Fostamatinib: Drug information

(For additional information see "Fostamatinib: Patient drug information")

For abbreviations, symbols, and age group definitions used in Lexicomp (show table)

Brand Names: US

Tavalisse

Brand Names: Canada

Tavalisse

Pharmacologic Category

Spleen Tyrosine Kinase (Syk) Inhibitor;
Tyrosine Kinase Inhibitor

Dosing: Adult

Note: Use the lowest dose necessary to achieve and maintain platelet count of at least 50,000/mm³ as necessary to reduce the risk of bleeding; discontinue after 12 weeks if platelet count does not increase to a level sufficient to avoid clinically important bleeding.

Immune thrombocytopenia, chronic, refractory

Immune thrombocytopenia, chronic, refractory: Initial: Oral: 100 mg twice daily; if platelet count has not increased to at least 50,000/mm³ after 1 month, increase dose to 150 mg twice daily (Ref).

Missed doses: If a dose is missed, the next scheduled dose should be administered at the regularly scheduled time.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Dosing: Kidney Impairment: Adult

There are no dosage adjustments provided in the manufacturer's labeling; renal impairment does not alter fostamatinib pharmacokinetics, therefore, dosage adjustment is not likely necessary.

Dosing: Hepatic Impairment: Adult

Hepatic impairment at treatment initiation: There are no dosage adjustments provided in the manufacturer's labeling; hepatic impairment does not alter fostamatinib pharmacokinetics, therefore, dosage adjustment is not likely necessary.

Hepatotoxicity during treatment:

Note: Refer to "Dosing - Adjustment for Toxicity" for fostamatinib dosage adjustment levels.

ALT, AST ≥3 and <5 times ULN and asymptomatic: Recheck LFTs every 72 hours until ALT, AST values are no longer elevated (<1.5 times ULN) and total bilirubin remains <2 times ULN; consider fostamatinib interruption or dose reduction if ALT, AST, and total bilirubin remain elevated (ALT, AST 3 to 5 times ULN with bilirubin <2 times ULN); if interrupted, resume fostamatinib at the next lower dosage level when ALT and AST are no longer elevated (<1.5 times ULN) and total bilirubin remains <2 times ULN.

ALT, AST ≥3 and <5 times ULN and symptomatic (eg, nausea, vomiting, abdominal pain): Interrupt fostamatinib. Recheck LFTs every 72 hours until ALT, AST values are no longer elevated (<1.5 times ULN) and total bilirubin remains <2 times ULN, then resume fostamatinib at the next lower dosage level.

ALT, AST ≥5 times ULN and total bilirubin <2 times ULN: Interrupt fostamatinib. Recheck LFTs every 72 hours. If ALT and AST decrease, recheck until ALT and AST are no longer elevated (<1.5 times ULN) and total bilirubin remains <2 times ULN, then resume fostamatinib at the next lower dosage level. If ALT, AST persist at ≥5 times ULN for ≥2 weeks, discontinue fostamatinib.

ALT, AST ≥3 times ULN and total bilirubin >2 times ULN: Discontinue fostamatinib.

Elevated unconjugated (indirect) bilirubin (in the absence of other LFT abnormalities): Continue fostamatinib; monitor frequently. Isolated increases in unconjugated bilirubin may be due to UGT1A1 inhibition.

Dosing: Adjustment for Toxicity: Adult

**Recommended Fostamatinib Dose Reduction Levels**
Usual maximum daily dose	300 mg/day (150 mg twice daily)
First dosage reduction level	200 mg/day (100 mg twice daily)
Second dosage reduction level	150 mg/day (150 mg once daily in the morning)
Third dosage reduction level	100 mg/day (100 mg once daily in the morning)
If further dosage reduction is required (at 100 mg/day), discontinue fostamatinib.

**Recommended Fostamatinib Dose Modifications and Management for Specific Adverse Reactions**
Adverse Reaction	Recommended Action
Hypertension
Stage 1: Systolic between 130 to 139 mm Hg or diastolic between 80 to 89 mm Hg	Initiate or increase dosage of antihypertensive medication for patients with increased cardiovascular risk, and adjust as needed until BP is controlled. If the BP target is not met after 8 weeks, reduce fostamatinib to next lower daily dose level.
Stage 2: Systolic ≥140 to 180 mm Hg or diastolic ≥90 to 120 mm Hg	Initiate or increase dosage of antihypertensive medication, and adjust as needed until BP is controlled. If BP remains ≥140/90 mm Hg for >8 weeks, reduce fostamatinib to next lower daily dose level. If BP remains ≥160/100 mm Hg for >4 weeks despite aggressive antihypertensive therapy, interrupt or discontinue fostamatinib.
Hypertensive crisis: Systolic >180 mm Hg and/or diastolic >120 mm Hg	Interrupt or discontinue fostamatinib. Initiate or increase dosage of antihypertensive medication, and adjust as needed until BP is controlled. If BP returns to less than the target BP, resume fostamatinib at same daily dose. If repeat BP is ≥160/100 mm Hg for >4 weeks despite aggressive antihypertensive treatment, discontinue fostamatinib.
Diarrhea
Diarrhea	Manage diarrhea using supportive measures (eg, dietary changes, hydration and/or antidiarrheal medication) early after diarrhea onset until symptom(s) have resolved. If symptom(s) become severe (grade 3 or above), temporarily interrupt fostamatinib. If diarrhea improves to mild (grade 1), resume fostamatinib at the next lower daily dose level.
Neutropenia
Neutropenia	If absolute neutrophil count decreases (ANC <1,000/mm³) and remains low after 72 hours, temporarily interrupt fostamatinib until resolved (ANC >1,500/mm³). Resume fostamatinib at the next lower daily dose level.

Dosing: Older Adult

Refer to adult dosing.

Adverse Reactions

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.

>10%:

Cardiovascular: Hypertension (28%)

Central nervous system: Dizziness (11%)

Gastrointestinal: Diarrhea (31%), nausea (19%)

Hepatic: Increased serum ALT (11%)

Respiratory: Respiratory tract infection (11%)

1% to 10%:

Cardiovascular: Chest pain (6%), hypertensive crisis (1%), syncope (1%, serious)

Central nervous system: Fatigue (6%)

Dermatologic: Skin rash (9%)

Gastrointestinal: Abdominal pain (6%), toothache (1%, serious)

Hematologic & oncologic: Neutropenia (6%), febrile neutropenia (1%)

Hepatic: Increased serum AST (9%)

Neuromuscular & skeletal: Arthralgia (1%, serious), limb pain (1%, serious)

Renal: Nephrolithiasis (1%, serious)

Respiratory: Dyspnea (2%, serious), hypoxia (1%, serious)

Contraindications

There are no contraindications listed in the manufacturer's US labeling.

Canadian labeling: Hypersensitivity to fostamatinib or any component of the formulation; pregnancy.

Warnings/Precautions

Concerns related to adverse effects:

• GI toxicity: Diarrhea occurred in nearly one-third of patients treated with fostamatinib; severe diarrhea occurred rarely.

• Hepatotoxicity: Elevated liver function tests (predominantly ALT and AST) may occur with fostamatinib treatment; ALT and AST elevations >3 times the upper limit of normal (ULN) have been reported. Transaminases recovered to baseline levels within 2 to 6 weeks of dose modification in most patients.

• Hypertension: Hypertension may occur with fostamatinib; hypertensive crisis has been reported rarely. Patients with pre-existing hypertension may be more susceptible to the hypertensive effects of fostamatinib.

• Neutropenia: Neutropenia has occurred with fostamatinib treatment; neutropenic fever has been reported rarely.

Disease-related concerns:

• Immune thrombocytopenia: If on a stable dose for 14 days prior to baseline, patients were allowed to continue one other concomitant immune thrombocytopenia medication (eg, corticosteroids at <20 mg/day prednisone equivalent, azathioprine, or danazol) throughout studies; rescue therapies (eg, IV immune globulin, Rh_o(D) immune globulin, corticosteroids, platelet transfusion) were also allowed (Bussel 2018).

Special populations:

• Pediatrics: Due to potential adverse effects on actively growing bones, use in patients under 18 years of age is not recommended.

Dosage Forms: US

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral, as disodium hexahydrate:

Tavalisse: 100 mg, 150 mg

Generic Equivalent Available: US

Pricing: US

Tablets (Tavalisse Oral)

100 mg (per each): $292.40

150 mg (per each): $292.40

Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.

Dosage Forms: Canada

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral, as disodium hexahydrate:

Tavalisse: 100 mg, 150 mg

Administration: Adult

Oral: Administer with or without food. Twice-daily doses should be administered in the morning and evening; once-daily doses (due to dose reduction for toxicity) should be administered in the morning.

Hazardous Drugs Handling Considerations

This medication is not on the NIOSH (2016) list; however, it may meet the criteria for a hazardous drug. Fostamatinib may cause teratogenicity and has a structural and/or toxicity profile similar to existing hazardous agents.

Use appropriate precautions for receiving, handling, storage, preparation, dispensing, transporting, administration, and disposal. Follow NIOSH and USP 800 recommendations and institution-specific policies/procedures for appropriate containment strategy (NIOSH 2016; USP-NF 2020).

Note: Facilities may perform risk assessment of some hazardous drugs to determine if appropriate for alternative handling and containment strategies (USP-NF 2020). Refer to institution-specific handling policies/procedures.

Use: Labeled Indications

Immune thrombocytopenia, chronic, refractory: Treatment of thrombocytopenia in adults with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment.

Medication Safety Issues

Sound-alike/look-alike issues:

Fostamatinib may be confused with afatinib, Fosamax, fosamprenavir, fosaprepitant, fosnetupitant, ifosfamide, imatinib, tafasitamab.

High alert medication:

This medication is in a class the Institute for Safe Medication Practices (ISMP) includes among its lists of drug classes which have a heightened risk of causing significant patient harm when used in error.

Metabolism/Transport Effects

Substrate of CYP3A4 (major), UGT1A9; Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential; Inhibits BCRP/ABCG2, P-glycoprotein/ABCB1

Drug Interactions

Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.

Afatinib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Afatinib. Management: If combined, administer the P-gp inhibitor simultaneously with, or after, the dose of afatinib. Monitor closely for signs and symptoms of afatinib toxicity and if the combination is not tolerated, reduce the afatinib dose by 10 mg. Risk D: Consider therapy modification

Aliskiren: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Aliskiren. Risk C: Monitor therapy

Alpelisib: BCRP/ABCG2 Inhibitors may increase the serum concentration of Alpelisib. Management: Avoid coadministration of BCRP/ABCG2 inhibitors and alpelisib due to the potential for increased alpelisib concentrations and toxicities. If coadministration cannot be avoided, closely monitor for increased alpelisib adverse reactions. Risk D: Consider therapy modification

Androgens: Hypertension-Associated Agents may enhance the hypertensive effect of Androgens. Risk C: Monitor therapy

Berotralstat: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Berotralstat. Management: Decrease the berotralstat dose to 110 mg daily when combined with P-glycoprotein (P-gp) inhibitors. Risk D: Consider therapy modification

Bilastine: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Bilastine. Risk X: Avoid combination

Celiprolol: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Celiprolol. Risk C: Monitor therapy

Cladribine: BCRP/ABCG2 Inhibitors may increase the serum concentration of Cladribine. Management: Avoid concomitant use of BCRP inhibitors during the 4 to 5 day oral cladribine treatment cycles whenever possible. If combined, consider dose reduction of the BCRP inhibitor and separation in the timing of administration. Risk D: Consider therapy modification

Clofazimine: May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Risk C: Monitor therapy

Colchicine: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Colchicine. Colchicine distribution into certain tissues (e.g., brain) may also be increased. Management: This combination is often contraindicated, but combined use may be permitted with dose adjustment and monitoring. Recommendations vary based on brand, indication, use of CYP3A4 inhibitors, and hepatic/renal function. See interaction monograph for details. Risk D: Consider therapy modification

CycloSPORINE (Systemic): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of CycloSPORINE (Systemic). Risk C: Monitor therapy

CYP3A4 Inducers (Moderate): May decrease serum concentrations of the active metabolite(s) of Fostamatinib. Risk C: Monitor therapy

CYP3A4 Inducers (Strong): May decrease serum concentrations of the active metabolite(s) of Fostamatinib. Risk X: Avoid combination

CYP3A4 Inhibitors (Strong): May increase serum concentrations of the active metabolite(s) of Fostamatinib. Risk C: Monitor therapy

Dabigatran Etexilate: P-glycoprotein/ABCB1 Inhibitors may increase serum concentrations of the active metabolite(s) of Dabigatran Etexilate. Risk C: Monitor therapy

Digoxin: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Digoxin. Management: Measure digoxin serum concentrations before initiating treatment with these P-glycoprotein (P-gp) inhibitors. Reduce digoxin concentrations by either reducing the digoxin dose by 15% to 30% or by modifying the dosing frequency. Risk D: Consider therapy modification

DOXOrubicin (Conventional): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of DOXOrubicin (Conventional). Risk X: Avoid combination

DOXOrubicin (Liposomal): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of DOXOrubicin (Liposomal). Risk C: Monitor therapy

Edoxaban: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Edoxaban. Risk C: Monitor therapy

Etoposide: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Etoposide. Risk C: Monitor therapy

Etoposide Phosphate: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Etoposide Phosphate. Risk C: Monitor therapy

Everolimus: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Everolimus. Risk C: Monitor therapy

Fexinidazole: May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Risk X: Avoid combination

Fusidic Acid (Systemic): May increase the serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Risk X: Avoid combination

Glecaprevir and Pibrentasvir: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Glecaprevir and Pibrentasvir. Risk C: Monitor therapy

Lapatinib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Lapatinib. Risk C: Monitor therapy

Larotrectinib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Larotrectinib. Risk C: Monitor therapy

Lefamulin: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Lefamulin. Management: Avoid concomitant use of lefamulin tablets with P-glycoprotein/ABCB1 inhibitors. If concomitant use is required, monitor for lefamulin adverse effects. Risk D: Consider therapy modification

Morphine (Systemic): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Morphine (Systemic). Risk C: Monitor therapy

Nadolol: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Nadolol. Risk C: Monitor therapy

Naldemedine: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Naldemedine. Risk C: Monitor therapy

Naloxegol: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Naloxegol. Risk C: Monitor therapy

PAZOPanib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of PAZOPanib. Risk X: Avoid combination

PAZOPanib: BCRP/ABCG2 Inhibitors may increase the serum concentration of PAZOPanib. Risk X: Avoid combination

Pralsetinib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Pralsetinib. Management: If this combo cannot be avoided, decrease pralsetinib dose from 400 mg daily to 300 mg daily; from 300 mg daily to 200 mg daily; and from 200 mg daily to 100 mg daily. Risk D: Consider therapy modification

Ranolazine: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Ranolazine. Risk C: Monitor therapy

Relugolix: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Relugolix. Management: Avoid coadministration of relugolix with oral P-gp inhibitors whenever possible. If combined, take relugolix at least 6 hours prior to the P-gp inhibitor and monitor patients more frequently for adverse reactions. Risk D: Consider therapy modification

Relugolix, Estradiol, and Norethindrone: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Relugolix, Estradiol, and Norethindrone. Management: Avoid use of relugolix/estradiol/norethindrone with P-glycoprotein (P-gp) inhibitors. If concomitant use is unavoidable, relugolix/estradiol/norethindrone should be administered at least 6 hours before the P-gp inhibitor. Risk D: Consider therapy modification

Repotrectinib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Repotrectinib. Risk X: Avoid combination

RifAXIMin: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of RifAXIMin. Risk C: Monitor therapy

Rimegepant: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Rimegepant. Management: Avoid administration of another dose of rimegepant within 48 hours if given concomitantly with a P-glycoprotein (P-gp) inhibitor. Risk D: Consider therapy modification

RisperiDONE: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of RisperiDONE. Risk C: Monitor therapy

RomiDEPsin: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of RomiDEPsin. Risk C: Monitor therapy

Rosuvastatin: Fostamatinib may increase the serum concentration of Rosuvastatin. Management: Limit the dose of rosuvastatin to 20 mg daily when combined with fostamatinib. Monitor closely for increased rosuvastatin effects/toxicities (eg, myalgias, rhabdomyolysis) when these agents are combined. Risk D: Consider therapy modification

Saquinavir: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Saquinavir. Risk C: Monitor therapy

Silodosin: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Silodosin. Risk C: Monitor therapy

Simvastatin: Fostamatinib may increase the serum concentration of Simvastatin. Risk C: Monitor therapy

Sirolimus (Conventional): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Sirolimus (Conventional). Management: Avoid concurrent use of sirolimus with P-glycoprotein (P-gp) inhibitors when possible and alternative agents with lesser interaction potential with sirolimus should be considered. Monitor for increased sirolimus concentrations/toxicity if combined. Risk D: Consider therapy modification

Sirolimus (Protein Bound): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Sirolimus (Protein Bound). Risk X: Avoid combination

Solriamfetol: May enhance the hypertensive effect of Hypertension-Associated Agents. Risk C: Monitor therapy

Tacrolimus (Systemic): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Tacrolimus (Systemic). Risk C: Monitor therapy

Talazoparib: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Talazoparib. Risk C: Monitor therapy

Talazoparib: BCRP/ABCG2 Inhibitors may increase the serum concentration of Talazoparib. Risk C: Monitor therapy

Tegaserod (Withdrawn from US Market): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Tegaserod (Withdrawn from US Market). Risk C: Monitor therapy

Teniposide: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Teniposide. Risk C: Monitor therapy

Tenofovir Disoproxil Fumarate: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Tenofovir Disoproxil Fumarate. Risk C: Monitor therapy

Topotecan: BCRP/ABCG2 Inhibitors may increase the serum concentration of Topotecan. Risk X: Avoid combination

Topotecan: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Topotecan. Risk X: Avoid combination

Ubrogepant: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Ubrogepant. Management: Use an initial ubrogepant dose of 50 mg and second dose (at least 2 hours later if needed) of 50 mg when used with a P-gp inhibitor. Risk D: Consider therapy modification

Venetoclax: P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of Venetoclax. Management: Reduce the venetoclax dose by at least 50% in patients requiring concomitant treatment with P-glycoprotein (P-gp) inhibitors. Resume the previous venetoclax dose 2 to 3 days after discontinuation of a P-gp inhibitor. Risk D: Consider therapy modification

VinCRIStine (Liposomal): P-glycoprotein/ABCB1 Inhibitors may increase the serum concentration of VinCRIStine (Liposomal). Risk X: Avoid combination

Reproductive Considerations

Evaluate pregnancy status prior to treatment in patients who could become pregnant; effective contraception should be used during treatment and for at least 1 month after the last fostamatinib dose.

Pregnancy Considerations

Based on the mechanism of action and information from animal reproduction studies, fostamatinib may cause fetal harm if exposure occurs during pregnancy.

Breastfeeding Considerations

It is not known if fostamatinib is present in breast milk.

Due to the potential for serious adverse events in the breastfed infant, the manufacturer does not recommend breastfeeding during therapy and for at least 1 month after the last fostamatinib dose.

Monitoring Parameters

CBC including platelets (baseline and monthly until a stable platelet count of ≥50,000/mm³ is achieved, then regularly); LFTs (ALT, AST, bilirubin [baseline and monthly; monitor every 72 hours if clinically indicated]). Evaluate pregnancy status (prior to treatment initiation in patients who could become pregnant). Monitor BP (baseline and every 2 weeks until stable dose is established, then monthly thereafter; monitor more frequently if clinically indicated). Monitor for signs/symptoms of diarrhea, infection, and hepatotoxicity. Monitor adherence.

Mechanism of Action

Fostamatinib is a small molecule spleen tyrosine kinase (Syk) inhibitor. Syk affects cellular proliferation, differentiation, survival and immune regulation via IgG Fc-receptor signaling and is also linked to B-cell receptor signaling and autoantibody production (Bussel 2018). The major active metabolite of fostamatinib, R406, inhibits signal transduction of Fc-activating receptors and B-cell receptor and reduces antibody-mediated destruction of platelets.

Pharmacokinetics (Adult Data Unless Noted)

Onset of action: Median time to response (platelets ≥50,000/mm³): 15 days (Bussel 2018)

Distribution: R406: 256 (± 92) L

Protein binding: R406: 98.3%

Metabolism: Fostamatinib: Metabolized in the gut (by alkaline phosphatase) to R406 (active metabolite); R406: Extensively metabolized, primarily via oxidation (by CYP3A4) and glucuronidation (by UGT1A9)

Bioavailability: R406: 55%

Half-life elimination: R406: 15 (± 4.3) hours

Time to peak: R406: ~1.5 hours (range: 1 to 4 hours)

Excretion: Feces (R406: ~80%); Urine (R406: ~20%)

Brand Names: International

International Brand Names by Country

For country code abbreviations (show table)

(CZ) Czech Republic: Tavlesse;
(ES) Spain: Tavlesse;
(FI) Finland: Tavlesse;
(FR) France: Tavlesse;
(GB) United Kingdom: Tavlesse;
(IT) Italy: Tavlesse;
(NL) Netherlands: Tavlesse;
(NO) Norway: Tavlesse;
(PR) Puerto Rico: Tavalisse;
(SE) Sweden: Tavlesse

<800> Hazardous Drugs—Handling in Healthcare Settings. United States Pharmacopeia and National Formulary (USP 43-NF 38). Rockville, MD: United States Pharmacopeia Convention; 2020:74-92.
Bussel JB, Arnold DM, Boxer MA, et al. Long-term fostamatinib treatment of adults with immune thrombocytopenia during the phase 3 clinical trial program. Am J Hematol. 2019;94(5):546-553. doi:10.1002/ajh.25444 [PubMed 30784097]
Bussel J, Arnold DM, Grossbard E, et al. Fostamatinib for the treatment of adult persistent and chronic immune thrombocytopenia: results of two phase 3, randomized, placebo-controlled trials. Am J Hematol. 2018. doi: 10.1002/ajh.25125. [PubMed 29696684]
Tavalisse (fostamatinib) [prescribing information]. South San Francisco, CA: Rigel Pharmaceuticals, Inc; November 2020.
Tavalisse (fostamatinib) [product monograph]. Toronto, Ontario, Canada: Medison Pharma Canada Inc; July 2021.
US Department of Health and Human Services; Centers for Disease Control and Prevention; National Institute for Occupational Safety and Health. NIOSH list of antineoplastic and other hazardous drugs in healthcare settings 2016. https://www.cdc.gov/niosh/docs/2016-161/default.html. Updated September 2016. Accessed April 30, 2018.

Topic 117669 Version 101.0

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Fostamatinib: Drug information