Table 1.
Spectrum and incidence of PegIFN-α–associated adverse reactions in chronic hepatitis B.
| Adverse reaction category | Specific manifestations | Estimated incidence | Subtype considerations (PegIFN-α-2a vs. -2b) | Key supporting references |
|---|---|---|---|---|
| Flu-like Syndrome | Fever, chills, myalgia, headache, profound fatigue | 60–80% | No major differences reported; both subtypes exhibit comparable incidence and severity as a class effect (32–35). | (15–17, 36–38) |
| Hematological Toxicity | Neutropenia, thrombocytopenia, anemia | 20–80% (Dose-dependent) [Severe neutropenia (ANC <0.75×109/L) is a key reason for dose reduction] | Generally comparable between subtypes. Some evidence from HCV studies suggests a slightly higher incidence of grade 3/4 neutropenia with PegIFN-α-2b, potentially due to its wider volume of distribution and higher tissue exposure (34). | (14, 15, 18, 39–44) |
| Paradoxical Lymphocyte Consumption | Decreased absolute counts of circulating CD8+ T cells (total & virus-specific). | Commonly observed. | Insufficient comparative data; the phenomenon has been documented primarily with PegIFN-α-2a (13), but is presumed to be a class effect. | (13) |
| Neuropsychiatric Effects | Depression, irritability, insomnia, cognitive impairment, fatigue | 15–30% (Major depression: ~≤5%) | Comparable incidence between subtypes, as demonstrated in large HCV cohort studies (33, 34). | (15, 16, 19, 45–49) |
| Autoimmune Phenomena | Thyroid dysfunction (hypo-/hyperthyroidism), autoantibody production (e.g., anti-TPO). | ~8.8–15.8% during therapy. | Limited comparative data; both subtypes can induce thyroid dysfunction, and the incidence appears similar (32, 35). | (20–24, 50–53) |
| Gastrointestinal & Dermatological | GI: Nausea, diarrhea, anorexia. Derm: Alopecia, injection-site reactions, psoriasiform eruptions. | GI: 15–40%. Derm: Highly variable; alopecia is frequent (~48%). | Generally comparable. Injection-site reactions may be more frequent with PegIFN-α-2b in some reports, but data are inconsistent (35). | (15, 16, 25, 54–60) |
| Ocular Toxicity (Vascular) | Retinopathy (cotton-wool spots), retinal hemorrhage. | Symptomatic: Rare (<1–2%). Subclinical (on screening): 18% to >75%. | No comparative studies available. Both subtypes are associated with retinopathy, as documented in case series (29). | (27–31, 61, 62) |
| Hepatotoxicity (Immune-Mediated Flare) | ALT/AST elevation. | 10–30% | No evidence of differential risk; flares are considered a class effect reflecting therapeutic immune activation (63, 64). | (14, 16, 17, 55, 63, 65–67) |
| Pulmonary Toxicity | Dyspnea, cough, interstitial pneumonitis, pulmonary arterial hypertension (PAH). | Uncommon but serious. PAH incidence low (<1–2%). | Individual case reports exist for both subtypes; no comparative data available. | (68–73) |
| Cardiovascular Toxicity | Arrhythmias, myopericarditis, reversible cardiomyopathy, endothelial dysfunction. | Rare de novo in patients with normal baseline function. | Insufficient data to compare subtypes; both are associated with rare cardiovascular events (74). | (74–82) |
| Renal Toxicity | Proteinuria, hematuria, acute kidney injury. Includes collapsing FSGS and thrombotic microangiopathy (TMA). | Uncommon. | Both subtypes have been implicated in case reports of glomerulopathies and TMA (83, 84). | (83–91) |
| Musculoskeletal & Other Systemic | Myalgia, arthralgia, exacerbation or de novo autoimmune rheumatic disease. | Myalgia/arthralgia: Very common. Autoimmune: Rare. | No subtype-specific differences reported. | (22, 37, 92) |
| Effects in Special Populations | Reversible growth retardation (in pediatric patients). | Variable (population-dependent). | Most pediatric studies have utilized PegIFN-α-2b; data for PegIFN-α-2a in children are more limited (26, 93). | (26) |
| Baseline Immune Dysfunction (Therapeutic Target, Not an Adverse Reaction) | T-cell exhaustion: Persistence of virologic non-response. | Variable (in non-responders). | This is a pre-existing host condition, not a drug-specific effect; the goal of reversing exhaustion applies equally to both subtypes (7, 12, 94). | (7, 12, 94) |
The incidence of hematological toxicity is highly variable. Severe neutropenia (ANC <0.75 × 109/L) is a primary indication for dose reduction. It is crucial to distinguish between PegIFN-α-induced toxicities (e.g., cytopenias) which are adverse consequences of systemic immune activation, and the pre-existing state of T-cell exhaustion, which is the dysfunctional immune condition characteristic of chronic HBV infection that therapy aims to reverse. The “Lymphocyte Consumption” entry describes a therapy-induced depletion, while the “Baseline Immune Dysfunction” entry describes the pre-therapy state that may persist due to inadequate reversal.
ALT, alanine aminotransferase; ANC, absolute neutrophil count; anti-TPO, anti-thyroid peroxidase antibody; AST, aspartate aminotransferase; CD8, cluster of differentiation 8; FSGS, focal segmental glomerulosclerosis; HBV, hepatitis B virus; PAH, pulmonary arterial hypertension; PegIFN-α, pegylated interferon-alpha; TMA, thrombotic microangiopathy.