A Well Designed Clinical Trial

A well-designed clinical trial is crucial to ensuring that specific endpoints, or outcomes, are met and that the researchers’ ultimate questions are answered.

The lead researcher in charge of the trial of a specific study is called the Principal Investigator (PI). The PI works with a team of health professionals, often including social workers and study nurses. There is also typically a study coordinator, who oversees the administration of the trial.

Each trial is dictated by a protocol, or design plan, that outlines the hypothesis the researchers will be testing and what methods they will use to do so. The protocol also defines additional details such as the administration methods, dosage, schedule of study visits, follow-up and monitoring procedures, and enrollment criteria.

Enrollment criteria specify who can participate in the study. Inclusion criteria are qualifications that a subject must meet in order to participate in the trial while exclusion criteria disqualify subjects from participation. These criteria help to eliminate any potential confounding factors from the trial in order to ensure it is as controlled and accurate as possible.

In addition to carefully selected enrollment criteria, clinical trials are often randomized to minimize the differences between the controlled group and the experimental group. Randomization helps to ensure the trial is the same in every way except that one group is receiving the novel therapy and one is not, reducing selection bias.

Another method used to reduce bias is called “blinding.” A randomized trial is “blind” if the participant is not told whether he or she is on the experimental or control arm of the study. A “single-blind” study means that one group — either participants or researchers — is unaware of the therapy the participant is taking. In a “double-blind” study, neither group knows who is receiving the experimental therapy and who is receiving a placebo or other therapy. Double-blind trials are considered the most objective as they eliminate the possibility for any conscious or unconscious bias that could affect the outcome.


Phase 1 – Is the treatment safe
Phase I trials use a small number of participants 10-100 individuals to test novel therapies for safety, toxicity, and dose. The first few participants get a low dose of the treatment. If there are only minor side effects, the next few get a higher dose. This process continues until doctors find a dose that’s most likely to work within an acceptable level of side effects. While there may be early indications that a therapy works, determining efficacy is not the goal of Phase I trials.

Phase 2 Does the treatment work
Once the safety of the treatment has been established, Phase II clinical trials test the efficacy or effectiveness, of the therapy on a larger number of participants 50-500 individuals. Phase II trials often run longer than Phase I — typically lasting several months to a few years. As the study progresses, decisions based on the treatment’s efficacy are made to advance to Phase III trials or to terminate the study. Only about one-third of novel therapies make it through Phase II trials.

Phase 3 – Is it better
Phase III clinical trials compare the safety and efficacy of the new treatment against the current standard treatment. Study participants are often picked at random to get either the standard treatment or the new treatment. Phase III clinical trials include a larger number of patients and can last several years. These studies are often carried out across the country (or around the world) at the same time. Data would be submitted to the FDA as evidence for approval of the new therapy.

Phase 4 – What can we still learn?
Once the therapy has been approved and brought to market, studies may continue. Even after testing a new medicine on thousands of people, all the effects of an approved treatment may not be known. Some questions may remain. Are there rare side effects that haven’t been seen yet, or side effects that only show up after taking the medicine for a long time? Additional studies are conducted to monitor the therapy’s performance and determine whether its effectiveness is long-lasting.


While testing novel treatments, therapies, and devices on human subjects are required to approve their use by the broader public, it also necessitates that regulations be established in order to protect the safety of those involved.

Before a clinical trial begins, its protocol must be extensively reviewed by an Institutional Review Board (IRB) to see that its benefits outweigh its risks. IRBs are objective committees made up of members from each research institution, including physicians, statisticians, ethicists, local community members, patient advocates, and sometimes people with the disease under study.

Independent review of the clinical trial protocol by an IRB is required for U.S. studies funded by the Department of Health and Human Services (DHHS), the FDA, and other U.S. federal agencies. In addition to federal requirements, some states also have their own regulations governing human research.

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