Basics of Drug Development

In previous posts, we’ve explored both the biggest bottleneck in drug development and a potential way to expedite it.

It might be helpful to take a step back and ask a basic question: what exactly is drug development? 

Understanding the Different Parts of Drug Development

At a high level, drug (or biopharmaceutical) research and development is the entire process of discovering and testing a new drug. The goal of this process is to market and sell the new drug for patient use. 

As shown in the figure below, this process can be broadly divided into two periods:

  1. Drug discovery (in orange/yellow). The goal of discovery is to find a drug for a particular disease.
  2. Clinical development (in green/blue/purple). The goal of clinical development is to demonstrate that a new drug is safe and effective for people.

Since Unlearn focuses on applying machine learning to clinical development, we will solely discuss clinical development in this post. 

Bird's-Eye View of Clinical Development

Many people describe clinical development as challenging. So here’s another question worth asking: why is clinical development so difficult? 

Here are some of the main reasons:

  1. It takes up to a decade to complete and is expensive: phase III clinical trials for Alzheimer’s disease, for example, cost ~$40,000/subject [1]. If 2000 subjects are recruited [2], the cost would amount to $80 million. 
  2. High rates of failure occur at different steps of clinical development. Almost 70% of clinical trial sites fail to meet enrollment requirements for a given trial [3]. 90% of drugs that enter clinical trials don’t make it to market [4]. 
  3. Multiple key stakeholders—with different roles and concerns—must all work together to bring a drug from clinical development to market.

The three major stakeholders include:

Phases of Clinical Development

Now that we’ve talked about what clinical development is overall—including the main challenges and key players—you might be asking this question: what happens during the main steps of clinical development?

So let’s dive right in.

In order to begin testing a new drug in people, the biopharma company must submit an investigational new drug application (IND) to the FDA. Once the IND is approved, the company can begin conducting clinical trials with human subjects. Clinical trials are necessary to make sure the drug is safe and works in people. As written in this post, the company must first identify and activate clinical trial sites, as well as recruit eligible subjects to participate.  

A typical clinical trial occurs in 4 phases, the order of which is prescribed by the FDA.

Once Phase III is complete, the company can submit a new drug application (NDA) to the FDA. The FDA reviews the NDA to decide whether to approve the company’s drug.

After the FDA approves the NDA, the company will conduct phase IV trials, or post-marketing monitoring and research. During this phase, the company can track the safety, benefits, and optimal use of the drug after it becomes available to patients. By collecting information during this phase, the FDA can make necessary changes to the drug (e.g. best dosage or whether it can be used with other drugs) [6]. 

That’s basically it! This post should help you better understand what clinical development is and how it works generally [7]. In future posts, we will talk more about clinical trials—innovative trial designs, patient perspectives, and other relevant issues.






[5] Although human subjects and patients are often used interchangeably, they are not necessarily the same term according to the FDA. The FDA defines a human subject as “an individual who is or becomes a participant in research, either as a recipient of the test article or as a control. A subject may be either a healthy individual or a patient.”

[6] Facts about each phase adapted from and

[7] For more details about clinical development, consult steps 3-5 on the FDA website:

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