Outcome of Patients with Complex Karyotype in a Phase 3 Randomized Study of Idelalisib Plus Rituximab for Relapsed Chronic Lymphocytic Leukemia

Introduction: Complex karyotype (CKT), defined as the presence of ≥3 chromosomal aberrations, is emerging as an adverse prognostic factor in chronic lymphocytic leukemia (CLL) (Thompson et. al., Cancer 2015; Herling et. al., Blood, 2016). Idelalisib (IDELA) is a selective PI3Kd inhibitor approved for use in patients (pts) with relapsed CLL. A phase 3 randomized study of rituximab (R) plus IDELA or placebo (PBO) in pts with relapsed CLL and comorbidities (NCT1539512) demonstrated superior progression-free survival (PFS) and overall survival (OS) in the IDELA arm (Furman et. al. NEJM 2014). This report examines the effect of CKT on long-term outcome in that study. Methods: Key eligibility criteria included CLL requiring therapy after progression within 24 months of last therapy, and being unfit to receive cytotoxic therapy. Pts were randomized to receive IDELA at 150 BID (n = 110) or PBO (n = 110) in combination with R at 375 mg/m2 (first dose) and then 500 mg/m 2 q2 weeks x 4, followed by q4 weeks x 3 (8 doses total). After progression, prior PBO+R pts could enroll into an extension study to receive IDELA at 150 mg BID. The primary endpoint of PFS was assessed by an IRC using standard criteria (Hallek et. al. Blood 2008; Blood 2012; Cheson et. al . J Clin Oncol 2012). After the first prespecified interim analysis, with median IDELA exposure time of 3.8 months, the study was stopped due to overwhelming difference in efficacy and pts on PBO arm were offered open-label IDELA on the extension study. Baseline peripheral blood samples for karyotype analysis, TP53 mutation (mut), and FISH for del(17p) were analyzed by central labs. Metaphase spreads were produced after IL-2/CpG-stimulated cell cultivation and karyotypes were analyzed per ISCN 2013 nomenclature. Results: Based on geography, two labs received a total of 283 screening blood samples and prepared metaphase spreads, with one lab completing the karyotypic analyses. The overall karyotypic success rate was 65%, but was 98% for samples initially processed in one of the labs. Karyotypes were successfully performed in 127 of 220 randomized pts. The median follow-up for karyotyped IDELA and PBO pts was 21.4 months (range 0.3-39.4) and 12.0 months (range 0.2-35.8), respectively. CKT and non-CKT were found in 26 and 39 IDELA pts and 24 and 38 PBO pts, respectively. Overall, 16 IDELA pts and 15 PBO pts had del(17p)/ TP53 mut along with CKT. Within the IDELA group: the overall response rate (ORR) was 80.8% (95% CI 60.6-93.4) with CKT and 89.7% (95% CI 75.8-97.1) with non-CKT; the median PFS was 20.9 months in CKT vs 19.4 in non-CKT, HR = 1.18 (p = 0.63); the med OS was NR vs NR in CKT vs non-CKT, HR = 1.78 (95%CI 0.69-4.64; p = 0.23). The presence or absence of del(17p)/ TP53 mut and CKT status did not significantly affect PFS or OS in pts randomized to IDELA (Figure 1). Prior to crossover, the median PFS for IDELA vs PBO pts with CKT was NR vs 3.7 months, HR = 0.16 (p Conclusion: In this first systematic evaluation of CKT in relapsed CLL, CKT was found in 44% of 185 successfully karyotyped screened patients, including 37% of those randomized on study. This post hoc exploratory analysis demonstrates the lack of any adverse prognostic effect of CKT on IDELA-treated patients with respect to PFS or OS, and there was no significant difference among subsets of these pts with and without del(17p)/TP53mut. As previously reported in the entire study intention-to-treat population, a survival and PFS advantage was imparted by the addition of IDELA to R in pts with CKT. Detailed analyses including other clinical and prognostic parameters will be presented. Disclosures Kreuzer: Gilead Sciences: Consultancy, Honoraria, Research Funding, Speakers Bureau; Roche Pharma GmbH and Mundipharma GmbH: Consultancy, Honoraria, Research Funding, Speakers Bureau. Furman: Abbvie: Consultancy, Honoraria; Gilead Sciences: Consultancy; Janssen: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; Genentech: Consultancy. Stilgenbauer: Boehringer Ingelheim: Consultancy, Honoraria, Other: Travel grants , Research Funding; Amgen: Consultancy, Honoraria, Other: Travel grants, Research Funding; Genzyme: Consultancy, Honoraria, Other: Travel grants , Research Funding; Gilead: Consultancy, Honoraria, Other: Travel grants , Research Funding; Janssen: Consultancy, Honoraria, Other: Travel grants , Research Funding; AbbVie: Consultancy, Honoraria, Other: Travel grants, Research Funding; Genentech: Consultancy, Honoraria, Other: Travel grants , Research Funding; GSK: Consultancy, Honoraria, Other: Travel grants , Research Funding; Celgene: Consultancy, Honoraria, Other: Travel grants , Research Funding; Mundipharma: Consultancy, Honoraria, Other: Travel grants , Research Funding; Novartis: Consultancy, Honoraria, Other: Travel grants , Research Funding; Pharmacyclics: Consultancy, Honoraria, Other: Travel grants , Research Funding; Hoffmann-La Roche: Consultancy, Honoraria, Other: Travel grants , Research Funding; Sanofi: Consultancy, Honoraria, Other: Travel grants , Research Funding. Dubowy: Gilead Sciences: Employment, Equity Ownership. Kim: Gilead Sciences: Employment, Equity Ownership. Munugalavadla: Gilead Sciences: Employment, Equity Ownership. Pettitt: Celgene: Speakers Bureau; Infinity: Research Funding; Gilead: Research Funding, Speakers Bureau; Roche: Research Funding, Speakers Bureau. Hallek: Gilead Sciences: Research Funding, Speakers Bureau.