Pathophysiology Of Immune Thrombocytopenia Research Articles

Trogocytosis: A potential pathogenic mechanism in immune thrombocytopenia leading to impaired megakaryocyte maturation and reduced platelet production

Immune thrombocytopenia (ITP) is an autoimmune disease due to increased peripheral platelets destruction and inappropriate bone marrow production of platelets by megakaryocytes (MKs). The pathophysiology of ITP is complex and multifactorial, which remains not fully understood. However, the production of antiplatelet autoantibodies and the destruction of antibody-coated platelets through antibody-dependent cellular phagocytosis by macrophages (Mθ) expressing Fc gamma receptor (FcγR) are regarded as the key mechanisms. Glycoprotein (GP) Ⅱb/Ⅲa is the main target of antiplatelet antibodies leading to platelet phagocytosis by splenic Mθ, through interactions with FcγR. As GPⅡb/Ⅲa is normally expressed both on platelets and the MKs from which they are derived, we inferred that partial phagocytosis (definitely trogocytosis) of MKs by bone marrow Mθ might exist, leading to the increased amount of granular MKs (or non-platelets-producing MKs) in ITP. And we further hypothesized that the “bitten” MKs cannot sustain their normal function of maturation. Such trogocytosis mechanism may shed new light on the understanding of morphology alterations, maturation defects and decreased platelets production of MKs in ITP, and provide appealing implications in therapeutic modifications targeting the interplay of MKs and Mθ in bone marrow.

Obesity is associated with adverse outcomes in primary immune thrombocytopenia - a retrospective single-center study

The pathophysiology of immune thrombocytopenia (ITP) involves immune-mediated platelet destruction. The presence of adipose tissue in obese individuals creates an inflammatory environment that could potentially impact the clinical course and outcomes of ITP. However the relationship between obesity and ITP outcomes has not been well described. We evaluated ITP outcomes in 275 patients diagnosed with primary ITP from 2012 to 2022. Patients were categorized into four groups based on their body mass index (BMI) at diagnosis. Female gender was associated with a lower platelet count at the time of diagnosis at any BMI. Patients with high BMI had lower platelet counts at diagnosis and at platelet nadir (p < 0.001), an increased likelihood of requiring therapy (p < 0.001) and requiring multiple lines of therapy (p = 0.032). Non-obese patients who required corticosteroid treatment experienced a longer remission duration compared to obese patients (p = 0.009) and were less likely to be steroid-dependent (p = 0.048). Our findings suggest that obesity may be a significant risk factor for developing ITP and for ITP prognosis. Future studies are needed to evaluate the role of weight loss intervention in improving ITP outcomes.

Pathophysiology, Clinical Manifestations and Diagnosis of Immune Thrombocytopenia: Contextualization from a Historical Perspective.

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by an isolated decrease in the 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 impaired central megakaryopoiesis and platelet production in the bone marrow. Here, we intend to contextualize the current knowledge on the pathophysiology, terminology, epidemiology, clinical manifestations, diagnosis, and prognosis of ITP from a historical perspective and the first references to the never-stopping garnering of knowledge about this entity. We highlight the necessity to better understand ITP in order to be able to provide ITP patients with personalized treatment options, improving disease prognosis and reducing the incidence or frequency of refractoriness.

Complications of thrombopoietin receptor agonists therapy in patients with immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by increased platelet destruction and decreased platelet production. The formation of antibodies to platelet and megakaryocyte glycoproteins plays a major role in the pathophysiology of ITP. All treatment strategies for ITP attempt to increase platelet count and reduce the risk of bleeding complications. Corticosteroids remain the most commonly used first-line therapy for ITP, but their long-term use is limited due to the development of severe complications. Today the new treatment methods including the use of thrombopoietin receptor agonists (TPO-RA) romiplostim, eltrombopag and avatrombopag with a number of advantages over standard therapy are of great interest. These drugs are recommended for use in the second-line therapy and show high efficacy in patients with ITP, particularly in real clinical practice. In most cases TPO-RA provide stable and long-term remission of the disease, allowing you to reduce or discontinue the use of glucocorticosteroids and avoid splenectomy. Many studies of the mechanism of action, efficacy and toxicity of TPO-RA have been performed. the research results significantly expand our knowledge about these agents. This review provides comparative data of the TPO-RA safety and the main aspects of their clinical use. The features of the new drug avatrombopag, recently approved for use in the Russian federation, are described. the overview presents the advantages and limitations of each drug, possible adverse events and methods for their control.

Prevalence of anti-glycoprotein V in patients with primary immune thrombocytopenia

Background Glycoprotein (GP) V is a well-characterized immune target in Varicella-associated and drug-induced thrombocytopenia. Recent studies have focused on the involvement of anti-GP V in the mechanism of platelet clearance as a recent paradigm in the pathophysiology of immune thrombocytopenia (ITP), rather than other anti-GPs like GP IIb/IIIa, GP Ib/IX and less frequently GP Ia/IIa. Objectives This study was conducted to determine the prevalence of anti-GP V in adult ITP Egyptian patients and to detect its impact on the outcome in these patients. Patients and methods This was a cross-sectional study in which, using enzyme-linked immunosorbent assay, the level of serum anti-GP antibodies V was measured in the peripheral blood of 90 patients with primary ITP compared with 20 age-matched and sex-matched normal healthy controls and its relationship with clinical, laboratory parameters, and response to treatment. Results Our study revealed that anti-GP antibodies V level in the cases group was statistically significantly higher as compared with the control group (P=0.005). There was weak statistically significant positive correlation between platelet count and anti-GP V level antibodies in the cases group after treatment with a P value of 0.0548. However, the level of anti-GP V did not show significant correlation with the bleeding score (P=0.123), degree of thrombocytopenia (P=0.967), sex (P=0.067), bone marrow findings (P=0.448), spleen size (P=0.992), or with the response to steroid therapy (P=0.171). Conclusion This study points out that GP V is a frequent immune target in ITP and that the detection of GP-specific autoantibodies being of value in the pathogenesis of ITP. We recommend that further studies including GP V are required before ITP treatment can be tailored according to platelet autoantibody specificity.

A Phase III Clinical Trial Program Investigating the Efficacy and Safety of Ianalumab in Patients with Primary Immune Thrombocytopenia (VAYHIT1 and VAYHIT2) and Warm Autoimmune Hemolytic Anemia (VAYHIA)

Background: Immune thrombocytopenia (ITP) and warm autoimmune hemolytic anemia (wAIHA) are characterized by autoantibody destruction of platelets and red blood cells, respectively. Autoreactive B cells play a role in the pathophysiology of ITP and wAIHA. Serum levels of B-cell activating factor (BAFF) are elevated in these disorders and correlate with increased disease activity. Ianalumab is a novel, fully human immunoglobulin G1 monoclonal antibody that targets BAFF receptor (BAFF-R) and has a unique dual mechanism of action: direct antibody-dependent cellular cytotoxicity-mediated B-cell depletion and inhibition of B-cell differentiation, proliferation and survival via blockade of BAFF-R-mediated signaling. Corticosteroids (CS) are the standard first-line treatment for ITP; however, few patients achieve a long-term response. Additionally, extended and recurrent use of CS is associated with substantial toxicity. Thrombopoietin receptor agonists (TPO-RAs), such as eltrombopag, are commonly used second-line ITP treatments and often achieve a response; however, responses are rarely maintained once treatment ends, so chronic administration is typically required. For wAIHA, few treatments have been approved, and patients rarely achieve durable responses on CS or off-label rituximab. Thus, there are significant unmet needs for patients with ITP or wAIHA. Aim: We report the designs of the randomized, double-blind, multicenter, 3-arm Phase III VAYHIT1 (NCT05653349), VAYHIT2 (NCT05653219) and VAYHIA (NCT05648968) trials. The trials aim to assess whether ianalumab, working with a distinct and complementary mechanism to standard-of-care treatments, can induce durable responses in patients with ITP or wAIHA. Trial designs: VAYHIT1 and VAYHIT2 will assess the efficacy and safety of ianalumab vs placebo in addition to first-line CS and short-term eltrombopag, respectively, in adults with primary ITP. In both trials, patients will be randomized 1:1:1 to intravenous (IV) low-dose ianalumab, high-dose ianalumab or placebo every 4 weeks (wks). The primary endpoint in both trials is the time from randomization to treatment failure, defined as platelet count &amp;lt;30 G/L later than 8 wks from randomization, need for rescue treatment later than 8 wks from randomization, start of a new ITP therapy, or death. In VAYHIT2, ineligibility to taper or inability to discontinue eltrombopag after the completion of treatment with ianalumab or placebo will also be assessed as treatment failure. Secondary endpoints include response rate, complete response rate and safety ( Table). VAYHIA will assess the efficacy and safety of ianalumab vs placebo in adults with wAIHA who have failed ≥1 treatment. Patients will be randomized 1:1:1 to IV low-dose ianalumab, high-dose ianalumab or placebo every 4 wks. Selected supportive care is allowed. The primary endpoint is durable hemoglobin (Hb) response, defined as Hb ≥10 g/dL and an Hb increase of ≥2 g/dL from baseline for ≥8 consecutive wks between Wk 9 and Wk 25 in the absence of rescue or prohibited treatment. The key secondary endpoint is duration of durable Hb response ( Table). An optional open-label crossover period will allow patients who receive placebo and do not achieve a durable Hb response to receive high-dose ianalumab. Patients from all 3 trials will be monitored for efficacy until treatment failure (or up to 39 months after the last patient was randomized, whichever comes first) and safety for up to 2 years. Conclusions: These trials have been designed based on the hypothesis that, when administered early in disease progression, medical therapy targeting complementary physiological pathways may restore self-tolerance in patients with ITP and wAIHA. Ianalumab in combination with standard of care is expected to safely induce a high response rate that will be maintained beyond treatment completion. Ianalumab may address the unmet needs for patients with ITP and wAIHA. Current status: At the time of writing, VAYHIT1, VAYHIT2 and VAYHIA are recruiting. The open-label, single-arm, Phase II VAYHIT3 trial is also assessing ianalumab in patients with primary ITP previously treated with at least 1 CS and 1 TPO-RA (NCT05885555).

Ianalumab, a Novel Anti-B-Cell Activating Factor (BAFF) Receptor (BAFF-R) Monoclonal Antibody (mAb) in Development for Immune Thrombocytopenia (ITP) and Warm Autoimmune Hemolytic Anemia (wAIHA), Has Demonstrated a Favorable Safety Profile in Sjögren's Syndrome (SjS), Systemic Lupus Erythematosus (SLE) and Chronic Lymphocytic Leukemia (CLL)

Background: Current therapies for ITP and wAIHA are mostly symptomatic and rarely lead to durable responses after discontinuation; thus, chronic treatment is often needed, which may be associated with toxicity and substantial quality-of-life burden for patients. There is an unmet need for disease-modifying therapies that can induce and maintain durable responses beyond treatment completion in ITP and wAIHA. BAFF is an important regulator of B-cell differentiation, proliferation and survival through interactions with BAFF-R. Autoreactive B cells play a key role in the pathophysiology of ITP and wAIHA and are fueled by increased BAFF pathway activity; therefore, there is a strong rationale for investigating BAFF-R as a target in both diseases. Ianalumab is a fully human mAb that targets BAFF-R. It has a novel dual mechanism of action: blockade of BAFF-R-mediated signaling and potent depletion of B cells mediated by antibody-dependent cellular cytotoxicity. Ianalumab has shown favorable safety and encouraging efficacy in other indications, including SjS, SLE and CLL, and is a promising potential treatment for ITP and wAIHA. As ianalumab is being investigated in ongoing, blinded Phase III trials in ITP and wAIHA, we present the safety profile of ianalumab from completed Phase I/II studies in SjS, SLE or CLL. Methods: Data for patients with SjS were from a randomized Phase IIb trial (NCT02962895); patients (N=190) received subcutaneous (SC) placebo or ianalumab 5, 50 or 300 mg every 4 weeks (wks) for 24 wks. Patients then entered a second treatment period; patients in the ianalumab 5 or 50 mg arm continued the same dose, patients in the ianalumab 300 mg arm were randomized to continue the same dose or receive placebo, and patients in the placebo arm switched to ianalumab 150 mg. Safety data in patients with SLE were collected from a randomized Phase II trial (NCT03656562). Patients (N=67) received SC ianalumab 300 mg or placebo every 4 wks for 28 wks; patients in the placebo group could switch to ianalumab in a 20-wk open-label extension. Data for patients with CLL were from a Phase Ib trial (NCT03400176); patients (N=32) received intravenous (IV) ianalumab 0.3, 1, 3 or 9 mg/kg every 2 wks plus ibrutinib 420 mg once daily for up to 8 28-day cycles. Safety assessments included adverse events (AEs), serious AEs (SAEs) and AEs of special interest. Results: Ianalumab was safe and well tolerated in patients with SjS. Most AEs were mild or moderate in severity; severe AEs were reported in 5 patients receiving ianalumab. Three ianalumab-treated patients had SAEs; 2 SAEs in 1 patient (appendicitis and tubo-ovarian abscess) were considered related to ianalumab treatment. Frequency of infections/infestations was similar between patients treated with ianalumab and placebo. Discontinuation rates were low, with only 4 patients discontinuing ianalumab for non-serious AEs (infection [n=2], lymphopenia, local injection-site reaction [n=1 each]); no SAEs led to treatment discontinuation. Ianalumab continued to be well tolerated in the second treatment period. There were no dose-dependent differences in the rate of AEs except for injection-site reactions (mostly local and not severe). In ianalumab-treated patients with SLE, there were no serious infections during the blinded period; only 1 SAE (renal impairment) was reported. In the open-label extension, 4 SAEs were reported. No SAEs in the blinded period or open-label extension were considered treatment related. Most AEs in patients with CLL were Grade 1 or 2 and not correlated with dose. Twelve patients experienced Grade ≥3 AEs; decreased neutrophil count (n=5) was most common. No dose-limiting toxicities were reported. Discussion: Data from patients with SjS, SLE or CLL receiving ianalumab for up to 52 wks show it has a favorable safety profile. There was a low risk of infections irrespective of dosing regimen. No cases of hypogammaglobulinemia were clinically significant in any trial. New treatments are needed for ITP and wAIHA that have disease-modifying potential and allow patients to achieve and maintain high response rates after a short therapeutic course. Ianalumab has the potential to address this unmet need and is currently being assessed as an IV dose every 4 wks in Phase III trials as both a first- (VAYHIT1 [NCT05653349]) and second-line (VAYHIT2 [NCT05653219]) treatment for ITP and as a second-line treatment for wAIHA (VAYHIA [NCT05648968]).

Novel therapeutics and future directions for refractory immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder affecting approximately 1 in 20 000 people. While most patients with ITP are successfully managed with the current set of standard and approved therapeutics, patients who cannot be adequately managed with these therapies, considered to have refractory ITP, are not uncommon. Therefore, there remains an ongoing need for novel therapeutics and drug development in ITP. Several agents exploiting novel targets and mechanisms in ITP are presently under clinical development, with trials primarily recruiting heavily pretreated patients and those with otherwise refractory disease. Such agents include the neonatal Fc receptor antagonist efgartigimod, the Bruton tyrosine kinase inhibitor rilzabrutinib, the complement inhibitors sutimlimab and iptacopan and anti-CD38 monoclonal antibodies such as daratumumab and mezagitamab, among others. Each of these agents exploits therapeutic targets or other aspects of ITP pathophysiology currently not targeted by the existing approved agents (thrombopoietin receptor agonists and fostamatinib). This manuscript offers an in-depth review of the current available data for novel therapeutics in ITP presently undergoing phase 2 or 3 studies in patients with heavily pretreated or refractory ITP. It additionally highlights the future directions for drug development in refractory ITP, including discussion of innovative clinical trial designs, health-related quality of life as an indispensable clinical trial end-point and balancing potential toxicities of drugs with their potential benefits in a bleeding disorder in which few patients suffer life-threatening bleeding.

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.

When immune thrombocytopenia gets on your nerves: β2-adrenergic receptor agonists as a potential treatment?

When immune thrombocytopenia gets on your nerves: β2-adrenergic receptor agonists as a potential treatment?

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.

Recent progress in immune thrombocytopenia pathophysiology and treatment

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by increased platelet destruction and impaired platelet production from bone marrow megakaryocytes. The details of different platelet destruction mechanisms resulting from differences in autoantibodies and autoantibody-independent direct platelet destruction remain unclear although antiplatelet autoantibodies directed against platelet glycoproteins, such as GPIIb/IIIa and GPIb, play a central role in ITP pathogenesis. ITP is diagnosed by excluding other causes of thrombocytopenia due to the lack of standard tests or biomarkers for its confirmation. Plasma thrombopoietin level measurement and reticulated platelet ratio are useful in distinguishing the cause of thrombocytopenia and will be included in the new "Diagnostic reference guide of adult immune thrombocytopenia." Currently, the treatment of refractory chronic ITP is mainly based on thrombopoietin receptor agonists, but ITP drugs with novel mechanisms of action are actively developed. New therapeutic agents are expected to be selected based on an accurate diagnosis and tailored to the pathophysiology of each case in ITP treatment.

Recent topics in the pathophysiology and treatment of immune thrombocytopenic purpura

Increased and impaired platelet productions via immunological abnormalities are the main pathophysiological mechanisms of primary immune thrombocytopenia (ITP). Recent studies have revealed that platelet removal from circulation involves not only Fc receptor-mediated phagocytosis of immunoglobulin G autoantibodies-bound platelets but also complement-dependent mechanism and platelet glycoprotein desialylation. Understanding the molecular mechanism of ITP pathophysiology has helped develop many novel molecular targeted drugs, and recent clinical trials have shown their effectiveness. In particular, fostamatinib, which is a Syk inhibitor, inhibits macrophage and B-cell activity and is already been approved in Europe for multidrug-resistant ITP. Recently, coronavirus disease-2019 (COVID-19) vaccine-associated newly-onset or ITP exacerbation has come to attention. Whether COVID-19 vaccines induce de novo ITP remains controversial. However, close attention is necessary after COVID-19 vaccination because a certain number of patients with ITP presented exacerbation after COVID-19 vaccination.

Uncovering Transcriptome Characteristics in Bone Marrow Hematopoiesis in Immune Thrombocytopenia at Single-Cell Resolution

Immune thrombocytopenia (ITP) is an autoimmune disorder, in which megakaryocyte dysfunction caused by an autoimmune reaction can lead to thrombocytopenia, although the underlying mechanisms remain unclear. Here, we hypothesized that bone marrow (BM) CD34+ hematopoietic stem and progenitor cells (HSPCs) participated in the defective megakaryogenesis in ITP patients, and we performed single-cell RNA-seq (scRNA-seq) of BM CD34+ HSPCs to reveal the overall transcriptome alterations in HSPCs in ITP. Dimensional reduction using uniform manifold approximation and projection (UMAP) showed the effective integration of the datasets from different samples. We manually annotated the cell clusters into 17 different cell types with distinct gene expression patterns. By performing differential expression analysis, enrichment analysis, trajectory analysis, transcriptional regulatory network analysis and cell-cell interaction analysis, we found that gene expression, transcriptional regulatory networks and cell-cell interactions varied in HSPCs of ITP, particularly in a pre-B cell population and natural killer/T cell progenitors, highlighting the selective immune aberration associated with defective megakaryopoiesis in ITP. Differentially expressed gene (DEG) analysis indicated that the top upregulated genes in a megakaryocytic progenitors (MkP) population of ITP were associated with erythropoiesis, suggesting a bias toward erythrocytes in megakaryopoiesis in ITP. Moreover, Flow cytometry confirmed that the number of CD9+ cells from CD34+ HSPCs decreased in ITP. Liquid culture assays demonstrated that CD9+ CD34+ HSPCs from healthy controls tended to differentiate into megakaryocytes; however, this tendency was not observed in ITP patients. The percentage of megakaryocytes differentiated from CD9+CD34+ HSPCs was higher than that of the CD9- counterparts from healthy controls, whereas in ITP patients, the percentage decreased to only 1/4th of that in the healthy controls and was comparable to that from the CD9- HSPCs, indicating that differentiation of CD9+ HSPCs toward the megakaryopoietic lineage was impaired in ITP. Further analysis revealed the universality of their heterogeneity and provided an analytical basis for the study of megakaryocyte-related diseases, including ITP. Enrichment analysis confirmed the definition of MkP in our ITP integrated dataset. To further analyze the transcriptional difference between ITP and HC, we pooled MkP from all samples. The expression of several molecular features of MkP was visualized, and seven transcriptionally heterogeneous subpopulations of MkP were identified. We then assessed the expression of marker genes in each subpopulation and characterized the gene sets enriched in different clusters, which showed pronounced heterogeneity within MkP, consistent with the results of previous analyses of MkP/Mk from multi-hematopoietic tissues. We evaluated ITP-associated DEGs in each MkP subcluster, and we found that most of these DEGs were subtype-specific, indicative of the subtype-specific effects of the disorder. In summary, this study dissects the significant heterogeneity and disease characteristics of BM CD34+ HSPCs from ITP patients at single-cell resolution, revealing new insights regarding the pathophysiology of ITP.

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.

The 4 T's of ITP: Tailoring Therapies to Treat Thrombocytopenia.

Immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder characterized by the destruction of platelets and megakaryocytes. Its management has changed significantly in recent years, and at JADPRO Live Virtual 2021, David Hughes, PharmD, BCOP, reviewed the background and pathophysiology of ITP and clinical practice guidelines with an emphasis on patient preference when selecting first and subsequent lines of therapies in the chronic ITP setting.

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.

Anti-glycoprotein antibodies and sequestration pattern of indium-labeled platelets in immune thrombocytopenia

AbstractAntiglycoprotein (anti-GP) antibodies play an important role in the pathophysiology of immune thrombocytopenia (ITP). The sequestration pattern of platelets in the spleen and liver can be studied with 111In-labeled autologous platelet scans. No studies have investigated the role of anti-GP antibodies in sequestration patterns in ITP patients. In this study, we examined the association between antibodies and (1) platelet sequestration site and (2) clearance rate of platelets. All ITP patients receiving an 111In-labeled autologous platelet study between 2014 and 2018 were included. Antibodies were measured using the direct MAIPA method to determine the presence and titer of anti-GPIIb/IIIa, anti-GPIb/IX, and anti-GPV antibodies. Multivariate regression models were used to study the association between anti-GP antibodies, sequestration site, and clearance rate. Seventy-four patients were included, with a mean age of 36 years. Forty-seven percent of the patients showed a predominantly splenic sequestration pattern, 29% mixed, and 25% a hepatic pattern. In 53% of the patients, anti-GP antibodies were detected. Regression models showed a significant association between splenic sequestration and GPV autoantibodies. Furthermore, in patients where antibodies were present, the clearance rate was higher in patients with a splenic sequestration. Anti-GPV antibodies are associated with a splenic sequestration pattern in ITP patients. These associations provide insight into the possible pathophysiological mechanisms of ITP, which may lead to better detection and treatment of this partly idiopathic and prevalent disease.

Novel therapies for immune thrombocytopenia.

Current therapies for immune thrombocytopenia (ITP) are successful in providing a haemostatic platelet count in over two-thirds of patients. Still, some patients have an inadequate response and there is a need for other therapies. A number of novel therapies for ITP are currently being developed based upon the current pathophysiology of ITP. Many therapies are targetted at reducing platelet destruction by decreasing anti-platelet antibody production by immunosuppression with monoclonal antibodies targetted against CD40, CD38 and the immunoproteasome or physically reducing the anti-platelet antibody concentration by inhibition of the neonatal Fc receptor. Others target the phagocytic system by inhibiting FcγR function with staphylococcal protein A, hypersialylated IgG, polymeric Fc fragments, or Bruton kinase. With a recognition that platelet destruction is also mediated by complement, inhibitors of C1s are also being tested. Inhibition of platelet desialylation may also play a role. Other novel therapies promote platelet production with new oral thrombopoietin receptor agonists or the use of low-level laser light to improve mitochondrial activity and prevent megakaryocyte apoptosis. This review will focus on these novel mechanisms for treating ITP and assess the status of treatments currently under development. Successful new treatments for ITP might also provide a pathway to treat other autoimmune disorders.

Increasing numbers of CD19 + CD24highCD38high regulatory B cells and pre-germinal center B cells reflect activated autoimmunity and predict future treatment response in patients with untreated immune thrombocytopenia.

The pathophysiology of immune thrombocytopenia (ITP) is poorly understood, particularly aspects regarding abnormal homeostasis and dysregulation of B cells. In this study, we analyzed peripheral lymphocyte subsets in patients with untreated ITP and healthy controls, and examined correlations between cell percentages/counts and titers of serum cytokines and antibodies. We also compared ITP patients who later required second-line therapies and those who did not. The percentages of CD19 + CD24highCD38high regulatory B cells, pre-germinal center (GC) B cells, and plasmablast-like B cells were significantly higher in ITP patients than in healthy controls. Absolute counts of regulatory B cells and pre-GC B cells were significantly higher in those who needed second-line therapies. In addition, serum B cell-activating factor belonging to the tumor necrosis factor family (BAFF) levels and platelet-associated immune globulin G antibody titers correlated positively with regulatory B cell, pre-GC B cell, and auto-reactive B cell counts. Serum interferon-α (IFN-α) levels were elevated in four ITP patients with high auto-reactive B cell counts. These results indicate that increases in regulatory B cells and pre-GC B cells may reflect activated autoimmunity induced by BAFF and/or IFN-α. Consequently, evaluation of B cell subsets in untreated ITP patients may predict treatment response.