Long-term administration of pegylated recombinant human megakaryocyte growth and development factor dramatically improved cytopenias in a patient with myelodysplastic syndrome

Current Advance in Thrombopoietin Receptor Agonists in the Management of Thrombocytopenia Associated With Chronic Liver Disease: Focus on Avatrombopag

Chronic liver disease (CLD) is a condition that progresses over time toward advanced disease state which is known as liver cirrhosis. Liver cirrhosis leads to dangerous health problems among people living across the world. One such problem that observed in about 75% of cirrhotic patients is thrombocytopenia; which in turn associated with poor prognosis and recovery from CLD. Beyond these, thrombocytopenia in cirrhotic patients led to impairment of coagulation cascade and significantly influenced the utilization of effective mechanism in the management of CLD. By nature, treatment of CLD involves invasive diagnostic and treatment procedures; therefore, in the presence of thrombocytopenia implementing these methods put the lives of patients in a critical health problem due to increased risk of bleeding and mortality. Because of these reasons, prophylactic transfusion of platelets is considered to be one of the most effective options that reduce the risk of bleeding in patients with CLD that required to undergo an invasive procedure. Although platelet transfusion presented with significant advantages in facilitating the invasive procedure in patients with CLD, refractoriness with repeated use and various problems associated with its transfusion limit the continuous utilization of this important option. With these challenges and current advance in the knowledge of thrombopoiesis, the development of relatively safe and alternative drugs that enhance the production of platelets by interacting with thrombopoietin receptor agonists provides a promising option to platelet transfusion. The discovery and approval of romiplostim and eltrombopag in August 2008 and November 2008, respectively, for the treatment of chronic immune thrombocytopenia paved a way and followed by the Food and Drug Administration (FDA) approval of 2 potentially advantageous drugs, lusutrombopag, and avatrombopag, in 2018 for the treatment of thrombocytopenia in patients with CLD that required to undergo elective surgery. Therefore, this review aims to assess pathogenesis of thrombocytopenia and its challenges in the management of liver-related issues and, more importantly, gives emphasis to address the potential use of avatrombopag in the treatment of thrombocytopenia underlying CLD, its pharmacokinetics and pharmacodynamics, as well as its toxicological profiles by presenting the most commonly reported adverse events in various trials.

Milestones in understanding platelet production: a historical overview

The discovery of thrombopoietin (TPO, also termed THPO) in 1994 was a major achievement in understanding the regulation of platelet production. In prior decades, physiological studies had demonstrated that platelets were produced from bone marrow megakaryocytes and that the megakaryocytes responded to thrombocytopenia by increasing their number, size and DNA ploidy. In 1958, it was proposed that a 'thrombopoietin' must exist that regulated this interaction between the circulating platelet mass and the bone marrow megakaryocytes. After over three decades of effort, TPO was finally purified by five independent laboratories. TPO stimulated megakaryocyte colony-forming cell growth and increased the number, size and ploidy of megakaryocytes. When the genes for TPO or TPO receptor were eliminated in mice, megakaryocytes grew and platelets were made, but at 15% of their normal number. A first generation of recombinant human (rh) TPO molecules [rhTPO and pegylated recombinant human megakaryocyte growth and development factor (PEG-rhMGDF)] rapidly entered clinical trials in 1995 and increased platelet counts in humans undergoing non-myeloablative chemotherapy but not in those undergoing stem cell transplantation. Antibodies developed against PEG-rhMGDF and development of these recombinant thrombopoietins ended. A second generation of TPO receptor agonists (romiplostim and eltrombopag) was then developed. Neither of these TPO receptor agonists demonstrated any significant untoward effects and both are now licensed in many countries for the treatment of immune thrombocytopenia. This review describes the significant experiments that have surrounded the discovery of TPO and its clinical development.

Recombinant human thrombopoietin alleviates infection-associated thrombocytopenia: a retrospective study in senile patients

OBJECTIVE

To examine the efficacy and adverse events of recombinant human thrombopoietin (rhTPO) in the treatment of infection-associated thrombocytopenia in senile patients.

METHODS

The current study is a retrospective analysis of the patients receiving rhTPO for infection-associated thrombocytopenia in our hospital.

RESULTS

Forty-nine cases were included in the analysis as rhTPO group. The absolute platelet count after treatment, increase in platelet count, and the overall response rate were considerably higher in the rhTPO group than that in the control group. Improvement in bleeding score was higher in the rhTPO treatment group than that in the control group (2.1 ± 5.4 vs 0.4 ± 1.7). Bleeding event was stopped in 68.2% of the patients after rhTPO treatment and in 35% of the patients in the control group (P = .032). A stratified analysis indicated that the therapeutic efficacy is much better in patients without organ failure.

CONCLUSION

Recombinant human TPO is effective in alleviating infection-associated thrombocytopenia and hemorrhage in senile patients, particularly if given prior to the emergence of organ failure.

Revisiting use of growth factors in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematologic neoplasms characterized by morphologic dysplasia, aberrant hematopoiesis and peripheral blood refractory cytopenias. MDS is recognized to be associated with an increased risk of symptomatic anemia, infectious complications and bleeding diathesis, as well as a risk of progression to acute myeloid leukemia, particularly in patients with a high IPSS score. The advent of use of hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) and recombinant erythropoietin (EPO) has improved symptoms in MDS patients in addition to some data that suggest there might be an improvement in survival. G-CSF is an effective therapeutic option in MDS patients, and it should be considered for the management of refractory symptomatic cytopenias. G-CSF and EPO in combination can improve outcomes in appropriate MDS patients such as those with lower-risk MDS and refractory anemia with ring sideroblasts (RARS) . This article reviews use of growth factors for lower-risk MDS patients, and examines the data for G-CSF, EPO and thrombopietic growth factors (TPO) that are available or being developed as therapeutic modalities for this challenging disease.

Development of thrombopoietin receptor agonists for clinical use

Thrombopoietin (TPO) is an essential hematopoietic cytokine for megakaryopoiesis. In 2002, we demonstrated that pegylated-recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) increased platelet counts in patients with chronic immune thrombocytopenic purpura (ITP) in a Phase I/II clinical trial. After the cessation of clinical trials of PEG-rHuMGDF because of severe thrombocytopenia or pancytopenia due to the development of the neutralizing antibody cross-reacting with endogenous TPO, second generation non-immunogenic TPO receptor agonists have been developed. A small molecule eltrombopag and Romiplostim were approved for clinical use by FDA in 2008 to treat patients with chronic ITP who are refractory to the prior therapy. Although the efficacy of both TPO receptor agonists is convincing for the refractory ITP, further investigation is necessary to assess the potential long-term side effects and clinical applications of these therapies for other thrombocytopenic conditions.

Hematopoietic Growth Factors in the Treatment of Acquired Bone Marrow Failure States

In severe aplastic anemia (SAA), the use of hematopoietic growth factors (HGFs) to support blood counts is of limited value, as predicted by in vitro studies and measurement of endogenous serum levels of hematopoietic growth factors (HGF), which are markedly elevated. Benefit is usually only seen in those with less severe disease who are unlikely to require HGFs in practice. HGFs administered alone play no role in the treatment of SAA. The main indication for using HGFs, most often granulocyte colony-stimulating factor (G-CSF), in SAA has been to determine whether they increase the response rate to immunosuppressive therapy (IST) and improve survival. While earlier neutrophil recovery occurs when G-CSF is administered with IST, studies to date show no significant advantage in hematologic response or overall survival. Conflicting results have been reported concerning whether G-CSF increases the known risk of myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) after IST; follow-up of at least 10 years is required, lacking in many clinical studies reported to date. In MDS, HGFs have been used to counteract the intramedullary apoptosis, which leads to ineffective hematopoiesis. In several uncontrolled and controlled studies, especially in low-risk MDS, high-dose erythropoietin (EPO) or its glycosylated derivative darbepoetin (DPO), alone or in combination with G-CSF, increased hemoglobin levels and diminished the need for red blood cell transfusions, in selected patients with prior transfusion frequency of less than 2 units per month and EPO levels below 500 IU/L. Quality-of-life measures were claimed to have improved, but the cost-effectiveness of this approach is debated, as is safety with regard to the risk of progression. G-CSF is used in supportive care of MDS to improve neutropenia during infectious complications, but to date there is no compelling evidence for a survival benefit or alteration of the course of the disease through the use of HGFs in MDS.

Long-term Efficacy of Pegylated Recombinant Human Megakaryocyte Growth and Development Factor in Therapy of Aplastic Anemia

Pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) potently stimulates platelet production in humans, mitigates thrombocytopenia associated with nonmyeloablative chemotherapy, and reduces the need for platelet transfusions. Its long-term effect in patients, however, is not well understood. We report a patient with aplastic anaemia who received 3 cycles of PEG-rHuMGDF 3 times a week for up to 2 years. Platelet counts slightly increased 1 week after the initiation of PEG-rHuMGDF therapy, bleeding episodes decreased, and there was no need for platelet transfusion. Administration of PEG-rHuMGDF increased not only platelet numbers but also reticulocyte counts, and reduced the need for erythrocyte transfusions as well. There were no significant adverse events, and no neutralizing antibodies were detected in the patient.