Off-therapy precipitous HBsAg decline predicts HBsAg loss after finite entecavir therapy in HBeAg-negative patients

Cessation of nucleos(t)ide analogue (Nuc) therapy in HBeAg-negative patients may increase HBsAg loss rate in patients with sustained remission (SR) and non-retreated clinical relapsers (CR). To investigate and compare the HBsAg kinetics from end of treatment (EOT) to HBsAg loss in these patients, serial serum samples after EOT from 36 SR and 12 CR with HBsAg loss (study group) and an 1:1 matched control who remained HBsAg-seropositive (control group) were assayed retrospectively for quantitative HBsAg (qHBsAg). The results showed that study group SR and CR had comparable EOT features except SR had lower EOT qHBsAg (67.5 vs 350.5 IU/mL; P = 0.02; < 100 IU/mL: 58.3% vs 25%; P = 0.09). All showed gradual qHBsAg decrease then “precipitous HBsAg decline” (>0.5 log₁₀ IU/mL in 1 year) prior to HBsAg loss. Patients with EOT qHBsAg <100 showed earlier (<12 months) “precipitous HBsAg decline” (91.7% vs 58.3%; P = 0.017) and sooner HBsAg loss (5.5 vs 21.9 months; P = 0.026). The control group also showed gradual qHBsAg decrease but less frequent “precipitous HBsAg decline” (39.6% vs 100%; P < 0.001) which occurred later (15.1 vs 5.7 months; P = 0.003) and was less steep (slope −0.6 vs −1.65 log₁₀ IU/mL/year; P < 0.001). HBsAg loss was achieved in 92.9% of the patients with “precipitous HBsAg decline” >0.76 log₁₀IU/mL in 1 year. In conclusion, both the SR and CR groups showed gradual HBsAg decrease followed by a “precipitous HBsAg decline”, which is a prerequisite for HBsAg loss. Lower EOT HBsAg in the SR group and qHBsAg <100 IU/mL may reflect better immune control hence followed by sooner HBsAg loss.