Production and characterization of 22 monoclonal antibodies directed against S 20499, a new potent 5-HT1A chiral agonist: Influence of the hapten structure on specificity and stereorecognition

Purpose. An immunoconjugate model was proposed to produce stereoselective m onoclonal antibodies (MAbs) for the quantitation of a 5-HT1A agonist, S 204 99. MAbs produced were characterized in terms of stereoselectivity and spec ificity towards the opposite enantiomer and structural analogs. Methods. The immunogen was formed following the effective addition of a but anoic acid spacer arm between the parent S 20499 structure and bovine serum albumin (BSA). After fusion (modified Kohler and Milstein's procedure), sp ecificity of MAbs was obtained using the Abraham's criteria. Experimental a nd calculated partition coefficients were determined. Results. Twenty-two hybridoma cell lines were established secreting MAbs (a pparent association constants ranging from 1.1 x 10(8) to 2.8 x 10(9) M-1). Several MAbs showed cross-reactivity levels of less than 5% with S 20500 ( optical antipode), which could anew a stereospecific assay to be set up. Bo th chroman and azaspiro moieties were part of the epitopic site. Dealkylati on and hydroxylation(s) led to various crossreactivity levels. Four antibod y families were described in terms of specificity. Conclusions. This study highlighted the influence of the immunoconjugate co nstruction (coupling site and type of spacer arm) in the immuno-stereospeci ficity of Abs. The results obtained for two monohydroxylated metabolites su ggest that the lipophilicity behavior could be a valuable tool for predicti ng Ab-crossreactivity.