Potencies of diazepam metabolites in rats trained to discriminate diazepam

A translational pharmacology approach to understanding the predictive value of abuse potential assessments

Within the drug development industry the assessment of abuse potential for novel molecules involves the generation and review of data from multiple sources, ranging from in-vitro binding and functional assays through to in-vivo nonclinical models in mammals, as well as collection of information from studies in humans. This breadth of data aligns with current expectations from regulatory agencies in both the USA and Europe. To date, there have been a limited number of reviews on the predictive value of individual models within this sequence, but there has been no systematic review on how each of these models contributes to our overall understanding of abuse potential risk. To address this, we analyzed data from 100 small molecules to compare the predictive validity for drug scheduling status of a number of models that typically contribute to the abuse potential assessment package. These models range from the assessment of in-vitro binding and functional profiles at receptors or transporters typically associated with abuse through in-vivo models including locomotor activity, drug discrimination, and self-administration in rodents. Data from subjective report assessments in humans following acute dosing of compounds were also included. The predictive value of each model was then evaluated relative to the scheduling status of each drug in the USA. In recognition of the fact that drug scheduling can be influenced by factors other than the pharmacology of the drug, we also evaluated the predictive value of each assay for the outcome of the human subjective effects assessment. This approach provides an objective and statistical assessment of the predictive value of many of the models typically applied within the pharmaceutical industry to evaluate abuse potential risk. In addition, the impact of combining information from multiple models was examined. This analysis adds to our understanding of the predictive value of each model, allows us to critically evaluate the benefits and limitations of each model, and provides a method for identifying opportunities for improving our assessment and prediction of abuse liability risk in the future.

Behavioral effects of several new anxiolytics and putative anxiolytics

The behavioral effects of several new anxiolytics and putative anxiolytics were evaluated in two tests sensitive for anxiolytic activity. In the first test, rats were trained to lever-respond for sweetened milk under a multiple variable-interval fixed-ratio (VI-FR) schedule of reinforcement. In the FR component a brief electric shock coincided with the presentation of reward (i.e. conflict procedure). Treatment of these rats with diazepam, tracazolate, CGS-9896, and the pyrimidinylpiperazine derivatives buspirone, gepirone and ipsapirone (TVX Q 7821) significantly increased responding that was suppressed by foot-shock. A common metabolite of the pyrimidinylpiperazines, l-PP, had no affect on punished responding. A second group of rats was trained to discriminate diazepam from saline using a two-lever operant choice procedure. Diazepam-stimulus generalization occurred to CGS-9896, CL 218,872, zopiclone and tracazolate, but not to buspirone, gepirone, ipsapirone or l-PP. It was concluded that while all of the new compounds examined appear to share an anxiolytic effect as demonstrated by their activity in the conflict procedure, the pyrimidinylpiperazine agents do not share discriminative stimulus properties which are common to drugs which act via the benzodiazepine receptor.