Azacitidine

Introduction Overview

Generic Name

azacitidine

Brand Name

Onureg

Dosage Form

oral tablet

Drug Class

Miscellaneous antineoplastics

Pharmacokinetics

Absorption:
Azacitidine, the active component of Onureg, is administered orally as tablets. After oral administration, azacitidine is absorbed via the gastrointestinal tract. The absolute bioavailability has shown variability, partly due to first-pass metabolism and instability in the gastrointestinal environment. Peak plasma concentrations are generally achieved within 1 to 2 hours after dosing. Food does not significantly affect the absorption of azacitidine, allowing it to be administered with or without food. Variability in absorption can occur due to patient-specific factors like gastrointestinal motility or concurrent medications.

Distribution:
Once absorbed, azacitidine distributes widely into body tissues and fluids. Plasma protein binding is relatively low, estimated around 15-30%, indicating a greater free drug fraction available for activity. The volume of distribution is moderately large, reflecting distribution into extravascular compartments including the bone marrow, which is the primary site of action. Azacitidine readily penetrates leukemic cells, exerting its cytotoxic and epigenetic effects. Tissue distribution studies further confirm its presence in critical hematopoietic tissues.

Metabolism:
Azacitidine undergoes extensive intracellular metabolism. It is rapidly converted into its active triphosphate form, 5-azacytidine triphosphate, which integrates into RNA. Furthermore, some azacitidine is metabolized to 5-aza-2'-deoxycytidine triphosphate, which incorporates into DNA leading to DNA hypomethylation and epigenetic modulation. Metabolic pathways include deamination via cytidine deaminase primarily in the liver, kidneys, and plasma. The drug’s metabolism is complex and critical for its antineoplastic activity, involving enzymatic processes that convert it into active nucleoside analogs.

Elimination:
The elimination of azacitidine and its metabolites occurs predominantly via renal excretion. The drug has a relatively short plasma half-life approximately 4 hours, reflecting rapid clearance. Urinary excretion accounts for a substantial portion of the administered dose, both as unchanged drug and metabolites. Renal impairment can affect elimination and may require clinical monitoring and dose adjustments. The drug is not significantly eliminated via feces or bile. Careful patient monitoring of renal function is important during therapy to prevent accumulation and toxicity.

Dosage Forms

Available Dosage Forms:
Onureg is available exclusively as oral tablets designed for a 28-day treatment cycle. Each tablet comes in a single strength with specific dosing instructions determined by healthcare providers. The tablets should be swallowed whole without crushing, chewing, or breaking to avoid skin or mucosal exposure to the active drug.

Dosages for Adults and Adolescents:
Onureg is indicated for adult patients with acute myeloid leukemia (AML) who have achieved first complete remission following intensive induction chemotherapy but are not able to complete intensive curative therapy. The typical regimen involves oral administration during the first 14 days of each 28-day cycle, taken once daily at approximately the same time. Precise dosing depends on physician’s assessment and patient tolerance; dose adjustments may be guided by adverse effects such as myelosuppression.

Specific Patient Populations:
Use of Onureg in pediatric patients under 18 years of age has not been established. In patients with renal or hepatic impairment, cautious use with close monitoring is recommended, given the reliance on renal clearance. Pregnant and lactating women are advised against using Onureg due to potential teratogenic effects and drug excretion in breast milk. The safety profile in geriatric populations aligns with adult data but requires vigilant monitoring of hematologic parameters.

Mechanism Of Action

Azacitidine, the active ingredient in Onureg, is a nucleoside analog of cytidine that functions primarily through epigenetic modulation and cytotoxicity. Once absorbed, azacitidine is phosphorylated into its active nucleotides, which are incorporated into RNA and DNA. Its incorporation into RNA disrupts RNA metabolism and protein synthesis, leading to impaired cellular functions and ultimately, apoptosis of malignant cells.

The primary mechanism underlying its antineoplastic effect is DNA hypomethylation. Incorporated into DNA as 5-aza-2'-deoxycytidine, azacitidine binds covalently to DNA methyltransferases (DNMTs), leading to their irreversible inhibition and subsequent degradation. The resultant DNA hypomethylation reactivates tumor suppressor genes and genes responsible for cell differentiation, reversing aberrant epigenetic silencing characteristic of leukemic cells.

At the cellular level, azacitidine induces differentiation and apoptosis of malignant hematopoietic cells. It disrupts the proliferation of leukemic blasts by interfering with DNA and RNA processes critical for cell division. Comparative to other hypomethylating agents such as decitabine, azacitidine exhibits additional RNA-directed cytotoxic effects, providing a distinct therapeutic profile.

Clinical studies underpinning the use of azacitidine demonstrate improved overall survival in AML patients in remission who cannot tolerate intensive therapy. Its epigenetic reprogramming helps maintain remission and suppress leukemic relapse, making Onureg a valuable oral maintenance therapy option.

Pharmacological Actions

Antineoplastic agent acting as a hypomethylating and cytotoxic nucleoside analog
Inhibits DNA methyltransferases leading to DNA hypomethylation and gene re-expression
Incorporates into RNA disrupting RNA metabolism and protein synthesis
Induces differentiation and apoptosis in malignant hematopoietic cells
Suppresses proliferation of leukemic blasts in acute myeloid leukemia
Epigenetic modulation reactivates tumor suppressor genes silenced in leukemogenesis
Provides maintenance therapy by preventing AML relapse post remission
Exerts direct cytotoxicity via RNA incorporation distinct from other hypomethylating agents
Demonstrates synergistic activity when combined with other agents in AML treatment protocols
Oral formulation enables convenient prolonged administration with improved patient adherence

Therapeutic Or Clinical Uses

Maintenance treatment of adults with acute myeloid leukemia (AML) in first complete remission
For patients who have undergone intensive induction chemotherapy but are unable to complete curative therapy
Used to prolong remission and prevent relapse in AML
Indicated when intravenous azacitidine formulations are not appropriate
Part of an emerging treatment strategy focusing on epigenetic modulation in hematologic malignancies
Used as a disease-modifying agent in elderly or frail AML patients
Improves overall survival rates in select AML patient populations
Potential off-label uses under investigation include other myelodysplastic syndromes (MDS)
Option for patients where bone marrow transplantation is contraindicated
Supports hematologic recovery and management in postremission settings
Available as oral maintenance therapy improving outpatient treatment feasibility
Adjunct to supportive care measures in AML management
Preferred for patients with co-morbidities limiting intensive chemotherapy
Used in clinical trials exploring combined regimens with other targeted agents
May be applied in personalized medicine approaches based on epigenetic profiles

Side Or Adverse Effects

Low blood cell counts leading to increased risk of infections, easy bruising, and bleeding
Common hematologic toxicity including neutropenia, thrombocytopenia, and anemia
Gastrointestinal symptoms such as nausea, vomiting, constipation, diarrhea, and stomach pain
Infections including lung infections and skin infections due to immunosuppression
Electrolyte disturbances such as low potassium presenting with cramps and irregular heartbeats
Fatigue, weakness, joint pain, and musculoskeletal discomfort
Dizziness and vertigo which may affect balance and safety
Allergic reactions including rash, hives, swelling, and difficulty breathing
Signs of liver toxicity including jaundice, dark urine, and upper abdominal pain
Potential kidney impairment evidenced by decreased urine output and swelling
Tumor lysis syndrome characterized by electrolyte imbalances and cardiac arrhythmias
Oral mucositis or sores which increase discomfort and infection risk
Injection site reactions are not applicable for oral Onureg but relevant for injectable forms
Possible skin exposure hazard from broken tablets causing irritation
Rare but serious fatal adverse events in severely immunocompromised patients

Precautions

Use effective contraception during treatment and for 6 months after last dose in women
Men should use contraception during treatment and for 3 months after last dose to prevent fetal harm
Avoid pregnancy due to high risk of teratogenicity and fetal harm
Avoid breastfeeding during treatment and for at least 1 week after last dose
Monitor renal and hepatic function routinely due to metabolism and elimination pathways
Frequent blood counts needed to monitor for myelosuppression and adjust dosing
Avoid contact with broken or crushed tablets to prevent mucocutaneous exposure
Use caution in patients with pre-existing infections or immunodeficiency
Inform healthcare provider promptly of any signs of infection or bleeding
Adjust dosage or discontinue therapy based on severity of adverse hematologic effects
Screen for allergic hypersensitivity prior to administration
Educate patients on symptoms of electrolyte imbalance and tumor lysis syndrome
Avoid use in pediatric patients as safety and efficacy are not established
Ensure adherence to administration schedule for optimal efficacy
Consider potential drug interactions when adding or discontinuing other medications

Warnings

Teratogenicity: Onureg can cause fetal harm when administered to pregnant women
Must use effective contraception in both male and female patients during and post treatment
Risk of severe myelosuppression leading to infections, bleeding, and anemia
Avoid in patients with known allergy to azacitidine or any tablet components
Not a substitute for injectable azacitidine formulations; different indications and dosing
Avoid breastfeeding due to potential drug excretion in breast milk and risk to infant
Monitor closely for signs of infection, including fever, cough, or unexplained symptoms
Risk of tumor lysis syndrome requiring close monitoring of electrolytes and cardiac status
Take tablets whole; broken or crushed tablets may cause local toxicity if contact occurs
Risk of hepatic and renal toxicity necessitates baseline and ongoing function tests
Emergency medical help required for signs of severe allergic reactions
Use cautiously in patients with significant kidney or liver impairment
Do not double doses if a dose is missed; follow prescribing instructions strictly
Avoid exposure to people with contagious infections due to immunosuppression risk
Potential for dizziness warrants caution when performing activities requiring alertness

Contraindication

Known hypersensitivity to azacitidine or any of the formulation components
Pregnant women due to risk of fetal harm
Patients unable to comply with contraceptive requirements
Severe untreated infections where immunosuppression would be hazardous
Patients with severe hepatic or renal impairment without adequate monitoring
Use of broken or crushed tablets leading to mucocutaneous exposure
Patients with a history of severe allergic reactions to nucleoside analogs
Concurrent use of non-compatible antineoplastics without specialist supervision
Known active bleeding disorders that contraindicate myelosuppressive therapy
Pediatric patients due to lack of safety and efficacy data

Drug Interactions

Concurrent use with other myelosuppressive agents may exacerbate cytopenias
Potential interactions with nephrotoxic drugs requiring renal function monitoring
Co-administration with strong CYP enzyme inducers or inhibitors may alter azacitidine metabolism
Use with anticoagulants increases bleeding risk due to thrombocytopenia
Interactions with antiemetics to manage nausea and vomiting during therapy
Possible interaction with drugs affecting potassium levels contributing to electrolyte imbalance
Herbal supplements with unknown effects on bone marrow should be avoided
Vitamins or supplements that may interfere with cell proliferation or apoptosis pathways
Drugs that impair immune function may heighten infection risk
Medications metabolized via cytidine deaminase pathways may influence azacitidine levels
No significant interaction with food; Onureg can be taken with or without meals
Avoid live vaccines due to immunosuppressive effects of azacitidine
Polypharmacy requires careful review to avoid overlapping toxicities
Monitor for increased toxicity when combined with other epigenetic modulators
Consult healthcare provider before starting or stopping any concomitant medications

Preparations Of The Drug

Onureg is supplied as oral tablets for administration in 28-day cycles
Tablets are packaged with moisture-absorbing preservatives to maintain stability
Each tablet contains a specified dose of azacitidine to be taken whole without crushing
Storage recommended at room temperature away from moisture and heat
Tablets supplied in child-resistant containers with patient information leaflets
Medication guides provide detailed instructions regarding dosing schedules and precautions
Not interchangeable with azacitidine injections (Vidaza) which have different dosing and indications
Available through prescription only with strict adherence to oncologist prescribing
Packaging includes warnings about hazardous exposure to broken tablets
Standardized manufacturing ensures consistent potency and quality control
Supplementary antiemetic medications may be dispensed concurrently to manage side effects
May be part of combination chemotherapy regimens prescribed by oncology specialists
Patient assistance programs or coupons may be available to support access
Regular supply provided in accordance with treatment cycles for outpatient care
Full prescribing information available to healthcare professionals for reference