Exploring N-Arylsulfonyl-l-proline Scaffold as a Platform for Potent and Selective αvβ1 Integrin Inhibitors

Abstract

ABSTRACT:One small molecule inhibitor of αvβ1 integrin, c8, shows antifibrotic effects in multiple in vivo mouse models. Here we synthesized c8 analogues and systematically investigate their structure−activity relationships (SAR) in αvβ1 integrin inhibition. N-Phenylsulfonyl-L-homoproline analogues of c8 maintained excellent potency against αvβ1 integrin while retaining good selectivity over other RGD integrins. In addition, 2-aminopyridine or cyclic guanidine analogues were shown to be equally potent to c8. A rigid phenyl linker increased the potency compared to c8, but the selectivity over other RGD integrins diminished. These results can provide further insights on design of αvβ1 integrin inhibitors as antifibrotics.KEYWORDS: Fibrosis, αvβ1 integrin, phenylsulfonylproline, TGFβ, integrin antagonist I ntegrins are transmembrane proteins that mediate cell−cell and cell−extracellular matrix (ECM) interactions.1 They exist as heterodimeric proteins consisting of an alpha (α) and beta (β) subunit. Multiple isoforms of each subunit have been identified so far with more than half of the integrins containing either the alpha v (αv) or beta 1 (β1) subunit.2 Due to their crucial biological roles in cell adhesion and proliferation, integrins have been extensively studied as therapeutic targets in cardiovascular diseases as well as cancer chemotherapy, and a few integrin inhibitors have reached the clinic.3 Integrins are also involved in the activation of TGFβ, a key cytokine in fibrotic diseases. An antibody against the epithelium-specific αvβ6 integrin (STX-100) is in phase II clinical trials for idiopathic pulmonay fibrosis (IPF). 4 We recently identified a role for another integrin, αvβ1, in activating TGFβ to drive organ fibrosis.5,6 A prototype inhibitor, c8, significantly reduced the fibrotic markers in mouse model for liver and lung fibrosis (Figure 1). These findings suggest that inhibitors of αvβ1 integrin could be promising new antifibrotic agents. However, αvβ1 integrin has not been widely studied, and little structural information on αvβ1 integrin is known. To our knowledge, no other selective and potent αvβ1 integrin inhibitors have been developed so far. Thus, we turned our attention to developing antifibrotic agents based upon modification of c8. Structurally, c8 (and its congener c6) mimics the natural ligand tripeptide sequence Arg-Gly-Asp (RGD) by connecting carboxylic acid and guanidinine through a linker. c8 also contains Narylsulfonyl-L-proline scaffold previously shown to confer specificity and potency in inhibition of other β1 integrins (α2β1 and α4β1). 7−10Based upon this analysis, we first investigated how the structural modification in N-arylsulfonyl-L-prolyl group would influence the potency (Figure 2). It was previously shown that a number of aryl or prolyl analogues in the same N-arylsulfonyl-Lprolyl scaffold were identified as potent non-RGD β1 integrin inhibitors. 8,9,11 However, it remains unclear if it holds true in the case of RGD integrin inhibitors like c8. Second, we were

Thrombospondin-1 regulation of latent TGF-β activation: A therapeutic target for fibrotic disease

“…Another integrin antagonist, the cyclic peptide that targets β v β 3 and β v β 5 , Cilengitide, recently failed in trials of aggressive glioblastoma and importantly, there was no correlation of p-Smad 2 levels with Cilengitide treatment in this disease for reasons that are not clear [88]. There is a small molecule inhibitor of β v β 1 (C8) which blocks fibrosis in several organs including the renal unilateral ureteral obstruction (UUO) model, although the relevance of this integrin to diabetic nephropathy has not yet been established [89, 90].…”

RGD-Binding Integrins in Head and Neck Cancers

“…Cooperative use of αvβ1, αvβ6 and α5β1 integrins to adhere and migrate on fibronectin has previously been reported by Koivisto and colleagues [ 89 ]. The development of novel selective small molecules binding αvβ1 [ 90 , 91 ], and αvβ6 and/or αvβ8 [ 92 , 93 ] provides the tools required to further investigate the effect of their inhibition in HNSCC and the design of potential new therapeutic and imaging agents.…”

Initial osteoblast adhesion and subsequent differentiation on zirconia surfaces are regulated by integrins and heparin-sensitive molecule

“…We next analyzed relation of integrin α 2 β 1 , a representative integrin non-RGD type heterodimer in osteoblasts. 26,27 Control IgG reduced absorbance when compared with non-treated samples, and blocking of α 2 β 1 by MAB1998 was enhanced more than in non-treated samples in Y-TZP, CpTi and Plate groups ( Figure 8C and D). Enhanced absorbance in NANOZR was not significant compared to other groups ( Figure 8C), suggesting that suppression of proliferation via α 2 β 1 is more functional in Y-TZP, CpTi and Plate, but less functional in NANOZR.…”