Design, Synthesis, and Structure−Affinity Relationships of Novel Series of Sialosides as CD22-Specific Inhibitors

Abstract

Sialosides incorporating substituted amides or amines at 9-position of sialic acid moiety have been synthesized and evaluated as CD22 inhibitors. Several derivatives exhibited inhibitory potency in sub- to low micromolar range (e. g., 8o, 9d, 9g, and 9k showed IC 50 values 0.40, 0.47, 0.24, and 0.23 microM, respectively, for hCD22, while 8p, 8q, and 9f, showed IC 50 values 1.70, 2.90, and 4.10 microM, respectively, for mCD22). The most significant result was the strongly enhanced affinity of 9g and 9k containing 9-(2' or 4'-hydroxy-4-biphenyl) methylamino substituents (600-fold more potent for hCD22 than the corresponding 9-hydroxy derivative; 7a). Molecular modeling study was carried out to get some insights into the molecular basis of CD22 inhibition. To the best of our knowledge, this is the first systematic structure-affinity relationship study on inhibition of CD22.

From a Library of MAG Antagonists to Nanomolar CD22 Ligands

“…[20] Moreover, Kiso and co-workers have reported ligands with phenyl, benzyl, and biphenylmethyl substituents at the reducing end. [21] Regarding the 5-position, van Rossenberg et al showed that sterically demanding acyl groups, such as benzoyl and long aliphatic chains such as octanoyl, decrease affinity, [18] whereas hydroxyacetyl is well accepted.…”

“…Based on the screening hits 9 c and 9 k as well as published data on CD22 ligands, [20] compound 13 a, [28] with biphenylcarboxamide at the 9-position and a benzyl aglycone, was considered as the starting point for our optimization campaign. Our goal was not only to elucidate the kinetic and thermodynamic profile Table 1.…”

“…When this extension in the 9-position was applied to the disaccharide epitope, ligands such as 5 and 6 exhibiting sub-micromolar affinities were identified. [20] Finally, benzyl substituents at the reducing end of the disaccharide epitope led to a further improvement in affinity. [19,21] When testing in B-cell based assays, a further aspect, the socalled density-dependent binding, must be considered.…”

Methyl 2,3,6-tri-O-Benzoyl-4-O-(tert-butyldimethylsilyl)-β-d-galactopyranoside

“…This product was then benzoylated at the 2-and 3-positions using benzoyl chloride in the presence of pyridine [11] to give methyl 4,6-O-benzylidene-2,3-di-O-benzoyl-β-D-galactopyranoside (3) as a white solid (50%). The benzylidene group was then removed using acetic acid in water (8:2 v/v) to give methyl 2,3-di-O-benzoyl-β-D-galactopyranoside (4) as a white solid (58%) [12]. Next, regioselective benzoylation gave methyl 2,3,6-tri-O-benzoyl-β-D-galactopyranoside (5) as an off-white solid (80%).…”

Extensive crosslinking of CD22 by epratuzumab triggers BCR signaling and caspase-dependent apoptosis in human lymphoma cells

“…Thus, besides the routine measurement of intracellular calcium as a marker for B-cell activation and cell surface binding to assess the affinity for CD22, the biological significance of CD22-targeting agents, particularly those derived from synthetic sialosides, 40,41,[45][46][47] should be substantiated with a suitable cytotoxicity assay, as exemplified by the capability of liposomal nanoparticles displaying both antigen and CD22L to induce antigen-specific B-cell apoptosis. 5 mg/mL; GAH, 10 mg/mL), and Wet-III (lane 7; hLL2, 7.5 mg/mL; GAH, 10 mg/mL; anti-IgM, 1 mg/mL).…”