A novel tyrosine kinase inhibitor restores chondrocyte differentiation and promotes bone growth in a gain-of-function Fgfr3 mouse model.

Activating germline fibroblast growth factor receptor 3 (FGFR3) mutations cause achondroplasia (ACH), the most common form of human dwarfism and a spectrum of skeletal dysplasias. FGFR3 is a tyrosine kinase receptor and constitutive FGFR3 activation impairs endochondral ossification and triggers severe disorganization of the cartilage with shortening of long bones. To decipher the role of FGFR3 in endochondral ossification, we analyzed the impact of a novel tyrosine kinase inhibitor (TKI), A31, on both human and mouse mutant FGFR3-expressing cells and on the skeleton of Fgfr3(Y367C/+) dwarf mice. We found that A31 inhibited constitutive FGFR3 phosphorylation and restored the size of embryonic dwarf femurs using an ex vivo culture system. The increase in length of the treated mutant femurs was 2.6 times more than for the wild-type. Premature cell cycle exit and defective chondrocyte differentiation were observed in the Fgfr3(Y367C/+) growth plate. A31 restored normal expression of cell cycle regulators (proliferating cell nuclear antigen, KI67, cyclin D1 and p57) and allowed pre-hypertrophic chondrocytes to properly differentiate into hypertrophic chondocytes. Our data reveal a specific role for FGFR3 in the cell cycle and chondrocyte differentiation and support the development of TKIs for the treatment of FGFR3-related chondrodysplasias.

Synthesis and biological evaluation of potential new inhibitors of the bacterial transferase MraY with a ß-ketophosphonate structure.

Stable analogs of bacterial transferase MraY substrate or product with a pyrophosphate surrogate in their structure are described. ß-ketophosphonates were designed as pyrophosphate bioisosteres and were investigated as UDP-GlcNAc mimics. The developed strategy allows introduction of structural diversity at a late stage of the synthesis. The biological activity of the synthesized compounds was evaluated on the MraY enzyme.

Synthesis and biological evaluation of a diazepanone-based library of liposidomycins analogs as MraY inhibitors.

New inhibitors of the bacterial tranferase MraY are described. A scaffold strategy based on the diazepanone central core of liposidomycins, natural inhibitors of MraY has been developed. It involves the introduction of key structural fragments required for biological activity on enantiopure diazepanones by reductive amination, esterification and glycosylation. Biological evaluation of these compounds on MraY enzyme revealed interesting inhibitory activity for compounds displaying three fragments on the scaffold: a palmitoyl chain, an aminoribose part and an alkyluracil moiety. The inhibitors were also evaluated on MurG enzyme. The best compounds resulted in inhibition with IC50 values in the 100 µM range for one or the other enzyme.

Synthesis of purin-2-yl and purin-6-yl-aminoglucitols as C-nucleosidic ATP mimics and biological evaluation as FGFR3 inhibitors.

Two new series of C-nucleosidic ATP mimics have been synthesized using an efficient and versatile synthetic pathway. These compounds were designed as FGFR3 inhibitors using purine as a central scaffold. The two substituents, a polyhydroxylated ribose mimic and a lipophilic moiety, were linked either in position 2 or 6 of the purine ring in order to explore any possible binding mode. All the compounds were able to inhibit FGFR3 kinase activity at a concentration of 50 µM. Unexpectedly, the best inhibitor was found to be one of the synthetic intermediates 13 bearing an iodine atom in position 2. Docking studies have confirmed its location in the ATP binding site and revealed halogen bonding among key interactions.

Bacterial transferase MraY inhibitors: synthesis and biological evaluation.

New inhibitors of the bacterial transferase MraY are described. Their structure is based on an aminoribosyl-O-uridine like scaffold, readily obtained in two key steps. The amino group can be coupled with proline or guanylated. Alternatively, these amino, prolinyl or guanidinyl groups can be introduced through a triazole linker. Biological evaluation of these compounds on MraY from Bacillus subtilis revealed interesting inhibitory activity for both amino compounds.

Synthesis and biological evaluation of a triazole-based library of pyrido[2,3-d]pyrimidines as FGFR3 tyrosine kinase inhibitors.

A library of pyrido[2,3-d]pyrimidines was designed as inhibitors of FGFR3 tyrosine kinase allowing possible interactions with an unexploited region of the ATP binding-site. This library was built-up with an efficient step of click-chemistry giving easy access to triazole-based compounds bearing a large panel of substituents. Among the 27 analogues synthesized, more than half exhibited 55-89% inhibition of in vitro FGFR3 kinase activity at 2 microM and one (19g) was able to inhibit auto-phosphorylation of mutant FGFR3-K650M in transfected HEK cells.

Mono, di and tri-mannopyranosyl phosphates as mannose-1-phosphate prodrugs for potential CDG-Ia therapy.

An efficient and convergent method for the synthesis of mannose-1-phosphate prodrugs is described as a potential therapy for congenital disorders of glycosylation-Ia (CDG-Ia). The key feature of the proposed approach is the silver assisted nucleophilic substitution of 2,3,4,6-tetra-O-protected-alpha-d-mannopyranosyl bromides with various silver phosphate salts to afford mono, di, and tri-mannopyranosyl phosphates. A preliminary biological evaluation of the synthesized phosphate prodrugs has been carried out.

Synthesis and glycosidase inhibitory activity of new hexa-substituted C8-glycomimetics.

BACKGROUND: Glycosidases are involved in several metabolic pathways and the development of inhibitors is an important challenge towards the treatment of diseases, such as diabetes, cancer and viral infections including AIDS. Thus, inhibition of intestinal alpha-glucosidases can be used to treat diabetes through the lowering of blood glucose levels, and alpha-glucosidase inhibitors are being marketed against type 2 (non-insulinodependent mellitus) diabetes (i.e.: Glyset or Diastabol, Basen and Glucor or Precose). RESULTS: In that context, new C8-carbasugars and related aminocyclitols have been targeted in order to study the effect of the enhanced flexibility and of the new spatial distribution displayed by these structures on their adaptability in the active site of the enzymes. The synthesis of these new C8-glycomimetics is described from enantiomerically pure C2-symmetrical polyhydroxylated cyclooctenes. Their obtention notably involved a syn-dihydroxylation, and more extended functionalization through formation of a cis-cyclic sulfate followed by amination and subsequent reductive amination. This strategy involving the nucleophilic opening of a cis-cyclic sulfate by sodium azide is to our knowledge the first example in C8-series. It revealead to be an efficient alternative to the nucleoplilic opening of an epoxide moiety which proved unsuccessful in this particular case, due to the hindered conformation of such epoxides as demonstrated by X-ray cristallographic analysis. CONCLUSION: The biological activity of the synthesized glycomimetics has been evaluated towards 24 commercially available glycosidases. The weak observed activities can probably be related to the spatial disposition of the hydroxy and amino groups which depart too much from that realized in glycomimetics such as valiolamine, voglibose and valienamine. Nevertheless, the synthetic strategy described here is efficient and general, and could be extended to increase the diversity of the glycosidase inhibitors obtained since this diversity is introduced in an ultimate step of the synthesis.

Synthesis of polyhydroxylated piperidines and evaluation as glycosidase inhibitors.

A series of 16 new chiral nonracemic polyhydroxylated piperidines was synthesized utilizing several chiral beta-amino-alcohols. They act as a nitrogen source, chirality inducer and iminium stabilizer, in the desymmetrization of meso-trihydroxylated glutaraldehyde. The biological activity of these compounds towards several glycosidases (alpha-D-glucosidase, alpha-D-mannosidase, alpha-L-fucosidase) has been evaluated.