Antibody engineering for increased potency, breadth and half-life

Sievers, Stuart A.; Scharf, Louise; West, Anthony P.; Bjorkman, Pamela J.

Techniques to improve IgG affinities [31 & ,32], broaden their specificity to related antigens [33] [34] [35] and improve their expression and solubility [32] include computational techniques [36] [37] [38] [39] and directed mutagenesis to introduce diversity coupled with selection techniques, for example phage, yeast, mRNA and ribosome display [32] . Early library-based engineering efforts to improve HIV-1 antibodies involved b12, one of the first HIV-1 bNAbs. The affinity of b12 was enhanced by nearly 400-fold by selecting for gp120 binding from libraries of phagedisplayed mutants in complementarity-determining regions (CDRs) [40] . These studies demonstrated that increasing affinity through in-vitro evolution could also increase breadth [41] . The engineering of the HIV-1 m9 antibody used a modified approach termed sequential antigen planning to improve both affinity and breadth: a single-chain variable fragment (scFv) library of a CD4-induced (CD4i) antibody was screened against sequentially changing antigens, ultimately identifying m9 [42] . Although antibodies recently isolated from donors are more promising therapeutically than earlier bNAbs [43,44 & ], librarybased methods may be important to improve the new generation of antibodies, as they can introduce beneficial changes that might not be anticipated from inspection of antibody-antigen complex structures. However, the large number of HIV-1 strains, including the diversity of the viral swarm within a single infected individual, makes it difficult to select for antibodies that maintain breadth across viral