N-Glycans at Asn(297) in the Fc domain of IgG molecules are required for Fc receptor-mediated effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). In this study we have specifically remodeled the Fc N-glycans of intact recombinant IgG(1) therapeutic monoclonal antibody (Mab) products, Rituxan and Herceptin, with a soluble recombinant rat beta-1,4-N-acetylglucosaminyltransferase III (rGnTIII) produced by baculovirus-infected insect cells. N-Glycan remodeling in vitro permitted a controlled and selective transfer of a bisecting beta1,4-linked GlcNAc to the core beta-linked mannose of degalactosylated Mab N-glycans to yield Mabs varying in bisecting GlcNAc content from 31% to 85%. This was confirmed by analysis of N-glycans by both normal phase HPLC and MALDI-MS, the latter yielding the expected mass increase of 203.2 Da with no other oligosaccharide modifications evident. ADCC of remodeled Rituxan and Herceptin Mabs was determined using peripheral blood mononuclear cells as effectors and either CD20(+) (SKW6.4 and SU-DHL-4) or Her2(+) (SKBR-3) target cells, respectively. A conserved 10-fold increase in ADCC was observed for both remodeled therapeutic Mabs with high (>80%) bisecting GlcNAc content. In contrast, although the presence of a bisecting GlcNAc had minimal effect on CDC, degalactosylation of Rituxan reduced CDC by approximately half, relative to unmodified (variably galactosylated) control Mab. In summary, our data suggests that in vitro remodeling of therapeutic Mab Fc N-glycans may be utilized to control the therapeutic efficacy of Mabs in vivo and to offer a more "humanized" glycoform profile for recombinant Mab products.

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Cell permeable carrier peptides are currently of interest for their potential to improve the delivery of bioactive molecules into cells and to specific cellular compartments. We have investigated the activity of a derivative of the antiandrogen drug, bicalutamide, attached to the cell-permeable carrier peptide penetratin(R). We have used both disulfide (labile) and thioether (nonlabile) linkages to attach the bicalutamide derivative to the peptide in order to assess whether one type of chemistry has advantages over the other. In addition we have added a nuclear localization sequence (NLS) to the carrier peptide to investigate whether localization of the drug to the nucleus of the cell affects the activity of the drug. Biotin-labeled peptides were used to demonstrate that the carrier peptide is rapidly accumulated inside cultured cells, and that the incorporation of an NLS in the sequence results in its nuclear targeting. The bicalutamide derivative linked to carrier peptides via a disulfide-linkage exerted no greater antiproliferative effect in LNCaP cells, than the bicalutamide derivative alone. The bicalutamide derivative linked to the carrier peptide by a non-labile thioether linkage showed a similar activity profile. When the construct includes a nuclear targeting sequence, however, a markedly increased antiproliferative effect was observed. This study has thus shown that the activity of bicalutamide may be enhanced by the nonlabile attachment of a cell-permeable and nuclear-targeted peptide, which has implications for the development of novel antiandrogens for the treatment of prostate cancer.