The present invention provides novel tetracyclic indole compounds of Formula (I) either as in vivo imaging agents or as therapeutic agents. A method for the preparation of the in vivo imaging agent compound is also provided by the invention, as well as a precursor for use in said method. Pharmaceutical compositions comprising the compounds of the invention are additionally provided. Where the pharmaceutical composition comprises a compound suitable for in vivo imaging, a kit is provided for the preparation of the pharmaceutical composition. In a further aspect, use of the compound for in vivo imaging or treatment of conditions associated with PBR is provided.