Abstract LB-B04: Development of a first-in-class leukemia inhibitory factor (LIF)/LIFR inhibitor, EC359 for targeted therapy

Abstract

Abstract Background: An IL-6 family member, leukemia inhibitory factor (LIF), is a pleotropic cytokine involved in multiple cellular signaling and pathophysiology of various malignancies including cancer. Overexpression of LIF is significantly correlated with advanced tumor stage, larger tumor size and worse relapse free survival rate. The objective of present study to develop and characterize next generation steroidal LIF/LIFR inhibitor based on our first LIF inhibitor, EC330. In this study, we optimized EC330 by synthetic modifications and generated EC359 to reduce its binding to classical steroid receptors and to improve its oral bioavailability. Material and methods: In silico docking studies were used to identify putative interaction of EC359 and LIF/LIFR receptor complex. We confirmed binding of EC359 to LIFR using surface plasmon resonance (SPR). Biophysical and biological characterization was performed by measuring cytotoxicity in various cancer cell lines and anchorage-independent colony assays. Specificity to LIF/LIFR was measured by GST pull-down assay and by SPR using commercially available recombinant proteins of LIF and LIFR. In vivo efficacy and toxicity was tested using syngeneic mice tumors and xenograft models. Results: EC359 showed cytotoxicity in various cancer cells at low nano-molar range, blocked formation of colonies in soft agar and inhibited triple negative breast cancer (TNBC) stem cells. Physical direct-interaction was confirmed by SPR which showed EC359 binding to LIFR with an affinity of 81μM. EC359 showed cytoskeletal disruption and targeting cancer-associated fibroblasts (CAFs) through inhibition of alpha-SMA but not beta-tubulin. Blockade of LIF-LIFR interaction reduced the STAT3 phosphorylation, mTOR and further downstream signaling cascades. In vivo, EC359 treatment (1 and 5mg/kg) dose dependently reduced tumor burden in both TNBC xenograft and murine syngeneic MM51 models. Pharmacologically, EC359 exhibits a high oral bioavailability and long half-life in rats with a wide therapeutic window. Conclusions: Our findings establish EC359 as a novel LIF/LIFR targeting drug with therapeutic perspectives for patients with advanced primary tumors. LIF/LIFR targeting may result in the blockade of JAK- STAT signaling pathway as well as cancer fibroblast associated pro invasive tumor microenvironment in regular as well as therapy resistant tumors. Citation Format: Hareesh B. Nair, Bindu Santhamma, Suryavathi Viswanadhapalli, Gangadhara R. Sareddy, Xinlei Pan, Vijaya Manthati, Ratna K. Vadlamudi, Murali Ramachandran, Klaus J. Nickisch. Development of a first-in-class leukemia inhibitory factor (LIF)/LIFR inhibitor, EC359 for targeted therapy [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B04.