Recent advances in the treatment of childhood immune thrombocytopenic purpura

Using the K/BxN mouse model of endogenous, chronic, rheumatoid arthritis for the evaluation of potential immunoglobulin-based therapeutic agents, including IVIg and Fc-μTP-L309C, a recombinant IgG1 Fc hexamer

BACKGROUND

High-dose intravenous immunoglobulin (IVIg), and more recently, subcutaneously-delivered Ig (SCIg), are used to treat a variety of autoimmune diseases; however, there are challenges associated with product production, availability, access and efficacy. These challenges have provided incentives to develop a human recombinant Fc as a more potent alternative to IVIg and SCIg for the treatment of autoimmune diseases. Recently, a recombinant human IgG1 Fc hexamer (Fc-μTP-L309C) was shown to be more efficacious than IVIg in a variety of autoimmune mouse models. We have now examined its efficacy compared to IVIg and SCIg in the K/BxN mouse model of endogenous, chronic rheumatoid arthritis (RA).

RESULT

Using the serum-transfer K/BxN model and the endogenous autoimmune model, amelioration of the arthritis was achieved. Effective treatment required high and frequent doses of IVIg, SCIg and Fc-μTP-L309C. However, Fc-μTP-L309C was efficacious at 10-fold lower doses that IVIg/SCIg. Also, arthritis could be prevented when Fc-μTP-L309C was given prior to onset of the arthritis in both the endogenous model and in the serum transfer model.

CONCLUSIONS

Our results show that Fc-μTP-L309C is a powerful treatment for the prevention and amelioration of severe, chronic arthritis in a true autoimmune mouse model of RA. Thus, the K/BxN endogenous arthritis model should be useful for testing potential therapeutics for RA. Our findings provide rationale for further examination of the treatment efficacy of immunoglobulin-based therapeutics in rheumatoid arthritis.

GM-CSF and IL-4 are not involved in IVIG-mediated amelioration of ITP in mice: a role for IL-11 cannot be ruled out

Previously, we have reported that interleukin (IL)-4, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-11, but not IL-33, are up-regulated in two strains of mice with immune thrombocytopenia (ITP) that are responsive to intravenous immunoglobulin (IVIg) treatment. Previously, IL-4 was ruled out in the mechanism of IVIg; however, other publications have suggested this cytokine as a major player in the mechanism of IVIg action. Thus, we sought to further investigate a role for IL-4 and, in addition, GM-CSF and IL-11 in the mechanism of action of IVIg using a murine model of ITP. A passive platelet antibody model was used to generate ITP in IL-4 receptor knock-out (IL-4R^-/- ), IL-11 receptor knock-out (IL-11Rα^-/- ) and GM-CSF knock-out (Csf2^-/- ) mice. We also used a neutralizing antibody to IL-11 and recombinant human IL-11 (rhIL-11) in addition to depleting basophils in vivo to study the effect of IVIg to ameliorate ITP. Our results showed that basophils, IL-4 and GM-CSF were unimportant in both ITP induction and its amelioration by IVIg. The role of IL-11 in these processes was less clear. Even though IL-11Rα^-/- mice with ITP responded to IVIg similarly to wild-type (WT) mice, treatment of ITP WT mice with rhIL-11 instead of IVIg showed an increase in platelet numbers and WT mice administered anti-IL-11 showed a significant reduction in the ability of IVIg to ameliorate the ITP. Our findings indicate that neither IL-4, basophils or GM-CSF have roles in IVIg amelioration of ITP; however, a role for IL-11 requires further study.

A randomized, double-blind study of romiplostim to determine its safety and efficacy in children with immune thrombocytopenia

Romiplostim, a thrombopoietin-mimetic peptibody, increases and maintains platelet counts in adults with immune thrombocytopenia (ITP). In this first study of a thrombopoietic agent in children, patients with ITP of ≥ 6 months' duration were stratified by age 1:2:2 (12 months-< 3 years; 3-< 12 years; 12-< 18 years). Children received subcutaneous injections of romiplostim (n = 17) or placebo (n = 5) weekly for 12 weeks, with dose adjustments to maintain platelet counts between 50 × 109/L and 250 × 109/L. A platelet count ≥ 50 × 109/L for 2 consecutive weeks was achieved by 15/17 (88%) patients in the romiplostim group and no patients in the placebo group (P = .0008). Platelet counts ≥ 50 × 109/L were maintained for a median of 7 (range, 0-11) weeks in romiplostim patients and 0 (0-0) weeks in placebo patients (P = .0019). The median weekly dose of romiplostim at 12 weeks was 5 μg/kg. Fourteen responders received romiplostim for 4 additional weeks for assessment of pharmacokinetics. No patients discontinued the study. There were no treatment-related, serious adverse events. The most commonly reported adverse events in children, as in adults, were headache and epistaxis. In this short-term study, romiplostim increased platelet counts in 88% of children with ITP and was well-tolerated and apparently safe.

The trial was registered with http://www.clinicaltrials.gov as NCT00515203.

Initial lymphocyte count and the development of persistent/chronic immune thrombocytopenic purpura

BACKGROUND

Acute immune thrombocytopenic purpura (ITP) is a common, benign, self-limiting disease in children. Chronic ITP is diagnosed when thorombocytopenia persists beyond 12 months. Older age is associated with increased risk for development of chronic ITP. The main objective of the current study was to examine whether total leukocyte (TLC) and absolute lymphocyte counts (ALC) at diagnosis correlate with the persistence of ITP beyond 6 months.

PROCEDURE

Two hundred and twenty four consecutive medical records for patients diagnosed with immune thrombocytopenia, between April 1993 and July 2007, were reviewed and 188 patients were eligible for analysis. Case records were examined to ascertain the following information: age, gender, ethnicity, date of presentation, presenting CBC with differential count, treatment given and the outcome.

RESULTS

The male to female ratio was almost 1:1; 24% (45/188) of patients had persistent ITP beyond 6 months. We determined that age >8.5 year, TLC < 6,250/microl and ALC < 3,050/microl was associated with a significant risk for development of persistent ITP beyond 6 months.

CONCLUSIONS

TLC and ALC at diagnosis are predictive variables for the development of persistent/chronic ITP. Further studies are recommended to confirm the current finding and to assess the underlying pathophysiology with the course of the ITP.

Immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP) is the commonest cause of sudden onset thrombocytopenia in a healthy child. The condition is frequently preceded by a viral infection. The hematological parameters are essentially normal except a low platelet count. Bone marrow examination is not routinely indicated except in specific situations. The pros and cons of drug treatment have been discussed as the disease is benign with excellent prognosis in majority of the cases. The various treatment options including low and high dose steroids, intravenous immunoglobulins and anti D have been discussed at length with other modalities of treatment and role of splenectomy. Current therapeutic options with rituximab and other drugs for stimulating platelet production in chronic cases have also been included in discussion.

Hepatic involvement and portal hypertension predict mortality in chronic granulomatous disease

BACKGROUND & AIMS

Chronic granulomatous disease (CGD) is a rare genetic disorder, predisposing affected individuals to recurrent infectious complications and shortened survival. Liver involvement in CGD includes vascular abnormalities, which may lead to noncirrhotic portal hypertension.

METHODS

To evaluate the impact of noncirrhotic portal hypertension on survival in CGD, all records from 194 patients followed up at the National Institutes of Health with CGD were reviewed. Cox proportional hazards regression was used to determine factors associated with mortality.

RESULTS

Twenty-four patients died, all from infectious complications. By Cox regression, factors associated with mortality were as follows: (1) decreases in platelet count (>9000/microL/y; hazard ratio, 4.7; P = .007), (2) alkaline phosphatase level increases (>0.25/y; hazard ratio, 4.5; P = .01) and (3) history of liver abscess (hazard ratio, 3.1; P = .03). By regression analysis, decreasing platelet count was associated with increasing portal vein diameter, splenomegaly, increased serum immunoglobulin G level, and increasing number of alanine aminotransferase increases; greater number of alkaline phosphatase level increases and abscess were both associated with increasing age and number of infections. Prospective evaluation revealed increased hepatic-venous pressure gradients in 2 patients with progressive thrombocytopenia, suggestive of portal hypertension.

CONCLUSIONS

These data suggest mortality in patients with CGD is associated with the development of noncirrhotic portal hypertension, likely owing to injury to the microvasculature of the liver from repeated systemic and hepatic infections. The slope of decline in platelet count may be a useful measure of progression of portal hypertension over time. Furthermore, the data illustrate the potential independent effect of portal hypertension on clinical outcome outside the setting of cirrhosis.

La prise en charge du purpura thrombopénique idiopathique en phase initiale: enquête auprès des membres de la Société française d'hématologie et d'immunologie pédiatrique (SHIP)

AIM OF THE STUDY

The purpose of this study was to report in acute childhood idiopathic thrombocytopenic purpura (ITP) the current practices of French paediatric hematologists and to compare them to recent publications of American and British teams.

METHOD

A questionnaire was sent online to the members of the French Society of Pediatric Hematology/Immunology (SHIP). This questionnaire, adapted from a similar american study conducted in 2001, asked 16 questions based on the clinical presentation of a 5-year-old boy referred for an acute ITP.

RESULTS

59/123 SHIP members responded to the survey. In response to question regarding initial treatment, 86% of physicians would be given active treatments and only 9% would rarely or never administer any drug. When asked which agent would be used in case of treatment, 68% would choose to prescribe intravenous immunoglobulins and 32% corticosteroids, nobody recommended the use of anti-D immunoglobulins. Furthermore, 83% would usually hospitalize such a child.

CONCLUSION

Finally, this study allowed us to update the current French management of treating pediatric ITP which is almost comparable among this subset of pediatric hematologists, but showed some discrepancies comparatively to the American and British studies.

Intravenous immunoglobulin: an update on the clinical use and mechanisms of action

Initially used as a replacement therapy for immunodeficiency diseases, intravenous immunoglobulin (IVIg) is now widely used for a number of autoimmune and inflammatory diseases. Considerable progress has been made in understanding the mechanisms by which IVIg exerts immunomodulatory effects in autoimmune and inflammatory disorders. The mechanisms of action of IVIg are complex, involving modulation of expression and function of Fc receptors, interference with activation of complement and the cytokine network and of idiotype network, regulation of cell growth, and effects on the activation, differentiation, and effector functions of dendritic cells, and T and B cells.