Details

Autor(en) / Beteiligte

• Kuenkele, Klaus-Peter
• Hofmann, Marco H.
• Scheiblich, Stefan
• Wartha, Katharina
• Klein, Christian

Titel

Abstract LB-397: Functional characterization of IGF-1R antibodies and possible implications for clinical safety and efficacy

Ist Teil von

• Cancer research (Chicago, Ill.), 2011-04, Vol.71 (8_Supplement), p.LB-397-LB-397

Erscheinungsjahr

2011

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract Background This is the first study performing a head to head comparison of monoclonal IGF-1R antibodies (mAb) based on published sequences for therapeutic mAbs from Pfizer (CP751,871, IgG2 kappa), Amgen (AMG479, IgG1 lambda), Merck (h7C10, cloned to R1507 backbone), Imclone (IMC-A12, IgG1 lambda) and Roche (R1507, IgG1). Methods In this study, sequence information for IGF-1R mAbs was extracted from patents and used to clone and transiently express IgGs (*=re-synthesized) in HEK293F cells. In vitro assays for ligand binding, IGF-1R auto-phosphorylation, IGF-1R downregulation, IR co-downregulation, and affinity analyses (Biacore) were used. In vivo comparison was done in BxPC3 xenograft mouse model. Results All antibodies inhibit IGF-1 binding and signaling at low nanomolar levels. While IMC-A12* and R1507 also prevent IGF-2 binding to IGF-1R and subsequent receptor activation, CP751,871* and h7C10* do not inhibit IGF-2 binding and have only limited impact (55%/30% inhibition) on IGF-2 signaling. Analysis of IGF-1R phosphorylation in 0.5 % FCS medium revealed that all antibodies except R1507 exert agonistic activity. Interestingly, Fab fragments of agonistic mAbs became antagonistic, indicating that bivalent binding is necessary for agonistic effects. All mAb (200nM, 24h treatment of MCF-7 cells) with the exception of AMG479* efficiently downregulated 78–82% the IGF-1R. Analysis of the same cell lysates revealed however striking differences in IR co-downregulation, a mechanism discussed as possible cause of clinical hyperglycemia. R1507 had the least side effects on Insulin co-downregulation (9%) compared to h7C10* (15%), CP751,871* (23%) and IMC-A12* (46%). Differences were also seen in the binding kinetics. Both AMG479* and R1507 showed faster koff rates resulting in shorter retention times at the receptor. Since kon/koff rates are discussed to influence tumor penetration (1), we compared downregulation of IGF-1R by R1507 and CP751,871* in xenograft tumors. Although both mAbs downregulate IGF-1R in vitro to the same extent, R1507 was significantly more effective in the in-vivo setting. Conclusion The head to head comparison of IGF-1R mAbs revealed differences in regard to binding properties, tumor penetration, IR codownregulation, and inhibition of signaling via the ligand IGF-2. Reference List 1. Adams, G. P., Schier, R., McCall, A. M., Simmons, H. H., Horak, E. M., Alpaugh, R. K., Marks, J. D., and Weiner, L. M. (2001) Cancer Res. 61, 4750–4755 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-397. doi:10.1158/1538-7445.AM2011-LB-397