Correlation of cyclin E1 expression and clinical outcomes in a phase 1b dose-escalation study of azenosertib (ZN-c3), a WEE1 inhibitor, in combination with chemotherapy (CT) in patients (pts) with platinum-resistant or refractory (R/R) epithelial ovarian, peritoneal, or fallopian tube cancer (EOC).

Abstract

5513 Background: Azenosertib (ZN-c3) is a novel, selective, and orally bioavailable WEE1 inhibitor demonstrating single-agent antitumor activity. Azenosertib may inhibit CT-induced DNA damage repair and provide benefit in pts with platinum R/R EOC. Cyclin E1 amplification/overexpression is present in ≥35% of metastatic ovarian cancer. High expression/amplification of Cyclin E1 is a poor prognostic marker and predictive of lack of response to platinum-based CT. Ovarian models overexpressing Cyclin E1 have exquisite sensitivity to azenosertib in vitro and in vivo; forced Cyclin E1 overexpression sensitizes cell lines with low endogenous Cyclin E1 to azenosertib. Methods: This open-label, multicenter study (NCT04516447) assessed azenosertib + paclitaxel (PAC), carboplatin (Carbo), gemcitabine (GEM), or pegylated liposomal doxorubicin (PLD) in pts with metastatic high-grade serous EOC after ≤2 lines of CT including platinum CT. Primary endpoint is safety and identification of RP2D of each combination. Secondary endpoints include clinical activity. Azenosertib was given continuously or intermittently QD in 21 or 28D cycles until PD or unacceptable toxicity. Results: 103 pts were enrolled; at data cut-off, 94 were efficacy evaluable. 26.6% had a partial response (PR) and median progression free survival (PFS) = 9.03 mo (95%CI: 5.52-11.01). Azenosertib + PAC demonstrated the highest ORR [9/18 (50%)], followed by Carbo [9/27 (33.3%)]; ORR for azenosertib + PLD or + GEM was 14.3% (5/35, 2/14 respectively). 80 pts had available Cyclin E1 expression data by IHC; higher Cyclin E1 (H-score >50) correlated with higher ORR and longer PFS (ORR = 31.3% vs 7.7%; PFS = 10.35 vs 3.25 mo, HR=0.3; Table). Frequent Grade ≥3 TEAEs (%) were neutropenia (44.4), thrombocytopenia (30.3), anemia (12.1), leukopenia (11.1), fatigue (10.1), diarrhea (6.1), nausea (5.1), and vomiting (5.1). Conclusions: Azenosertib + CT is well tolerated and has encouraging clinical activity, with durable responses in pts with platinum R/R EOC. Pts with Cyclin E1 overexpressing tumors, a subgroup with suboptimal benefits from CT, demonstrated significant improvements in ORR and PFS vs pts with tumors having low expression. These data support a planned trial of azenosertib + CT vs CT alone in Cyclin E1 overexpressing platinum R/R EOC. Clinical trial information: NCT04516447 . [Table: see text]