Received for publication July 26, 2006.
Revised September 4, 2006.
Accepted for publication September 12, 2006.

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

Abstract

The CC chemokine, eotaxin1 (CCL11) is an important regulator of eosinophil function. A marked accumulation of eosinophils in tissues has been correlated with the upregulation of eotaxin1 expression in several diseases. The potential therapeutic value of neutralising the effects of eotaxin1 in inflammatory conditions (including asthma) is under investigation. A human single chain fragment variable (scFv) antibody that neutralises human eotaxin1 (CAT-212) was produced using antibody phage display and converted to whole antibody IgG4 format (CAT-213). A novel approach to lead optimisation in which the length of the variable heavy chain complementarity determining region 3 (V_HCDR3) was reduced by one amino acid resulted in an increase in potency of over 1000-fold compared to the parent anti-eotaxin1 antibody. The optimised antibody binds eotaxin1 with high affinity (80.4 pM) and specificity. CAT-213 and CAT-212 do not bind or neutralise a range of other human proteins including human MCP-1, a structurally similar chemokine. CAT-213 neutralises the ability of eotaxin1 to cause an increase in intracellular calcium signalling (with an IC₅₀ value of 2.86 nM), migration of CCR3-expressing L1.2 cells (with an IC₅₀ value of 0.48 nM) and inhibits eotaxin1 evoked shape change of human eosinophils in vitro (with an IC₅₀ of 0.71 nM). Local administration of CAT-213 to mice (1 - 100µg kg^-1) attenuates dermal eosinophilia induced by human eotaxin1, achieving greater than 90% inhibition of eosinophil influx. CAT-213 may therefore be of therapeutic value in inhibiting diseases where eotaxin1 and eosinophils play a major role, for example in severe asthma.

Key words: antibody, asthma, eotaxin, human, optimisation, phage