Garcia Del Muro, Xavier

PURPOSE Antitumor activity in preclinical models and a phase I study of patients with dedifferentiated liposarcoma (DD-LPS) was observed with selinexor. We evaluated the clinical benefit of selinexor in patients with previously treated DD-LPS whose sarcoma progressed on approved agents. METHODS SEAL was a phase II-III, multicenter, randomized, double-blind, placebo-controlled study. Patients age 12 years or older with advanced DD-LPS who had received two-five lines of therapy were randomly assigned (2:1) to selinexor (60 mg) or placebo twice weekly in 6-week cycles (crossover permitted). The primary end point was progression-free survival (PFS). Patients who received at least one dose of study treatment were included for safety analysis (ClinicalTrials.gov identifier: NCT02606461 ). RESULTS Two hundred eighty-five patients were enrolled (selinexor, n = 188; placebo, n = 97). PFS was significantly longer with selinexor versus placebo: hazard ratio (HR) 0.70 (95% CI, 0.52 to 0.95; one-sided P = .011; medians 2.8 v 2.1 months), as was time to next treatment: HR 0.50 (95% CI, 0.37 to 0.66; one-sided P < .0001; medians 5.8 v 3.2 months). With crossover, no difference was observed in overall survival. The most common treatment-emergent adverse events of any grade versus grade 3 or 4 with selinexor were nausea (151 [80.7%] v 11 [5.9]), decreased appetite (113 [60.4%] v 14 [7.5%]), and fatigue (96 [51.3%] v 12 [6.4%]). Four (2.1%) and three (3.1%) patients died in the selinexor and placebo arms, respectively. Exploratory RNA sequencing analysis identified that the absence of CALB1 expression was associated with longer PFS with selinexor compared with placebo (median 6.9 v 2.2 months; HR, 0.19; P = .001). CONCLUSION Patients with advanced, refractory DD-LPS showed improved PFS and time to next treatment with selinexor compared with placebo. Supportive care and dose reductions mitigated side effects of selinexor. Prospective validation of CALB1 expression as a predictive biomarker for selinexor in DD-LPS is warranted.

522 Background: In the METEOR study (NCT01865747), cabo demonstrated improved progression-free survival (median 7.4 vs. 3.8 mo; HR 0.58, 95% CI 0.45–0.74; p<0.0001), OS (median 21.4 vs. 16.5 mo; HR 0.66, 95% CI 0.53-0.83, p=0.0003), and objective response rate (17% vs. 3%; p<0.0001) compared with eve in patients (pts) with advanced RCC who had received prior VEGFR TKI therapy (Choueiri NEJM 2015, Lancet Oncol 2016). Here we evaluate the impact of changes in target lesion size from baseline on OS. Methods: 658 pts were randomized 1:1 to receive cabo (60 mg qd) or eve (10 mg qd). Stratification factors were MSKCC risk group and number of prior VEGFR TKIs. Target lesion size was assessed per independent radiology review by CT/MRI scans at baseline, every 8 weeks for the first 12 months, and every 12 weeks thereafter. Three subgroups were defined by best change in target lesion size from baseline: decrease ≥30%, decrease <30%, and any increase. Results: The rate of target lesion regression was higher in the cabo arm (75%) compared with the eve arm (48%). A higher fraction of pts had a decrease ≥30% in target lesion size in the cabo arm, while a higher fraction of pts had an increase in target lesion size in the eve arm (Table). Medians for OS with cabo were not estimable (NE) (95% CI, NE‒NE), 20.8 mo (95% CI, 18.1‒NE), and 11.1 mo (95% CI, 7.6‒15.2) for the ≥30% decrease, <30% decrease, and any increase subgroups, respectively. Medians for OS with eve were NE (95% CI, 19.3‒NE), 18.0 mo (95% CI, 15.9‒20.4), and 14.0 mo (95% CI, 10.5‒16.3) for the ≥30% decrease, <30% decrease, and any increase subgroups, respectively. Median duration of follow-up for OS was 18.7 mo (IQR 16.1–21.1) for cabo and 18.8 mo (16.0–21.2) for eve. A higher proportion of pts received subsequent anticancer therapy in the any increase subgroup compared with the other subgroups. Conclusions: Cabo demonstrated a higher rate of tumor target lesion regression than eve, and greater target lesion regression was associated with improved OS in pts with advanced RCC. Clinical trial information: NCT01865747. [Table: see text]