Abstract CT173: Sunitinib (S) in patients (pts) with metastatic breast cancer (mBC) with FGFR1 mutations or amplifications: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study

Background: TAPUR is a phase II basket study evaluating anti-tumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. S is an oral multi-kinase inhibitor that inhibits Fibroblast Growth Factor Receptor family members 1-4 (FGFR1-4) in biochemical and cellular assays and is FDA approved in several tumor types. Results in a cohort of mBC pts with FGFR1 mutations (mut) or amplifications (amp) treated with S are reported. Methods: Eligible pts had mBC, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was performed in CLIA-certified, CAP-accredited site selected labs. Pts received S 50 mg orally daily for four weeks followed by two weeks off, until tumor progression. Simon 2-stage design tested the null disease control (DC) - defined as partial (PR), complete response (CR) or stable disease at 16+ weeks (SD 16+) - rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 have DC, 18 more pts are enrolled. If ≥7 of 28 pts have DC, the null DC rate is rejected. Secondary endpoints are progression-free survival (PFS), overall survival (OS) and safety. Results: Thirty pts with mBC with FGFR1 mut (1 pt), amp (28 pts), or both (1 pt) were enrolled from Oct 2016 to June 2019. 3 were not evaluable and excluded from efficacy analyses. Demographics and outcomes are summarized in Table 1. Two partial responses (PR) and 5 SD16+ (FGFR1 amp only) were observed for DC and OR rates of 29% (95% CI: 13%, 42%) and 7% (95% CI: 1%, 24%), respectively, and the null DC rate of 15% was rejected (p=0.09). S related grade 3-5 TAEs (Table 1) were consistent with the product label for S except encephalopathy. Conclusions: Monotherapy S showed modest anti-tumor activity and clinically significant TAEs in heavily pre-treated pts with mBC with FGFR1 amplification. Citation Format: Carmen Calfa, Michael Rothe, Pam K. Mangat, Elizabeth Garrett-Mayer, Eugene Ahn, Keerthi Gogineni, Nitin Rohatgi, Monika L. Burness, Anu Gaba, Omid Hamid, Tareq Albaghdadi, Alison Conlin, Philip Gold, Jordi Rodon, Ramya Thota, Richard L. Schilsky. Sunitinib (S) in patients (pts) with metastatic breast cancer (mBC) with FGFR1 mutations or amplifications: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT173.