No abstract

Combinatorial libraries of rearranged hypervariable V(H) and V(L) sequences from nonimmunized human donors contain antigen specificities, including anti-self reactivities, created by random pairing of V(H)s and V(L)s. Somatic hypermutation of immunoglobulin genes, however, is critical in the generation of high-affinity antibodies in vivo and occurs only after immunization. Thus, in combinatorial phage display libraries from nonimmunized donors, high-affinity antibodies are rarely found. Lengthy in vitro affinity maturation is often needed to improve antibodies from such libraries. We report the construction of human Fab libraries having a unique combination of immunoglobulin sequences captured from human donors and synthetic diversity in key antigen contact sites in heavy-chain complementarity-determining regions 1 and 2. The success of this strategy is demonstrated by identifying many monovalent Fabs against multiple therapeutic targets that show higher affinities than approved therapeutic antibodies. This very often circumvents the need for affinity maturation, accelerating discovery of antibody drug candidates.

Background: Unregulated plasma kallikrein proteolytic activity can result from C1-inhibitor deficiency, causing excessive and potentially fatal edema.Results: The antibody DX-2930 potently and specifically inhibits plasma kallikrein and exhibits a long plasma half-life.Conclusion: An antibody protease inhibitor can lead to potent and specific bioactivity.Significance: DX-2930 could be an effective therapeutic for the prophylactic inhibition of plasma kallikrein-mediated diseases.

ADAMTS-4 and ADAMTS-Aggrecanase-mediated degradation of aggrecan, the major aggregating proteoglycan of articular cartilage, is an early and sustained feature of osteoarthritis (OA (3, 4). Because of their preference for Glu at P1, both ADAMTS-4 and -5 are considered glutamyl endoproteinases. Whereas ADAMTS-5 is constitutively expressed in human cartilage, ADAMTS-4 is inducible by a number of inflammatory cytokines, such as interleukin-1␤ and tumor necrosis factor-␣ (5). Gene knockout of ADAMTS-5, but not ADAMTS-4, expression in mice has been shown to be chondroprotective in a surgical mouse model of OA (6, 7), yet in human OA cartilage explants both ADAMTS-4 and ADAMTS-5 mediate aggrecan breakdown (8). Inhibition of ADAMTS-4 and ADAMTS-5 activity may represent a viable option for slowing down the progression of cartilage deterioration in OA.Alignment of the known sequences flanking the ADAMTS-4 cleavage sites in the proteoglycan substrates, aggrecan, versican, and brevican, led to the proposal of a 24-amino acid consensus motif (9). Not surprisingly, a glutamic acid residue occupied P1 (100% conserved) with P2Ј occupied by the basic amino acids, Arg or Lys. The authors speculated that activity of ADAMTS family members toward proteoglycan substrates was primarily dictated by an extended 23-amino acid motif N-terminal to the scissile bond, and a short 3-amino acid motif downstream of the site of cleavage. However, unlike the scissile bonds in the aggregating proteoglycans, the site of ADAMTS-4 proteolysis in ␣ 2 -macroglobulin (␣ 2 M) is Met 690 /Gly 691 , with no requirement for Glu at P1 (10). Yet, P1Ј to P3Ј in ␣ 2 M, Gly-Arg-Gly, is remarkably similar to downstream sequences in aggrecan and brevican, implying that PЈ amino acids may be more important in recognition and catalysis than sequences upstream of the scissile bond. ADAMTS-4 has also been shown * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The therapeutic management of antibody-mediated autoimmune disease typically involves immunosuppressant and immunomodulatory strategies. However, perturbing the fundamental role of the neonatal Fc receptor (FcRn) in salvaging IgG from lysosomal degradation provides a novel approach – depleting the body of pathogenic immunoglobulin by preventing IgG binding to FcRn and thereby increasing the rate of IgG catabolism. Herein, we describe the discovery and preclinical evaluation of fully human monoclonal IgG antibody inhibitors of FcRn. Using phage display, we identified several potent inhibitors of human-FcRn in which binding to FcRn is pH-independent, with over 1000-fold higher affinity for human-FcRn than human IgG-Fc at pH 7.4. FcRn antagonism in vivo using a human-FcRn knock-in transgenic mouse model caused enhanced catabolism of exogenously administered human IgG. In non-human primates, we observed reductions in endogenous circulating IgG of >60% with no changes in albumin, IgM, or IgA. FcRn antagonism did not disrupt the ability of non-human primates to mount IgM/IgG primary and secondary immune responses. Interestingly, the therapeutic anti-FcRn antibodies had a short serum half-life but caused a prolonged reduction in IgG levels. This may be explained by the high affinity of the antibodies to FcRn at both acidic and neutral pH. These results provide important preclinical proof of concept data in support of FcRn antagonism as a novel approach to the treatment of antibody-mediated autoimmune diseases.