Aim

• To retrospectively evaluate Hepatitis B Virus (HBV) status in children who had received adefovir dipivoxil (ADV) as part of a trial within the past 11 years.

• To determine whether ADV treatment pre-conditions patients to spontaneous HBeAg seroconversion and ALT/HBV DNA reduction in later years with no additional further treatment.

Methods 9 children with chronic HBV from a single centre that had received ADV as part of a 4 year, double blind multi centre trial in 2004–2005 were identified. Clinical data was collected (May–July 2015) from both paediatric and adult services from pre/post trial periods including:

• HBV serology and DNA

• Liver function tests

• Adverse events

• Other treatments received

Results 6 of the 9 cohort children completed the original trial; with one undergoing HBeAg seroconversion within the study period and rest deemed ‘failed responders’.

In subsequent years, the remaining 5 have all had HBeAg seroconversion at varying time points post-treatment (100% vs 16.7% in the original trial). Mean duration post-treatment to seroconversion was 2112.8 days. No other treatments were given after the trial to confound results. No correlation can be found with time to seroconversion and age/ethnicity/sex/ original ADV treatment length/HBV genotype.

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Abstract G48(P) Figure 1

Results of HBV DNA post ADV treatment

All 6 children had falling HBV DNA post ADV treatment (Figure 1). Baseline mean for all participants (at original study recruitment) was 3 × 10⁸ copies/ml (with 2 outliers at higher levels), compared to end mean of 1.711 × 10⁴ copies/ml. This was similar for ALT (baseline 39 – end 23 means). No adverse effects were noted in any of the cohort.

Conclusion There is a high rate of spontaneous seroconversion post ADV treatment in children and adolescents. This suggests that treatment may provide hepatic pre-conditioning for long-term HBeAg seroconversion, above that expected without additional treatment. HBV DNA and ALT are further reduced. No safety issues are noted. Patients from other centres will be examined to study the wider implications of this study and whether this is a paediatric specific effect. Further biological and clinical studies are warranted to understand the potential for hepatic conditioning for spontaneous HBV seroconversion in children.