The role of T cells and myeloid-derived suppressor cells in refractory immune thrombocytopenia

Immune thrombocytopenia (ITP) is characterized by a dysregulated immune response against platelets, affecting both their destruction and production. A role for an abnormal T-cell compartment has been established in ITP pathogenesis and treatments that increase platelet counts in patients with ITP have shown improvements in T-cell profiles. On the other hand, patients who were refractory to treatment appear to retain the T-cell abnormalities as before. Myeloid-derived suppressive cells (MDSCs) are also emerging as key contributors to the immune pathology of ITP and response to treatment. In this review, we will discuss how various treatments affect the T-cell and MDSC compartments in ITP. The review will focus on studies that have examined the underlying mechanisms and/or genetic basis responsible for refractoriness to a given treatment and highlight remaining challenges in identifying factors and mechanisms to predict response to treatment.

Refractory immune thrombocytopenia in adults: Towards a new definition

Immune thrombocytopenia (ITP) is an autoimmune haematological disorder characterized by immune-mediated thrombocytopenia and a variable risk of bleeding. Despite the availability of multiple treatment options, some patients are considered refractory since they do not achieve a platelet count response to multiple treatments and are at risk of bleeding. The term 'refractory' has been used to identify this patient group; however, with the advent of multiple lines of treatment, its meaning has become ambiguous. To address this issue, we reviewed previous definitions of refractory ITP, solicited the views of ITP experts and collected data from registries to inform a definition. Twenty ITP experts who attended the 7th Expert Meeting of the Intercontinental Cooperative ITP Study Group in September 2022 answered a web-based survey: 95% felt that there was a need for a new definition of refractory ITP for clinical and research purposes. The use of the term refractory, accompanied by a clear indication of the type and timing of failed treatments, was supported by 85% of respondents. Preliminary data on the frequency of refractory patients from the McMaster and Norwegian ITP Registries demonstrated that the proportion of adult ITP patients who had failed first-line therapy, rituximab, thrombopoietin receptor agonists, any immune suppressant medication and splenectomy ranged from 0.4% to 3.8%. We propose a definition of refractory ITP that could be evaluated in future studies.

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.

Therapeutic Outcomes of High Dose-Dexamethasone versus Prednisolone + Azathioprine, Rituximab, Eltrombopag, and Romiplostim Strategies in Persistent, Chronic, Refractory, and Relapsed Immune Thrombocytopenia Patients

BACKGROUND

Primary immune thrombocytopenia (ITP) is an inflammatory autoimmune disease that can be managed with several treatment options. However, there is a lack of comparative data on the efficacy of these options in different phases of the disease.

AIM OF THE STUDY

This study aimed to evaluate the efficacy of high-dose Dexamethasone (HD-DXM), Prednisolone + Azathioprine, Rituximab, Eltrombopag, and Romiplostim schedules in persistent, chronic refractory or relapsed Egyptian ITP patients with a platelet count ≤30 × 109/L. The primary outcome measure was a sustained increase in platelet counts over 50 × 109/L for an additional 12 months without additional ITP regimens. The study also aimed to identify a suitable treatment regimen with a long remission duration for each phase of ITP.

RESULTS

Prednisolone + Azathioprine was significantly more effective in achieving an overall response in persistent patients than Romiplostim, high-dose Dexamethasone, and Rituximab. (90.9% vs. 66.6, [Odds ratio, OR: 5; confidence interval, CI 95% (0.866-28.86)], 45%, [OR: 0.082, CI 95% (0.015-0.448)] and, 25%, [OR: 30, CI 95% (4.24-211.8)], respectively, p-value < 0.01). Eltrombopag was significantly more effective in achieving a durable response in refractory ITP than HD-DXM, Rituximab, and Prednisolone; (80% compared to 32.2% [OR: 0.119, CI 95% (0.035-0.410)], 22.2% [OR:0.071, CI 95% (0.011-0.455)], and 18.1% [OR: 0.056, CI 95% (0.009-0.342)], respectively, p-value < 0.01).

CONCLUSIONS

Finally, Eltrombopag following HD-DXM showed the highest percentage of patients with complete treatment-free survival times of at least 330 days. These findings could help clinicians choose the most appropriate treatment for their patients with ITP based on the phase of the disease. This trial is registered in clinicaltrials.gov with registration number NCT05861297.

Screening for Genetic Mutations for the Early Diagnosis of Common Variable Immunodeficiency in Children With Refractory Immune Thrombocytopenia: A Retrospective Data Analysis From a Tertiary Children's Center

Aim: This study aimed to identify common variable immunodeficiency (CVID) by high-throughput next-generation sequencing (NGS) in children with refractory immune thrombocytopenia (RITP) to facilitate early diagnosis. Methods: CVID-related genetic mutations were explored in patients with RITP during 2016-2019. They were tested consecutively through NGS by the ITP team of the tertiary children hospital in China. An evaluation system was devised based on the phenotype, genetic rule, and serum immunoglobulins (Igs) of all patients with RITP. The patients were divided into highly suspicious, suspicious, and negative groups using the evaluation system. Results: Among 176 patients with RITP, 16 (9.1%) harbored CVID-related genetic mutations: 8 (4.5%) were highly suspicious of CVIDs. Five had mutations in tumor necrosis factor receptor superfamily 13B (TNFRSF13B), one in lipopolysaccharide responsive beige-like anchor protein (LRBA), one in nuclear factor kappa-B2 (NF-κB2), and one in caspase recruitment domain11 (CARD11). Others were classified into the suspicious group because the clinical phenotype and pedigree were suggestive, yet insufficient, for diagnosis. Repeated infection existed in all patients. Two had an allergic disease. Positive autoimmune serologies were noted in 62.5%. Five had a definite positive family history. The median serum immunoglobulin (Ig)A, IgG, and IgM levels were 0.3875, 6.14, and 0.522 g/L, respectively. Nearly 85.7% of patients had insufficient serum IgA levels, while 37.5% had low IgG and IgM levels. Conclusions: High-throughput NGS and a thorough review of the medical history are beneficial for the early diagnosis of patients without any significant clinical characteristics, distinguishing them from those with primary pediatric ITP. The cases suspicious of CVID need further investigation and follow-up to avoid deterioration.

Romiplostim in children with chronic immune thrombocytopenia (ITP): the French experience

A minority of children with chronic immune thrombocytopenia (ITP) require therapeutic intervention to prevent haemorrhagic risk. This retrospective national study evaluated romiplostim in childhood non-responsive or refractory chronic ITP. Between 2009 and 2012, 10 patients whose Buchanan score was 3-4 were treated with romiplostim. The median duration of thrombocytopenia was 1·9 years (0·8-15). The median duration of romiplostim treatment was 9 months (3-36). A response was observed in 5/10 patients (one complete, four partial). No serious adverse effect was noticed. The long-term benefit/risk balance of this innovative treatment is currently recorded by Centre de Référence National des Cytopénies Auto-immunes de l'Enfant.