Table 1.

Synthetic ligands of the translocator protein (TSPO)

Class	Compound	Structure	Properties
4‐Phenylquinazoline‐2‐carboxamides	ER176		Aza‐isosteres of PK11195. In particular, PET radioligands with sensitivity to robustly image all three TSPO genotypes in human brain
Benzodiazepines	Ro‐5‐4864		Sedative, neuroprotective, agonist, or partial agonist of TSPO with nanomolar binding affinity
Benzoxazines	Etifoxine		Anxiolytic effects, anti‐neurodegenerative effects mediated by TSPO, PET ligand
Cholest‐4‐en‐3‐one	TRO40303		Agonist, used in cardioprotection, ALS, putatively interrupts the formation of mitochondrial transition pore
Imidazopyridine acetamides	DPA		Ligand used for in vivo imaging of TSPO
Indoleacetamides	FGIN‐1‐27		TSPO ligand characterized by steroidogenic and pro‐apoptotic activities
Isoquinoline carboxamides	PK11195		TSPO antagonist with nanomolar affinity, widely used for characterizing expression and function in various tissues and cells, widely used PET ligand
N,N‐Dialkyl‐2‐phenylindol‐3‐ylglyoxylamide (PIGA)	PIGA 1128		Used to modify steroidogenic activity of TSPO, specifically in relation to neurosteroids; developed for anxiolytic activity
Phenoxyphenyl acetamides	PBR28		Developed as PET ligands for TSPO, specifically used for neuroinflammation; brain penetrant
Phenylpurines	Emapunil		Ligand with rapid anxiolytic effects
Pyrrolobenzoxazepines	OXA‐17		Developed as anti‐cancer therapies, some activity for cannabinoid receptors
Quinoline carboxamides	VCM198M		Used as radioligand for TSPO imaging
Vinca alkaloids	Vinpocetine		Ligand with neuroprotective activity that binds TSPO and other receptors such as adrenoceptors

This Table also shows the chemical structures of the TSPO ligands along with their pharmacological effects and clinical or preclinical use.