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

Tapering and Sustained Remission of Thrombopoietin Receptor Agonists (TPO-RAs): Is it Time for Paediatric ITP?

Thrombopoietin receptor agonists (TPO-Ras; romiplostim/eltrombopag/avatrombopag) have demonstrated high efficacy rates (59-88%) and a good safety profile in clinical trials with adult patients with immune thrombocytopenia (ITP). Similar efficacy and safety results have been observed with romiplostim and eltrombopag in paediatric cohorts. Continuous treatment with TPO-RAs has shown durable responses with long-term use, up to 3 years. The effect of TPO-RAs was generally considered transient, as platelet counts tended to drop to baseline values after a short period of time (about 2 weeks), unless treatment was maintained. Several groups have reported successful discontinuation of TPO-RAs without the need for concomitant treatments. This is referred to as sustained remission off treatment (SROT). Both short- and medium-term treatment with TPO-RAs may reduce costs to our healthcare systems and, more importantly, may reduce the potential side effects that may be associated with continuous TPO-RA treatment. The issue of tapering and discontinuation of TPO-RAs in paediatric patients with ITP has received little attention to date. Given that paediatric ITP has much higher rates of spontaneous remission than ITP in adults, we consider that the possibility of SROT of TPO-RAs in paediatric patients with ITP is a neglected but very relevant issue in this subtype of the disease.

Lightening the load for paediatric ITP: The importance of health-related quality of life

In their paper, Klaassen et al. present their findings on the revised Kids ITP Tools (KIT). This important work provides an update to the validated measure for evaluating health-related quality of life (HRQoL) in children with immune thrombocytopenia (ITP). ITP, an acquired autoimmune disorder, results in thrombocytopenia and places children at risk for significant bleeding. Thankfully, the majority of children with ITP will have a brief disease course and no or mild bleeding symptoms. The rarity of severe bleeding events or the development of chronic disease provides a challenge with regard to clinical trial design, making alternative measures of pharmacological efficacy extremely important. Commentary on: Dhir et al. Quality of life in childhood immune thrombocytopenia: Revision of the Kids' ITP Tools (KIT). Br J Haematol 2024 (Online ahead of print). doi: 10.1111/bjh.19662.

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.

Frequency of toll-like receptor 4 variants and association with treatment response in children with primary immune thrombocytopenia

OBJECTIVES

To investigate the frequency of toll-like receptor 4 (TLR4) variants c.896A>G (p.Asp299Gly) and c.1196C>T (p.Thr399Ile) among Egyptian children with primary immune thrombocytopenia (pITP), and their association with disease course and response to treatment.

METHODS

A case-control study that included 80 children with pITP and 50 age- and sex-matched healthy controls. TLR4 c.896A>G and c.1196C>T variants were genotyped using polymerase chain reaction-restriction fragment length polymorphism. Patients were classified according to their response to treatment after 3 months as responders and nonresponders.

RESULTS

Compared with controls, children with pITP had significantly higher minor allele frequencies of TLR4 p.Asp299Gly (16.25% vs. 6%, odds ratio [OR] 3.04, 95% confidence interval [CI]: 1.16-9.36, p = .014) and p.Thr399Ile (20% vs. 4%, OR 6, 95% CI: 2.02-24.01, p < .001). The presence of p.Asp299Gly variant was significantly associated with chronic ITP (OR 7.78, 95% CI: 2.04-35.69, p < .001) and non-response to therapy with steroid (OR 11.67, 95% CI: 1.32-104.08, p = .012), but not thrombopoietin-receptor agonist (OR 1.67, 95% CI: 0.35-8.19, p = .464). Likewise, having p.Thr399Ile variant was significantly associated with chronic ITP (OR 5.14, 95% CI: 1.6-17.4, p = .002) and non-response to therapy with steroid (OR 6.1, 95% CI: 1.01-49.06, p = .046) but not thrombopoietin-receptor agonist (OR 1.57, 95% CI: 0.33-7.58, p = .515).

CONCLUSION

The presence of TLR4 p.Asp299Gly or p.Thr399Ile variant may be associated with ITP predisposition, chronicity, and non-response to upfront steroid therapy. These findings enhance our understanding of the complex pathophysiology of pITP with potentially important clinical implications.

Prediction of the Clinical Course of Immune Thrombocytopenia in Children by Platelet Kinetics

Childhood immune thrombocytopenia (ITP) is a rare autoimmune disorder characterized by isolated thrombocytopenia. Prolonged ITP (persistent and chronic) leads to a reduced quality of life for children in many domains. To provide optimal support for children, with ITP, it is important to be able to predict those who will develop prolonged ITP. This study aimed to develop a mathematical model based on platelet recovery that allows the early prediction of prolonged ITP. In this retrospective study, we used platelet counts from the 6 months following the diagnosis of ITP to model the kinetics of change in platelet count using a pharmacokinetic-pharmacodynamic model. In a learning set (n = 103), platelet counts were satisfactorily described by our kinetic model. The Kheal parameter, which describes spontaneous platelet recovery, allowed a distinction between acute and prolonged ITP with an area under the curve (AUC) of 0.74. In a validation set (n = 58), spontaneous platelet recovery was robustly predicted using platelet counts from 15 (AUC = 0.76) or 30 (AUC = 0.82) days after ITP diagnosis. In our model, platelet recovery quantified using the kheal parameter allowed prediction of the clinical course of ITP. Future prospective studies are needed to improve the predictivity of this model, in particular, by combining it with the predictive scores previously reported in the literature.

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.

Thrombopoietin Receptor Agonists (TPO-RAs): Drug Class Considerations for Pharmacists

The thrombopoietin receptor agonists (TPO-RAs) romiplostim, eltrombopag, avatrombopag, and lusutrombopag carry unique US Food and Drug Administration (US FDA)- and European Medicines Agency (EMA)-approved indications and may be used to increase platelet counts in a variety of conditions. Current indications for available TPO-RAs include treatment of chronic immune thrombocytopenia (ITP) in cases of insufficient response to prior treatment (avatrombopag, eltrombopag, romiplostim), management of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure (avatrombopag, lusutrombopag), management of severe aplastic anemia (eltrombopag), and management of thrombocytopenia associated with interferon-based therapy for hepatitis C (eltrombopag). Across current indications, pharmacists can assist in stabilizing platelet counts and help to reduce large undulations commonly seen when starting, stopping, or transitioning between these agents. If therapy modifications may benefit the patient, pharmacists should discuss possible changes with the patient's treatment team or treating physician. When used for ITP, romiplostim, eltrombopag, and avatrombopag stimulate TPO receptors on hematopoietic stem cells (also known as c-Mpl, or CD110) to promote platelet production; however, romiplostim is the only TPO-RA that binds at the same site as endogenous TPO. These subtle mechanistic differences may explain why switching TPO-RA may be clinically advantageous in some situations. As pharmacists are called to counsel patients on TPO-RA use, a deep understanding of potential adverse events and management strategies, as well as appropriate monitoring, will increase the likelihood that patients meet their goals of therapy in the shortest timeframe. Other uses of TPO-RAs are also discussed in this review, including use following hematopoietic stem cell transplant, use in myelodysplastic syndrome, and use in chemotherapy-induced thrombocytopenia.