General Information

Tavalisse (fostamatinib disodium hexahydrate) is a tyrosine kinase inhibitor with demonstrated activity against spleen tyrosine kinase (SYK). 

Tavalisse is specifically indicated for the treatment of thrombocytopenia in adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment.

Tavalisse is supplied as a tablet for oral administration. Tavalisse should be initiated at a dose of 100 mg taken orally twice daily. After a month, if platelet count has not increased to at least 50 x 109/L, increase the Tavalisse dose to 150 mg twice daily. Use the lowest dose of Tavalisse to achieve and maintain a platelet count at least 50 x 109/L as necessary to reduce the risk of bleeding. Tavalise may be taken with or without food. 

Mechanism of Action

Tavalisse (fostamatinib disodium hexahydrate) is a tyrosine kinase inhibitor with demonstrated activity against spleen tyrosine kinase (SYK). The major metabolite of fostamatinib, R406, inhibits signal transduction of Fc-activating receptors and B-cell receptor. The fostamatinib metabolite R406 reduces antibody-mediated destruction of platelets.

Side Effects

Adverse events associated with the use of Tavalisse may include, but are not limited to, the following:

• diarrhea
• hypertension
• nausea
• respiratory infection
• dizziness
• ALT/AST increased, rash
• abdominal pain
• fatigue
• chest pain
• neutropenia

Clinical Trial Results

The FDA approval of Tavalisse was based on data from the FIT clinical program. In two parallel, phase 3, multicenter, randomized, double‐blind, placebo‐controlled trials (FIT1 and FIT2), patients with persistent/chronic ITP were randomized 2:1 to fostamatinib (n=101) or placebo (n=49) at 100mg BID for 24 weeks with a dose increase in non‐responders to 150mg BID after 4 weeks. The primary endpoint was stable response (platelets ≥50,000/μL at ≥4 of 6 biweekly visits, weeks 14‐24, without rescue therapy). Baseline median platelet count was 16,000/μL; median duration of ITP was 8.5 years. Stable responses occurred in 18% of patients on fostamatinib vs. 2% on placebo (P=0.0003). Overall responses (defined retrospectively as ≥1 platelet count ≥50,000/μL within the first 12 weeks on treatment) occurred in 43% of patients on fostamatinib vs. 14% on placebo (P=0.0006). Median time to response was 15 days (on 100mg bid), and 83% responded within 8 weeks.