Rapid modifications of N-substitution in iminosugars: Development of new β-glucocerebrosidase inhibitors and pharmacological chaperones for Gaucher disease

Multivalent pyrrolidines acting as pharmacological chaperones against Gaucher disease

A concise asymmetric synthesis of clickable enantiomeric pyrrolidines was achieved using Crabbé-Ma allenation. The synthesized iminosugars were grafted by copper-free strain-promoted alkyne-azide cycloaddition onto phosphorus dendrimers. The hexavalent and dodecavalent pyrrolidines were evaluated as β-glucocerebrosidase inhibitors. The level of inhibition suggests that monofluorocyclooctatriazole group may contribute to the affinity for the protein leading to potent multivalent inhibitors. Docking studies were carried out to rationalize these results. Then, the iminosugars clusters were evaluated as pharmacological chaperones in Gaucher patients' fibroblasts. An increase in β-glucocerebrosidase activity was observed with hexavalent and dodecavalent pyrrolidines at concentrations as low as 1 µM and 0.1 µM, respectively. These iminosugar clusters constitute the first example of multivalent pyrrolidines acting as pharmacological chaperones against Gaucher disease.

Discovery of small-molecule protein stabilizers toward exogenous alpha-l-iduronidase to reduce the accumulated heparan sulfate in mucopolysaccharidosis type I cells

Synthesis of a series of l-iduronic acid (IdoA)- and imino-IdoA-typed C-glycosides for modulating α-l-iduronidase (IDUA) activity is described. In an enzyme inhibition study, IdoA-typed C-glycosides were more potent than imino-IdoA analogs, with the most potent IdoA-typed C-glycoside 27c showing an IC₅₀ value of 1 μM. On the other hand, co-treatment of 12 with rh-α-IDUA in mucopolysaccharidosis type I (MPS I) fibroblasts exhibited a nearly 3-fold increase of the IDUA activity, resulting in a clear reduction of the accumulated heparan sulfate (HS) compared to the exogenous enzyme treatment alone. This is the first report of small molecules facilitating IDUA stabilization, enhancing enzyme activity, and reducing accumulated HS in MPS I cell-based assays, which reveals that small molecules as rh-α-IDUA stabilizers to improve enzyme replacement therapy (ERT) efficacy toward MPS I is feasible and promising.

Harnessing polyhydroxylated pyrrolidines as a stabilizer of acid alpha-glucosidase (GAA) to enhance the efficacy of enzyme replacement therapy in Pompe disease

To discover small molecules as acid alpha-glucosidase (GAA) stabilizers for potential benefits of the exogenous enzyme treatment toward Pompe disease cells, we started from the initial screening of the unique chemical space, consisting of sixteen stereoisomers of 2-aminomethyl polyhydroxylated pyrrolidines (ADMDPs) to find out two primary stabilizers 17 and 18. Further external or internal structural modifications of 17 and 18 were performed to increase structural diversity, followed by the protein thermal shift study to evaluate the GAA stabilizing ability. Fortunately, pyrrolidine 21, possessing an l-arabino-typed configuration pattern, was identified as a specific potent rh-GAA stabilizer, enabling the suppression of rh-GAA protein denaturation. In a cell-based Pompe model, co-administration of 21 with rh-GAA protein significantly improved enzymatic activity (up to 5-fold) compared to administration of enzyme alone. Potentially, pyrrolidine 21 enables the direct increase of ERT (enzyme replacement therapy) efficacy in cellulo and in vivo.

An overview of therapeutic potential of N-alkylated 1-deoxynojirimycin congeners

Polyhydroxylated alkaloids display a wide range of biological activities, suggesting their use in the treatment of various diseases. Their most famous representative, 1-deoxynojirimycin (DNJ), is a natural product that shows α- and β-glucosidase inhibition. This molecule has been since converted into two clinically approved drugs i.e., Zavesca® and Glyset®, targeting type I Gaucher's disease and type II diabetes mellitus, respectively. This review examines the therapeutic potential of important DNJ congeners reported in last decade and presents concise mechanism of glycosidase inhibition. A brief overview of substituents conjugation's impact on DNJ scaffold (including N-alkylated DNJ derivatives, mono-valent, di-valent and multivalent DNJ congeners, N-[5-(adamantan-1-yl-methoxy)-pentyl]-1-deoxynojirimycin (AMP-DNM) look alike DNJ based lipophilic derivatives, AMP-DNM based neoglycoconjugates, DNJ click derivatives with varying carboxylic acids and aromatic moieties, conjugates of DNJ and glucose, and N-bridged DNJ analogues) towards various enzymes such as α/β glucosidase, porcine trehalase, as F508del-CFTR correctors, α-mannosidase, human placental β-glucocerebrosidase, N370S β-GCase, α-amylase and insect trehalase as potent and selective inhibitors have been discussed with potential bioactivities, which can provide inspiration for future studies.

Selective Golgi α-mannosidase II inhibitors: N-alkyl substituted pyrrolidines with a basic functional group

Enzymatic assays, molecular modeling and NMR studies of novel 1,4-dideoxy-1,4-imino-l-lyxitols provided new information on the GH38 family enzyme inhibitors and their selectivity.

Synthesis of multimeric pyrrolidine iminosugar inhibitors of human β-glucocerebrosidase and α-galactosidase A: First example of a multivalent enzyme activity enhancer for Fabry disease

The synthesis of a chemical library of multimeric pyrrolidine-based iminosugars by incorporation of three pairs of epimeric pyrrolidine-azides into different alkyne scaffolds via CuAAC is presented. The new multimers were evaluated as inhibitors of two important therapeutic enzymes, human α-galactosidase A (α-Gal A) and lysosomal β-glucocerebrosidase (GCase). Structure-activity relationships were established focusing on the iminosugar inhitope, the valency of the dendron and the linker between the inhitope and the central scaffold. Remarkable is the result obtained in the inhibition of α-Gal A, where one of the nonavalent compounds showed potent inhibition (0.20 μM, competitive inhibition), being a 375-fold more potent inhibitor than the monovalent reference. The potential of the best α-Gal A inhibitors to act as pharmacological chaperones was analyzed by evaluating their ability to increase the activity of this enzyme in R301G fibroblasts from patients with Fabry disease, a genetic disorder related with a reduced activity of α-Gal A. The best enzyme activity enhancement was obtained for the same nonavalent compound, which increased 5.2-fold the activity of the misfolded enzyme at 2.5 μM, what constitutes the first example of a multivalent α-Gal A activity enhancer of potential interest in the treatment of Fabry disease.

Synthesis and glycosidase inhibition of N-substituted derivatives of 1,4-dideoxy-1,4-imino-d-mannitol (DIM)

Four series of N-substituted DIMs have been synthesized and assayed against glycosidases to provide continuous and reliable inhibitory spectra.

Dual targeting of PTP1B and glucosidases with new bifunctional iminosugar inhibitors to address type 2 diabetes

The diffusion of type 2 diabetes (T2D) throughout the world represents one of the most important health problems of this century. Patients suffering from this disease can currently be treated with numerous oral anti-hyperglycaemic drugs, but none is capable of reproducing the physiological action of insulin and, in several cases, they induce severe side effects. Developing new anti-diabetic drugs remains one of the most urgent challenges of the pharmaceutical industry. Multi-target drugs could offer new therapeutic opportunities for the treatment of T2D, and the reported data on type 2 diabetic mice models indicate that these drugs could be more effective and have fewer side effects than mono-target drugs. α-Glucosidases and Protein Tyrosine Phosphatase 1B (PTP1B) are considered important targets for the treatment of T2D: the first digest oligo- and disaccharides in the gut, while the latter regulates the insulin-signaling pathway. With the aim of generating new drugs able to target both enzymes, we synthesized a series of bifunctional compounds bearing both a nitro aromatic group and an iminosugar moiety. The results of tests carried out both in vitro and in a cell-based model, show that these bifunctional compounds maintain activity on both target enzymes and, more importantly, show a good insulin-mimetic activity, increasing phosphorylation levels of Akt in the absence of insulin stimulation. These compounds could be used to develop a new generation of anti-hyperglycemic drugs useful for the treatment of patients affected by T2D.

Exploring substituent diversity on pyrrolidine-aryltriazole iminosugars: Structural basis of β-glucocerebrosidase inhibition

The synthesis of a library of pyrrolidine-aryltriazole hybrids through CuAAC between two epimeric dihydroxylated azidomethylpyrrolidines and differently substituted phenylacetylenes is reported. The evaluation of the new compounds as inhibitors of lysosomal β-glucocerebrosidase showed the importance of the substitution pattern of the phenyl moiety in the inhibition. Crystallization and docking studies revealed key interactions of the pyrrolidine motif with aminoacid residues of the catalytic site while the aryltriazole moiety extended along a hydrophobic surface groove. Some of these compounds were able to increase the enzyme activity in Gaucher patient fibroblasts, acting as a new type of chemical chaperone for Gaucher disease.

A combinatorial approach towards the synthesis of non-hydrolysable triazole–iduronic acid hybrid inhibitors of human α-l-iduronidase: discovery of enzyme stabilizers for the potential treatment of MPSI

Synthesis and bioevaluation of substituent-diverse triazole–iduronic acid hybrid molecules are highlighted.

Synthesis of 1-Deoxynojirimycin: Exploration of Optimised Conditions for Reductive Amidation and Separation of Epimers

1-Deoxynojirimycin (DNJ), which has importance with respect to sugar processing enzymes, is a synthetic target for chemists. A key step in the synthesis of DNJ is the preparation of 2,3,4,6-tetra- O-benzyl-D-glucono-δ-lactam. By varying reaction parameters such as temperature, solvent and reducing reagent, improvements on previous methods are described. A novel approach for the synthesis of 2,3,4,6-tetra- O-benzyl-5-dehydro-5-deoxo-D-gluconamide has been developed by using PCC as an oxidising agent. Separation of epimers permitted DNJ to be obtained in 85% yield after reduction and hydrogenolysis steps.

Glycomimetic-based pharmacological chaperones for lysosomal storage disorders: lessons from Gaucher, GM1-gangliosidosis and Fabry diseases

Lysosomal storage disorders (LSDs) are often caused by mutations that destabilize native folding and impair the trafficking of enzymes, leading to premature endoplasmic reticulum (ER)-associated degradation, deficiencies of specific hydrolytic functions and aberrant storage of metabolites in the lysosomes. Enzyme replacement therapy (ERT) and substrate reduction therapy (SRT) are available for a few of these conditions, but most remain orphan. A main difficulty is that virtually all LSDs involve neurological decline and neither proteins nor the current SRT drugs can cross the blood-brain barrier. Twenty years ago a new therapeutic paradigm better suited for neuropathic LSDs was launched, namely pharmacological chaperone (PC) therapy. PCs are small molecules capable of binding to the mutant protein at the ER, inducing proper folding, restoring trafficking and increasing enzyme activity and substrate processing in the lysosome. In many LSDs the mutated protein is a glycosidase and the accumulated substrate is an oligo- or polysaccharide or a glycoconjugate, e.g. a glycosphingolipid. Although it might appear counterintuitive, substrate analogues (glycomimetics) behaving as competitive glycosidase inhibitors are good candidates to perform PC tasks. The advancements in the knowledge of the molecular basis of LSDs, including enzyme structures, binding modes, trafficking pathways and substrate processing mechanisms, have been put forward to optimize PC selectivity and efficacy. Moreover, the chemical versatility of glycomimetics and the variety of structures at hand allow simultaneous optimization of chaperone and pharmacokinetic properties. In this Feature Article we review the advancements made in this field in the last few years and the future outlook through the lessons taught by three archetypical LSDs: Gaucher disease, GM1-gangliosidosis and Fabry disease.

Bioevaluation of sixteen ADMDP stereoisomers toward alpha-galactosidase A: Development of a new pharmacological chaperone for the treatment of Fabry disease and potential enhancement of enzyme replacement therapy efficiency

A unique molecular library consisting of all sixteen synthetic ADMDP (1-aminodeoxy-DMDP) stereoisomers has been prepared and evaluated for inhibitory activity against α-Gal A, and ability to impart thermal stabilization of this enzyme. The results of this testing led us to develop a novel pharmacological chaperone for the treatment of Fabry disease. 3-Epimer ADMDP was found to be an effective pharmacological chaperone, able to rescue α-Gal A activity in the lymphoblast of the N215S Fabry patient-derived cell line, without impairment of cellular β-galactosidase activity. When 3-epimer ADMDP was administered with rh-α-Gal A (enzyme replacement therapy) for the treatment of Fabry patient-derived cell lines, improvements in the efficacy of rh-α-Gal A was observed, which suggests this small molecule can also provide clinical benefit of enzyme replacement therapy in Fabry disease.

Gem-difluoromethylated and trifluoromethylated derivatives of DMDP-related iminosugars: synthesis and glycosidase inhibition

Gem-difluoromethylated and trifluoromethylated derivatives of DMDP-related iminosugars have been synthesized from cyclic nitrones and assayed against various glycosidases.

Evidence for a multivalent effect in inhibition of sulfatases involved in lysosomal storage disorders (LSDs)

New targets sensitive to multivalency: synthesis of nonavalent pyrrolidine iminosugars.

Synthetic deoxynojirimycin derivatives bearing a thiolated, fluorinated or unsaturated N-alkyl chain: identification of potent α-glucosidase and trehalase inhibitors as well as F508del-CFTR correctors

Synthetic DNJs bearing a thiolated, fluorinated or unsaturated N-substituent exhibit trehalase inhibition or F508del-CFTR correction.