Fostamatinib disodium hexahydrate (Tavalisse), a kinase inhibitor, was granted FDA approval for the treatment of thrombocytopenia in adult patients with chronic immune thrombocytopenia (ITP) who have had insufficient response to a previous treatment.
Recommended dose is 100 mg orally twice daily. If a platelet count of at least 50×109/L is not achieved in 1 month after therapy initiation, the dose should be increased to 150 mg orally twice daily.
The application was granted a standard review and orphan product designation. The approval was based on results from FIT-1 [ClinicalTrials.gov Identifier: NCT02076399] and FIT-2 [ClinicalTrials.gov Identifier: NCT02076412] trials, two identical, double-blind, placebo-controlled trials that enrolled a total of 150 patients with persistent or chronic ITP. The patients had had insufficient response to previous treatment with corticosteroids, immunoglobulins, splenectomy, and/or a thrombopoietin receptor agonist. In the trials, patients were randomized 2:1 to receive fostamatinib 100 mg orally twice daily or placebo for 24 weeks. Dose escalation to 150 mg orally twice daily was allowed after 1 month.
Stable platelet response of at least 50×109/L on at least 4 visits between weeks 14 and 24 was used to determine efficacy. In FIT-1, stable response was achieved in 9 patients (18%) in the fostamatinib group vs 0 patients (0%) in the placebo group (P=.03). In FIT-2, stable platelet response was achieved in 8 patients (16%) in the fostamatinib group vs 1 patient (4%) in the placebo group (P=.26).
In the FIT-3 extension study (ClinicalTrials.gov Identifier: NCT 02077192), a stable response was observed in 10 patients (23%) newly exposed to fostamatinib. Durable platelet responses were seen in all the studies.
The most common adverse reactions — reported by at least 5% of patients in the treatment groups — were abdominal pain, chest pain, diarrhea, dizziness, fatigue, hypertension, increased ALT/AST, rash, respiratory infection, nausea, and neutropenia. In the ITP double-blind studies, Serious adverse drug reactions reported in the ITP double-blind studies were diarrhea, febrile neutropenia, hypertensive crisis, and pneumonia; each reaction occurred in 1% of patients receiving fostamatinib.
FDA approves fostamatinib tablets for ITP [news release]. Silver Spring, MD: US Food and Drug Administration; April 17, 2018. https://www.fda.gov/drugs/informationondrugs/approveddrugs/ucm604956.htm. Accessed April 18, 2018.