Refractory Immune Thrombocytopenia Research Articles

Pediatric refractory chronic immune thrombocytopenia: Identification, patients' characteristics, and outcome.

Refractory chronic immune thrombocytopenia (r-cITP) is one of the most challenging situations in chronic immune thrombocytopenia (cITP). Pediatric r-cITP is inconsistently defined in literature, contributing to the scarcity of data. Moreover, no evidence is available to guide the choice of treatment. We compared seven definitions of r-cITP including five pediatric definitions in 886 patients with cITP (median [min-max] follow-up 5.3 [1.0-29.3] years). The pediatric definitions identified overlapping groups of various sizes (4%-20%) but with similar characteristics (higher proportion of immunopathological manifestations [IM] and systemic lupus erythematosus [SLE]), suggesting that they adequately captured the population of interest. Based on the 79 patients with r-cITP (median follow-up 3.1 [0-18.2] years) according to the CEREVANCE definition (≥3 second-line treatments), we showed that r-cITP occurred at a rate of 1.15% new patients per year and did not plateau over time. In multivariate analysis, older age was associated with r-cITP. One patient (1%) experienced two grade five bleeding events after meeting r-cITP criteria and while not receiving second-line treatment. The cumulative incidence of continuous complete remission (CCR) at 2 years after r-cITP diagnosis was 9%. In this analysis, splenectomy was associated with a higher cumulative incidence of CCR (hazard ratio: 5.43, 95% confidence interval: 1.48-19.84, p = 7.8 × 10-4). In sum, children with cITP may be diagnosed with r-cITP at any time point of the follow-up and are at increased risk of IM and SLE. Second-line treatments seem to be effective for preventing grade 5 bleeding. Splenectomy may be considered to achieve CCR.

Efficacy and safety of human umbilical cord-derived mesenchymal stem cells in the treatment of refractory immune thrombocytopenia: a prospective, single arm, phase I trial

Patients with refractory immune thrombocytopenia (ITP) frequently encounter substantial bleeding risks and demonstrate limited responsiveness to existing therapies. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) present a promising alternative, capitalizing on their low immunogenicity and potent immunomodulatory effects for treating diverse autoimmune disorders. This prospective phase I trial enrolled eighteen eligible patients to explore the safety and efficacy of UC-MSCs in treating refractory ITP. The research design included administering UC-MSCs at escalating doses of 0.5 × 106 cells/kg, 1.0 × 106 cells/kg, and 2.0 × 106 cells/kg weekly for four consecutive weeks across three cohorts during the dose-escalation phase, followed by a dose of 2.0 × 106 cells/kg weekly for the dose-expansion phase. Adverse events, platelet counts, and changes in peripheral blood immunity were monitored and recorded throughout the administration and follow-up period. Ultimately, 12 (with an addition of three patients in the 2.0 × 106 cells/kg group due to dose-limiting toxicity) and six patients were enrolled in the dose-escalation and dose-expansion phase, respectively. Thirteen patients (13/18, 72.2%) experienced one or more treatment emergent adverse events. Serious adverse events occurred in four patients (4/18, 22.2%), including gastrointestinal hemorrhage (2/4), profuse menstruation (1/4), and acute myocardial infarction (1/4). The response rates were 41.7% in the dose-escalation phase (5/12, two received 1.0 × 106 cells/kg per week, and three received 2.0 × 106 cells/kg per week) and 50.0% (3/6) in the dose-expansion phase. The overall response rate was 44.4% (8/18) among all enrolled patients. To sum up, UC-MSCs are effective and well tolerated in treating refractory ITP (ClinicalTrials.gov ID: NCT04014166).

The Challenge for a Correct Diagnosis of Refractory Thrombocytopenia: ITP or MDS with Isolated Thrombocytopenia?

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by isolated thrombocytopenia. It is diagnosed in patients with a platelet count below 100,000 per cubic millimeter in whom other causes of thrombocytopenia have been ruled out, and its diagnosis is generally one of exclusion. Clinical manifestations of patients may vary from asymptomatic disease to mild mucocutaneous or life-threatening bleeding. Glucocorticoids are used as first-line treatment for ITP, while other second-line medications, mainly thrombopoietin-receptor agonists (TPO-RA) and rituximab, are given to patients in whom ITP does not remit, or relapses soon after glucocorticoid treatment. Refractoriness of ITP strongly questions its diagnosis and necessitates a thorough clinical and laboratory work-up to decide whether that is the case of refractory ITP or a misdiagnosis. The aim of this review is to summarize the conditions associated with isolated thrombocytopenia and highlight the characteristics of confusing cases. Even though the case of a myelodysplastic syndrome presented with isolated thrombocytopenia (MDS-IT) is relatively rare and not well-established in the literature, it constitutes one of the most predominant misdiagnoses of refractory ITP. MDS-IT patients are thought to present with multilineage dysplasia, normal karyotype and low risk prognostic score, based on IPSS-R. It has been shown that a significant proportion of MDS-IT patients are misdiagnosed as having the more common ITP. Therefore, it is crucial that in confusing cases of persistent thrombocytopenia a detailed diagnostic work-up is applied-including evaluation of peripheral-blood smear, bone marrow examination and cytogenetic testing-to avoid unnecessary therapy delay.

Novel Perspectives on Thrombopoietin Receptor Agonists Applications.

Second-generation thrombopoietin receptor agonists (TPO-RAs), romiplostim, eltrombopag, and avatrombopag, have been proved to be significant stimulators of megakaryopoiesis and, in the last decade, they have been incorporated in the treatment options against refractory immune thrombocytopenia in children and adults that do not respond to conventional therapy. Additionally, given their beneficial impact on hematopoiesis, they have successfully been applied in cases of non-immune thrombocytopenia, such as aplastic anemia, HCV-related thrombocytopenia, chronic liver disease, and most recently acute radiation syndrome. During the past years, a wide variety of clinical studies have been performed, in regard to the use of TPO-RAs in various thrombocytopenic settings, such as malignant hematology and hematopoietic stem cell transplantation, hereditary thrombocytopenias, and chemotherapy-treated patients with solid organ tumors. Although data indicate that TPO-RAs may be an effective and safe option for managing disease- or treatment-related thrombocytopenia in these patients, further research is needed to determine their efficacy and safety in these settings. Furthermore, recent studies have highlighted novel properties of TPO-RAs that render them as potential treatment candidates for reducing tumor burden or fighting infections. Herein, we discuss the potential novel applications of TPO-RAs and focus on data regarding their efficacy and safety in these contexts.

Effectiveness and safety of eltrombopag in connective tissue disease patients with refractory immune thrombocytopenia: a retrospective study.

We aimed to investigate the safety and effectiveness of eltrombopag for adult patients with refractory immune thrombocytopenia (ITP) secondary to connective tissue disease (CTD). This is a single-centre, retrospective cohort and propensity score-matched study. Data from CTD-ITP patients treated with eltrombopag between January 2019 and January 2023 were retrospectively analysed. Baseline characteristics and follow-up information were recorded. CTD patients without ITP were matched to identify the risk factors associated with CTD-ITP performed by Logistic regression analysis. Twenty patients were enrolled, including 5 systemic lupus erythematosus (SLE), 9 Sjögren's syndrome (SS) and 6 undifferentiated connective tissue disease (UCTD). Nineteen (95%) patients were female, and the median age was 59 years. Logistic regression analysis showed that anaemia (OR = 8.832, P = 0.007) was associated with increased risk of ITP, while non-erosive arthritis (OR = 0.045, P = 0.001) and interstitial lung disease (OR = 0.075, P = 0.031) were associated with reduced risk. Fourteen patients (70%) achieved a complete response (CR) and one (5%) achieved a partial response (PR). The median response time was 14 days. The median platelet count was 8.5 × 109/l at baseline of eltrombopag and increased to 122 × 109/l after 4 weeks. No adverse events were observed. Eltrombopag appears to be effective, safe and well-tolerated in refractory ITP patients with CTD; larger studies are needed to confirm the generalizability of these findings.

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

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

GPIbα CAAR-T cells function like a Trojan horse to eliminate autoreactive B cells to treat immune thrombocytopenia.

Breakthrough treatment for refractory and relapsed immune thrombocytopenia (ITP) patients is urgently needed. Autoantibody-mediated platelet clearance and megakaryocyte dysfunction are important pathogenic mediators of ITP. Glycoprotein (GP) Ibα is a significant autoantigen found in ITP patients and is associated with poor response to standard immunosuppressive treatments. Here, we engineered human T cells to express a chimeric autoantibody receptor (CAAR) with GPIbα constructed into the ligand-binding domain fused to the CD8 transmembrane domain and CD3ζ-4-1BB signaling domains. We performed cytotoxicity assays to assess GPIbα CAAR-T-cell selective cytolysis of cells expressing anti-GPIbα B-cell receptors (BCRs) in vitro. Furthermore, we demonstrated the potential of GPIbα CAAR-T cells to persist and precisely eliminate GPIbα-specific B cells in vivo. In summary, we present a proof of concept for CAAR-T-cell therapy to eradicate autoimmune B cells while sparing healthy B cells with GPIbα CAAR-T cells that function like a Trojan horse. GPIbα CAAR-Tcell therapy is a promising treatment for refractory and relapsed ITP patients.

Rituximab alleviates pediatric systemic lupus erythematosus associated refractory immune thrombocytopenia: a case-based review.

A complication of pediatric systemic lupus erythematosus (pSLE) is immune thrombocytopenia (ITP). Although corticosteroids and immunoglobulins are frequently used as preliminary treatments, some patients do not respond to them. Rituximab has been reported to be safe and effective in the treatment of pSLE complicated with refractory ITP. Research is currently underway to determine the optimal rituximab dose for these individuals. We report a case of a child with SLE-associated ITP (SLE-ITP) who was successfully treated with rituximab. Rituximab is likely the most viable therapeutic option for refractory SLE-ITP. Furthermore, a comprehensive review of the relevant literature was performed and a concise overview of the pathogenesis and available treatment modalities for pediatric patients diagnosed with SLE and concurrent ITP was provided.

Efficacy and Safety of Fostamatinib in Refractory Immune Thrombocytopenia: A Meta-analysis from Randomized Controlled Trials

Efficacy and Safety of Fostamatinib in Refractory Immune Thrombocytopenia: A Meta-analysis from Randomized Controlled Trials

Abstract B030: Intracerebral and intraventricular hemorrhage due to severe thrombocytopenia: A rare case of Evans syndrome

Abstract Introduction: Evans syndrome (ES) is a rare autoimmune disorder characterized by the development of autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), and/or immune neutropenia (AIN) without an identifiable cause. It is believed to involve immune system dysregulation, leading to the destruction of red blood cells, platelets, and neutrophils. Case Presentation: A 68-year-old male with a history of coronary artery disease, hypertension, diabetes, and atrial fibrillation presented with abdominal pain and diarrhea. Laboratory tests revealed a platelet count of 3k, suggesting ITP. Initial treatment with dexamethasone and platelet transfusion provided limited improvement. A bone marrow biopsy showed mildly hypercellular bone marrow with trilineage hematopoiesis. However, the patient's condition rapidly deteriorated, and he returned to the emergency department with severe symptoms, including headache, gum bleeding, and lower extremity petechiae. A CT scan revealed a large intraparenchymal hematoma with intraventricular hemorrhage, highlighting the risk of life-threatening bleeding in ES patients. Discussion: The patient was managed with platelet transfusions, high-dose steroids, and intravenous immunoglobulin (IVIG), which provided temporary relief but failed to maintain stable platelet levels. Further investigations revealed a positive antinuclear antibody (ANA), suggesting an underlying rheumatological condition and confirming the diagnosis of secondary ES. This finding necessitated the exploration of treatment options. Of interest is Romiplostim (Promacta), a thrombopoietin receptor agonist, which has shown promise in increasing platelet counts and reducing bleeding episodes in refractory ITP. Considering the positive ANA and the suspected rheumatological etiology, Romiplostim may serve as a viable long-term treatment option to stabilize platelet levels and mitigate bleeding risks in this case. Conclusion: This case highlights the complexity of Evans syndrome and emphasizes the need to promptly recognize and manage life-threatening bleeding complications, particularly in older patients. The presence of a positive ANA suggests an underlying rheumatological condition, necessitating comprehensive evaluation, and tailored therapeutic approaches. Although further research is needed to understand the pathogenesis and optimal management strategies for ES, Romiplostim holds promise as a potential treatment for patients with secondary ES who are unresponsive to conventional therapies. Citation Format: Kiersten R. Patterson, Aliya M. Khan, Raj Patel. Intracerebral and intraventricular hemorrhage due to severe thrombocytopenia: A rare case of Evans syndrome [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B030.

Efficacy and Safety of Human Umbilical Cord-Derived Mesenchymal Stem Cells in the Treatment of Immune Thrombocytopenia: A Prospective, Single Centre, Single Arm, Phase I Trial

Background Patients with refractory immune thrombocytopenia (ITP) often suffer severe bleeding events and have poor responses to various treatments. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) have been used to treat multiple autoimmune diseases due to their low immunogenicity and strong immunomodulatory potential. To explore the safety and efficacy of UC-MSCs in treating refractory ITP, we conducted this phase Ⅰ clinical trial. Methods Patients diagnosed with refractory ITP were screened for the study. The major inclusion criteria included age 18 to 60 years, ITP duration lasting for more than six months, platelet count < 30 × 10 9/L and concomitant bleeding manifestations at enrolment. The study consisted of two parts: a dose-escalation phase for exploring the safety and efficacy of three different dosage groups according to the traditional 3+3 protocol and a dose-expansion phase for further verifying the optimal UC-MSC dosage. UC-MSCs were administered at doses of 0.5×10 6 cells/kg, 1.0×10 6 cells/kg, and 2.0×10 6 cells/kg per week four times in the dose-escalation phase and 2.0×10 6 cells/kg per week four times in the dose-expansion phase. The adverse events, platelet counts, and bleeding symptoms were evaluated and recorded during the administration and follow-up period. The study protocol was approved by the Ethics Committees of the Institute of Hematology and Blood Diseases Hospital, and informed consent was obtained from each participant according to the Declaration of Helsinki (ClinicalTrials.gov ID: NCT04014166). Results Between November 2019 and August 2022, 18 refractory ITP patients hospitalized in our centre were successfully screened and enrolled in the study. Twelve patients were enrolled in the dose-escalation phase (three additional patients were added in the 2.0×10 6 cells/kg group due to the dose-limiting toxicity), and six patients were included in the dose-expansion phase. Thirteen patients (13/18, 72.2%) had one or more TEAEs. SAEs occurred in four patients (4/18, 22.2%), including gastrointestinal haemorrhage (2/4), profuse menstruation (1/4), and acute myocardial infarction (1/4). There were 0.0% (0/3), 66.7% (2/3), and 50.0% (6/12) patients in the 0.5×10 6, 1.0×10 6 and 2.0×10 6 cells/kg cohorts who achieved a response after treatment, respectively. The overall response rate was 44.4% (8/18) in all patients who received UC-MSCs. Conclusion UC-MSC infusion achieved a 44.4% overall response rate in patients with refractory ITP and mild adverse events.

Gpibα Caar-T Cells Induce Autoreactive B Cells Elimination to Treat Immune Thrombocytopenia

Background: Immune thrombocytopenia (ITP) is a bleeding disorder caused by autoantibodies against platelet glycoproteins (GPs). A key attempt to treat ITP is to eliminate the autoreactive B cells. Here, we proposed a new strategy for B cell-depletion therapy of ITP, chimeric autoantibody receptors T cells (CAAR-T), which could trap autoreactive B cells and perform specific killing. GPIbα is a significant autoantigen found in ITP patients and indicates a poor response to standard immunosuppressive treatments. We developed GPIbα-based CAARs in this study. Aim: To precisely eliminate the autoreactive B cells to treat ITP. Methods: We constructed various lengths of the native GPIbα ectodomain into the ligand-binding domain of a second-generation CAR structure and expressed the CAAR structure on the HEK293 cell surface to verify its conformational epitope. We immunized BALB/C mice with human platelet lysates to obtain anti-GPIbα hybridomas and performed a binding assay to confirm selected hybridoma antibodies' binding ability to GPIbα CAAR. We performed cytotoxicity assays to assess GPIbα CAAR-T-cell selective cytolysis against anti-GPIbα B cells in vitro and developed a xenograft model to assess the cytolytic efficiency and security of GPIbα CAAR-T cells in vivo. A plasma antibody binding assay was used to test GPIbα CAAR-T cells' ability in reaction with native GPIbα autoantibodies from ITP patients. We applied an enzyme-linked immunospot (ELISpot) assay to verify GPIbα CAAR-T cells' potential in eradicating autoreactive B cells of ITP patients. Results: We successfully expressed GPIbα CAAR structure on the cell surface and proved that the conformational epitope of GPIbα CAAR is consistent with that of the native human platelet GPIbα. The Schematic of GPIbα CAAR structure is presented in Figure 1A. By immunizing BALB/C mice with human platelet lysates, we obtained four anti-GPIbα hybridomas with different CAAR binding sites. Vitro cytotoxicity assays confirmed GPIbα CAAR-T-cell selective cytolysis of anti-GPIbα hybridoma cells. In a hybridoma xenograft model, we verified that the CAAR-T cells could persist and selectively lyse autoreactive B cells and subsequently reduce autoantibody titers without apparent off-target organ toxicity. Through the plasma antibody binding assay, we demonstrated that GPIbα CAAR could react with sera from ITP patients with anti-GPIbα antibodies (Figure 1B). ELISpot analysis showed that GPIbα CAAR-T cells successfully eliminated anti-GPIbα B cells from a patient with refractory ITP, and normal B cells were not destroyed compared to anti-CD19 CAR-T cells. Conclusion: Our study provides a proof of concept for CAAR-T cell therapy to eradicate autoimmune B cells while sparing healthy B cells, which would compensate for the defects of traditional B cell depletion therapy in ITP. GPIbα CAAR-T therapy would be a promising treatment for refractory and relapsed ITP patients.

Efficacy and Safety of Fostamatinib for Immune Thrombocytopenia in Clinical Practice in Spain: Interim Results of Fostames, Our National Fostamatinib Registry

Background: Fostamatinib is a splenic tyrosine kinase (SYK) inhibitor that prevents antibody-mediated platelet destruction. This drug has demonstrated to be effective and safe in immune thrombocytopenia (ITP). However, clinical trials may not accurately reflect what happens in clinical practice. Here we evaluated the efficacy and safety of eltrombopag in ITP in a real-world setting. Aims: To assess the management of adult patients with immune thrombocytopenia (ITP) with fostamatinib (Tavlesse®) in routine clinical practice outside controlled clinical trials. Methods: Multicentre, retrospective and prospective observational study at national level to evaluate the management of fostamatinib (Tavlesse®) in adult patients with ITP. An interim analysis of the medical records of all patients treated with fostamatinib (Tavlesse®) and suffering from ITP at each center was performed. Data were obtained in a retrospective and prospective observational, non-interventional manner to fulfil the exclusively scientific objective of this study, by conducting a review of the patient's clinical history. Thus, a total of 46 adult patients with ITP from 19 Spanish centers, who had been treated with fostamatinib, were evaluated. Results: The median age of our cohort was 74 yr (interquartile range, IQR, 60-81 yr). 25/46 (54%) were women. 43 of them were Primary ITP, 2 Secondary ITP and only one Evans Syndrome. 20 (47.6%) had ≥ 1 comorbidity of the Charlson Comorbidity Index. At the time of ITP diagnosis, the median platelet count was 8 x 10 9/L (IQR, 4-21 x 10 9/L) while 31 (69%) patients had hemorrhages. The median time with a diagnosis of ITP at initiation of fostamatinib was 61 months (IQR, 9-160 months). The median number of therapies prior to fostamatinib was 4 (IQR, 3-6). Of the entire cohort of 46 patients, 35 had been exposed to eltrombopag, 33 to romiplostim, 23 to intravenous immunoglobulins (IVIG), and 21 to rituximab. Only eight and two patients had received avatrombopag and splenectomy prior to fostamatinib treatment, respectively. 26/46 patients (56.5%) were treated with fostamatinib monotherapy throughout ITP. Twenty-three patients (50%) had signs/symptoms of bleeding in the month prior to treatment initiation. The median platelet count at baseline on fostamatinib was 12 × 10 9/L (IQR, 6-28 × 10 9/L), while the median platelet count to best response achieved after fostamatinib treatment was 84 × 10 9/L (IQR, 28-187 × 10 9/L). The median time from initiation of fostamatinib to maximum response to treatment was 2 months (IQR, 0-3.25). Similarly, the median duration of treatment with fostamatinib was 2 months (IQR, 1-4.25). The median time from initiation of fostamatinib to dose increase to 150 mg twice a day was 16 days (IQR, 8-38). A total of 32/46 patients (69.5%) responded to fostamatinib. Thus, 21 patients (45.7%) achieved a complete response (platelet count > 100 x 10 9/L) and 11 achieved a response. Twenty-one patients (45.6%) experienced adverse events, mainly grade 1-2, with diarrhea (n=13) and hypertension (n=8) being the most frequent. Twenty-five patients (54.3%) discontinued fostamatinib treatment: 18 did so due to inefficacy with three exitus due to severe bleeding in the context of refractory ITP. On the contrary, only three patients discontinued the drug due to toxicity/severe adverse events. Summary/Conclusion: Fostamatinib was used in heavily treated patients. However, fostamatinib proved to be effective and well tolerated in unselected patients with primary and secondary ITP. The association of fostamatinib with other drugs or its use in earlier lines of therapy may be associated with higher platelet response rates.

MST4 kinase regulates immune thrombocytopenia by phosphorylating STAT1-mediated M1 polarization of macrophages.

Primary immune thrombocytopenia (ITP) is an autoimmune hemorrhagic disorder in which macrophages play a critical role. Mammalian sterile-20-like kinase 4 (MST4), a member of the germinal-center kinase STE20 family, has been demonstrated to be a regulator of inflammation. Whether MST4 participates in the macrophage-dependent inflammation of ITP remains elusive. The expression and function of MST4 in macrophages of ITP patients and THP-1 cells, andof a macrophage-specific Mst4-/- (Mst4ΔM/ΔM) ITP mouse model were determined. Macrophage phagocytic assays, RNA sequencing (RNA-seq) analysis, immunofluorescence analysis, coimmunoprecipitation (co-IP), mass spectrometry (MS), bioinformatics analysis, and phosphoproteomics analysis were performed to reveal the underlying mechanisms. The expression levels of the MST4 gene were elevated in the expanded M1-like macrophages of ITP patients, and this elevated expression of MST4 was restored to basal levels in patients with remission after high-dose dexamethasone treatment. The expression of the MST4 gene was significantly elevated in THP-1-derived M1 macrophages. Silencing of MST4 decreased the expression of M1 macrophage markers and cytokines, and impaired phagocytosis, whichcould be increased by overexpression of MST4. In a passive ITP mouse model, macrophage-specific depletion of Mst4 reduced the numbers of M1 macrophages in the spleen and peritoneal lavage fluid, attenuated the expression of M1 cytokines, and promoted the predominance of FcγRIIb in splenic macrophages, which resulted in amelioration of thrombocytopenia. Downregulation of MST4 directly inhibited STAT1 phosphorylation, which is essential for M1 polarization of macrophages. Our study elucidates a critical role for MST4 kinase in the pathology of ITP and identifies MST4 kinase as a potential therapeutic target for refractory ITP.

Refractory primary immune thrombocytopenia and use of combined therapy, case report

La trombocitopenia inmune primaria es un trastorno autoinmune adquirido, caracterizado por una destrucción plaquetaria excesiva, derivada de la producción de anticuerpos contra la membrana plaquetaria, conllevando a un alto riesgo de hemorragia para el paciente. Actualmente, la piedra angular del tratamiento sigue siendo el uso de agentes de primera línea como los glucocorticoides y la inmunoglobulina intravenosa. Sin embargo, en algunos casos los pacientes pueden ser refractarios a estos, con el requerimiento de terapias de segunda y tercera línea. Se presenta el caso clínico de una paciente de 25 años con historia de trombocitopenia inmune primaria con presentación severa por la presencia de sangrado gastrointestinal y estado anémico asociado, con refractariedad a diferentes estrategias de tratamiento, incluida la esplenectomía, requiriendo posterior manejo combinado con Rituximab, con el cual se logró mantener un recuento plaquetario adecuado. Consideramos que este caso toma interés clínico dado los escasos reportes de casos de esta condición y la limitada evidencia que se tiene ante las terapias secuenciales en pacientes refractarios a tratamiento de primera línea.

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.

The role of genetics in refractory immune thrombocytopenia.

Patients with refractory immune thrombocytopenia (rITP) have increased morbidity and mortality. Currently, there is limited understanding of the cause of refractoriness and no markers to help direct novel treatment options. Understanding the reason(s) for refractoriness is crucial to determining novel treatment options. The pathogenesis underlying rITP has generally been thought to be an underlying genetic predisposition with an environmental trigger. Familial ITP remains rare, and there are few twin studies, suggesting that a simple genetic cause is unlikely. However, genetic mutations provide the background for several autoimmune diseases. In this review, we explore the evidence of either an inherited genetic cause of rITP or an acquired mutation, in particular one resulting in clonal expansion of cytotoxic T cells.

Chronic refractory immune thrombocytopenia in adolescents and young adults.

Defining immune thrombocytopenia (ITP) in two age groups-children and adults-overlooks the specific clinical features and needs of adolescents and young adults (AYAS). We previously reported a high risk of chronic disease at 12 months (50%); however, data on the course of chronic ITP, the risk of refractoriness and treatment strategies in AYAS are limited. Data from patients aged 12-25 years with chronic primary ITP at 12 months were extracted from three large registries between 2004 and 2021. Clinical and laboratory data were evaluated until 48 months of follow-up (FU). Refractory ITP was defined as the administration of ≥3 different lines of therapy. A total of 427 AYAS (64% female) with chronic ITP were included. Overall, 7% and 14% were classified as 'refractory' at 12 and 48 months of FU respectively. The proportion of males was greater in the refractory group than in the non-refractory group (43% vs. 35%). AYAS with refractory disease displayed lower median platelet counts, more bleeding and a higher need for treatment at initial diagnosis and FU than non-refractory patients. This study reveals that refractory ITP is uncommon in AYAS; however, AYAS with refractory ITP display a high disease burden at all time points, including at initial diagnosis.

Complement in immune thrombocytopenia (ITP): The role of complement in refractory ITP.

Immune thrombocytopenia (ITP) is a disorder characterized by low platelets due to increased clearance and decreased platelet production. While ITP has been characterized as an acquired disorder of the adaptive immune system, the resulting platelet autoantibodies provide ancillary links to the innate immune system via antibody interaction with the complement system. Most autoantibodies in patients with ITP are of the IgG1 subclass, which can be potent activators of the classical complement pathway. Antibody-coated platelets can initiate complement activation via the classical pathway leading to both direct platelet destruction and enhanced clearance of C3b-coated platelets by complement receptors. Similar autoantibody interactions with bone marrow megakaryocytes can also result in complement injury and ineffective thrombopoiesis. The development of novel therapeutic complement inhibitors has revived interest in the role of complement in autoantibody-mediated disorders, such as ITP. A recent early-phase clinical trial of a classical complement pathway inhibitor has demonstrated efficacy in a subset of ITP patients refractory to conventional immune modulation. In this review, we will analyse the role of complement in refractory ITP.

Burden of immune thrombocytopenia (ITP): Special considerations for refractory ITP.

It is known that patients with immune thrombocytopenia (ITP) have fatigue and impairment of health-related quality of life (HRQoL). However, it is hypothesized that patients with refractory ITP have additional burdens that should be considered. Specifically, fatigue is more pronounced in patients with refractory disease, there are additional side effects from second- and third-line treatments, additional anxiety about the long-term course of the disease, impairment in HRQoL resulting from heavy menstrual bleeding and concerns related to family planning. The burden of disease, therefore, should be carefully assessed and considered in these patients. However, researchers have utilized numerous tools for evaluating HRQoL and fatigue, making comparison of data across studies challenging. There is a need to standardize assessment using either disease-specific or generic instruments that can be easily implemented in routine clinical practice. Additionally, whether treatment of low platelet count and bleeding symptoms will have a positive influence on HRQoL remains to be seen and published evidence is conflicting. Nevertheless, improvement of HRQoL is a major treatment goal for both patients and physicians and should be especially considered when treating patients with refractory ITP.