Abstract 6703: A fully synthetic EphA2/4-1BB tumor-targeted immune cell agonist (TICATM) induces tumor localized 4-1BB agonism
Authors: Battula Sailaja , Mudd Gemma , Upadhyaya Punit , Kristensson Julia , Kleyman Marianna , Repash Elizabeth , Kublin Jessica , Ma Jun , Haines Eric , Hurov Kristen , Chen Liuhong , Lahdenranta Johanna , Beswick Paul , McDonnell Kevin , Keen Nicholas 
Published: September 2020

Abstract
4-1BB (CD137) is a member of the TNFR superfamily involved in stimulation of several immune cell types, including T cells and NK cells. CD137 is well validated pre-clinically, as agonism with anti-CD137 antibodies is effective in vivo [1], however, clinical utility to date has been limited by dose dependent hepatotoxicity. Bicycles® are a new therapeutic modality - fully synthetic, constrained bicyclic peptides with high affinity and excellent target selectivity.
We hypothesized that Bicycle CD137 agonists that lack Fc domains and exhibit rapid renal elimination may induce CD137 mediated anti-tumor activity while avoiding liver toxicity. Initially, we identified and optimized CD137 specific Bicycle agonists which, when multimerized together, induced CD137 mediated anti-tumor activity [2]. We have built on this initial approach and developed second generation molecules to enable potent stimulation of immune cells exclusively at the tumor site. These tumor-targeted immune cell agonists (TICAsTM) comprise CD137 binding Bicycles coupled to tumor antigen binding Bicycles.
Erythropoietin-producing hepatocellular A2 receptor (EphA2) is a tumor target overexpressed in several human cancers and its overexpression correlates with poor clinical prognosis. Here, we present new preclinical data demonstrating the potent immunomodulatory activity of dual targeting EphA2/CD137 TICAs. EphA2/CD137 TICAs engage EphA2 and CD137 with high affinity resulting in picomolar potency in co-culture assays consisting of cancer cell lines endogenously expressing EphA2, and CD137 Jurkat NF-kB/luciferase reporter cells. Moreover, EphA2/CD137 TICAs potentiate cytokine secretion (e.g. IFNγ) in immune cell co-culture experiments and promote caspase activity in T cell mediated cell killing assays. In vivo, EphA2/CD137 TICA (BCY9173), when dosed at 15 mg/kg (BID) to PBMC-humanized mice bearing HT29 xenografts, increased CD8+ T cells in tumors but not in plasma, suggesting local tumor target specific stimulation of T cells without systemic CD137 agonism. Intermittent dosing with various regimens of BCY12491, an EphA2/CD137 TICA, demonstrated robust anti-tumor activity including complete responses (CR) in 10/12 animals in a syngeneic humanized CD137 MC38 mouse model. Importantly, CR mice are resistant to re-challenge with MC38 tumor cells demonstrating a memory response, a phenomenon which has been previously reported for CD137 agonists [1]. Our EphA2/CD137 TICAs have shown the potential to precisely and potently stimulate immune cells in tumors without systemic immune activation.
This provides a strong rationale to further develop first-in-class Bicycle TICAs to potentially treat EphA2 expressing cancers.
References
1. Melero I, Shuford WW, Newby SA, Aruffo A, Ledbetter JA, Hellström KE, Mittler RS, Chen L. Monoclonal antibodies against the 4-1BB T-cell activation molecule eradicate established tumors. Nat Med. 1997; 3(6): 682-5
2. K. Hurov, P. Upadhyaya, J. Kublin, M. Kleyman, X. Zhou, J. Kristensson, G. Mudd, K. Rietschoten, S. Watcham, R. Lani, W. F. An, T. Stephen, E. Haines, J. Lahdenranta, L. Chen, S. Battula, K. McDonnell, P. Park, and N. Keen. Activation of 4-1BB using multivalent and tumour targeted bicyclic peptides; Poster 2019 Annual AACR meeting, Cancer Research, DOI: 10.1158/1538-7445.AM2019-3257 Published July 2019
Citation Format: Sailaja Battula, Gemma Mudd, Punit Upadhyaya, Julia Kristensson, Marianna Kleyman, Elizabeth Repash, Jessica Kublin, Jun Ma, Eric Haines, Kristen Hurov, Liuhong Chen, Johanna Lahdenranta, Paul Beswick, Kevin McDonnell, Nicholas Keen. A fully synthetic EphA2/4-1BB tumor-targeted immune cell agonist (TICATM) induces tumor localized 4-1BB agonism [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6703.