Dr Michael Silverman, principal at BioStrategics Consulting Ltd, continues his discussion this week on the Clinical Trial Protocol. To achieve a successful protocol, the choice of the patient population is critical.
This week I would like to discuss a make or break aspect of the clinical trial protocol; the patient population. The definition of the patient population is one of the most important conditions for testing a drug.
In many situations, it will not be the target population that is desired for ultimate labeling of the product. Early in development, or for pharmacokinetics trials, normal volunteers are often the most suitable subjects. The search for very specific or novel effects – such as unique pharmacodynamic behavior or pharmacogenomic profiles – may be conducted in small, highly selective subsets of the larger patient population. On the other hand, the potential for use in special populations may require dedicated studies in patients with, for example, renal or hepatic impairment. Eventually, pivotal efficacy trials must be conducted in a population that matches the targeted market population exactly, if the drug is to receive regulatory approval for the desired label.
From a practical standpoint, the trial population is defined by the protocol inclusion and exclusion criteria, which conceptually, fall into three distinct categories.
- First, criteria may be used to denote characteristics that will make trial participants representative of the eventual market population – specific qualities such as age, duration and severity of disease, previous treatment and its effects, and the like.
- Second, and particularly true of many exclusions, the criteria may have little to do with characteristics of the target population but may seek to exclude patients with concomitant conditions that may put a patient at higher risk and/or could obscure the assessment of the drug effect. Such conditions often include kidney or liver disease, malignancy, cognitive or behavioral dysfunction, or the use of certain medications.
- Finally, several criteria are used to protect subject rights and safety, and to fulfill regulatory requirements; these include the signature of an Institutional Review Board-approved informed consent document, knowledge and ability to cooperate with the protocol, and proscription of other investigational substances within a given time period.
Next week, I will cover protocol design and sample size of the protocol. So stay tuned.
Dr Michael Silverman is the principal clinical consultant at BioStrategics Consulting Ltd., a clinical development consulting company based in Marblehead, MA, with business interests around the globe. Dr Silverman would be delighted to hear your thoughts on today’s blog, your experiences, or anecdotes and of course, your questions. To make comments or ask questions, click on this link.
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