Abstract 239: A novel multimeric protein scaffold stimulates apoptotic signaling through TRAILR2

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL TRAILR2 (DR5, TNFRSF10B) is a member of the TNF-receptor superfamily that mediates programmed cell death following stimulation with its ligand. Binding of homotrimeric ligand TRAIL to TRAILR2 induces oligomerization of the receptors and triggers the apoptotic pathway through induction of caspases. Although TRAILR2 is found to be expressed in a number of normal cell types it is routinely found at high levels in many cancer types. Since TRAIL has been shown to preferentially induce apoptosis in cancer cells versus normal cells, several TRAIL receptor agonists including monoclonal antibodies as well as the ligand itself, are currently in clinical development. Here, we describe a novel protein scaffold (Tn3) based on a fibronectin type-III domain from the protein Tenascin that was engineered to specifically agonize TRAILR2. Connecting TRAILR2-binding Tn3 domains together significantly improved the in vitro potency of the molecule in several cancer cell models. For example, a hexameric TRAILR2-binding Tn3 construct has an EC50 of 0.5 pM in a 72 hour cell viability assay with Colo-205 cells. This is approximately 2 logs better than TRAIL. Furthermore, a subset of TRAIL-resistant cancer cell lines derived from multiple tissues of origin is sensitive to the multimeric Tn3. The improved potency over TRAIL was demonstrated in colorectal cancer xenograft models. In addition, tumor regression was also observed at doses as low as 0.3 mg/kg. These results suggest that a multimeric Tn3 protein scaffold targeting TRAILR2 has more potent anti-tumor activity in vitro and in vivo compared than the natural ligand. 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 239. doi:1538-7445.AM2012-239