Development of LB244, an Irreversible STING Antagonist.

The cGMP-AMP Synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway plays a critical role in sensing dsDNA localized to the cytosol, resulting in the activation of a robust inflammatory response. While cGAS-STING signaling is essential for antiviral immunity, aberrant STING activation is observed in amyotrophic lateral sclerosis (ALS), lupus, and autoinflammatory diseases such as Aicardi-Goutières syndrome (AGS) and STING associated vasculopathy with onset in infancy (SAVI). Significant efforts have therefore focused on the development of STING inhibitors. In a concurrent submission, we reported that BB-Cl-amidine inhibits STING-dependent signaling in the nanomolar range, both in vitro and in vivo. Considering this discovery, we sought to generate analogs with higher potency and proteome-wide selectivity. Herein, we report the development of LB244, which displays nanomolar potency and inhibits STING signaling with markedly enhanced proteome-wide selectivity. Moreover, LB244 mirrored the efficacy of BB-Cl-amidine in vivo. In summary, our data identify novel chemical entities that inhibit STING signaling and provide a scaffold for the development of therapeutics for treating STING-dependent inflammatory diseases.

Dual Inhibitors of Main Protease (MPro) and Cathepsin L as Potent Antivirals against SARS-CoV2.

Given the current impact of SARS-CoV2 and COVID-19 on human health and the global economy, the development of direct acting antivirals is of paramount importance. Main protease (MPro), a cysteine protease that cleaves the viral polyprotein, is essential for viral replication. Therefore, MPro is a novel therapeutic target. We identified two novel MPro inhibitors, D-FFRCMKyne and D-FFCitCMKyne, that covalently modify the active site cysteine (C145) and determined cocrystal structures. Medicinal chemistry efforts led to SM141 and SM142, which adopt a unique binding mode within the MPro active site. Notably, these inhibitors do not inhibit the other cysteine protease, papain-like protease (PLPro), involved in the life cycle of SARS-CoV2. SM141 and SM142 block SARS-CoV2 replication in hACE2 expressing A549 cells with IC50 values of 8.2 and 14.7 nM. Detailed studies indicate that these compounds also inhibit cathepsin L (CatL), which cleaves the viral S protein to promote viral entry into host cells. Detailed biochemical, proteomic, and knockdown studies indicate that the antiviral activity of SM141 and SM142 results from the dual inhibition of MPro and CatL. Notably, intranasal and intraperitoneal administration of SM141 and SM142 lead to reduced viral replication, viral loads in the lung, and enhanced survival in SARS-CoV2 infected K18-ACE2 transgenic mice. In total, these data indicate that SM141 and SM142 represent promising scaffolds on which to develop antiviral drugs against SARS-CoV2.

ß-Cyclodextrin-poly (ß-Amino Ester) Nanoparticles Are a Generalizable Strategy for High Loading and Sustained Release of HDAC Inhibitors.

Therapeutic development of histone deacetylase inhibitors (HDACi) has been hampered by a number of barriers to drug delivery, including poor solubility and inadequate tissue penetration. Nanoparticle encapsulation could be one approach to improve the delivery of HDACi to target tissues; however, effective and generalizable loading of HDACi within nanoparticle systems remains a long-term challenge. We hypothesized that the common terminally ionizable moiety on many HDACi molecules could be capitalized upon for loading in polymeric nanoparticles. Here, we describe the simple, efficient formulation of a novel library of ß-cyclodextrin-poly (ß-amino ester) networks (CDN) to achieve this goal. We observed that network architecture was a critical determinant of CDN encapsulation of candidate molecules, with a more hydrophobic core enabling effective self-assembly and a PEGylated surface enabling high loading (up to ∼30% w/w), effective self-assembly of the nanoparticle, and slow release of drug into aqueous media (up to 24 days) for the model HDACi panobinostat. We next constructed a library of CDNs to encapsulate various small, hydrophobic, terminally ionizable molecules (panobinostat, quisinostat, dacinostat, givinostat, bortezomib, camptothecin, nile red, and cytarabine), which yielded important insights into the structural requirements for effective drug loading and CDN self-assembly. Optimized CDN nanoparticles were taken up by GL261 cells in culture and a released panobinostat was confirmed to be bioactive. Panobinostat-loaded CDNs were next administered by convection-enhanced delivery (CED) to mice bearing intracranial GL261 tumors. These studies confirm that CDN encapsulation enables a higher deliverable dose of drug to effectively slow tumor growth. Matrix-assisted laser desorption/ionization (MALDI) analysis on tissue sections confirms higher exposure of tumor to drug, which likely accounts for the therapeutic effects. Taken in sum, these studies present a novel nanocarrier platform for encapsulation of HDACi via both ionic and hydrophobic interactions, which is an important step toward better treatment of disease via HDACi therapy.

Use of α-cyclodextrin to Promote Clean and Environmentally Friendly Disinfection of Phenolic Substrates via Chlorine Dioxide Treatment.

The use of chlorine dioxide to disinfect drinking water and ameliorate toxic components of wastewater has significant advantages in terms of providing safe water. Nonetheless, significant drawbacks toward such usage remain. These drawbacks include the fact that toxic byproducts of the disinfection agents are often formed, and the complete removal of such agents can be challenging. Reported herein is one approach to solving this problem: the use of α-cyclodextrin to affect the product distribution in chlorine dioxide-mediated decomposition of organic pollutants. The presence of α-cyclodextrin leads to markedly more oxidation and less aromatic chlorination, in a manner that is highly dependent on analyte structure and other reaction conditions. Mechanistic hypotheses are advanced to explain the cyclodextrin effect, and the potential for use of α-cyclodextrin for practical wastewater treatment is also discussed.

Synthetic Access to Functionalized Dipolarophiles of Lewis Basic Complexant Scaffolds through Sonogashira Cross-Coupling.

Soft Lewis basic complexants that facilitate selective removal of discrete ions resident in spent nuclear fuel can decrease repository volume and radiotoxicity and are of significant interest. Optimization of chelation efficacy is predicated on modular access to synthons to rapidly evaluate structure-activity relationships. The following work highlights efficient access to functionalized synthons for use as potential dipolarophiles in subsequent cycloaddition processes via Sonogashira coupling of 3-(6-bromo-pyridin-2-yl)-[1,2,4]triazine scaffolds. The 41 examples explored during method development evaluated electrophile and nucleophile diversity affording the desired coupled products in 31-96% isolated yield. Method optimization, substrate scope, a scale-up reaction, and downstream product functionalization are reported herein.

Cyclodextrin-Based Pseudorotaxanes: Easily Conjugatable Scaffolds for Synthesizing Hyperpolarized Xenon-129 Magnetic Resonance Imaging Agents.

Hyperpolarized (HP) xenon-129 (Xe) magnetic resonance (MR) imaging has the potential to detect biological analytes with high sensitivity and high resolution when coupled with xenon-encapsulating molecular probes. Despite the development of numerous HP Xe probes, one of the challenges that has hampered the translation of these agents from in vitro demonstration to in vivo testing is the difficulty in synthesizing the Xe-encapsulating cage molecule. In this study, we demonstrate that a pseudorotaxane, based on a γ-cyclodextrin macrocycle, is easily synthesized in one step and is detectable using HyperCEST-enhanced 129Xe MR spectroscopy.

Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions.

Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of N-substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of N-cyclohexylmaleimide with a methyl-ß-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond. The results reported herein represent a new mechanism for cyclodextrin-promoted Diels Alder reactions, and have significant potential applications in the development of other cyclodextrin-promoted organic transformations. Moreover, the ability to deplanarize polycyclic aromatic hydrocarbons (PAHs) under mild conditions, as demonstrated herein, has significant applications for PAH detoxification.