The structure, function, and clinical use of the thrombopoietin receptor agonist avatrombopag

Avatrombopag in immune thrombocytopenia: A real-world study of the Spanish ITP Group (GEPTI)

Avatrombopag is the newest thrombopoietin receptor agonist (TPO-RA) approved to treat immune thrombocytopenia (ITP). Real-world evidence regarding effectiveness/safety is limited. The Spanish ITP Group (GEPTI) performed a retrospective study with patients starting avatrombopag for the first time. A total of 268 ITP patients were recruited. The median (interquartile range [IQR]) follow-up time was 47.5 (30.4-58.9) weeks. Among the 193 patients with baseline platelet counts <50 × 109/L, 174 (90.1%) of them achieved response (PC ≥50 × 109/L), and 113 (87.6%) of the 129 who persisted on avatrombopag at last visit had platelet levels above such threshold. Results were similar when only those patients switching to avatrombopag due to previous treatment failure were considered (n = 104). Patients reached response in 13 (7-21) days. Among patients with baseline levels ≥50 × 109/L, 73/75 (97.3%) reported response, which was maintained by 53 (94.6%) of the 56 who continued on avatrombopag at the end of the study. Loss-of-response was always <10%. ITP duration did not influence response. Approximately 79% (34/43) of heavily pretreated (≥4 lines) patients with baseline platelet counts <50 × 109/L switching after previous failure achieved PC ≥50 × 109/L. Previous use of eltrombopag and/or romiplostim did not influence response, regardless of whether previous TPO-RA(s) succeeded or failed. Avatrombopag allowed dose-reduction/suspension of corticosteroids in 40/50 (80.0%) patients with baseline platelet counts <50 × 109/L. Overall, 40/268 (14.9%) thrombocytosis and 12/268 (4.5%) thromboembolic events were reported. Our real-world cohort supports the use of avatrombopag to manage ITP, regardless of disease severity and treatment history.

DNA damage repair in megakaryopoiesis: molecular and clinical aspects

INTRODUCTION

Endogenous DNA damage is a significant factor in the damage of hematopoietic cells. Megakaryopoiesis is one of the pathways of hematopoiesis that ends with the production of platelets and plays the most crucial role in hemostasis. Despite the presence of efficient DNA repair mechanisms, some endogenous lesions can lead to mutagenic alterations, disruption of pathways of hematopoiesis including megakaryopoiesis and potentially result in human diseases.

AREAS COVERED

The complex regulation of DNA repair mechanisms plays a central role in maintaining genomic integrity during megakaryopoiesis and influences platelet production efficiency and quality. Moreover, anomalies in DNA repair processes are involved in several diseases associated with megakaryopoiesis, including myeloproliferative disorders and thrombocytopenia.

EXPERT OPINION

In the era of personalized medicine, diagnosing diseases related to megakaryopoiesis can only be made with a complete assessment of their molecular aspects to provide physicians with critical molecular data for patient management and to identify the subset of patients who could benefit from targeted therapy.

Efficacy and safety of avatrombopag in the treatment of thrombocytopenia after umbilical cord blood transplantation

BACKGROUND

Delayed platelet engraftment is a common complication after umbilical cord blood transplantation (UCBT), and there is no standard therapy. Avatrombopag (AVA) is a second-generation thrombopoietin (TPO) receptor agonist (TPO-RA) that has shown efficacy in immune thrombocytopenia (ITP). However, few reports have focused on its efficacy in patients diagnosed with thrombocytopenia after allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

We conducted a retrospective study to evaluate the efficacy of AVA as a first-line TPO-RA in 65 patients after UCBT; these patients were compared with 118 historical controls. Response rates, platelet counts, megakaryocyte counts in bone marrow, bleeding events, adverse events and survival rates were evaluated in this study. Platelet reconstitution differences were compared between different medication groups. Multivariable analysis was used to explore the independent beneficial factors for platelet implantation.

RESULTS

Fifty-two patients were given AVA within 30 days post-UCBT, and the treatment was continued for more than 7 days to promote platelet engraftment (AVA group); the other 13 patients were given AVA for secondary failure of platelet recovery (SFPR group). The median time to platelet engraftment was shorter in the AVA group than in the historical control group (32.5 days vs. 38.0 days, Z = 2.095, P = 0.036). Among the 52 patients in the AVA group, 46 achieved an overall response (OR) (88.5%), and the cumulative incidence of OR was 91.9%. Patients treated with AVA only had a greater 60-day cumulative incidence of platelet engraftment than patients treated with recombinant human thrombopoietin (rhTPO) only or rhTPO combined with AVA (95.2% vs. 84.5% vs. 80.6%, P <0.001). Patients suffering from SFPR had a slightly better cumulative incidence of OR (100%, P = 0.104). Patients who initiated AVA treatment within 14 days post-UCBT had a better 60-day cumulative incidence of platelet engraftment than did those who received AVA after 14 days post-UCBT (96.6% vs. 73.9%, P = 0.003).

CONCLUSION

In summary, compared with those in the historical control group, our results indicate that AVA could effectively promote platelet engraftment and recovery after UCBT, especially when used in the early period (≤14 days post-UCBT).

[Differential diagnosis and therapy of immune thrombocytopenia]

Immune thrombocytopenia is caused by autoantibodies against surface antigens on platelets. Since only about 50 % of cases will allow the identification of glycoprotein-specific antibodies, ITP remains a diagnosis of exclusion. Apart from EDTA-induced pseudo thrombocytopenia, other diseases like secondary thrombocytopenia due to medication, a large number of other disease and hereditary thrombocytopenias must be taken into account. The first-line therapy of ITP includes corticosteroids and intravenous immunoglobulins. The second line consists of thrombopoietin receptor agonists, rituximab, or splenectomy. For further lines of therapy, Fostamatinib and non-steroidal immunosuppressives are available.

Efficacy, Safety, and Population Pharmacokinetics of Eltrombopag in Children with Different Severities of Aplastic Anemia

Eltrombopag was approved as a first-line treatment for patients older than 2 years old with severe aplastic anemia (SAA). However, data on eltrombopag in children with different types of aplastic anemia (AA), especially non-severe AA (NSAA), are limited. We performed a prospective, single-arm, and observational study to investigate eltrombopag's efficacy, safety, and pharmacokinetics in children with NSAA, SAA, and very severe AA (VSAA). The efficacy and safety were assessed every 3 months. The population pharmacokinetic (PPK) model was used to depict the pharmacokinetic profile of eltrombopag. Twenty-three AA children with an average age of 7.9 (range of 3.0-14.0) years were enrolled. The response (complete and partial response) rate was 12.5%, 50.0%, and 100.0% after 3, 6, and 12 months in patients with NSAA. For patients with SAA and VSAA, these response rates were 46.7%, 61.5%, and 87.5%. Hepatotoxicity occurred in one patient. Fifty-three blood samples were used to build the PPK model. Body weight was the only covariate for apparent clearance (CL/F) and volume of distribution. The allele-T carrier of adenosine triphosphate-binding cassette transporter G2 was found to increase eltrombopag's clearance. However, when normalized by weight, the clearance between the wild-type and variant showed no statistical difference. In patients with response, children with NSAA exhibited lower area under the curve from time zero to infinity, higher CL/F, and higher weight-adjusted CL/F than those with SAA or VSAA. However, the differences were not statistically significant. The results may support further individualized treatment of eltrombopag in children with AA.

Update on the Use of Thrombopoietin-Receptor Agonists in Pediatrics

This review summarizes the rationale and current data on the use of thrombopoietin receptor agonists (TPO-RAs) for treating severe thrombocytopenia in infants, children, and adolescents. It focuses on substances that have been approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) for pediatric patients. Romiplostim and eltrombopag are already established as second-line treatment for persistent or chronic immune thrombocytopenia (ITP). As in adults, TPO-RAs are currently also evaluated in severe aplastic anemia (SAA), chemotherapy-induced thrombocytopenia (CIT), myelodysplastic syndromes (MDS), and poor engraftment after hematopoietic stem cell transplantation in pediatric and adolescent patients. Moreover, studies on the implication of TPO-RA in treating rare inherited thrombocytopenias, such as Wiskott-Aldrich syndrome (WAS), congenital amegakaryocytic thrombocytopenia (CAMT), or MYH9-associated thrombocytopenia, deserve future attention. Current developments include testing of avatrombopag and lusutrombopag that are approved for the treatment of thrombocytopenia associated with chronic liver disease (CLD) in adult patients. In pediatric and adolescent medicine, we expect in the near future a broader use of TPO-RAs as first-line treatment in primary ITP, thereby considering immunomodulatory effects that increase the rate of sustained remission off-treatment, and a selective use in rare inherited thrombocytopenias based on current clinical trials.

Avatrombopag as alternative therapy for severe aplastic anemia patients who are intolerant or unresponsive to eltrombopag

Introduction

Eltrombopag (EPAG), a thrombopoietin receptor agonist, was approved for the treatment of severe aplastic anemia (SAA) combined with immunosuppressive therapy (IST). However, EPAG contains a typical biphenyl structure, which causes liver function damage.

Methods

Twenty patients with SAA who were intolerant or refractory to EPAG were enrolled in a multicenter prospective registry of the Chinese Eastern Collaboration Group of Anemia (ChiCTR2100045895) from October 2020 to June 2023.

Results

Eight patients who were ineffective to EPAG, six with kidney impairment, and nine with abnormal liver function (two with concomitant liver and kidney impairment) were converted to avatrombopag (AVA) therapy with the median duration of AVA treatment was 6 (3-24) months. 17 cases (85%) achieved trilineage hematological response (HR): complete remission (CR) in 3 cases (15%), good partial remission (GPR) in 4 cases (20%), partial remission (PR) in 10 cases (50%), and no response (NR) in 3 cases (15%). The median time to response was 1.7 (0.5-6.9) months, with 16 cases (94%) achieving response within six months and 17 cases (100%) within 12 months. 9 cases (50%) achieved transfusion independence. AVA converted treatment was associated with higher neutrophil counts (0.8×109/L vs 2.2×109/L, p=0.0003), platelet counts (11×109/L vs 39×109/L, p=0.0008), hemoglobin count (59g/L vs 98g/L, p=0.0002), red cell count (1.06×1012/L vs 2.97×1012/L, p=0.001), and absolute reticulocyte count (31.99 ×109/L vs 67.05×109/L p=0.0004) were all significantly elevated compared with the pre-treatment level. After the conversion to AVA therapy, liver and kidney function indexes were maintained within the normal range, no AVA related grade 2 or higher adverse events occurred, and no thrombotic events occurred.

Conclusion

The conversion to AVA was an optimal choice for patients with SAA who were EPAG intolerant or refractory.

Clinical trial registration

http://www.chictr.org.cn/showproj.html?proj=125480, identifier ChiCTR2100045895.

Recombinant Human Thrombopoietin Promotes Platelet Engraftment in Severe Aplastic Anemia Patients Following Treatment With Haploid Hematopoietic Stem Cell Transplantation using Modified Post-Transplantation Cyclophosphamide

BACKGROUND

Recombinant human TPO (rhTPO) promotes platelet engraftment in patients after allogeneic HSCT (allo-HSCT). However, the effects of rhTPO on platelet recovery after Haplo-HSCT in patients with severe aplastic anemia (SAA) have not been intensively studied.

OBJECTIVE

We aimed to evaluate the efficacy of rhTPO on platelet engraftment in patients with SAA who were treated with Haplo-HSCT using post-transplantation cyclophosphamide (PTCy).

STUDY DESIGN

SAA patients who received Haplo-HSCT plus PTCy regimen were divided into the rhTPO group (with subcutaneous injection of rhTPO, n = 28) and Control group (no rhTPO administration, n = 27). The engraftment of platelet/neutrophil, platelet infusion amount, and transplant-related complications between the 2 groups were compared.

RESULTS

All 55 patients showed successful hematopoietic reconstitution. The median time of platelet engraftment was 11 (9 to 29) days in the rhTPO group and 14 (9 to 28) days in the Control group (P = .003). The rhTPO group had a significantly reduced amount of infused platelets compared to the Control group (2 (1 to 11.5) versus 3 (1 to 14) therapeutic doses; P = .004). There was no significant difference between the 2 groups regarding median time of neutrophil engraftment, incidence of acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD), incidence of cytomegalovirus or Epstein-Barr virus reactivation, 3-yr overall survival rate, and failure-free-survival rate. No obvious adverse reactions were observed in the rhTPO group.

CONCLUSION

rhTPO promoted platelet engraftment, reduced the amount of transfused platelets, and demonstrated good safety profiles without evidence of adverse reactions in patients with SAA who received Haplo-HSCT using PTCy regimen.

Efficacy and safety of avatrombopag in Chinese children with persistent and chronic primary immune thrombocytopenia: A multicentre observational retrospective study in China

Avatrombopag (AVA) is a novel thrombopoietin receptor agonist (TPO-RA) that has been recently approved as a second-line therapy for immune thrombocytopenia (ITP) in adults; however, its safety and efficacy data in children are lacking. Here, we demonstrated the efficacy and safety of AVA as second-line therapy in children with ITP. A multicentre, retrospective, observational study was conducted in children with persistent or chronic ITP who did not respond to or relapsed from previous treatment and were treated with AVA for at least 12 weeks between August 2020 and December 2022. The outcomes were the responses (defined as achieving a platelet count ≥30 × 109/L, twofold increase in platelet count from baseline and absence of bleeding), including rapid response within 4 weeks, sustained response at weeks 12 and 24, bleeding control and adverse events (AEs). Thirty-four (18 males) patients with a mean age of 6.3 (range: 1.9-15.3) years were enrolled. The median number of previous treatment types was four (range: 1-6), and 41.2% patients switched from other TPO-RAs. Within 4 weeks, overall response (OR) was achieved in 79.4% patients and complete response (CR, defined as a platelet count ≥100 × 109/L and the absence of bleeding) in 67.7% patients with a median response time of 7 (range: 1-27) days. At 12 weeks, OR was achieved in 88.2%, CR in 76.5% and sustained response in 44% of patients. At 24 weeks, 22/34 (64.7%) patients who achieved a response and were followed up for 24 weeks were evaluated; 12/22 (54.55%) achieved a sustained response. During AVA therapy, median platelet counts increased by week 1 and were maintained throughout the treatment period. The proportion of patients with grade 1-3 bleeding decreased from 52.95% at baseline to 2.94% at 12 weeks, while concomitant ITP medications decreased from 36.47% at baseline to 8.82% at 12 weeks, with only 9 (26.47%) patients receiving rescue therapy 23 times within 12 weeks. There were 61.8% patients with 59 AEs: 29.8% with Common Terminology Criteria for Adverse Events grade 1 and the rest with grade 2. These findings show that AVA could achieve a rapid and sustained response in children with persistent or chronic ITP as a second-line treatment, with good clinical bleeding control and reduction of concomitant ITP therapy, without significant AEs.

Lusutrombopag as a Repurposing Drug in Combination with Aminoglycosides against Vancomycin-Resistant Enterococcus

Due to the widespread abuse of antibiotics, drug resistance in Enterococcus has been increasing. However, the speed of antibiotic discovery cannot keep pace with the acquisition of bacterial resistance. Thus, drug repurposing is a proposed strategy to solve the crises. Lusutrombopag (LP) has been approved as a thrombopoietin receptor agonist by the Food and Drug Administration. This study demonstrated that LP exhibited significant antimicrobial activities against vancomycin-resistant Enterococcus in vitro with rare resistance occurrence. Further, LP combined with tobramycin exhibited synergistic antimicrobial effects in vitro and in vivo against Enterococcus. No in vitro or in vivo detectable toxicity was observed when using LP. Mechanism studies indicated that the disrupted proton motive force may account for LP's antimicrobial activity. In summary, these results demonstrate that LP has the previously undocumented potential to serve as an antibacterial agent against refractory infections caused by Enterococcus.

Avatrombopag for the salvage treatment of platelet transfusion refractoriness

Background

Platelet transfusion refractoriness (PTR) is a life-threatening and intractable condition in hematological patients. Thrombopoietin receptor agonists such as avatrombopag promote platelet production and modulate immune intolerance. However, its application in PTR has not been extensively studied.

Objectives

We aimed to compare the platelet response (PR) as well as bleeding events and mortality rate between the best available therapies (BATs) and avatrombopag (Ava) treatments in refractory PTR patients.

Design

A total of 71 refractory PTR patients were enrolled at Nanfang Hospital. Intravenous immunoglobulin, steroids, and human leucocyte antigen-matched platelet transfusions were administered to 30 patients in the BATs group. The Ava group included 41 patients.

Methods

Data of refractory PTR patients were retrospectively collected. The primary endpoint was PR (defined as an increase of platelet count to ⩾50 × 109/L without platelet transfusion support for 7 consecutive days). Secondary endpoints included platelet-transfusion independence rate, cumulative platelet transfusion units, World Health Organization bleeding grades, adverse events, overall survival (OS), and bleeding event-free survival (EFS).

Results

There were 75.6% and 13.3% refractory PTR patients who reached PR within 3 months in Ava and BATs groups. The median platelet counts were significantly higher in Ava group from day 7. Platelet-transfusion independence rate in Ava was higher than BATs group. The median cumulative platelet transfusion unit in Ava was lower than that of BATs group. The OS and bleeding events-free EFS rate of Ava group improved within 3 months as compared to BATs group. Cox proportional hazards regression analysis revealed that Ava therapy was a protective factor for the OS and EFS. No primary disease progression or termination of avatrombopag was observed due to intolerability.

Conclusion

Our study suggests that avatrombopag is an effective and safe treatment option for refractory PTR patients.

Synthetic Approaches to Piperazine-Containing Drugs Approved by FDA in the Period of 2011-2023

The piperazine moiety is often found in drugs or in bioactive molecules. This widespread presence is due to different possible roles depending on the position in the molecule and on the therapeutic class, but it also depends on the chemical reactivity of piperazine-based synthons, which facilitate its insertion into the molecule. In this paper, we take into consideration the piperazine-containing drugs approved by the Food and Drug Administration between January 2011 and June 2023, and the synthetic methodologies used to prepare the compounds in the discovery and process chemistry are reviewed.

Avatrombopag, a promising novel thrombopoietin receptor agonist for refractory/relapsed/intolerant non-severe aplastic anemia: a phase 2 single-arm clinical trial

INTRODUCTION

The therapeutic options for thrombocytopenia in non-severe aplastic anaemia (NSAA) are limited. Avatrombopag (AVA) is prescribed for thrombocytopenic diseases but not for NSAA.

METHODS

Herein, we conducted a phase 2, non-randomized, single-arm trial to explore the efficacy and safety of AVA in refractory/relapsed/intolerant NSAA. AVA dose was initiated at 20 mg/d and titrated to a maximum of 60 mg/d. The primary endpoint was the haematological response at 3 months.

RESULTS

Twenty-five patients were analyzed. The overall response rate (ORR) at 3 months was 56% (14/25), with 12% (3/25) achieving a complete response (CR). At a median follow-up of 7 (3-10) months, the OR and CR rates were 52% and 20%, respectively. Responders had a shorter duration of diagnosis of AVA administration than non-responders (10 (6-80) vs 37 (6-480) months, p = 0.027) and belonged to the relapsed/intolerant NSAA type (71% vs 27%, p = 0.047); 44% (8/18) patients previously treated with eltrombopag before enrollment responded at 3 months, with an average prior eltrombopag dose of median 72.5 (50-100) mg/d and an average AVA dose for a response of median 43.5 (20-60) mg/d. 3-month ORR had no significant correlation with eltrombopag exposure (p = 0.09), prior eltrombopag length (R²=0.11), or cumulative eltrombopag dose (R²=0.30). Only one patient relapsed after stopping AVA for 1 month. No serious AVA-related side effects or clone evolution were detected.

CONCLUSION

AVA is effective and well-tolerated in NSAA patients who are refractory, relapsed, or intolerant to CsA/tacrolimus ± eltrombopag. Earlier treatment and relapsed/intolerant AA may show a better short-term response rate. More studies are needed to define the optimal dose and the long-term efficacy (NCT04728789).

Structure of the thrombopoietin-MPL receptor complex is a blueprint for biasing hematopoiesis

Thrombopoietin (THPO or TPO) is an essential cytokine for hematopoietic stem cell (HSC) maintenance and megakaryocyte differentiation. Here, we report the 3.4 Å resolution cryoelectron microscopy structure of the extracellular TPO-TPO receptor (TpoR or MPL) signaling complex, revealing the basis for homodimeric MPL activation and providing a structural rationalization for genetic loss-of-function thrombocytopenia mutations. The structure guided the engineering of TPO variants (TPOmod) with a spectrum of signaling activities, from neutral antagonists to partial- and super-agonists. Partial agonist TPOmod decoupled JAK/STAT from ERK/AKT/CREB activation, driving a bias for megakaryopoiesis and platelet production without causing significant HSC expansion in mice and showing superior maintenance of human HSCs in vitro. These data demonstrate the functional uncoupling of the two primary roles of TPO, highlighting the potential utility of TPOmod in hematology research and clinical HSC transplantation.

Avatrombopag for adult chronic primary immune thrombocytopenia: a randomized phase 3 trial in China

Background

Immune thrombocytopenia (ITP) is an autoimmune disorder with decreased platelet counts and increased bleeding risk.

Objectives

To evaluate the efficacy and safety of avatrombopag, a second-generation oral thrombopoietin receptor agonist, for the treatment of Chinese patients with chronic primary ITP.

Methods

This multicenter, randomized, double-blind, placebo-controlled phase 3 study (CTR20210431) consisted of a 6-week double-blind core treatment phase followed by a 20-week, open-label extension phase. Chinese adults with chronic primary ITP for at least 12 months and a platelet count <30 × 109/L were randomized (2:1) to receive avatrombopag (initial dose of 20 mg/day) or matched placebo. The primary endpoint was the proportion of subjects with a platelet count ≥50 × 109/L at week 6 of the core treatment phase in absence of rescue therapy.

Results

In total, 74 patients were randomized (avatrombopag: N = 48; placebo: N = 26) between March 5, 2021, and August 6, 2021; all of whom entered the extension phase (72 received avatrombopag up to 26 weeks). At week 6 of the core study, the platelet response (≥50 x 109/L) rate was significantly higher in the avatrombopag group (77.1%; 95% CI, 62.7, 88.0) vs placebo (7.7%; 95% CI, 1.0, 25.1); the treatment difference was 69.4% (95% CI, 56.2, 86.3; P < .0001). During the 6-week core study, treatment-emergent adverse events were reported in 41 (85.4%) and 20 (76.9%) patients in the avatrombopag and placebo groups, respectively. The most common avatrombopag-related treatment-emergent adverse events were upper respiratory tract infection (14/48 [29.2%]), increased platelet count (13/48 [27.1%]) and headache (7/48 [14.6%]).

Conclusion

Avatrombopag was efficacious and generally well tolerated in Chinese patients with chronic primary ITP, with comparable efficacy and safety to previous reports in Western patients.

Avatrombopag increased platelet count in a patient with chronic immune thrombocytopenia refractory to multiple lines of treatment

We present a case of a 30-year-old man suffering from chronic refractory immune thrombocytopenia (ITP) from early childhood. The patient was treated with all the therapeutic methods available in Poland, without platelet response: corticosteroids, intravenous immunoglobulins, splenectomy, cyclophosphamide, vinblastine, azathioprine, mycophenolate mofetil, rituximab, ciclosporin A, romiplostim, and eltrombopag. He continued to function persistently with deep thrombocytopenia, symptoms of hemorrhagic diathesis, and one episode of spontaneous subarachnoid bleeding. In April 2022, at the age of 29, the patient received avatrombopag. Within 4 weeks of starting avatrombopag 20 mg daily for 2 weeks and then 40 mg daily, he reached a platelet (PLT) count of 67 x 10 9 /l. In the next month, platelets fell below 30 x 10 9 /l, but subsequently the count increased to 47 x 10 9 /l, then to 52 x 10 9 /l, and remained stable. The symptoms of cutaneous hemorrhage diathesis have resolved completely since avatrombopag was introduced and did not reappear despite the decrease in PLT count.

Use of thrombopoietin receptor agonists in adults with immune thrombocytopenia: a systematic review and Central European expert consensus

There are currently three thrombopoietin receptor agonists (TPO-RAs) approved in Europe for treating patients with immune thrombocytopenia (ITP): romiplostim (Nplate®), eltrombopag (Revolade®), and avatrombopag (Doptelet®). However, comparative clinical data between these TPO-RAs are limited. Therefore, the purpose of this study was to perform a literature review and seek expert opinion on the relevance and strength of the evidence concerning the use of TPO-RAs in adults with ITP. A systematic search was conducted in PubMed and Embase within the last 10 years and until June 20, 2022. A total of 478 unique articles were retrieved and reviewed for relevance. The expert consensus panel comprised ITP senior hematologists from eight countries across Central Europe. The modified Delphi method, consisting of two survey rounds, a teleconference and email correspondence, was used to reach consensus. Forty articles met the relevancy criteria and are included as supporting evidence, including five meta-analyses analyzing all three European-licensed TPO-RAs and comprising a total of 31 unique randomized controlled trials (RCTs). Consensus was reached on seven statements for the second-line use of TPO-RAs in the management of adult ITP patients. In addition, the expert panel discussed TPO-RA treatment in chronic ITP patients with mild/moderate COVID-19 and ITP patients in the first-line setting but failed to reach consensus. This work will facilitate informed decision-making for healthcare providers treating adult ITP patients with TPO-RAs. However, further studies are needed on the use of TPO-RAs in the first-line setting and specific patient populations.

Application and investigation of thrombopoiesis-stimulating agents in the treatment of thrombocytopenia

Platelets, derived from a certain subpopulation of megakaryocytes, are closely related to hemostasis, coagulation, metastasis, inflammation, and cancer progression. Thrombopoiesis is a dynamic process regulated by various signaling pathways in which thrombopoietin (THPO)-MPL is dominant. Thrombopoiesis-stimulating agents could promote platelet production, showing therapeutic effects in different kinds of thrombocytopenia. Some thrombopoiesis-stimulating agents are currently used in clinical practices to treat thrombocytopenia. The others are not in clinical investigations to deal with thrombocytopenia but have potential in thrombopoiesis. Their potential values in thrombocytopenia treatment should be highly regarded. Novel drug screening models and drug repurposing research have found many new agents and yielded promising outcomes in preclinical or clinical studies. This review will briefly introduce thrombopoiesis-stimulating agents currently or potentially valuable in thrombocytopenia treatment and summarize the possible mechanisms and therapeutic effects, which may enrich the pharmacological armamentarium for the medical treatment of thrombocytopenia.

Avatrombopag for the treatment of thrombocytopenia in children's patients following allogeneic hematopoietic stem-cell transplantation: A pilot study

Thrombocytopenia following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a common and life-threatening complication. Thus, new prevention and treatment strategies for post-HSCT thrombocytopenia are urgently required. In recent studies, thrombopoietin receptor agonists (TPO-RA) for treating post-HSCT thrombocytopenia indicated efficiency and safety. The improved effect of post-HSCT thrombocytopenia in adults was found in the administration of avatrombopag which was a new TPO-RA. However, there was no relevant study in the children's cohort. Herein, we retrospectively analyzed the effect of avatrombopag in post-HSCT thrombocytopenia in children. As a result, the overall response rate (ORR) and complete response rate (CRR) were 91% and 78%, respectively. Furthermore, both cumulative ORR and CRR were significantly lower in the poor graft function (PGF)/secondary failure of platelet recovery (SFPR) group compared to the engraftment-promotion group (86.7% vs. 100%, p = 0.002 and 65.0% vs. 100%, p < 0.001, respectively). Achieving OR required a median of 16 days in the PGF/SFPR group while 7 days in the engraftment-promotion group (p = 0.003). Grade III-IV acute graft vs. host disease and inadequate megakaryocytes were identified as risk factors of CRR only in univariate analysis (p = 0.03 and p = 0.01, respectively). No severe adverse events were documented. Conclusively, avatrombopag is an alternatively efficient and safe agent for treating post-HSCT thrombocytopenia in children.

Effectiveness and Safety of Avatrombopag in Liver Cancer Patients with Severe Thrombocytopenia: Real-World Data and Challenges

Background

Avatrombopag has been approved in patients who have severe thrombocytopenia (<50 × 10⁹/L) and chronic liver disease (CLD) while receiving invasive procedures. The real-world application and effectiveness of avatrombopag in the subgroup patients with liver cancer remain unknown.

Methods

Liver cancer patients (including primary liver cancer and colorectal cancer liver metastasis) who had severe thrombocytopenia and received avatrombopag were retrospectively enrolled. Avatrombopag dose, peak and absolute platelet count increase, combination treatment with other thrombopoietic agents, responder (peak count ≥50 × 10⁹/L with absolute increase ≥20 × 10⁹/L) rate, and anticancer treatment effect were analyzed. Thrombosis and bleeding events were assessed.

Results

In total, 93 patients were enrolled, with 72 and 21 in the CLD and non-CLD groups, respectively. Patients with CLD had hepatitis B or C, larger spleen volume, and a higher cirrhosis degree. Baseline platelet counts were similar between two groups (median, 37.0 × 10⁹/L vs. 39.0 × 10⁹/L; P=0.594), while patients without CLD had higher peak platelet (median, 134.0 × 10⁹/L vs. 74.0 × 10⁹/L; P=0.015) and absolute increase (median, 101.0 × 10⁹/L vs. 41.0 × 10⁹/L; P=0.020) after avatrombopag treatment. The responder rate was higher in patients without CLD (100% vs. 76.4%; P=0.010). Combined avatrombopag with other thrombopoietic agents significantly increased platelet count; repeated use of avatrombopag produced similar effects with that of initial treatment. Concerning anticancer treatment effect, patients who responded to avatrombopag had a higher disease control rate. No thrombosis or hemorrhagic events were observed, even in patients with portal vein tumor thrombosis.

Conclusion

Avatrombopag was safe and effective and ensured successful implementation of anticancer treatment in liver cancer patients with severe thrombocytopenia, accompanied with or without CLD.

Clinical efficacy of avatrombopag and recombinant human thrombopoietin in the treatment of chronic liver disease-associated severe thrombocytopenia: A real-world study

Purpose: To investigate the clinical efficacy of avatrombopag, an oral thrombopoietin receptor agonist, versus subcutaneous recombinant human thrombopoietin (rh-TPO) in the treatment of severe thrombocytopenia (TCP) associated with chronic liver disease (CLD).

Methods: Clinical data of 250 patients with severe TCP associated with CLD were collected in a single hospital from January 2019 to January 2022. The main parameters measured were the therapeutic response rate, changes in platelets (PLTs), and adverse events. Propensity score matching (PSM) was used to avoid possible selection bias.

Results: After PSM, a total of 154 patients were enrolled in the study: 77 in the avatrombopag group and 77 in the rh-TPO group. There was no statistically significant difference between the two groups in the effect of increasing the PLT count (Waldχ2 = 1.659, p = 0.198; Waldχ2 = 0.220, p = 0.639). In addition, no interaction between time and different medications was found (Waldχ2 = 0.540, p = 0.910; Waldχ2 = 1.273, p = 0.736). Interestingly, in the subgroup analysis, both before and after PSM, avatrombopag showed better clinical efficacy than rh-TPO in the treatment of TCP associated with CLD in Child‒Pugh Class A (88.89% vs. 63.41%, p =0.003; 81.33% vs. 61.76%, p = 0.043). Fewer patients reported dizziness in the avatrombopag group than in the rh-TPO group both before and after PSM (7.8% vs. 25.0%; 7.8% vs. 24.7%, p &lt; 0.05).

Conclusion: Both before and after PSM, avatrombopag showed better clinical efficacy than rh-TPO in the treatment of TCP associated with CLD in Child‒Pugh Class A and showed a lower incidence of dizziness in all patients.

An updated evaluation of avatrombopag for the treatment of chronic immune thrombocytopenia

INTRODUCTION

Multiple agents are available for the management of chronic immune thrombocytopenia (ITP), including thrombopoietin-receptor agonists (TPO-RAs), rituximab, and fostamatinib. Although TPO-RAs are often selected as treatments for chronic ITP, when choosing between the TPO-RAs, clinicians must balance safety profile, dosing restrictions, and method of administration incorporating patient preference.

AREAS COVERED

We provide an overview of the thrombopoietin receptor agonists with a particular focus on avatrombopag, the newest agent in this class. In phase II and III clinical trials, avatrombopag was shown to offer durable improvement in platelet counts. We also include recent real-world evidence describing avatrombopag effectiveness in patients with poor response to prior treatments (including other TPO-RAs).

EXPERT OPINION

Compared with other TPO-RAs used to treat ITP, avatrombopag offers practical oral dosing with a single pill strength, does not require long-term dietary restrictions, and has no warning for hepatotoxicity. It is frequently effective after use of other TPO-RAs in ITP. The primary downside with avatrombopag use at present is the lack of longer-term safety data in ITP that presently exists for romiplostim and eltrombopag.

Avatrombopag improves thrombocytopenia in MYH9-related disorder following eltrombopag treatment failure

MYH9-related disorder (MYH9-RD) is autosomal dominant thrombocytopenia caused by mutations in the MYH9 gene, which codes for the non-muscle myosin-IIA heavy chain. We present a case of a 24-year-old Chinese man with MYH9-RD who was initially misdiagnosed with immune thrombocytopenia. Whole-exome sequencing and Sanger sequencing revealed a novel missense mutation in the MYH9 gene at the position of c.4550 G > T (p.G1517V) in exon 32. The same phenotype was observed in the proband, his mother, and his brother, in addition to macrothrombocytopenia and Dohle-like bodies in neutrophil granulocytes without non-hematologic manifestations. Following failed treatment with eltrombopag, avatrombopag, which was not mentioned before in the MYH9-RD treatment, was administered to the patient, and thrombocytopenia improved. In this case report, we present a novel pathogenic mutation and show the potential of avatrombopag for temporarily increasing the platelet count in patients with MYH9-RD.

Avatrombopag for the Treatment of Adult Patients with Chronic Immune Thrombocytopenia (cITP): Focus on Patient Selection and Perspectives

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by a reduced number of circulating platelets due to immune-mediated destruction and decreased platelet production in the bone marrow. Thrombopoietin receptor agonists (TPO-RAs) are highly effective and widely used in the treatment of patients with steroid treatment failure or dependency. Avatrombopag represents a new supplement to the TPO-RAs family. It was originally approved for the treatment of thrombocytopenia in patients with chronic liver disease who are scheduled to undergo an invasive procedure. However, labeled indications for avatrombopag have been relatively recently expanded to include treatment of chronic ITP in adults with insufficient response to the previous treatments. In this article, we provide an overview of pharmacodynamics and pharmacokinetics of avatrombopag as well as results of the clinical trials related to safety and efficacy of avatrombopag with a perspective on current clinical use. Available data so far suggests that avatrombopag can be effectively used in ITP patients and has a favorable safety profile. Though further studies are needed to affirm the efficacy and safety, avatrombopag has the potential to become a TPO agonist of choice for many patients with ITP.