Abstract 357: Nonclinical tumor efficacy studies of [18F]AH113804, a novel PET imaging agent with high affinity for the human c-Met receptor

Abstract

Abstract c-Met, the tyrosine-kinase receptor for hepatocyte growth factor (HGF)/scatter factor, is involved in tumour growth, invasion and metastasis in many human cancers of epithelial origin. Various tumour types are reported to overexpress c-Met, whilst expression in most normal tissues is relatively low. [18F]AH113804 is a peptide-based molecular imaging agent being developed by GE Healthcare for the in vivo evaluation of tumour and metastatic c-Met expression by PET imaging. In vitro affinity studies with fluorescently labelled analogues confirmed that whilst the AH113804 peptide had high affinity for human c-Met (hc-Met), there was limited or no affinity for dog or rodent c-Met, respectively. In mice, relatively high uptake of [18F]AH113804 was observed in human xenograft tumours known to express high levels of hc-Met, with rapid clearance from key background tissues such as muscle (tumour to muscle ratio of >5 achieved by 30 minutes post-injection). This biodistribution profile allowed the tumour to be clearly visualised by micro-PET imaging. Tumour uptake was significantly reduced by co-administration of excess non-radioactive peptide, confirming tumour uptake was specific. Tumour uptake of [18F]AH113804 was also shown to correlate with expression of hcMet, with a relative retention of 2.0±0.1, 1.2±0.2 and 0.7±0.2% retained dose per gram normalised for body weight (% rd/g/100g bw) 60 minutes post-injection in xenograft tumours with relatively high (HT-29 tumours), lower (U87 tumours) and no (LLC tumours) expression of hc-Met respectively (as assayed by ELISA). Finally, 111InCl3 was used in a dual tumour model as a non-specific marker of blood pool to confirm differences in tumour uptake were not related to differences in tumour blood pool or delivery. There was a significant difference in [18F]AH113804 uptake between HT-29 (2.2±0.8% rd/g/100 g bw) and LLC (0.9±0.2% rd/g/100 g bw) tumours (p<0.001) 30 minutes post-injection, whilst uptake of 111InCl3 was similar for the two tumour types (HT-29; 0.9±0.2% rd/g/100 g bw, LLC; 1.1±0.2% rd/g/100 g bw). Overall, these results confirmed that [18F]AH113804 has desirable properties for a c-Met targeted molecular imaging agent. Since there are a number of anti-c-Met therapies in clinical development, [18F]AH113804 has potential to be used as an aid in therapy selection and/or monitoring. Furthermore, [18F]AH113804 may be of use in patient stratification and prediction of patient outcome for specific cancers. 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 357. doi:1538-7445.AM2012-357