Clinical trials

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What is a clinical trial?
Phases of clinical trials
How are trials conducted?
How are participants protected?
Why participate in trials?

What is a clinical trial?


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A clinical trial is a research study conducted in human volunteers to assess whether a new intervention is safe and effective for a specific condition. The intervention tested can either be a new drug, a device, a procedure or even changes to a participants’ behaviour (such as dieting). It is normally tested against a current standard treatment, a placebo (a drug that contains no active ingredients) or no intervention.

Clinical trials are conducted by a research team led by a principal investigator, who is usually an expert in the intervention and condition being studied. Funding of clinical trials can come from many different sources. These include pharmaceutical companies, academic medical centres, universities, voluntary groups, charities, federal organisations, individuals or a combination of the above.


Phases of clinical trials


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The difference between each phases of clinical trials.This is explained in the subsequent text.
Phases of clinical trials

Pre-clinical study

These are studies performed in the laboratory on animals or human cell models to find out if a particular drug or procedure is likely to be useful for a specific condition. The dosage and toxicity levels of the new treatment is studied in this phase.


Phase 1

Phase one trials allow the research team to establish the potential effects of the new treatment has on humans and its safety. It usually involves a small number of participants, with six to ten healthy volunteers or very sick patients who have limited treatment options.


Phase 2

Phase two trials are designed to evaluate the safety and efficacy of the new treatment at different dosages. It normally has more participants than phase one, with about 20 to 300 participants depending on the disease studied.


Phase 3

Phase three trials are used to confirm the safety and efficacy of the new treatment by conducting on larger number of participants than phase two. It usually involves about 300 to 3000 participants depending on the disease studied.


Phase 4

Phase four trials are also known as post-authorisation safety studies (PASS). This is conducted after the new treatment has received regulatory approval and being used in the clinical setting. It serves to evaluate the long term side-effects of the treatment and its real-world effectiveness.


How are trials conducted?


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In order to answer a specific research question(s), the team conducting the trial normally draws up a research plan, also known as a protocol early in the study design to outline how the study should be conducted and also to safeguard the wellbeing of participants. It usually contains the following:

  • Reason for conducting the study
  • Who can participate in the study, also known as the eligibility criteria
  • Location(s) of where the study is being conducted
  • Number of participants needed
  • Allocation of interventions for participants
  • Length of the study
  • Schedule of tests, procedures, or drugs and their dosages
  • Data that will be gathered from the participants (outcomes) and its collection method


Once the study protocol has been reviewed and approved by a regulatory body to make sure it is ethical, the research team then starts recruiting participants and conduct the trial according to the protocol. Adhering to a protocol ensures that the data gathered is robust and reliable.


How are participants protected?


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A member of the research team conducting the trial usually has a thorough discussion with potential participants, particularly outlining the risks and potential benefits of the study. This discussion also allows potential participants or their relatives to ask questions. Other materials about the study are provided to supplement the discussion. This process is called informed consent. Even if a consent form has been signed, it is not a binding contract and participants can withdraw from the study at any point.

Clinical trials involving a drug, biological product or medical device regulated by the US Food and Drug Administration (FDA) needs to be approved by an Institutional Review Board (IRB). The IRB is a group of people consisting of doctors, researchers and members of the public unrelated to the trial. The purpose of the IRB is to ensure that the study is ethical and the welfare of participants are protected.

Sometimes, clinical trials are also monitored by the Data and Safety Monitoring Boards (DSMBs) to review the progress of trials after commencement. Members of DSMBs are clinical trial experts and they evaluate if participants are safe, data collection is complete and whether the investigated treatment is working or not.


Why participate in trials?


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  • Contribute to medical knowledge
Results of trials can be used to inform the wider medical community about the effects, risks and benefits of a specific drug, procedure or any other interventions. It may stimulate further studies which could lead to discovery of a new treatment.
  • Access to cutting edge therapies
Most inherited eye disorders have limited or no treatment options. Participating in trials allow patients access to new therapies that could potentially be beneficial.
  • Receiving expert care
Research teams involved in clinical trials are normally led by experts in their respective fields. As researchers need to adhere to the trial protocols strictly, participants tend to have scheduled and more detailed follow-ups. However, this means that each follow-up appointment might be more time consuming than your standard clinic appointment.


Although there are benefits to participating in clinical trials, a word of warning is necessary. Certain studies might not have been evaluated by an ethics committee or given approval. If you are interested in joining a particular trial, it is important that you seek advice from your doctor on whether they think it is reputable and ethically approved.