Clinical data
Routes of
ATC code
  • None
  • 1-(2-{bis[4-(trifluoromethyl)phenyl]methoxy}ethyl)-
    -3,6-dihydro-2H-pyridine-5-carboxylic acid
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass473.415 g·mol−1
3D model (JSmol)
  • C1CN(CC(=C1)C(=O)O)CCOC(C2=CC=C(C=C2)C(F)(F)F)C3=CC=C(C=C3)C(F)(F)F
  • InChI=InChI=1S/C23H21F6NO3/c24-22(25,26)18-7-3-15(4-8-18)20(16-5-9-19(10-6-16)23(27,28)29)33-13-12-30-11-1-2-17(14-30)21(31)32/h2-10,20H,1,11-14H2,(H,31,32)

CI-966 (developmental code name) is a central nervous system depressant acting as a GABA reuptake inhibitor, specifically a highly potent and selective blocker of the GABA transporter 1 (GAT-1) (IC50 = 0.26 μM),[1] and hence indirect and non-selective GABA receptor full agonist.[2][3] It was investigated as a potential anticonvulsant, anxiolytic, and neuroprotective therapeutic but was discontinued during clinical development due to the incidence of severe adverse effects at higher doses and hence was never marketed.[2]

In a phase I human clinical trial while under development for the treatment of epilepsy, CI-966 was assessed at doses of 1–10 mg, 25 mg, and 50 mg.[4] While the 1–10 mg dosages were well tolerated, the 25 mg dose produced memory deficits and the 50 mg dose was found to produce "a variety of severe neurological and psychiatric symptoms" and "serious psychotic adverse effects" of prolonged (several-day) duration and demonstrated "severe adverse CNS symptoms such as memory deficits, myoclonus and tremors, unresponsiveness and subsequent severe psychological disturbances".[2][4][5][6][7] The psychotomimetic effects produced by CI-966 are reportedly "similar to those of schizophrenia" and show "a similar phenotype to that seen with the psychotomimetics that block the effects of glutamate at the NMDA receptor",[8][9] and the psychiatric effects of CI-966 were also described as resembling those seen in patients with mania in addition to schizophrenia.[4] These research findings were responsible for the discontinuation of the clinical development of CI-966.[2][5][7] In addition, on the basis of these findings, the drug has been characterized as a hallucinogen similarly to the potent GABAA receptor full agonist muscimol (a constituent of the hallucinogenic Amanita muscaria (fly agaric) mushrooms).[10]

In contrast to CI-966, the marketed selective GAT-1 blocker (and analogue of CI-966) tiagabine has been found at the dosages in which it has been studied and used to have far lower although non-absent potential for the same adverse effects of the former, including psychotic reactions.[6] This may be due to differences in pharmacology or potency between CI-966 and tiagabine or might be accounted for the possibility that the initial doses of CI-966 studied in humans simply were too high.[2][11] In addition to tiagabine, the marketed anticonvulsant GABA transaminase (GABA-T) inhibitor (and hence also an indirect and non-selective GABA receptor agonist) vigabatrin has also been associated with acute psychotic episodes, hallucinations, and other psychiatric adverse reactions, albeit less commonly.[12][13][14]

See also


  1. ^ Chikako Tanaka; Norman G. Bowery (6 December 2012). GABA: Receptors, Transporters and Metabolism. Birkhäuser. pp. 70–. ISBN 978-3-0348-8990-2.
  2. ^ a b c d e Linda Pullan; Jitendra Patel (13 November 1995). Neurotherapeutics: Emerging Strategies. Springer Science & Business Media. pp. 93–94, 207–208. ISBN 978-1-59259-466-5.
  3. ^ Green, A.Richard; Hainsworth, Atticus H.; Jackson, David M. (2000). "GABA potentiation: a logical pharmacological approach for the treatment of acute ischaemic stroke". Neuropharmacology. 39 (9): 1483–1494. doi:10.1016/S0028-3908(99)00233-6. ISSN 0028-3908. PMID 10854894. S2CID 39073036.
  4. ^ a b c Sedman, Allen J.; Gilmet, Gregory P.; Sayed, Albert J.; Posvar, Edward L. (1990). "Initial human safety and tolerance study of a GABA uptake inhibitor, Cl-966: Potential role of GABA as a mediator in the pathogenesis of schizophrenia and mania". Drug Development Research. 21 (3): 235–242. doi:10.1002/ddr.430210309. ISSN 0272-4391. S2CID 84577983.
  5. ^ a b Jie Jack Li; E. J. Corey (3 April 2013). Drug Discovery: Practices, Processes, and Perspectives. John Wiley & Sons. pp. 262–. ISBN 978-1-118-35446-9.
  6. ^ a b White, H. S. (2004). "First Demonstration of a Functional Role for Central Nervous System Betaine/ -Aminobutyric Acid Transporter (mGAT2) Based on Synergistic Anticonvulsant Action among Inhibitors of mGAT1 and mGAT2". Journal of Pharmacology and Experimental Therapeutics. 312 (2): 866–874. doi:10.1124/jpet.104.068825. ISSN 0022-3565. PMID 15550575. S2CID 30717285.
  7. ^ a b Armer, Richard (2000). "Inhibitors of Mammalian Central Nervous System Selective Amino Acid Transporters". Current Medicinal Chemistry. 7 (2): 199–209. doi:10.2174/0929867003375380. ISSN 0929-8673. PMID 10637362.
  8. ^ Jan Egebjerg; Arne Schousboe; Povl Krogsgaard-Larsen (4 October 2001). Glutamate and GABA Receptors and Transporters: Structure, Function and Pharmacology. CRC Press. pp. 419–. ISBN 978-0-203-29938-8.
  9. ^ Marino, M.J.; Davis, R.E.; Meltzer, H.; Knutsen, L.J.S.; Williams, M. (2007). "Schizophrenia". Comprehensive Medicinal Chemistry II: 17–44. doi:10.1016/B0-08-045044-X/00162-0. ISBN 9780080450445.
  10. ^ Hollister, Leo E. (1990). "New class of hallucinogens: GABA-enhancing agents". Drug Development Research. 21 (3): 253–256. doi:10.1002/ddr.430210311. ISSN 0272-4391. S2CID 143868762.
  11. ^ Krogsgaard-Larsen, Povl; Frolund, Bente; Frydenvang, Karla (2000). "GABA Uptake Inhibitors. Design, Molecular Pharmacology and Therapeutic Aspects". Current Pharmaceutical Design. 6 (12): 1193–1209. doi:10.2174/1381612003399608. ISSN 1381-6128. PMID 10903390.
  12. ^ James Willmore, L.; Abelson, Mark B.; Ben-Menachem, Elinor; Pellock, John M.; Donald Shields, W. (2009). "Vigabatrin: 2008 Update". Epilepsia. 50 (2): 163–173. doi:10.1111/j.1528-1167.2008.01988.x. ISSN 0013-9580. PMID 19230067.
  13. ^ Levinson DF, Devinsky O (1999). "Psychiatric adverse events during vigabatrin therapy". Neurology. 53 (7): 1503–11. doi:10.1212/wnl.53.7.1503. PMID 10534259.
  14. ^ Ferrie CD, Robinson RO, Panayiotopoulos CP (1996). "Psychotic and severe behavioural reactions with vigabatrin: a review". Acta Neurol. Scand. 93 (1): 1–8. doi:10.1111/j.1600-0404.1996.tb00161.x. PMID 8825264. S2CID 40041098.

Further reading