Things to Expect When Applying Clinical Trials

Published On: June 5th, 202311.4 min read

Clinical trials provide us with a pathway to progress in improved health outcomes for rare and complicated diseases, and offer us a way to test new treatments or find new avenues to prevent, diagnose, or manage existing diseases. But, clinical trials are also complex, costly, and time-consuming processes that involve many steps and challenges. In this post, we will explore how long clinical trials take, what factors influence clinical trial duration, and what you can expect if you apply to a clinical trial.

What’s The Timeline From Discovery to Full Approval?

When looking at how long do clinical trials take from the initial discovery of a novel therapy or drug, to its full-on approval by regulatory bodies, you can expect an average of 10-years. While this timeline may seem exceedingly long to participants, it is necessary to ensure that a product is safe and viable before it can be introduced into the market. The reason clinical trials take so long is that they must move through a series of 4 phases before it can be deemed successful, and these phases can take up 6–7 years of that 10-year timeline.

The Length of Time For Each Phase in a Clinical Trial

If you’re thinking about participating in a clinical trial, and want to know how long the clinical trial will take, this depends on the phase that the trial is in. Clinical trials are divided into 5 distinct phases, which have separate timelines and requirements that must be met before the next phase can begin.

How Long Does Pre-clinical Testing Take?

Before a new drug or treatment can be tested in humans, it has to undergo pre-clinical testing in laboratories and animals. This phase aims to evaluate the safety, efficacy, pharmacology, and toxicity of the drug or treatment, as well as to determine the optimal dose and delivery method. Pre-clinical testing can take anywhere from 1 to 6 years, depending on the type and complexity of the drug or treatment, the availability of animal models, and the regulatory guidelines.

How Long Are Phase 1 Clinical Trials?

Phase 1 clinical trials are the first stage of testing a new drug or treatment in humans. The main goal of this phase is to assess the safety and tolerability of the drug or treatment in a small group of healthy volunteers (usually 20 to 100). Phase 1 trials also measure how the drug or treatment is absorbed, metabolized, distributed, and excreted by the body, as well as its pharmacological effects and potential side effects. Phase 1 trials usually last from 1 to 4 months, but they can take longer if there are unexpected adverse events or dose adjustments.

The Length of Phase 2 Clinical Trials

Phase 2 clinical trials are designed to evaluate the efficacy and safety of the drug or treatment in a larger group of patients (usually 100 to 300) who have the condition that the drug or treatment is intended to treat. These trials also aim to determine the optimal dose and schedule of administration, as well as to identify any short-term side effects or risks. Phase 2 trials can last from several months up to the 2-year mark, depending on the number of patients enrolled, the type and severity of the condition, and the outcome measures used.

Phase 3 Clinical Trials

Phase 3 clinical trials are the most rigorous and extensive stage of testing a new drug or treatment in humans. The main objective of this phase is to compare the efficacy and safety of the drug or treatment with a standard or placebo treatment in a large group of patients (typically 300 to 3000) who have the condition that the treatment is intended to tackle. Phase 3 trials also aim to evaluate the long-term effects and benefits of the drug or treatment, as well as its impact on quality of life and cost-effectiveness. Phase 3 trials can take from 1 to 4 years or more, depending on the number of patients enrolled, the type and complexity of the condition, and the regulatory requirements.

FDA Approval After a Successful Phase 3

If the drug or treatment is deemed safe and effective in a Phase 3 clinical trial, the sponsor of the study (usually a pharmaceutical company) can submit a New Drug Application (NDA) to the Food and Drug Administration (FDA). The FDA will then review the NDA and make a decision about approving the drug or treatment for use in the general public.

Phase 4 Clinical Trials

Phase 4 clinical trials are conducted after a new drug or treatment has been approved by the regulatory authorities and marketed to the public. The purpose of this phase is to monitor the safety and effectiveness of the drug or treatment in a real-world setting, involving thousands or millions of patients who use it over a long period of time. Phase 4 trials also aim to discover any rare or long-term side effects or risks, as well as any new indications or benefits of the drug or treatment. Phase 4 trials can last for several years, or even decades, depending on the type and frequency of adverse events reported, as well as any changes in clinical practice or guidelines.

How Long Do Clinical Trials Take For Those Choosing to Participate?

While a clinical trial may take numerous years to complete, this doesn’t mean that the participant’s involvement will be that long. In fact, most studies only require a few visits to the study site over the course of the trial. These visits may involve physical exams, blood tests, questionnaires, or other procedures to monitor the safety and effectiveness of the intervention.

In between the visits, participants may be asked to keep a diary or log of their symptoms, medication use, or any other relevant information. This helps the researchers to collect accurate and reliable data from the participants. The study team will also contact the participants regularly to check on their health and well-being.

Another common question that potential participants may have is whether they can withdraw from a clinical trial once they enroll. The answer is yes, they can. Participation in a clinical trial is always voluntary and participants can decide to stop at any time, for any reason. They do not have to give a reason or justify their decision to anyone. However, it is important to inform the study team before withdrawing so that they can provide any necessary follow-up care and advice.

Sometimes, a clinical trial may also end earlier than planned. This may happen if the researchers find that the intervention is either very effective or very ineffective, or if there are safety issues or ethical concerns. In such cases, the participants will be notified and informed of the reasons for stopping the trial.

What Factors Influence How Long Clinical Trials Take?

There are a number of factors that can affect the duration of a clinical trial. These include:

1. Trial Complexity. The complexity of a given treatment has a large impact on the duration of the trial because more complex treatments generally require longer observation periods to ensure accurate results. If a treatment must go through animal testing before it can be tested on humans, this will also add significant time to the process. For these reasons, many simple medications that don't necessarily need extensive testing can move through clinical trials much faster than more complicated treatments.

One way to reduce trial complexity is to use adaptive designs, which allow researchers to modify certain aspects of the trial based on interim data. This can help optimize the trial efficiency and reduce unnecessary costs and risks.

2. Trial Scope. The size and scope of a study also play an important role in how long it takes to complete. A small-scale local study with only 30 participants may take only one or two months to complete, while larger studies involving thousands of subjects across multiple locations may take years. Moreover, if new medications must be manufactured for use in a trial—which is often necessary—that adds yet another variable that affects the timeline.

One way to reduce trial scope is to use online platforms and digital tools that can facilitate recruitment, data collection, and communication among researchers and participants. This can help streamline the trial process and reduce logistical challenges.

3. The Condition Being Studied. The type and severity of the condition being studied can also impact how long a clinical trial takes. Some conditions are more common and easier to diagnose than others, which means finding eligible participants may be faster and simpler. Some conditions are also more stable and predictable than others, which means measuring the outcomes may be more straightforward and reliable.

One way to reduce the impact of the condition being studied is to use biomarkers, which are measurable indicators of biological processes or responses. Biomarkers can help researchers assess the efficacy and safety of a treatment more quickly and accurately than clinical endpoints, which are observable changes in health status or symptoms.

4. The Trial Design. The trial design refers to how a study is structured and conducted. It includes aspects such as the number and type of groups, the randomization method, the intervention protocol, the outcome measures, and the statistical analysis plan. The trial design can have a significant influence on how long a clinical trial takes because it determines how many participants are needed, how often they are assessed, and how the data are interpreted.

One way to reduce trial design issues is to use standardized protocols and guidelines that have been validated by experts and regulators. This can help ensure that the trial design is appropriate for the research question and meets the ethical and scientific standards

5. The Regulatory Requirements. The regulatory requirements refer to the rules and regulations that govern clinical trials in different countries and regions. They include aspects such as the approval process, the informed consent procedure, the data protection policy, and the reporting obligations. The regulatory requirements can affect how long a clinical trial takes because they determine what steps must be taken before, during, and after a trial to ensure its quality and validity.

One way to reduce regulatory hurdles is to use harmonized frameworks and procedures that facilitate cross-border collaboration and coordination among researchers and regulators. This can help reduce duplication of efforts and speed up the approval process.

6. Any Logistical Challenges. The logistical challenges refer to any practical difficulties or obstacles that may arise during a clinical trial. They include aspects such as finding suitable sites, securing adequate resources, managing staff turnover, handling unexpected events, and maintaining participant retention. The logistical challenges can influence how long a clinical trial takes because they can cause delays or disruptions in the trial execution.

One way to reduce logistical challenges is to use contingency plans and risk management strategies that anticipate potential problems and prepare solutions in advance. This can help minimize the impact of unforeseen circumstances and ensure continuity of operations.

7. Ethical Considerations. The ethical considerations refer to any moral or ethical issues that may arise during a clinical trial. They include aspects such as ensuring participant safety, respecting participant autonomy, protecting participant confidentiality, avoiding conflicts of interest, and ensuring social justice. The ethical considerations can affect how long a clinical trial takes because they require careful deliberation and consultation among researchers, participants, regulators, and other stakeholders.

One way to reduce ethical issues is to use a structured approach that involves transparent communication, meaningful dialogue, and informed decision-making. This can help promote mutual understanding and trust between researchers and participants, which is essential for successful clinical trials.

What to Expect If You Apply to Participate in a Clinical Trial

If you are considering participating in a clinical trial, and are wondering how long a specific clinical trial study will take, the timeframe should be posted on the listing. If it is not, a patient care coordinator will tell you how long it will last when you complete the informed consent process during your application to participate. You can expect the following when applying:

  • To be considered for a trial, potential participants must meet the eligibility criteria for that particular trial. These criteria may include age, gender, medical history, current medications, disease stage and more. To determine if you are eligible for a clinical trial, you need to undergo screening tests.
  • Before participating in a clinical trial it is important to read and understand the details of the informed consent form which explains the purpose, procedures, risks, benefits, alternatives, and responsibilities of taking part in the trial. If anything is unclear, or you have concerns, make sure to ask questions before signing the form.
  • When joining a trial, it is possible that you will be randomly assigned to receive either the new treatment being tested or a standard treatment or placebo (in which case you would not know which one you have been given). This helps prevent bias when evaluating outcomes from different treatments.
  • Once taking part in a clinical trial, you will need to follow instructions from research teams in regard to taking medication/treatment or undergoing tests/procedures and reporting any symptoms or side effects that occur. It's also essential to keep in touch with them throughout and after the trail ends.
  • You can withdraw from the clinical trial process at any time.


Clinical trials are vital for advancing medical science and improving human health. However, they are also lengthy and challenging processes that require careful planning, execution, analysis, and reporting. This is why the answers to “how long do clinical trials take,” can vary so widely depending on the type of treatment, the design of the trial, the recruitment of participants, and regulatory standards and approvals. If you have any questions about in our clinical studies, please contact us by phone at: 407-916-0060 or by emailing us at:

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Conquest Research is continuously looking for participants to take part in clinical research trials for various medical conditions.