Peginterferon alfa-2a

Summary

Peginterferon alfa-2a (Pegasys) is a pegylated recombinant human interferon alfa-2a used primarily for the treatment of chronic hepatitis B and chronic hepatitis C. PEGylation (attachment of 40 kDa branched polyethylene glycol) extends the half-life and reduces immunogenicity compared to standard interferon alfa-2a, allowing once-weekly subcutaneous dosing.

Mechanism of Action

Peginterferon alfa-2a binds to specific cell-surface receptors (IFNAR1/IFNAR2), activating the JAK-STAT signaling pathway (JAK1/TYK2), which induces transcription of interferon-stimulated genes. This leads to antiviral, antiproliferative, and immunomodulatory effects, including enhanced NK cell activity, macrophage phagocytosis, and inhibition of viral replication.

Routes of Administration

Goals & Uses

• Chronic Hepatitis C treatmentAntiviralHigh
• Chronic Hepatitis B treatmentAntiviralHigh
• ImmunomodulationImmunologyModerate
• Antineoplastic (melanoma, renal cell carcinoma)OncologyLow

Contraindications

• Severe psychiatric disorders (e.g., severe depression with suicidal ideation)NeuropsychiatricHigh
• Neonates and Infants (benzyl alcohol-containing formulations)PediatricHigh
• Pregnancy (when used with ribavirin)ReproductiveHigh
• Known hypersensitivity to interferon alfa or PEG componentsAllergic/ImmunologicHigh
• Autoimmune hepatitisHepatic / AutoimmuneHigh
• Decompensated hepatic disease (Child-Pugh B/C)HepaticHigh

Adverse Effects

• Flu-like symptoms (fatigue, fever, myalgia, headache)ConstitutionalCommon
• Hematologic toxicity (neutropenia, thrombocytopenia, anemia)HematologicCommon
• Neuropsychiatric effects (depression, irritability, insomnia, suicidality)NeuropsychiatricCommon
• Injection site reactionsLocalCommon
• Retinopathy / Optic neuropathyOphthalmologicUncommon
• Thyroid dysfunction (hypothyroidism or hyperthyroidism)EndocrineUncommon

Drug Interactions

• Theophylline / MethylxanthinesModerate
• TelbivudineHigh
• RibavirinModerate
• MethadoneModerate
• Myelosuppressive agents (e.g., azathioprine, hydroxyurea)High

Population Constraints

• PregnancyReproductive SafetyRelative
• Patients with pre-existing psychiatric disordersPsychiatricRelative
• Pediatric patients (<5 years)PediatricRelative
• Severe renal impairment (CrCl <30 mL/min)Organ ImpairmentRelative
• Patients with pre-existing cardiac diseaseCardiovascularRelative

Regulatory Status

• European UnionApprovedApproved: Chronic hepatitis C in adults and children ≥5 years, Chronic hepatitis B in adultsEMA approval granted; marketed as Pegasys by Roche. SmPC includes similar safety warnings as FDA label.
• United StatesApprovedApproved: Chronic hepatitis C (genotypes 1–6), in combination with ribavirin or as monotherapy, Chronic hepatitis B (HBeAg-positive and HBeAg-negative)FDA approved since October 2002. Black Box Warning for neuropsychiatric, autoimmune, ischemic, and infectious disorders. Use in HCV largely displaced by DAAs but remains approved.
• United KingdomApprovedApproved: Chronic hepatitis C, Chronic hepatitis BMHRA approved; post-Brexit retained approval. NICE guidance generally favors DAAs for HCV over pegylated interferon regimens.

FDA-approved since 2002 (Pegasys). Approved for chronic hepatitis C (with or without ribavirin) and chronic hepatitis B. Use in hepatitis C has largely been supplanted by direct-acting antivirals (DAAs). Risk Evaluation and Mitigation Strategy (REMS) previously required; current labeling includes Black Box Warnings for neuropsychiatric, autoimmune, ischemic, and infectious disorders.

Evidence & Sources

No sources recorded yet.