Fostamatinib
TAVALISSE
Pronunciation: fos-ta-MA-ti-nib (TAV-a-lees)
What it isAn oral spleen tyrosine kinase (SYK) inhibitor whose active metabolite R406 blocks Fc-receptor and B-cell-receptor signaling to reduce antibody-mediated platelet destruction.
Why this oneUsed for chronic immune thrombocytopenia in adults with an insufficient response to prior therapy.
What limits itIt commonly causes hypertension, diarrhea, hepatotoxicity, and neutropenia requiring monitoring, and CYP3A4 inhibitors raise R406 exposure.
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Chronic immune thrombocytopenia (ITP), insufficient response to prior treatment | Adults | 100 mg BID | Lowest dose maintaining platelets >=50 x 10^9/L | 150 mg BID |
Titration After 4 weeks: increase to 150 mg BID if platelets not >=50 x 10^9/L
Renal Undefined
Hepatic Undefined
Monitor: CBC incl. platelets monthly until stable then regularly; LFTs monthly; BP q2wk until stable dose then monthly. Strong CYP3A4 inhibitors increase active metabolite (R406) exposure - monitor for toxicity, dose-modify if needed
Instructions
- With or without food
- Missed dose: take next dose at regularly scheduled time
- Discontinue after 12 weeks if platelet count insufficient to avoid clinically important bleeding
- Dose-reduction ladder for toxicity: 300 -> 200 -> 150 (as 150 mg QAM) -> 100 mg/day; discontinue if <100 mg/day needed
Available strengths
- tab 100, 150 mg
Cautions
- Hypertension (incl. hypertensive crisis 1%) - monitor BP, treat, dose-reduce/interrupt/discontinue if uncontrolled
- Hepatotoxicity (ALT/AST >3x ULN in 9%) - monthly LFTs; interrupt/reduce/discontinue per thresholds
- Diarrhea (31%; severe 1%) - supportive care; interrupt for Grade >=3
- Neutropenia (6%; febrile 1%) - monitor ANC monthly; interrupt if ANC <1.0 x 10^9/L persisting 72 h
- Embryo-fetal toxicity - effective contraception during treatment and >=1 month after
Adverse reactions
- Diarrhea, hypertension, nausea, respiratory infection, dizziness, ALT/AST increased, rash, abdominal pain, fatigue, chest pain, neutropenia (>=5% and > placebo)
- Serious: febrile neutropenia, diarrhea, pneumonia, hypertensive crisis (each 1%)
Pregnancy Can cause fetal harm (animal embryo-fetal mortality/malformations at >=0.3x human exposure); no human data; advise risk and contraception
Lactation Do not breastfeed during treatment and for >=1 month after last dose (R406 5-10x plasma levels in rodent milk)
Cost
| Strength | #/mo | generic $/mo | CostPlus | |
|---|---|---|---|---|
| 100 mg | tab | 60 BID | not offered | |
| 150 mg | tab | 60 BID | not offered |
Generic entry2026
NO BOXED WARNINGS
Principal riskNo FDA boxed warning.