AMG 479, a fully human anti-IGF-1R monoclonal antibody, Inhibits IGF-1 induced phospho-Akt and enhances the antineoplastic activity of cyclophosphamide in vivo

4001 AMG 479 is a fully human monoclonal antibody raised against the type I IGF-1 receptor (IGF-1R). AMG 479 exerts its anti-tumor effects by inhibiting IGF-1R signaling through ligand blocking and receptor internalization and degradation. Currently, a single agent phase II clinical trial is underway to test the activity of AMG 479 against Ewing’s sarcoma. In the present study, we tested the ability of AMG 479 to inhibit IGF-1 driven PI3K/Akt pathway activation in sarcoma cell lines as well as its ability to enhance responsiveness to cyclophosphamide.AMG 479 was able to inhibit more than 80% of IGF-1 induced phospho-Akt (pAkt) and phospho-p70S6K (pp70S6K) in the sarcoma cell lines SK-ES-1, SJSA-1 and A673. To test whether this inhibitory effect can also be achieved in vivo, we dosed xenograft bearing mice (SK-ES-1, SJSA-1 or A673) with 1 mg of AMG 479 or hIgG1 6 hrs prior to challenge with an intraperitoneal injection of IGF-1 (15 μg). Tumor lysates generated from xenograft samples demonstrated that AMG 479 effectively inhibited IGF-1 induced Akt and p70S6K phosphorylation. Interestingly, in SJSA-1 xenografts, AMG 479 was also able to inhibit all basal pAkt activity. Treatment of SK-ES-1 and SJSA-1 xenografts with AMG 479 (300 μg/dose, 2x/week) resulted in highly significant (p 70% vs. hIgG1). In contrast, AMG 479 failed to inhibit the growth of A673 xenografts when used as single agent. In this resistant model, the addition of the DNA alkylating agent cyclophosphamide (25 mg/kg, 3x/week) to AMG 479 therapy resulted in significant (p=0.0020 vs. AMG 479, p=0.0002 vs. cyclophosphamide) tumor growth inhibition compared to either therapy alone, suggesting that these two agents can be combined clinically for the treatment of sarcoma. Together, the data suggest that AMG 479 has therapeutic potential in sarcoma patients both as monotherapy and in combination with approved chemotherapeutic agents.