PS1163 PATIENT‐BASED PROSPECTIVE REAL WORLD DATA ANALYSIS SHOWS THAT THE DURATION OF TREATMENT INTERRUPTIONS WITH SUBSEQUENT RESUMPTION OF IDELALISIB THERAPY CAN VARY FROM DAYS TO MONTHS
Authors: Hoechstetter M. , Knauf W. , Eissmann P. , Hucke N. , Ramroth H. , Abenhardt W. , Rummel M. 
Published: June 2019

Background:Idelalisib, a first‐in‐class PI3Kδ‐inhibitor, is licensed in the European Union in relapsed chronic lymphocytic leukemia (CLL) and refractory follicular lymphoma (FL). Treatment should be continued until disease progression or unacceptable toxicity and may continue for several months or years. Optimal therapy management is therefore important and may include temporary treatment interruptions (TIs) and dose modifications to manage idelalisib associated adverse drug reactions (ADRs).Aims:Recent data from a retrospective analysis of idelalisib clinical studies suggest that patients may benefit from optimal ADR management of idelalisib via TI and subsequent resumption of therapy [Ma et al. ASH 2018]. Here we analyzed frequency and duration of TIs within a prospective observational study. To understand the effect of TIs on the course of disease, we additionally analyzed lymphocyte counts during and after treatment interruption on an individual patient level.Methods:Post‐hoc analysis of a prospective, two‐cohort, multicenter, non‐interventional post‐authorization safety study (PASS) reporting real world safety and effectiveness data on the use of idelalisib in Germany. Inclusion of patients was based on the physician's decision to initiate treatment with idelalisib in accordance with the European Summary of Product Characteristics. Detailed methods, patient characteristics and results were already published at two conferences [Hoechstetter et al. DGHO 2018; Hoechstetter et al. ASH 2018]. Descriptive statistics were used for data analysis. Idelalisib TIs were defined as documented interruptions with subsequent resumption of idelalisib therapy.Results:96 patients (84 CLL and 12 FL patients) enrolled at 45 sites were included until data cut in February 2018 with a median follow‐up of 9.7 months. 58 patients had documented permanent discontinuation of idelalisib therapy. 49 patients had one or more documented TIs with 26 patients (one TI n = 20, two TI n = 6) subsequently resuming therapy. After interruptions, treatment was resumed with the standard or a reduced idelalisib dose of 150 mg or 100 mg twice daily, respectively. The most frequently reported reason for both dose reduction and TI was ADR, only 9 TIs followed an adverse event (AE) not related to idelalisib. The 3 most commonly reported ADRs (events) resulting in TI were diarrhea (9), pulmonary complications (4) and rash (3). The duration of TIs varied widely from only a few to 235 days. The median (range) duration of a single TI was 15 (1–235) days, representing 15 (1–86) days for the first and 16 (5–235) days for the second interruption, respectively. 9 patients had a single interruption with a duration of >30 days. Patient level data demonstrate stable or only moderate changes in lymphocyte counts during this treatment interruption.Summary/Conclusion:Optimal management of idelalisib therapy to achieve best outcomes for patients may include temporary TIs and/or dose modifications. However, little information is available about the duration of idelalisib TIs and the possibility to resume therapy in routine clinical practice. Our analysis of prospectively collected real world data shows that the duration of TIs may vary widely from a few days to several months with about 50% of patients with a TI resuming idelalisib therapy. Patient level data suggest that lymphocyte counts were relatively stable during and after TIs. Our results therefore provide evidence that idelalisib treatment may be interrupted to allow treatment of ADRs/AEs with subsequent resumption of idelalisib therapy.image