Anne Marinier

Rational design of RAR-selective ligands revealed by RARβ crystal stucture

The crystal structure of the ligand‐binding domain of RARβ, a suspect tumour suppressor, reveals important features that distinguish it from the two other RAR isotypes. The most striking difference is an extra cavity allowing RARβ to bind more bulky agonists. Accordingly, we identified a ligand that shows RARβ selectivity with a 100‐fold higher affinity to RARβ than to α or γ isotypes. The structural differences between the three RAR ligand‐binding pockets revealed a rationale explaining how a single retinoid can be at the same time an RARα, γ antagonist and an RARβ agonist. In addition, we demonstrate how to generate an RARβ antagonist by gradually modifying the bulkiness of a single substitution. Together, our results provide structural guidelines for the synthesis of RARβ‐selective agonists and antagonists, allowing for the first time to address pharmacologically the tumour suppressor role of RARβ in vitro and in animal models.

Identification of small molecules that support human leukemia stem cell activity ex vivo

Leukemic stem cells (LSCs) are considered a major cause of relapse in acute myeloid leukemia (AML). Defining pathways that control LSC self-renewal is crucial for a better understanding of underlying mechanisms and for the development of targeted therapies. However, currently available culture conditions do not prevent spontaneous differentiation of LSCs, which greatly limits the feasibility of cell-based assays. To overcome these constraints we conducted a high-throughput chemical screen and identified small molecules that inhibit differentiation and support LSC activity in vitro. Similar to reports with cord blood stem cells, several of these compounds suppressed the aryl-hydrocarbon receptor (AhR) pathway, which we show to be inactive in vivo and rapidly activated ex vivo in AML cells. We also identified a compound, UM729, that collaborates with AhR suppressors in preventing AML cell differentiation. Together, these findings provide newly defined culture conditions for improved ex vivo culture of primary human AML cells.

E2 enzyme inhibition by stabilization of a low-affinity interface with ubiquitin

Weak protein interactions between ubiquitin and the ubiquitin-proteasome system (UPS) enzymes that mediate its covalent attachment to substrates serve to position ubiquitin for optimal catalytic transfer. We show that a small molecule inhibitor of the E2 ubiquitin conjugating enzyme Cdc34A, called CC0651, acts by trapping a weak interaction between ubiquitin and the E2 donor ubiquitin binding site. A structure of the ternary CC0651-Cdc34A-ubiquitin complex reveals that the inhibitor engages a composite binding pocket formed from Cdc34A and ubiquitin. CC0651 also suppresses the spontaneous hydrolysis rate of the Cdc34A-ubiquitin thioester, without overtly affecting the interaction between Cdc34A and the RING domain subunit of the E3 enzyme. Stabilization of the numerous other weak interactions between ubiquitin and UPS enzymes by small molecules may be a feasible strategy to selectively inhibit different UPS activities.

Sordaricin antifungal agents

Compounds based on sordaricin were prepared via organometallic addition onto a fully protected sordaricin aldehyde. The fungal growth inhibition profiles for these compounds were established and the results are presented here. The synthesis of homologated sordaricin as well as ether and ester derivatives is presented, and structural rearrangement products upon oxidation. These compounds were evaluated as agents to inhibit fungal growth.

Novel Tricyclic Inhibitors of IκB Kinase

The design and synthesis of a novel series of oxazole-, thiazole-, and imidazole-based inhibitors of IkappaB kinase (IKK) are reported. Biological activity was improved compared to the pyrazolopurine lead, and the expedient synthesis of the new tricyclic systems allowed for efficient exploration of structure-activity relationships. This, combined with an iterative rat cassette dosing strategy, was used to identify compounds with improved pharmacokinetic (PK) profiles to advance for in vivo evaluation.

Novel mimics of sialyl Lewis X: design, synthesis and biological activity of a series of 2- and 3-malonate substituted galactoconjugates.

A series of potent inhibitors of P-selectin as potential anti-inflammatory agents is reported. These compounds are derivatives of galactocerebrosides bearing a malonate side chain in positions 2 and 3 of the galactose moiety. Based on the binding mode of sialyl Lewis X, the two acidic groups of the malonate are designed to form ionic interactions with two important lysines in the active site of P-selectin, Lys113 and Lys111. On the other hand, the 4- and 6-hydroxy groups on the galactose ring are arranged to chelate the calcium ion in the P-selectin active site. The synthesis and the biological activity of this series of compounds are described. Lead compounds having a greater potency than sialyl Lewis X are identified.