ANNOUNCE: A randomized, placebo (PBO)-controlled, double-blind, phase (Ph) III trial of doxorubicin (dox) + olaratumab versus dox + PBO in patients (pts) with advanced soft tissue sarcomas (STS)

LBA3 Background: Dox is standard therapy in STS. In a Ph 2 trial, olaratumab (a human IgG1 antibody targeting PDGFRα) + dox improved overall survival (OS) and progression-free survival (PFS) vs dox. ANNOUNCE aimed to confirm the OS benefit in advanced STS. Methods: Adult pts with unresectable locally advanced or metastatic STS, anthracycline-naïve, and ECOG PS 0-1 were eligible. Pts were randomized 1:1 to olaratumab (20mg/kg Cycle 1, 15mg/kg subsequent cycles) or PBO on Days 1 and 8 of each 21-day cycle combined with dox (75mg/m2) on Day 1 for up to 8 cycles. After 8 cycles, pts with disease control continued olaratumab or PBO until progression or toxicity. Randomization was stratified by histology, prior systemic therapy, ECOG PS, and geographic region. Dexrazoxane use was allowed to mitigate dox-related cardiotoxicity. Primary endpoints were OS in the intent-to-treat (ITT) population and/or leiomyosarcoma (LMS) subset of the ITT population; the study was designed to be positive if either primary endpoint was met. Secondary endpoints included PFS, response/disease control rates, safety, and pharmacokinetics. Results: 509 pts were randomized: 258 in the investigational and 251 in the control arm. Baseline pt characteristics were well balanced. Dexrazoxane was received by 63.0% vs 65.1% of pts (investigational vs control arm, respectively, for all data). In the ITT population, median OS was 20.4 vs 19.8 months (m) (HR=1.05, 95% CI: 0.84-1.30; p = 0.69) and was 21.6 vs 21.9 m in LMS pts (HR=0.95, 95% CI: 0.69-1.31; p = 0.76). Median PFS was lower in the investigational arm in the ITT population (5.4 vs 6.8 m; HR=1.23, 95% CI: 1.01-1.50; p = 0.04) and in LMS pts (4.3 vs 6.9 m, HR=1.22, 95% CI: 0.92-1.63; p = 0.17). Median dox exposure was 6 vs 7 cycles. Safety was similar between arms. Olaratumab serum concentrations reached levels expected from prior trials. Additional subgroup/biomarker results will be presented. Conclusions: ANNOUNCE did not confirm that olaratumab + dox, followed by olaratumab monotherapy, improves OS over dox in pts with advanced STS. Further analyses are warranted to explore the inconsistent outcomes between the Ph 3 and Ph 2 studies. Clinical trial information: NCT02451943.