Assessment of romiplostim immunogenicity in adult patients in clinical trials and in a global postmarketing registry.

Antibodies to first-generation recombinant thrombopoietin (TPO) neutralized endogenous TPO and caused thrombocytopenia in some healthy subjects and chemotherapy patients. The second-generation TPO receptor agonist romiplostim, having no sequence homology to TPO, was developed to avoid immunogenicity. This analysis examined development of binding and neutralising antibodies to romiplostim or TPO among adults with immune thrombocytopenia (ITP) in 13 clinical trials and a global postmarketing registry. 60/961 (6·2%) patients from clinical trials developed anti-romiplostim-binding antibodies post-baseline. The first positive binding antibody was detected 14 weeks (median) after starting romiplostim, at median romiplostim dose of 2 µg/kg and median platelet count of 29.5 × 109 /l; most subjects had ≥98·5% of platelet assessments showing response. Neutralising antibodies to romiplostim developed in 0·4% of patients, but were unrelated to romiplostim dose and did not affect platelet count. Thirty-three patients (3·4%) developed anti-TPO-binding antibodies; none developed anti-TPO-neutralising antibodies. In the global postmarketing registry, 9/184 (4·9%) patients with spontaneously submitted samples had binding antibodies. One patient with loss of response had anti-romiplostim-neutralising antibodies (negative at follow-up). Collectively, anti-romiplostim-binding antibodies developed infrequently. In the few patients who developed neutralising antibodies to romiplostim, there was no cross-reactivity with TPO and no associated loss of platelet response.

Assessment of the underlying causes of the immune thrombocytopenia: Ten years experience.

OBJECTIVE: Immune thrombocytopenia (ITP) is an immune haematologic disorder causing platelet destruction mediated by anti-platelet antibodies. In this study we aimed to evaluate the clinical and laboratory variables of ITP patients in southeast of Turkey. METHODS: In this retrospective study 167 ITP patients between 2005 and 2015 were evaluated. All patients were screened for immunological parameters including ANA (antinuclear antibodies), anti dsDNA (anti-double-stranded-DNA), ACA(anti-cardiolipin) IgM and IgG, LA (lupus anticoagulants). All patients were screened for Helicobacter pylori, HBsAg (Hepatitis B surface antigen), anti-HCV (hepatitis C virus antibody), and anti-HIV ½ (HIV antibody) and brucellosis.. RESULTS: Among the patients, 50 (29.9%) patients were male, 117 (70.1%) were female. The age range of patients was 18-86 (mean 38.16±14). In 56 patients (33.5%) splenectomy was performed. 36 patients (21.6%) were positive for ANA, 5 (3%) were positive for anti dsDNA, 14 (8.4%) for ACA Ig G, and 14 (8.4%) patients for ACA IgM. LA was tested in 165 patients and 30 (18%) patients were positive for LA. Microbiologic evaluation was as follows: 16 patients (9.6%) were positive for HbsAg, 109 (65.3%) positive for Anti-HBs, 5 positive for anti-HCV (3%), 56 (33.5%) patients were positive for Helicobacter pylori antigen, 5 (2.9%) for Brucella and one patient was positive for anti-HIV ½. CONCLUSIONS: Immune thrombocytopenia patients have to be evaluated according to their demographic characteristics and laboratory results. Secondary causes of ITP were HIV, HCV, Helicobacter pylori, brucellosis, tuberculosis, and autoimmune diseases in our region. Management of ITP patients can change in different regions.

Performance characteristics of an automated latex immunoturbidimetric assay [HemosIL® HIT-Ab(PF4-H)] for the diagnosis of immune heparin-induced thrombocytopenia.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by platelet-activating anti-PF4/heparin antibodies. Given time-sensitive treatment considerations, a rapid and accurate laboratory test for HIT antibodies is needed. AIMS: To determine operating characteristics for the HemosIL® HIT-Ab(PF4/H), a rapid, on-demand, fully-automated, latex immunoturbidimetric assay (LIA), for diagnosis of HIT. METHODS: We evaluated LIA sensitivity, specificity, negative (NPV) and positive predictive value (PPV), negative (LR-) and positive likelihood ratio (LR+), using citrated-plasma from 429 patients (prospective cohort study of 4Ts scoring; HIT, n=31), and from consecutive HIT patients (n=125), using reference standard serotonin-release assay (SRA). Comparators included two PF4-dependent enzyme-immunoassays (EIAs). We used stratum-specific likelihood ratios (SSLRs) to determine how differing magnitudes of LIA-positivity influenced post-test probability of HIT. RESULTS: LIA operating characteristics were: sensitivity=97.4% (152/156); specificity=94.0% (374/398); PPV=55.6% (30/54); and NPV=99.7% (374/375). At manufacturers' cutoffs, LIA specificity and PPV were superior to the EIAs. Although a negative LIA pointed strongly against HIT (LR-, 0.034), the post-test probability was ~2% with high 4Ts score. The LIA's LR+ was high (16.0), with SSLRs rising substantially with greater LIA-positivity: 5.7 (1.0-4.9U/mL), 31 (5.0-15.9U/mL), and 128 (≥16U/mL). A LIA-positive result (at 1.0 cutoff) indicated at least 24% HIT probability (low 4Ts score), rising to 90% with high 4Ts score. CONCLUSIONS: Although approximately 1 in 40 SRA-positive patients tested LIA-negative, the LIA's high NPV and PPV indicate that this rapid assay is useful for the diagnostic evaluation of HIT, including in low pre-test situations.

Assessment of Th17/Treg cells and Th cytokines in an improved immune thrombocytopenia mouse model.

OBJECTIVES: The improved passive immune thrombocytopenia (ITP) mouse model has been extensively utilized for the study of ITP. However, how closely this model matches the human inflammation state and immune background is unclear. Our study aimed to explore the profile of Th cytokines and Th17/Treg cells in the model. METHODS: We induced the ITP mouse model by dose-escalation injection of MWReg30. The serum levels of cytokines (IFN-γ, IL-2, IL-4, IL-10, IL-17A, and TGF-ß1) were measured by enzyme-linked immunosorbent assay and the frequency of Th17 and Treg cells was measured by flow cytometry. The mRNA expression of Foxp3 and RORrt was measured by real-time PCR. RESULTS: The serum levels of cytokines IFN-γ, TGF-ß1, IL-4, and IL-10 were significantly lower in ITP mice. The secretion of serum proinflammatory cytokines IL-2 and IL-17A and the percentage of Th17 cells showed no statistically significant increase. In ITP mice the frequency of Treg cells and mRNA expression of Foxp3 was significantly lower in splenocytes. CONCLUSION: Our data suggest that the improved passive ITP mouse model does not mimic the autoimmune inflammatory process of human ITP. Compared with human ITP, this model has a similar change in frequency of Treg cells, which may directly or indirectly result from antibody-mediated platelet destruction due to attenuated release of TGF-ß.

Management of immune thrombocytopenic purpura in children: potential role of novel agents.

The treatment of immune thrombocytopenic purpura (ITP) in children is controversial, requiring individualized assessment of the patient and consideration of treatment options. If the platelet count is >10 000/µL and the patient is asymptomatic, a 'watch and wait' strategy is appropriate since most children with ITP will recover completely without pharmacotherapy. If therapy is indicated because of bleeding or a platelet count <10 000/µL, then treatment with glucocorticoids, intravenous immunoglobulin (IVIg), or anti-D are possible initial choices. Glucocorticoid treatment is the least expensive and is our usual first choice of therapy. Its use assumes that the blood counts and blood film have been evaluated to ensure the absence of evidence of alternative diagnoses, such as thrombotic thrombocytopenic purpura or incipient acute leukemia. IVIg is expensive and often causes severe headache, nausea and vomiting, and requires hospitalization at our institution. Anti-D therapy is also expensive and can only be used in patients who are Rhesus D positive. These therapies, even if only transiently effective, can be repeated if necessary. Children usually recover from newly diagnosed ITP, with or without multiple courses of medical therapy. If the disease becomes 'persistent' with severe thrombocytopenia and/or bleeding, and is no longer responsive to the three first-line therapies, the next approach includes the use of thrombopoietin receptor agonists or rituximab. When the disease persists for more than 1 year, it is considered chronic, and, if symptomatic, it may become necessary to consider third-line therapies, including splenectomy, alternative immunosuppressive agents, or combination or investigative chemoimmunotherapy. This review considers the indications, mechanism of action, and effectiveness of the traditional and novel treatment options for patients with ITP.

[A prospective assessment of the diagnostic value of MAIPA test in idiopathic thrombocytopenic purpura].

OBJECTIVE: To evaluate the clinical significance of MAIPA test in diagnosis of idiopathic thrombocytopenic purpura (ITP) and in the differential diagnosis of antoimmune thrombocytopenias from nonimmune thrombocytopenias. METHODS: A total of 321 thrombocytopenic patients (118 males, 203 females) from 14 centers were studied. A modified monoclonal antibody immobilization of platelet antigen (MAIPA) method was used to detect the platelet glycoprotein-specific autoantibodies (anti-GP IIb/IIIa, anti-GPIb/IX) to double-blindly evaluate its sensitivity and specificity for the diagnosis of ITP and to investigate the impact of the antibodies on platelet count. RESULTS: The results showed that for the diagnosis of ITP, anti-GPIIb/IIIa, anti-GPIb/IX and both of them had the sensitivity of 39.75%, 32.64% and 55.23%; the specificity of 97.56%, 93.94% and 92.68%; the positive predictive value of 97.94%, 93.98% and 95.65%; the negative predictive value of 35.71%, 32.35% and 41.53%; and the total efficiency of 54.51%, 48.29% and 64.80%, respectively. The positivity of the autoantibodies in immune thrombocytopenias was incredibly higher than that in nonimmune thrombocytopenias. The platelet counts in the immune thrombocytopenias with autoantibody positivities were significantly lower than those without the autoantibodies. The platelet counts were negatively correlated with the concentration of the autoantibodies. The levels of anti-GPIIb/IIIa or anti-GPIb/IX or both of them dropped or disappeared in patients being responsive to steroid therapy. CONCLUSION: MAIPA assay is proved to be of great value for the diagnosis of ITP and for differential diagnosis of immune thrombocytopenias from nonimmune thrombocytopenias.

Assessment of immunogenicity of romiplostim in clinical studies with ITP subjects.

Romiplostim is an Fc-peptide fusion protein that activates intracellular transcriptional pathways via the thrombopoietin (TPO) receptor leading to increased platelet production. Romiplostim has been engineered to have no amino acid sequence homology to endogenous TPO. Recombinant protein therapeutics can be at a risk of development of an antibody response that can impact efficacy and safety. Hence, a strategy to detect potential antibody formation to the drug and to related endogenous molecules can be useful. The immunogenicity assessment strategy involved both the detection and characterization of binding and neutralizing antibodies. The method for detection was based on a surface plasmon resonance biosensor platform using the Biacore 3000. Samples that tested positive for binding antibodies in the Biacore immunoassay were then tested in a neutralization assay. Serum samples from 225 subjects with immune thrombocytopenic purpura (ITP) dosed with romiplostim and 45 ITP subjects dosed with placebo were tested for romiplostim and TPO antibodies. Prior to romiplostim treatment, 17 subjects (7%) tested romiplostim antibody positive and 12 subjects (5%) tested TPO antibody positive for pre-existing binding antibodies. After romiplostim exposure, 11% of the subjects exhibited binding antibodies against romiplostim and 5% of the subjects with ITP showed binding antibodies against TPO. The antibodies against romiplostim did not cross-react with TPO and vice versa. No cases of anti-TPO neutralizing antibodies were detected in romiplostim-treated subjects. The incidence of anti-romiplostim neutralizing antibodies to romiplostim was 0.4% (one subject); this subject tested negative at the time of follow-up 4 months later. No impact on platelet profiles were apparent in subjects that had antibodies to romiplostim to date. In summary, administration of romiplostim in ITP subjects resulted in the development of a binding antibody response against romiplostim and TPO ligand. One subject developed a neutralizing antibody response to romiplostim that impacted the platelet counts of this subject. No neutralizing antibodies to endogenous TPO were observed.

Romiplostim for the treatment of chronic immune or idiopathic thrombocytopenic purpura: a single technology appraisal.

This paper presents a summary of the evidence review group (ERG) report into the clinical and cost-effectiveness of romiplostim for the treatment of adults with chronic immune or idiopathic thrombocytopenic purpura (ITP) based upon a review of the manufacturer's submission to the National Institute for Health and Clinical Excellence (NICE) as part of the single technology appraisal (STA) process. The submission's evidence came from two relatively high-quality randomised controlled trials (RCTs). The ERG found no evidence that any important data were missed or that data extraction was inaccurate. In both RCTs more patients in the romiplostim than in the placebo group achieved a durable platelet response [non-splenectomised patients: romiplostim 25/41 (61%), placebo 1/21 (5%), odds ratio (OR) 24.45, 95% confidence interval (CI) 3.34 to 179.18; splenectomised patients: romiplostim 16/42 (38%), placebo 0/21 (0%), OR 8.5 (95% CI 1.15 to 372)] and an overall platelet response [non-splenectomised patients: romiplostim 36/41 (88%), placebo 3/21 (14%), OR 34.74, 95% CI 7.77 to 155.38; splenectomised patients: romiplostim 33/42 (79%), placebo 0/21 (0%), OR 16.6 (95% CI 2.37 to 706]. The difference in mean period with a platelet response was 13.9 weeks (95% CI 10.5 to 17.4) in favour of romiplostim in the RCT of non-splectomised patients and 12.1 weeks (95% CI 8.7 to 15.6) in favour of romiplostim in the RCT of splectomised patients. The manufacturer's economic model evaluated the cost-effectiveness of romiplostim compared with standard care. The ERG had concerns about the way the decision problem was addressed in the economic model and about the non-adjustment of findings for confounding factors. In non-splenectomised patients, using romiplostim as a first option treatment, the base-case incremental cost-effectiveness ratio (ICER) was 14,840 pounds per quality-adjusted life-year (QALY). In splenectomised patients the ICER was 14,655 pounds per QALY. Additional sensitivity analyses performed by the ERG identified two issues of importance: whether individuals entered the model on watch and rescue or on active therapy in the comparator arm (ICER 21,674 pounds per QALY for non-splenectomised patients, 29,771 pounds per QALY for splenectomised patients); whether it was assumed that any unused medicine would be wasted. Combining all of the separate sensitivity analyses, and assuming that watch and rescue was not the first-line treatment, increased the ICERs further (non-splenectomised 37,290 pounds per QALY; splenectomised 131,017 pounds per QALY). In conclusion, the manufacturer's submission and additional work conducted by the ERG suggest that romiplostim has short-term efficacy for the treatment of ITP, but there is no robust evidence on long-term effectiveness or cost-effectiveness of romiplostim compared with relevant comparators.

[Treatment of chronic immune thrombocytopenic purpura. Looking for something better. Review]. / Tratamiento de la púrpura trombocitopénica inmune crónica. Buscando algo mejor. Revisión.

Chronic Immune Thrombocytopenic Purpura (cITP) has become a field of multiple therapeutic assays. More than 20 types of treatment have been developed to obtain a favorable and prolonged platelet response. The treatment of cITP is oriented to inhibit the antiplatelet antibodies production by interference with the macrophage of the reticulum endothelial system and a blockade of the antigenic response with a decrease in the amplification of the immunological response. Steroids of the glucocorticoids type and splenectomy constitute the first line of treatment. Failure of these treatments leads to the use of second line drugs such as non steroid immuno-supressors and the immunoglobulins type IgG and anti-D. Therapeutic assays with others immunomodulators have been reported. The introduction of new drugs destined to increase the megakaryocytic bone marrow platelet production, has opened a new way to treat the cITP. However, the splenectomy remains as the simplest, safest and most effective treatment in cITP. The principal criteria does not have to be focused on obtaining a normal platelet count, but to reach safe hemostatic levels in absence of hemorrhage, for a prolonged time. On the other hand, despite the persistence of thrombocytopenia, the hematologist can choose to maintain the patient with no treatment and with only a strict clinical observation. It is obvious that the cost-benefit from the different treatments is inclined towards those of lower cost and minimal secondary effects.

A single-institution, 20-year prospective experience with an affordable Fc-receptor blockade method to treat patients with chronic, refractory autoimmune thrombocytopenic purpura.

In a 20-year period in a single institution, 34 patients with chronic, refractory autoimmune thrombocytopenic purpura were prospectively treated with ex vivo anti-D opsonized autologous red blood cells. All patients had received previous treatment with steroids and/or immunosuppressive agents, and 11 had been splenectomized. Twenty one patients had an increase in the platelet count; in five cases, the increase was more than 50 x 10(9)/L platelets and in 16 the increase was more than 100 x 10(9)/L platelets. Early responses were observed in 20 patients and late responses in seven, whereas seven patients (20%) did not respond at all. Nine of the 20 individuals who achieved an ER had a subsequent drop in the platelet count; however, only three had a drop below 50 x 10(9)/L. When last censored, of the 34 patients, 24 (70%) had a platelet count above 50 x 10(9)/L. The 84-month thrombocytopenia-free (over 50 x 10(9)/L platelets) status of the whole group is 70%, whereas the 84-month complete remission (over 100 x 10(9)/L platelets) status of the whole group is 50%. It is concluded that the use of ex vivo anti-D opsonized red blood cells may represent another, substantially cheaper treatment of patients with chronic, refractory, autoimmune thrombocytopenic purpura.

Prospective epidemiologic study of the outcome and cost-effectiveness of antenatal screening to detect neonatal alloimmune thrombocytopenia due to anti-HPA-1a.

BACKGROUND: To assess the value of antenatal screening to detect neonatal alloimmune thrombocytopenia (NAIT) due to anti-HPA-1a, a prospective study was carried out to quantify the potential clinical benefits and determine whether screening would be cost-effective. STUDY DESIGN AND METHODS: An observational prospective controlled study was carried out on 26,506 pregnant women over 2 years. HPA-1a phenotyping was performed in the first trimester and women confirmed HPA-1a-negative were tested for anti-HPA-1a during pregnancy, at delivery, and 10 to 14 days after birth. Babies of HPA-1a-negative women were tested at delivery for thrombocytopenia and examined for signs of bleeding. Economic evaluation was undertaken on the basis of the data collected during the study. RESULTS: Twenty-five of 318 women (7.9%) had anti-HPA-1a detected for the first time. Eight women (43 per 100,000) gave birth to babies with NAIT, and 5 (27 per 100,000) had severe thrombocytopenia. Three babies had mild signs of bleeding, and no cases of intracranial hemorrhage (ICH) or fetal loss were detected. It is estimated that it would cost 60,596 pounds (98,771 US dollars) to detect a case of severe NAIT, where anti-HPA-1a has been identified for the first time, and 1,151,323 pounds (1,876,656 US dollars) to prevent a case of ICH, assuming that detection allowed successful intervention. CONCLUSIONS: Our data suggest that severe HPA-1a NAIT is underdiagnosed in the absence of routine antenatal screening. Serious bleeding complications and ICH, however, occur less frequently in first cases of NAIT than suspected from the literature, and the costs of screening and possible intervention must be balanced against the procedural risks.

[Intravenous immunoglobulins and autoimmune thrombopenic purpura]. / Immunoglobulines intraveineuses et purpura thrombopénique auto-immun.

OBJECTIVE: To determine the usefulness of intravenous immunoglobulin in the treatment of autoimmune thrombocytopenic purpura (AITP). RESULTS: IVIg infusion is an important agent in managing AITP because most patients experienced a rapid increased platelet count. Its precise place in the management of these patients is however controversial, particularly on account of its high cost and transient effect. It is indicated in the severe form of the disease or before surgery in corticoresistant patients. PERSPECTIVE: Prospective studied are mandatory to compare the efficacy of IVIg and high dose corticosteroids in this indication.

Experience with protein A-immunoadsorption in treatment-resistant adult immune thrombocytopenic purpura.

Extracorporeal immunoadsorption of plasma to remove IgG and circulating immune complexes (CIC) was evaluated as a therapy for adults with treatment-resistant immune thrombocytopenic purpura (ITP). Seventy-two patients with initial platelet counts less than 50,000/microL who had failed at least two other therapies were studied. They received an average of six treatments of 0.25 to 2.0 L plasma per procedure over a 2- to 3-week period using columns of staphylococcal protein A-silica (PROSORBA immunoadsorption treatment columns; IMRE Corp, Seattle, WA). The treatments caused an acute increase in the platelet count to greater than 100,000/microL in 18 patients and to 50,000 to 100,000/microL in 15 patients. The median time to response was 2 weeks. Responses were transient (less than 1 month duration) in seven of those patients (10%), but no additional relapses were reported over a follow-up period of up to 26 months (mean of 8 months). Clinical responses were associated with significant decreases in specific serum platelet autoantibodies (including anti-glycoprotein IIb/IIIa), platelet-associated Ig, and CIC. Thirty percent of treatments were associated with transient mild to moderate side effects usually presenting as a hypersensitivity-type reaction. Continued administration of failed therapies for ITP, which always included low-dose corticosteroids (less than or equal to 30 mg/d), had no demonstrable influence on the effectiveness of immunoadsorption treatment but did depress the incidence and severity of side effects. The degree of effectiveness of protein A immunoadsorption therapy in patients with treatment-resistant ITP is promising and further controlled studies in this patient population are warranted.