Christophe Pardin

Cinnamoyl inhibitors of tissue transglutaminase.

Transglutaminases (TGases) catalyze the intermolecular cross-linking of certain proteins and tissue TGases (TG2) are involved in diverse biological processes. Unregulated, high TGase activities have been implicated in several physiological disorders, but few reversible inhibitors of TG2 have been reported. Herein, we report the synthesis of a series of novel trans-cinammoyl derivatives, discovered to be potent inhibitors of guinea pig liver transglutaminase. The most effective inhibitors evaluated can be sorted into two subclasses: substituted cinnamoyl benzotriazolyl amides and the 3-(substituted cinnamoyl)pyridines, referred to more commonly as azachalcones. Kinetic evaluation of both of these subclasses revealed that they display reversible inhibition and are competitive with acyl donor TGase substrates at IC50 values as low as 18 microM. An analysis of structure-activity relationships within these series of inhibitors permitted the identification of potentially important binding interactions. Further testing of some of the most potent inhibitors demonstrated their selectivity for TG2 and their potential for further development.

Reversible and Competitive Cinnamoyl Triazole Inhibitors of Tissue Transglutaminase

A series of 15 cinnamoyl triazole derivatives was prepared by Cu(I)‐catalyzed azide/alkyne [3+2]‐cycloaddition reactions and examined as inhibitors of guinea‐pig liver transglutaminase. Several compounds exhibited activity as reversible inhibitors that were competitive with acyl donor transglutaminase substrates. For example, triazole 4d has a Ki value of 174 nm and represents one of the most potent reversible transglutaminase inhibitors reported to date.

First-in-class small molecule potentiators of cancer virotherapy.

The use of engineered viral strains such as gene therapy vectors and oncolytic viruses (OV) to selectively destroy cancer cells is poised to make a major impact in the clinic and revolutionize cancer therapy. In particular, several studies have shown that OV therapy is safe and well tolerated in humans and can infect a broad range of cancers. Yet in clinical studies OV therapy has highly variable response rates. The heterogeneous nature of tumors is widely accepted to be a major obstacle for OV therapeutics and highlights a need for strategies to improve viral replication efficacy. Here, we describe the development of a new class of small molecules for selectively enhancing OV replication in cancer tissue. Medicinal chemistry studies led to the identification of compounds that enhance multiple OVs and gene therapy vectors. Lead compounds increase OV growth up to 2000-fold in vitro and demonstrate remarkable selectivity for cancer cells over normal tissue ex vivo and in vivo. These small molecules also demonstrate enhanced stability with reduced electrophilicity and are highly tolerated in animals. This pharmacoviral approach expands the scope of OVs to include resistant tumors, further potentiating this transformative therapy. It is easily foreseeable that this approach can be applied to therapeutically enhance other attenuated viral vectors.

Using Quenching Kinetics and Thermodynamics of Amino-Fluorophores as Empirical Tools for Predicting Boronic Acid Sensors Suitable for Use in Physiological Conditions

A series of water-soluble 1-amino-naphthalenes and 2-amino-fluorenes are prepared. These serve as model fluorophores for measuring the thermodynamics and kinetics of fluorescence quenching with phenylboronic acids and aliphatic amines. Steady-state and time-resolved fluorescence quenching kinetics are investigated using the Stern–Volmer method. Diffusion limited quenching constants and exergonic thermodynamics of electron transfer are derived for the 5-amino-1-napthol and 2-aminofluorene derivatives with phenylboronic acid and/or an aliphatic imine. No quenching and endergonic thermodynamics or electron transfer are observed for 5-sulfonamide, 5-sulfonic acid, or 5-hydroxy-7-sulfonic acid aminonaphthalene derivatives. Boronic acid sensors synthesized from these aminofluorophores by reductive amination with 2-formylphenylboronic acid undergo fluorescence revival in the presence of saccharides only when the fluorophore demonstrates diffusion limited quenching kinetics and exergonic thermodynamics of electron transfer with the boronic acid or imine quenchers. Thus, these two properties are suitable empirical tools for predicting saccharide-induced fluorescence revival of boronic acid sensors.

Towards a characterization of the structural determinants of specificity in the macrocyclizing thioesterase for deoxyerythronolide B biosynthesis.

Type I polyketide synthases (PKSs) are giant multidomain proteins that synthesize many therapeutics and other natural products. The synthesis proceeds by a thiotemplate mechanism whereby intermediates are covalently attached to the PKS. The release of the final polyketide is catalyzed by the terminal thioesterase (TE) domain through hydrolysis, transesterification, or macrocyclization. The PKS 6-deoxyerythronolide B synthase (DEBS) produces the 14-membered macrolide core of the clinically important antibiotic erythromycin. The TE domain of DEBS (DEBS TE) has well-established, empirically-defined specificities for hydrolysis or macrocyclization of native and modified substrates. We present efforts towards understanding the structural basis for the specificity of the thioesterase reaction in DEBS TE using a set of novel diphenyl alkylphosphonates, which mimic substrates that are specifically cyclized or hydrolyzed by DEBS TE. We have determined structures of a new construct of DEBS TE alone at 1.7Å, and DEBS TE bound with a simple allylphosphonate at 2.1Å resolution. Other, more complex diphenyl alkylphosphonates inhibit DEBS TE, but we were unable to visualize these faithful cyclization analogs in complex with DEBS TE. This work represents a first step towards using DEBS TE complexed with sophisticated substrate analogs to decipher the specificity determinants in this important reaction.