could offer clinicians an additional therapeutic option for treating ITP.

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.

Efficacy and safety of mycophenolate mofetil in patients with immune thrombocytopenic purpura: a systematic review and meta-analysis

BACKGROUND

Immune thrombocytopenic purpura (ITP) is a challenging disease in its presentation and management as it may cause life-threatening hemorrhaging in vital organs and may resist several lines of treatment. This systematic review and meta-analysis aimed to evaluate the safety and efficacy of mycophenolate mofetil (MMF) in treating patients with ITP.

METHODS

We systematically searched four electronic databases (PubMed, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials) from inception until 10 October 2022. We included all clinical trials, either controlled or single arm, and prospective and retrospective observational studies that evaluate the efficacy and safety of MMF in patients with ITP. We assessed the risk of bias using three tools (ROBINS-I, Cochrane ROB-2, and NIH), each for eligible study design.

RESULTS

Nine studies were included in this meta-analysis, with a total of 411 patients with ITP. We found that MMF demonstrated an overall response rate of (62.09%; 95% CI = [43.29 to 77.84]) and the complete response rate was (46.75%; 95% CI = [24.84 to 69.99]). The overall proportion of adverse events was (12%; 95% CI = [6 to 24]). After the sensitivity analysis, the overall response rate became 50%; 95% CI = [38 to 63]) and the complete response rate became (32%; 95% CI = [24 to 42]). However, MMF did not appear to affect white blood cell counts or hemoglobin levels significantly.

CONCLUSION

This systematic review and meta-analysis demonstrate that MMF appears to be an effective and relatively safe treatment option for patients with ITP when combined with steroids and even in those who have not responded to standard therapies (steroid-resistant cases). Further research with well-designed studies is warranted to better understand the factors influencing treatment response and to refine the use of MMF in the management of ITP. An interactive version of our analysis can be accessed from here: https://databoard.shinyapps.io/mycophenolate_meta/.

Recent advances in the management of immune thrombocytopenic purpura (ITP): A comprehensive review

Autoimmune disorders place a substantial burden on the healthcare system all over the world affecting almost 3% to 8% of the population. Immune thrombocytopenic purpura (ITP), also known as idiopathic thrombocytopenic purpura, is a blood disorder in which the body immune system destroys platelets, leading to low platelet counts in the blood (peripheral blood platelet count < 150 × 109/L). Although the pathophysiology of ITP is not fully understood, it is believed to result from a complex interplay between hereditary and environmental variables. Certain factors, such as a low platelet count, history of bleeding, and certain comorbidities can increase the risk of severe bleeding in patients with ITP. Corticosteroids, intravenous immunoglobulin (IVIG), immunosuppressants, rituximab, and thrombopoietin receptor agonists (TPO-RAs) are some of the advanced treatments for ITP. Although these therapies may be successful, they also carry the risk of negative effects. Recently, significant advancements have been made in the understanding and treatment of ITP. There is still much to learn about the disease, and new, more effective treatments are needed. This comprehensive review offers a comprehensive assessment of recent advancements in ITP management, with a focus on active research projects, novel therapeutic targets, new treatment modalities, and areas of uncertainty and unmet needs. According to research, it is crucial to develop individualized treatment plans for ITP patients based on their age, platelet count, risk of bleeding, and comorbidities. The article also looks at how future developments in gene editing, bispecific antibody therapies, and cellular therapy may completely change the treatment of ITP.

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.

B cells and antibodies in refractory immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired bleeding disorder mediated by pathogenic autoantibodies secreted by plasma cells (PCs) in many patients. In refractory ITP patients, the persistence of splenic and bone marrow autoreactive long-lived PCs (LLPCs) may explain primary failure of rituximab and splenectomy respectively. The reactivation of autoreactive memory B cells generating new autoreactive PCs contributes to relapses after initial response to rituximab. Emerging strategies targeting B cells and PCs aim to prevent the settlement of splenic LLPCs with the combination of anti-BAFF and rituximab, to deplete autoreactive PCs with anti-CD38 antibodies, and to induce deeper B-cell depletion in tissues with novel anti-CD20 monoclonal antibodies and anti-CD19 therapies. Alternative strategies, focused on controlling autoantibody mediated effects, have also been developed, including SYK and BTK inhibitors, complement inhibitors, FcRn blockers and inhibitors of platelet desialylation.

Decreased cyclooxygenase-2 associated with impaired megakaryopoiesis and thrombopoiesis in primary immune thrombocytopenia

BACKGROUND

Cyclooxygenase (COX)-2 is a rate-limiting enzyme in the biosynthesis of prostanoids, which is mostly inducible by inflammatory cytokines. The participation of COX-2 in the maturation of megakaryocytes has been reported but barely studied in primary immune thrombocytopenia (ITP).

METHODS

The expressions of COX-2 and Caspase-1, Caspase-3 and Caspase-3 p17 subunit in platelets from ITP patients and healthy controls (HC), and the expressions of COX-2 and CD41 in bone marrow (BM) of ITP patients were measured and analyzed for correlations. The effects of COX-2 inhibitor on megakaryopoiesis and thrombopoiesis were assessed by in vitro culture of Meg01 cells and murine BM-derived megakaryocytes and in vivo experiments of passive ITP mice.

RESULTS

The expression of COX-2 was decreased and Caspase-1 and Caspase-3 p17 were increased in platelets from ITP patients compared to HC. In platelets from ITP patients, the COX-2 expression was positively correlated with platelet count and negatively correlated to the expression of Caspase-1. In ITP patients BM, the expression of CD41 was positively correlated with the expression of COX-2. COX-2 inhibitor inhibited the count of megakaryocytes and impaired the maturation and platelet production in Meg01 cells and bone marrow-derived megakaryocytes. COX-2 inhibitor aggravated thrombocytopenia and damaged megakaryopoiesis in ITP murine model.

CONCLUSION

COX-2 plays a vital role in the physiologic and pathologic conditions of ITP by intervening the survival of platelets and impairing the megakaryopoiesis and thrombopoiesis of megakaryocytes.

The Outcomes and Adverse Drug Patterns of Immunomodulators and Thrombopoietin Receptor Agonists in Primary Immune Thrombocytopenia Egyptian Patients with Hemorrhage Comorbidity

Immune thrombocytopenia (ITP) treatment has evolved recently. However, none of the treatments have only benefits without drawbacks. This study aimed to compare the clinical outcomes and adverse drug patterns of Eltrombopag, Romiplostim, Prednisolone + Azathioprine, High Dose-dexamethasone (HD-DXM) (control group), and Rituximab in primary ITP Egyptian patients. All patients were initiated with corticosteroids, HD-DXM, as a first-line treatment for the first month immediately following diagnosis. Four hundred sixty-seven ITP patients were randomly assigned to five groups. The outcome measures were judged at baseline, at the end of treatment (6 months), and after an additional 6-month free treatment period. The follow-up period for which relapse is noted was 6 months after the end of treatment. Eltrombopag and Romiplostim resulted in a significantly higher incidence of sustained response than Rituximab, HD-DXM, and Prednisolone + Azathioprine (55.2% and 50.6% vs. 29.2%, 29.1%, and 18%, respectively; p-value < 0.001). More patients on immunomodulators (Prednisolone+ Azathioprine, HD-DXM, and Rituximab) relapsed than those on Romiplostim and Eltrombopag (81.9%, 70.8%, and 70.7% vs. 49.3%, and 44.7%, respectively; p-value < 0.01). We also describe 23 reports of pulmonary hypertension with Prednisolone+ Azathioprine and 13 reports with HD-DXM. The thrombotic events occurred in 16.6% and 13% of patients who received Eltrombopag and Romiplostim treatment, respectively. Most patients had at least one or two risk factors (92.8% of cases). Corticosteroids are effective first-line therapy in primary ITP patients. However, relapse is frequent. Eltrombopag and Romiplostim are safer and more effective than Prednisolone, HD-DXM, and Rituximab. They might be reasonable beneficial options after a one-month HD-DXM regimen.

Daratumumab as a novel treatment option in refractory ITP

Primary immune thrombocytopenia (ITP) in adult patients typically presents as a repeatedly relapsing disease in need of multiple lines of therapy. Here we report the clinical courses of two patients, an 82-year-old female and a 54-year-old male, with primary ITP after multiple relapses and exhausted standard therapies, which we treated with the myeloma-licensed anti-CD38 monoclonal antibody daratumumab in an off-label setting. Daratumumab is known to target preferentially plasmablasts, short-lived plasma cells and long-lived plasma cells, with the latter being the major source of antiplatelet autoantibodies. Noteworthy, rituximab, a CD20 antibody, targets earlier steps in B-cell ontogenesis, thereby indirectly decreasing plasmablasts and short-lived plasma cells, but to a lesser extent long-lived plasma cells, which tend to persist after rituximab treatment. Several single-patient reports and case series have demonstrated successful treatment with daratumumab in ITP, autoimmune thrombocytopenia in Evans syndrome as well as other cytopenias or pure red cell aplasia after allogeneic stem cell transplantation or in congenital diseases, systemic lupus erythematodes and cold agglutinin disease. Our first patient with isolated primary ITP rapidly and lastingly responded to daratumumab plus tapered steroids, with platelet counts above 50 × 10⁹/L within weeks and subsequently even stably within the normal range. Despite no objective response observed in the second patient, a lasting clinical stabilization was achieved. As the underlying mode of action, we hypothesize here daratumumab to effectively target long-lived plasma cells as the source of ITP-mediating autoantibodies, and suggest broader clinical evaluation of daratumumab in this potential indication.

Recombinant Thrombopoietin Effectively Shortens the Time to Response and Increases Platelet Counts in Elderly Patients with Severe Immune Thrombocytopenia

Background: This study was conducted to investigate the short-term efficacy and safety of rhTPO for the management of severe ITP in the elderly as first-line treatment. Methods: A total of 54 elderly patients with severe ITP were studied, including 39 patients treated with a combination regimen of rhTPO plus standard treatment (glucocorticoid; rhTPO group) and 15 patients treated with glucocorticoid treatment alone (control group). The response rate, time to initial response, peak platelet counts, and time to peak platelet counts were compared, and clinical characteristics correlated with the efficacy of rhTPO were analyzed. The efficacy of rhTPO in the elderly is comparable to the non-elderly in terms of the OR, CR, time to initial response, and peak platelet counts. Results: There were no differences in the overall response (OR) and the complete response (CR) in the rhTPO group compared to the control group. The time to initial response in the rhTPO group was shorter than that in the control group (p = 0.032). In patients without intravenous immunoglobulin (IVIg) and platelet transfusion, the peak platelet counts in the rhTPO group were higher than those in the control group (p = 0.003). Conclusions: Standard glucocorticoid treatment plus rhTPO effectively shortens the time to response and increases platelet counts in the elderly with severe ITP.

Evaluation of paediatric immune thrombocytopenia patients with clinical and laboratory findings: emphasizing the role of monocytosis

We aimed to investigate the relationship between demographics, clinical features, laboratory findings including monocytosis and clinical course in children with immune thrombocytopenia (ITP). Data of 100 ITP patients were analysed. Complete blood count findings of the patients at certain time points were evaluated to classify the disease as acute, persistent and chronic. An effect of sex on chronicity was not observed ( P  = 0.166). Of the patients enrolled in the study, 38% ( n  = 38) had chronic course. The mean age of patients with the chronic course was 7 ± 4.1 years, which was significantly higher than the other groups ( P  = 0.007). Sixty-five percent ( n  = 13) of the patients presenting with mucosal bleeding and 27.4% ( n  = 20) of the patients presenting with skin bleeding became chronic ( P  = 0.008). MPV was found to be significantly high in chronic ITP patients ( P  = 0.049). Monocytosis was noted in 80% of the patients at diagnosis. Intravenous immunoglobulin was used in 84% of the patients with acute ITP; 33% of them developed chronic ITP. The age at diagnosis, presence of mucosal bleeding and increased MPV on admission were high-risk factors for the development of the chronic course. Monocytosis was detected in 80% of the patients on admission, and it may play a role in the pathogenesis of ITP.

Association between P-Selectin Autoantibody Positive and Response to Steroid Treatment in Newly Diagnosed Immune Thrombocytopenia Patients

OBJECTIVE

This study aimed to detect the association between P-selectin autoantibody positive and response to steroid treatment in newly diagnosed immune thrombocytopenia (ITP) patients.

METHODS

The data from 105 newly diagnosed adult ITP patients administered with first-line of steroid treatment from October 2016 to May 2021 were retrospectively analyzed. Treatment responses were evaluated within 3 months after the onset of treatment.

RESULTS

Among the 105 patients, 80.00% (84/105) of patients presented with platelet glycoprotein-specific antibody positive; 44.76% (47/105) patients were anti-P-selectin positive, while 35.24% (37/105) were anti-P-selectin negative. No significant difference in overall response was observed between patients who were anti-P-selectin positive and those who were anti-P-selectin negative (74.47% vs. 89.19, χ2 = 2.910, p = 0.088). But patients who were anti-P-selectin negative had significantly higher complete response rate, compared to those who were anti-P-selectin positive (72.97% vs. 48.94%, χ2 = 4,965, p = 0.026). Logistic regression analysis revealed that anti-GP IIb/IIIa positive (OR = 3.114, p = 0.010, 95% CI: 1.313-7.388) and anti-P-selectin positive (OR = 0.309, p = 0.036, 95% CI: 0.127-0.753) were two factors that could affect patients' response.

CONCLUSIONS

Our study found that ITP patients with anti-GP IIb/IIIa may have a higher response to steroid treatment, but anti-P-selectin-mediated-ITP might be less responsive to steroid treatment. In adults with ITP, the presence of anti-P-selectin autoantibodies is a predictive factor for poor response to steroid treatment.

Association of CD40 gene polymorphisms and immune thrombocytopenic purpura in the adult Egyptian population

Background

The pathophysiology underlying primary adult immune thrombocytopenic purpura (ITP) has not yet been identified. However, many mechanisms affect the immune system, causing defective tolerance to self-platelets and megakaryocytes. Cluster of differentiation 40 (CD40) contributes to both humoral and cell-mediated immune responses.

Methods

This case‒control study was conducted to detect rs4810485G>T and rs1883832C>T polymorphisms of CD40 in Egyptian patients with persistent/chronic ITP to clarify their possible association with chronic disease evolution. This study included 50 patients with persistent/chronic ITP and 50 healthy controls. Genotyping was performed using the polymerase chain reaction‒restriction fragment length polymorphism technique.

Results

Genotyping of rs1883832 and rs4810485 revealed no statistically significant differences between the two groups. However, combined gene polymorphism genotyping showed a statistically significant difference between the two groups (P<0.01).

Conclusion

Our results indicate a strong association between the combined polymorphism of both genes and susceptibility to developing ITP among adult Egyptian patients. Targeting this pathway using novel therapeutic approaches is promising.

Mechanism and Molecular Targets of Ejiao Siwu Decoction for Treating Primary Immune Thrombocytopenia Based on High-Performance Liquid Chromatograph, Network Pharmacology, Molecular Docking and Cytokines Validation

We explored the mechanisms and molecular targets of Ejiao Siwu Decoction (EJSW) for treating primary immune thrombocytopenia (ITP) using network pharmacology and molecular docking. Active compounds of EJSW were identified by high-performance liquid chromatography-diode array detector (HPLC-DAD) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) and their targets were obtained from HERB and SwissTargetPrediction, and ITP targets were obtained from Comparative Toxicogenomics Database (CTD) and GeneCards. STRING and Cytoscape were used for protein-protein interaction (PPI) network analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses by WebGestalt yielded a gene-pathway network, Autodock molecular docking was applied to screen targets and active compounds, and cytokines were detected using a cytometric bead array (CBA) human inflammation kit. We identified 14 compounds and 129 targets, and 1,726 ITP targets. RAC-alpha serine/threonine-protein kinase (AKT1), tumour necrosis factor (TNF), interleukin-6 (IL6), caspase-3 (CASP3) and tumour suppressor protein (TP53) were core targets (nodes and edges). Functional annotation identified cofactor binding and coenzyme binding, and 20 significantly enriched pathways. Active compounds of EJSW were successfully docked with ITP targets. Tumour necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) were upregulated in ITP patients, vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor D (VEGF-D) were downregulated, and EJSW treatment reversed these trends. EJSW may regulate key ITP targets based on the in silico analyses, and protect vascular integrity through AGE-RAGE signalling, complement and coagulation cascades, and VEGF signalling by downregulating TNF-α, IL-1β and other inflammatory factors.

Potential Autoimmunity Resulting from Molecular Mimicry between SARS-CoV-2 Spike and Human Proteins

Molecular mimicry between viral antigens and host proteins can produce cross-reacting antibodies leading to autoimmunity. The coronavirus SARS-CoV-2 causes COVID-19, a disease curiously resulting in varied symptoms and outcomes, ranging from asymptomatic to fatal. Autoimmunity due to cross-reacting antibodies resulting from molecular mimicry between viral antigens and host proteins may provide an explanation. Thus, we computationally investigated molecular mimicry between SARS-CoV-2 Spike and known epitopes. We discovered molecular mimicry hotspots in Spike and highlight two examples with tentative high autoimmune potential and implications for understanding COVID-19 complications. We show that a TQLPP motif in Spike and thrombopoietin shares similar antibody binding properties. Antibodies cross-reacting with thrombopoietin may induce thrombocytopenia, a condition observed in COVID-19 patients. Another motif, ELDKY, is shared in multiple human proteins, such as PRKG1 involved in platelet activation and calcium regulation, and tropomyosin, which is linked to cardiac disease. Antibodies cross-reacting with PRKG1 and tropomyosin may cause known COVID-19 complications such as blood-clotting disorders and cardiac disease, respectively. Our findings illuminate COVID-19 pathogenesis and highlight the importance of considering autoimmune potential when developing therapeutic interventions to reduce adverse reactions.

Expansion of Human Megakaryocyte-Lineage Progeny via Aryl Hydrocarbon Receptor Antagonism with CH223191

Aryl hydrocarbon receptor (AhR) antagonism is known to expand human hematopoietic stem cells (HSCs). However, its regulatory effect on the lineage-skewed differentiation of HSCs has not been sufficiently studied. Here, we investigate the effect of the AhR-selective antagonist CH223191 on the regulation of HSC differentiation. Consistent with the well-known effects of AhR antagonists, CH223191 treatment increase phenotypic HSCs (Lin-CD34 + CD38-CD90 + CD45RA-) and preserves their functionality. On the other hand, CH223191 leads to an overall expansion of megakaryocyte (MK)-lineage populations, such as MK progenitors (MKps, CD34 + CD41 +), immature MKs (CD41 + CD42b-), and mature MKs (CD41 + CD42b +), and it also activates MK/platelet-associated signaling pathways. Furthermore, CH223191 expands MKps, mature MKs, and p-selectin (CD62p)-positive platelet-like particles in immune thrombocytopenia (ITP) patient bone marrow (BM). These results highlight the numerical expansion of human MK-lineage progeny through AhR antagonism with CH223191. This approach using CH2231291 may be applicable in the development of auxiliary treatment regimens for patients with abnormal thrombopoiesis.

Alternatives for managing patients with newly diagnosed immune thrombocytopenia: a narrative review

INTRODUCTION

Primary immune thrombocytopenia (ITP) is an acquired bleeding disorder. Conventionally, first-line ITP therapy aims to obtain a rapid response and stop or decrease the risk of bleeding by increasing the platelet count. At this point, the duration of the response, the tolerability, and the long-term safety of pharmacologic interventions are considered less of a priority. Combination treatments that simultaneously address multiple disease mechanisms are an attractive strategy to increase efficacy in acute ITP therapy. In this review, we discuss the treatment of newly diagnosed ITP patients, emphasizing the use of new combinations to benefit from their synergy.

AREAS COVERED

This article summarizes conventional treatment, recent and novel combinations, and COVID-19 management recommendations of newly diagnosed ITP patients.

EXPERT OPINION

The key areas for improvement consider the long-term effects of conventional first-line therapy, reducing relapse rates, and extending responses to achieve long-term remission. Although corticosteroids remain first-line therapy, restricting their use to avoid toxicity and the increasing use of rituximab and TPO-RAs in the first three months after diagnosis open the landscape for future interventions in frontline therapy for ITP. First-line therapy intensification or synergistic drug combination offers a potential and realistic shift in future treatment guidelines.

High-affinity autoreactive plasma cells disseminate through multiple organs in patients with immune thrombocytopenic purpura

The major therapeutic goal for immune thrombocytopenic purpura (ITP) is to restore normal platelet counts using drugs to promote platelet production or by interfering with mechanisms responsible for platelet destruction. Eighty percent of patients with ITP possess anti–integrin αIIbβ3 IgG autoantibodies that cause platelet opsonization and phagocytosis. The spleen is considered the primary site of autoantibody production by autoreactive B cells and platelet destruction. The immediate failure in approximately 50% of patients to recover a normal platelet count after anti-CD20 rituximab-mediated B cell depletion and splenectomy suggests that autoreactive, rituximab-resistant, IgG-secreting B cells (IgG-SCs) reside in other anatomical compartments. We analyzed more than 3,300 single IgG-SCs from spleen, bone marrow, and/or blood of 27 patients with ITP, revealing high interindividual variability in affinity for αIIbβ3, with variations over 3 logs. IgG-SC dissemination and range of affinities were, however, similar for each patient. Longitudinal analysis of autoreactive IgG-SCs upon treatment with the anti-CD38 mAb daratumumab demonstrated variable outcomes, from complete remission to failure with persistence of high-affinity anti–αIIbβ3 IgG-SCs in the bone marrow. This study demonstrates the existence and dissemination of high-affinity autoreactive plasma cells in multiple anatomical compartments of patients with ITP that may cause the failure of current therapies.

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.

The Use of Clinical Scores in the Management of Immune Thrombocytopenic Purpura in Children

While the majority of children with recently diagnosed ITP have a benign, self-limiting condition, most often with a spontaneously recovery, 40% of children with ITP progress toward persistent ITP and 10-20% goes toward chronicity. Several clinical scores have been developed with the aim to perform a better monitoring outcome or to differentiate transient vs. persistent ITP (e.g., Donato score). Our paper aims to describe and to compare the most important scores used in the management of ITP in children: bleeding severity scores and chronicity prediction scores. These scores include a combination of different already known risk factors: age, gender, presence of a previous infections or vaccination, bleeding grade, type of onset, platelet count at diagnosis. The real utility of these scores has been a matter of debate and no consensus has been reached so far as to their necessity to be implemented as compulsory tool in the care of children with ITP.

Platelet Activation Mechanisms and Consequences of Immune Thrombocytopenia

Autoimmune disorders are often associated with low platelet count or thrombocytopenia. In immune-induced thrombocytopenia (IIT), a common mechanism is increased platelet activity, which can have an increased risk of thrombosis. In addition, or alternatively, auto-antibodies suppress platelet formation or augment platelet clearance. Effects of the auto-antibodies are linked to the unique structural and functional characteristics of platelets. Conversely, prior platelet activation may contribute to the innate and adaptive immune responses. Extensive interplay between platelets, coagulation and complement activation processes may aggravate the pathology. Here, we present an overview of the reported molecular causes and consequences of IIT in the most common forms of autoimmune disorders. These include idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), drug-induced thrombocytopenia (DITP), heparin-induced thrombocytopenia (HIT), COVID-19 vaccine-induced thrombosis with thrombocytopenia (VITT), thrombotic thrombocytopenia purpura (TTP), and hemolysis, the elevated liver enzymes and low platelet (HELLP) syndrome. We focus on the platelet receptors that bind auto-antibodies, the immune complexes, damage-associated molecular patterns (DAMPs) and complement factors. In addition, we review how circulating platelets serve as a reservoir of immunomodulatory molecules. By this update on the molecular mechanisms and the roles of platelets in the pathogenesis of autoimmune diseases, we highlight platelet-based pathways that can predispose for thrombocytopenia and are linked thrombotic or bleeding events.

Platelets in ITP: Victims in Charge of Their Own Fate?

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder. The pathophysiological mechanisms leading to low platelet levels in ITP have not been resolved, but at least involve autoantibody-dependent and/or cytotoxic T cell mediated platelet clearance and impaired megakaryopoiesis. In addition, T cell imbalances involving T regulatory cells (Tregs) also appear to play an important role. Intriguingly, over the past years it has become evident that platelets not only mediate hemostasis, but are able to modulate inflammatory and immunological processes upon activation. Platelets, therefore, might play an immuno-modulatory role in the pathogenesis and pathophysiology of ITP. In this respect, we propose several possible pathways in which platelets themselves may participate in the immune response in ITP. First, we will elaborate on how platelets might directly promote inflammation or stimulate immune responses in ITP. Second, we will discuss two ways in which platelet microparticles (PMPs) might contribute to the disrupted immune balance and impaired thrombopoiesis by megakaryocytes in ITP. Importantly, from these insights, new starting points for further research and for the design of potential future therapies for ITP can be envisioned.

New treatments for primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an autoimmune disease leading to a decreased platelet count and an ensuing haemorrhagic risk. First-line treatment against ITP consists in the administration of immunomodulators aimed at decreasing platelet destruction. Up to 70% of individuals with an ITP diagnosis treated with corticosteroids do not achieve a clinical response or demonstrate a high relapse rate, requiring treatment to prevent a haemorrhagic risk. Less than 30% of patients treated with thrombopoietin analogues, 60% of those treated with splenectomy and 20% of those treated with rituximab reach sustained remission in the absence of treatment. Because of these reasons, it is unquestionable that treatment of patients with ITP should be optimized. Through this study, we will review new actual and future options of treatment.

Immune Thrombocytopenia: Recent Advances in Pathogenesis and Treatments

Immune thrombocytopenia (ITP) is a rare autoimmune disease due to both a peripheral destruction of platelets and an inappropriate bone marrow production. Although the primary triggering factors of ITP remain unknown, a loss of immune tolerance-mostly represented by a regulatory T-cell defect-allows T follicular helper cells to stimulate autoreactive splenic B cells that differentiate into antiplatelet antibody-producing plasma cells. Glycoprotein IIb/IIIa is the main target of antiplatelet antibodies leading to platelet phagocytosis by splenic macrophages, through interactions with Fc gamma receptors (FcγRs) and complement receptors. This allows macrophages to activate autoreactive T cells by their antigen-presenting functions. Moreover, the activation of the classical complement pathway participates to platelet opsonization and also to their destruction by complement-dependent cytotoxicity. Platelet destruction is also mediated by a FcγR-independent pathway, involving platelet desialylation that favors their binding to the Ashwell-Morell receptor and their clearance in the liver. Cytotoxic T cells also contribute to ITP pathogenesis by mediating cytotoxicity against megakaryocytes and peripheral platelets. The deficient megakaryopoiesis resulting from both the humoral and the cytotoxic immune responses is sustained by inappropriate levels of thrombopoietin, the major growth factor of megakaryocytes. The better understanding of ITP pathogenesis has provided important therapeutic advances. B cell-targeting therapies and thrombopoietin-receptor agonists (TPO-RAs) have been used for years. New emerging therapeutic strategies that inhibit FcγR signaling, the neonatal Fc receptor or the classical complement pathway, will deeply modify the management of ITP in the near future.