Objective : Post-marketing surveillance was conducted for the purpose of demonstrating the relationship between the therapeutic effect of natural IFN-β preparation on chronic active hepatitis C and HCV subtype or viral load as well as various predictors of its efficacy.
Design : Cohort studies.
Methods : Questionnaires were sent to all medical institutions at which IFN-β ('IFNβMochida') was administered to patients with chronic active hepatitis C once daily for at least 8 weeks and its therapeutic effect was judged based on the rate of virological sustained response (VSR) and the rate of biochemical (ALT) sustained response (BSR).
Results : Questionnaires for 2, 076 patients were collected from 244 medical institutions all over the country. Of these questionnaires, those for 1, 503 patients, 930 men (61.9%) and 573 women (38.1%), collected from 229 institutions could be evaluated regarding the therapeutic effect of IFNβ Mochida. The patients' mean age was 50.2 years. The average VSR were 31% for all of the patients (1, 503 patients), 61% for those with a low viral load (HCV-RNA level before IFN treatment ; <106 copies/ml) and 14% for those with a high viral load (≥106 copies/ml) ; with the subtypes 1 b, 2 a and 2 b accounting for 18, 55 and 29% respectively. BSR were 45, 69 and 32%, respectively ; with the subtypes 1 b, 2 a and 2 b accounting for 32, 66 and 56%. As for the therapeutic effect in patients with the same level of viral load but different viral subtype, at each level of viral load VSR was the highest in subtype 2 a, followed by 2 b and 1 b, showing a significant difference between 2 a and 1 b or 2 b, depending on the level of viral load. BSR of 2 a and 2 b were similarly high, showing a significant difference between 2 a or 2 b and 1 b, depending on the level of viral load. In patients with subtype 1 a or 1 b, patients who were administered IFN-β≥339 MU obtained a higher VSR than those who were administered IFN-β ≤336MU. Adverse drug reactions were observed in 89% of the total 2, 076 patients, however, these symptoms disappeared immediately after the completion of the treatment. Univariate and multivariate logistic regression analyses conducted to detect the predictors on the therapeutic effect (VSR) of IFN-β revealed that the subtype, viral load and age were significant factors for all the patients and that the viral load and NS5A mutation were significant factors for the patients with subtype 1 b. However, the NS5A mutant type viral load was significantly less than that of the other types, showing no difference in the therapeutic effect in the comparison at the same level of viral load.
Conclusion : It was confirmed that the therapeutic effect of the natural IFN-β preparation on chronic active hepatitis C varied widely depending on the viral load and viral subtype. This information will play an important role in the development of therapy for chronic hepatitis C in the future.