Combination of Two Insulin-Like Growth Factor-I Receptor Inhibitory Antibodies Targeting Distinct Epitopes Leads to an Enhanced Antitumor Response

Abstract

The insulin-like growth factor-I receptor (IGF-IR) is a cell surface receptor tyrosine kinase that mediates cell survival signaling and supports tumor progression in multiple tumor types. We identified a spectrum of inhibitory IGF-IR antibodies with diverse binding epitopes and ligand-blocking properties. By binding distinct inhibitory epitopes, two of these antibodies, BIIB4 and BIIB5, block both IGF-I and IGF-II binding to IGF-IR using competitive and allosteric mechanisms, respectively. Here, we explored the inhibitory effects of combining BIIB4 and BIIB5. In biochemical assays, the combination of BIIB4 and BIIB5 improved both the potency and extent of IGF-I and IGF-II blockade compared with either antibody alone. In tumor cells, the combination of BIIB4 and BIIB5 accelerated IGF-IR downregulation and more efficiently inhibited IGF-IR activation as well as downstream signaling, particularly AKT phosphorylation. In several carcinoma cell lines, the antibody combination more effectively inhibited ligand-driven cell growth than either BIIB4 or BIIB5 alone. Notably, the enhanced tumor growth-inhibitory activity of the BIIB4 and BIIB5 combination was much more pronounced at high ligand concentrations, where the individual antibodies exhibited substantially reduced activity. Compared with single antibodies, the BIIB4 and BIIB5 combination also significantly further enhanced the antitumor activity of the epidermal growth factor receptor inhibitor erlotinib and the mTOR inhibitor rapamycin. Moreover, in osteosarcoma and hepatocellular carcinoma xenograft models, the BIIB4 and BIIB5 combination significantly reduced tumor growth to a greater degree than each single antibody. Taken together, our results suggest that targeting multiple distinct inhibitory epitopes on IGF-IR may be a more effective strategy of affecting the IGF-IR pathway in cancer. Mol Cancer Ther; 9(9); 2593-604. ©2010 AACR.

Stable IgG-like Bispecific Antibodies Directed toward the Type I Insulin-like Growth Factor Receptor Demonstrate Enhanced Ligand Blockade and Anti-tumor Activity

“…These results combined with the equilibrium SPR results indicate that only the BIIB4-5scFv BsAb has all its binding arms completely unimpeded for binding hIGF-1R. Enhanced Ligand Blockade via Engagement of Two Inhibitory Epitopes-It was shown previously that combining the inhibitory antibody properties of both BIIB4 and BIIB5 leads to significantly enhanced inhibition of IGF-1R signaling and tumor cell growth, primarily due to enhanced ligand blockade (9). The goal of generating a BsAb targeting both inhibitory epitopes was to capture this activity within a single therapeutic candidate.…”

“…Signaling Analyses-Measurement of the relative levels of both IGF-1R and Akt phosphorylation in the absence and presence of each mAb or BsAb was performed as described previously for the BIIB4 and BIIB5 combination (9). Briefly, cells were grown in RPMI 1640 medium containing 10% FBS overnight and then serum-starved for 24 h. The cells were treated with 0.1, 1, 10, or 100 nM of control antibody C2B8, BIIB5, BIIB4, BIIB4-5scFv, or a combination of BIIB4 and BIIB5 each at the above indicated concentrations for 1 h before being stimulated with 100 ng/ml of IGF-1 (R & D Systems) for 20 min.…”

“…Recently, we have shown that targeting multiple inhibitory epitopes of IGF-1R can result in enhanced ligand blockade, which concomitantly leads to decreased IGF-1R signaling and cell proliferation compared with what could be achieved with single mAbs (9). Positive results of pairing the inhibitory mechanisms of distinct antibodies against single targets for improved activity have been demonstrated in both oncology (10 -12) and infectious diseases (13,14).…”

“…Positive results of pairing the inhibitory mechanisms of distinct antibodies against single targets for improved activity have been demonstrated in both oncology (10 -12) and infectious diseases (13,14). We tested several antibody combinations against IGF-1R and found that the combination of a purely competitive inhibitor and a purely allosteric inhibitor (8) provided the most compelling activity (9). We hypothesized that converting this antibody combination into a single bispecific antibody (BsAb) might increase the effective concentration of each antigen binding arm upon initial binding to IGF-1R and lead to increased potency.…”

Interplay between microRNA-17-5p, insulin-like growth factor-II through binding protein-3 in hepatocellular carcinoma

“…IGF-1R was reported to be upregulated in 59% of HCC tissues in which it was associated with poor prognosis and tumors exceeding the Milan criteria [10] . The tumorigenic effect of IGF-1R was reversed through its efficient blockage by combination of two IGF-1R antibodies which dramatically reduced liver tumor growth [11] . On the other hand, IGFBP-3 expression was found to be inversely correlated to HCC metastasis and proliferation [12,13] .…”