Effects of on‐treatment ALT flares on serum HBsAg and HBV RNA in patients with chronic HBV infection

As pegylated interferon alpha (PEG-IFN-α) is increasingly used in combination regimens of novel drugs, we aimed to characterize ALT flares and their relationship with serum HBsAg and HBV RNA kinetics in a large combined cohort of chronic hepatitis B (CHB) patients on PEG-IFN-α-based therapy. In this post hoc analysis of four international randomized trials, 269/130/124/128 patients on PEG-IFN-α monotherapy, PEG-IFN-α plus nucleos(t)ide analogue (NA) de novo combination, PEG-IFN-α add-on to NA or NA monotherapy were included, respectively. A flare was defined as an episode of ALT ≥5 × ULN. The association between flares and HBsAg and HBV RNA changes were examined. On-treatment flares occurred in 83/651 (13%) patients (median timing/magnitude: week 8 [IQR 4-12], 7.6 × ULN [IQR 6.2-10.5]). Flare patients were more often Caucasians with genotype A/D and had higher baseline ALT, HBV DNA, HBV RNA and HBsAg levels than the no-flare group. More flares were observed on PEG-IFN-α monotherapy (18%) and PEG-IFN+NA de novo combination (24%) vs. PEG-IFN-α add-on (2%) or NA monotherapy (1%) (p < .001). On-treatment flares were significantly and independently associated with HBsAg and HBV RNA decline ≥1 log₁₀ at the final visit declines started shortly before the flare, progressing towards 24 weeks thereafter. On-treatment flares were seen in 16/22 (73%) patients who achieved HBsAg loss. In conclusion, ALT flares during PEG-IFN-α treatment are associated with subsequent HBsAg and HBV RNA decline and predict subsequent HBsAg loss. Flares rarely occurred during PEG-IFN-α add-on therapy and associated with low HBsAg loss rates. Combination regimens targeting the window of heightened response could be promising.