Efficacy and tolerability of old and new drugs used in the treatment of immune thrombocytopenia: Results from a long-term observation in clinical practice

Epidemiology, Treatment Patterns, and Cost Analysis of Immune Thrombocytopenia in Spain between 2014 and 2020: A Population-based Study

Background  Immune thrombocytopenia (ITP) is characterised by low platelet counts and often leads to bleeding, fatigue, and reduced health-related quality of life. Methods  This observational, retrospective, population-based study using BIG-PAC® database included Spanish paediatric and adult patients with primary ITP diagnosed in primary care and hospitals between 2014 and 2020 (median follow-up: 4 years). Epidemiology, baseline/clinical characteristics, treatment trends, healthcare resources and costs were analysed. Results  The BIG-PAC® database contains records of 1,818,588 patients; 170 adults and 27 children with ITP were included in our analysis. ITP prevalence and annual incidence per 100,000 were estimated in 10.8 (2.8 in chronic ITP [cITP] patients) and 1.5 (0.3 in cITP patients), respectively. Epistaxis was the most common bleeding event, followed by genitourinary and gastrointestinal bleeding; >50%/> 75% of ITP/cITP patients reported fatigue. Chronic patients had lower platelet counts at baseline and required more transfusions. Corticosteroids, immunosuppressants, and thrombopoietin receptor agonists were the most used agents in first-, second- and third-line treatment, respectively. Thirty-five patients, all of them in chronic phase, underwent splenectomy. Patients had on average 13.9, 6.6, and 1.2 visits/year to primary care, haematology/internal medicine, and emergency departments, respectively. More than one-fourth of adult patients took on average 16.3 days of sick leave annually. Mean annual total health care costs were €10,741 (ITP patients) and €19,809 (cITP patients). Conclusion  This is the first study to provide an overall perspective on the situation of the Spanish ITP population in terms of epidemiology, treatment trends, health care resources and costs, highlighting unmet patient needs, and direct and indirect costs/resource use between 2014 and 2020.

Is Immune Thrombocytopenia and its Treatment Associated with Sarcopenia?

BACKGROUND

Immune thrombocytopenia (ITP) is defined as an isolated platelet count less than 100 × 109/L in the absence of other causes of thrombocytopenia. Sarcopenia is a body-wide muscular disorder with a progressive nature that leads to reduced mobility, physical disability, falls, and poor quality of life. We aimed to evaluate the frequency of objectively diagnosed sarcopenia in patients with ITP and to determine whether ITP therapies have sarcopenic effects.

METHODS

This prospective study included patients who were followed up with ITP in the hematology outpatient clinic. Patients who had received corticosteroids within 3 months were excluded. The handgrip strength test, appendicular skeletal muscle mass (ASMM), ASMM/height2 value, soft lean mass (SLM), trunk soft lean mass (SLMT), and the 6-min walking speed test were applied for muscular evaluations and physical performance assessment.

RESULTS

We included 53 patients (female/male: 73.58%/26.42%). While sarcopenia was not observed in 77.36% of ITP patients, possible sarcopenia was diagnosed in 9.43% and confirmed sarcopenia in 13.21%. Severe sarcopenia was not seen in any of the patients. Loss of muscle strength was observed in 22.64% of patients. SLM was found to be low in 92.45%.

CONCLUSION

Sarcopenia may be more frequent among patients with ITP compared to the population, and it is important to note that 92.45% of patients had low SLM and 54.72% had low SLMT. Eltrombopag therapy might be beneficial as demonstrated by higher SLM, ASMM, and ASMM/height2 values.

Checkpoint inhibitors

Immune checkpoint inhibitors are a class of antineoplastic therapies that unleash immune cells to kill malignant cells. These medications commonly cause immune-related adverse effects due to activated adaptive and innate immune cells, autoantibody production, and/or cytokine dysregulation. Hematologic toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses. Management is challenging because one must attend to the hematologic toxicity while simultaneously attending to the malignancy, with the imperative that therapeutic effects be maintained or minimally interrupted when possible.

Risk factors of significant relapse and appropriate maintenance therapy strategy in SLE-associated immune thrombocytopenia

Background:

Systemic lupus erythematosus–associated immune thrombocytopenia (SLE-ITP) is characterized by relapse. The risk factors of relapse and appropriate maintenance therapy strategy deserve further exploration.

Objectives:

To determine the risk factors for relapse and appropriate maintenance therapy in significant SLE-ITP patients (a platelet count ⩽30 × 10⁹/l) after the first complete response.

Design:

Retrospective cohort study using the medical records of 105 patients diagnosed as significant SLE-ITP in Fujian Medical University Union Hospital during December 2012 to March 2021. Patients were followed through a call for observations in January 2022.

Methods:

Data including demographics, initial clinical feature, induction and maintenance therapy, and outcome at the end of follow-up were analyzed. Risk factors for significant relapse were analyzed using multivariate logistic regression models. The cumulative hazard of significant relapse and the duration of response were estimated, and the differences in outcome between groups were compared using the Cox regression analysis.

Results:

A total of 65 significant SLE-ITP patients were eligible for the final analysis. Median [interquartile range (IQR)] follow-up duration and median [IQR] duration of response were 62.2 [41.0–79.6] months and 43.4 [20.3–68.7] months, respectively. After the first complete response, 19/65 (29.2%) had a significant relapse. Compared with sustained clinical remission (SCR) + sustained response (SR) group, significant relapse group had a higher proportion of discontinued patients (47.4% versus 8.7%, p = 0.001). Among the 13 discontinued patients, the duration of maintenance therapy of the patients in significant relapse group was significantly shorter than that of the patients in SCR + SR group (months, median [IQR], 43.1 [32.0–62.4] versus 12.0 [5.1–22.0], p = 0.009). Multivariate logistic regression analysis showed that drug withdrawal was an independent risk factor for significant relapse [odds ratio (OR) = 10.4, confidence interval (CI) 95% 2.2–47.8, p = 0.003]. There was no significant difference between glucocorticoids (GCs) + hydroxychloroquine (HCQ) group and GCs + HCQ + immunosuppressive agents (ISAs) group in significant relapse rate (26.7% versus 22.2%, p > 0.05). The two SR curves of GCs + HCQ and GCs + HCQ+ ISA group basically coincided by the Cox regression analysis, demonstrating comparable long-term outcomes (p > 0.05).

Conclusion:

Drug withdrawal, especially abrupt withdrawal with insufficient duration of maintenance therapy, is an independent risk factor for significant relapse of SLE-ITP. HCQ combined with GCs is expected to be the first choice of the maintenance therapy for SLE-ITP patients.

Treatment of immune thrombocytopenia in Australian adults: A multicenter retrospective observational study

Background

In Australia, prescribing restrictions limit access to internationally recommended second‐line therapies such as rituximab and thrombopoietin agonists (TPO‐A) (eltrombopag and romiplostim). Subsequent lines of therapy include an array of immunosuppressive and immune‐modulating agents directed by drug availability and physician and patient preference.

Objectives

The objective of the study was to describe the use of first and subsequent lines of treatment for adult immune thrombocytopenia (ITP) in Australia and to assess their effectiveness and tolerability.

Patients/Methods

A retrospective review of medical records was conducted of 322 patients treated for ITP at eight participating centers in Australia between 2013 and 2020. Data were analyzed by descriptive statistics and frequency distribution using pivot tables, and comparisons between centers were assessed using paired t tests.

Results

Mean age at diagnosis of ITP was 48.8 years (standard deviation [SD], 22.6) and 58.3% were women. Primary ITP was observed in 72% and secondary ITP in 28% of the patients; 95% of patients received first‐line treatment with prednisolone (76%), dexamethasone (15%), or intravenous immunoglobulin (48%) alone or in combination. Individuals with secondary ITP were less steroid dependent (72% vs. 76%) and required less treatment with a second‐line agent (47% vs. 58%) in the study sample. Over half (56%) of the cohort received treatment with one or more second‐line agents. The mean number of second‐line agents used for each patient was 1.9 (SD, 1.2). The most used second‐line therapy was rituximab, followed by etrombopag and splenectomy. These also generated the highest rates of complete response (60.3%, 72.1%, and 71.8% respectively). The most unfavorable side effect profiles were seen in long‐term corticosteroids and splenectomy.

Conclusion

A wide range of “second‐line” agents were used across centers with variable response rates and side effect profiles. Findings suggest greater effectiveness of rituximab and TPO‐A, supporting their use earlier in the treatment course of patients with ITP across Australia.

Refractory primary immune thrombocytopenia (ITP): current clinical challenges and therapeutic perspectives

Chronic primary immune thrombocytopenia (ITP) can today benefit from multiple therapeutic approaches with proven clinical efficacy, including rituximab, thrombopoietin receptor agonists (TPO-RA), and splenectomy. However, some ITP patients are unresponsive to multiple lines of therapy with prolonged and severe thrombocytopenia. The diagnosis of refractory ITP is mainly performed by exclusion of other disorders and is based on the clinician's expertise. However, it significantly increases the risk of drug-related toxicity and of bleedings, including life-threatening events. The management of refractory ITP remains a major clinical challenge. Here, we provide an overview of the currently available treatment options, and we discuss the emerging rationale of new therapeutic approaches and their strategic combination. Particularly, combination strategies may target multiple pathogenetic mechanisms and trigger additive or synergistic effects. A series of best practices arising both from published studies and from real-life clinical experience is also included, aiming to optimize the management of refractory ITP.

Immune thrombocytopenia with clinical significance in systemic lupus erythematosus: a retrospective cohort study of 90 patients

OBJECTIVES

To describe the characteristics, treatment, and outcome of patients with immune thrombocytopenia with clinical significance (ITPCS) associated with systemic lupus erythematosus (SLE).

METHODS

This retrospective multicentre study included SLE patients who experienced ≥1 ITPCS (defined as ITP with attributable bleeding disorders and/or a platelet count <30 x109/L). Other causes of secondary thrombocytopenia were excluded. Major bleeding event (MBG) was defined as Khellaf score>8 and/or WHO score>2.

RESULTS

A total of 90 patients were included, the median (range) follow-up duration was 80 (6-446) months. ITP was diagnosed before SLE in 25 patients. They presented high rate of autoimmune haemolytic anaemia (15%), antiphospholipid antibody (62%), and antiphospholipid syndrome (19%). The 25 (28%) patients who experienced MBG had significantly more bleedings at ITP diagnosis and higher bleeding scores, and serositis and thrombosis during follow-up. They required significantly more treatment lines, transfusions, and hospitalizations. The 11 (12%) patients who experienced no bleeding event presented a significantly more restricted SLE phenotype (cutaneous and/or articular). Patients received a mean (range) of 4.2 (1-11) treatment lines. Corticosteroids and hydroxychloroquine allowed ITPCS overall response in one third of patients. The median relapse-free survival of rituximab (n = 34), azathioprine (n = 19), mycophenolate mofetil (n = 8), thrombopoietin-receptor agonists (n = 16), and splenectomy (n = 19) were 53, 31.5, 61, 24.5, and 78 months, respectively. Four patients experienced thrombotic events after splenectomy and one occurred under thrombopoietin-receptor agonist treatment.

CONCLUSION

SLE-ITCS patients displayed a high rate of haematological abnormalities and MBG patients exhibited higher morbidity. Management of thrombocytopenia was highly heterogeneous and many options seem viable.

Hematologic complications of immune checkpoint inhibitors

Immune checkpoint inhibitors are a class of anti-neoplastic therapies that unleash immune cells to kill malignant cells. There are currently 7 medications FDA-approved for the treatment of 14 solid tumors and 2 hematological malignancies. These medications commonly cause immune-related adverse effects due to overactive T lymphocytes, autoantibody production, and/or cytokine dysregulation. Hematological toxicities are rare and of uncertain mechanism, and therefore management is often based on experiences with familiar conditions involving these perturbed immune responses, such as autoimmune hemolytic anemia, immune thrombocytopenia, and idiopathic aplastic anemia. Management is challenging because one must attend to the hematological toxicity while simultaneously attending to the malignancy, with the imperative that effective cancer therapy be maintained or minimally interrupted if possible. The purpose of this review is to assist clinicians by providing a clinical and pathophysiological framework in which to view these problems.

A retrospective analysis of 122 immune thrombocytopenia patients treated with dapsone: Efficacy, safety and factors associated with treatment response

BACKGROUND

The optimum second-line treatment or best sequence of treatments for immune thrombocytopenia (ITP) are yet to be determined. Our institution has accumulated extensive experience regarding the use of dapsone as second-line therapy for ITP.

OBJECTIVES

We aimed to assess the efficacy rate and safety of dapsone treatment in ITP patients.

PATIENTS/METHODS

Here we report our experience in a retrospective study, including 122 patients, with a median treatment duration with dapsone of 6 months and a median follow-up period of 3.4 years.

RESULTS

The overall response rate in this cohort was 66%, including 24% of complete responses. Among responders, in 24% a relapse occurred while on treatment. Therefore, a sustained response was observed in 51% of patients. Interestingly, 81% of the responders maintained the response after the interruption of treatment, for a median time of 26 months. Side effects were reported in 16% of the patients in this cohort and treatment was interrupted due to side effects in 11% of patients. The main cause in these cases was hemolytic anemia and methemoglobinemia. Reductions in hemoglobin levels during the use of dapsone were seen in 94% of the patients. Responders presented significantly greater reductions in their hemoglobin levels than nonresponders did: median hemoglobin drop of 1.9 g/dl vs. 1.2 g/dl (p = .004).

CONCLUSIONS

Our findings suggest that dapsone has adequate efficacy and is well tolerated. Although the mechanism of action is still unclear, our observation that the degree in the drop of hemoglobin is greater in responders suggest a possible role of the blockage of the reticuloendothelial system in the therapeutic effect of the drug.

Safety and efficacy of azathioprine in immune thrombocytopenia

BACKGROUND

Immune thrombocytopenia (ITP) is a benign hematological disorder characterized by low platelet counts in peripheral blood and spectrum of various bleeding manifestations. Azathioprine is one of the effective, readily available, and affordable immunosupressants available for ITP management in developing countries. We aimed to study the efficacy and long-term safety profile of our patients with ITP who were treated with azathioprine.

METHOD

This was a retrospective, single-center study conducted at a tertiary care hospital in Northern India. The patients who had received at least one line of therapy before receiving azathioprine were included in this study. All patients received oral azathioprine at a dose of 1 mg/kg/day (50 mg or 100 mg tablet formulations were used), which was increased up to 2 mg/kg/day depending upon the response and adverse effects.

RESULT

Sixty-three patients were analyzed. Their median age was 28 years (range 15-68); 29/63 patients (46.03%) were females. The median duration from diagnosis to azathioprine initiation was 539 days (323 days-980.5 days). The patients included in the study had received a median of 3 (range 1-6) prior lines of therapies; 38/63 patients (60.32%) had received ≥3 prior therapies. Six patients (9.5%) had relapsed after splenectomy, and 16 patients (25.4%) had relapsed after receiving rituximab. The mean baseline platelet count was 10000/μL. The median time to response was 95 days (90 days-not reached) and the cumulative overall response rate (complete and partial response) at day 90 was 38.1%. Only one patient achieved complete response with azathioprine in our study. The cumulative rate of relapse at five years was 21.2%. Twenty-six patients stopped azathioprine after achieving some response (CR/PR) with Azathioprine for a median duration of 1067.5 days (range: 236 days-2465 days). They were followed up for a median of 870 days (range: 392 days-1928 days), and twelve of them relapsed. Twenty-six patients (26/63, 41.27%) reported one or more adverse events while on azathioprine. Leucopenia was the most frequent adverse event, followed by anemia and hepatobiliary laboratory abnormalities. Serious adverse events (grade ≥3 CTCAEv4) were noted in three patients (4.7%). One patient succumbed to severe sepsis multiorgan dysfunction while being on treatment.

CONCLUSION

We conclude that azathioprine has a good response rate in chronic ITP patients. It is well-tolerated with minimal and manageable side effects.

Prospective Evaluation of the First Option, Second-Line Therapy in Childhood Chronic Immune Thrombocytopenia: Splenectomy or Immunomodulation

OBJECTIVE

To describe 4 subgroups of pediatric patients treated with splenectomy, hydroxychloroquine, azathioprine, or rituximab as the first-option, second-line treatment for chronic immune thrombocytopenia.

STUDY DESIGN

Selection of patients with chronic immune thrombocytopenia from the French national prospective cohort of pediatric autoimmune cytopenia OBS'CEREVANCE and VIGICAIRE study, treated by splenectomy, hydroxychloroquine, azathioprine, or rituximab as a first second-line treatment.

RESULTS

For 137 patients, treated between 1989 and 2016, the median follow-up after diagnosis and after treatment initiation was 8.5 (2.8-26.4) years and 4.7 (1.1-25.1) years, respectively. Median age at diagnosis and at initiation of treatment were 9 (0.7; 16) and 12 (2; 18.1) years, respectively without significant difference between subgroups. For the whole cohort, 24-month event-free survival was 62% (95% CI 55; 71). It was 85% (95% CI 77; 95) for the 56 patients treated with splenectomy, 60% (95% CI 44; 84) for the 23 patients treated with rituximab, 46% (95% CI 30; 71) for the 24 patients treated with azathioprine, and 37% (95% CI 24; 59) for the 34 patients treated with hydroxychloroquine (log-rank P < .0001). For the splenectomy subgroup, being older than 10 years at splenectomy tended to improve event-free survival (P = .05). Female teenagers with antinuclear antibody positivity benefited from hydroxychloroquine therapy.

CONCLUSIONS

This national study, limiting pitfalls in the analysis of the effects of second-line therapies, showed that splenectomy remains the treatment associated with the better response at 24 months.

A Case of Epistaxis as the First Sign of Acute Idiopathic Thrombocytopenic Purpura

Idiopathic thrombocytopenic purpura (ITP) is an acquired thrombocytopenia caused by the action of autoantibodies against platelet antigens. It is traditionally defined by a platelet count of less than 10 × 10⁴/μL. Most patients with ITP are asymptomatic; however, symptoms have been confirmed in some cases. Conversely, it is very rare to find epistaxis as the first sign of ITP. We report the case of an 84-year-old man who came to the ear, nose, and throat department with severe and repeated epistaxis. We decided to keep him hospitalized as it was very difficult to stop the nasal bleeding. A full blood count showed a platelet level of only 1000/μL. Hematologic results confirmed the diagnosis of ITP. The patient underwent treatment with intravenous gamma-globulin, platelet transfusions, and romiplostim with a favorable response.

Clinical Phenotype and Response to Different Lines of Therapy in Elderly with Immune Thrombocytopenia: A Retrospective Study

Purpose

Insufficient knowledge of primary immune thrombocytopenia purpura (ITP) in the elderly, together with a lack of clinical trial data, has resulted in wide variation in treatments. Here, we present a study focused on clinical characteristics of ITP in older subjects at diagnosis integrated with the subsequent course of the disease and treatment history.

Methods

In a retrospective monoinstitutional study, we evaluated >65-year-old patients with primary ITP. Clinical characteristics at the time of diagnosis were described and analyzed. We aimed to delineate whether subsequent lines of therapy influenced the number of relapses. In addition to initial regimens, we reported subsequent treatments and the impact on relapse trends.

Results

A total of 50 patients (56% males, mean age 78 years) were included. With regard to clinical variables at diagnosis, statistical significance was found for Eastern Cooperative Oncology Group performance status 1 (46% of patients, p<0.0001), presence of three comorbidities (36% of patients, p<0.0001), World Health Organization grade 0 bleeding (46%, p=0.0001), and World Health Organization grade 1 bleeding (42%, p=0.0009). For bleeding sites, the most frequent were skin or mucosa (40%, p=0.0477). A decrease in platelet count was correlated with moderate or severe bleeding (ρ=-0.52, p=0.0001) and viscera or skin/mucosa + viscera site (ρ=-0.50, p=0.0002). Finally, a decreasing number of patients required treatment from first-line therapy to sixth (p<0.0001). Relapse was most frequent before second-line therapy (54%, p<0.0001) and less frequent before fivth and sixth (4%, p=0.0072; 2%, p=0.0027).

Conclusion

ITP in older age poses considerable challenges, so specific management strategies should be considered to optimize outcomes. Our findings provide evidence of an inverse relationship between lines of therapy and timing of relapses. This study does not exclude the possibility that agents used after first-line therapy may have an impact on the response and modify the unfavorable course of ITP.

More about the combination of rituximab, cyclosporine and dexamethasone in the treatment of chronic ITP. A useful option on an environment with limited resources

Treatment of chronic primary immune thrombocytopenia (ITP) is challenging especially with limited resources and therapy-related complications. This prospective interventional study assessed the efficacy and safety of triple therapy(TT4); a combination treatment of oral dexamethasone 40 mg for days1-4, oral cyclosporine A 2-3 mg/kg daily for 28 consecutive days and intravenous rituximab 100 mg for days7,14,21 and 28 among 40 patients with ITP who failed previous 2 or more treatment options. Our aim was to maintain platelet count ≥ 30 X 10⁹/L without any obvious bleeding at any point in the study. Platelet counts were assessed weekly for a month then monthly for 2 years to evaluate the long-term response. TT4 was well tolerated and induced a good response with a significant increase in the mean platelet count after the 1^st, 2^nd, 3^rd, and 4^thweek compared to the baseline. Patients with mean platelet count ≥ 30 X 10⁹/L at the 6^th month were 75% (30/40 patients). Treatment free survivals (TFS) at 12 and 24 months were 93.3% (28/30 patients) and 80% (24/30 patients) respectively. TT4 is an effective treatment option that maintained platelet count in the desired level and induced a higher sustained response, especially in an environment with limited resources.

Treatment of primary and secondary immune thrombocytopenia

PURPOSE OF REVIEW

Medical therapies for the treatment of immune thrombocytopenia (ITP) complicating SLE are increasingly being investigated as alternatives to splenectomy and IVIG. The purpose of this review is to highlight the therapies that are utilized in the treatment of primary ITP and ITP secondary to lupus.

RECENT FINDINGS

Corticosteroids are still the standard initial treatment of ITP, with the addition of IVIG when a rapid response is needed. There are few studies dedicated to assessing the efficacy of disease-modifying antirheumatic (DMARD), biologic, and nonimmunosuppressive agents as treatment for lupus thrombocytopenia/lupus ITP. Rituximab and thrombopoeitin mimetics have been the most extensively studied therapies for primary ITP in recent years. Results of trials show adequate initial responses; however, the duration of therapy and sustainability of responses are variable. Splenectomy is less often utilized.

SUMMARY

Although corticosteroids, intravenous immunoglobulin and splenectomy have proven to be effective measures to treat immune thrombocytopenia, newer studies have demonstrated positive outcomes of immunosuppressives and thrombopoeitin mimetics. In most cases, the reported duration of therapy was not prolonged. More studies are needed to fully assess the effect of medical therapy in lupus ITP and to determine how long to continue maintenance therapy.

Revisiting the management of chronic ITP; a randomized controlled clinical trial

The balance between therapy effectiveness and economic efficiency in chronic immune thrombocytopenia (ITP) becomes more confusing. This single-center open label randomized controlled trial evaluates the effectiveness and safety of hydroxychloroquine in chronic ITP patients against other affordable second-line treatments. It is registered under number (NCT03229746) at Clinical Trials.gov. 120 patients were recruited and randomly allocated to three arms of hydroxychloroquine, vincristine, and azathioprine equally. Platelet counts of more than 100 × 10⁹/L were interpreted as complete response (CR), while response (R) was determined as platelet counts ranging from 30 × 10⁹/L to less than 100 × 10⁹/L with the doubling of the pretreatment platelet count. Overall response (OR) was defined to include both CR and R. Patients were monitored every 6 weeks for a total of 24 weeks. The population baseline characteristics regarding age, sex, duration of the disease, baseline platelets count, and presence of antinuclear antibodies ANA or antiplatelet antibodies were similar among tested groups. There was a significant difference in the overall response between hydroxychloroquine (80.6%) and azathioprine (55.9%) (p-value <0.05). This difference was not significant between hydroxychloroquine and vincristine group (63.2%) (p-value = 0.09). This study proves that hydroxychloroquine can contribute to the therapy of chronic ITP especially as an affordable and well-tolerated drug.

Mechanisms and therapeutic prospects of thrombopoietin receptor agonists

The second-generation thrombopoietin (TPO) receptor agonists eltrombopag and romiplostim are potent activators of megakaryopoiesis and represent a growing treatment option for patients with thrombocytopenic hematological disorders. Both TPO receptor agonists have been approved worldwide for the treatment of children and adults with chronic immune thrombocytopenia. In the EU and USA, eltrombopag is approved for the treatment of patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy and in the USA for the first-line treatment of severe aplastic anemia in combination with immunosuppressive therapy. Eltrombopag has also shown efficacy in several other disease settings, for example, chemotherapy-induced thrombocytopenia, selected inherited thrombocytopenias, and myelodysplastic syndromes. While both TPO receptor agonists stimulate TPO receptor signaling and enhance megakaryopoiesis, their vastly different biochemical structures bestow upon them markedly different molecular and functional properties. Here, we review and discuss results from preclinical and clinical studies on the functional and molecular mechanisms of action of this new class of drug.

Treatments for Primary Immune Thrombocytopenia: A Review

Immune thrombocytopenic purpura (ITP) is an autoimmune condition that affects nearly 1:10,000 people in the world. It is traditionally defined by a platelet count of less than 100 x 109L, but treatment typically depends on symptomology rather than on the platelet count itself. For primary idiopathic ITP, corticosteroids have been the standard first-line of treatment for symptomatic patients, with the addition of intravenous immune globulin (IVIG) or Rho(D) immune globulin (anti-RhD) for steroid-resistant cases. In cases of refractory or non-responsive ITP, second-line therapy includes splenectomy or rituximab, a monoclonal antibody against the CD20 antigen (anti-CD20). In patients who continue to have severe thrombocytopenia and symptomatic bleeding despite first- and second-line treatments, the diagnosis of "chronic refractory ITP" is appropriate, and third-line treatments are evaluated. This manuscript describes the efficacy of different treatment options for primary ITP and introduces the reader to various third-line options that are emerging as a means of treating chronic refractory ITP.

Eltrombopag in Immune Thrombocytopenia, Aplastic Anemia, and Myelodysplastic Syndrome: From Megakaryopoiesis to Immunomodulation

Eltrombopag is an orally available thrombopoietin receptor agonist indicated for the treatment of immune thrombocytopenia (ITP). Beyond the effect on megakaryopoiesis, the drug also showed a stimulating effect on the hematopoietic stem cell with consistent clinical efficacy in aplastic anemia (AA) and myelodysplastic syndromes (MDS). Eltrombopag is highly effective in ITP and less so in AA and MDS. This observation underlines the importance of residual normal hematopoiesis, which is maximal in ITP, minimal/absent in AA, and dysregulated in MDS. In ITP, the drug at 50-75 mg daily induced up to 85% responses both in clinical trials and real-life studies, with the possibility of tapering and discontinuation. In AA, eltrombopag at 150 mg daily was effective in about 40% of cases relapsed/refractory to standard immunosuppression or ineligible for bone marrow transplant. In MDS, the drug seems less effective, with responses in about a quarter of patients at various schedules. The efficacy of eltrombopag in ITP, AA, and MDS suggests the existence of common immune-pathological mechanisms in these diseases, including autoimmunity against peripheral blood cells and bone marrow precursors, as well as a possible evolution of one condition into the other. Additional mechanisms of action emerging from the clinical use of eltrombopag include modulation of T-regulatory cells, restoration of Fc-γ receptor balance in phagocytes, and an iron-mobilizing effect. In this review, we analyzed the most recent literature on eltrombopag use and efficacy in patients with ITP, AA, and MDS, exploring the basis for different dosing, combined treatments, and discontinuation in each context.