1087. Evaluation of Risk Factors for Infection among Patients Receiving Ibrutinib

Background Ibrutinib is a small-molecule inhibitor of Bruton tyrosine kinase (BTK) approved for various B-cell malignancies and cGVHD. Rates of serious infection—defined as requiring hospitalization or parenteral antimicrobials— and invasive fungal infection (IFI) in patients on ibrutinib are as high as 11.4% and 4.2% respectively (Varughese T, et al. Clin Infect Dis 2018;67(5):687-92), which may be related to off-target inhibition of interleukin-2-inducible T-cell kinase or macrophage function. Methods We retrospectively reviewed infection complications in patients receiving ibrutinib at our institution between 06/01/2014 and 08/31/2019, including patients who received single-agent or combination ibrutinib. In this study, serious infection was defined as above, or a diagnosis of pneumonia regardless of hospitalization or parenteral antimicrobial therapy. Logistic regression was used to identify risk factors. Results Baseline characteristics of 134 included patients are in Table 1. Infection and serious infection occurred in 96 (72%) and 48 (36%) patients, respectively. When pneumonia was not included as a criterion for serious infection, the serious infection rate was 22%. Prior allogeneic stem cell transplant (allo-HSCT) (OR 4.50; 95% CI 1.19 – 17.00) and corticosteroid use (OR 5.42; 95% CI 1.49 – 19.82) were significant risk factors for serious infection without pneumonia (Table 2). Of 37 patients (28%) who received primary HSV/VZV prophylaxis with acyclovir, there was one case of suspected herpes zoster infection (3%). IFI developed in 7 patients (5%): 5 with Pneumocystis jirovecii pneumonia (PJP), 1 with invasive aspergillosis, and 1 with a filamentous fungus, species unknown. Other identified organisms are detailed in Figure 1. Classical risk factors for IFI, including diabetes, allo-HSCT, and concurrent corticosteroid use, were not significant predictors in this group. Table 1. Baseline Characteristics Table 2. Risk Factor Analysis Figure 1. Identified Organisms in Serious Infection Conclusion Serious infections developed at a higher rate than previously reported in the literature, with IFI rates similar to those previously described. Prior allo-HSCT and steroid use were found to be risk factors for serious infection without pneumonia. Treating physicians should have a high index of suspicion for pneumonia, IFI, and PJP in this population. Disclosures All Authors: No reported disclosures