Bingchen Yu

Esterase-Sensitive Prodrugs with Tunable Release Rates and Direct Generation of Hydrogen Sulfide†

Prodrugs that release hydrogen sulfide upon esterase-mediated cleavage of an ester group followed by lactonization are described herein. By modifying the ester group and thus its susceptibility to esterase, and structural features critical to the lactonization rate, H2 S release rates can be tuned. Such prodrugs directly release hydrogen sulfide without the involvement of perthiol species, which are commonly encountered with existing H2 S donors. Additionally, such prodrugs can easily be conjugated to another non-steroidal anti-inflammatory agent, leading to easy synthesis of hybrid prodrugs. As a biological validation of the H2 S prodrugs, the anti-inflammatory effects of one such prodrug were examined by studying its ability to inhibit LPS-induced TNF-α production in RAW 264.7 cells. This type of H2 S prodrugs shows great potential as both research tools and therapeutic agents.

Toward Carbon Monoxide–Based Therapeutics: Critical Drug Delivery and Developability Issues

Carbon monoxide (CO) is an intrinsic signaling molecule with importance on par with that of nitric oxide. During the past decade, pharmacologic studies have amply demonstrated the therapeutic potential of carbon monoxide. However, such studies were mostly based on CO inhalation and metal-based CO-releasing molecules. The field is now at the stage that a major effort is needed to develop pharmaceutically acceptable forms of CO for delivery via various routes such as oral, injection, infusion, or topical applications. This review examines the state of the art, discusses the existing hurdles to overcome, and proposes developmental strategies necessary to address remaining drug delivery issues.

Toward Hydrogen Sulfide Based Therapeutics: Critical Drug Delivery and Developability Issues

Hydrogen sulfide (H2S), together with nitric oxide (NO) and carbon monoxide (CO), belongs to the gasotransmitter family and plays important roles in mammals as a signaling molecule. Many studies have also shown the various therapeutic effects of H2S, which include protection against myocardial ischemia injury, cytoprotection against oxidative stress, mediation of neurotransmission, inhibition of insulin signaling, regulation of inflammation, inhibition of the hypoxia‐inducible pathway, and dilation of blood vessels. One major challenge in the development of H2S‐based therapeutics is its delivery. In this manuscript, we assess the various drug delivery strategies in the context of being used research tools and eventual developability as therapeutic agents.

Stereoselective Synthesis of 1-Methyl-3′,4′,5′,6′-tetrahydrospiro[indoline-3,2′-pyran]-2-one Derivatives via Prins Cyclization

A novel spirocyclization has been developed for the construction of functionalized spirooxindole pyran via Lewis acid promoted Prins cyclization. The reaction proceeds through formation of a single diastereoisomer with high stereoselectivity. This approach can be used to construct biologically important substituted spirooxindole as well as fluorinated pyran scaffolds.

Toward Direct Protein S-Persulfidation: A Prodrug Approach That Directly Delivers Hydrogen Persulfide

A general strategy of delivering hydrogen persulfide (H2S2) is described herein. Esterase- and phosphatase-sensitive H2S2 prodrugs with tunable release rates have been synthesized. Their utility is validated in examining protein S-persulfidation. With this unique approach of directly delivering H2S2, our findings reaffirmed that S-persulfidation leads to decreased activity of glyceraldehyde 3-phosphate dehydrogenase. This new approach complements available prodrugs/donors that directly deliver a single species, including hydrogen sulfide, perthiol, and COS, and will be very useful as part of the toolbox for delineating the mechanisms of sulfur signaling.

Esterase-Sensitive Glutathione Persulfide Donor

An esterase-sensitive glutathione persulfide (GSSH) donor (BW-GP-401) is described. The release profile was studied by monitoring the formation of lactone and direct trapping of GSSH with 1-fluoro-2,4-dinitrobenzene (DNFB). The donor was examined for its inhibitory effect toward glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Under highly oxidative conditions, the donor also shows cytoprotective effects in H9c2 cardiomyocytes.

Click, Release, and Fluoresce: A Chemical Strategy for a Cascade Prodrug System for Codelivery of Carbon Monoxide, a Drug Payload, and a Fluorescent Reporter

A chemical strategy was developed wherein a single trigger sets in motion a three-reaction cascade leading to the release of more than one drug-component in sequence with the generation of a fluorescent side product for easy monitoring. As a proof of concept, codelivery of CO with the antibiotic metronidazole was demonstrated.

Biomarker-Based Metabolic Labeling for Redirected and Enhanced Immune Response

Installation of an antibody-recruiting moiety on the surface of disease-relevant cells can lead to the selective destruction of targets by the immune system. Such an approach can be an alternative strategy to traditional chemotherapeutics in cancer therapy and possibly other diseases. Herein we describe the development of a new strategy to selectively label targets with an antibody-recruiting moiety through its covalent and stable installation, complementing existing methods of employing reversible binding. This is achieved through selective delivery of 1,3,4- O-acetyl- N-azidoacetylmannosamine (Ac3ManNAz) to folate receptor-overexpressing cells using an Ac3ManNAz-folate conjugate via a cleavable linker. As such, Ac3ManNAz is converted to cell surface glycan bearing an azido group, which serves as an anchor to introduce l-rhamnose (Rha), a hapten, via a click reaction with aza-dibenzocyclooctyne (DBCO)-Rha. We tested this method in several cell lines including KB, HEK-293, and MCF7 and were able to demonstrate the following: 1) Rha can be selectively installed to the folate receptor overexpressing cell surface and 2) the Rha installed on the target surface can recruit anti-rhamnose (anti-Rha) antibodies, leading to the destruction of target cells via complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP).