title: Antibody-mediated neutralization of autocrine Gas6 inhibits the growth of pancreatic ductal adenocarcinoma tumors in vivo.
abstract: Gas6 and its receptors Axl, Mer and Tyro-3 (TAM) are highly expressed in human malignancy suggesting that signaling through this axis may be tumor-promoting. In pancreatic ductal adenocarcinoma (PDAC), Gas6 and the TAM receptor Axl are frequently co-expressed and their co-expression correlates with poor survival. A strategy was devised to generate fully human neutralizing antibodies against Gas6 using XenoMouse® technology. Hybridoma supernatants were selected based on their ability to inhibit Gas6 binding to the receptor Axl and block Gas6-induced Axl phosphorylation in human cells. Two purified antibodies isolated from the screened hybridomas, GMAB1 and GMAB2, displayed optimal cellular potency which was comparable to that of the soluble extracellular domain of the receptor Axl (Axl-Fc). In vivo characterization of GMAB1 was conducted using a pharmacodynamic assay that measured inhibition of Gas6-induced Akt activation in the mouse spleen. Treatment of mice with a single dose (100-1000 µg) of GMAB1 led to greater than 90% inhibition of Gas6-induced phosphorylated Akt (pAkt) for up to 72 hr. Based on the target coverage observed in the PD assay, the efficacy of GMAB1 was tested against human pancreatic adenocarcinoma xenografts. At doses of 50 µg and 150 µg, twice weekly, GMAB1 was able to inhibit 55% and 76% of tumor growth, respectively (p < 0.001 for both treatments vs. control Ig). When combined with gemcitabine, GMAB1 significantly inhibited tumor growth compared to either agent alone (p < 0.001). Together, the data suggest that Gas6 neutralization may be important as a potential strategy for the treatment of PDAC.
authors.affiliation: Oncology Research Therapeutic Area, Thousand Oaks, CA.
authors.forename: Gordon
authors.initials: G
authors.lastname: Moody
authors.affiliation: Oncology Research Therapeutic Area, Thousand Oaks, CA.
authors.forename: Brian
authors.initials: B
authors.lastname: Belmontes
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Masterman
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Chadwick
authors.initials: C
authors.lastname: King
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Chris
authors.initials: C
authors.lastname: Murawsky
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Trace
authors.initials: T
authors.lastname: Tsuruda
authors.affiliation: Therapeutic Discovery, Amgen Inc., Thousand Oaks, CA.
authors.forename: Shuying
authors.initials: S
authors.lastname: Liu
authors.affiliation: Oncology Research Therapeutic Area, Thousand Oaks, CA.
authors.forename: Robert
authors.initials: R
authors.lastname: Radinsky
authors.affiliation: Oncology Research Therapeutic Area, Thousand Oaks, CA.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Beltran
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology*; D057134:Antibodies, Neutralizing / Q000276:immunology / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects*; D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D000906:Antibodies; D057134:Antibodies, Neutralizing; D000970:Antineoplastic Agents; D036341:Intercellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D000094963:Axl Receptor Tyrosine Kinase; D000099255:Growth Arrest-Specific Protein 6
keywords: Axl; Gas6; Mer; PDAC; Tyro-3; Xenomouse®; pancreatic carcinoma