Pharmacodynamics and pharmacokinetics of AMG 531, a novel thrombopoietin receptor ligand

A practical guide to the management of immune thrombocytopenia co-existing with acute coronary syndrome

Introduction

Immune thrombocytopenia (ITP) management with co-existing acute coronary syndrome (ACS) remains challenging as it requires a clinically relevant balance between the risk and outcomes of thrombosis and the risk of bleeding. However, the literature evaluating the treatment approaches in this high-risk population is scarce.

Methods and Results

In this review, we aimed to summarize the available literature on the safety of ITP first- and second-line therapies to provide a practical guide on the management of ITP co-existing with ACS. We recommend holding antithrombotic therapy, including antiplatelet agents and anticoagulation, in severe thrombocytopenia with a platelet count < 30 × 109/L and using a single antiplatelet agent when the platelet count falls between 30 and 50 × 109/L. We provide a stepwise approach according to platelet count and response to initial therapy, starting with corticosteroids, with or without intravenous immunoglobulin (IVIG) with a dose limit of 35 g, followed by thrombopoietin receptor agonists (TPO-RAs) to a target platelet count of 200 × 109/L and then rituximab.

Conclusion

Our review may serve as a practical guide for clinicians in the management of ITP co-existing with ACS.

Population Pharmacokinetic and Pharmacodynamic Modeling of Romiplostim Biosimilar GP40141 and Reference Product in Healthy Volunteers to Evaluate Biosimilarity

GP40141 is a romiplostim biosimilar. A Phase 1 clinical trial was previously conducted in healthy volunteers to evaluate the pharmacodynamics (PD), pharmacokinetics (PK), and safety of GP40141 compared to the reference romiplostim (NCT05652595). Using noncompartmental analysis, the biosimilarity of PD end points was determined according to the classical criterion (0.8-1.25). PK end points were also in good agreement between GP40141 and the reference romiplostim; however, the confidence interval for the area under concentration-time curve from time 0 to the time of last measurement was slightly out of the bioequivalence range (0.91-1.29). Population PK/PD was used in the present study to characterize the individual PK and PD data of 56 healthy subjects in 2 cross-over periods of the Phase 1 clinical trial. Body weight and neutralizing antibodies to romiplostim were found to be important predictors of apparent volume of distribution and linear elimination constant, respectively. Within the framework of the conducted modeling, population estimates of PK/PD parameters were obtained, which were in agreement with literature data for the reference romiplostim. Additionally, values of intersubject variability, previously unreported for romiplostim in a healthy subject population, were derived. Covariate analysis, conducted during model development, as well as visual diagnostics and model-based simulations, demonstrated the absence of significant differences in PK and PD between GP40141 and romiplostim-ref.

Thrombopoietin receptor agonist and rituximab combination therapy in patients with refractory primary immune thrombocytopenia

The aim of our study was to evaluate the efficacy of this therapy in patients with refractory primary immune thrombocytopenia. It is crucial to develop alternative treatment methods for this patient group in order to achieve better response. This combination therapy combines two different mechanisms of action, which is promising in terms of targeting pathophysiology of immune thrombocytopenia. We conducted a retrospective study, which included all patients who were diagnosed with refractory primary immune thrombocytopenia and received TPO-RA and rituximab at the General Hematology Department, Copernicus Memorial Hospital in Lodz, Poland. We assessed the response, time to response and treatment-free remission (TFR). After 1 month of treatment, the complete response (CR1, PLT >100 g/l) was achieved in 62.5% patients, and response (R1, PLT >30 g/l) was achieved in 62.5% patients. The median PLT was 175 × 10 9 /l. Within 1 month of treatment, 87.5% of patients achieved TFR. Adequately, after 6 months, CR6 and R6 was 62.5 and 75%. The median PLT was 182 × 10 9 /l. Treatment-free remission 6 months after completion was in 50% of patients. The study group achieved response to treatment, which suggests that combination of TPO-RA and rituximab is effective and relatively well tolerated. Prospective study on larger group of patients is needed to better evaluate the efficiency and safety of this treatment.

Purification and Activity Evaluation of a Novel Thrombopoietin Mimetic Peptide

The emergence of thrombopoietin mimetic peptides presents a promising therapeutic strategy for addressing thrombocytopenia. This particular study aimed to establish a direct, expeditious, and efficient method for modifying and purifying a novel thrombopoietin mimetic peptide. Precursor proteins were subjected to modification utilizing three distinct fatty acids: C25H42O7N2, C39H66O15N4, and C41H70O15N4. Liquid chromatography analyses demonstrated that C41H70O15N4 yielded the most effective modification results. Mass spectrometry findings validated the correspondence between the theoretical and actual molecular weights of each sample. In vivo experiments conducted on normal mice showcased that the C41H70O15N4 modification group exhibited the highest platelet count, peaking at an impressive 5047 × 109/L. This count was approximately twice that of the peak platelet count observed in the dTMP group and four times higher than the control group. Pharmacokinetic investigations revealed that the C41H70O15N4 modification group displayed the lengthiest half-life among beagles, persisting for 128.5 h. This duration was approximately 28.5 times longer than that of the unmodified dTMP group. These findings underscore the effectiveness of the established C41H70O15N4 modification and purification method in preserving the biological activity of the thrombopoietin mimetic peptide. The novel thrombopoietin mimetic peptide showcased notable attributes of simplicity and cost-effectiveness, while also exhibiting a significant platelet-promoting effect and an extended half-life. Consequently, this novel peptide holds substantial significance for advancing the treatment of thrombocytopenia.

A Review on Romiplostim Mechanism of Action and the Expressive Approach in E. coli

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder determined by immune-mediated platelet demolition and reduction of platelet production. Romiplostim is a new thrombopoiesis motivating peptibody that binds and stimulates the human thrombopoietin receptor the patent of which was registered in 2008. It is used to treat thrombocytopenia in patients with chronic immune thrombocytopenic purpura. Romiplostim is a 60 kDa peptibody designed to inhibit cross-reacting immune responses. It consists of four high-affinity TPO-receptor binding domains for the Mpl receptor and one human IgG1 Fc domain. Escherichia coli is a good host for the fabrication of recombinant proteins such as romiplostim. The expression of a gene intended in E. coli is dependent on many factors such as a protein's inherent ability to fold, mRNA's secondary structure, its solubility, its toxicity preferential codon use, and its need for post-translational modification (PTM). This review focuses on the structure, function, mechanism of action, and expressive approach to romiplostim in E. coli.

Thrombopoietin-receptor agonists for adult patients with immune thrombocytopenia: a narrative review and an approach for managing patients fasting intermittently

Introduction

Thrombopoietin-receptor agonist (TPO-RAs) currently represent the state of art for treating immune thrombocytopenia. Their different molecular structures contribute to the difference in their pharmacodynamics and pharmacokinetics. This narrative review aims to provide an overview of the current TPO-RAs approved for primary immune thrombocytopenia (romiplostim, eltrombopag, avatrombopag) and the effect of intermittent fasting in adult patients receiving TPO-RAs.

Areas covered

Literature was searched with no limits on date or language, using various combinations of keywords. Data on the pharmacokinetics, pharmacodynamics, efficacy, and safety of TPO-RAs and the effect of intermittent fasting were summarized.

Expert opinion

Switching between TPO-RAs is a useful strategy to tackle some associated limitations. Romiplostim and avatrombopag have an advantage over eltrombopag as they do not require any dietary restrictions. In cases where romiplostim and avatrombopag are unavailable, patients should be educated on the appropriate administration, possible interactions, and dietary restrictions before initiating eltrombopag.

Survival and Hematologic Benefits of Romiplostim After Acute Radiation Exposure Supported FDA Approval Under the Animal Rule

PURPOSE

Patients exposed to acute high doses of ionizing radiation are susceptible to dose-dependent bone marrow depression with resultant pancytopenia. Romiplostim (RP; Nplate) is a recombinant thrombopoietin receptor agonist protein that promotes progenitor megakaryocyte proliferation and platelet production and is an approved treatment for patients with chronic immune thrombocytopenia. The goal of our study was to evaluate the postirradiation survival and hematologic benefits of a single dose of RP with or without pegfilgrastim (PF; Neulasta, granulocyte colony stimulating factor) by conducting a well-controlled, treatment-concealed, good laboratory practice-compliant study in rhesus macaques that was compliant with the United States Food and Drug Administration Animal Rule regulatory approval pathway.

METHODS AND MATERIALS

Irradiated male and female rhesus macaques (20/sex in each of 3 groups: control, RP, and RP + PF) were subcutaneously administered vehicle or RP (5 mg/kg, 10 mL/kg) on day 1 in the presence or absence of 2 doses of PF (0.3 mg/kg, 0.03 mL/kg, days 1 and 8). Total body radiation (680 cGy, 50 cGy/min from cobalt-60 gamma ray source) occurred 24 ± 2 hours previously at a dose targeting 70% lethality for the control cohort over 60 days. The study examined 60-day survival postirradiation as the primary endpoint. Secondary endpoints included incidence, severity, and duration of thrombocytopenia and neutropenia, other hematology parameters, coagulation parameters, and body weight change to provide insights into potential mechanisms of action.

RESULTS

Compared with sham-treated controls, treated animals demonstrated a 40% to 55% survival benefit compared with controls, less severe clinical signs, reduced incidence of thrombocytopenia and/or neutropenia, earlier hematologic recovery, and reduced morbidity from bacterial infection.

CONCLUSIONS

These results were pivotal in obtaining Food and Drug Administration approval in January 2021 for RP's new indication as a single administration therapy to increase survival in adults and pediatric patients acutely exposed to myelosuppressive doses of radiation.

A randomized, double-blind, comparative study of the pharmacodynamics and pharmacokinetics of GP40141 (romiplostim biosimilar) and reference romiplostim in healthy male volunteers

AIMS

The pharmacodynamic (PD) similarity between GP40141, a proposed romiplostim biosimilar, and reference romiplostim was evaluated. Pharmacokinetics and safety were also assessed.

METHODS

In this phase 1, randomized, double-blind, single-dose, crossover comparative study with an adaptive design, 56 healthy male volunteers were randomized 1:1 to receive a 3 ug × kg-1 subcutaneous dose of GP40141 and reference romiplostim. The PD similarity between GP40141 and the reference romiplostim was determined using the standard equivalence criteria (80%-125%) for the area under the platelet count-time curve from time 0 to the time of the last sampling for PD (AUCplt ) and the maximum observed platelet count (Pmax ).

RESULTS

GP40141 and the reference romiplostim exhibited similar PD profiles. 90% CI for the geometric mean ratios for the primary PD parameters (AUCplt, Pmax ) for GP40141 (T) and the reference romiplostim (R) were fully contained within the predefined equivalence limits of 80%-125%: 98.13%-102.42% for AUCplt and 97.56%-105.80% for Pmax . The pharmacokinetic profiles of GP40141 and the reference romiplostim were well described. No adverse events were observed during the clinical trial after the administration of GP40141 and the reference romiplostim.

CONCLUSION

This study demonstrates the PD similarity of GP40141 to the reference romiplostim. Both treatments had comparable safety profiles (NCT05652595).

Chromatography assisted in-vitro refolding and purification of recombinant peptibody: Recombinant Romiplostim a case study

In-vitro protein refolding is one of the key rate-limiting unit operations in manufacturing of fusion proteins such as peptibodies expressed using E. coli. Dilution-assisted refolding is the most commonly used industrial practice to achieve the soluble, native functional form of the recombinant protein from the inclusion bodies. This study is focused on developing a chromatography-assisted in-vitro refolding platform to produce the biologically active, native form of recombinant peptibody. Recombinant Romiplostim was selected as a model protein for the study. A plug flow tubular reactor was connected in series with capture step affinity chromatography to achieve simultaneous in-vitro refolding and capture step purification of recombinant Romiplostim. Effect of various critical process parameters like fold dilution, temperature, residence time, and Cysteine: DTT ratio was studied using a central composite based design of experiment strategy to achieve a maximum refolding yield of selected peptibody. Under optimum refolding conditions, the maximum refolding yield of 57.0 ± 1.5 % and a purity of over 79.73 ± 3.4 % were achieved at 25-fold dilution, 15 °C temperature, 6 h residence time with 6 mM and 10 mM of cysteine and DTT, respectively. The formation of native peptibody structure was examined using various orthogonal analytical tools to study the protein's primary, secondary, and tertiary structure. The amino acid sequence for the disulfide-linked peptide was mapped using collision-induced dissociation (CID) to confirm the formation of interchain disulfide bonds between Cys7-Cys7 and Cys10-Cys10 similarly for intra-chain disulfide bonds between Cys42-Cys102, and Cys148-Cys206. The developed protocol here is a valuable tool to identify high-yield scalable refolding conditions for multi-domain proteins involving inter-domain disulfide bonds.

Primary and secondary immune thrombocytopenia (ITP): Time for a rethink

There are not many publications that provide a holistic view of the management of primary and secondary ITP as a whole, reflecting the similarities and differences between the two. Given the lack of major clinical trials, we believe that comprehensive reviews are much needed to guide the diagnosis and treatment of ITP today. Therefore, our review addresses the contemporary diagnosis and treatment of ITP in adult patients. With respect to primary ITP we especially focus on establishing the management of ITP based on the different and successive lines of treatment. Life-threatening situations, "bridge therapy" to surgery or invasive procedures and refractory ITP are also comprehensively reviewed here. Secondary ITP is studied according to its pathogenesis by establishing three major differential groups: Immune Thrombocytopenia due to Central Defects, Immune Thrombocytopenia due to Blocked Differentiation and Immune Thrombocytopenia due to Defective Peripheral Immune Response. Here we provide an up-to-date snapshot of the current diagnosis and treatment of ITP, including a special interest in addressing rare causes of this disease in our daily clinical practice. The target population of this review is adult patients only and the target audience is medical professionals.

Efficacy and Safety of Biosimilar Romiplostim Versus Innovator Romiplostim in Patients with Chronic Immune Thrombocytopenia

Romiplostim is a Food and Drug Administration (FDA)-approved therapy for immune thrombocytopenia (ITP). Biosimilar is a biological product that has no clinical meaningful difference from an existing FDA-approved reference product. It has a potential of lowering health-care-related cost. Biosimilar of romiplostim can be made available to patients with ITP at a low cost and can be beneficial in providing the best therapy. Thus, the efficacy and safety of biosimilar romiplostim (ENZ110) was compared with innovator romiplostim (Nplate) with respect to platelet response in patients with chronic ITP. This was a prospective, multicenter, randomized, and double-blind clinical trial. Patients with chronic ITP, aged 18-65 years, were enrolled in a study and were randomized to receive either ENZ110 or Nplate in a 3:1 ratio for a treatment period of 12 weeks, respectively. After completion of the treatment period, the patients were followed-up for one week to evaluate the platelet response and to monitor the adverse events (AEs). Over the duration of 12 weeks, platelet response of > 50 × 109/L was achieved in 85.3% patients treated with ENZ110 and in 75.0% patients treated with Nplate in per protocol population. In intent-to-treat population, 83.8% patients with ENZ110 and 76.9% patients with Nplate achieved a platelet response of > 50 × 109/L. In the ENZ110 group, 111 AEs were recorded in 66.7% patients, while 18 AEs were reported in 61.5% patients in the Nplate group. The study demonstrated non-inferiority with comparable efficacy and safety between biosimilar romiplostim and innovator romiplostim in patients with chronic ITP. Trial registration number and date of registration: CTRI/2019/04/018614.

Romiplostim in primary immune thrombocytopenia that is persistent or chronic: phase III multicenter, randomized, placebo-controlled clinical trial in China

Background

Multiple trials have confirmed that romiplostim could increase platelet count in individuals with primary immune thrombocytopenia (ITP), but no related study has assessed Chinese patients.

Objectives

To assess the effectiveness of romiplostim as a second-line treatment of persistent or chronic ITP in Chinese adults.

Methods

This phase III multicenter, randomized, placebo-controlled, double-blind, then open-label clinical trial (NCT02868099, CTR20150395) was conducted at 28 investigational sites in China. The patients were randomly assigned (3:1) to romiplostim (starting and maximum doses of 1 and 10 μg/kg, respectively) or placebo for 9 weeks (double-blind period), followed by the open-label period (both groups administered romiplostim) to week 22. The primary endpoint was the time (in weeks) during which platelet counts were ≥50 × 109/L in the double-blind period.

Results

In this study, 202 patients (romiplostim, n = 151; placebo, n = 51) started the treatment. The median (range) numbers of weeks with platelet response after 6 weeks of treatment were 2 (0-6) and 0 (0-2) in patients administered romiplostim and placebo, respectively (P < .001). During the double-blind period, the proportions of patients with treatment-emergent adverse events were comparable between the romiplostim and placebo groups (82.8% vs 82.4%). The treatment-emergent adverse event with ≥10% difference in incidence between these 2 groups was injection site bleeding (1.3% vs 11.8%).

Conclusion

Romiplostim significantly increased the time with maintained platelet response in patients with persistent or chronic ITP in comparison with placebo. No new safety signal was observed.

Trial registration

ClinicalTrials.gov, NCT02868099. www.chinadrugtrials.org.cn/clinicaltrials.searchlist.dhtml, CTR20150395.

Early initiation of second-line therapy in primary immune thrombocytopenia: insights from real-world evidence

To compare patients with primary immune thrombocytopenia (ITP) prescribed early (within 3 months of initial ITP treatment) second-line treatment (eltrombopag, romiplostim, rituximab, immunosuppressive agents, splenectomy) with or without concomitant first-line therapy to those who received only first-line therapy. This real-world retrospective cohort study of 8268 patients with primary ITP from a large US-based database (Optum^® de-identified Electronic Health Record [EHR] dataset) combined electronic claims and EHR data. Outcomes included platelet count, bleeding events, and corticosteroid exposure 3 to 6 months after initial treatment. Baseline platelet counts were lower in patients receiving early second-line therapy (10‒28 × 10⁹/L) versus those who did not (67 × 10⁹/L). Counts improved and bleeding events decreased from baseline in all treatment groups 3 to 6 months after the start of therapy. Among the very few patients for whom follow-up treatment data were available (n = 94), corticosteroid use was reduced during the 3- to 6-month follow-up period in patients who received early second-line therapy versus those who did not (39% vs 87%, p < 0.001). Early second-line treatment was prescribed for more severe cases of ITP and appeared to be associated with improved platelet counts and bleeding outcomes 3 to 6 months after initial therapy. Early second-line therapy also appeared to reduce corticosteroid use after 3 months, although the small number of patients with follow-up data on treatment precludes any substantive conclusions. Further research is needed to determine whether early second-line therapy has an effect on the long-term course of ITP.

Sustained Remission Off-Treatment (SROT) of TPO-RAs: The Burgos Ten-Step Eltrombopag Tapering Scheme

Background and Objectives: TPO-RAs (romiplostim/eltrombopag/avatrombopag) have broadly demonstrated high efficacy rates (59-88%), durable responses (up to three years) and a satisfactory safety profile in clinical trials. The effect of TPO-RAs is classically considered to be transient because platelet numbers usually dropped rapidly to baseline unless therapy was maintained. However, several groups have reported the possibility of successfully discontinuing TPO-RAs in some patients without further need for concomitant treatments. This concept is usually referred as sustained remission off-treatment (SROT). Materials and Methods: Unfortunately, we still lack predictors of the response to discontinuation even after the numerous biological, clinical and in vitro studies performed to study this phenomenon. The frequency of successful discontinuation is matter of controversy, although a percentage in the range of 25-40% may probably be considered a consensus. Here, we describe all major routine clinical practice studies and reviews that report the current position on this topic and compare them with our own results in Burgos. Results: We report our Burgos ten-step eltrombopag tapering scheme with which we have achieved an elevated percentage rate of success (70.3%) in discontinuing treatment. Conclusions: We hope this protocol may help successfully taper and discontinue TPO-RAs in daily clinical practice.

A bibliometric analysis of primary immune thrombocytopenia from 2011 to 2021

Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia. This bibliometric analysis was applied to identify the characteristics of global scientific output, the hotspots, and frontiers of ITP over the past 10 years. We retrieved publications from 2011 to 2021 from the Web of Science Core Collection (WoSCC). Bibliometrix package, VOSviewer, and Citespace were used to analyse and visualize the trend, distribution, and hotspots of research on ITP. Altogether, there were 2084 papers, written by 9080 authors from 410 organizations in 70 countries/regions, published in 456 journals with 37 160 co-cited references. In the last decades, the most productive journal was British Journal of Haematology, China was the most productive country. and the most cited journal was Blood. Shandong University was the most productive institution in the field of ITP. NEUNERT C, 2011, BLOOD, CHENG G, 2011, LANCET, and PATEL VL, 2012, BLOOD were the top three most cited documents. "Thrombopoietin receptor agonist", "regulatory T cell" and "sialic acid" were three hotspots of the last decade. And "immature platelet fraction", "Th17", and "fostamatinib" would be research frontiers in the feature. The present study provided a novel insight for future research directions and scientific decision-making.

Looking for the phoenix: the current research on radiation countermeasures

PURPOSE

Ionizing radiation (IR) is widely applied in radiotherapy for the treatment of over 50% of cancer patients. IR is also intensively used in medical diagnostics on a daily basis in imaging. Moreover, recent geopolitical events have re-ignited the real threat of the use of nuclear weapons. Medical radiation countermeasures represent one of the effective protection strategies against the effects of IR. The aim of this review was to summarize the most commonly used strategies and procedures in the development of radiation countermeasures and to evaluate the current state of their research, with a focus on those in the clinical trial phase.

METHODS

Clinical trials for this review were selected in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. The search was performed in the clinicaltrials.gov database as of May 2022.

RESULTS

Our search returned 263 studies, which were screened and of which 25 were included in the review. 10 of these studies had been completed, 3 with promising results: KMRC011 increased G-CSF, IL-6, and neutrophil counts suggesting potential for the treatment of hematopoietic acute radiation syndrome (H-ARS); GC4419 reduced the number of patients with severe oral mucositis and its duration; the combination of enoxaparin, pentoxifylline, and ursodeoxycholic acid reduced the incidence of focal radiation-induced liver injury.

CONCLUSION

The agents discovered so far show significant side effects or low efficacy, and hence most of the tested agents terminate in the early stages of development. In addition, the low profitability of this type of drug demotivates the private sector to invest in such research. To overcome this problem, there is a need to involve more public resources in funding. Among the technological opportunities, a deeper use of in silico approaches seems to be prospective.

Megakaryopoiesis impairment through acute innate immune signaling activation by azacitidine

Thrombocytopenia, prevalent in the majority of patients with myeloid malignancies, such as myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML), is an independent adverse prognostic factor. Azacitidine (AZA), a mainstay therapeutic agent for stem cell transplant-ineligible patients with MDS/AML, often transiently induces or further aggravates disease-associated thrombocytopenia by an unknown mechanism. Here, we uncover the critical role of an acute type-I interferon (IFN-I) signaling activation in suppressing megakaryopoiesis in AZA-mediated thrombocytopenia. We demonstrate that megakaryocytic lineage-primed progenitors present IFN-I receptors and, upon AZA exposure, engage STAT1/SOCS1-dependent downstream signaling prematurely attenuating thrombopoietin receptor (TPO-R) signaling and constraining megakaryocytic progenitor cell growth and differentiation following TPO-R stimulation. Our findings directly implicate RNA demethylation and IFN-I signal activation as a root cause for AZA-mediated thrombocytopenia and suggest mitigation of TPO-R inhibitory innate immune signaling as a suitable therapeutic strategy to support platelet production, particularly during the early phases of AZA therapy.

Medical management of acute radiation syndrome

Acute radiation syndrome (ARS) is a clinical syndrome involving four organ systems, resulting in the hematopoietic syndrome (HS), gastrointestinal subsyndrome (GIS), neurovascular subsyndrome (NVS) and cutaneous subsyndrome (CS). Since few healthcare providers have seen an ARS case, evidence-based recommendations are needed to guide medical management in a mass casualty scenario. The authors reviewed recommendations from evidence-based and narrative reviews by expert consultants to the World Health Organisation (WHO), a subsequent review of published HS cases, and infectious disease guidelines for management of febrile neutropenia. The WHO Consultancy applied a rigorous grading system to evaluate treatment strategies described in published ARS cases as of 2009, strategies to manage HS in unirradiated persons, results of ARS studies in animal models of ARS, and recommendations of prior expert panels. Major findings for HS were (a) no randomised controlled studies have been performed, (b) data are restricted by the lack of comparator groups, and (c) reports of countermeasures for management of injury to non-hematopoietic organs are often incomplete. Strength of recommendations ranged from strong to weak. Countermeasures of potential benefit include cytokines and for a subgroup of HS patients, hematopoietic stem cell transplantation. These recommendations did not change in a subsequent analysis of HS cases. Recommendations also included fluoroquinolones, bowel decontamination, serotonin receptor antagonists, loperamide and enteral nutrition for GIS; supportive care for NVS; and topical steroids, antihistamines and antibiotics, and surgical excision/grafting for CS. Also reviewed are critical care management guidelines, the role of mesenchymal stem cells for CS, the potential of a platelet-stimulating cytokine for HS, and the author's approach to clinical management of microbial infections associated with ARS based on published guidelines of infectious disease experts. Today's management of HS is supported by evidence-based guidelines. Management of non-HS subsyndromes is supported by a narrative review of the literature and recommendations of infectious disease societies.

Chemotherapy-induced thrombocytopenia in Ewing sarcoma: Implications and potential for romiplostim supportive care

BACKGROUND

Maintaining dose-dense, interval-compressed chemotherapy improves survival in patients with Ewing sarcoma but is limited by myelosuppression. Romiplostim is a thrombopoietin receptor agonist that may be useful in the treatment of chemotherapy-induced thrombocytopenia (CIT).

METHODS

Patients aged between 3 and 33 years with Ewing sarcoma from 2010 to 2020 were reviewed. CIT was defined as a failure to achieve 75,000 platelets per microliter by day 21 after the start of any chemotherapy cycle. Fisher's exact test was used for univariate analysis and Pearson's correlation coefficient was used for the association between continuous variables.

RESULTS

Twenty-seven out of 42 patients (64%) developed isolated CIT, delaying one to four chemotherapy cycles per patient. CIT occurred during consolidation therapy in 24/27(88.9%) and with ifosfamide/etoposide cycles in 24/27 (88.9%). Univariate analysis failed to identify risk factors for CIT. The use of radiation approached significance (p-value = .056). Ten patients received romiplostim. The median starting dose was 3 μg/kg (range 1-5). Doses were escalated weekly by 1-2 to 4-10 μg/kg and continued throughout chemotherapy. A higher romiplostim dose was associated with a higher change in average platelet counts from baseline, r = .73 (p = .04). No romiplostim-related adverse events were identified aside from mild headache.

CONCLUSIONS

CIT is the primary reason for the inability to maintain treatment intensity in Ewing sarcoma. The concurrent use of romiplostim with chemotherapy was safe and feasible, and efficacy was associated with higher romiplostim doses.

Safety, tolerance, pharmacokinetic and pharmacodynamic properties of thrombopoietin mimetic peptide for injection in Chinese healthy volunteers: a randomized, placebo-controlled, double-blind study

The thrombopoietin mimetic peptide for injection is a second-generation thrombopoietin receptor agonist (TPO-RA) used in the treatment of patients with immune thrombocytopenia. The aim of the present study was to assess the safety, tolerance, pharmacokinetic and pharmacodynamic properties of thrombopoietin mimetic peptide for injection in Chinese healthy volunteers. A randomized, placebo-controlled, double-blind, dose-escalation study was conducted in healthy Chinese subjects aged 18-50 years. Thirty subjects received single subcutaneous injection of 0.3 μg/kg, 1.0 μg/kg, 2.0 μg/kg thrombopoietin mimetic peptide or placebo. Thrombopoietin mimetic peptide was safe and well tolerated at doses of 0.3-2.0 μg/kg. There was no significant change in mean platelet count (PLT) from baseline at the 0.3 μg/kg or placebo groups. The mean PLT of subjects in the 1.0 μg/kg and 2.0 μg/kg groups peaked at day 12 (± 1), began to decline around day 17, and returned to the baseline level at day 28 (± 1). Platelet aggregation rates of the three dose groups showed no significant change before and after administration. Serum concentrations of thrombopoietin mimetic peptide in all subjects were below the quantization limit. This was the first study to demonstrate that subcutaneous injection of thrombopoietin mimetic peptide at doses of 0.3-2.0 μg/kg was safe and well tolerated in Chinese healthy subjects. As a second-generation TPO-RA, thrombopoietin mimetic peptide is effective at improving PLT after single subcutaneous injection at dose of ≥1 μg/kg.Plain language summaryWhat is the context?● Immune thrombocytopenia (ITP) is a rare, serious autoimmune disorder characterized by low platelet count (PLT) without an alternate cause. The treatment goal of ITP is to increase the platelet count to a safe level that can stop active bleeding and reduce the risks of future bleeding.● Thrombopoietin receptor agonists (TPO-RAs, e.g. eltrombopag, avatrombopag, hetrombopag, and romiplostim) have shown high response rates in stimulating platelet production and reducing the risk of bleeding. TPO-RAs provide ITP patients with well-tolerated, long-term treatment choices.What is new?● The thrombopoietin mimetic peptide for injection is a new TPO-RAs developed by Shandong Quangang Pharmaceutical Co., Ltd. (China).● This study showed that thrombopoietin mimetic peptide is effective at improving PLT after a single subcutaneous injection.● The thrombopoietin mimetic peptide is safe and well-tolerated in Chinese healthy subjects.What is the impact?● This study provides evidence for the further development potential of the thrombopoietin mimetic peptide.

Pharmacokinetics, Pharmacodynamics, Efficacy and Safety of a Romiplostim Biosimilar in Chronic Refractory Immune Thrombocytopenic Purpura (ITP) Patients

Romiplostim (Nplate®, Amgen Inc.) is an orphan drug approved for the treatment of chronic refractory immune thrombolytic purpura (ITP) in adult and pediatric patients. Limited availability of pharmacokinetic (PK) data and large inter- and intra-subject variability in PK and platelet response is a challenge in the clinical development of a romiplostim biosimilar. We compared pharmacokinetics (PK), pharmacodynamics (PD)/efficacy, and safety of a romiplostim biosimilar with Nplate in 24 patients with ITP following a single 3 μg/kg dose, and assessed efficacy of the romiplostim biosimilar at a titrated dose range of 1-5 μg/kg in 50 patients with ITP. The PK of the romiplostim biosimilar did not differ compared to the PK of Nplate, and PD/efficacy responses were similar between the products following the single dose. The romiplostim biosimilar showed historically comparable PD/efficacy with Nplate over 8 weeks when treated at the titrated dose range. It was well tolerated in both the studies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12288-021-01431-y.

Pharmacokinetics, Safety, and Pharmacodynamics of Romiplostim in Chinese Subjects With Immune Thrombocytopenia: A Phase I/II Trial

Romiplostim is approved for the treatment of immune thrombocytopenia (ITP). This study aimed to evaluate the pharmacokinetics, safety, and pharmacodynamics of romiplostim in Chinese patients with ITP. This multicenter, open-label, dose-escalation phase I/II trial enrolled ITP patients from 5 centers in China between October 2015 and August 2017. There were 2 cohorts: 1 μg/kg and 3 μg/kg weekly for 2 weeks. The end points included pharmacokinetics, platelet changes from baseline, hematological indicators, and adverse events (AEs). Sixteen participants, with 8 patients in each cohort, were enrolled. In the 1 μg/kg cohort, time to maximum concentration was 4.00 (4.00-7.83) hours, maximum serum drug concentration was 52.0 (16.0-228.0) pg/mL, and area under the serum drug concentration-time curve from time 0 to the last detectable time point was 389 (32.0-5400) pg · h/mL. In the 3 μg/kg cohort, time to maximum serum drug concentration was 11.91 (4.00-12.00) hours, maximum serum drug concentration was 105.0 (25.5-313.0) pg/mL, and half-life was 12.7 (8.2-23.6) hours. The absolute change of peak platelet count from baseline was 14 (3-40) and 72 (3-369) ×10⁹ /L in the 1 and 3 μg/kg cohorts, respectively. Seven (87.5%) and eight (100%) participants had treatment-emergent AEs in 1 μg/kg cohort and 3 μg/kg cohort, respectively. No major AEs occurred in the 2 cohorts. Romiplostim (1 and 3 μg/kg) is safe and well tolerated in Chinese patients with ITP.

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

Thrombopoietin regulates platelet production through activation of the thrombopoietin receptor (TPO-R). TPO-R agonists (TPO-RAs) are available to treat thrombocytopenia in chronic immune thrombocytopenia (ITP), chronic liver disease (CLD) patients who are undergoing a procedure, severe aplastic anemia (SAA), and hepatitis C virus (HCV) infection. There are four TPO-RAs approved in the US and Europe: romiplostim (ITP), eltrombopag (ITP, SAA, HCV), avatrombopag (ITP, CLD), and lusutrombopag (CLD). It is important to understand pharmacological characteristics of these agents when evaluating treatment options. Avatrombopag interacts with the transmembrane domain of the TPO-RA and does not compete with endogenous thrombopoietin for TPO-R binding. Structural differences between avatrombopag and other TPO-RAs may impart differential downstream effects on cell signaling pathways, potentially resulting in clinically relevant differences in outcome. Avatrombopag has a favorable pharmacological profile with similar exposure in Japanese, Chinese, or Caucasian patients and no drug-drug interactions, food interactions, or potential for chelation.

Experts' review: the emerging roles of romiplostim in immune thrombocytopenia (ITP)

INTRODUCTION

The management of ITP has in recent years been transformed from reliance on immunosuppressants and splenectomy to targeted therapy with thrombopoietin receptor agonists (TPO-RA) that directly stimulate platelet production in the bone marrow. This has reduced the long-term infective complications and toxicities associated with the use of potent immunosuppressants and splenectomy. The welltolerated romiplostim, itself a novel drug construct called peptibody, has established itself, alongside other TPO-RA as the preferred 2nd line therapy in major international guidelines on treatment of ITP.

AREAS COVERED

This review summarizes the data from early licensing trials of romiplostim and discusses the real-world experience to date, the unexpected emerging data on treatment-free long-term remission achieved using TPO-RA, and the case for its early introduction in the therapeutic pathway. The emerging risk of thrombosis is also discussed.

EXPERT OPINION

The use of romiplostim and other TPO-RA will be increasingly brought forward in the management pathway of ITP with the prospect of modifying the long-term outcome of the disease by increasing sustained treatment-free remission. With the prospect of several new targeted therapies been introduced into clinical practice, TPO-RA will likely be a key component of future combination therapies for difficult cases.

Comparative Efficacy and Safety of Thrombopoietin Receptor Agonists in Adults With Thrombocytopenia: A Systematic Review and Network Meta-analysis of Randomized Controlled Trial

Thrombopoietin receptor agonists (TPO-RAs) play a crucial role in stimulating thrombopoiesis. However, conventional meta-analyses have shown inconsistent results regarding the efficacy of thrombopoietin receptor agonists versus placebo. Therefore, we performed a network meta-analysis to assess the effects of five TPO-RAs via indirect comparison. For this network meta-analysis, we considered randomized trials that included any of the following interventions: avatrombopag, lusutrombopag, eltrombopag, romiplostim, recombinant human thrombopoietin (rhTPO). We searched the Medline, PubMed, Embase, the Cochrane Library, and Web of Science databases for randomized controlled clinical trials from inception to January 31, 2021. We use randomized controlled clinical trials of TPO-RAs for treatment of immune thrombocytopenia in adults. The primary outcome was the number of patients achieving platelet response which was defined as the achievement of a platelet count of more than 30 or 50 cells × 10⁹/L in the absence of rescue therapy, and the secondary outcome was the therapy-related serious adverse events and incidence of bleeding episodes. To obtain the estimates of efficacy and safety outcomes, we performed a random-effects network meta-analysis. These estimates were presented as odds ratios with 95% confidence intervals. We use surface under the cumulative ranking probabilities to rank the comparative effects and safety of all drugs against the placebo. In total, 2,207 patients were analyzed in 20 clinical trials. All preparations improved the point estimates of platelet response when compared with the placebo. Avatrombopag and lusutrombopag had the best platelet response compared to the placebo, the former had a non-significant advantage compared to the latter [odds ratio (OR) = 1.91 (95% confidence interval: 0.52, 7.05)]. The treatments were better than eltrombopag, romiplostim, rituximab, and rhTPO + rituximab, with corresponding ORs of 3.10 (1.01, 9.51), 9.96 (2.29, 43.29), 33.09 (8.76, 125.02), and 21.31 (3.78, 119.98) for avatrombopag and 1.62 (0.63, 4.17), 5.21 (1.54, 17.62), 17.34 (5.15, 58.36), and 11.16 (2.16, 57.62) for lusutrombopag. Regarding bleeding, the placebo group had the highest probability of bleeding, whereas lusutrombopag had the lowest risk of bleeding when compared to the placebo. Adverse events were slightly higher in patients receiving rituximab than in those receiving placebo or other treatments. Overall, this meta-analysis showed that avatrombopag may yield the highest efficacy because it has the most favorable balance of benefits and acceptability.

A Review of Romiplostim Mechanism of Action and Clinical Applicability

Thrombocytopenia results from a variety of conditions, including radiation, chemotherapy, autoimmune disease, bone marrow disorders, pathologic conditions associated with surgical procedures, hematopoietic stem cell transplant (HSCT), and hematologic disorders associated with severe aplastic anemia. Immune thrombocytopenia (ITP) is caused by immune reactions that accelerate destruction and reduce production of platelets. Thrombopoietin (TPO) is a critical component of platelet production pathways, and TPO receptor agonists (TPO-RAs) are important for the management of ITP by increasing platelet production and reducing the need for other treatments. Romiplostim is a TPO-RA approved for use in patients with ITP in the United States, European Union, Australia, and several countries in Africa and Asia, as well as for use in patients with refractory aplastic anemia in Japan and Korea. Romiplostim binds to and activates the TPO receptor on megakaryocyte precursors, thus promoting cell proliferation and viability, resulting in increased platelet production. Through this mechanism, romiplostim reduces the need for other treatments and decreases bleeding events in patients with thrombocytopenia. In addition to its efficacy in ITP, studies have shown that romiplostim is effective in improving platelet counts in various settings, thereby highlighting the versatility of romiplostim. The efficacy of romiplostim in such disorders is currently under investigation. Here, we review the structure, mechanism, pharmacokinetics, and pharmacodynamics of romiplostim. We also summarize the clinical evidence supporting its use in ITP and other disorders that involve thrombocytopenia, including chemotherapy-induced thrombocytopenia, aplastic anemia, acute radiation syndrome, perisurgical thrombocytopenia, post-HSCT thrombocytopenia, and liver disease.

Severe, Refractory Immune Thrombocytopenia Occurring After SARS-CoV-2 Vaccine

The rollout of the SARS-CoV-2 vaccine is underway, and millions have already been vaccinated. At least 25 reports of "immune thrombocytopenia" (ITP) or "thrombocytopenia" following the Moderna or Pfizer vaccine have been added to the Vaccine Adverse Event Reporting System (VAERS) in the US. ITP is a rare but known complication of several vaccinations. SARS-CoV-2 vaccine is new, with a novel mechanism of action, and understanding the epidemiology, clinical manifestations, treatment success and natural history of post-vaccination thrombocytopenia is evolving. We report a 74-year-old man who developed refractory thrombocytopenia within one day of receiving the Moderna SARS-CoV-2 vaccine. Several hours after vaccination, he developed significant epistaxis and cutaneous purpura. Severe thrombocytopenia was documented the following day, and he developed extremity weakness and encephalopathy with facial muscle weakness. Over a 14-day period, thrombocytopenia was treated first with high dose dexamethasone, intravenous immunoglobulin, platelet transfusions, rituximab, plasma exchange (for presumed acute inflammatory demyelinating polyneuropathy (AIDP)), and four daily doses of the thrombopoietin receptor agonist (TPO-RA) eltrombopag (Promacta™), without a platelet response. Three days later, he received the TPO-RA romiplostim (Nplate™). Five days later, his platelet count began to rise and by post-vaccination day 25, his platelet count was in the normal range. Thrombocytopenia was refractory to frontline and second-line treatment. The eventual rise in his platelet count suggests that one or both TPO-RAs may have impacted platelet recovery. Possibly, but less likely given the temporality, the drug-induced thrombocytopenia was subsiding. The aggressive use of immunosuppressive treatment may jeopardize the intended purpose of the SARS-CoV-2 vaccine, and earlier use of non-immunosuppressive second-line treatment for vaccine-related severe thrombocytopenia, such as with TPO-RAs, should be considered. While it is imperative to continue the global vaccination program, vigilance to the occurrence of post-vaccination severe thrombocytopenia is warranted.

Clinical overview and practical considerations for optimizing romiplostim therapy in patients with immune thrombocytopenia

The fundamental treatment goal for patients with immune thrombocytopenia (ITP) is reduced or ameliorated bleeding. Although various treatment options exist for the management of ITP, recent advances have led to the approval of three thrombopoietin receptor agonists (TPO-RAs; romiplostim, eltrombopag, and avatrombopag) in the United States and European Union. Current treatment guidelines for ITP indicate that medical therapy is preferred over surgical therapy and support the use of TPO-RAs as early as 3 months after disease onset. More recent data are available on the use of romiplostim in patients who have had ITP for <1 year, and romiplostim is now indicated for the treatment of adults who have not responded adequately to initial treatment, as well as children aged ≥1 year who have had ITP for ≥6 months. Here we review the role of romiplostim in the management of ITP, with a focus on efficacy and safety data, emerging data on early use (beginning within 3 months of disease onset) and treatment-free remission, and practical considerations for optimal management of ITP.

Efficacy and safety of romiplostim in refractory aplastic anaemia: a Phase II/III, multicentre, open-label study

A previous dose-finding study has suggested that romiplostim is effective in patients with refractory aplastic anaemia (AA) and 10 µg/kg once weekly was recommended as a starting dose. In this Phase II/III, multicentre, open-label study, romiplostim was administered subcutaneously at a fixed dose of 10 µg/kg once weekly for 4 weeks (weeks 1-4) followed by weekly doses (5, 10, 15 and 20 µg/kg) titrated by platelet response for up to 52 weeks (weeks 5-52). A total of 31 patients with AA who were refractory to immunosuppressive therapy (IST) and thrombocytopenia (platelet count of ≤30 × 10⁹ /l) were enrolled. The primary efficacy endpoint of the proportion of patients achieving any haematological (platelet, neutrophil and erythrocyte) response at week 27 was 84% [95% confidence interval (CI) 66-95%]. Trilineage response was 39% (95% CI 22-58%) at week 53. The most common treatment-related adverse events (AEs) were headache and muscle spasms (each 13%). All AEs were mild or moderate except for three patients with Grade 3 hepatic AEs; no AEs necessitated romiplostim discontinuation. Two patients developed cytogenetic abnormalities, of whom one returned to normal karyotype at last follow-up. High-dose romiplostim is effective and well tolerated in the treatment of patients with AA refractory to IST.

Dominant negative Gfi1b mutations cause moderate thrombocytopenia and an impaired stress thrombopoiesis associated with mild erythropoietic abnormalities in mice

GFI1B-related thrombocytopenia (GFI1B-RT) is a rare bleeding disorder mainly caused by the presence of truncated GFI1B proteins with dominant-negative properties. The disease is characterized by low platelet counts, the presence of abnormal platelets, a megakaryocytic expansion and mild erythroid defects. However, no animal models faithfully reproducing the GFI1B-RT phenotype observed in patients exist. We had previously generated mice with floxed Gfi1b alleles that can be eliminated by Cre recombinase, but those animals developed a much more severe phenotype than GFI1B-RT patients and were of limited interest in assessing the disease. Using CRISPR/Cas9 technology, we have now established three independent mouse lines that carry mutated Gfi1b alleles producing proteins lacking DNA binding zinc fingers and thereby acting in a dominant negative (DN) manner. Mice heterozygous for these Gfi1b-DN alleles show reduced platelet counts and an expansion of megakaryocytes similar to features of human GFI1B-RT but lacking the distinctively large agranular platelets. In addition, Gfi1b-DN mice exhibit an expansion of erythroid precursors indicative of a mildly abnormal erythropoiesis but without noticeable red blood cell defects. When associated with megakaryocyte-specific ablation of the remaining allele, the Gfi1b-DN alleles triggered erythroid-specific deleterious defects. Gfi1b-DN mice also showed a delayed recovery from platelet depletion, indicating a defect in stress thrombopoiesis. However, injecting Gfi1b-DN mice with romiplostim, a thrombopoietin receptor super agonist, increased platelet numbers even beyond normal levels. Thus, our data support a causal link between DN mutations in GFI1B and thrombocytopenia and suggest that patients with GFI1B-RT could be treated successfully with thrombopoietin agonists.

Augmentation of NK Cell Proliferation and Anti-tumor Immunity by Transgenic Expression of Receptors for EPO or TPO

Many investigational adoptive immunotherapy regimens utilizing natural killer (NK) cells require the administration of interleukin-2 (IL-2) or IL-15, but these cytokines cause serious dose-dependent toxicities. To reduce or preclude the necessity for IL-2 use, we investigated whether genetic engineering of NK cells to express the erythropoietin (EPO) receptor (EPOR) or thrombopoietin (TPO) receptor (c-MPL) could be used as a method to improve NK cell survival and function. Viral transduction of NK-92 cells to express EPOR or c-MPL receptors conveyed signaling via appropriate pathways, protected cells from apoptosis, augmented cellular proliferation, and increased cell cytotoxic function in response to EPO or TPO ligands in vitro. In the presence of TPO, viral transduction of primary human NK cells to express c-MPL enhanced cellular proliferation and increased degranulation and cytokine production toward target cells in vitro. In contrast, transgenic expression of EPOR did not augment the proliferation of primary NK cells. In immunodeficient mice receiving TPO, in vivo persistence of primary human NK cells genetically modified to express c-MPL was higher compared with control NK cells. These data support the concept that genetic manipulation of NK cells to express hematopoietic growth factor receptors could be used as a strategy to augment NK cell proliferation and antitumor immunity.

Bayesian Population Model of the Pharmacokinetics of Venetoclax in Combination with Rituximab in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Results from the Phase III MURANO Study

BACKGROUND

Venetoclax is a selective B-cell lymphoma-2 (BCL-2) inhibitor approved for use as monotherapy or with rituximab in patients with chronic lymphocytic leukemia (CLL). The objectives of the current analysis of observed data from adult patients randomized to venetoclax-rituximab in the phase III MURANO study were to characterize venetoclax pharmacokinetics (PKs) using a Bayesian approach, evaluate whether a previously developed population PK model for venetoclax can describe the PKs of venetoclax when administered with rituximab, and to determine post hoc estimates of PK parameters for the exposure-response analysis.

METHODS

Parameter estimates and uncertainty estimated by a population PK model were used as priors. Additional covariate effects (CLL risk status, geographic region, and 17p deletion [del(17p)] status) were added to the model. The updated model was used to describe venetoclax PKs after repeated dosing in combination with rituximab, and to determine post hoc estimates of PK parameters for exposure-response analysis.

RESULTS

The PK analysis included 600 quantifiable venetoclax PK samples from 182 patients in the MURANO study. Model evaluation using standard diagnostic plots, visual predictive checks, and normalized prediction distribution error plots indicated no model deficiencies. There was no significant relationship between venetoclax apparent clearance (CL/F) and bodyweight, age, sex, mild and moderate hepatic and renal impairment, or coadministration of weak cytochrome P450 3A inhibitors. The chromosomal abnormality del(17p) and CLL risk status had no apparent effect on the PKs of venetoclax. A minimal increase in venetoclax CL/F (approximately 7%) was observed after coadministration with rituximab. CL/F was 30% lower in patients from Central and Eastern Europe (n = 60) or Asia (n = 4) compared with other regions (95% confidence interval [CI] 21-39%). Apparent central volume of distribution was 30% lower (95% CI 22-38%) in females (n = 56) compared with males (n = 126). No clinically significant impact of region or sex was observed on key safety and efficacy outcomes.

CONCLUSIONS

The Bayesian model successfully characterized venetoclax PKs over time and confirmed key covariates affecting PKs in the MURANO study. The model was deemed appropriate for further use in simulations and for generating individual patient PK parameters for subsequent exposure-response evaluation.

Failure Mode and Effects Analysis (FMEA) for Immunogenicity of Therapeutic Proteins

Biotherapeutic drugs made by cell-based systems are revolutionizing the practice of medicine. The next generation of biotherapeutics include recombinant proteins, monoclonal antibodies, viral vector expressed proteins, and cell therapies. Immunogenicity associated adverse events is one of the major risks for these biologics. Accurate and precise measurement of the immunogenicity of biologics is a critical component during all phases of drug development. We have utilized the principles of Failure Mode and Effects Analysis (FMEA) in performing assessment of risk of immunogenicity. The multi-dimensional approach involves: i) listing all the potential risks by likelihood of occurrence and severity as part of quality target product profile. ii) ascribing the causes by identifying the risks at each stage of development. iii) predicting the effects. iv) determining the risk mitigation strategy. v) implementing a monitoring process. vi) developing templates for data collection. vii) timely reporting and. viii) life cycle management. FMEA is a continuous process that works throughout the lifecycle of the product or the process and keeps on getting updated with new insights and knowledge.

Romiplostim for the management of pediatric immune thrombocytopenia: drug development and current practice

Since successful cloning of thrombopoietin (TPO) in 1994, significant advances have been made in the development of recombinant TPO receptor agonists. The US Food and Drug Administration (FDA) has approved 2 agents for use in patients with immune thrombocytopenia (ITP): eltrombopag and romiplostim. Romiplostim is a once-weekly subcutaneous injection that has been shown to increase the platelet count, lessen bleeding, and reduce concurrent medication use in adults with ITP. In December 2018, the US FDA approved romiplostim for use in pediatric patients ≥1 year of age with ITP of >6 months' duration and insufficient response to corticosteroids, immunoglobulins, or splenectomy, based on similarly favorable clinical trial data. In addition, romiplostim is well tolerated, making it an attractive option for the treatment of children. Expansion of off-label romiplostim use is being reported in children for ITP <6 months, neonatal thrombocytopenia, hereditary thrombocytopenias, and chemotherapy- and bone marrow transplant-associated thrombocytopenia. We review here the development of romiplostim with a focus on pediatric use.

Thrombopoietin Receptor Agonists in Children with Immune Thrombocytopenia: A New Therapeutic Era

BACKGROUND AND OBJECTIVE

Immune thrombocytopenia (ITP) is a common bleeding disorder in childhood. The management of ITP in children is controversial, requiring personalized assessment of patients and therapeutic choices. Thrombopoietin receptor agonists (TPO-RAs), eltrombopag and romiplostim, have been shown to be safe and effective for the treatment of pediatric ITP. The aim of our research is to define the role of thrombopoietin receptor agonists in the management of pediatric ITP.

METHODS

This review focuses on the use of TPO-RAs in pediatric ITP, in randomized trials and in clinical routine, highlighting their key role in the management of the disease.

RESULTS

Eltrombopag and romiplostim appear effective treatment options for children with ITP. Several clinical studies have assessed that the use of TPO-RAs increases platelet count, decreases bleeding symptoms and improves health-related quality of life. Moreover, TPO-RAs are well tolerated with minor side effects.

CONCLUSION

Although long term efficacy and safety of TPO-RAs still require further investigations, their use is gradually expanding in the clinical practice of children with ITP.

The role of romiplostim for pediatric patients with immune thrombocytopenia

The thrombopoietin receptor agonists (TPO-RAs) are a class of platelet growth factors used to treat immune thrombocytopenia (ITP) in children and adults. Romiplostim is a peptide TPO-RA approved for over a decade to treat adults with ITP but was just recently US Food and Drug Administration approved to manage ITP in children 1 year of age and older who have had an inadequate response to corticosteroids, intravenous immunoglobulin, or splenectomy. Like the small molecule TPO-RA eltrombopag, romiplostim offers a high clinical response rate in pediatric patients with ITP, but requires use over an extended, and possibly indefinite, duration. This review is a critical appraisal of the role of romiplostim in pediatric ITP, discussing the safety and efficacy of this agent in clinical trials of children and adults and defining the patients most likely to benefit from romiplostim treatment. The treating hematologist is additionally provided guidance with treatment goals, dosing strategies, toxicity management, and indications for discontinuation.

Romiplostim for the Treatment of Immune Thrombocytopenia: Spotlight on Patient Acceptability and Ease of Use

Immune thrombocytopenia (ITP) is an immune-mediated disorder resulting in platelet destruction and subsequent thrombocytopenia. Bleeding symptoms range from mild cutaneous bleeding to life-threatening hemorrhage. Romiplostim, a peptide-antibody fusion product, is a thrombopoietin receptor agonist (TPO-RA) indicated for use in patients with ITP. Romiplostim is US Food and Drug Administration (FDA) approved in children ≥1 year of age with ITP of >6 months' duration who have had an inadequate response to first-line therapies or splenectomy. FDA approval in adults with chronic ITP was expanded in October 2019 to include adults with newly diagnosed (<3 months' duration) and persistent (3-12 months' duration) ITP who demonstrated an inadequate response to first-line therapies, including corticosteroids and immunoglobulins, or splenectomy. The newly published 2019 American Society of Hematology ITP Guidelines place TPO-RAs, including romiplostim, as second-line therapies in both children and adults. Here, we review the use of romiplostim as second-line therapy with a spotlight on health-related quality of life, ease of use, and patient preference.

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.

Romiplostim in patients with refractory aplastic anaemia previously treated with immunosuppressive therapy: a dose-finding and long-term treatment phase 2 trial

BACKGROUND

Aplastic anaemia is a rare, life-threatening condition, characterised by pancytopenia with hypocellular bone marrow. Haematopoietic stem cells and most progenitor cells express thrombopoietin receptor (c-MPL). Romiplostim is a peptibody with c-MPL agonist activity that stimulates endogenous thrombopoietin production and leads to promoting the proliferation and differentiation of megakaryocytes in the bone marrow. In this phase 2 trial we aimed to assess the activity and safety of romiplostim in patients with aplastic anaemia who were previously treated with immunosuppressive therapy.

METHODS

We did an open-label, phase 2 study including a randomised, parallel, dose-finding part followed by an extension part to evaluate long-term treatment at two clinical centres in Seoul, South Korea. Eligible patients were aged 19 years or older, and had aplastic anaemia confirmed by bone marrow and cytogenetic studies and thrombocytopenia (platelet count ≤30 × 10⁹/L), an Eastern Cooperative Oncology Group performance status score of 2 or lower, and were previously treated with immunosuppressive therapy, including at least one course of antithymocyte globulin plus cyclosporin. In the dose-finding part, patients were randomly assigned to fixed dose cohorts (1, 3, 6, or 10 μg/kg) of subcutaneous romiplostim once weekly for 8 weeks, according to a static allocation procedure after stratification by platelet count. In the extension part of the study, patients continued romiplostim titrated every 4 weeks in single steps (1, 3, 6, 10, 13, 16, and 20 μg/kg once weekly), depending on platelet response and safety up to 1 year (weeks 9-52). Patients who had a platelet response during weeks 46-53 continued dose titration in single steps (3, 6, 10, 13, 16, and 20 μg/kg once weekly) for an additional 2 years (weeks 53-156). The primary endpoint was the proportion of patients achieving a platelet response at week 9 (after completion of the dose-finding part). Activity was assessed per-protocol in all patients evaluable for response at week 9 and safety was assessed in all patients who received at least one dose of romiplostim. This trial is registered with ClinicalTrials.gov, NCT02094417.

FINDINGS

Between April 14 and Nov 24, 2014, 35 patients were enrolled and randomly assigned to one of four dose cohorts: romiplostim 1 μg/kg (n=7), 3 μg/kg (n=9), 6 μg/kg (n=9), and 10 μg/kg (n=10). Data cutoff for this final analysis was on April 14, 2018. The median duration of treatment for all patients was 53 weeks (IQR 35-155). Ten (30%) of 33 evaluable patients achieved a platelet response at week 9, including seven (70%) of ten patients in the 10 μg/kg cohort, three (33%) of nine patients in the 6 μg/kg cohort, and no patients in both the 3 μg/kg and 1 μg/kg cohorts. During the extension study, 18 (55%) of 33 evaluable patients had a platelet response during weeks 46-53 and were eligible for continued treatment. Ten (30%) patients maintained a platelet response at 2 and 3 years, of whom nine had an erythroid response and five a neutrophil response, and completed protocol treatment. Treatment-related adverse events occurred in three (9%) of 35 patients, including grade 1 or 2 myalgia, fatigue, and dizziness. 17 (49%) of 35 patients had adverse events of grade 3 or higher; seven (20%) had serious adverse events (one event of febrile neutropenia, cataract, retinal detachment, macular fibrosis, inguinal hernia, appendicitis, cellulitis, tendon injury, and transfusion reaction); and one patient died from sepsis during treatment; none of these events were related to treatment. No patients developed clonal evolution.

INTERPRETATION

Romiplostim seems to be active and has a favourable safety profile in patients with refractory aplastic anaemia. 10 μg/kg once weekly might be used as a recommended starting dose in future studies. These findings warrant further investigation.

FUNDING

Kyowa Hakko Kirin Korea.

A Review of Growth Factor Support in Bloodless Autologous Hematopoietic Stem Cell Transplant

Bloodless autologous hematopoietic cell transplantation is associated with risks of severe bleeding and profound anemia. RBC or platelet transfusions are often used to prevent these hematologic complications. However, in patients such as Jehovah's Witnesses who refuse major blood components, the lack of transfusion support is not an absolute contraindication to an autologous hematopoietic cell transplant. Pennsylvania Hospital performed the world's first bloodless hematopoietic cell transplant more than 15 years ago and has gradually improved its technique with a sizable patient population. Erythropoiesis-stimulating agents were successfully employed as part of their pretransplant regimen to prevent severe anemia. Thrombopoietin agonists' potential role in bloodless transplant is also currently being explored. Although there is limited literature, available reports in combination with physiologic reasoning may support the use of these growth factors to promote transplant success. These agents offer potential benefit and may be of utility in minimizing complications of a bloodless transplant. In this review, we summarize the available literature and offer insight into how we may incorporate growth factors to allow bloodless autologous hematopoietic cell transplantation to be an available option to patients who may otherwise be denied.

Current and emerging treatments for immune thrombocytopenia

Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease. Even though there are many treatments available, some patients remain resistant to multiple treatments. Therefore, it is very important to develop new treatment options. Areas covered: Here, the authors summarize several current and emerging treatments developed for ITP in recent years. They include a summary of their mechanisms of action and clinical trial results. Expert opinion: At present, the first-line treatment of ITP is glucocorticoid and intravenous immunoglobulin (IVIg). Other traditional therapies include splenectomy, thrombopoietin (TPO), rituximab and other immunosuppressive agents. The several emerging treatments developed recently for ITP may change the treatment pattern in the future.

Pharmacodynamics of romiplostim alone and in combination with pegfilgrastim on acute radiation-induced thrombocytopenia and neutropenia in non-human primates

Purpose: Evaluation of the pharmacodynamics (PD) and pharmacokinetics (PK) of romiplostim alone and in combination with pegfilgrastim in a non-human primate (NHP) model of acute radiation syndrome (ARS).Materials and methods: Male and female rhesus macaques were subjected to Cobalt-60 γ irradiation, at a dose of 550 cGy 24 h prior to subcutaneous administration of either romiplostim alone as a single (2.5 or 5.0 mg/kg on Day 1) or repeat dose (5.0 mg/kg on Days 1 and 8), pegfilgrastim alone as a repeat dose (0.3 µg/kg on Day 1 and 8), or a combination of both agents (romiplostim 5.0 mg/kg on Day 1; pegfilgrastim 0.3 µg/kg on Days 1 and 8). Clinical outcome, hematological parameters and PK were assessed throughout the 45 d study period post-irradiation.Results: Administration of romiplostim, pegfilgrastim or the combination of both resulted in significant improvements in hematological parameters, notably prevention of severe thrombocytopenia, compared with irradiated, vehicle control-treated NHPs. The largest hematologic benefit was observed when romiplostim and pegfilgrastim were administered as a combination therapy with much greater effects on both platelet and neutrophil recovery following irradiation compared to single agents alone.Conclusions: These results indicate that romiplostim alone or in combination with pegfilgrastim is effective at improving hematological parameters in an NHP model of ARS. This study supports further study of romiplostim as a medical countermeasure to improve primary hemostasis and survival in ARS.

New Small Molecule Drugs for Thrombocytopenia: Chemical, Pharmacological, and Therapeutic Use Considerations

This review provides details about three small molecules that were recently approved by the FDA for the treatment of thrombocytopenia. The new treatments include lusutrombopag, avatrombopag, and fostamatinib. The first two drugs are orally active thrombopoietin receptor (TPO-R) agonists which are FDA-approved for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure. Fostamatinib is orally active prodrug that, after activation, becomes spleen tyrosine kinase (SYK) inhibitor. Fostamatinib is currently used to treat chronic and refractory immune thrombocytopenia in patients who have had insufficient response to previous treatment. Chemical structures, available dosage forms, recommended dosing, pharmacokinetics, results of toxicity studies in animals, most frequent adverse effects, significant outcomes of the corresponding clinical trials, and their use in specific patient populations are thoroughly described. Described also is a comparative summary of the different aspects of five currently available therapies targeting TPO-R or SYK for the treatment of thrombocytopenia.

Romiplostim (Nplate®) as an effective radiation countermeasure to improve survival and platelet recovery in mice

Purpose: Rapid depletion of white blood cells, platelets, and reticulocytes are hallmarks of hematopoietic injury of acute radiation syndrome (H-ARS) and, if left untreated, can lead to severe health consequences including death. While the granulocyte colony stimulating factors (G-CSF) filgrastim (Neupogen^®), pegfilgrastim (Neulasta^®), and sargramostim (Leukine^®) are approved to increase survival in patients exposed to a myelosuppressive dose of radiation, no medical countermeasure is currently available for treatment of the thrombocytopenia that also results following radiation exposure. Romiplostim (Nplate^®), a thrombopoietin receptor agonist, is the first FDA-approved thrombopoiesis-stimulating protein for the treatment of low platelet (PLT) counts in adults with chronic immune thrombocytopenia. Herein, we present the results of an analysis in mice of romiplostim as a medical countermeasure to improve survival and PLT recovery following acute radiation.Materials and methods: Male and female C57BL/6J mice (11 - 12 weeks of age, n = 21/sex/group) were total body irradiated (TBI) with 6.8 Gy X-rays that reduces 30-day survival to 30% (LD70/30). Vehicle, romiplostim, and/or pegfilgrastim were administered subcutaneously beginning 24 h after TBI for 1-5 days. Evaluation parameters included 30-day survival, pharmacokinetics, and hematology.Results: Full or maximal efficacy with an ∼40% increase in survival was achieved after a single 30 µg/kg dose of romiplostim. No further survival benefit was seen with higher (100 µg/kg) or more frequent dosing (3 or 5 once daily doses at 30 µg/kg) of romiplostim or combined treatment with pegfilgrastim. Pharmacodynamic analysis revealed that the platelet nadir was not as low and recovery was faster in the irradiated mice treated with romiplostim when compared with irradiated control animals (Day 8 versus 10 nadir; Day 22 versus 29 recovery to near baseline). Platelet volume also increased more rapidly after romiplostim injection. Kinetic profiles of other hematology parameters were similar between TBI romiplostim-treated and control mice. Peak serum levels of romiplostim in TBI mice occurred 4 - 24 h (T_max) after injection with a t_1/2 of ∼24 h. Cmax values were at ∼6 ng/ml after 30 µg/kg ± TBI and ∼200 ng/ml after 300 µg/kg. A 10-fold higher romiplostim dose increased the AUC_last values by ∼35-fold.Conclusion: A single injection of romiplostim administered 24 h after TBI is a promising radiation medical countermeasure that dramatically increased survival, with or without pegfilgrastim, and hastened PLT recovery in mice.

Efficacy and safety of thrombopoietin receptor agonists in children with chronic immune thrombocytopenic purpura: meta-analysis

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder presenting with low platelet count <100 × 10⁹/L. The condition affects both adults and children. Thrombopoietin receptor agonists (TPO-RAs) are second-line of therapy that includes Romiplostim and Eltrombopag, which stimulate the production of normally functioning platelets. Although the biological effect of these drugs is well established, there has not been a meta-analysis in children. To estimate the efficacy and safety of Romiplostim and Eltrombopag, we performed a systematic review and meta-analysis in children with chronic ITP. Systematic literature search was conducted in the following database: PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL). Review Manager 5.3 for Windows was used to analyze the data. Five randomized controlled trials with total of 261 pediatric patients from 1-17 years of age were included. The efficacy and safety analysis showed TPO-RA groups were superior over placebo, and there was no difference in adverse event occurrence between TPO-RA (Romiplostim and Eltrombopag) and placebo groups. The efficacy and safety of Eltrombopag did not differ significantly from those of Romiplostim. Both drugs were effective in treatment of children with chronic ITP. Our findings extend the currently available data on ITP treatment and is helpful for pediatric health providers and for the design of future clinical trials.

Pharmacokinetics of protein and peptide conjugates

Protein and peptide conjugates have become an important component of therapeutic and diagnostic medicine. These conjugates are primarily designed to improve pharmacokinetics (PK) of those therapeutic or imaging agents, which do not possess optimal disposition characteristics. In this review we have summarized preclinical and clinical PK of diverse protein and peptide conjugates, and have showcased how different conjugation approaches are used to obtain the desired PK. We have classified the conjugates into peptide conjugates, non-targeted protein conjugates, and targeted protein conjugates, and have highlighted diagnostic and therapeutic applications of these conjugates. In general, peptide conjugates demonstrate very short half-life and rapid renal elimination, and they are mainly designed to achieve high contrast ratio for imaging agents or to deliver therapeutic agents at sites not reachable by bulky or non-targeted proteins. Conjugates made from non-targeted proteins like albumin are designed to increase the half-life of rapidly eliminating therapeutic or imaging agents, and improve their delivery to tissues like solid tumors and inflamed joints. Targeted protein conjugates are mainly developed from antibodies, antibody derivatives, or endogenous proteins, and they are designed to improve the contrast ratio of imaging agents or therapeutic index of therapeutic agents, by enhancing their delivery to the site-of-action.

Feasibility study of a point-of-care positron emission tomography system with interactive imaging capability

PURPOSE

We investigated the feasibility of a novel positron emission tomography (PET) system that provides near real-time feedback to an operator who can interactively scan a patient to optimize image quality. The system should be compact and mobile to support point-of-care (POC) molecular imaging applications. In this study, we present the key technologies required and discuss the potential benefits of such new capability.

METHODS

The core of this novel PET technology includes trackable PET detectors and a fully three-dimensional, fast image reconstruction engine implemented on multiple graphics processing units (GPUs) to support dynamically changing geometry by calculating the system matrix on-the-fly using a tube-of-response approach. With near real-time image reconstruction capability, a POC-PET system may comprise a maneuverable front PET detector and a second detector panel which can be stationary or moved synchronously with the front detector such that both panels face the region-of-interest (ROI) with the detector trajectory contoured around a patient's body. We built a proof-of-concept prototype using two planar detectors each consisting of a photomultiplier tube (PMT) optically coupled to an array of 48 × 48 lutetium-yttrium oxyorthosilicate (LYSO) crystals (1.0 × 1.0 × 10.0 mm³ each). Only 38 × 38 crystals in each arrays can be clearly re-solved and used for coincidence detection. One detector was mounted to a robotic arm which can position it at arbitrary locations, and the other detector was mounted on a rotational stage. A cylindrical phantom (102 mm in diameter, 150 mm long) with nine spherical lesions (8:1 tumor-to-background activity concentration ratio) was imaged from 27 sampling angles. List-mode events were reconstructed to form images without or with time-of-flight (TOF) information. We conducted two Monte Carlo simulations using two POC-PET systems. The first one uses the same phantom and detector setup as our experiment, with the detector coincidence re-solving time (CRT) ranging from 100 to 700 ps full-width-at-half-maximum (FWHM). The second study simulates a body-size phantom (316 × 228 × 160 mm³ ) imaged by a larger POC-PET system that has 4 × 6 modules (32 × 32 LYSO crystals/module, four in axial and six in transaxial directions) in the front panel and 3 × 8 modules (16 × 16 LYSO crystals/module, three in axial and eight in transaxial directions) in the back panel. We also evaluated an interactive scanning strategy by progressively increasing the number of data sets used for image reconstruction. The updated images were analyzed based on the number of data sets and the detector CRT.

RESULTS

The proof-of-concept prototype re-solves most of the spherical lesions despite a limited number of coincidence events and incomplete sampling. TOF information reduces artifacts in the reconstructed images. Systems with better timing resolution exhibit improved image quality and reduced artifacts. We observed a reconstruction speed of 0.96 × 10⁶ events/s/iteration for 600 × 600 × 224 voxel rectilinear space using four GPUs. A POC-PET system with significantly higher sensitivity can interactively image a body-size object from four angles in less than 7 min.

CONCLUSIONS

We have developed GPU-based fast image reconstruction capability to support a PET system with arbitrary and dynamically changing geometry. Using TOF PET detectors, we demonstrated the feasibility of a PET system that can provide timely visual feedback to an operator who can scan a patient interactively to support POC imaging applications.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.