Fostamatinib for the treatment of Japanese patients with primary immune thrombocytopenia: A phase 3, placebo-controlled, double-blind, parallel-group study

Sustained response off treatment after fostamatinib in refractory immune thrombocytopenia: A series of four case reports

INTRODUCTION

A goal of most primary immune thrombocytopenia (ITP) treatments is reducing or discontinuing treatment while maintaining a response including an absence of bleeding events. We present four cases describing treatment with the spleen tyrosine kinase (SYK) inhibitor, fostamatinib, that showed sustained response off treatment (SROT).

CASE PRESENTATIONS

Case 1 was a 66-year-old male with chronic ITP. He was pre-treated with prednisone and rituximab before being in the FIT-2 clinical trial (placebo). He received fostamatinib in the FIT-3 open-label extension for seven weeks and maintained SROT for 2.5 years. Case 2 was a 54-year-old female patient with chronic, highly refractory ITP. SROT was achieved after 6 months of fostamatinib and was maintained for more than 16 months (in remission to date). Case 3 was a 60-year-old male with chronic ITP. He was successfully treated with cycles of corticosteroids for six years prior to fostamatinib. He was treated with fostamatinib plus prednisone for approximately two months. SROT was observed in this patient for one year. Case 4 was a 67-year-old male with persistent ITP. Before fostamatinib, he was unresponsive to high-dose dexamethasone, IVIG, eltrombopag and romiplostim. After 11 months of fostamatinib, his dose was tapered for three months and ultimately discontinued. SROT was observed for more than ten months (in remission to date).

DISCUSSION

These cases emphasize that SROT is achievable with fostamatinib in complex ITP cases unresponsive to multiple previous therapies. Additional research is needed to identify the magnitude of the underlying mechanisms, and the clinical factors associated with, and potentially predictive of, SROT.

Long-term safety and efficacy of fostamatinib in Japanese patients with primary immune thrombocytopenia

Fostamatinib had superior efficacy to a placebo and acceptable safety profiles for at least 1 year in a phase 3 study of Japanese patients with primary immune thrombocytopenia. Here, we report the 3-year safety and efficacy of fostamatinib in that study. Data from 33 patients who received at least one dose of fostamatinib were analyzed. A platelet response > 50,000/µL (at two consecutive visits at least 28 days apart while receiving fostamatinib) was achieved in 16 patients (48%). The median total duration of a platelet response > 50,000/µL was 589 (range: 106-1003) days. Gastrointestinal disorders, such as diarrhea, hypertension, and hepatic enzyme elevation, were the most common fostamatinib-related adverse events. Most events occurred within 12 weeks of treatment. No thromboembolisms, treatment-related infections, or moderate or severe treatment-related bleeding events were observed. In summary, this extension study of a clinical trial found a sustained platelet response without new safety signals during 3-year treatment with fostamatinib.

Spleen tyrosine kinase aggravates intestinal inflammation through regulating inflammatory responses of macrophage in ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is a persistent chronic, non-specific inflammatory disease, and macrophages play a crucial role in its pathogenesis. Spleen tyrosine kinase (Syk) is strongly associated with the pathogenesis of several inflammatory diseases. However, the role of Syk in the pathogenesis of UC is still obscure.

METHODS

Syk expression was analyzed in peripheral blood mononuclear cells (PBMCs) and colonic tissues of UC patients using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunofluorescence. A public database was used to analyze the expression of selected signature genes of interest in UC patients with different expressions of Syk. R788, a small molecule inhibitor of Syk, was used to treat macrophages from mice. The functions of macrophages were assessed using qRT-PCR, flow cytometry, and fluorescence microscopy. Dextran sodium sulfate (DSS)-induced colitis mice model was established to determine the role of Syk in UC.

RESULTS

The Syk levels were markedly increased in PBMCs, colonic tissues, and colonic mucosa lamina propria macrophages from UC patients, and positively related to disease activity. Inhibition of Syk with R788 decreased pro-inflammatory genes expression and increased anti-inflammatory genes expression in peritoneal macrophages and bone marrow macrophages. Blockade of Syk enhanced phagocytosis and bactericidal ability of macrophages. Syk promoted the production of reactive oxygen species of macrophages and M1-type macrophage polarization. Furthermore, inhibition of Syk alleviated intestinal mucosal inflammation in DSS-induced colitis model.

CONCLUSIONS

Syk plays a vital role in intestinal inflammation by regulating inflammatory responses of macrophages in UC. Targeting Syk may be a promising therapeutic approach for UC.

Efficacy and safety of fostamatinib in refractory immune thrombocytopenia: a meta-analysis from randomized controlled trials

BACKGROUND

Immune thrombocytopenia (ITP) is an immune-mediated disease that results in low platelet counts. Despite appropriate treatment, many patients continue to experience refractory disease. Fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, has emerged as a promising option for refractory ITP.

OBJECTIVE

This meta-analysis aims to evaluate the efficacy and safety of fostamatinib compared to conventional therapy in adults aged ≥ 18 years with refractory ITP.

MATERIALS AND METHODS

Literature search was conducted in PubMed, Scopus, Embase, and clinicaltrials.gov databases from inception to March 31, 2024. Randomized controlled trials (RCTs) assessing the safety and efficacy of fostamatinib in adults with refractory ITP were included. Data extraction, risk of bias assessment, and statistical analysis were performed following PRISMA guideline.

RESULTS

A total of 495 articles were screened, with three RCTs meeting the inclusion criteria. Fostamatinib therapy demonstrated superior efficacy in achieving stable platelet response by week 24 (ORR 0.80; 95%CI 0.72-0.88), platelet count ≥ 50,000/µL at weeks 12 (ORR 0.80; 95%CI 0.72-0.90) and week 24 (ORR 0.82; 95%CI 0.72-0.90). Additionally, fostamatinib improves platelet counts in subjects with a baseline count of < 15,000/µL. The Number Needed to Treat (NNT) was calculated as 10. Adverse effects include diarrhea (RR 2.32; 95%CI 1.11-4.84), hypertension (RR 2.33; 95%CI 1.00-5.43), and abnormal liver function tests (RR 4.18; 95% CI 1.00-17.48). Interestingly, the occurrences of nausea (RR 1.77; 95% CI 0.33-9.67) and rash (RR 2.28; 95% CI 0.50-10.29) did not achieve statistical significance.

CONCLUSION

This meta-analysis provides robust evidence supporting the efficacy of fostamatinib in improving platelet counts and achieving therapeutic goals in adults with refractory ITP. However, fostamatinib's safety profile warrants consideration due to higher rates of diarrhea, hypertension, and abnormal liver function tests.

Fostamatinib for immune thrombocytopenic purpura in adult patients: A systematic review and meta-analysis

Immune thrombocytopenic purpura (ITP) is an immune disorder characterized by thrombocytopenia. Fostamatinib is an orally administered spleen tyrosine kinase inhibitor intended to treat refractory ITP. To evaluate the efficacy and safety of fostamatinib as a subsequent-line therapy for ITP in adults. We searched four electronic databases for primary studies of any design. Primary efficacy outcomes included proportions of patients achieving overall (≥30 × 109 cells/L), partial (≥50 × 109 cells/L), and stable (as defined in original studies) platelet response. Safety outcomes included rescue medication use and other adverse events. We used narrative synthesis and Mantel-Haenszel random effect meta-analysis to summarize results. Our systematic review included 11 studies for analyses (n = 722). Weighted mean proportions of patients achieving overall, partial, and stable responses with fostamatinib treatment were 0.70 [0.62, 0.76], 0.48 [0.36, 0.61], and 0.28 [0.16, 0.44], respectively. Fostamatinib was favored over placebo for partial (relative risk [RR] = 3.04, 95% confidence interval [CI] [1.53, 6.06]) and stable (RR = 6.43, 95% CI [1.58, 26.23]) responses. Patients on fostamatinib required less rescue medication and were more likely to experience hypertension. Fostamatinib is a viable subsequent-line therapy option for refractory ITP. Given the heterogeneous data and large number of small studies, these results should be interpreted cautiously.

Post-marketing safety surveillance of fostamatinib: an observational, pharmacovigilance study leveraging FAERS database

OBJECTIVE

Fostamatinib, an FDA-approved oral small-molecule spleen tyrosine kinase (SYK) inhibitor, is used to treat thrombocytopenia in adults with chronic immune thrombocytopenia (ITP) who have not responded to previous treatments. However, comprehensive safety data is lacking. This study uses the FDA Adverse Event Reporting System (FAERS) database to explore real-world adverse events (AEs) related to fostamatinib, aiming to inform its clinical use.

METHODS

The FAERS database was retrospectively queried to extract reports associated with fostamatinib from 2019 to 2023. To identify and evaluate potential AEs in patients receiving fostamatinib, various disproportionality analyses such as the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multi-item gamma Poisson shrinker (MGPS) were employed.

RESULTS

A total of 23 AE signals were included in our analysis. Among them, hypertension, blood pressure increase, blood pressure abnormality, hepatic enzyme increase, and diarrhea were consistent with the common AEs described for fostamatinib in clinical trials. In addition, unexpected serious AEs were detected including cerebral thrombosis and necrotizing soft tissue infection. The median time to onset of fostamatinib-related AEs was 86 days.

CONCLUSION

Our investigation revealed several possibly emergent safety concerns associated with fostamatinib in real-world clinical practice, which might provide essential vigilance evidence for clinicians and pharmacists to manage the safety issues of fostamatinib.

Treatment with fostamatinib in patients with immune thrombocytopenia: Experience from the Andalusian region in Spain-The Fostasur Study

Immune thrombocytopenia (ITP) is characterized by low platelet counts (PLTs) and an increased risk of bleeding. Fostamatinib, a spleen tyrosine kinase inhibitor, has been approved as a second-line treatment for ITP. Real-world data on fostamatinib are lacking. This observational, retrospective, multicentre study, conducted in the Andalusia region of Spain, evaluated 44 adult primary ITP patients (47.7% female; median age 58 years; newly diagnosed ITP 6.8%; persistent 13.6%; chronic 79.5%; median four prior treatments) after ≥ 4 weeks of fostamatinib therapy. The median PLT at the initiation of fostamatinib was 15 × 109/L. Common reasons for starting fostamatinib were refractoriness or intolerance to prior therapy, oral medication preference, history of thrombosis and cardiovascular risk. Dosing was individualized based on efficacy and tolerance. After 2 weeks, global response rate was 56.8% (response and complete response). Response rates were 70.5%, 62.5% and 64% at 4 weeks, 12 weeks and at the end of the study respectively. Adverse events were mild, and no patients discontinued as a result. This real-world study demonstrated a response rate similar to fostamatinib as seen in the pivotal clinical trials while including newly diagnosed patients and allowing for individualized dosing.

Addressing thrombosis concerns in immune thrombocytopenia: the role of fostamatinib in immune thrombocytopenia management

INTRODUCTION

Immune thrombocytopenia (ITP), a disease that commonly presents with an increased risk of bleeding, can also paradoxically produce an increased risk of thromboembolic events. The risk of thromboembolism can be associated with patient-related factors (e.g. co-morbidities, age and history of thrombosis), disease-related factors (e.g. a greater proportion of younger, more reactive platelets, and the presence of microparticles and pro-inflammatory cytokines) and treatment-related factors (e.g. splenectomy, thrombopoietin receptor agonists, and IVIg).

AREAS COVERED

Aspects of the pathophysiology of ITP and the effects of treatment are discussed with emphasis on individualizing treatment based on the patient's thromboembolic risk, treatment options and preferences.

EXPERT OPINION

An increased understanding of the pathophysiology of ITP has led to the development of new agents such as fostamatinib, a spleen tyrosine kinase inhibitor. Further research into the factors contributing to the risks for bleeding and thromboembolic events can contribute to the development of more specific therapies for ITP and allow greater individualization of therapy based on each patient's medical history and clinical status.