Neil I. Goldstein

Immunogenicity and pharmacokinetic attributes of poly(ethylene glycol)-grafted immunoliposomes

Immunoliposomes composed of hydrogenated soy phosphatidylcholine, cholesterol, methoxypoly(ethylene glycol)-distearoyl phosphatidylethanolamine (mPEG-DSPE), and hydrazide-PEG-DSPE (mole ratio, 57:38:3.3:1.7) linked to periodate-oxidized chimerized mouse IgG (C225, anti-human epidermal growth factor receptor) were prepared by an optimized aggregation-free procedure. The antigen-binding activity of the immunoliposomes was well preserved. When injected intravenously into naive rats, the immunoliposomes (approximately 18 IgG per 100 nm liposome) exhibited long circulation times (MRT = 8.5 h, Cl = 0.2 ml/h). Subsequent injections of the immunoliposomes into the same animals resulted in rapid clearance (MRT < or = 0.7 h, Cl > or = 7 ml/h), which was accompanied by a significant increase in anti-C225 specific titers. Upon repeated injection or coinjection with the parent liposomes free C225 consistently exhibited prolonged circulation without any increase in C225-specific antisera, but was cleared quickly when administered into animals that had been pretreated with the immunoliposomes. Screening of the immunoliposome induced antisera against human polyclonal IgG and C225-derived Fab fragment revealed that the immune response was specifically triggered by the constant human region of C225. These results demonstrate that the preparations of PEG-grafted immunoliposomes are more immunogenic than the free IgG component, which is of profound importance to the antibody-mediated liposomal drug delivery effort.

High-level expression of a biologically active human interleukin-6 mutein

We have constructed two different muteins of interleukin-6 (IL-6) which were expressed in Escherichia coli. Both muteins lack the first 22 N-terminal amino acids of native IL-6 and lack one or the other of the two naturally occurring pairs of cysteines at either position 45 and 51 or position 74 and 84 of IL-6. We found that there was a dramatic increase in the level of IL-6 produced from each mutein clone, compared to the level produced by the wild-type IL-6 clone. We also observed that the yield of soluble and properly refolded mutein IL-6 was highest when the cysteines at position 74 and 84 were left intact. The mutein IL-6 with cysteines at position 74 and 84 was as active as wild-type IL-6 and a lower concentration of the mutein IL-6 was required to reach maximal activity, compared to wild-type IL-6. The mutein IL-6 with cysteines at position 45 and 51 had a much reduced biological activity.

New approaches for the development and application of monoclonal antibodies for the diagnosis and therapy of human cancer

Monoclonal antibodies (MAbs) represent potentially important reagents for both the diagnosis and therapy of human cancer. Innovative approaches are resulting in the improved production of MAbs and an enhanced ability to use these molecules therapeutically. Application of genetic engineering to MAb development is also resulting in the production of MAbs displaying enhanced target specificity. Of particular value for cancer therapy will be catalytic, bispecific, anti-idiotypic and human MAbs. By using agents that can augment the expression of tumor-associated antigens on cancer cells, a further increase in the utility of MAbs in cancer therapy will be forthcoming.

CCR 20th Anniversary Commentary: A Chimeric Antibody, C225, Inhibits EGFR Activation and Tumor Growth

Murine mAb 225 was effective against the EGFR tyrosine kinase and inhibited tumor growth in preclinical studies. A phase I trial showed safety, tumor localization, and satisfactory pharmacokinetics. Human:murine chimeric C225 retained biologic activity, which was essential for the conduct of subsequent combination therapy trials and eventual regulatory approval. Clin Cancer Res; 21(2); 227–9. ©2015 AACR. See related article by Goldstein et al., Clin Cancer Res 1995;1(11) November 1995;1311–8