Abstract 871: Nanoliposomal targeting of ephrin receptor A2 (EphA2): Preclinical in vitro and in vivo rationale
Authors: Kamoun Walid S. , Luus Lia , Pien Christine , Kornaga Tad , Oyama Shinji , Huang Zhaohua Richard , Tipparaju Suresh , Kirpotin Dmitri B. , Marks James D. , Koshkaryev Alexander , Geddie Melissa , Xu Lihui , Lugovosky Alexey , Drummond Daryl C. 
Published: July 2016

Abstract
Ephrins receptors are cell to cell adhesion molecules that mediate signaling and are implicated in neuronal repulsion, cell migration and angiogenesis. Ephrin receptor A2 (EphA2) is part of the ephrin family and was shown to be overexpressed in several solid tumors including ovarian, gastric and lung cancer and is associated with poor prognosis. MM-310 is a novel EphA2 targeted docetaxel nanoliposome. Similar to other nanoparticles, MM-310 leverages organ specificity through enhanced permeability and retention, but can also leverage cellular specificity through its EphA2 targeting arm.
Binding of targeted liposomes to cells in vitro was assessed using flow cytometry in a large panel cell lines. 3D spheroids were used to assess targeting as well as liposome penetration. In order to test the effect of targeting on liposome microdistribution in vivo, primary and metastatic tumor bearing animals were injected with a mixture of EphA2-targeted liposome (EphA2-Ls) and non-targeted liposome (NT-Ls) labeled with two different lipophilic fluorescent dyes. Tissues were assessed using fluorescent microscopy. In order to evaluate the contribution of EphA2-targeting to efficacy, four gastric xenograft models were treated with either MM-310 or a non-targeted version of the drug NT-310, and compared to free docetaxel.
In cell suspension models, we observed a high level of specificity for EphA2-Ls, with more than one hundred-fold increase in liposome cell association. 3D spheroid assays showed that EphA2-Ls binds and penetrates EphA2+ spheroids, while non-targeted liposomes show minimal penetration. Tissue microdistribution analysis in triple negative breast and esophageal tumor models following injection of the EphA2-Ls/NT-Ls mixtures showed a target mediated shift in the microdistribution of liposomes. EphA2-Ls penetrated deeper within the lesions while the NT-Ls deposited at high levels in areas close to the microvasculature. The target mediated shift in microdistribution was also observed in lung metastasis model, with a pattern of distribution that potentially matches disseminated tumor cells. In the same animals, targeting did not affect microdistribution in normal organs such as liver, spleen and skin. Four models of gastric and esophageal cancers were used to test the potential link between cell targeting and tumor growth control. While NT-310 and MM-310 were both able to control tumor growth leading to regression in most models, in three out of four models there was a statistically significant difference between MM-310 and NT-310 at 25 mpk. Biomarker analysis is underway to evaluate the key parameters necessary to mediate targeting.
In conclusion, the data suggests clear evidence of targeting in 2D cell suspension, 3D spheroids, and in primary as well as metastatic tumor models in vivo. In vivo efficacy data showed evidence of the contribution of EphA2 targeting to tumor growth control and regression in several gastric cancer models.
Citation Format: Walid S. Kamoun, Lia Luus, Christine Pien, Tad Kornaga, Shinji Oyama, Zhaohua Richard Huang, Suresh Tipparaju, Dmitri B. Kirpotin, James D. Marks, Alexander Koshkaryev, Melissa Geddie, Lihui Xu, Alexey Lugovosky, Daryl C. Drummond. Nanoliposomal targeting of ephrin receptor A2 (EphA2): Preclinical in vitro and in vivo rationale. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 871.