Abstract 2724: Activity of the specific anti-ADAM17 inhibitory IgG antibody (Ab), D1(A12) in an ovarian cancer model in vivo

Abstract

Abstract ADAM17 (TNF-α converting enzyme, TACE) is a membrane-bound metalloproteinase responsible for ectodomain shedding of TNF-α, EGFR ligands and other pathologically significant proteins. ADAM17 overexpression is reported in many cancers, with roles in cancer cell proliferation, migration and drug resistance. Small molecule inhibitors of ADAM17 lack specificity, so we developed a specific human ADAM17 inhibitory IgG Ab, D1(A12), which inhibits the proteolysis of ADAM17 substrates (TNF-α, amphiregulin, etc.,) in cancer cells in vitro (C.J. Tape, et al., Proc Natl Acad Sci USA 108: 5578-83, 2011). We have now assessed the suitability of the D1(A12) Ab for therapeutic use, by investigating its pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumour efficacy in mice. The IGROV1-Luc xenograft model of intraperitoneal (i.p.) disseminated ovarian carcinoma in nude mice was used, as IGROV1-Luc cells secrete TNF-α and other ADAM17 products and knockdown of TNF-α expression inhibits tumour growth (H. Kulbe, et al., Cancer Res., 67: 585- 592, 2007). We investigated the PK of D1(A12) Ab using a single 10 mg/kg dose i.p., first in non-tumour-bearing (NTB) mice and then in mice bearing IGROV1-Luc tumours, measuring the concentration of D1(A12) IgG in plasma and ascitic fluid by ELISA. In NTB mice, plasma Cmax was 512 nM, half life 8.6 days. The concentrations in tumour-bearing mice were expected to be lower due to a larger volume of distribution due to the ascitic fluid, and in tumour-bearing mice the Cmax was 425 nM in plasma and 391 nM in ascitic fluid. The PK data suggest that weekly dosing with 10 mg/kg D1(A12) maintains therapeutically active concentrations of the IgG, so this regimen was used for an efficacy study comparing D1(A12) with vehicle. D1(A12) showed clear PD effects: Ascitic fluid concentrations of 3 ADAM17 products were reduced when compared to vehicle: AREG (55 +/− 19 vs 302 +/− 37 pg/ml, p < 0.001), soluble hTNFR1α (479 +/− 100 vs 2108 +/− 204 pg/ml, p < 0.001) and TGF-β (0.35 +/− 0.67 vs 5.2 +/− 2.2 pg/ml, p = 0.002), indicative of inhibition of ADAM17 activity in vivo. However, D1(A12) did not significantly reduce the concentration of TNF-α in ascitic fluid (109 +/− 21 vs 134 +/−32 pg/ml, p = 0.06), suggesting that in this system ADAM17 is not the only metalloproteinase with TACE activity. Tumour burden was quantified using bioluminescence generated from the luciferase expressing cells, measured using an IVIS xenogen 200 imager. There was decreased tumour growth in the D1(A12)-treated group (compared to vehicle), although this did not reach statistical significance (p=0.09). In conclusion we have shown that the anti-ADAM17 antibody has PK properties suitable for therapeutic studies and that it can inhibit shedding of ADAM17-dependent growth factors in vivo. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2724. doi:1538-7445.AM2012-2724