Role of the Cholecystokinin System in Anxiolytic Activity of Dipeptide GB-115

Influence of Retrodipeptide Analogue of Cholecystokinin Tetrapeptide (GB-115) and Phenazepam on the Behavior of Rhesus Monkeys under Isolation Conditions

INTRODUCTION

The developed domestic retrodipeptide analogue of cholecystokinin tetrapeptide (CCK) (N-(6-phenylhexanoyl)-glycyltryptophan amide, or compound GB-115) with antagonistic properties in relation to CCK1 receptors has anxiolytic activity previously shown in preclinical and clinical studies. The aim of the study was to evaluate the anxiolytic effect of GB-115 as a tablet form with subchronic oral administration in comparison with phenazepam in nonhuman primates.

MATERIALS AND METHODS

The study was conducted on four male rhesus monkeys (Macaca mulatta) aged 5.7-6.7 years. After a 30-day adaptation to the conditions of individual caging, experiments were performed first with GB-115 (tablets of 0.001 g) and second with phenazepam (tablets of 0.0005 g). Both drugs were administered one at a time (7 days) and then two tablets each (7 days). Behavior was assessed by observing an object with registration according to the "Yes-No" principle of ethogram elements at the background periods, during the administration of the drugs, and after their withdrawal. The stress response was assessed using cortisol and dehydroepiandrosterone sulfate (DHEA-S) levels as biomarkers determined in the blood serum by enzyme immunoassay.

RESULTS

GB-115 (0.001 g each) and phenazepam (0.001 g each) decreased the stay of the animals in the upper part of the cage compared to the background period, indicating decrease in stress response. GB-115 (0.002 g each) reduced the cortisol/DHEA-S ratio. Phenazepam dose-dependently decreased the level of cortisol in the blood serum without affecting the content of DHEA-S. Under administration of phenazepam (0.001 g each), a decreased cortisol/DHEA-S ratio was also observed.

CONCLUSIONS

A positive effect of GB-115 upon subchronic administration on the attenuation of the emotional stress response and the restoration of adaptive behavior in rhesus monkeys comparable to the effect of phenazepam was revealed, which confirms the possibility of using blockade of CCK1 receptors as one of the approaches for treating anxiety disorders.

[Results of a clinical study of a new anxiolytic, a blocker of central cholecystokinin receptors]

AIM

To evaluate anxiolytic action of GB-115, a low-affinity blocker of central cholecystokinin receptors, used in tablets in a dose of 1 mg for the treatment of patients with anxiety disorders in order to determine effective dose, safety, tolerability and efficacy in clinical settings.

MATERIAL AND METHODS

The study included 31 patients (22 women, 9 men) diagnosed with generalized anxiety disorder (GAD, F41.1 according to ICD-10), aged from 22 to 53 years. The duration of treatment was 21 days. The Hamilton Anxiety Rating scale, Psychopathologic symptoms severity evaluation scale (PSSES), Spilberger State-Anxiety Inventory, Multidimensional Fatigue Inventory (MFI), Clinical Global Impression scale (CGI), computerized battery for evaluation of cognitive functions ('NS-Psychotest') were used.

RESULTS AND CONCLUSION

The effective dose of GB-115 was determined at 6 mg per day. Drug action is characterized by fast onset of anxiolytic effect with stimulating properties and beneficial effect on sleep disturbances and autonomic symptoms. GB-115 treatment was associated with favorable changes in attention parameters, reaction time and overall performance. In contrast to first-line drugs for GAD treatment (SSRIs and SNRIs), GB-115 does not induce initial overactivation, anxiety and sleep disturbances. GB-115 is safe and has a good tolerability.