Design, Synthesis, and Structure−Activity Relationships of Macrocyclic Hydroxamic Acids That Inhibit Tumor Necrosis Factor α Release in Vitro and in Vivo

Abstract

To search for TNF-α (tumor necrosis factor α) converting enzyme (TACE) inhibitors, we designed a new class of macrocyclic hydroxamic acids by linking the P1 and P2‘ residues of acyclic anti-succinate-based hydroxamic acids. A variety of residues including amide, carbamate, alkyl, sulfonamido, Boc-amino, and amino were found to be suitable P1−P2‘ linkers. With an N-methylamide at P3‘, the 13−16-membered macrocycles prepared exhibited low micromolar activities in the inhibition of TNF-α release from LPS-stimulated human whole blood. Further elaboration in the P3‘−P4‘ area using the cyclophane and cyclic carbamate templates led to the identification of a number of potent analogues with IC₅₀ values of ≤0.2 μM in whole blood assay (WBA). Although the P3‘ area can accommodate a broad array of structurally diversified functional groups including polar residues, hydrophobic residues, and amino and carboxylic acid moieties, in both the cyclophane series and the cyclic carbamate series, a glycine residue at P3‘ was identified as a critical structural component to achieve both good in vitro potency and good oral activity. With a glycine residue at P3‘, an N-methylamide at P4‘ provided the best cyclophane analogue, SL422 (WBA IC₅₀ = 0.22 μM, LPS-mouse ED₅₀ = 15 mg/kg, po), whereas a morpholinylamide at P4‘ afforded the most potent and most orally active cyclic carbamate analogue, SP057 (WBA IC₅₀ = 0.067 μM, LPS-mouse ED₅₀ = 2.3 mg/kg, po). Further profiling for SL422 and SP057 showed that these macrocyclic compounds are potent TACE inhibitors, with K_i values of 12 and 4.2 nM in the porcine TACE assay, and are broad-spectrum MMP inhibitors. Pharmacokinetic studies in beagle dogs revealed that SL422 and SP057 are orally bioavailable, with oral bioavailabilities of 11% and 23%, respectively.