Characterization and Discovery of a Selective Small-Molecule Modulator of Mitochondrial Complex I Targeting a Unique Binding Site

Merging cultures and disciplines to create a drug discovery ecosystem at Virginia commonwealth university: Medicinal chemistry, structural biology, molecular and behavioral pharmacology and computational chemistry

The Department of Medicinal Chemistry, together with the Institute for Structural Biology, Drug Discovery and Development, at Virginia Commonwealth University (VCU) has evolved, organically with quite a bit of bootstrapping, into a unique drug discovery ecosystem in response to the environment and culture of the university and the wider research enterprise. Each faculty member that joined the department and/or institute added a layer of expertise, technology and most importantly, innovation, that fertilized numerous collaborations within the University and with outside partners. Despite moderate institutional support with respect to a typical drug discovery enterprise, the VCU drug discovery ecosystem has built and maintained an impressive array of facilities and instrumentation for drug synthesis, drug characterization, biomolecular structural analysis and biophysical analysis, and pharmacological studies. Altogether, this ecosystem has had major impacts on numerous therapeutic areas, such as neurology, psychiatry, drugs of abuse, cancer, sickle cell disease, coagulopathy, inflammation, aging disorders and others. Novel tools and strategies for drug discovery, design and development have been developed at VCU in the last five decades; e.g., fundamental rational structure-activity relationship (SAR)-based drug design, structure-based drug design, orthosteric and allosteric drug design, design of multi-functional agents towards polypharmacy outcomes, principles on designing glycosaminoglycans as drugs, and computational tools and algorithms for quantitative SAR (QSAR) and understanding the roles of water and the hydrophobic effect.

Novel Positron Emission Tomography Radiotracers for Imaging Mitochondrial Complex I

Mitochondrial dysfunction has been indicated in neurodegenerative and other disorders. The mitochondrial complex I (MC-I) of the electron transport chain (ETC) on the inner membrane is the electron entry point of the ETC and is essential for the production of reactive oxygen species. Based on a recently identified β-keto-amide type MC-I modulator from our laboratory, an ¹⁸F-labeled positron emission tomography (PET) tracer, ¹⁸F-2, was prepared. PET/CT imaging studies demonstrated that ¹⁸F-2 exhibited rapid brain uptake without significant wash out during the 60 min scanning time. In addition, the binding of ¹⁸F-2 was higher in the regions of the brain stem, cerebellum, and midbrain. The uptake of ¹⁸F-2 can be significantly blocked by its parent compound. Collectively, the results strongly suggest successful development of MC-I PET tracers from this chemical scaffold that can be used in future mitochondrial dysfunction studies of the central nervous system.

Synthesis, biological evaluation and cellular localization study of fluorescent derivatives of Jiyuan Oridonin A

Jiyuan Oridonin A (JOA) is a naturally occurring ent-kaurane diterpenoid that exhibits significant potential in the field of anti-tumor drug development. However, its detailed anti-cancer mechanism of action has not been fully understood. In order to investigate its anticancer mode of action, two series of novel fluorescent derivatives of JOA conjugated with naphthalimide dyes were synthesized, and their antitumor activity against five selected cancer cell lines (MGC-803, SW1990, PC-3, TE-1 and HGC-27) was evaluated. Compared with JOA, the anti-tumor activity of the vast majority of compounds were improved. Among them, B12 exhibited promising anti-proliferative activity against HGC-27 cells with IC₅₀ value of 0.39 ± 0.09 μM. Fluorescence imaging studies demonstrated that probe B12 could enter HGC-27 cells in a dose-dependent and time-dependent manner and was mainly accumulated in mitochondria. Preliminary biological mechanism studies indicated that B12 was able to inhibit cell cloning and migration. Further studies suggested that B12-induced apoptosis was related to the mitochondrial pathway. Overall, our results provide new approaches to explore the molecular mechanism of the natural product JOA, which would contribute to its further development as an antitumor agent.

Structural understanding of 5-(4-hydroxy-phenyl)-N-(2-(5-methoxy-1H-indol-3-yl)-ethyl)-3-oxopentanamide as a neuroprotectant for Alzheimer's disease

In our continuing efforts to develop novel neuroprotectants for Alzheimer's disease (AD), a series of analogs based on a lead compound that was recently shown to target the mitochondrial complex I were designed, synthesized and biologically characterized to understand the structure features that are important for neuroprotective activities. The results from a cellular AD model highlighted the important roles of the 4-OH on the phenyl ring and the 5-OCH3 on the indole ring of the lead compound. The results also demonstrated that the β-keto moiety can be modified to retain or improve the neuroprotective activity. Docking studies of selected analogs to the FMN site of mitochondrial complex I also supported the observed neuroprotective activities. Collectively, the results provide further information to guide optimization and development of analogs based on this chemical scaffold as neuroprotectants with a novel mechanism of action for AD.

The right tools for the job: the central role for next generation chemical probes and chemistry-based target deconvolution methods in phenotypic drug discovery

The reconnection of the scientific community with phenotypic drug discovery has created exciting new possibilities to develop therapies for diseases with highly complex biology. It promises to revolutionise fields such as neurodegenerative disease and regenerative medicine, where the development of new drugs has consistently proved elusive. Arguably, the greatest challenge in readopting the phenotypic drug discovery approach exists in establishing a crucial chain of translatability between phenotype and benefit to patients in the clinic. This remains a key stumbling block for the field which needs to be overcome in order to fully realise the potential of phenotypic drug discovery. Excellent quality chemical probes and chemistry-based target deconvolution techniques will be a crucial part of this process. In this review, we discuss the current capabilities of chemical probes and chemistry-based target deconvolution methods and evaluate the next advances necessary in order to fully support phenotypic screening approaches in drug discovery.