Quizartinib

Introduction Overview

Generic Name

quizartinib

Brand Name

Vanflyta

Dosage Form

oral tablet (17.7 mg; 26.5 mg)

Drug Class

Multikinase inhibitors

Pharmacokinetics

Absorption:
Quizartinib is administered orally as a tablet and exhibits substantial absorption through the gastrointestinal tract. While specific bioavailability data from human trials remain limited, clinical evidence indicates that quizartinib’s absorption allows for effective systemic plasma concentrations adequate for therapeutic action in acute myeloid leukemia. The drug can be taken with or without food without significant alteration in its pharmacokinetic profile. The presence of food marginally delays the time to peak concentration but does not significantly affect overall absorption. Factors such as gastrointestinal pH and motility may influence absorption; however, no major clinically significant interactions have been documented.

Distribution:
After absorption, quizartinib demonstrates extensive tissue distribution due to its lipophilic nature. It has a considerable volume of distribution, indicating penetration beyond vascular compartments into extravascular tissues. Plasma protein binding is high, predominantly to albumin and alpha-1-acid glycoprotein, which may influence free drug concentration and pharmacodynamic effects. Distribution into sanctuary sites such as the central nervous system appears limited due to blood-brain barrier constraints. Distribution kinetics suggest sustained tissue residence which supports once-daily dosing. No significant accumulation in adipose tissue has been reported.

Metabolism:
Quizartinib undergoes extensive hepatic metabolism, primarily via cytochrome P450 isoenzymes CYP3A4 and to a lesser extent CYP3A5. The metabolic pathways involve oxidative heterocyclic ring formation and subsequent conjugation reactions, including glucuronidation and sulfation. Metabolites have not demonstrated significant pharmacologic activity. The potential for drug interactions through CYP3A-mediated metabolism is high, necessitating caution when co-administering potent CYP3A inhibitors or inducers, which can respectively increase toxicity or reduce efficacy. Metabolic capacity may vary based on genetic polymorphisms affecting CYP enzymes and liver function.

Elimination:
The elimination of quizartinib primarily occurs via hepatic clearance with excretion of metabolites in feces and urine. The terminal half-life supports once-daily dosing and ranges between 30 to 50 hours in adult patients. Renal excretion of unchanged drug is minimal, reducing the impact of renal impairment on clearance; however, hepatic impairment may affect elimination. Monitoring of liver function during therapy is important to adjust dosing if necessary. Steady-state concentrations are achieved within approximately two weeks of daily dosing. No significant accumulation is expected beyond steady state with standard dosing regimens.

Dosage Forms

Available Dosage Forms:
Quizartinib is available exclusively as an oral tablet formulated in two distinct strengths: 17.7 mg and 26.5 mg tablets. These formulations are designed to provide flexible dosing regimens tailored to patient needs while maintaining compliance and ease of administration.

Dosages for Adults and Adolescents:
The typical dosing protocol for adults with acute myeloid leukemia involves once-daily oral administration of quizartinib. Initial doses are individually titrated based on patient response, tolerability, and concurrent therapies. Therapy usually begins with a lower dose, gradually escalating to the target therapeutic dose, often utilizing the 17.7 mg and 26.5 mg tablets to achieve precise dosing. Treatment cycles are defined according to hematologic response and side effect profiles, with potential dose adjustments or interruptions when clinically indicated.

Specific Patient Populations:
Quizartinib dosing requires careful consideration in special populations. Its use in patients with hepatic impairment mandates caution due to metabolism via hepatic cytochrome P450 enzymes; dose reductions may be necessary. Renal impairment has less impact but should still prompt monitoring. Pediatric dosing data are insufficient, restricting use primarily to adults. Geriatric patients may have altered pharmacokinetics and increased susceptibility to cardiac side effects, thus requiring close monitoring. Pregnancy and lactation contraindicate quizartinib use due to teratogenic potential. The drug’s availability is restricted to certified pharmacies and requires patient enrollment in a special program to ensure safe administration and monitoring.

Mechanism Of Action

Quizartinib is a potent and highly selective oral multikinase inhibitor primarily targeting the FMS-like tyrosine kinase 3 (FLT3) receptor, a type III receptor tyrosine kinase frequently mutated and overexpressed in acute myeloid leukemia (AML). In particular, quizartinib exhibits high affinity for the FLT3 internal tandem duplication (ITD) mutation, which is constitutively active and drives leukemic cell proliferation and survival. By selectively binding to the ATP-binding site within the FLT3 tyrosine kinase domain, quizartinib inhibits autophosphorylation and downstream signal transduction.

At the cellular level, this inhibition abrogates critical signaling pathways involved in leukemogenesis, including the PI3K/AKT/mTOR and RAS/RAF/MEK/ERK cascades. This suppression leads to decreased proliferation, induction of apoptosis, and inhibition of aberrant survival signals in malignant myeloid cells. Additionally, quizartinib blocks other kinases implicated in oncogenic processes, such as KIT, thereby amplifying its antineoplastic effects.

Biochemically, quizartinib’s selective inhibition reduces phosphorylation of FLT3 and downstream effectors, impairing cellular processes that promote leukemic cell growth, chemoresistance, and angiogenesis. This targeted mechanism improves therapeutic index by sparing non-malignant cells, which contributes to a more favorable toxicity profile compared to conventional chemotherapy.

Clinically, the selective targeting of FLT3 ITD mutations by quizartinib has demonstrated improved remission rates and progression-free survival in patients with relapsed or refractory AML harboring these mutations. Studies have revealed its efficacy as monotherapy and in combination regimens, establishing quizartinib as a valuable agent in precision oncology. Its mechanism contrasts with less selective multikinase inhibitors, underscoring its role as a frontline targeted therapy option supported by extensive molecular and clinical research.

Pharmacological Actions

Selective inhibition of FLT3 receptor tyrosine kinase, including FLT3 internal tandem duplication mutants, leading to blockade of leukemic cell proliferation.
Suppression of downstream oncogenic signaling pathways involved in cell survival and growth, such as PI3K/AKT/mTOR and RAS/RAF/MEK/ERK.
Induction of apoptosis in malignant myeloid blast cells by interrupting aberrant kinase activity.
Inhibition of other kinases involved in hematopoiesis and oncogenesis such as KIT, contributing to antileukemic effects.
Reduction of leukemic cell survival and chemoresistance, enhancing sensitivity to concomitant therapeutic agents.
Selective targeting reduces toxicity to normal hematopoietic progenitors, improving therapeutic index.
Oral bioavailability allowing convenient once-daily dosing with sustained drug levels.
Potential to overcome resistance mechanisms mediated by FLT3 kinase domain mutations due to its potent binding affinity.
Modulation of immune microenvironment through indirect effects on leukemic cell population dynamics.
Inhibition of aberrant angiogenesis contributing to leukemia progression.

Therapeutic Or Clinical Uses

Treatment of acute myeloid leukemia (AML) in adults, particularly AML with FLT3 internal tandem duplication mutations.
Monotherapy or in combination with other chemotherapeutic agents for relapsed or refractory AML.
Targeted therapy option for AML patients unsuitable for or refractory to conventional chemotherapy.
Use within specialized treatment programs requiring patient registration and monitoring.
Adjunct treatment aimed at reducing leukemic burden prior to hematopoietic stem cell transplantation.
Potential investigational use in other hematologic malignancies exhibiting aberrant FLT3 expression.
Off-label use in clinical trials exploring efficacy in FLT3-mutated myelodysplastic syndromes.
Management of AML patients with high risk of relapse due to FLT3-ITD positive mutation.
Incorporated into combination regimens aimed at improving remission duration and overall survival.

Side Or Adverse Effects

Nausea, vomiting, and stomach discomfort including pain and upset stomach.
Diarrhea and loss of appetite leading to potential nutritional deficits.
Fungal infections indicating immunosuppressive effects.
Sepsis and serious infections due to neutropenia or immunosuppression.
Eye irritation manifesting as redness or discomfort.
Nosebleeds resulting from thrombocytopenia or mucosal fragility.
Cold-like symptoms including stuffy nose, sneezing, and sore throat.
Herpes virus reactivation or infection.
Sleep disturbances including insomnia or trouble falling asleep.
Low platelet counts increasing bleeding risk and bruising.
Electrolyte imbalances, particularly hypokalemia (low potassium) and hypomagnesemia (low magnesium).
Altered liver function tests suggestive of hepatotoxicity.
Abnormal electrocardiogram changes, including QT prolongation and risk of arrhythmias.
Low blood cell counts (anemia, neutropenia) causing fever, chills, tiredness, mouth and skin sores, and susceptibility to infections.
Serious heart problems such as ventricular arrhythmias, torsades de pointes, and potential sudden cardiac death.

Precautions

Use only under enrollment in certified pharmacy programs with monitoring requirements.
Avoid administration in patients with known hypersensitivity to quizartinib or its excipients.
Careful baseline and ongoing monitoring of electrolytes, especially potassium and magnesium levels.
Perform and frequently monitor electrocardiograms to detect QT interval prolongation.
Use caution and monitor cardiac function in patients with history of arrhythmias or heart disease.
Do not use in patients with long QT syndrome or a history of torsades de pointes.
Dose modification or interruption may be required if severe side effects or ECG abnormalities develop.
Avoid concurrent use with other QT-prolonging agents to reduce risk of cardiac arrhythmias.
Inform patients of the risk of serious heart problems and instruct them to report symptoms such as lightheadedness, syncope, palpitations, or chest pain.
Requires pregnancy testing and effective contraception for women of childbearing potential during therapy and for at least 7 months after last dose.
Men should use contraception during therapy and for at least 4 months after last dose to prevent fetal exposure.
Discontinue breastfeeding during treatment and for at least one month post-therapy due to unknown effects in infants.
Monitor blood counts regularly due to risk of cytopenias.
Avoid St. John’s Wort and other CYP3A4 inducers or inhibitors that may alter quizartinib levels.
Use caution in patients with hepatic impairment; dose adjustments may be necessary.

Warnings

Serious cardiac toxicity can occur, including QT prolongation, ventricular arrhythmias, torsades de pointes, and sudden death.
Use cautiously when co-administered with medications known to prolong QT interval or affect electrolyte balance.
Immediate medical evaluation required if symptoms of irregular heartbeat, dizziness, fainting, or gastrointestinal symptoms such as diarrhea or vomiting develop.
Risk of severe infections including sepsis due to immunosuppressive effects.
Risk of hematologic toxicities including severe neutropenia, thrombocytopenia, and anemia.
Potential teratogenic effects necessitate strict contraception and pregnancy prevention strategies.
Not indicated for use during pregnancy or breastfeeding due to risk of fetal harm.
Must be dispensed under a restricted risk evaluation and mitigation strategy (REMS) program with certified pharmacies and prescribers.
Dose reduction, interruption, or discontinuation may be warranted based on severity of toxicities.
Patients should be counseled not to alter dosage without physician consultation.
Avoid abrupt discontinuation, which may lead to disease progression or rebound effects.
Potential interactions with herbal supplements like St. John’s Wort, which can reduce drug efficacy.
Monitor liver function tests to detect and manage hepatotoxicity early.
Patients should be advised against driving or operating machinery if experiencing dizziness or cardiac symptoms.
Frequent laboratory and ECG assessments are necessary, particularly during initiation and dose adjustments.

Contraindication

Known hypersensitivity to quizartinib or any component of the formulation.
Patients with documented long QT syndrome or familial history of long QT syndrome.
History of ventricular arrhythmias such as torsades de pointes or other life-threatening ventricular tachyarrhythmias.
Severe electrolyte abnormalities including hypokalemia and hypomagnesemia not corrected prior to treatment.
Concomitant use with medications contraindicated due to additive QT prolongation risk.
Pregnancy, due to potential teratogenic and fetal toxic effects.
Breastfeeding women, due to unknown risk to nursing infants.
Severe hepatic impairment without capacity for close monitoring and dose adjustment.
Patients unable to comply with program restrictions and monitoring requirements.
Patients with uncontrolled infections or significant immunosuppression may be at increased risk for adverse effects.
Known significant drug interactions with CYP3A4 inducers or inhibitors that cannot be safely managed.

Drug Interactions

Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole) may increase quizartinib plasma concentrations, elevating toxicity risk.
CYP3A4 inducers (e.g., rifampin, carbamazepine, St. John’s Wort) can reduce quizartinib efficacy by lowering plasma levels.
Other QT-prolonging agents (e.g., amiodarone, sotalol, certain antipsychotics) increase risk of torsades de pointes and sudden cardiac death.
Drugs that alter electrolyte balance (e.g., diuretics causing hypokalemia or hypomagnesemia) can exacerbate cardiac risks.
Medications causing myelosuppression (e.g., other chemotherapeutics) may have additive hematologic toxicity when combined with quizartinib.
Concomitant use with strong P-glycoprotein inhibitors or inducers may affect distribution and clearance.
Antifungal agents (azoles) impacting CYP3A4 metabolism require dose adjustments or close monitoring.
Co-administration with anticoagulants or antiplatelet agents may require bleeding risk evaluation due to thrombocytopenia.
Caution with other hepatically metabolized drugs due to potential for competitive metabolism and altered plasma levels.
Herbal supplements, particularly those modulating cytochrome P450 enzymes, should be avoided.
Use with medications causing bradycardia or heart block necessitates cautious cardiac monitoring.
Pharmacodynamic interactions with immunosuppressants could increase infection risk.
Combination with other multikinase inhibitors demands close clinical surveillance for overlapping toxicities.
Avoid grapefruit and grapefruit juice, which inhibit CYP3A4 and may increase drug exposure.
Potential drug-food interactions are minimal but maintaining consistent dietary habits is recommended.

Preparations Of The Drug

Oral tablets available in 17.7 mg strength (round, yellow tablets).
Oral tablets available in 26.5 mg strength (round, orange tablets).
Packaged in blister cards ensuring stability and dose tracking.
Requires storage at controlled room temperature, protected from moisture and heat.
Supplied exclusively through a restricted program due to safety profile.
Dispensed only by certified pharmacies enrolled in REMS or equivalent programs.
Accompanied by patient education materials detailing dosing and side effect monitoring.
Packaging includes clear labeling regarding teratogenic risks and contraception requirements.
No parenteral or alternative formulations authorized as yet.
Supplied with prescription-only status emphasizing controlled medical supervision.