A novel survivin dimerization inhibitor without a labile hydrazone linker induces spontaneous apoptosis and synergizes with docetaxel in prostate cancer cells

Survivin, a member of the inhibitor of apoptosis protein family, exists as a homodimer and is aberrantly upregulated in a wide spectrum of cancers. It was thought to be an ideal target due to its lack of expression in most adult normal tissues and importance in cancer cell survival. However, it has been challenging to target survivin due to its "undruggable" nature. We previously attempted to target its dimerization domain with a hypothesis that inhibiting survivin dimerization would promote its degradation in proteasome, which led to identification of a lead small-molecule inhibitor, LQZ-7F. LQZ-7F consists of a flat tetracyclic aromatic core with labile hydrazone linking a 1,2,5-oxadiazole moiety. In this study, we tested the hypothesis that LQZ-7F could be developed as a prodrug because the labile hydrazone linker could be hydrolyzed, releasing the tetracyclic aromatic core. To this end, we synthesized the tetracyclic aromatic core (LQZ-7F1) using reported procedure and tested LQZ-7F1 for its biological activities. Here we show that LQZ-7F1 has a significantly improved potency with submicromolar IC_50's and induces spontaneous apoptosis in prostate cancer cells. It also more effectively inhibits survivin dimerization and induces survivin degradation in a proteasome-dependent manner than LQZ-7F. We also show that the combination of LQZ-7F1 and docetaxel have strong synergism in inhibiting prostate cancer cell survival. Together, we conclude that the hydrazone linker with the oxadiazole tail is dispensable for survivin inhibition and the survivin dimerization inhibitor, LQZ-7F, may be developed as a prodrug for prostate cancer treatment and to overcome docetaxel resistance.

Classics in Chemical Neuroscience: U-47700

U-47700, 3,4-dichloro-N-((1R,2R)-2-(dimethylamino)cyclohexyl)-N-methyl benzamide, is a novel synthetic opioid (NSO), discovered by the Upjohn company in the late 1970s. With potent in vivo activity, ∼10-times greater than that of morphine, U-47700 has become a drug of widespread abuse due to its ease of synthesis and, until recently, lack of robust detection methods by law enforcement. U-47700 has been found in counterfeit oxycodone tablets and is a key ingredient in "gray death." Due to its emergence worldwide in the past 5 years, it is now a Schedule I drug in the United States and similarly designated around the world; moreover, at autopsy, U-47700 was found to have contributed to the death of the pop artist Prince. This Review will capture the >40 year history of U-47700 and go in-depth regarding the synthesis, medicinal chemistry, in vitro/in vivo pharmacology, drug metabolism (from postmortem overdose cases), and societal impact of this DARK Classic in chemical neuroscience.

Synthesis and Identification of a Novel Lead Targeting Survivin Dimerization for Proteasome-Dependent Degradation

Survivin, a homodimeric member of the Inhibitor of Apoptosis Protein (IAP) family, is required for cancer cell survival and overexpressed in almost all solid tumors. However, targeting survivin has been challenging due to its "undruggable" nature. Recently, we used a novel approach to target the dimerization interface and identified inhibitors of two scaffolds that can directly bind to and inhibit survivin dimerization. One of the scaffolds, represented by the compound LQZ-7, contains an undesirable labile hydrazone linker and a potentially nonfunctional furazanopyrazine ring that we attempted to eliminate in this study. We found one compound, 7I, that is more active than the parent compound, LQZ-7, and when given orally effectively inhibits xenograft tumor growth and induces survivin loss in tumors. These findings indicate that 7I with a stable linker and a quinoxaline ring can be used as a lead for further optimization of this novel class of survivin inhibitors.

An aryl isonitrile compound with an improved physicochemical profile that is effective in two mouse models of multidrug-resistant Staphylococcus aureus infection

OBJECTIVES

The aim of this study was to investigate the antibacterial activity of a synthetic aryl isonitrile compound (35) that was developed as part of a compound library to identify new antibacterial agents effective against methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

Compound 35 was evaluated against MRSA isolates by the broth microdilution assay and for toxicity to mammalian keratinocytes using the MTS assay. A multistep resistance selection assay was conducted to investigate MRSA resistance development to 35. A Caco-2 bidirectional permeability assay was employed to evaluate the ability of 35 to permeate across the gastrointestinal tract, and compound 35 was incubated with human liver microsomes to determine susceptibility to hepatic metabolism. Finally, compound 35 was evaluated in an uncomplicated MRSA skin infection mouse model and an MRSA neutropenic thigh infection mouse model.

RESULTS

Compound 35 inhibited the growth of MRSA clinical isolates at 2-4μM and was non-toxic to human keratinocytes. No resistance formation was observed with MRSA against compound 35 after 10 serial passages. In a murine skin wound model, compound 35 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. Compound 35 exhibited a marked improvement both in permeability and stability to hepatic metabolism (half-life >11h) relative to the first-generation lead compound. In a neutropenic thigh infection mouse model, compound 35 successfully reduced the burden of MRSA in immunocompromised mice.

CONCLUSION

In summary, compound 35 was identified as a new lead aryl isonitrile compound that warrants further investigation as a novel antibacterial agent.

Second-generation aryl isonitrile compounds targeting multidrug-resistant Staphylococcus aureus

Antibiotic resistance remains a major global public health threat that requires sustained discovery of novel antibacterial agents with unexploited scaffolds. Structure-activity relationship of the first-generation aryl isonitrile compounds we synthesized led to an initial lead molecule that informed the synthesis of a second-generation of aryl isonitriles. From this new series of 20 compounds, three analogues inhibited growth of methicillin-resistant Staphylococcus aureus (MRSA) (from 1 to 4 µM) and were safe to human keratinocytes. Compound 19, with an additional isonitrile group exhibited improved activity against MRSA compared to the first-generation lead compound. This compound emerged as a candidate worthy of further investigation and further reinforced the importance of the isonitrile functionality in the compounds' anti-MRSA activity. In a murine skin wound model, 19 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. In summary, 19 was identified as a new lead aryl isonitrile compound effective against MRSA.

Discovery and characterization of aryl isonitriles as a new class of compounds versus methicillin- and vancomycin-resistant Staphylococcus aureus

Methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA) have emerged as a global health concern. A new class of compounds featuring an aryl isonitrile moiety has been discovered that exhibits potent inhibitory activity against several clinically-relevant MRSA and VRSA isolates. Structure-activity relationship studies have been conducted to identify the aryl isonitrile group as the key functional group responsible for the observed antibacterial activity. The most potent antibacterial aryl isonitrile analogs (MIC 2 μM) did not show any toxicity against mammalian cells up to a concentration of 64 μM.