Development of an enzymatic pretargeting strategy for dual-modality imagingElectronic supplementary information (ESI) available: Detailed experimental methods, full characterisation data for all compounds, cell labelling data, SPECT/CT images and ex vivo biodistribution data. See DOI: 10.1039/c4cc10265g

A pretargeted imaging strategy based on the HaloTag dehalogenase enzyme is described. Here, a HaloTag-Trastuzumab conjugate has been used as the primary agent targeting HER2 expression, and three new radiolabelled HaloTag ligands have been used as secondary agents, two of which offer dual-modality (SPECT/optical) imaging capability. An in vitro pretargeted imaging strategy based on the HaloTag enzyme is described. Dual-modality (SPECT and optical) HaloTag ligands enable the detection of HER2 expression.