Emapunil (AC-5216, XBD-173) is an anxiolytic drug which acts as a selective agonist at the peripheral benzodiazepine receptor, also known as the mitochondrial 18 kDa translocator protein or TSPO.[1][2] This protein has multiple functions, among which is regulation of steroidogenesis,[3][4] particularly the production of neuroactive steroids such as allopregnanolone in the brain.[5][6][7] In both animal and human trials, emapunil produced fast acting anxiolytic and anti-panic effects, without producing sedation or withdrawal symptoms following cessation of use.[8][9] Emapunil is also used in its 11C radiolabelled form to map the distribution of TSPO receptors in the brain.[10][11]

Clinical data
ATC code
  • none
  • N-benzyl-N-ethyl-2-(7-methyl-8-oxo-2-phenylpurin-9-yl)acetamide
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass401.470 g·mol−1
3D model (JSmol)
  • CCN(Cc1ccccc1)C(=O)Cn2c3c(cnc(n3)c4ccccc4)n(c2=O)C
  • InChI=1S/C23H23N5O2/c1-3-27(15-17-10-6-4-7-11-17)20(29)16-28-22-19(26(2)23(28)30)14-24-21(25-22)18-12-8-5-9-13-18/h4-14H,3,15-16H2,1-2H3

See alsoEdit


  1. ^ Kita A, Kohayakawa H, Kinoshita T, Ochi Y, Nakamichi K, Kurumiya S, Furukawa K, Oka M (August 2004). "Antianxiety and antidepressant-like effects of AC-5216, a novel mitochondrial benzodiazepine receptor ligand". British Journal of Pharmacology. 142 (7): 1059–72. doi:10.1038/sj.bjp.0705681. PMC 1575165. PMID 15249420.
  2. ^ Mealy NE, Bayés M, Lupone B, Balcells M (2006). "Psychiatric Disorders". Drugs of the Future. 31 (3): 259.
  3. ^ Veenman L, Papadopoulos V, Gavish M (2007). "Channel-like functions of the 18-kDa translocator protein (TSPO): regulation of apoptosis and steroidogenesis as part of the host-defense response". Current Pharmaceutical Design. 13 (23): 2385–405. doi:10.2174/138161207781368710. PMID 17692008.
  4. ^ Falchi AM, Battetta B, Sanna F, Piludu M, Sogos V, Serra M, Melis M, Putzolu M, Diaz G (August 2007). "Intracellular cholesterol changes induced by translocator protein (18 kDa) TSPO/PBR ligands". Neuropharmacology. 53 (2): 318–29. doi:10.1016/j.neuropharm.2007.05.016. PMID 17631921.
  5. ^ Kita A, Furukawa K (April 2008). "Involvement of neurosteroids in the anxiolytic-like effects of AC-5216 in mice". Pharmacology Biochemistry and Behavior. 89 (2): 171–8. doi:10.1016/j.pbb.2007.12.006. PMID 18201755.
  6. ^ Da Settimo F, Simorini F, Taliani S, La Motta C, Marini AM, Salerno S, Bellandi M, Novellino E, Greco G, Cosimelli B, Da Pozzo E, Costa B, Simola N, Morelli M, Martini C (September 2008). "Anxiolytic-like effects of N,N-dialkyl-2-phenylindol-3-ylglyoxylamides by modulation of translocator protein promoting neurosteroid biosynthesis". Journal of Medicinal Chemistry. 51 (18): 5798–806. doi:10.1021/jm8003224. PMID 18729350.
  7. ^ Taliani S, Da Settimo F, Da Pozzo E, Chelli B, Martini C (September 2009). "Translocator Protein Ligands as Promising Therapeutic Tools for Anxiety Disorders". Current Medicinal Chemistry. 16 (26): 3359–80. doi:10.2174/092986709789057653. PMID 19548867.
  8. ^ Rupprecht R, Rammes G, Eser D, Baghai TC, Schüle C, Nothdurfter C, Troxler T, Gentsch C, Kalkman HO, Chaperon F, Uzunov V, McAllister KH, Bertaina-Anglade V, La Rochelle CD, Tuerck D, Floesser A, Kiese B, Schumacher M, Landgraf R, Holsboer F, Kucher K (June 2009). "Translocator Protein (18 kD) as Target for Anxiolytics Without Benzodiazepine-Like Side Effects". Science. 325 (5939): 490–3. doi:10.1126/science.1175055. PMID 19541954. S2CID 26125316.
  9. ^ Kita A, Kinoshita T, Kohayakawa H, Furukawa K (June 2009). "Lack of tolerance to anxiolysis and withdrawal symptoms in mice repeatedly treated with AC-5216, a selective TSPO ligand". Progress in Neuro-psychopharmacology & Biological Psychiatry. 33 (6): 1040–5. doi:10.1016/j.pnpbp.2009.05.018. PMID 19497344.
  10. ^ Zhang MR, Kumata K, Maeda J, Yanamoto K, Hatori A, Okada M, Higuchi M, Obayashi S, Suhara T, Suzuki K (November 2007). "11C-AC-5216: a novel PET ligand for peripheral benzodiazepine receptors in the primate brain". Journal of Nuclear Medicine. 48 (11): 1853–61. doi:10.2967/jnumed.107.043505. PMID 17978354.
  11. ^ Miyoshi M, Ito H, Arakawa R, Takahashi H, Takano H, Higuchi M, Okumura M, Otsuka T, Kodaka F, Sekine M, Sasaki T, Fujie S, Seki C, Maeda J, Nakao R, Zhang MR, Fukumura T, Matsumoto M, Suhara T (June 2009). "Quantitative Analysis of Peripheral Benzodiazepine Receptor in the Human Brain Using PET with 11C-AC-5216". Journal of Nuclear Medicine. 50 (7): 1095–101. doi:10.2967/jnumed.109.062554. PMID 19525461.