Phase 3 Clinical Trials Explained

Phase 3 Clinical Trials Phase 3 Clinical Trials

Phase 3 Clinical Trials – Overview

Phase 3 clinical trials are the final phase for experimenting with a new drug to confirm the therapeutic effect observed in phase 2 clinical trials. It ensures that the drug is beneficial and safe and offers treatment for the intended indication.

Billions are spent to progress a drug to phase 3 trials, a vital phase from chemical to drug development. It focuses on efficacy and safety by collecting randomized control data on a larger number of patients with a given disease.

This phase involves choosing the experimental scheme, collecting undesirable effects, considering the risk-benefit ratio, and calculating the number of participants necessary to demonstrate certain efficiency in the pathology.

Phase 3 Clinical Trials - Key Takeaways

Phase 3 Clinical Trials – Introduction

Phase 3 Clinical Trials – Introduction

It is necessary to perform the widest trials as most phase 2 clinical trials ending with a positive result do not succeed in phase 3. It is often due to a lack of therapeutic efficacy or serious adverse effects.

Phase 3 trials are conducted to obtain additional information and verify the new drug’s effectiveness and safety to assess the risk/benefit ratio.

This information is used in the drug’s labeling once the FDA approves it. These trials involve large-scale studies and include several hundred to thousand patients.

Phase 3 trials are Randomized Control Trials (RCTs), where the participants receive the experimental drug or placebo randomly.

The trials ate double-blinded; neither the investigator nor the participant will know what the latter has received. The average duration of the trial ranges from one to four years.

Before the phase 3 trial, a substance is not considered a drug; however, it becomes a drug after getting positive results in phase 3 trials. It is then approved for registration and accepted by the concerned authorities. Based on valid arguments, it can be subsequently offered to prescribing physicians.

The Center for Drug Evaluation and Research (CDER), a division of the U.S. Food and Drug Administration (FDA), oversees these clinical trials.

CDER can bring a clinical on hold if the phase 3 trial design doesn’t meet its objectives or if a study is found unsafe.

Key Takeaways

  • Phase 3 trials are the final three-stage process of clinical drug trials before a new drug or device can be approved for public use.
  • These are randomized control trials, double-blinded, and involve large-scale participation, focusing on safety and efficacy.
  • Phase 3 trials are expensive and therefore have been blamed for high drug prices.

Phase 3 Clinical Trials – Methodological Bases

Phase 3 clinical trials are generally controlled with blind studies or random assignments between the control and treatment groups. It includes a sufficient number of patients. Though the modalities differ depending on the substance studies, the protocol must satisfy certain general demands.

  • Choice of scheme

The choice of the experimental scheme depends on factors such as the objectives of the study, stages in the study and the number of participants.

The correct evaluation of the effectiveness of the drug requires comparison. The experimental scheme allows this comparison among two or more groups of patients.

The participating patients are divided randomly into two groups who receive the planned treatment throughout the trial period.

  • Randomization

Randomization is necessary and is intended to reduce bias in the choice of drugs or treatments. In this method, a patient is given treatment by chance.

Randomized clinical trials have contributed immensely to advances in patient care and serve as the standard for research.

  • Blind Studies

Implementing a blind procedure is necessary as the efficacy of treatments can be assessed. It involves two procedures; a Simple blind procedure, where the patient is unaware if he/she belongs to the control or treatment group and a double-blind where the patient and the physician are both unaware.

  • Statistics

The statistical tests ensure that the differences observed are meaningful. The high comparison levels contribute to the probability of detecting a difference between treatments being maximal.

Phase 3 Clinical Trials – Key Elements

The several key points for phase 3 protocols include:

  • Inclusion Criteria

Want to participate in the trial? Well, the inclusion criteria define the requirements to enter the trial. If the criteria are too vague, the patient may comprise a heterogeneous group, making it difficult to interpret trial results, thus compromising the objectives of the study.

On the other hand, if the inclusion criteria are too restrictive, it becomes impossible to find a sufficient number of patients where the results become difficult to extrapolate.

Several trials are conducted, depending on the substances studied in phase 3. During each trial, a specific population can be studied.

  • Exclusion Criteria

Exclusion or non-inclusion criteria must be indicated to eliminate patients for whom the trial represents an excessive risk. It could also represent those who would make the group too heterogeneous or those whose follow-up is uncertain.

  • Evaluation Criteria

Evaluation or judgment criteria are fundamental to attain the objective of the study and must be chosen judiciously. It includes assessment tools and outcome measurements, evaluating the safety, efficacy, and tolerability of a new treatment.

  • Adverse Effects

Adverse or clinical and biological effects should be determined concerning possible symptoms.

  • Number of Subjects Required

The number of subjects required for the trial is decided before the trial begins and its length is also determined.

Phase 3 Trial – Associated Costs and Approval Process

Phase 3 trials are extremely expensive and it has been estimated at around $19 million. However, the costs may vary depending on the drug.

The drug development companies view the steep costs associated with Phase 3 trials as a necessary expense. The drug provides clinical benefits, and the successful completion raises the odds of obtaining marketing approval from the FDA for a new drug.

Drug Approval Process

Despite extensive testing, it can sometimes be difficult to evaluate the effectiveness of the drug. Clinical trials demonstrate if the drug is working or not; however, it does not indicate the reasons.

It is also possible that the subjects on which the drug is tested might be healthier than the patients who will be using the tested treatment.

After the phase 3 clinical trial, the New Drug Application (NDA) is the formal step and a comprehensive document defining the safety and efficacy of the new drug.

It includes data and analyses of the drug on animals and human body studies, the drug’s toxicology, pharmacology, dosage, and manufacturing process. NDA has to be submitted to the FDA for approval. Once approved, the new drug is then marketed in the U.S. market.

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Phase 3 Clinical Trials – Determining the Ultimate Efficacy, Safety & Dosage of Drugs


Phase 3 clinical trials are more intensive extensions of phase 1 and phase 2 clinical trials.

These trials determine the ultimate efficacy, safety and dosage of drugs after comparing the results. The dosage levels are modified according to the most beneficial effects while offering the least side effects.

See Also

Phase 4 Clinical Trials

Biomedical Research Grants

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