A clinical trial is a term used to refer to scientific research that is carried out to verify the efficacy and safety of new drugs, vaccines, diagnoses, or therapeutic procedures. They are normally designed by researchers, whether doctors or other health specialists, who are experts in diagnosing and treating a particular disease and they are carried out considering a series of national and international ethical and legal standards and following the provisions of a protocol, which must be strictly followed until the end of the trial. Additionally, the design and execution of these trials are submitted to the health authorities for evaluation and approval to ensure the study’s quality and safety. Generally, each country has one specialized authority dedicated to this matter.
These kind of trials and other similar clinical research studies are essential for the use and commercialization of a new product or treatment to be approved by the regulatory authorities around the world.
According to the International Conference on Harmonization (ICH), an international project for the harmonization of technical requirements for the registration of products for human use, clinical trials must be aimed at verifying the following elements of the product under investigation:
- The clinical, pharmacological, and pharmacodynamic effects
- Any adverse reaction
- Absorption, distribution, metabolism, and excretion of an investigational product
- Efficacy for a timely therapeutic, prophylactic, or diagnostic indication
In this way, the execution of clinical trials is fundamental to guarantee that the new products under investigation are genuinely effective for the prevention, diagnosis, and treatment of diseases, which ultimately positively impacts the quality of life and the general well-being of the population.
Part of the international scientific community considers that the first clinical trial was developed in 1747 by the British navy surgeon, James Lind, to find out the best treatment for scurvy, a disease resulting from a lack of vitamin C. In fact, Every May 20 is celebrated on International Clinical Trial Day to commemorate this date. However, it was not until 1931 that the Lancet magazine publicly recognized the term “clinical trial” when referring to the creation of a Clinical Trials Committee by the UK Medical Research Council.
Some years later, Sir Austin Bradford Hill, considered nowadays as the father of the modern clinical trial, published the first book on the subject, “Principles of Medical Statistics”. The first controlled clinical trial was carried out in 1946 to test the efficacy of streptomycin as a treatment for tuberculosis. Years later, the rest of the currently known clinical trials were introduced as investigative practices.
There are different types of clinical trials according to various classifications. Depending on the type of product to be investigated, one or another type of test is chosen for each of the phases of the investigation.
- Uncontrolled trials: There are no control groups. The results of efficacy or toxicity are compared with those obtained in previous trials.
- Controlled trials: There are control groups to which a placebo or another type of treatment is applied and with which the study groups are compared.
- Non-randomized trials: The investigator places each of the study participants into treatment or control groups.
- Randomized trials: Participants are assigned randomly using different tools that guarantee confidentiality.
- Open trials: Investigators know to which group the patients participating in the trial have been assigned, which may inadvertently influence the results.
- Blind trials: The participants or they and the investigators do not know to which groups the participants have been assigned. Single-blind trials are those trials in which the investigators know the allocation of the participants. In contrast, trials in which neither the participants nor the investigators know the distribution are designated double-blind trials.
- Superiority trials: The aim is to demonstrate that the product under investigation is better than the one used as a control or reference.
- Bioequivalence trials: These trials aim to demonstrate that the result obtained with the drug is neither better nor worse than that used as a control.
- In non-inferiority trials: These investigations are carried out to corroborate that the drug is not the one used as a reference.
- Parallel trials: There are several groups of patients, and each receives a single treatment. It is used for comparative trials.
- Crossover trials: Each one of the patients receives all the treatments involved in the trials.
- Sequential trials: Patients enter the study in pairs, one is assigned to the experimental group and one to the control group, and the results are analyzed cumulatively.
In general, clinical trials are developed through research stages or phases that can last up to around ten years. Several research phases are involved in this process, which are divided into preclinical and clinical phases. The clinical stage is divided, in turn, into four different phases (phases I-IV).
It constitutes the first step in the investigation of a product in man. In this phase, pharmacokinetic and pharmacodynamic trials are developed to assess tolerance preliminarily, evidence of pharmacological actions, ranges, dosage, absorption, distribution, metabolism, and excretion of the product. During this phase, the first tests are carried out on humans, who are generally entirely healthy.
It analyzes the treatment effect and is also used to determine the appropriate dosage range. It is carried out with a limited number of patients who suffer from the disease that it is intended to combat or is at risk of doing so with the objectives of studying a specific biological activity, control, or disease prevention.
These are usually randomized controlled clinical trials of treatments. The inclusion and exclusion criteria are strict.
In the first stage, the efficacy results are analyzed. Then new studies are designed to definitively assess the safety and usefulness of the product, which requires rigorous supervision of the patients involved. The development of phase III will largely depend on the results obtained.
It is carried out to assess the efficacy and safety of the new product under conditions similar to those that can be expected when it is on the market and considering the therapeutic alternatives available in the medication studied. In studies of this type, the product is compared with pre-established standard treatments to confirm evidence of relative efficacy.
These studies support the authorization of the registration and commercialization of a drug at a specific dose and indication. Hence, they must be controlled (if possible double-blind) and randomized, including sufficient patients to demonstrate the comparative efficacy and safety between the treatments under study.
They are carried out with marketed drugs to carry out their pharmacovigilance of the product, a process that includes detecting long-term side effects and possible effects on the pathology itself; or morbidity and mortality studies. New product indications, new formulations, dosage forms, or the comparison with other already known drugs are also studied.
Individuals have different motivations for participating in clinical trials. Some want to follow the latest treatments because they hope they will be more effective than the current standard. Others join out of a desire to contribute to science or to receive money. And others, for their part, may wish to have free access to medicines and medical care.
Whatever the reason for participating in a clinical trial, doing so is an excellent opportunity. However, people involved in this research must do so consciously and consider the risks and benefits that this implies.
Likewise, you must know that, in any clinical trial, the participants have the obligation and the right to sign an informed consent after clarifying with the researcher all doubts and questions regarding the process and to declare that their participation is voluntary and that you can leave it at any time you want without having to give explanations and without this decision affecting your future medical care.
In this way, we come to the end of this post, which we have been dedicated to discover the different types of clinical trials that exist and are used to evaluate novel biopharmaceutical products, So now you know what you can expect from each of them, if you dare to participate.