Lead Pb 203 PSV359

**Semantic type:** Indicator, Reagent, or Diagnostic Aid|Pharmacologic Substance

**Definition:** A radioconjugate composed of PSV359, a fibroblast activation protein alpha (FAP)-targeting peptide conjugated to a lead (Pb)-specific chelator, radiolabeled with the gamma-emitting radioisotope Pb 203, with potential use as a tracer for FAP-expressing cancer-associated fibroblasts (CAFs) and tumor cells during single photon emission computed tomography (SPECT)/computed tomography (CT). Upon administration of lead Pb 203 PSV359, the FAP-targeting peptide moiety targets and binds to FAP expressed on CAFs and tumor cells, which allows for the visualization of those cells upon SPECT/CT imaging. FAP, a cell surface protein, is overexpressed on CAFs in the tumor microenvironment (TME) and certain tumor cells.

**Synonyms:** - Lead Pb 203-PSV359 - Lead Pb 203-labeled PSV359 - [203Pb]-PSV359