Development Process

What is a clinical trial?

A clinical trial is a carefully monitored experiment that helps determine whether an investigational product, or an intervention on a disease, is safe and effective for treating the condition in which it is being studied. This means there is no guarantee that a person in a clinical trial will benefit from the investigational product and there may be unanticipated risks associated with participating. Your safety is monitored by the clinical trial physician throughout the conduct of a trial.

The physician who enrolls a patient in a clinical trial is called the “principal investigator” (sometimes “P.I.” for short), the “clinical trial physician”, or the “clinical trial doctor”.

How do clinical trials work?

Clinical trials to evaluate an investigational product can vary quite a bit based on the patient population size.

The table below outlines a typical process for evaluating an investigational product for larger disease populations (e.g. diabetes) in clinical trials.

Clinical Trial Process for Larger Populations

Phase IPhase IIPhase III*Phase IV+

Research goal(s)

Is it safe?

What routes of administration (e.g. oral, intravenous, etc.) and or regimens (e.g. twice per day, biweekly, etc.) can be used?

Is it safe to be dosed with other drugs or conditions?

Is it safe?

Does it work in selected groups of participants?

What is the optimal dose?

Is it safe?

Does it work in a broadly selected group of participants with the condition?

Long-term follow-up+

Does it work in other disorders or in special populations?

Trial participant population

Healthy volunteers or those affected by conditionThose affected by conditionThose affected by conditionThose affected by condition

Number of participants

20-80Several hundredSeveral thousandSeveral thousand


1 – 6 months6 months – 2 years1 – 3 yearsVaried+

Typical Designs

Multiple options, from open-label studies with no controls to randomized, double-blind, controlled trials

Several dose levels

Randomized, double-blind, controlled

A few dose levels

Randomized, double-blind, controlled

Typically one dose level


+Dependent on the specific needs of the product approval.

The clinical trial process is different for rare conditions.

The table below outlines a high-level process that is typical for the evaluation of an investigational product for rare conditions.

Clinical Trial Process for Rare Conditions

Phase I/IIPhase IIIWhat happens next?

Research goal(s)

Is it safe?

Does it work?

What is the best dose and regimen?

What are the best endpoints?
Is it safe?

Does it work?

What is the best dose and regimen?

The full interpretation of the clinical trial data cannot be completed until every participant enrolled has completed the full duration of the trial. Keep in mind that there may be a significant gap in time from when the first participant in the clinical trial is dosed to the time the last participant enrolled in the clinical trial is dosed.

After all the clinical trial participants have completed the full duration of the clinical trial, the data from all participants are extensively analyzed. This period of analysis and interpretation may last months, at which time the data and analyses would be submitted to regulatory agencies for review (timing varies by region).

After this process, there are several scenarios which may occur, including:

  • Additional studies, if the research goal is not fully achieved
  • An extension or long-term follow-up may be required to collect additional safety and efficacy data

Trial participant population

Those affected by conditionThose affected by condition

Number of participants

5-50*Up to several hundred


Varied6 months – 2 years


Randomized, open-label or double-blind, controlled*Randomized, open-label or double-blind, controlled*

*Number of participants and trial designs are dependent on the condition/disorder being studied.

+Phase III trials may not always be required, if safety and efficacy data permits.

How long does it take to complete a clinical trial?

Trial timing/duration depends on many things, including:

  • Trial endpoints (safety and efficacy)
  • How long it takes the investigational product to start working (response time)
  • Other things that we learn in the trial (e.g. new information about the disease or the effect of the investigational product)
  • How long the beneficial effects of the investigational product last

How long does it take to obtain a regulatory/marketing approval so that the potential treatment is available for all appropriate patients?

Before an investigational product can be approved, below are some key questions that need to be answered:

  • What is the right dose to administer?
  • Does the investigational product benefit the intended patient population?
  • Do the benefits outweigh the risks?
  • Has the safety profile of the investigational product been adequately characterized?
  • Are the observed benefits meaningful to clinical trial participants compared to the alternatives?

Some clinical trials are observational and do not include administration of an investigational product. Why is that?

Studies that collect patient or disease information but do not include administration of an investigational product are sometimes referred to as “observational”, “natural history”, or “non-interventional” studies. These types of studies serve several very important purposes in the rare disease community. For example, they help:

  • Increase understanding about the natural history of a disease or condition (the way it presents itself in different people, at different times or developmental stages)
  • Guide the design of later clinical trials in which an investigational product is administered
  • Identify endpoints or other markers of change that can be measured in an interventional clinical trial
  • Prepare clinical trial sites for interventional clinical trial activities
  • Collect participant data that can be used as baseline measurements for a participant that will later receive investigational product, so that they can serve as their own “within participant” control

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