A novel immunomodulatory treatment involving mycophenolate mofetil and corticosteroids for pediatric autoimmune cytopenias

Mycophenolate mofetil for autoimmune cytopenias in children: high rates of response in inborn errors of immunity

Second-line treatments of autoimmune cytopenias (AC) are not well-defined in children. Mycophenolate mofetil (MMF) is an immunosuppressant agent that has been demonstrated to be safe and effective in this setting. A retrospective observational study was conducted in 18 children with prolonged AC who received MMF, in order to describe clinical and biological markers of response. The overall response rate of MMF at 20-30 mg/kg per day was 73.3%. All patients with Evans syndrome (n = 9) achieved complete response. Among the patients with monolineage AC (n = 9), those with an underlying inborn errors of immunity (IEI), tended to respond better to MMF. No biological markers related to treatment response were found. Rather, lymphocyte subpopulations proved useful for patient selection as a marker suggestive of IEI along with immunoglobulin-level determination.

Immunomodulation with romiplostim as a second-line strategy in primary immune thrombocytopenia: The iROM study

Thrombopoietin receptor agonists (TPO-RAs) stimulate platelet production, which might restore immunological tolerance in primary immune thrombocytopenia (ITP). The iROM study investigated romiplostim's immunomodulatory effects. Thirteen patients (median age, 31 years) who previously received first-line treatment received romiplostim for 22 weeks, followed by monitoring until week 52. In addition to immunological data, secondary end-points included the sustained remission off-treatment (SROT) rate at 1 year, romiplostim dose, platelet count and bleedings. Scheduled discontinuation of romiplostim and SROT were achieved in six patients with newly diagnosed ITP, whereas the remaining seven patients relapsed. Romiplostim dose titration was lower and platelet count response was stronger in patients with SROT than in relapsed patients. In all patients, regulatory T lymphocyte (Treg) counts increased until study completion and the counts were higher in patients with SROT. Interleukin (IL)-4, IL-9 and IL-17F levels decreased significantly in all patients. FOXP3 (Treg), GATA3 (Th2) mRNA expression and transforming growth factor-β levels increased in patients with SROT. Treatment with romiplostim modulates the immune system and possibly influences ITP prognosis. A rapid increase in platelet counts is likely important for inducing immune tolerance. Better outcomes might be achieved at an early stage of autoimmunity, but clinical studies are needed for confirmation.

Mycophenolate Mofetil Use in Pediatric Immune Thrombocytopenia Refractory to First-line Therapy: a Single-center Experience

Most children treated for immune thrombocytopenia remit during the first year following diagnosis. For the ∼40% who develop persistent or chronic disease, second-line treatment options include immunomodulation and thrombomimetic agents. While immunomodulators target the underlying mechanism, prolonged immunosuppression may increase the risk of infection. We report the use of the reversible immunomodulating agent mycophenolate mofetil (MMF) in 16 pediatric patients with immune thrombocytopenia refractory to first-line treatment. Using escalating doses up to 2400 mg/m 2 /d, MMF treatment resulted in a 73% response rate. Adverse events were mostly mild and tolerable. Complete responders have been successfully tapered off MMF with sustained responses.

Treatment of immune-mediated cytopenias in patients with primary immunodeficiencies and immune regulatory disorders (PIRDs)

Severe immune cytopenias (SICs) are rare acquired conditions characterized by immune-mediated blood cell destruction. They may necessitate emergency medical management and long-term immunosuppressive therapy, strongly compromising the quality of life. The initial diagnostic workup involves excluding malignancies, congenital cytopenias, bone marrow failure syndromes, infections, and rheumatologic diseases such as systemic lupus erythematosus. Causal factors for SIC such as primary immunodeficiencies or immune regulatory disorders, which are referred to as inborn errors of immunity (IEIs), should be diagnosed as early as possible to allow the initiation of a targeted therapy and avoid multiple lines of ineffective treatment. Ideally, this therapy is directed against an overexpressed or overactive gene product or substitutes a defective protein, restoring the impaired pathway; it can also act indirectly, enhancing a countermechanism against the disease-causing defect. Ultimately, the diagnosis of an underling IEI in patients with refractory SIC may lead to evaluation for hematopoietic stem cell transplantation or gene therapy as a definitive treatment. Interdisciplinary care is highly recommended in this complex patient cohort. This case-based educational review supports decision making for patients with immune-mediated cytopenias and suspected inborn errors of immunity.

The effect of mycophenolate mofetil on platelet function

: Mycophenolate mofetil (MMF) raises platelet counts in patients with primary immune thrombocytopenia. However, studies indicate that MMF inhibits collagen-induced platelet aggregation, potentially increasing bleeding risk following MMF therapy. The study evaluates the in-vitro effect of MMF on platelet function. Blood samples (n = 6) from healthy donors were incubated with vehicle, MMF or mycophenolic acid (MPA) at clinically relevant concentrations. Platelet aggregation was measured with flow cytometry and 96-well light transmission aggregometry (LTA). Using flow cytometry, we measured the expression of platelet CD49b, CD42b, CD42a, CD61 and CD41. Platelet activation was measured as the expression of P-selectin and the active form of the GPIIb/IIIa receptor following agonist stimulation. Agonists were: ADP, thrombin receptor-activating peptide, collagen, collagen-related peptide and U46619. The Platelet Function Analyzer-200 was used to measure global platelet function. MMF and MPA did not change platelet aggregation regardless of the agonist used. An exception was a significant, but minor decrease in collagen-induced platelet aggregation in samples with MMF (6 ± 3%, P = 0.02) and MPA (8 ± 4%, P = 0.01) compared with vehicle (22 ± 11%). However, this was not observed using the lesser sensitive LTA method. Compared with vehicle, MPA led to a significantly lower relative disposition of the surface collagen-receptor GPVI (7.8 ± 1.8 versus 8.8 ± 2.1 mean fluorescence intensity, P < 0.001). In all other platelet-related tests, neither MMF nor MPA showed any effect. In conclusion, MMF and MPA only had a minor effect on collagen-induced platelet aggregation, with MPA reducing the relative disposition of surface GPVI receptors.