Fedratinib (Monograph)

Brand name: Inrebic
Drug class: Antineoplastic Agents

Medically reviewed by Drugs.com on May 10, 2025. Written by ASHP.

[Web]

Introduction

Antineoplastic agent; selective inhibitor of Janus kinase (JAK) 2 and fms-like tyrosine kinase (Flt) 3.

Uses for Fedratinib

Myelofibrosis

Treatment of adults with intermediate-2 or high-risk primary or secondary myelofibrosis, including post-polycythemia vera or post-essential thrombocythemia (designated an orphan drug by FDA for these conditions). Substantially reduces splenomegaly and symptom burden compared with placebo.

Patients with low- or intermediate-risk MF who lack significant symptoms may be managed with observation alone. However, if cytoreductive therapy is indicated in low- to intermediate-risk patients, hydroxyurea is often recommended as first-line treatment. Historically, MF-associated splenomegaly was treated with hydroxyurea; however, some experts recommend JAK inhibitors in patients with intermediate or high-risk disease who are not eligible for allogeneic stem cell transplantation, in those who are unresponsive to or cannot tolerate hydroxyurea, and to reduce spleen size prior to allogeneic stem cell transplantation.

Fedratinib Dosage and Administration

General

Pretreatment Screening

• Obtain thiamine levels and assess nutritional status prior to initiating therapy. Do not initiate fedratinib in patients with thiamine deficiency. Correct thiamine levels prior to initiating and during fedratinib therapy.

• Obtain CBC with platelets, serum amylase and lipase concentrations, and hepatic and renal function (S_cr and BUN) at baseline.

Patient Monitoring

• Monitor thiamine levels periodically during therapy and as clinically indicated.

• Monitor CBC with platelets, serum amylase and lipase concentrations, and hepatic and renal function (S_crand BUN) periodically during therapy and as clinically indicated.

• Monitor for the development of major adverse cardiac events (MACE), thrombosis, and secondary malignancies during therapy.

Premedication and Prophylaxis

• Consider prophylactic antiemetic therapy (e.g., 5-HT₃ serotonin receptor antagonist).

• Administer prophylactic thiamine 100 mg orally daily during treatment.

Administration

Oral Administration

Administer once daily without regard to food; tolerability (i.e., reduced nausea or vomiting) increased with a high-fat meal.

If a dose is missed, administer next scheduled dose the following day; do not administer an additional dose to replace the missed dose.

Do not initiate in patients receiving ruxolitinib until ruxolitinib has been discontinued by gradual taper.

Dosage

Available as fedratinib hydrochloride; dosage expressed in terms of fedratinib.

Adults

Myelofibrosis

Oral

400 mg once daily in those with baseline platelet count ≥50,000/mm³.

Dosage Modification for Toxicity

Oral

Adverse effects may require temporary interruption, dosage reduction, and/or permanent discontinuance.

Discontinue fedratinib in patients unable to tolerate a 200 mg daily dose.

Hematologic Toxicity

Oral

If grade 3 thrombocytopenia with active bleeding or grade 4 thrombocytopenia occurs, interrupt fedratinib therapy. If thrombocytopenia resolves to grade 2 or less or baseline, resume fedratinib at 100 mg daily below the last given dose.

If grade 4 neutropenia occurs, interrupt fedratinib therapy. If neutropenia resolves to grade 2 or less or baseline, resume fedratinib at 100 mg daily below the last given dose.

In patients who become transfusion-dependent, consider dosage reduction.

GI Effects

Oral

If grade 3 or greater nausea, vomiting, or diarrhea occurs and is not responsive to supportive therapy within 48 hours, interrupt fedratinib therapy. When toxicity resolves to grade 1 or less or baseline, resume fedratinib at 100 mg daily below the last given dose.

Hepatic Toxicity

Oral

For grade 3 or greater ALT, AST, or bilirubin concentration elevations, interrupt fedratinib therapy. If toxicity resolves to grade 1 or less or baseline, resume fedratinib at 100 mg below the last given dose and monitor serum ALT, AST, and total and direct bilirubin concentrations more frequently.

If grade 3 or greater ALT, AST, or bilirubin concentration elevations recur, discontinue fedratinib therapy.

Wernicke Encephalopathy

Oral

If Wernicke encephalopathy suspected, promptly discontinue fedratinib and administer IV thiamine. Monitor thiamine levels until symptoms resolve or improve and thiamine levels reach normal limits.

Pancreatic Enzyme Elevation

Oral

For grade 3 or greater serum amylase and/or lipase concentration elevations, interrupt fedratinib therapy. If toxicity resolves to grade 1 or less or baseline, resume fedratinib at 100 mg daily below the last given dose.

Other Toxicity

Oral

If grade 3 or greater adverse reactions occur, interrupt fedratinib therapy. If toxicity resolves to grade 1 or less or baseline, resume fedratinib at 100 mg daily below the last given dose.

Concomitant Use of Drugs Affecting Hepatic Microsomal Enzymes

Since strong CYP3A4 inhibitors may increase exposure to fedratinib, consider selection of an alternative drug with less CYP3A4 inhibition potential. Alternatively, reduce dosage to 200 mg once daily when coadministering a strong CYP3A4 inhibitor. If concomitant use of the strong CYP3A4 inhibitor is discontinued, gradually return dosage of fedratinib to dosage used prior to initiation of the strong CYP3A4 inhibitor according to the following schedule: 300 mg once daily for 2 weeks then an increase to 400 mg once daily thereafter as tolerated.

Special Populations

Hepatic Impairment

No specific dosage recommendations for patients with preexisting mild to severe hepatic impairment; however, hepatic toxicity may occur with therapy requiring temporary interruption, dosage adjustment, or discontinuation.

Renal Impairment

Severe renal impairment (Cl_cr 15–29 mL/minute): Reduce dosage to 200 mg once daily.

Moderate renal impairment (Cl_cr 60–89 mL/minute): No initial dosage adjustment required. Closely monitor for signs of toxicity and adjust dosage as appropriate .

Mild renal impairment (Cl_cr 30–59 mL/minute): No dosage adjustment required.

Geriatric Patients

No specific dosage recommendations at this time.

Cautions for Fedratinib

Contraindications

• None.

Warnings/Precautions

Warnings

Encephalopathy

Serious, sometimes fatal, encephalopathy reported (See Boxed Warning). Wernicke encephalopathy, a neurologic emergency caused by thiamine deficiency, also reported.

If changes in mental status, confusion, or memory impairment occur, interrupt fedratinib therapy and promptly evaluate for encephalopathy (i.e., neurologic examination, radiographic imaging, assessment of thiamine levels). If encephalopathy is suspected, promptly discontinue fedratinib and administer IV thiamine. Monitor thiamine levels until symptoms resolve or improve and thiamine levels reach normal limits.

Assess thiamine levels and nutritional status prior to initiating therapy, periodically during therapy, and as clinically indicated. Do not initiate fedratinib therapy in patients with thiamine deficiency. Correct thiamine levels prior to initiating and during therapy. Administer prophylactic oral thiamine to all patients during therapy.

Other Warnings and Precautions

Hematologic Effects

Adverse hematologic effects (i.e., anemia, thrombocytopenia, neutropenia) reported. Median time to initial onset of grade 3 anemia or thrombocytopenia is approximately 2 or 1 month(s), respectively. Nadir hemoglobin concentrations occur after 12–16 weeks of fedratinib therapy; partial recovery and stabilization occurs after 16 weeks. Approximately one-half of patients who developed anemia required RBC transfusions and 3.1% of patients who developed thrombocytopenia required platelet transfusions.

Monitor CBCs at baseline, periodically during therapy, and then as clinically indicated. Temporary interruption of therapy, dosage reduction, or treatment discontinuance may be necessary based on severity of the toxicity.

GI Effects

Diarrhea, nausea, and vomiting occur frequently, generally within 2 weeks of initiating therapy.

Consider prophylactic antiemetic therapy (e.g., 5-HT₃ serotonin receptor antagonist). If diarrhea occurs, promptly initiate antidiarrheal therapy at onset of diarrhea.

Temporary interruption of therapy, dosage reduction, or treatment discontinuance may be necessary based on severity of the toxicity. Monitor thiamine levels and correct as needed.

Hepatic Toxicity

Serum ALT and/or AST elevations, generally within 3 months of initiating therapy, reported.

Monitor liver function tests at baseline, periodically during therapy, and as clinically indicated. Temporary interruption followed by dosage reduction or treatment discontinuance may be necessary based on severity of the toxicity.

Pancreatic Enzyme Elevation

Serum amylase and/or lipase elevations, generally within 1 month of initiating therapy, reported. Pancreatitis also reported.

Monitor serum amylase and lipase concentrations at baseline, periodically during therapy, and as clinically indicated. Temporary interruption followed by dosage reduction or treatment discontinuance may be necessary based on severity of the toxicity.

Major Adverse Cardiac Events (MACE)

An increased risk of MACE observed in patients with rheumatoid arthritis treated with another Janus Kinase inhibitor. Advise patients of benefits and risks of initiating or continuing fedratinib, particularly for current or past smokers or those who have other cardiovascular risk factors. Inform patients about symptoms of serious cardiovascular events and steps to take if such symptoms occur.

Thrombosis

An increased risk of thrombosis observed in patients with rheumatoid arthritis treated with another Janus Kinase inhibitor. Evaluate patients with thrombosis symptoms promptly and treat appropriately.

Secondary Malignancies

An increased risk of lymphoma and other malignancies, excluding nonmelanoma skin cancer, observed in patients with rheumatoid arthritis treated with another Janus Kinase inhibitor. Current or past smokers are at an additional increased risk for secondary malignancy development. Advise patients of benefits and risks of initiating or continuing fedratinib, particularly for those with a known malignancy (other than nonmelanoma skin cancer), those who develop a malignancy, and those who are current or past smokers.

Specific Populations

Pregnancy

May cause fetal harm; teratogenicity demonstrated in animals.

Consider potential risks and benefits of drug to mother and potential risk to fetus prior to initiating therapy in pregnant women.

Lactation

Not known whether fedratinib or its metabolites are distributed into human milk or affect nursing infants or milk production. Discontinue nursing during therapy and for ≥1 month after discontinuance of the drug.

Pediatric Use

Safety and efficacy not established.

Geriatric Use

No overall differences in safety or efficacy relative to younger adults.

Hepatic Impairment

Mild to severe hepatic impairment does not have clinically meaningful effects on fedratinib pharmacokinetics.

Renal Impairment

Pharmacokinetics of fedratinib not altered in patients with mild renal impairment (Cl_cr 60–89 mL/minute).

Increased systemic exposure in individuals with moderate or severe renal impairment (Cl_cr 15–59 mL/minute). Reduce dosage in patients with preexisting severe renal impairment.

Grade 3 or 4 adverse effects requiring dosage modification reported more frequently in patients with moderate renal impairment; closely monitor patients with preexisting moderate renal impairment for signs of fedratinib toxicity and adjust dosage as appropriate.

Common Adverse Effects

Adverse effects reported in ≥20% of patients: Diarrhea, nausea, anemia, vomiting.

Drug Interactions

Metabolized principally by CYP3A4 and, to a lesser extent, by CYP2C19 and flavin-containing monooxygenase 3 (FMO3).

In vitro, inhibits P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion transport protein (OATP) 1B1, OATP1B3, organic cation transporter (OCT) 2, multidrug and toxin extrusion (MATE) transporter 1, and MATE2K; not an inhibitor of bile salt export pump (BSEP), multidrug resistance protein (MRP) 2, organic anion transporter (OAT) 1, and OAT3.

Substrate of P-gp, but not a substrate of BCRP, BSEP, OATP1B1, OATP1B3, MRP, or MRP2.

Drugs Affecting Hepatic Microsomal Enzymes

Strong CYP3A4 inhibitors: Possible increased systemic exposure to, and increased toxicity of, fedratinib. Consider alternative drug with less CYP3A4 inhibition potential. If concomitant use of a strong CYP3A4 inhibitor cannot be avoided, reduce fedratinib dosage to 200 mg once daily. If the strong CYP3A4 inhibitor is discontinued, increase fedratinib dosage to 300 mg once daily for 2 weeks followed by an increase to 400 mg once daily, as tolerated.

Combined CYP3A4 and 2C19 inhibitors: Concomitant use may result in increased systemic exposure to fedratinib and possible toxicity. May require more intensive safety monitoring and a potential dose modification if adverse reactions occur.

Moderate and strong CYP3A4 inducers: Concomitant use may result in decreased systemic exposure to fedratinib and possible reduced effectiveness of the drug. Avoid concomitant use.

Drugs Metabolized by Hepatic Microsomal Enzymes

Substrates of CYP3A4, 2C19, or 2D6: Possible increased systemic exposure to, and increased toxicity of, the substrate drug. If fedratinib used concomitantly with a CYP3A4, 2C19, or 2D6 substrate, monitor for toxicity of substrate drug and adjust dosage of substrate drug as appropriate.

Substrates of OCT2 and MATE1/2-K: Possible reduced renal clearance of the substrate drug. If fedratinib used concomitantly with a OCT2 or MATE1/2-K substrate, monitor for adverse reactions and consider dose modifications.

Specific Drugs

Fedratinib Pharmacokinetics

Absorption

Bioavailability

Systemic exposure increases in a dose-proportional manner over a dosage range of 300–500 mg once daily.

Peak plasma concentrations achieved within 2–4 hours following administration of fedratinib 400 mg once daily.

Steady-state concentrations achieved in 15 days. Mean accumulation ratio is 3- to 4-fold.

Food

Administration with a low-fat or high-fat meal increased peak plasma concentrations and AUC by 14 and 24%, respectively.

Special Populations

Mild (total bilirubin concentration not exceeding ULN with AST concentration exceeding ULN, or total bilirubin concentration >1 times ULN, but not >1.5 times ULN, with any AST concentration) or moderate (total bilirubin concentration >1.5 times ULN, but not >3 times ULN, with any AST concentration) hepatic impairment: No effect on pharmacokinetics of fedratinib.

Severe hepatic impairment (total bilirubin concentration >3 times ULN with any AST concentration): Pharmacokinetics not studied.

Mild renal impairment (Cl_cr 60–89 mL/minute): No effect on pharmacokinetics of fedratinib.

Moderate (Cl_cr 30–59 mL/minute) or severe renal impairment (Cl_cr15–29 mL/minute): Systemic exposure increased by 1.5- or 1.9-fold, respectively.

Age (20–95 years), sex, body weight, and race: No substantial effect on pharmacokinetics.

Distribution

Extent

Not known whether fedratinib is distributed into human milk.

Plasma Protein Binding

≥92%.

Elimination

Metabolism

Metabolized principally by CYP3A4 and, to a lesser extent, by 2C19 and FMO3.

Elimination Route

Eliminated primarily in feces (77%; 23% as unchanged drug) and to a lesser extent in urine (5%; 3% as unchanged drug).

Half-life

Effective half-life: 41 hours.

Terminal half-life: Approximately 114 hours.

Stability

Storage

Oral

Capsules

<30°C.

Actions

• Selectively inhibits JAK2 and Flt 3.

• Myeloproliferative neoplasms, including myelofibrosis and polycythemia vera, associated with dysregulated JAK2 signaling. Majority of polycythemia vera myelofibrosis and 50–60% of primary myelofibrosis and essential thrombocythemia myelofibrosis carry JAK2V617F mutation, which results in constitutive activation of JAK-STAT signaling pathway and subsequent abnormal hematopoiesis and dysregulation of inflammatory cytokines and chemokines.

• Competitively inhibits at ATP-binding site of wild-type JAK2 and JAK2V617F, preventing phosphorylation and activation of STATs.

• In vitro, greater inhibitory potency at JAK2 relative to JAK1, JAK3, and TYK2.

• In vitro, decreased phosphorylation of STAT3/5, inhibited cell proliferation, and induced apoptosis.

• Inhibits phosphorylation of STAT3/5 and improves survival, WBCs, hematocrit, splenomegaly, and fibrosis in mouse models of myeloproliferative disease harboring JAK2V617F.

• Causes dose-dependent inhibition of cytokine-induced STAT3 phosphorylation in whole blood of patients with myelofibrosis. Maximal inhibition observed approximately 2 hours after initial dose of drug; activity returns to near baseline by 24 hours. Inhibition at steady state similar to maximal inhibition observed following the initial dose.

Advice to Patients

• Advise patients that if they miss a dose of fedratinib, they should take their prescribed dose at the next scheduled time; an additional dose should not be administered to replace the missed dose.

• Risk of encephalopathy, including Wernicke encephalopathy. Stress importance of monitoring of thiamine levels. Advise patients to seek emergency medical attention if changes in mental status (e.g., confusion, drowsiness, memory impairment), cerebellar abnormalities (e.g., ataxia), or ophthalmic abnormalities (e.g., diplopia, nystagmus) occur. Stress importance of promptly informing clinician if nausea, vomiting, diarrhea, and weight loss unresponsive to appropriate treatment and resulting in malnutrition and low thiamine levels occur. Instruct patients that they should receive prophylaxis with thiamine 100 mg orally daily while receiving fedratinib.

• Inform patients of the risk of thrombocytopenia or anemia and the importance of monitoring CBCs prior to and during fedratinib therapy. Inform clinician if bleeding or bruising occurs.

• Inform patients of the risk of diarrhea, nausea, or vomiting unresponsive to appropriate treatment.

• Inform patients of the risk of hepatotoxicity and the importance of liver function test monitoring prior to and during fedratinib therapy.

• Inform patients of the risk of elevated amylase or lipase concentrations and the importance of pancreatic enzyme monitoring prior to and during fedratinib therapy.

• Inform patients of the risk of major adverse cardiac events, thrombosis, and secondary malignancies with therapy and the importance of monitoring patients for symptoms of their development.

• Advise patients to inform clinicians if they are or plan to become pregnant or plan to breast-feed. Advise patients not to breast-feed during and for ≥1 month after discontinuance of therapy.

• Stress importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

• Inform patients of other important precautionary information.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care. For further information on the handling of antineoplastic agents, see the ASHP Guidelines on Handling Hazardous Drugs at [Web].

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Distribution is restricted. Contact manufacturer for additional information.

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