While some readers may know regulatory pathways like the back of their hand, this post is for folks who are relative newbies.
Although the processes for gaining FDA approval for a new drug or medical device has common features, there is one major difference between clinical trials for drugs and medical devices. Drugs always require a series of clinical studies, but medical devices require a series of clinical trials only to the extent that they represent risk.
Drugs may be defined as a medicine or substance introduced into the body for the cure, mitigation, treatment or prevention of disease through a chemical or metabolic action. A medical device is defined as any instrument, apparatus, implant, machine, in vitro reagent or similar or related article intended to diagnose, prevent or treat disease but NOT through chemical action OR metabolic processes. A medical device acts locally and effects the structure of the human tissue (or organ).
Medical devices are classified according to their risk
Class I medical devices are considered the least risky and general controls are considered adequate to demonstrate their safety; a clinical trial is not needed for Class I devices. Class II medical devices represent intermediate risk, and special controls are required to demonstrate their safety, i.e. a 510K filing. Class III medical devices have a substantial risk associated with their use, and pre-market approval (PMA) is compulsory. This is also known as an IDE.
There is another point of difference: drugs often require a larger number of study subjects to identify side effects while fewer subjects may be needed to prove the safety of a medical device.
Before a pharma or biotech companies consider clinical trials, they conduct basic research to identify promising compounds or delivery mechanisms that may positively impact human health. Then researchers design feasibility studies to test hypotheses. Typically, a feasibility study is conducted with animals that have been specially bred, or a human cell line of known properties or composition.
If proved promising, the research moves into a phase where human beings are tested, called Phase I. Normally, Phase I studies are done on healthy volunteers. The purpose of Phase I trials is to determine metabolism and pharmacological action, and demonstrate safety and tolerance.
If Phase I proves promising, research moves into Phase II, which is done with a small number of patients who have a disease that you seek to treat. At this point, the patient pool is rather circumscribed, perhaps 25-50 patients. The aim is to demonstrate the safety and effectiveness of the drug.
Phase II-III studies are often called pivotal studies.
Particularly in Phase III, investigators can enroll thousands of patients worldwide.
These studies may be designed to modify dosage, delineate the benefits and risks, or to measure the safety or efficacy of new drugs against existing drugs in the marketplace.
In Phase III and IV, one “study” may actually consist of 4 or 5 different “studies” each of which tests a slightly different procedure or dosage.
Phase IV studies are also called post approval or post surveillance studies. They have become more prevalent as the FDA seeks to obtain additional information regarding the risks, benefits and optimal use of drugs (or devices) that are already commercially available.
This is a rather generic overview of what happens in clinical trials. The process for gaining regulatory approval may be adjusted for medical devices, but the approach still holds, i.e. more subjects get recruited and a larger number of sites become involved as safety and efficacy is demonstrated on an ever-larger groups of subjects.
Here is a great infographic from the U.S. Food and Drug Administration, that sums up the details of what happens with drugs that are tested and then submitted for FDA approval.