Abstract 2579: Combination with the novel tumor-targeted CEA-IL2v immunocytokine enhances the activity of ADCC-competent and glycoengineered antibodies in vitro and in vivo
Authors: Nicolini Valeria , Waldhauer Inja , Freimoser Anne , Colombetti Sara , Cavallo Federica , Bacac Marina , Gerdes Christian , Umana Pablo , Klein Christian 
Published: May 2015

Abstract
We recently described a novel monomeric tumor-targeted CEA-IL2v immunocytokine. CEA-IL2v comprises a single IL-2 variant (IL2v) with abolished CD25 binding that is fused to the C-terminus of a humanized CEA antibody with a heterodimeric Fc devoid of FcγR and C1q binding. CEA-IL2v recognizes a membrane-proximal epitope of CEA. Here we show that CEA-IL-2v is able to enhance the activity of ADCC competent antibodies and glycoengineered IgG1 antibodies in vitro and in vivo.
The combination of CEA-IL2v with ADCC-competent IgG1 antibodies was investigated in vitro in ADCC assays and in vivo in xenografts in hCD16a transgenic SCID mice that express hFcγRIIIα on NK cells and the homologous muFcγRIV on macrophages/monocytes. Antibodies tested include trastuzumab, cetuximab and the ADCC-enhanced glycoengineered EGFR antibody GA201. In the spontaneous genetically engineered BALB-neuT breast cancer mouse model a surrogate tumor stroma Tenascin C A2 (TNCA2)-targeted IL2v immunocytokine was used in combination with a ratHER2 antibody.
PBMCs stimulated by CEA-IL2v in co-cultures with tumor cells showed dose-dependent elimination of tumor cells and activation of NK cells. Addition of trastuzumab or cetuximab resulted in induction of activation markers and enhanced killing of tumor cells. As a single agent, CEA-IL2v showed minor tumor growth inhibition in orthotopic i.m.f.p. KPL4 BC and s.c. N87 GC xenografts. The combination of CEA-IL2v (1 mg/kg, q7d×3) with trastuzumab (10 mg/kg in KPL4 and 25 mg/kg in N87, q7d×3) resulted in superior inhibition of tumor growth compared to the respective single-agent treatments, combination therapy induced 6/9 complete tumor remissions in N87 and 3/5 in KPL4. In the i.v. A549 lung cancer and i.s. LS174T CRC xenografts, single-agent CEA-IL2v showed a moderate effect on median survival, whereas the combination of CEA-IL2v (1 mg/kg, q7d×3) with cetuximab (25 mg/kg, q7d×3) increased median/overall survival. Similarly, in the i.v. A549 NSCLC and i.s. LS174T CRC xenografts, the combination of CEA-IL2v (1 mg/kg for A549 and 2 mg/kg for LS174T, q7d×3) with GA201 (25 mg/kg, q7d×3) resulted in superior median survival compared to the respective single-agent treatments with long term survival of 10/10 animals in the A549 model and survival of 2/8 animals in the LS174T model. Finally in the spontaneous GEM BALB-neuT breast cancer model the combination of TNCA2-IL2v with a ratHER2 IgG1 antibody resulted in a strong and significant reduction of tumor formation in 6/7 animals as compared to the respective single agents.
Combining CEA-IL2v or TNCA2-IL2v with ADCC competent/enhanced IgG1 antibodies results in enhanced anti-tumor efficacy in xenografts and in a spontaneous immunocompetent genetically engineered BALB-neuT mouse model. These data support the clinical investigation of CEA-IL2v with ADCC competent/enhanced IgG1 antibodies.
Citation Format: Valeria Nicolini, Inja Waldhauer, Anne Freimoser, Sara Colombetti, Federica Cavallo, Marina Bacac, Christian Gerdes, Pablo Umana, Christian Klein. Combination with the novel tumor-targeted CEA-IL2v immunocytokine enhances the activity of ADCC-competent and glycoengineered antibodies in vitro and in vivo. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2579. doi:10.1158/1538-7445.AM2014-2579