Definition

A radioconjugate consisting of the human somatostatin receptor subtype 2 (SSTR2)-targeting peptide and Tyr3-octreotide (TOC) analog VMT-a-NET, in which the N-terminus of TOC is conjugated, via polyethylene glycol (PEG) linkers (PEG2), to the cyclen-based lead-specific chelator PSC and labeled with the gamma-emitting radioisotope lead Pb 203, with potential imaging activity of neuroendocrine tumors (NETs) using single photon emission computed tomography (SPECT)/computed tomography (CT). Upon administration of lead Pb 203 VMT-a-NET, the peptide moiety specifically targets and binds to SSTR2, which is present on the cell membranes of many types of NETs. This allows for visualization of SSTR2-positive cells upon SPECT/CT imaging. SSTR2 is overexpressed on NETs and their metastases while most other normal tissues express low levels of SSTR2.