Monoclonal antibodies (mAbs) are one of the fastest growing therapeutics in the drug sector. For many antibodies, the structure and extent of the N-glycans on the Fc region of the H-chain plays a significant role in their therapeutic function. A glyco-optimized anti-CD20 antibody (rituximab) was expressed in the clonal aquatic plant Lemna. The optimized glycosylation was accomplished by co-expressing an interfering RNA (RNAi) construct targeting the endogenous alpha-1,3-fucoslytransferase (FucT) and beta-1,2-xylosyltransferase (XylT) genes (Cox et al., 2006). The resulting glyco-optimized rituximab contained a single major G0 N-glycan without any detectable xylose or fucose. In cell-based functional assays, the glyco-optimized rituximab showed similar CD20-binding affinity and apoptotic effects as Rituxan® produced in mammalian cells but with significantly enhanced (up to 100-fold) antibody-dependent cellular cytotoxicity (ADCC). Using FACS based methods, comparable CD20-binding was demonstrated in the B-cell lines Raji, Daudi and Wil2S. Apoptotic measurements used Raji and Daudi cells. In the treatment of non-Hodgkin’s B-cell lymphoma (NHL), the patient response rate for Rituxan is only 50–60% and is significantly correlated with a FcgRIIIa receptor polymorphism (Cartron et al., 2002). However, the glyco-optimized rituximab showed enhanced ADCC with effector cells from all FcgRIIIa-158 genotypes. ADCC activity was determined by FACS-based methods using Raji as the target cells. PBMC genotyping was accomplished by PCR analysis (Koene et al., 1997). Up to a ten-fold decrease in complement dependent cytotoxicity (CDC) was also observed using Raji cells. This functional profile may offer the potential for an optimized anti-CD20 antibody therapeutic with improved efficacy and potency while simultaneously decreasing the side effects associated with CDC activity (Clark and Ledbetter, 2005).
Disclosure:Employment: Authors from institution 1) are employed at Biolex Therapeutics. Ownership Interests: Authors from institution 1) own company stock. Research Funding: Author from insitute 2) received research funding from Biolex.