Project: Enhanced antibody directed enzyme prodrug therapy (ADEPT) for colorectal cancers

This project is concerned with enhancing “Antibody Directed Enzyme Prodrug Therapy” (ADEPT) for cancer to achieve greater efficacy with improved components and initially directed at colorectal (CRC) cancers._x000D__x000D_There reCOs a huge and growing need for improved cancer therapies. For example, CRC is the second most common cause of cancer death, causing 655,000 deaths worldwide per year, including 16,000 in the UK (50,000 in the US). It is the third most common cancer with incidences in 2005 of 36,766 in the UK (130,000 cases in the US). _x000D__x000D_Antibodies have shown promise for several decades, but major breakthroughs have not yet been made, so new approaches are urgently needed._x000D__x000D_This project is to develop a significantly enhanced form of ADEPT. Systemic cancer therapy is limited by a lack of tumour selectivity and by drug resistance; ADEPT was designed to overcome both problems. An antibody (Ab) directed against CEACAM5 is linked to an enzyme, carboxypeptidase G2 (CPG2), which converts a harmless prodrug into a powerful cytotoxic agent. When administered systemically, the antibody enzyme construct (AEC) accumulates in the tumour. Selectivity is achieved by the specificity of the antibody and by delaying prodrug administration until there is a large differential between tumour and normal tissue enzyme levels (2 step ADEPT). But, originally, selectivity was strongly enhanced by a clearing agent (3 step ADEPT) to remove unbound AEC via the liver, prior to prodrug administration. The prodrug is then converted to an active cytotoxic drug by the enzyme reCOing within the tumour. In initial animal models, full 3 step ADEPT had specific antitumour activity but, since then, the clearance agent (CA) was omitted from key ADEPT human clinical trials. See Appendix 3 for summary of previous ADEPT._x000D__x000D_A project based on ADEPT technology is particularly attractive, as a therapy with novel components, fully harmonized and optimized could provide a step-change in effectiveness._x000D__x000D_The project strategy is to develop novel CAs to deplete systemic AEC CPG2 activity, using peptides that bind the active site. Arrays of peptides will be synthesised, using an empirical approach, to identify sets of peptides that bind the active site. Binding properties of these peptides will be optimised by full empirical positional scanning, resulting in new peptides with optimal binding properties. Repeating such rounds of improvement, will achieve peptides with required affinity and specificity. Lead peptides resulting from the above optimisation rounds will be modified to generate a series of molecules with optimised patterns of pendant galactose molecules. Binding to AEC will be confirmed, and hepatic clearance efficacy will be predicted by cytometrically determining the ability of the CA/AEC complex to bind and be processed by cell lines expressing asialo-glycoprotein receptor. Prior to the phase I trials, the clearing agent is to be assessed in animal biodistribution and clearance studies to confirm efficacy. Manufacturing procedures and formulations are also to be optimised. The inclusion of a novel clearing agent (CA) within the therapy will tightly localise cytotoxin generation at the tumour site by removing unbound AEC from the circulation. _x000D__x000D_In parallel, an existing AEC (Ab against CEACAM5/CPG2 fusion; A5CP, Francis et al, BJ Cancer, 2002, 87: 600) that has been extensively characterised and proven in clinical settings, will be engineered to reduce/modify its glycosylation and expressed in various expression systems to further modify glycosylation patterns. This will reduce hepatic clearance and allow the AEC to reCO in circulation long enough to efficiently penetrate the tumour. The AEC will be expressed in an appropriate expression system in preparation for animal models and phase I clinical trials._x000D__x000D_An additional Mologic project, concerned with the development of a prodrug with optimum half life and resultant cytotoxicity, is set up to feed into this Enhanced ADEPT project at an appropriate stage (see Appendix 2)._x000D__x000D_All components of the Enhanced ADEPT project are to be assessed in in vitro cytotoxicity studies, animal distribution and clearance studies and animal immunogenicity models where appropriate. The last stage of the project is to conduct pre-clinical trials (xenograft-bearing mice models) of an integrated product with optimised conjugate, clearing agent, pro-drug and procedure. See Appendix 2 for a summary of the project plan and timescales._x000D__x000D_The end result is intended to be a step-change in cancer therapy, with therapeutic agents and procedures that produce a very high therapeutic index, with minimal side effects and unprecedented outcomes._x000D__x000D_The consortium combines a UK antibody-based SME (Mologic Ltd), and a Dutch SME (Pepscan bv). These Ps bring all the interrelated skills needed for the entire project._x000D__x000D_NB. See Appendix 1 for abbreviations used in this application.

Acronym	Enhanced ADEPT (Reference Number: 4806)
Duration	06/04/2009 - 29/07/2011
Project Topic	This project aims to significantly enhance the efficacy of ADEPT to treat colorectal and other CEA expressing cancers using a three step treatment approach, and substantial further benefits to the existing technology based on innovations from within Mologic and Pepscan
Project Results (after finalisation)	The CO Pepscan result of the project was the development of a successful clearing agent as part of the ADEPT concept. This was achieved through the development of a modified pepscan assay that allowed successful selection of peptide clearing agents. Pepscan designed and synthesized multiple large peptide arrays of 10000's of structurally constrained synthetic peptides containing very specific non-natural building blocks. The lead clearing agents were selected through screening of these peptide arrays with the enzyme CPG2. The other components of the ADEPT concept including the Prodrug were developed by Mologic Ltd. The relevant know-how was tranferred to Mologic Ltd. and its spin-out company Gallient Biomedical which will take the project further.
Network	Eurostars
Call	Eurostars Cut-Off 2

Project partner

Number	Name	Role	Country
2	Mologic Ltd	Coordinator	United Kingdom
2	Pepscan Therapeutics BV	Partner	Netherlands