Monoclonal antibodies against metzincin targets

Abstract

The metzincin clan of metalloproteinases includes the MMP, disintegrin and metalloproteinase (ADAM) and ADAM with thrombospondin motifs families, which cleave extracellular targets in a wide range of (patho)physiological processes. Antibodies constitute a powerful tool to modulate the activity of these enzymes for both therapeutic and research purposes. In this review, we give an overview of monoclonal antibodies (mAbs) that have been tested in preclinical disease models, human trials and important studies of metzincin structure and function. Initial attempts to develop therapeutic small molecule inhibitors against MMPs were hampered by structural similarities between metzincin active sites and, consequently, off-target effects. Therefore, more recently, mAbs have been developed that do not bind to the active site but bind to surface-exposed loops that are poorly conserved in closely related family members. Inhibition of protease activity by these mAbs occurs through a variety of mechanisms, including (i) barring access to the active site, (ii) disruption of exosite binding, and (iii) prevention of protease activation. These different modes of inhibition are discussed in the context of the antibodies' potency, selectivity and, importantly, the effects in models of disease and clinical trials. In addition, various innovative strategies that were used to generate anti-metzincin mAbs are discussed. LINKED ARTICLES: This article is part of a themed section on Translating the Matrix. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.1/issuetoc.

Figure 1

Schematic illustration of IgG and IgG fragments. IgGs are bivalent and consist of two heavy and two light chains, made of variable (V_H and V_L) and constant (C_H and C_L) regions. The heavy chain constant region is divided into C_H1, C_H2 and C_H3. The antigen binding site is composed of six hypervariable complementarity determining regions, three in the variable region of the heavy (V_H) and light (V_L) chains. The ‘fragment crystallizable’ (Fc) region is composed of the C_H2 and C_H3 constant regions of the antibody and mediates interactions with cell surface (Fc) receptors and the complement system. The antigen‐binding fragment (Fab) is composed of one constant and one variable region of each of the heavy and light chains (monovalent). It can be produced from an intact IgG by digestion with papain, or it can be expressed recombinantly. The scFv consists of single V_H and V_L regions connected by a flexible linker and is therefore monovalent. The scFv‐Fc is bivalent and consists of two scFvs connected to the Fc region of IgG. Yellow lines indicate disulfide bonds.

Figure 2

Domain organization of metzincins discussed in this review. S, signal peptide; Pro, prodomain; F, fibronectin type II repeats; H, hinge region; HPX, haemopexin domain; TM, transmembrane domain; CT, c‐terminal tail; Dis, disintegrin‐like domain; CR, cysteine‐rich domain; EGF‐L, EGF‐like domain; TS, thrombospondin type‐1‐like repeat; CUB, complement c1r/c1s, uegf, bmp1 domain; LAMG, laminin G‐like domain; ID, interdomain region. For tandem repeats, the number of repeats is shown in brackets. Note that the disintegrin‐like domains of ADAMs and ADAMTSs are structurally very different.

Figure 3

Structure of the catalytic domain (Cat) of MMP‐14. The Cat of members of the metzincin clan have a characteristic fold consisting of an active site groove that runs approximately along the axis of the central α‐helix beneath it, here shown horizontally at the centre of the domain. This active site helix also provides two of the three histidines that bind the catalytic zinc ion. Structural stability of MMP‐14 is provided by a second zinc ion (purple circle) and two calcium ions (green circles). Indicated are the membrane‐type (MT) loop (residues 163–170) and the VB‐loop (residues 218–233), which have been used for selective targeting by mAbs. PDB ID, 1BQQ (Fernandez‐Catalan et al., 1998).