Immune thrombocytopenia (ITP) in pregnancy

Immune thrombocytopenia (ITP) in pregnancy is challenging for both mother and fetus. Understanding the pathophysiology, treatments, and risks to the mother and fetus leads to proper management resulting in successful pregnancy and delivery in almost all cases.1 ITP in a pregnant woman has many similarities to ITP not in pregnancy although gestational thrombocytopenia can be confused with ITP. However, recognizing differences is instrumental in avoiding bleeding complications and toxicities of treatment. This Nutshell review focuses on the natural history of ITP in pregnancy, its treatment, and dilemmas.

The highs and lows of cyclic thrombocytopenia

Cyclic thrombocytopenia (CTP) is characterized by periodic platelet oscillation with substantial amplitude. Most CTP cases have a thrombocytopenic background and are often misdiagnosed as immune thrombocytopenia with erratically effective treatment choices. CTP also occurs during hydroxyurea treatment in patients with myeloproliferative diseases. While the aetiology of CTP remains uncertain, here we evaluate historical, theoretical and clinical findings to provide a framework for understanding CTP pathophysiology. CTP retains the intrinsic oscillatory factors defined by the homeostatic regulation of platelet count, presenting as reciprocal platelet/thrombopoietin oscillations and stable oscillation periodicity. Moreover, CTP patients possess pathogenic factors destabilizing the platelet homeostatic system thereby creating opportunities for external perturbations to initiate and sustain the exaggerated platelet oscillations. Beyond humoral and cell-mediated autoimmunity, we propose recently uncovered germline and somatic genetic variants, such as those of MPL, STAT3 or DNMT3A, as pathogenic factors in thrombocytopenia-related CTP. Likewise, the JAK2 V617F or BCR::ABL1 translocation that drives underlying myeloproliferative diseases may also play a pathogenic role in hydroxyurea-induced CTP, where hydroxyurea treatment can serve as both a trigger and a pathogenic factor of platelet oscillation. Elucidating the pathogenic landscape of CTP provides an opportunity for targeted therapeutic approaches in the future.

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

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

Treatment of immune thrombocytopenia during pregnancy with thrombopoietin receptor agonists

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

Efficacy and safety of the neonatal Fc receptor inhibitor efgartigimod in adults with primary immune thrombocytopenia (ADVANCE IV): a multicentre, randomised, placebo-controlled, phase 3 trial

BACKGROUND

Primary immune thrombocytopenia is an autoimmune disorder mediated partly by platelet autoantibodies, resulting in thrombocytopenia, bleeding, and constitutional symptoms. Efgartigimod, a first-in-class novel human IgG1 Fc fragment, binds the neonatal Fc receptor with high affinity and thus reduces serum IgG concentrations, including autoantibodies. The objective of this study was to evaluate the efficacy and safety of efgartigimod in adults with persistent and chronic primary immune thrombocytopenia.

METHODS

This phase 3, multicentre, randomised, double-blinded, placebo-controlled, 24-week study evaluated the efficacy and safety of intravenous efgartigimod in adults aged 18 years or older with chronic or persistent primary immune thrombocytopenia who had an average platelet count of less than 30 000, had responded to at least one previous immune thrombocytopenia therapy, and were on a concurrent therapy at baseline or had received at least a second previous immune thrombocytopenia therapy. The study took place in 71 participating sites from Asia, Europe, and North America. Patients were randomly assigned 2:1 to receive either efgartigimod (10 mg/kg) or placebo intravenously for the first 4 weeks, after which the dosing schedule could be altered to once per week or every other week depending on the patients' platelet count. The primary endpoint, evaluated in the chronic population, was sustained platelet count response (≥50 × 109 for at least 4 of the last 6 weeks). This study is registered with ClinicalTrials.gov (NCT04188379) and is completed.

FINDINGS

A total of 205 patients were screened from Dec 9, 2019, to Feb 3, 2022, and 131 (86 in the efgartigimod group; 45 in the placebo group) were randomly assigned. These patients represented a population with long-term disease who had a mean time since diagnosis of 10·6 years and 67% (88/131) of whom had received at least three previous immune thrombocytopenia treatments. 22% (17/78) of patients with chronic immune thrombocytopenia receiving efgartigimod reached the primary endpoint compared with 5% (2/40) of those receiving placebo (p=0·032; adjusted difference in response, 16% [95% CI 2·6-26·4]). The median number of weeks of disease control in patients with chronic immune thrombocytopenia was 2·0 (IQR 0·0-11·0) for efgartigimod versus 0·0 (0·0-1·0) for placebo (p=0·0009). Efgartigimod was well tolerated; most adverse events were mild to moderate in severity. The most common adverse events of interest in both groups were headache (16% in efgartigimod and 13% in placebo), haematuria (16% in efgartigimod and 16% in placebo), and petechiae (15% in efgartigimod and 27% in placebo).

INTERPRETATION

Efgartigimod significantly increased sustained platelet count responses compared with placebo in patients with chronic immune thrombocytopenia, including those who had received multiple previous immune thrombocytopenia therapies. Upon completion of the ADVANCE IV study, patients could enroll in the ongoing open-label extension. Subcutaneous efgartigimod is currently being evaluated in patients with immune thrombocytopenia in the ADVANCE SC+ trial.

FUNDING

argenx.

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.

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.

Early initiation of second-line therapy in primary immune thrombocytopenia: insights from real-world evidence

To compare patients with primary immune thrombocytopenia (ITP) prescribed early (within 3 months of initial ITP treatment) second-line treatment (eltrombopag, romiplostim, rituximab, immunosuppressive agents, splenectomy) with or without concomitant first-line therapy to those who received only first-line therapy. This real-world retrospective cohort study of 8268 patients with primary ITP from a large US-based database (Optum^® de-identified Electronic Health Record [EHR] dataset) combined electronic claims and EHR data. Outcomes included platelet count, bleeding events, and corticosteroid exposure 3 to 6 months after initial treatment. Baseline platelet counts were lower in patients receiving early second-line therapy (10‒28 × 10⁹/L) versus those who did not (67 × 10⁹/L). Counts improved and bleeding events decreased from baseline in all treatment groups 3 to 6 months after the start of therapy. Among the very few patients for whom follow-up treatment data were available (n = 94), corticosteroid use was reduced during the 3- to 6-month follow-up period in patients who received early second-line therapy versus those who did not (39% vs 87%, p < 0.001). Early second-line treatment was prescribed for more severe cases of ITP and appeared to be associated with improved platelet counts and bleeding outcomes 3 to 6 months after initial therapy. Early second-line therapy also appeared to reduce corticosteroid use after 3 months, although the small number of patients with follow-up data on treatment precludes any substantive conclusions. Further research is needed to determine whether early second-line therapy has an effect on the long-term course of ITP.

The role of CD8+ T-cell clones in immune thrombocytopenia

Immune thrombocytopenia (ITP) is traditionally considered an antibody-mediated disease. However, a number of features suggest alternative mechanisms of platelet destruction. In this study, we use a multidimensional approach to explore the role of cytotoxic CD8+ T cells in ITP. We characterized patients with ITP and compared them with age-matched controls using immunophenotyping, next-generation sequencing of T-cell receptor (TCR) genes, single-cell RNA sequencing, and functional T-cell and platelet assays. We found that adults with chronic ITP have increased polyfunctional, terminally differentiated effector memory CD8+ T cells (CD45RA+CD62L-) expressing intracellular interferon gamma, tumor necrosis factor α, and granzyme B, defining them as TEMRA cells. These TEMRA cells expand when the platelet count falls and show no evidence of physiological exhaustion. Deep sequencing of the TCR showed expanded T-cell clones in patients with ITP. T-cell clones persisted over many years, were more prominent in patients with refractory disease, and expanded when the platelet count was low. Combined single-cell RNA and TCR sequencing of CD8+ T cells confirmed that the expanded clones are TEMRA cells. Using in vitro model systems, we show that CD8+ T cells from patients with ITP form aggregates with autologous platelets, release interferon gamma, and trigger platelet activation and apoptosis via the TCR-mediated release of cytotoxic granules. These findings of clonally expanded CD8+ T cells causing platelet activation and apoptosis provide an antibody-independent mechanism of platelet destruction, indicating that targeting specific T-cell clones could be a novel therapeutic approach for patients with refractory ITP.

Overuse of corticosteroids in patients with immune thrombocytopenia (ITP) between 2011 and 2017 in the United States

Corticosteroids (CSs) are standard first-line therapy for immune thrombocytopenia (ITP). Prolonged exposure is associated with substantial toxicity; thus guidelines recommend avoidance of prolonged CS treatment and early use of second-line therapies. However, real-world evidence on ITP treatment patterns remains limited. We aimed to assess real-world treatment patterns in patients with newly-diagnosed ITP, using two large US healthcare databases (Explorys and MarketScan) between January 1, 2011 and July 31, 2017. Adults with ITP, ≥12 months of database registration prior to diagnosis, ≥1 ITP treatment, and ≥1 month enrollment following initiation of first ITP treatment were included (n = 4066 Explorys; n = 7837 MarketScan). Information on lines of treatment (LoTs) was collected. As expected, CSs were the most common first-line treatment (Explorys, 87.9%; MarketScan, 84.5%). However, CSs remained by far the most common treatment (Explorys ≥77%; MarketScan ≥85%) across all subsequent LoTs. Second-line treatments such as rituximab (12.0% Explorys; 24.5% MarketScan), thrombopoietin receptor agonists (11.3% Explorys; 15.6% MarketScan), and splenectomy (2.5% Explorys; 8.1% MarketScan) were used much less frequently. CS use is widespread in the US in patients with ITP across all LoTs. Quality improvement initiatives are needed to reduce CS exposure and bolster use of second-line treatments.

Maintenence rituximab following induction in autoimmune cytopenias

About 50% of immune thrombocytopenia (ITP) patients respond to rituximab induction, but most relapse. The effectiveness of rituximab maintenance remains untested. This study included autoimmune cytopenia patients who had previously responded to rituximab induction but subsequently relapsed. After re-induction, patients received rituximab maintenance regimen consisting of a single 375 mg/m² dose administered at 4 month intervals, with a maximum of 6 doses. Primary endpoints were duration of response and safety. Sixteen patients: ITP (9), autoimmune haemolytic anaemia (2), and Evans syndrome (5) received rituximab maintenance. 15/16 achieved complete response (CR); 8/15 CR + 1 partial reponse remain in remission. Median response: 43 months; estimated 5-year relapse-free >50%. Three developed hypogammaglobulinemia. Rituximab maintenance led to prolonged remissions in patients with autoimmune cytopenias who had previously responded to rituximab induction.

Why should intramuscular anti-D be different from intravenous anti-D?

For reasons of safety the use of intravenous anti D to treat ITP has largely been abandoned because of the risk it incurs of intravascular haemolysis. Intramuscular delivery of anti-D could be a safer approach and deserves to be further evaluated. IV anti-D was a mainstay of ITP treatment in the United States in the 1990's until the development of intravascular hemolysis (IVH) and its serious even fatal consequences was appreciated. Subsequently, treatment of patients with ITP with IV anti-D has become very rare given other alternatives and the IVH risk. IM anti-D does not carry a risk for IVH and it should be re-evaluated and reconsidered as an option for D+ DAT-negative not splenectomized adults who do not have a long duration of ITP and require maintenance treatment. Commentary on: Lakhwani, et al. Intramuscular Anti-D treatment for immune thrombocytopenia: A single centre experience. Br J Haematol 2023;200:353-357.

Should dexamethasone alone or in combination be the initial steroid for adult ITP: Still a relevant question

Corticosteroids are used in first-line treatment in newly diagnosed immune thrombocytopenia. The goal of treatment is primarily to decrease autoantibody-mediated platelet clearance. Ideally initial treatment would not just increase the platelet count but also provide a long-term sustained remission. While many clinicians use prednisone (PDN) as their first choice of corticosteroid, others prefer dexamethasone. The controversy is the subject of debates. Short courses of higher-dose corticosteroids were first reported by the Andersen study in 1994. The study posited high-dose dexamethasone as a 'cure' for all ITP patients. Later, studies addressed the number of dexamethasone cycles, indications to repeat cycles and timing between cycles, with varied long-term results. The results with dexamethasone were compared to PDN in some studies: the four-day cycles of dexamethasone work faster in increasing platelet counts and appear to reduce the occurrence of severe adverse events. Therefore, it is probably a better option for patients with low platelet counts and bleeding diathesis; however, curative superiority, the initial reason to administer it, compared to PDN is not well demonstrated. Across the studies, treatment with high-dose dexamethasone seems to be safer, with lower incidence of all adverse events compared to PDN, which might be a reflection of shorter treatment duration and possibly also lower cumulative steroid dose. Dexamethasone in combination with rituximab in first-line treatment produced higher response rates with better long-term results compared to high-dose dexamethasone alone and is a particularly good option in younger women.

Effects of COVID-19 vaccination on platelet counts and bleeding in children, adolescents, and young adults with immune thrombocytopenia

Coronavirus disease 2019 (COVID-19) vaccines rarely cause de novo immune thrombocytopenia (ITP) but may worsen preexisting ITP in adults. Whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines impact platelet counts and bleeding in children, adolescents, and young adults (C-AYA) with preexisting ITP is unknown. We report here the very limited effect of COVID-19 vaccination on platelet counts and bleeding in a single-center series of 2 C-AYA with ITP. No patient experienced worsening bleeding and only one child had a significant decrease in platelet count which improved spontaneously to her baseline without intervention. SARS-CoV2 vaccination was safe in C-AYA with ITP in this small cohort.

Romiplostim use in pregnant women with immune thrombocytopenia

Treatment for immune thrombocytopenia (ITP) in pregnancy is hampered by the lack of fetal safety evidence of maternally-administered medications. The Pregnancy Surveillance Program (PSP) collected patient information from 2017-2020 for pregnancy, birth outcomes, and adverse events (AEs) for 186 women exposed to romiplostim from 20 days before pregnancy to the end of pregnancy. Timing of exposure was available in 128 women. Seventy-one mothers (38%) had prepregnancy exposure to romiplostim; intrapartum exposure was known for the first (for many mothers when they discovered their pregnancy), second, and third trimesters for 74 (40%), 22 (12%), and 44 (24%) mothers, respectively, with 15 mothers exposed during >1 trimester. Among the 86 mothers with known pregnancy outcomes, 46 (53%) had at least one pregnancy-related serious AE (SAE); approximately 2/3 of SAEs were due to underlying ITP. Of 92 mothers with known birth outcomes, 60 (65%) had a normal pregnancy and 16 (17%) had complications, with both categories including term and preterm births; there were 12 (14%) spontaneous miscarriages/stillbirths, 3 (3%) ectopic pregnancies, and 1 (1%) molar pregnancy. Most abnormal births resulted from abnormal pregnancies. There were five neonatal/postnatal AEs of note: inguinal hernia, cytomegalovirus infection, trisomy 8 (third trimester single-dose romiplostim exposure), single umbilical artery without known anomalies, and development of autism at age 2 years. Seven of 12 infants with neonatal thrombocytopenia had resolution of thrombocytopenia before discharge; all 12 were discharged. Review of pregnancies in women exposed to romiplostim did not reveal any specific safety concerns for mothers, fetuses, or infants.

Abstract C028: The lung pro-thrombotic niche drives cancer-associated thromboembolism and metastasis via extracellular vesicle ITGB2

Thromboembolism (TE) is a common complication in cancer patients and the second leading cause of cancer-related deaths. The incidence of TE varies in different cancer types, with the highest risk in pancreatic ductal adenocarcinoma (PDAC) and in advanced-stage and metastatic cancers. Despite the benefits associated with anti-coagulant therapy for symptomatic TE, the prevention of TE still remains an unmet clinical need due to lack of biomarkers predictive of TE risk and the bleeding risk associated with the routine use of anti-coagulants. Small extracellular vesicles (sEV) mediate cell-to-cell communication. Cancer cells and the tumor microenvironment release large numbers of sEV into the blood circulation and sEVs have displayed a therapeutic and predictive value in systemic diseases. However, the role of sEVs in cancer-associated TE remains to be investigated. Here we show that sEVs from (pre)metastatic lungs of mice with melanoma, breast, lung, and PDAC induce TE in mice and express high levels of integrin beta 2 (ITGB2), while sEVs from tumor cell lines, primary tumors, or other metastasis-bearing organs did not show any pro-thrombotic properties. A specific subtype of interstitial macrophages infiltrating (pre-)metastatic lungs were the main source of ITGB2+ pro-thrombotic sEVs. Blockade of ITGB2 on lung-derived sEVs, or systemically in mice, prevented EV-induced platelet aggregation and TE, and reduced metastasis. Examination of the mechanisms of ITGB2-induced TE showed that EV-associated ITGB2 interacts directly or through fibrin with different binding partners on platelets, and induce their activation and aggregation. Importantly, we found that levels of ITGB2 on sEVs are elevated in the plasma of PDAC patients prior (&lt;30 days) to TE events in comparison to PDAC patients with no history of TE, and thus might serve as prognostic biomarker of TE. Together, our results provide the first evidence of the establishment of a pro-thrombotic lung niche in PDAC as well as other cancer types. Moreover, we identify EV-associated ITGB2 as a new target for the prevention and/or treatment of TE, as well as a potential “liquid biopsy” analyte for the early stratification of patients at high risk of TE.

Citation Format: Serena Lucotti, Yusuke Ogitani, Candia M. Kenific, Linda Bojmar, Michele Cioffi, Pernille Lauritzen, Henrik Molina, Soeren Heissel, Henry B. Lengel, Xiaohong Jing, Haiying Zhang, Irina Matei, Eileen M. O'Reilly, William R. Jarnagin, David Jones, James B. Bussel, David Kelsen, Jacqueline F. Bromberg, Diane M. Simeone, David Lyden. The lung pro-thrombotic niche drives cancer-associated thromboembolism and metastasis via extracellular vesicle ITGB2 [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C028.

A narrative review of anti-SARS-CoV-2 vaccines and immune thrombocytopenia: be aware, but reassured

The COVID-19 pandemic gave rise to rapid development of anti-SARS-CoV-2 vaccines using established and new technologies. Immune thrombocytopenia (ITP) is a bleeding disorder that has been associated with COVID-19 vaccine products that are currently in use. We reviewed the available evidence regarding the most commonly used vaccines against SARS-CoV-2 in North America and Europe and their association with ITP. We found that population-based studies suggested a small increase in the incidence of ITP in persons receiving the ChAdOx1 nCoV-19 vaccine from Oxford-AstraZeneca, on the order of 6 cases per million doses administered. Severe bleeding was an even rarer event. Both messenger RNA-based and adenovirus-based vaccines have been associated with exacerbation of preexisting ITP in 6% to 20% of patients. ITP exacerbation is readily treatable with standard approaches when needed. Severe bleeding events are rare both in the general population and in persons with preexisting ITP, and overall, the benefits of vaccination outweigh the risks. Further identification of persons at the highest risk for complications (including those with ITP, vaccine-induced immune thrombotic thrombocytopenia, and myocarditis) and clear communication of both risks and benefits of immunization will continue to be paramount in the global campaign against COVID-19.

Immune thrombocytopenia (ITP): diagnosis including secondary ITP, and selection of second line treatment

This article summarizes our approach to the diagnosis of immune thrombocytopenia (ITP), its secondary forms, and choice of second-line treatment options. We very briefly summarize first-line treatment and then utilize a case-based approach. We first explore persistent, chronic ITP in a younger female. We consider many possibilities beyond primary ITP e.g., hypogammaglobulinemia, chronic infection, and anemia, and how to approach their diagnosis and management. The journey continues throughout pregnancy and the post-partum period and eventually includes fourth-line treatment after a late relapse. We then consider an older male, emphasizing differences in diagnostic considerations and management. The focus is on initiation and continuation of second-line treatment, the pros and cons of each option, and briefly the impact of treatment choices related to the endemic presence of severe acute respiratory syndrome coronavirus 2. During the review of potential second-line treatment options, we also briefly touch upon novel treatments. Finally, there is a short section on refractory disease drawn from our previous extensive review published in February 2020.¹ The clinical nature of the discussions, replete with figures and tables and with the interspersion of pearls regarding efficacy and toxicity at different ages and genders, will serve the reader in the management of “typical” adult patients who develop persistent and chronic ITP.

Abstract 3138: The lung pro-thrombotic niche drives cancer-associated thromboembolism via exosomal ITGB2

Thromboembolism (TE) is a common complication in cancer patients and the second leading cause of cancer-related deaths. The incidence of TE varies in different cancer types, with the highest risk in lung cancer and pancreatic ductal adenocarcinoma (PDAC), and in advanced-stage and metastatic cancers. Despite the benefits associated with thromboprophylaxis for symptomatic TE, the prevention of TE still remains an unmet clinical need due to lack of biomarkers predictive of TE risk and the bleeding risk associated with the routine use of anti-coagulants. Exosomes are small circulating extracellular vesicles that mediate cell-to-cell communication. Cancer cells and the tumor microenvironment release large numbers of exosomes into the blood circulation and have displayed a therapeutic and predictive value in systemic diseases. Integrins expressed on the surface of exosomes drive their selective organotropism and prepare distant sites for metastatic seeding by establishing favorable pre-metastatic niches. Here we show that exosomes from metastasis-bearing lungs or pre-metastatic lungs of mice with melanoma, breast, lung and pancreatic cancer induce TE in mice and express high levels of integrin beta 2 (ITGB2). Instead, exosomes from tumor cell lines, primary tumors or other metastasis-bearing organs did not show any pro-thrombotic properties. Myeloid cells including monocytes/macrophages and neutrophils infiltrating pre- and post-metastatic lungs were the main source of ITGB2+ pro-thrombotic exosomes. Blockade of ITGB2 on lung-derived exosomes, or systemically in mice, prevented exosome-induced platelet aggregation and TE, and reduced metastasis. Examination of the mechanisms of ITGB2-induced TE showed that exosomal ITGB2 interact directly or through fibrin with different binding partners on platelets, and induce their activation and aggregation. Importantly, we found that exosomal ITGB2 levels are elevated in the plasma of PDAC patients prior to TE events in comparison to PDAC patients with no history of TE, and thus might serve as prognostic biomarker of TE. Together, our results provide the first evidence of the establishment of a pro-thrombotic lung niche in different cancer types. Moreover, we identify exosomal ITGB2 as a new target for the prevention and/or treatment of TE, as well as a potential “liquid biopsy” analyte for the early stratification of patients at high risk of TE.

Citation Format: Serena Lucotti, Yusuke Ogitani, Candia M. Kenific, Linda Bojmar, Michele Cioffi, Pernille Lauritzen, Henrik Molina, Soren Heissel, Harry B. Lengel, Xiaohong Jing, Haiying Zhang, Irina Matei, Eileen M. O'Reilly, William R. Jarnagin, David R. Jones, James B. Bussel, David Kelsen, Jacqueline F. Bromberg, Diane M. Simeone, David Lyden. The lung pro-thrombotic niche drives cancer-associated thromboembolism via exosomal ITGB2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3138.

Low-dose rituximab in immune thrombocytopenia: One and done

Rituximab is a widely-used medication for many years, important in management of immune thrombocytopenia (ITP); however, the optimal rituximab dose remains unknown. Ni and colleagues report a clinical trial comparing 2 doses of rituximab: a single dose of 375 mg/m² versus 100 mg/m² weekly for four weeks. The authors report similar efficacy and safety profile with both strategies. However, single-dose rituximab offered substantial benefits in quality-of-life and decrease in treatment costs. The study by Ni and colleagues adds a new option for management of ITP with rituximab. This article is protected by copyright. All rights reserved.

New developments in fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia, the platelet equivalent of hemolytic disease of the fetus and newborn, can have devastating effects on both the fetus and neonate. Current management of fetal and neonatal alloimmune thrombocytopenia in a subsequent affected pregnancy involves antenatal administration of intravenous immune globulin and prednisone to the pregnant woman to prevent the development of severe fetal thrombocytopenia and secondary intracranial hemorrhage in utero. That therapy has proven to be highly effective but is associated with maternal side effects and is expensive. This commentary describes 4 advances that could substantially change the current approach to detecting and managing fetal and neonatal alloimmune thrombocytopenia in the near future. The first would be an introduction of a program to screen all antepartum patients in this country for pregnancies at risk of developing fetal and neonatal alloimmune thrombocytopenia. Strategies to implement this complex process have been described. A second advance is testing of cell-free fetal DNA obtained from maternal blood to noninvasively determine the fetal human platelet antigen 1 genotype. A third, in preliminary development, is creation of a prophylactic product that would be the platelet equivalent of Rh immune globulin (RhoGAM). Finally, a fourth major potential advance is the development of neonatal Fc receptor inhibitors to replace the current medical therapy administered to pregnant women with an affected fetus. Neonatal Fc receptor recycles plasma immunoglobulin G to increase its half-life and is the means by which immunoglobulin G crosses the placenta from the maternal to the fetal circulation. Blocking the neonatal Fc receptor is an ideal way to prevent maternal immunoglobulin G antibody from causing fetal and neonatal alloimmune thrombocytopenia in a fetus at risk of developing that disorder. The pertinent pathophysiology and rationale for each of these developments will be presented in addition to our thoughts relating to steps that must be taken and difficulties that each approach would face for them to be successfully implemented.

Quality of life is an important indication for second-line treatment in children with immune thrombocytopenia

BACKGROUND

The decision to initiate second-line treatment in children with immune thrombocytopenia (ITP) is complex and involves many different factors.

METHODS

In this prospective, observational, longitudinal cohort study of 120 children from 21 centers, the factors contributing to the decision to start second-line treatments for ITP were captured. At study entry, clinicians were given a curated list of 12 potential reasons the patient required a second-line treatment. Clinicians selected all that applied and ranked the top three reasons.

RESULTS

Quality of life (QOL) was the most frequently cited reason for starting a second-line therapy. Clinicians chose it as a reason to treat in 88/120 (73%) patients, as among the top three reasons in 68/120 (57%), and as the top reason in 32/120 (27%). Additional factors ranked as the top reason to start second-line treatment included severity of bleeding (22/120, 18%), frequency of bleeding (19/120, 16%), and severity of thrombocytopenia (18/120, 15%). Patients for whom QOL (p = .006) or sports participation (p = .02) were ranked reasons were more likely to have chronic ITP, whereas those for whom severity (p = .003) or frequency (p = .005) of bleeding were ranked reasons were more likely to have newly diagnosed or persistent ITP. Parental anxiety, though rarely the primary impetus for treatment, was frequently cited (70/120, 58%) as a contributing factor.

CONCLUSION

Perceived QOL is the most frequently selected reason pediatric patients start second-line therapies for ITP. It is critical that studies of treatments for childhood ITP include assessments of their effects on QOL.

Miniaturized 3D bone marrow tissue model to assess response to Thrombopoietin-receptor agonists in patients

Thrombocytopenic disorders have been treated with the Thrombopoietin-receptor agonist Eltrombopag. Patients with the same apparent form of thrombocytopenia may respond differently to the treatment. We describe a miniaturized bone marrow tissue model that provides a screening bioreactor for personalized, pre-treatment response prediction to Eltrombopag for individual patients. Using silk fibroin, a 3D bone marrow niche was developed that reproduces platelet biogenesis. Hematopoietic progenitors were isolated from a small amount of peripheral blood of patients with mutations in ANKRD26 and MYH9 genes, who had previously received Eltrombopag. The ex vivo response was strongly correlated with the in vivo platelet response. Induced Pluripotent Stem Cells (iPSCs) from one patient with mutated MYH9 differentiated into functional megakaryocytes that responded to Eltrombopag. Combining patient-derived cells and iPSCs with the 3D bone marrow model technology allows having a reproducible system for studying drug mechanisms and for individualized, pre-treatment selection of effective therapy in Inherited Thrombocytopenias.

Platelets are tiny cell fragments essential for blood to clot. They are created and released into the bloodstream by megakaryocytes, giant cells that live in the bone marrow. In certain genetic diseases, such as Inherited Thrombocytopenia, the bone marrow fails to produce enough platelets: this leaves patients extremely susceptible to bruising, bleeding, and poor clotting after an injury or surgery.

Certain patients with Inherited Thrombocytopenia respond well to treatments designed to boost platelet production, but others do not. Why these differences exist could be investigated by designing new test systems that recreate the form and function of bone marrow in the laboratory. However, it is challenging to build the complex and poorly understood bone marrow environment outside of the body.

Here, Di Buduo et al. have developed an artificial three-dimensional miniature organ bioreactor system that recreates the key features of bone marrow. In this system, megakaryocytes were grown from patient blood samples, and hooked up to a tissue scaffold made of silk. The cells were able to grow as if they were in their normal environment, and they could shed platelets into an artificial bloodstream. After treating megakaryocytes with drugs to stimulate platelet production, Di Buduo et al. found that the number of platelets recovered from the bioreactor could accurately predict which patients would respond to these drugs in the clinic.

This new test system enables researchers to predict how a patient will respond to treatment, and to tailor therapy options to each individual. This technology could also be used to test new drugs for Inherited Thrombocytopenias and other blood-related diseases; if scaled-up, it could also, one day, generate large quantities of lab-grown blood cells for transfusion.

A Review of Romiplostim Mechanism of Action and Clinical Applicability

Thrombocytopenia results from a variety of conditions, including radiation, chemotherapy, autoimmune disease, bone marrow disorders, pathologic conditions associated with surgical procedures, hematopoietic stem cell transplant (HSCT), and hematologic disorders associated with severe aplastic anemia. Immune thrombocytopenia (ITP) is caused by immune reactions that accelerate destruction and reduce production of platelets. Thrombopoietin (TPO) is a critical component of platelet production pathways, and TPO receptor agonists (TPO-RAs) are important for the management of ITP by increasing platelet production and reducing the need for other treatments. Romiplostim is a TPO-RA approved for use in patients with ITP in the United States, European Union, Australia, and several countries in Africa and Asia, as well as for use in patients with refractory aplastic anemia in Japan and Korea. Romiplostim binds to and activates the TPO receptor on megakaryocyte precursors, thus promoting cell proliferation and viability, resulting in increased platelet production. Through this mechanism, romiplostim reduces the need for other treatments and decreases bleeding events in patients with thrombocytopenia. In addition to its efficacy in ITP, studies have shown that romiplostim is effective in improving platelet counts in various settings, thereby highlighting the versatility of romiplostim. The efficacy of romiplostim in such disorders is currently under investigation. Here, we review the structure, mechanism, pharmacokinetics, and pharmacodynamics of romiplostim. We also summarize the clinical evidence supporting its use in ITP and other disorders that involve thrombocytopenia, including chemotherapy-induced thrombocytopenia, aplastic anemia, acute radiation syndrome, perisurgical thrombocytopenia, post-HSCT thrombocytopenia, and liver disease.

Assessment of thrombotic risk during long-term treatment of immune thrombocytopenia with fostamatinib

Background:

Patients with immune thrombocytopenia (ITP) are at risk of bleeding and, paradoxically, thromboembolic events (TEEs), irrespective of thrombocytopenia. The risk of thrombosis is increased by advanced age, obesity, and prothrombotic comorbidities: cancer, hyperlipidemia, diabetes, hypertension, coronary artery disease, and chronic kidney disease, among others. Certain ITP treatments further increase the risk of TEE, especially splenectomy and thrombopoietin receptor agonists. Spleen tyrosine kinase (SYK) is a key signaling molecule common to thromboembolic and hemostatic (in addition to inflammatory) pathways. Fostamatinib is an orally administered SYK inhibitor approved in the USA and Europe for treatment of chronic ITP in adults.

Methods:

The phase III and extension studies included heavily pretreated patients with long-standing ITP, many of whom had risk factors for thrombosis prior to initiating fostamatinib. This report describes long-term safety and efficacy of fostamatinib in 146 patients with up to 5 years of treatment, a total of 229 patient-years, and assesses the incidence of thromboembolic events (by standardized MedDRA query).

Results:

Platelet counts ⩾50,000/µL were achieved in 54% of patients and the safety profile was as described in the phase III clinical studies with no new toxicities observed over the 5 years of follow-up. The only TEE occurred in one patient (0.7%, or 0.44/100 patient-years), who experienced a mild transient ischemic attack. This is a much lower rate than might be expected in ITP patients.

Conclusion:

This report demonstrates durable efficacy and a very low incidence of TEE in patients receiving long-term treatment of ITP with the SYK inhibitor fostamatinib.

ClinicalTrials.gov identifiers:

NCT02076399, NCT02076412, and NCT02077192.

Neonatal Fc receptor in human immunity: Function and role in therapeutic intervention

The humoral immune response provides specific, long-lived protection against invading pathogens, via immunoglobulin production and other memory functions. IgG, the most abundant immunoglobulin isotype, has the longest half-life and protects against bacterial and viral infections. The neonatal Fc receptor (FcRn) transports IgG across barriers, for example, the placenta, enhancing fetal humoral immunity to levels similar to their mothers'. Importantly, FcRn, by protecting IgG from intracellular degradation, results in an approximately 21-day circulating IgG half-life and high plasma levels; similarly, FcRn recycles albumin and is the portal of entry for enteric cytopathic human orphan (echo) virus infection. Dysregulated immune responses may lead to antibodies against self-antigens (autoantibodies), resulting in organ-specific or systemic autoimmune diseases. Autoantibody-mediated diseases have been treated by nonspecific immunoglobulin-lowering/modulating therapies, including immunoadsorption, plasma exchange, and high-dose intravenous immunoglobulin. However, targeting FcRn with specific inhibitors results in reduction in only IgG levels. The effectiveness of FcRn inhibitors in autoimmune diseases, including myasthenia gravis and immune thrombocytopenia, provides further evidence that IgG is a primary driver in these autoantibody-mediated diseases. We describe the role of FcRn in human biology, including insights that clinical testing of FcRn inhibitors have provided into FcRn biology and autoimmune disease mechanisms, allowing fact-based speculation on their therapeutic potential.

Immune thrombocytopenia (ITP) World Impact Survey (iWISh): Patient and physician perceptions of diagnosis, signs and symptoms, and treatment

Immune thrombocytopenia (ITP) is now well-known to reduce patients' health-related quality of life. However, data describing which signs and symptoms patients and physicians perceive as having the greatest impact are limited, as is understanding the full effects of ITP treatments. I-WISh (ITP World Impact Survey) was an exploratory, cross-sectional survey designed to establish the multifaceted impact of ITP, and its treatments, on patients' lives. It focused on perceptions of 1507 patients and 472 physicians from 13 countries regarding diagnostic pathway, frequency and severity of signs and symptoms, and treatment use. Twenty-two percent of patients experienced delayed diagnosis (caused by several factors), 73% of whom felt anxious as a result. Patients rated fatigue among the most frequent, severe symptom associated with ITP at diagnosis (58% most frequent; 73% most severe), although physicians assigned it lower priority (30%). Fatigue was one of the few symptoms persisting at survey completion (50% and 65%, respectively) and was the top symptom patients wanted resolved (46%). Participating physicians were experienced at treating ITP, thereby recognizing the need to limit corticosteroid use to newly-diagnosed or first-relapse patients and espoused increased use of thrombopoietin receptor agonists and anti-CD20 after relapse in patients with persistent/chronic disease. Patient and physicians were largely aligned on diagnosis, symptoms, and treatment use. I-WISh demonstrated that patients and physicians largely align on overall ITP symptom burden, with certain differences, for example, fatigue. Understanding the emotional and clinical toll of ITP on the patient will facilitate shared decision-management, setting and establishment of treatment goals and disease stage-appropriate treatment selection.

Immune thrombocytopenia (ITP) World Impact Survey (I-WISh): Impact of ITP on health-related quality of life

Immune thrombocytopenia (ITP) has a substantial, multifaceted impact on patients' health-related quality of life (HRQoL). Data describing which aspects of ITP physicians and patients perceive as having the greatest impact are limited. The ITP World Impact Survey (I-WISh) was a cross-sectional survey, including 1507 patients and 472 physicians, to establish the impact of ITP on HRQoL and productivity from patient and physician perspectives. Patients reported that ITP reduced their energy levels (85% of patients), capacity to exercise (77%), and limited their ability to perform daily tasks (75%). Eighty percent of physicians reported that ITP symptoms reduced patient HRQoL, with 66% reporting ITP-related fatigue substantially reduced patient HRQoL. Patients believed ITP had a substantial impact on emotional well-being (49%) and 63% worried their condition would worsen. Because of ITP, 49% of patients had already reduced, or seriously considered reducing their working hours, and 29% had considered terminating their employment. Thirty-six percent of patients employed at the time of the survey felt ITP decreased their work productivity, while 51% of patients with high/very high symptom burden reported that ITP affected their productivity. Note, I-WISh demonstrated substantive impact of ITP on patients' HRQoL both directly for patients and from the viewpoint of their physicians. Patients reported reduced energy levels, expressed fears their condition might worsen, and those who worked experienced reduced productivity. Physicians should be aware not only of platelet counts and bleeding but also the multi-dimensional impact of ITP on patients' lives as an integral component of disease management.

Fostamatinib is an effective second-line therapy in patients with immune thrombocytopenia

Fostamatinib demonstrated efficacy in phase 3 trials of adults with immune thrombocytopenia (ITP). Post hoc analysis compared patients who received fostamatinib as second‐line therapy (after steroids ± immunoglobulins) versus third‐or‐later‐line therapy (after ≥2 prior lines of therapy including a second‐line agent). Platelet responses ≥50 000/µl were observed in 25/32 (78%) second‐line and 54/113 (48%) third‐or‐later‐line patients. Bleeding events were less frequent in second‐line (28%) versus third‐or‐later‐line (45%) patients. Responses once achieved tended to be durable in both groups. The safety profile was similar in both groups. In this post hoc analysis, fostamatinib was more effective as second‐line than third‐or‐later‐line therapy for ITP.

Fatigue in children and adolescents with immune thrombocytopenia

Immune thrombocytopenia (ITP), an acquired autoimmune disorder of low platelets and risk of bleeding, has a substantial impact on health-related quality of life (HRQoL). Patients with ITP often report significant fatigue, although the pathophysiology of this is poorly understood. In this observational cohort of 120 children receiving second-line therapies for ITP, we assessed reports of fatigue using the Hockenberry Fatigue Scale. Children and adolescents with ITP reported a similarly high level of fatigue with 54% (29/54) of children and 62% (26/42) of adolescents reporting moderate-to-severe fatigue. There was no correlation between fatigue and age or gender. Adolescents with newly diagnosed and persistent ITP had higher mean fatigue scores than those with chronic ITP (P = 0·03). Fatigue significantly improved in children and adolescents by 1 month after starting second-line treatments, and this improvement continued to be present at 12 months after starting treatment. Fatigue scores at all time-points correlated with general HRQoL using the Kids ITP Tool, but did not correlate with bleeding symptoms, platelet count, or platelet response to treatment. Fatigue is common in children and adolescents with ITP and may benefit from ITP-directed treatment even in the absence of bleeding symptoms.