Abstract C008: Phase I biomarker analysis of farletuzumab ecteribulin (FZEC), formerly MORAb-202, effects on cancer responses in patients with platinum resistant ovarian cancer
Authors: Zhang Yan , Zimmermann Bob , Li Shuyu , Uenaka Toshimitsu , Furuuchi Keiji , Yonemori Kan , Shimizu Toshio , Nishio Shin , Yunokawa Mayu , Matsumoto Koji , Takehara Kazuhiro , Hasegawa Kosei , Hirashima Yasuyuki , Kato Hidenori , Otake Yohei , Miura Takuma , Matsui Junji , Li Meijuan 
Published: December 2023

Background: FZEC (formerly MORAb-202) is an antibody-drug conjugate consisting of farletuzumab and eribulin. FZEC is cytotoxic to FRα+ cancer cells (via direct binding) and to adjacent tumor cells (via bystander effects); it also exerts noncytotoxic bystander effects in the tumor microenvironment (Zhang et al, EORTC 2022). Study 101 is a first-in-human dose escalation followed by dose expansion study in Japanese patients (pts) with selected solid tumors to determine safety and preliminary efficacy of FZEC; antitumor activity across several doses was demonstrated in pts with platinum-resistant ovarian cancer (PROC) and FRα+ tumors (Nishio ASCO 2022). This exploratory biomarker study evaluated association of FZEC-induced pharmacological effects and clinical responses in pts with PROC to examine the mechanism of action (MoA) of FZEC.

Methods: Serum samples from up to 58 pts with PROC from a FZEC 0.9 mg/kg cohort (equivalent to 33 mg/m2) or from a combined dose cohort (FZEC 0.3, 0.45, 0.68, 0.9, 1.2 mg/kg) were collected predose on day 1 of treatment cycles 1–6 and analyzed using 139 exploratory Luminex, Simoa, or OLINK protein assays. While these doses are no longer being evaluated, as a result of a change to body-surface-area-based dosing, the biomarkers observed to be preliminarily associated with response in this analysis should be further explored in ongoing studies. Markers with &gt;30% unevaluable data points were excluded. The 1-sample Wilcoxon signed-rank test and 2-sample Wilcoxon rank-sum test were used to assess changes from baseline and differences between 2 best overall response groups (responders [CR/PR] and nonresponders [SD/PD]) at each visit. Fisher’s method was used to summarize statistical difference across visits (meta P&lt;0.05) between the 2 groups.

Results: Changes from baseline to at least 1 visit postdose (P&lt;0.05) in either the responder or nonresponder groups, and differences between responders and nonresponders (meta P&lt;0.05), were seen in 29 markers in the combined-dose cohort, and in 14 markers in the 0.9 mg/kg cohort. There was an overlap of 11 markers in both the FZEC 0.9 mg/kg and combined-dose cohorts that showed a significant change from baseline and significant differences in changes between responders and nonresponders. Among these 11 markers, SP-D and IGFBP-2 showed persistent changes (≥3 visits) in responders. Decreases in markers with reported protumor functions (eg, ANG-2, KLK-5, KLK-7, MCP-1, FRTN, and MMP-12), and increases in SP-D, were persistent (≥4 of 5 visits) in responders. Some biomarkers (eg, IGFBP-1, FLT3LG, and VEGF-D) showed significant increases in nonresponders.

Conclusions: The persistent responder-associated biomarker changes suggest that FZEC may modulate functions associated with these markers (eg, immune regulation, vascular remodeling, extracellular matrix protease activities, iron metabolism) and this may contribute to the antitumor effect of FZEC. In the limited number of pts analyzed, preliminary pharmacodynamic effects trended with the antitumor effects observed with FZEC 0.9 mg/kg.

Citation Format: Yan Zhang, Bob Zimmermann, Shuyu Li, Toshimitsu Uenaka, Keiji Furuuchi, Kan Yonemori, Toshio Shimizu, Shin Nishio, Mayu Yunokawa, Koji Matsumoto, Kazuhiro Takehara, Kosei Hasegawa, Yasuyuki Hirashima, Hidenori Kato, Yohei Otake, Takuma Miura, Junji Matsui, Meijuan Li. Phase I biomarker analysis of farletuzumab ecteribulin (FZEC), formerly MORAb-202, effects on cancer responses in patients with platinum resistant ovarian cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C008.