Romiplostim in chronic immune thrombocytopenic purpura

Investigation of the mechanism of action of Shengxuexiaoban Capsules against primary immune thrombocytopenia using network pharmacology and experimental validation

BACKGROUND

Shengxuexiaoban Capsules (SC) is a classical prescription in traditional Chinese medicine (TCM) and has been clinically adopted in the treatment of primary immune thrombocytopenia (ITP) in China. However, the underlying mechanisms of the actions of SC on ITP remain clear.

METHODS

A network pharmacology approach was adopted to investigate the underlying molecular mechanism of SC in treating ITP, and the effects of SC on the proliferation, differentiation, and apoptosis of megakaryocyte (MK) and on the ITP animal model were investigated.

RESULTS

Network pharmacology analysis found 128 active compounds and 268 targets of these compounds in SC, as well as 221 ITP-related targets. The topological analysis found a central network containing 82 genes, which were significantly associated with the regulation of transcription, cell proliferation, apoptosis processes, the PI3K-AKT signaling pathway, the MAPK signaling pathway, and the ERK1 and ERK2 cascades. It showed that SC increased the proliferation and differentiation of MK, but had no significant impact on MK apoptosis in vivo. The addition of SC increased the gene expression of several potential targets, including STAT3, KDR, CASP3, and TGFB1. In addition, SC administration elevated the protein expression of p-AKT and inhibit the protein expression of p-ERK, but has no impact on the protein expression of p-P38. Moreover, SC could improve haemogram parameters, coagulation indicators, and the proliferation and differentiation of MK in the ITP animal model.

CONCLUSIONS

The present study systematically elucidated the underlying mechanisms of SC against ITP and provided an efficient strategy to discover the pharmacological mechanism of TCM. It may strengthen the understanding of SC and facilitate more application of this formula in the treatment of ITP.

Extremophilic proteases as novel and efficient tools in short peptide synthesis

The objective of this review is to outline the crucial role that peptides play in various sectors, including medicine. Different ways of producing these compounds are discussed with an emphasis on the benefits offered by industrial enzyme biotechnology. This paper describes mechanisms of peptide bond formation using a range of proteases with different active site structures. Importantly, these enzymes may be further improved chemically and/or genetically to make them better suited for their various applications and process conditions. The focus is on extremophilic proteases, whose potential does not seem to have been fully appreciated to date. The structure of these proteins is somewhat different from that of the common commercially available enzymes, making them effective at high salinity and high or low temperatures, which are often favorable to peptide synthesis. Examples of such enzymes include halophilic, thermophilic, and psychrophilic proteases; this paper also mentions some promising catalytic proteins which require further study in this respect.

Expression, purification and biological activity assessment of romiplostim biosimilar peptibody

Background

Romiplostim is a peptibody analogue of thrombopoietin (TPO) which regulates platelet production. This molecule consists of two main parts: Peptide sequences which like wild type TPO, mimics stimulation of TPO receptor and IgG1Fc, (Peptide + Antibody = Peptibody). This drug is used in treatment of chronic Immune Thrombocytopenic Purpura (ITP).

Methods

In this project E. coli bacteria were transformed by a construct harboring peptibody fusion gene. This construct consisted of two repeated peptide sequences which have fused to Carboxyl group of IgG1Fc. Designed construct in E. coli host resulted in protein expression in cytoplasm as inclusion body. The inclusion bodies were separated, washed and after denaturation and solubilization, in the last stage the desired peptibodies were refolded and purified. The resulting peptibodies were characterized by SDS-PAGE and Western immunoblotting. The bioactivity were assessed in vivo using subcutaneous injection in mice.

Results

Results showed accurate molecules were produced and purified. Also, in vivo experiment showed significant increment (more than two fold) of platelets compared to control group.

Conclusion

In this study laboratory scale production of recombinant romiplostim showed proper in-vivo bioactivity. This new approach in expression and purification of this recently introduced thrombopoietin receptor agonist drug may be followed by scale up of its production to response the chronic ITP patient’s demand.

Bioanalysis of target biomarker and PK/PD relevancy during the development of biotherapeutics

The majority of biotherapeutic drugs act on specific targets, which may serve as biomarkers to be evaluated for target engagement and validation. Together with subsequent pathway biomarkers, these data can provide proof-of-mechanism and understanding of the biological drug affect. A major task during early development is to predict, for the first first time in human clinical trials, the starting dose and simulate the PK/PD relationship. However, determinations of the biotherapeutic drug and target concentrations are not straightforward due to temporal changes of drug–target binding and challenges in developing reliable methods to measure the free and total drug and target. Herein, the bioanalysis of the target biomarker and the biotherapeutics in the context of PK/PD relevancy during drug development is reviewed. Binding of the target to the biotherapeutic will affect target clearance and drug disposition, resulting in nonlinear PK. Reliable and specific methods are crucial for the correct PK/PD modeling and interpretation.

The burden of immune thrombocytopenia in adults: evaluation of the thrombopoietin receptor agonist romiplostim

BACKGROUND

Immune thrombocytopenia (ITP) is a chronic, immune-mediated disease characterized by a transient or long-lasting decrease in platelet counts. ITP is associated with numerous serious clinical consequences. Discussed here are clinical aspects of ITP, the humanistic and economic burden of ITP, and current treatment options with a focus on romiplostim, a thrombopoietin (TPO) receptor agonist. The aim of this review is to provide decision-makers with the background information necessary to evaluate the value of romiplostim.

SCOPE

PubMed was searched for relevant, English-language papers published from January 2006 through November 2011 relating to the epidemiology and treatment options of chronic ITP, and, focusing on the TPO mimetic romiplostim, patient-reported outcomes (PRO) and economic burden. Recent select conference abstracts were also reviewed.

FINDINGS

The initial clinical management of ITP (e.g., corticosteroids, immunoglobulins) is often associated with adverse events and recommended for short-term use only. Splenectomy, a potentially curative second-line treatment, is associated with increased risks of bleeding and infection, and patients often require additional long-term drug intervention. ITP and its sequelae are associated with a substantial burden on patients' health-related quality-of-life (HRQoL) and increased medical costs. Use of TPO receptor agonists in ITP patients may represent a more efficient use of healthcare resources than existing therapies.

CONCLUSION

While this literature review is not a systematic review, e.g., it considers only approved therapies and published literature written in English, it provides a comprehensive overview of the clinical, humanistic, and economic factors that should be considered in treating ITP, particularly with new agents such as romiplostim. Among the limited number of safe and effective therapies currently available for chronic ITP, highly effective and well-tolerated medications such as romiplostim may reduce the healthcare resource utilization associated with ITP while improving patients' HRQoL.

Total remission of severe immune thrombocytopenia after short term treatment with romiplostim

Immune thrombocytopenia (ITP) in adults is an acquired chronic immune-mediated disorder defined by isolated thrombocytopenia. In recent years, an improved understanding of the pathophysiology of ITP has been achieved and it is now accepted that the disorder is due to increased platelet destruction and decreased platelet production from megakary-ocytes. Thrombopoietin (TPO)-receptor agonists (romiplostim and eltrombopag) are new therapeutic modalities in the treatment of ITP. Here we describe a case of an elderly patient with severe ITP who presented complete remission after short-term use of romiplostim (only 3 weekly doses). This finding is quite interesting as the TPO-receptor agonists are, so far, believed to rarely lead to off-treatment sustained remission. The common notion of long-term use of romiplostim could be reexamined in future studies. Furthermore, the short term treatment with romiplostim may reduce the cost and the risk of side effects.

[Pharmacologic treatment for 2 thrombocytopenic patients prior to neurosurgery]

Preoperative prophylaxis of hemorrhage for patients with thrombocytopenia or a platelet disorder is controversial. Platelet count correlates to a certain degree with risk of hemorrhage, and risk factors for hemorrhage should be assessed and treated before deciding on perioperative treatments. Thirteen percent of cirrhotic patients have a platelet count between 50,000 and 75,000/microL and thrombocytopenia is multifactorial in origin. Idiopathic thrombocytopenic purpura is an acquired disease; since it may be either primary or secondary to other conditions, treatment may vary considerably. No clinical method has been established for predicting risk of perioperative bleeding in patients with thrombocytopenia. We describe 2 thrombocytopenic patients scheduled for intracranial surgery who were treated with thrombopoietic growth factors; in both cases, platelet counts increased sufficiently for this type of surgery. Controlled clinical trials are needed to ascertain the safety and prophylactic utility of platelet transfusion and thrombopoietin analogs in certain situations of refractory thrombocytopenia.

Ligand-binding mass spectrometry to study biotransformation of fusion protein drugs and guide immunoassay development: strategic approach and application to peptibodies targeting the thrombopoietin receptor

The knowledge of in vivo biotransformation (e.g., proteolysis) of protein therapeutic candidates reveals structural liabilities that impact stability. This information aids the development and confirmation of ligand-binding assays with the required specificity for bioactive moieties (including intact molecule and metabolites) for appropriate PK profiling. Furthermore, the information can be used for re-engineering of constructs to remove in vivo liabilities in order to design the most stable candidates. We have developed a strategic approach of ligand-binding mass spectrometry (LBMS) to study biotransformation of fusion proteins of peptides fused to human Fc ("peptibodies") using anti-human Fc immunoaffinity capture followed by tiered mass spectrometric interrogation. LBMS offers the combined power of selectivity of ligand capture with the specificity and detailed molecular-level information of mass spectrometry. In this paper, we demonstrate the preclinical application of LBMS to three peptibodies, AMG531 (romiplostim), AMG195(linear), and AMG195(loop), that target the thrombopoietin receptor. The data show that ligand capture offers excellent sample cleanup and concentration of intact peptibodies and metabolites for subsequent query by matrix-assisted laser desorption ionization time-of-flight mass spectrometry for identification of in vivo proteolytic points. Additional higher-resolution analysis by nanoscale liquid chromatography interfaced with electrospray ionization mass spectrometry is required for identification of heterogeneous metabolites. Five proteolytic points are accurately identified for AMG531 and two for AMG195(linear), while AMG195(loop) is the most stable construct in rats. We recommend the use of LBMS to assess biotransformation and in vivo stability during early preclinical phase development for all novel fusion proteins.