CI-988 (PD-134,308) is a drug which acts as a cholecystokinin antagonist, selective for the CCKB subtype. In animal studies it showed anxiolytic effects[1][2] and potentiated the analgesic action of both morphine[3] and endogenous opioid peptides,[4][5] as well as preventing the development of tolerance to opioids[6][7] and reducing symptoms of withdrawal.[8][9] Consequently, it was hoped that it might have clinical applications for the treatment of pain and anxiety in humans, but trial results were disappointing with only minimal therapeutic effects observed even at high doses.[10][11][12][13] The reason for the failure of CI-988 and other CCKB antagonists in humans despite their apparent promise in pre-clinical animal studies is unclear, although poor pharmacokinetic properties of the currently available drugs are a possible explanation,[14] and CCKB antagonists are still being researched for possible uses as adjuvants to boost the activity of other drugs.[15]
^Durieux C, Derrien M, Maldonado R, Valverde O, Blommaert A, Fournié-Zaluski MC, Roques BP (March 1994). "CCK-B antagonists exhibit antidepressant-like effects and potentiate endogenous enkephalin analgesia. Correlation with in vivo binding affinities and brain penetration". Annals of the New York Academy of Sciences. 713: 355–7. doi:10.1111/j.1749-6632.1994.tb44091.x. PMID8185186. S2CID23317834.
^Valverde O, Maldonado R, Fournie-Zaluski MC, Roques BP (July 1994). "Cholecystokinin B antagonists strongly potentiate antinociception mediated by endogenous enkephalins". The Journal of Pharmacology and Experimental Therapeutics. 270 (1): 77–88. PMID8035345.
^Hoffmann O, Wiesenfeld-Hallin Z (December 1994). "The CCK-B receptor antagonist Cl 988 reverses tolerance to morphine in rats". NeuroReport. 5 (18): 2565–8. doi:10.1097/00001756-199412000-00040. PMID7696605.
^Valverde O, Roques BP (March 1998). "Cholecystokinin modulates the aversive component of morphine withdrawal syndrome in rats". Neuroscience Letters. 244 (1): 37–40. doi:10.1016/s0304-3940(98)00118-9. PMID9578139. S2CID34384142.
^Bradwejn J, Koszycki D, Paradis M, Reece P, Hinton J, Sedman A (December 1995). "Effect of CI-988 on cholecystokinin tetrapeptide-induced panic symptoms in healthy volunteers". Biological Psychiatry. 38 (11): 742–6. doi:10.1016/0006-3223(95)00081-X. PMID8580227. S2CID1096074.
^Adams JB, Pyke RE, Costa J, Cutler NR, Schweizer E, Wilcox CS, et al. (December 1995). "A double-blind, placebo-controlled study of a CCK-B receptor antagonist, CI-988, in patients with generalized anxiety disorder". Journal of Clinical Psychopharmacology. 15 (6): 428–34. doi:10.1097/00004714-199512000-00007. PMID8748432.
^van Megen HJ, Westenberg HG, den Boer JA, Slaap B, van Es-Radhakishun F, Pande AC (February 1997). "The cholecystokinin-B receptor antagonist CI-988 failed to affect CCK-4 induced symptoms in panic disorder patients". Psychopharmacology. 129 (3): 243–8. doi:10.1007/s002130050186. PMID9084062. S2CID12570838.
^Pande AC, Greiner M, Adams JB, Lydiard RB, Pierce MW (September 1999). "Placebo-controlled trial of the CCK-B antagonist, CI-988, in panic disorder". Biological Psychiatry. 46 (6): 860–2. doi:10.1016/s0006-3223(99)00090-6. PMID10494457. S2CID5801419.
^Le Guen S, Mas Nieto M, Canestrelli C, Chen H, Fournié-Zaluski MC, Cupo A, et al. (July 2003). "Pain management by a new series of dual inhibitors of enkephalin degrading enzymes: long lasting antinociceptive properties and potentiation by CCK2 antagonist or methadone". Pain. 104 (1–2): 139–48. doi:10.1016/s0304-3959(02)00486-4. PMID12855323. S2CID38514264.