IL-17A is a pro-inflammatory cytokine that has been implicated in autoimmune and inflammatory diseases. Monoclonal antibodies inhibiting IL-17A signaling have demonstrated remarkable efficacy, but an oral therapy is still lacking. A high affinity IL-17A peptide antagonist (HAP) of 15 residues was identified through phage-display screening followed by saturation mutagenesis optimization and amino acid substitutions. HAP binds specifically to IL-17A and inhibits the interaction of the cytokine with its receptor, IL-17RA. Tested in primary human cells, HAP blocked the production of multiple inflammatory cytokines. Crystal structure studies revealed that two HAP molecules bind to one IL-17A dimer symmetrically. The N-terminal portions of HAP form a β-strand that inserts between two IL-17A monomers while the C-terminal section forms an α helix that directly blocks IL-17RA from binding to the same region of IL-17A. This mode of inhibition suggests opportunities for developing peptide antagonists against this challenging target.

A solid-phase route affording novel 3,5-disubstituted 1,5-benzothiazepin-4(5H)-ones in optically pure form has been enabled. SNAr reaction of polymer-bound 4-fluoro-3-nitrobenzoic acid, 12, with l-Fmoc-cysteine, l-13, under basic conditions, followed by tin(II) chloride mediated nitro group reduction, furnished the primary aniline 15. Reductive alkylation of 15 to the corresponding secondary anilines 17 was shown to be feasible for a wide range of aldehydes, using an optimized solvent system composed of CH(OMe)3, DMF, MeOH, and HOAc, with NaCNBH3 as the reducing agent. In cases of enolizable aldehydes, benzotriazole was found to be a beneficial additive for the suppression of side-products due to imine−enamine tautomerization. Subsequent cyclization of the secondary anilines 17 using DIC in apolar solvents furnished the corresponding N(5)-alkylated 1,5-benzothiazepin-4-ones 19. Following Fmoc removal from 19, the primary amino group was finally reacted with carboxylic acids, isocyanates, sulfonyl chlorides, or aldehydes to afford the respective amides 32, ureas 33, sulfonamides 34, or secondary amines 35. Performing the synthesis with the d-form of Fmoc-cysteine, d-13, resulted in the corresponding antipodal products, with no detectable scrambling at C(3). The solid-phase assembly of 1,5-benzothiazepin-4-ones was also shown to be compatible with chemical encoding based on dialkylamine tags, enabling the construction of large combinatorial libraries of the title compounds.

A synthetic strategy that allows for the site-specific attachment of polymers such as poly(ethylene glycol) (PEG) to protein pharmaceuticals is described. PEG was attached to a 67-amino acid fully synthetic CCL-5 (RANTES) analogue at its GAG binding site both to reduce aggregation and to increase the circulating lifetime. Effective protection of an Aoaa chemoselective linker during peptide assembly, total chemical protein synthesis, and protein folding was achieved with an isopropylidene group. Mild deprotection of the resulting folded synthetic protein and subsequent polymer attachment occur without interference with the native folded structure and activity.

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