A potent human anti-eotaxin1 antibody, CAT-213: Isolation by phage display and in vitro and in vivo efficacy

The CC chemokine, eotaxin1(CCL11) is an important regulator of eosinophil function. A marked accumulation of eosinophils in tissues has been correlated with the up-regulation of eotaxin1 expression in several diseases. The potential therapeutic value of neutralizing the effects of eotaxin1 in inflammatory conditions ( including asthma) is under investigation. A human single-chain fragment variable antibody that neutralizes human eotaxin1 (CAT-212) was produced using antibody phage display and converted to whole antibody IgG4 format (CAT-213). A novel approach to lead optimization in which the length of the variable heavy chain complementarity-determining region 3 was reduced by one amino acid resulted in an increase in potency of > 1000-fold compared with the parent anti-eotaxin 1 antibody. The optimized antibody binds eotaxin1 with high affinity (80.4 pM) and specificity. CAT-213 and CAT-212 do not bind or neutralize a range of other human proteins including human monocyte chemoattractant protein-1, a structurally similar chemokine. CAT-213 neutralizes the ability of eotaxin1 to cause an increase in intracellular calcium signaling ( with an IC50 value of 2.86 nM), migration of CCR3-expressing L1.2 cells ( with an IC50 value of 0.48 nM), and inhibition of the eotaxin1-evoked shape change of human eosinophils in vitro ( with an IC50 of 0.71 nM). Local administration of CAT- 213 to mice (1-100 mu g kg(-1)) attenuates dermal eosinophilia induced by human eotaxin1, achieving > 90% inhibition of eosinophil influx. CAT- 213 may therefore be of therapeutic value in inhibiting diseases in which eotaxin1 and eosinophils play a major role, for example, severe asthma.