Thrombopoietin receptor agonists in refractory immune thrombocytopenia: differential responses to eltrombopag and romiplostim: a case report and possible explanations

Switching from eltrombopag to hetrombopag in patients with primary immune thrombocytopenia: a post-hoc analysis of a multicenter, randomized phase III trial

While studies have explored the feasibility of switching between various thrombopoietin receptor agonists in treating immune thrombocytopenia (ITP), data on the switching from eltrombopag to hetrombopag remains scarce. This post-hoc analysis of a phase III hetrombopag trial aimed to assess the outcomes of ITP patients who switched from eltrombopag to hetrombopag. In the original phase III trial, patients initially randomized to the placebo group were switched to eltrombopag. Those who completed this 14-week eltrombopag were eligible to switch to a 24-week hetrombopag. Treatment response, defined as a platelet count of ≥ 50 × 109/L, and safety were evaluated before and after the switch. Sixty-three patients who completed the 14-week eltrombopag and switched to hetrombopag were included in this post-hoc analysis. Response rates before and after the switch were 66.7% and 88.9%, respectively. Among those with pre-switching platelet counts below 30 × 109/L, eight out of 12 patients (66.7%) responded, while eight out of nine patients (88.9%) with pre-switching platelet counts between 30 × 109/L and 50 × 109/L responded post-switching. Treatment-related adverse events were observed in 50.8% of patients during eltrombopag treatment and 38.1% during hetrombopag treatment. No severe adverse events were noted during hetrombopag treatment. Switching from eltrombopag to hetrombopag in ITP management appears to be effective and well-tolerated. Notably, hetrombopag yielded high response rates, even among patients who had previously shown limited response to eltrombopag. However, these observations need to be confirmed in future trials.

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.

Sequential Use of Romiplostim after Eltrombopag for Refractory Thrombocytopenia in Hydrocarbon-Induced Myelodysplasia

We describe the clinical course of a 65-year-old male patient who suffered from hydrocarbon-induced myelodysplasia and was successfully treated with the thrombopoietin receptor agonist (TPO-RA), romiplostim. Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis, cytopenias, and increased risk of leukemic transformation. Here, we present a clinical vignette of MDS-associated thrombocytopenia refractory to first-line drugs as well as the TPO-RA, eltrombopag. To date, romiplostim is an U.S. Food and Drug Administration (FDA)-approved drug for idiopathic thrombocytopenic purpura and thrombocytopenia secondary to liver disease. Of note, currently the FDA advises against its use in MDS based on previous long-term safety concerns. Since the therapeutic options for thrombocytopenia in MDS patients are sparse, repurposing and reassessing romiplostim in this setting have been the focus of recent studies. At the time of writing, no published double-blind randomized clinical trials have conducted a head-to-head comparison between romiplostim and eltrombopag in thrombocytopenic MDS patients. To the best of our knowledge, for a thrombocytopenic patient in the setting of MDS, this is the first documented report of refractory clinical response after a 2-year use of eltrombopag in which replacement of treatment with romiplostim resulted in sustained physiological counts of thrombocytes within four weeks.

Switching thrombopoietin receptor agonist treatments in patients with primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is a bleeding disorder that conventionally has been treated with steroids or other immunosuppressive treatments. The introduction of thrombopoietin receptor agonists (TPO-RAs), which increase platelet production, dramatically changed the treatment landscape for ITP by providing patients with well-tolerated, long-term treatment options. Two TPO-RAs, eltrombopag and romiplostim, have been approved in the United States and European Union for the treatment of ITP. Some patients do not benefit from the first TPO-RA they receive, so it is assumed that the alternate TPO-RA would have the same outcome. However, eltrombopag and romiplostim have distinct pharmacodynamic and pharmacokinetic properties and may have different tolerability and efficacy in individual patients with ITP. Published retrospective studies showed that >75% of patients who switched to the alternate TPO-RA maintained or achieved a response with the new treatment. Notably, most patients who switched due to lack of efficacy with the first TPO-RA responded to the alternate TPO-RA, which demonstrates an absence of cross-resistance between the two drugs. Therefore, switching to the alternate TPO-RA if the first TPO-RA fails to demonstrate a response should be considered before the use of a less-preferable option.

Alternate use of thrombopoietin receptor agonists in adult primary immune thrombocytopenia patients: A retrospective collaborative survey from Italian hematology centers

Sequential use of the TPO-RAs romiplostim and eltrombopag in ITP patients failing either agent was retrospectively evaluated to assess efficacy and impact of clinical characteristics on outcome. Patients were grouped into 5 categories: efficacy issues: 1^st TPO-RA failure; loss of response; non-efficacy issues: platelet fluctuations; patient's preference; adverse event development. Either one TPO-RA sequence was analyzed at 3 month and at last follow-up. 106/546 patients on TPO-RA underwent switch and 65% achieved, regained or maintained a short- term response independent of switch sequence, gender or age; lower response rates were associated with lines of previous therapy; disease duration lowers probability to respond. Clinically, patients switched for efficacy issue did not differ from those switched for non-efficacy issues. Response was achieved/regained in 57.8% of patients switched for efficacy issues, the lowest response rates were observed in non-responders to 1^st TPO-RA; 80% of patients switched for non-efficacy issues maintained a response. Platelet fluctuation resolved in 44.4%. Of the 49 patients evaluable for long-term outcome, 27 were in response on therapy; 16 discontinued the TPO-RA for reasons other than efficacy, while only 6 were non responders. We confirm the efficacy of TPO-RA switch; once achieved, response to the 2^nd TPO-RA seems durable.

Bidirectional inefficacy or intolerability of thrombopoietin receptor agonists: new data and a concise review

BACKGROUND

There is evidence that the thrombopoietin-receptor agonists romiplostim and eltrombopag may have different therapeutic values and adverse reaction profiles. Here we present new data and provide a review of all studies dealing with switching between these two drugs.

MATERIALS AND METHODS

A total of 89 patients (38 males and 51 females, aged between 14-87 years) were treated with eltrombopag and/or romiplostim between 2007 and 2016 at our institution. Eltrombopag was switched to romiplostim or vice versa in 32 patients. In addition, all published data concerning patients treated sequentially with different thrombopoietin-receptor agonists were identified via a computer-assisted search and summarised in this article.

RESULTS

Thirty-two of 89 patients treated with a thrombopoietin-receptor agonist in our institution were given both eltrombopag and romiplostim sequentially. Therapy was switched to the alternate thrombopoietin-receptor agonist 36 times, due to inefficacy (n=21), adverse reactions (n=14), and a patient's preference (n=1). In addition, data from 126 patients who have been treated with both agonists have been published by other groups. In total eltrombopag was replaced by romiplostim in 56 cases due to poor or no response or to adverse reactions. Forty-five patients responded to treatment with romiplostim, 11 patients shared cross-resistance and nine had adverse reactions to romiplostim. In contrast, romiplostim was replaced by eltrombopag in 106 cases. Seventy-eight patients responded to eltrombopag, 27 shared cross-resistance and 19 had adverse reactions to eltrombopag.

DISCUSSION

Eltrombopag and romiplostim often share bidirectional cross-resistance and/or adverse reactions. Both drugs appear to cause more adverse reactions than have been previously reported.

Efficacy and safety of eltrombopag in adult refractory immune thrombocytopenia

Background

Eltrombopag is a thrombopoietin receptor agonist with excellent treatment outcomes in immune thrombocytopenia (ITP). Here, we analyzed the dose of eltrombopag required to achieve and maintain safe platelet counts in Korean ITP patients.

Methods

Adult refractory ITP patients (<30,000 platelets/µL) were enrolled. Eltrombopag doses were increased to achieve a target platelet count (≥50,000 cells/µL). After achieving the target platelet count, the dose of concomitant ITP medications and eltrombopag was reduced to identify the lowest effective dose required to maintain the platelet count.

Results

Among 18 patients, 66.7% achieved complete response, 5.6% achieved platelet counts between 50,000 and 100,000 cells/µL, and 27.8% failed to achieve the target platelet count. The median ITP duration was significantly shorter in patients who achieved the target platelet count. The initial dose required to achieve the target platelet count was 25 mg/d. The adjusted maintenance doses were 25 mg twice per week or 25 mg/d. After discontinuation, 83.3% relapsed, and the median relapse-free survival was 15 days. Two relapsed and 1 failed patient switched to romiplostim. The response to romiplostim was similar to eltrombopag. During eltrombopag treatment, 38.9% showed hepatobiliary laboratory anomalies. Among 9 follow-up bone marrow examinations, 1 revealed fibrosis after 1 year of treatment.

Conclusion

Eltrombopag was well tolerated with excellent treatment outcomes in refractory adult ITP patients. Low-dose eltrombopag effectively maintained the target platelet count. However, some patients required longer or higher-dose treatment to maintain the target platelet count, especially in heavily pretreated or longer ITP cases.

Treatment patterns and clinical outcomes in patients with chronic immune thrombocytopenia (ITP) switched to eltrombopag or romiplostim

This observational study aimed to assess real-world treatment patterns and clinical outcomes for patients with chronic immune thrombocytopenia (ITP) currently being treated with eltrombopag or romiplostim after switching from corticosteroids, rituximab, or the alternate thrombopoietin receptor agonist (TPO-RA). The study examined the rationale for switching to TPO-RA therapy using aided responses. Dosing patterns were also analyzed before and after switching. Treatment outcomes were assessed through platelet counts at multiple time points including treatment initiation and after switching at the last office visit. A total of 280 patients were enrolled whose active therapy for ITP was replaced with either eltrombopag (n = 130) or romiplostim (n = 150). Efficacy-related issues (desired platelet count not achieved and/or lack of response to prior therapy) were the main drivers for therapy switching among all patients (54 % for eltrombopag vs. 57 % for romiplostim). Platelet counts at the last office visit showed improvement compared with counts at the initiation of either eltrombopag or romiplostim treatment. No significant differences were noted when comparing clinical outcomes between the eltrombopag and romiplostim treatment cohorts. Our results suggest that switching to the other TPO-RA may be beneficial if there is inadequate response to treatment with the initial TPO-RA.

Use of eltrombopag after romiplostim in primary immune thrombocytopenia

The thrombopoietin receptor agonists (THPO-RAs), romiplostim and eltrombopag, are effective and safe in immune thrombocytopenia (ITP). However, the value of their sequential use when no response is achieved or when adverse events occur with one THPO-RA has not been clearly established. Here we retrospectively evaluated 51 primary ITP adult patients treated with romiplostim followed by eltrombopag. The median age of our cohort was 49 (range, 18-83) years. There were 32 women and 19 men. The median duration of romiplostim use before switching to eltrombopag was 12 (interquartile range 5-21) months. The reasons for switching were: lack of efficacy (n = 25), patient preference (n = 16), platelet-count fluctuation (n = 6) and side-effects (n = 4). The response rate to eltrombopag was 80% (41/51), including 67% (n = 35) complete responses. After a median follow-up of 14 months, 31 patients maintained their response. Efficacy was maintained after switching in all patients in the patient preference, platelet-count fluctuation and side-effect groups. 33% of patients experienced one or more adverse events during treatment with eltrombopag. We consider the use of eltrombopag after romiplostim for treating ITP to be effective and safe. Response to eltrombopag was related to the cause of romiplostim discontinuation.

Initial Experience with the Use of Thrombopoetin Receptor Agonists in Patients with Refractory HIV-Associated Immune Thrombocytopenic Purpura: A Case Series

HIV-associated immune thrombocytopenic purpura (ITP) has decreased in incidence 10-fold since the advent of highly active antiretroviral therapy (HAART). For patients with detectable HIV viral loads, first-line treatment approaches involve optimizing HAART followed by standard ITP options used to treat those without HIV infection. In the general population, the thrombopoetin receptor agonists (TRAs), eltrombopag and romiplostim, are effective when used as salvage ITP therapy. In addition, eltrombopag has been used effectively in patients with thrombocytopenia secondary to hepatitis C--a virus seen commonly in HIV-infected patients, especially in those who also have a history of intravenous drug use. There are, however, few reports or studies of TRAs use in those with HIV infection. Herein, we describe 5 cases of refractory HIV-associated ITP managed with TRAs. Although platelet counts improved for all patients, 2 patients succumbed to thromboembolic complications. Our initial experience, as well as our findings from a Medline review, supports the potential utility of TRA as salvage therapy in the treatment of HIV-related ITP; however, we recommend caution in the use of these agents in those who are at highest risk of thrombosis. Additional studies are needed to determine the efficacy and, more importantly, the safety of TRAs in treatment of HIV-associated ITP.

Are adverse drug reaction patterns different between romiplostim and eltrombopag? 2009-2013 French PharmacoVigilance assessment

BACKGROUND

Romiplostim and eltrombopag, the two marketed thrombopoietin receptor agonists (TPO-RAs), have distinct binding sites and might have distinct pharmacodynamic mechanisms. The aim of this study was to compare their adverse drug reaction (ADR) patterns.

METHODS

We selected in the French PharmacoVigilance Database all ADRs associated with TPO-RAs from TPO-RA marketing until the 31st of December 2013. Medical charts were reviewed. We conducted disproportionality analyses comparing romiplostim exposure in the reports of a given ADR pattern (thrombosis, neurological, cutaneous, gastrointestinal or hematological) to romiplostim exposure in all other TPO-RA-related ADR reports. Reporting Odds Ratios (RORs) were adjusted for age and gender. We also compared the number of reports of a given ADR pattern per million daily defined doses (DDDs) dispensed in France during the study period.

RESULTS

We described 45 reports (53 ADRs) with romiplostim and 26 reports (37 ADRs) with eltrombopag. There were 19 venous thromboses. At least one other risk factor was present in 83.3% of the cases. Ten (55.6%) patients had been splenectomized previously. There were eight arterial thromboses. Another risk factor was noticed in all cases. There was no signal for an excess risk of thrombosis with romiplostim versus eltrombopag (ROR: 1.45, 95% CI [0.48-4.45]). There was a signal for a higher risk of gastrointestinal ADRs with eltrombopag (ROR: 30.28, 95% CI [3.23-383.86]) and of hematological ADRs with romiplostim (ROR: 14.36, 95% CI [1.73-119.08]). Dispensing data-adjusted comparisons led to similar results.

CONCLUSIONS

This study suggests different ADR patterns between romiplostim and eltrombopag.