Effect Of Mm-141 On Gemcitabine And Nab-Paclitaxel Potentiation In Preclinical Models Of Pancreatic Cancer Through Induction Of Igf-1r And Erbb3 Degradation

289 Background: Gemcitabine, the first-line treatment for pancreatic cancer, has been improved by addition of nab-paclitaxel. However, patient response to this regimen is limited. Oncogenic insulin-like growth factor 1 (IGF-1) and heregulin (HRG) signaling are associated with increased cancer risk and decreased response to anti-metabolites and taxanes. Therefore, we explored MM-141, a novel bispecific antibody that blocks ErbB3 and IGF-1 receptor (IGF-1R) signaling, in combination with nab-paclitaxel and gemcitabine in preclinical models of pancreatic cancer. Methods: Combinations with MM-141, gemcitabine, and nab-paclitaxel were investigated in pancreatic cancer cell lines, in vitro and in vivo. The effects of MM-141, gemcitabine, and nab-paclitaxel on tumor growth and signaling were measured by 3D spheroid growth, ELISA, Western, and mouse xenograft experiments. Results: In vitro studies show that IGF-1 and HRG are potent activators of AKT signaling, leading to increased pancreatic tumor cell proliferation and decreased sensitivity to gemcitabine and nab-paclitaxel. MM-141 inhibits ligand-induced AKT activation, induces IGF-1R and ErbB3 degradation better than a mixture of IGF-1R and ErbB3 antibodies, and sensitizes cells to gemcitabine and nab-paclitaxel, in vitro. In vivo, MM-141 combines favorably with a nab-paclitaxel/gemcitabine regimen, leading to curative outcomes in a subset of treated mice. Conclusions: ErbB3 and IGF-1R co-inhibition is required to inhibit AKT signaling in pancreatic adenocarcinoma cell lines. These receptors are associated with chemoresistance to gemcitabine and nab-paclitaxel, which is abrogated by co-administration with MM-141. MM-141-induced degradation of oncogenic receptor complexes is likely essential to reverse chemoresistance and enhance effects of the nab-paclitaxel/gemcitabine regimen. These data, taken together with wide-spread expression of IGF-1R and ErbB3 in Stage IV pancreatic adenocarcinoma tissue, support clinical exploration of a MM-141/nab-paclitaxel/gemcitabine regimen in frontline metastatic pancreatic cancer. Preparations for a randomized Phase 2 study are underway.