Is anti-D immunoglobulin still a frontline treatment option for immune thrombocytopenia?

Antagonism of the Platelet-Activating Factor Pathway Mitigates Inflammatory Adverse Events Driven by Anti-erythrocyte Antibody Therapy in Mice

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by low platelet counts primarily due to antiplatelet autoantibodies. Anti-D is a donor-derived polyclonal Ab against the rhesus D Ag on erythrocytes used to treat ITP. Unfortunately, adverse inflammatory/hypersensitivity reactions and a Food and Drug Administration-issued black box warning have limited its clinical use. This underscores the imperative to understand the inflammatory pathway associated with anti-erythrocyte Ab-based therapies. TER119 is an erythrocyte-specific Ab with anti-D-like therapeutic activity in murine ITP, while also exhibiting a distinct inflammatory signature involving production of CCL2, CCL5, and CXCL9 but not IFN-γ. Therefore, TER119 has been used to elucidate the potential mechanism underlying the adverse inflammatory activity associated with anti-erythrocyte Ab therapy in murine ITP. Prior work has demonstrated that TER119 administration is associated with a dramatic decrease in body temperature and inflammatory cytokine/chemokine production. The work presented in the current study demonstrates that inhibiting the highly inflammatory platelet-activating factor (PAF) pathway with PAF receptor antagonists prevents TER119-driven changes in body temperature and inhibits the production of the CCL2, CCL5, and CXCL9 inflammatory cytokines in CD-1 mice. Phagocytic cells and a functional TER119 Fc region were found to be necessary for TER119-induced body temperature changes and increases in CXCL9 and CCL2. Taken together, this work reveals the novel requirement of the PAF pathway in causing adverse inflammatory activity associated with anti-erythrocyte Ab therapy in a murine model and provides a strategy of mitigating these potential reactions without altering therapeutic activity.

Real-world experience of anti-D immunoglobulin in immune thrombocytopenia

In developing countries, anti-D has been used in immune thrombocytopenia (ITP) as a cheaper alternative to human immunoglobulin. We aim to analyze the response and safety profile of anti-D in patients with severe ITP. A retrospective study was conducted at a tertiary care hospital in Northern India. Patients received a single intravenous infusion of 75 μg/kg anti-D. In total, 36 patients (20 females) were included in this study. The median duration from ITP diagnosis to anti-D therapy was 235 days (range 1-1613 days). Four (11.1%) patients received anti-D as an upfront treatment. The patients' platelet counts rose significantly by the end of day three and continued to be significantly high until day 30 of receiving anti-D (p ≤ 0.001). The overall response rate (ORR) by day seven was 88.89%. There was no effect of age, sex, duration of disease, prior therapy, and platelet count on the ORR. Patients were followed up for a median duration of 52 days (longest follow-up: 3080 days). Six (6/36, 16.67%) patients continued to be in remission till the last follow-up. The hemoglobin fall was statistically significant on day three and day seven (p < 0.001 and p = 0.001) and got normalized by day 30. We observed equally good ORR in mixed populations and different phases of ITP along with long-term sustained response. The study demonstrates a quick and high response rate along with good safety profile to anti-D in all forms of ITP.

Immune Thrombocytopenia in Children: Consensus and Controversies

Newly diagnosed immune thrombocytopenia (ITP) is a relatively common disorder of childhood that does not require an exhaustive laboratory workup for diagnosis. A history and physical exam with a review of the peripheral smear are crucial for excluding secondary causes of thrombocytopenia. Several guidelines have been published to guide physicians in the management of ITP. However, the decision for treatment can be arduous. The management strategy should not be focussed on the platelet count but the severity of bleeding symptoms. Agents for treating acute ITP, including corticosteroids, immunoglobulin and anti-D immunoglobulin, do not seem to have a significant impact on the natural history of the disease. The majority of children with ITP do not need therapy and have a spontaneous resolution of the disease. Some children can develop chronic ITP that is not commonly life-threatening but can lead to impaired quality of life. Traditional therapies such as rituximab and splenectomy for chronic ITP are not without significant adverse effects. Thrombopoietin receptor agonists are newer agents for the treatment of chronic ITP and hold promise, however, their cost currently precludes use in most of the patients in low-middle-income countries. This review compares and contrasts the specific treatments available for the treatment of ITP to help the reader make a balanced choice. This review, based on a series of case examples, will help physicians in making decisions about choosing a practical management strategy for patients with newly diagnosed as well as chronic ITP.

The third international standard for anti-D immunoglobulin: international collaborative study to evaluate candidate preparations

BACKGROUND AND OBJECTIVES

The purpose of the study was to evaluate a lyophilized anti-D immunoglobulin preparation to serve as a replacement WHO International Standard for the calibration of potency assays of anti-D immunoglobulin products. Such products are used to prevent haemolytic disease of the foetus and newborn due to maternal alloanti-D.

MATERIALS AND METHODS

The candidate 3rd International Standard for anti-D immunoglobulin (16/332) was evaluated and calibrated against the 2nd International Standard for anti-D immunoglobulin (01/572), along with a coded duplicate, a second candidate preparation (16/278) and a comparability sample (16/272) in an international collaborative study. Twenty of 21 laboratories in 15 countries performed one or more of the three European Pharmacopoeia reference methods.

RESULTS

The overall geometric mean potency (from all methods) of the candidate 3rd International Standard, 16/332, was 296·6 IU/ampoule, with inter-laboratory variability, expressed as % GCV, of 4·7%. SE-HPLC of the immunoglobulin preparations demonstrated combined monomeric and dimeric IgG peak areas of >95% for all samples. Accelerated stability studies have shown both 16/332 and 16/278 to be very stable for long-term storage at -20°C.

CONCLUSIONS

Preparation 16/332 was established by the World Health Organisation Expert Committee on Biological Standardization as the 3rd International Standard for anti-D immunoglobulin with an assigned potency of 297 IU/ampoule.

Patterns of care and burden of chronic idiopathic thrombocytopenic purpura in Brazil

AIMS

Although several therapeutic options are available for chronic immune thrombocytopenic purpura (cITP), little is known about the treatment of cITP in Brazil.

MATERIALS AND METHODS

A multi-center, retrospective chart review, observational study was designed to describe the treatment patterns, clinical burden, resources use, and associated costs for adult patients diagnosed with cITP and treated in public and private institutions in Brazil. Patient charts were screened in reverse chronological order based on their last visit post January 1, 2012. (All costs were calculated using 1.00 USD = 3.9571 BRL, from February 2016.) Results: Of 340 patient charts screened, 50 patients were eligible for inclusion in the study. Single-drug therapy (prednisone, dexamethasone, or dapsone) was the most commonly used treatment, followed by combination therapies (azathioprine + prednisone, azathioprine + prednisone + danazol, and prednisone + dapsone). Splenectomy was performed in 22% of patients after at least first-line treatment. Platelet count and number of bleeding episodes at diagnosis were 31,561.1/mm³ (SD = ±26,396.1) and 40 episodes, respectively; in first-line, 92,631.1/mm³ (SD = ±79,955.3) and 19 episodes, respectively; in second-line, 96,950.0/mm³ (SD = ±76,476.4) and 17 episodes, respectively. Private system patients had a higher median cost compared to public system patients (USD 17.49/month, range = 0-2,020.77 vs USD 9.51/month, range = 0-192.64, respectively).

LIMITATIONS

This study does not allow conclusions for causal explanations due to the cohort study design, and treatment patterns represent only the practices of physicians who have agreed to participate in the study.

CONCLUSIONS

The data indicate that available therapeutic strategies for second- and third-line therapies appear to be limited.

Bleeding complications in immune thrombocytopenia

Bleeding manifestations in patients with immune thrombocytopenia (ITP) range from mild skin bruises to life-threatening intracranial hemorrhage (ICH). Severe bleeding is distinctly uncommon when the platelet count is >30 × 109/L and usually only occurs when the platelet count falls <10 × 109/L. Based on estimates from clinical studies, ITP registries and administrative databases, the frequency of ICH in patients with ITP is ∼0.5% in children and 1.5% in adults. Estimates of severe (non-ICH) bleeding are difficult to obtain because of the lack of standardized case definitions; the lack of a universally accepted, ITP-specific bleeding assessment tool; and the omission of reporting bleeding outcomes in many clinical studies. In practice, the presence of bleeding should dictate whether or not treatment is needed because many patients, especially children, can be safely managed with observation alone. Guiding principles for the management of ITP, based on the bleeding risk are: (1) Decide when treatment is needed and when it can safely be withheld; (2) for patients with chronic ITP, use the least toxic treatment at the lowest dose; (3) emergency treatment of severe thrombocytopenia-associated bleeding requires combination therapy; and (4) early aggressive therapy may result in durable platelet count responses.

Management of hypersensitivity reactions to anti-D immunoglobulin preparations

RhD immunoglobulin G (anti-D) administered to pregnant Rh(-) women prevents Rh isoimmunization. Its use has significantly reduced the incidence of haemolytic disease of the foetus and newborn previously responsible for one death in every 2200 births. In pregnancy, acute drug-induced hypersensitivity reactions including anaphylaxis can have serious deleterious effects on the mother and foetus/neonate. Women can be erroneously labelled as drug allergic as the investigation of hypersensitivity reactions in pregnancy is complex and drug challenges are usually contraindicated. We present three cases of suspected anti-D hypersensitivity clinically presenting as anaphylaxis and delayed transfusion-related reaction. We also propose a new algorithm for the investigations of such reaction. It relies on detailed history, cautious interpretation of skin tests, foetal Rh genotyping from maternal blood and, in some cases, anti-D challenges. This is not to deprive women of anti-D which might put their future pregnancies at risk.