What is a Phase I Clinical Trial?


When a new drug or medical device is discovered, it will need to go through clinical testing to receive approval from the FDA. Clinical research on the drug is conducted through a clinical trial (also know as a clinical study) which is comprised of multiple different phases. Each phase serves a specific purpose for moving the new drug or medical device to market. The first phase is especially important, as it can be the ‘make or break’ phase for a new medical discovery. We’ll dive into what a Phase I clinical trial is, its purpose, and everything in between.

What is a Phase I clinical trial?

A Phase I clinical trial is the first time that a new drug, treatment, or medical device is tested in human study participants. Phase I trials are usually conducted in healthy volunteers, and are designed to determine whether a drug or treatment is safe for humans. Phase I trials provide vital information about the pharmacokinetics (study of how the body processes a drug) and pharmacodynamics (how the body responds to a drug) of an experimental medication, treatment, or device.

Phase I clinical trials are often done on small groups of people due to not knowing what kind of side effects might occur. In this way, Phase I clinical trials help researchers understand how effective their treatment will be once it moves into larger scale studies like Phase II or III.

What is the purpose of a Phase I clinical trial?

The purpose of a Phase I clinical trial is to test the safety of a new drug, treatment, or medical device in human study participants. Phase I clinical trials are usually small, with a few dozen participants. This helps ensure that any side effects in humans can be detected and dealt with before the drug is used more widely.

What is involved in a Phase 1 clinical trial?

A Phase 1 clinical trial is the first step the clinical trial process and occurs after pre-clinical studies. A Phase 1 clinical trial is not designed to test the effectiveness of a drug—that will happen in later phases. Instead, Phase 1 involves testing the safety of a new product in human study participants.

Phase 1 trials typically have a slow recruitment process and usually begin with small group of healthy volunteers. Some Phase 1 trials may recruit patients who have illnesses or diseases that are similar to those affected by the condition being studied, such as cancer.

Although each Phase 1 clinical trial has its own protocol, here are some of the steps involved:

  • Safety evaluation: The drug’s side effects are documented through physical exams, blood tests and other medical tests.
  • Dose escalation (or dose-finding): In this step, researchers gradually increase doses until they learn how much patients can safely tolerate without experiencing serious side effects or other problems. They also observe what happens when too much of a substance enters their bodies at once—this might reveal new information about how it works inside our systems or show that there could be potentially dangerous interactions between this substance and other medications we take regularly (such as aspirin).

How long does a Phase I clinical trial take?

A Phase I clinical trial can take from 2 to 5 years to complete. The time it takes for a Phase I clinical trial to be completed depends on several factors including:

  • The condition being studied, the drug being tested and its formulation, and the dosage being used (typically 0-100 mg/kg body weight)
  • The number of patients in the trial (30-80)
  • The length of time required for recruitment and retention of patients, as well as follow-up data collection

Phase I clinical trials are conducted in 3 parts: 1) Screening Phase; 2) Treatment Phase; and 3) Safety Follow-up Evaluation.

What happens after a Phase 1 clinical trial?

The results of a Phase I clinical trial are reviewed by the FDA. If the results are positive, your drug may be eligible for further development through Phase II or III trials. This is good news! It means that your drug has potential to help people with a disease and could one day be approved by the FDA as an effective treatment.

If your Phase I clinical trial was negative, it’s still important to share those results with others in the scientific community as well as with investors who supported you during this initial round of research and development. However, it means that your drug isn’t likely to work out in later phases of testing (or at least not without significant changes). You’ll either need to find another approach or abandon that particular line of research altogether—and try something else!

What does a CRO do in a Phase 1 clinical trial?

A Contract Research Organization (CRO) is a company that administers clinical trials on behalf of pharmaceutical and biotech companies. They ensure that the clinical trial is conducted according to the protocol and regulatory requirements, as well as ethical standards. The CRO will also ensure that the clinical trial is conducted according to the highest possible standards for the best trial outcomes.

Typical services provided by CROs to pharmaceutical companies

All CROs offer different services, but in general a CRO will provide a wide range of services to pharmaceutical and biotech companies. CRO services specific to Phase I clinical trials include:

  • Conducting and managing the study
  • Developing the protocol and finalizing patient eligibility criteria, objectives, and procedures for the study
  • Recruiting patients who meet the eligibility criteria as defined in the protocol
  • Ensuring that each patient meets all requirements before enrolling them in a trial (e.g., physical exams)


It’s clear that Phase 1 clinical trials are crucial to a drug’s success, which is why it’s vital to choose the right CRO for the job. Vial is a next generation, tech-enabled CRO reimagining clinical trials for the modern world. Vial has a powerful technology platform and an expert team of Clinical Operations (”Clin Ops”) leaders and scientific advisors with the proven experience to perform Phase 1 trials. Contact us today to discuss your trial needs and request a free quote.

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