Dr Morgan and Dr Fernandes suggest several first glycosylation features to consider modifying when designing biobetter MAbs. These include changes to the N-glycans in the Cg2 domain of the fragment crystallisable (Fc) region, as well as modifications to fragment antigen-binding (Fab) glycans if they exist in the therapeutic. In general, major changes can be achieved by switching cell lines, and smaller changes by modifying cell culture conditions. They note that the modification of one glycosylation feature will generally affect others, so when glycoengineering the glycosylation should be viewed as a whole, rather than the sum of independent components. (see also Design out Gal-α(1,3)-Gal for biobetter MAbs and Design out NeuGc, Fab glycosylation for biobetter MAbs)

Design out core Fc fucosylation

Antibody-dependent cellular cytotoxicity (ADCC) activity of therapeutic IgG1 type MAbs can be greatly increased by reducing the levels of fucosylation. The mechanism is improved binding to the Fcγ receptor IIIa (FcγRIIIa) of the low fucose MAb glycoforms. Engineered antibodies with low fucose are now being produced; their improved binding to FcgγIIIa allows them to evade the inhibitory effect on ADCC of plasma IgG (which is fucosylated and binds to FcgγIIIa with lower strength). The authors suggest you may design out core Fc fucosylation of MAbs relying on ADCC by switching to a cell line producing low-fucose complex N-glycans (which now include commercially available galactosyltransferase knockout mammalian cells). This should give you a biobetter with a better efficacy profile. As an alternative, you may consider a high-titre non-mammalian expression system (e.g. producing oligomannose glycans) that could give you a drug of which the manufacturing cost per therapeutic dose is lower than that of the original drug. However, they warn you should be aware of other effects (e.g. changes to pharmacokinetics).

Modify β-galactosylation levels

If your MAb relies on CDC (complement-dependent cytotoxicity) for its mode of action, Dr Morgan and Dr Fernandes write you should consider increasing the levels of terminal Gal-b(1,4) residues on the Fc glycans. The positive correlation between CDC activity and galactose has been found in the anti-CD20 antibody Rituximab, where C1q binding to the Fc region increases with the percentage of galactosylation, and similar effects have been found in other CDC-dependent therapeutic antibodies. According to them, levels of terminal b-galactosylation can be modified by switching mammalian cell lines and changing cell culture conditions, including dissolved oxygen.

Reference:

Claire Morgan and Daryl Fernandes. Designing Biobetter Monoclonal Antibody Therapeutics By Glycoengineering. International Pharmaceutical Industry (IPI) p. 38-44. Autumn 2009.