PB1904 PROPHYLAXIS FOR OCCULT HBV INFECTION UNDER IBRUTINIB THERAPY: MANDATORY OR OPTIONAL?

Background: Ibrutinib is a Bruton's tyrosine kinase inhibitor which plays a critical role in the management of some B cell malignancies. Although there are some case reports and case studies indicating hepatitis B virus (HBV) reactivation under ibrutinib therapy in patients who were not given concomitant HBV prophylaxis, case studies showing contradictory results also exist (Blood. 2018.131(17):1987‐9 and Leukemia&lymphoma. 2017.58(12):2966‐8). Past or active HBV infection was an exclusion criteria for the clinical studies of ibrutinib. Aims: In this study, we wanted to present our single‐center experience on the outcomes of patients with occult HBV infection receiving ibrutinib from a country with a relatively high incidence of HBV infection. Methods: Twenty‐three patients with B cell malignancies receiving ibrutinib were evaluated retrospectively. Demographic features, previous treatments (including rituximab (RTX)) and follow‐up durations, HBV infection and reactivation status, prophylaxis information, serum transaminase and total bilirubin levels were noted. Past HBV infection defined as concurrent detectable HBV core IgG Ab (Anti‐HBc IgG) and undetectable HBV surface Ag (HbsAg). Active HBV infection defined as HbsAg and/or HBV core IgM Ab (Anti‐HBc IgM) positivity. Quantitative HBV‐DNA PCR results are also recorded, if available. Results: Of these 23 patients, twenty‐two were eligable, and patients’ characteristics are displayed in Table 1. Median durations of ibrutinib therapy and entire follow‐up were 9.5 and 96 months, respectively. All patients had received RTX prior to ibrutinib. 6 patients had past HBV infection, while 2 had active HBV infection. HBV prophylaxis was started with treatments prior to ibrutinib in 5 patients, whereas 3 patients with past HBV infection were not given prophylaxis. Among these 3 cases with Anti‐HBc IgG positivity, two were also positive for HBV surface Ab (Anti‐HBs). Currently, 2 of these 3 cases including the one who is Anti‐HBs negative are both receving the 12th cycles, and the remaining one is at the 4th cycle of ibrutinib therapy. Serum Anti‐HBs titers and liver function tests are being followed at 3‐month intervals. To date, no signs of HBV reactivation was detected among our ibrutinib‐treated patients. Summary/Conclusion: Although the number of patients is limited and follow‐up periods are relatively short, our results indicate that patients with occult HBV infection treated with ibrutinib for B cell malignancies, might only be closely followed for HBV reactivation, rather than routine prophylactic anti‐HBV treatment. Upfront prophylactic treatment might still be an option for patients who can not be followed regularly. Possibility of loss of Anti‐HBs due to prior RTX exposure always should be kept in mind.