Despite rapid advances in clinical oncology, acquired drug resistance still poses a significant threat to the long-term efficacy of current treatment regimens. Because most chemotherapy drugs aim to activate apoptosis in cancer cells, expansion of the pharmacopeia to include treatments targeting novel tumor cell death mechanisms is a promising anti-cancer strategy. Induction of ferroptosis, an iron-dependent form of regulated cell death, shows particular therapeutic potential as aggressive metastatic and drug-resistant cancer cell states have been demonstrated to possess an exquisite dependency on glutathione peroxidase 4 (GPX4), a key suppressor of the ferroptotic cell death pathway. However, current GPX4 inhibitors are limited by poor pharmacokinetic properties that preclude their clinical use. The development of novel drug-like GPX4 inhibitors would benefit from the discovery of new chemical scaffolds to both enhance our understanding of the structural basis of small molecule binding and inhibition as well as facilitate the rational design of future GPX4-targeted therapeutics. In this dissertation, we employed three high-throughput screening strategies to identify novel scaffolds of interest for GPX4 inhibitor development.
First, a Lead-Optimized Compound (LOC) library was screened and we conducted further characterization and structure-activity relationship (SAR) studies on hit compound LOC880. Compared to the original hit, analogs QW-095 and QW-105 showed improved binding affinity and GPX4 inhibitory activity in vitro and also induced lipid peroxidation in cells suggestive of ferroptotic death. Further enhancement of the potency and ferroptosis specificity of this scaffold is still needed, but the potentially noncovalent and allosteric mechanism of action presents a novel approach for targeting GPX4.
Second, we conducted extensive SAR analyses on another promising hit from the LOC library screen, LOC1886, which led to the identification of the lead compound QW-314. This analog showed significantly improved potency and ferroptosis specificity in multiple cancer cell contexts, including a drug-tolerant persister cell model of minimal residual disease. Characteristic markers of GPX4 inhibition and ferroptosis are also observed in cells treated with QW-314, including GPX4 protein degradation and induction of lipid peroxidation, and QW-314 exhibited excellent selectivity for GPX4 over another glutathione peroxidase family selenoprotein GPX1 in an in vitro assay using cell lysates. Moreover, we determined a baseline of pharmacokinetic measures including aqueous solubility and metabolic stability in human and mouse liver microsomes for further medicinal chemistry optimization. Lastly, we screened a DNA-encoded library (DEL) and an Enamine Diversity library, identifying 10 additional chemical starting points for future investigation.
| Identifer | oai:union.ndltd.org:columbia.edu/oai:academiccommons.columbia.edu:10.7916/wsrq-xv50 |
| Date | January 2023 |
| Creators | Lin, Annie |
| Source Sets | Columbia University |
| Language | English |
| Detected Language | English |
| Type | Theses |
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