Abstract 4294: GE152: In vivo detection of tumor apoptosis as a tool for assessment of therapeutic efficacy

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL A major challenge in personalized healthcare is predicting how effective a drug treatment is. This is particularly the case in oncology, where there is a call for better therapy monitoring to maximize drug treatment effectiveness leading to improved patient survival and help reduce healthcare costs. GE152, a nuclear imaging agent under development at GE Healthcare, is being evaluated preclinically as a tool to assess therapeutic efficacy by detecting tumor apoptosis. GE152 is based on a 99mTechnetium radiolabelled peptide that shows nanomolar affinity for a specific cell death target, as demonstrated by studies using Biacore technology. Biodistribution using the murine lymphoma (EL4) tumour therapy model has shown increased tumor uptake and retention of GE152 following chemotherapy, with positive tumor:muscle and tumor:blood ratios. Correlation of tumor apoptosis levels (determined by caspase activity) with GE152 tumor retention suggest a trend of increasing agent retention with rising levels of apoptosis (GE152 retention in low apoptotic tumors is 4.9%ID/g; GE152 retention in high apoptotic tumors is 8.2%ID/g).Further validation of GE152 was carried out using an apoptosis-specific inducible cell death model whereby HT29 colorectal cancer cell xenografts engineered to inducibly express either a constitutively active form of caspase-3 (which causes synchronous cell death in vivo when exposed to doxycycline) or an inactive point mutant. GE152 demonstrated greater uptake in tumors undergoing apoptosis (3.6% ID/g) than in controls (1.2% ID/g), correlating with caspase activity levels (and subsequent apoptosis) as determined both enzymatically and by IHC and blood-borne biomarkers of cell death. These results are in agreement with preliminary preclinical imaging studies using SPECT/CT, where region of interest analysis has demonstrated increased post-therapy tumor retention of GE152. We are currently optimizing the performance of GE152 by assessing different radiolabelling precursors to improve imaging agent pharmacokinetics. In addition to the current 99mTechnetium-based approach, we are exploring 18F radiolabelling options that would allow expansion of the agent's utility to PET imaging. 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 4294. doi:1538-7445.AM2012-4294