Developing novel LOX inhibitors to target chemotherapy resistant TNBC

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PROJECT SUMMARY Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype. It accounts for ~15% of all breast cancer yet is responsible for 30% of breast cancer deaths. TNBC is treated primarily by conventional chemotherapy; however, resistance to therapy is common, leading to high mortality rates. Importantly, the benefit of current therapeutic strategies used in chemoresistant TNBC; i.e., immunotherapy and antibody- drug conjugates, is confined to only a fraction of patients, and survival benefit is limited. Therefore, there is an urgent need to identify novel and effective treatment strategies to overcome resistance to chemotherapy. Recently, we identified hypoxia-induced ECM re-modeler, lysyl oxidase (LOX) as a key mediator of chemoresistance in TNBC (Saatci et al, Nature Communications, 2020). We showed that LOX is overexpressed in chemoresistant tumors, and its inhibition re-sensitizes the most aggressive breast tumors to doxorubicin using several clinically-relevant mouse models. However, the available LOX inhibitors are either non-selective or has toxicity. Hence, our main objective in this project is to develop potent, specific and well-tolerated LOX inhibitors to overcome chemoresistance in TNBC that has a high translational potential. Through high-throughput compound library screening and hit-to-lead conversion studies, we identified compounds with potent on-target cellular engagement of LOX, with good oral pharmacokinetics (PK) and with chemosensitizer effect without major toxicity (US PTO 17/693,371 and PCT/US2022/20086, patent pending). Starting from our current non-optimized lead molecule, we aim to develop lead compounds with increased potency, safety and drug-likeness. To accomplish this goal, in Phase I of this Fast-Track STTR grant, we will generate a diverse library of small molecules via an extensive structure activity relationship (SAR) study using our initial pharmacophore. We will test the synthesized inhibitors with respect to the degree of LOX enzymatic activity inhibition, LOX binding and selectivity towards LOX. We will perform the off-target assessment of the inhibitors using CEREP screen as well as kinome profiling. The shortlisted candidates will further be tested in ECM crosslinking and 3D chemosensitization assays using both cell lines and organoids. Inhibitors with better efficacy, selectivity and stability will move to Phase II. In Phase II, we will perform several ADME assays, including metabolic stability/identity, Caco-2 permeability and transport, cardiotoxicity and genotoxicity, plasma protein binding, CYP inhibition/induction/reaction phenotyping to improve drug-like properties while maintaining on-target potency in TNBC cells. Detailed PK/PD and toxicity analyses of the most promising candidates will be carried out followed by testing their chemosensitizer effect using both state-of-the-art immunodeficient (cell line- and patient-derived xenografts) and immunocompetent (syngeneic) mice models. The successful completion of the proposed project will lead to potent and specific, lead-optimized LOX inhibitors to overcome chemoresistance in TNBC, the deadliest form of breast cancer.