Engineering an antibody with picomolar affinity to DOTA chelates of multiple radionuclides for pretargeted radioimmunotherapy and imaging

摘要: Abstract Introduction In pretargeted radioimmunotherapy (PRIT), a bifunctional antibody is administered and allowed to pre-localize tumor cells. Subsequently, chelated radionuclide captured by cell-bound while unbound hapten clears rapidly from the body. We aim engineer high-affinity binders 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelates for use in PRIT applications. Methods mathematically modeled pharmacokinetics analyze retention as function of binding affinity. Motivated model predictions, we used directed evolution yeast surface display affinity mature 2D12.5 DOTA, reformatted single chain variable fragment (scFv). Results Modeling predicts that high antigen density saturating bsAb dose, hapten-binding 100 pM needed near-maximal retention. matured with an initial constant about 10 nM DOTA-yttrium chelates. Affinity maturation resulted 1000-fold improvement biotinylated DOTA-yttrium, yielding 8.2±1.9 picomolar binder. The scFv binds DOTA complexes lutetium gadolinium similar indium low nanomolar When engineered into bispecific construct targeting carcinoembryonic antigen, results significantly higher 111 In-DOTA compared wild-type xenograft mouse model. Conclusions have versatile, high-affinity, DOTA-chelate-binding scFv. anticipate it will prove useful developing imaging therapy protocols exploit potential variety radiometals.