Designing Clinical Trials and Its Phases

Designing Clinical Trials and Its Phases: Clinical research is generally classified into two district types such as experimental studies and observational studies (Fig). The basic concept of experimental study design is to study the effect of an intervention. In the experimental study, the risk factor/exposure of interest/ treatment is controlled by the investigator. Observational research does not attempt to intervene in the study sample for exclusively investigational purposes. Observational study types include wide ranges from traditional epidemiologic cohort and case-control studies to quasi-experimental time series methods. Observational research can also be classified as retrospective or prospective concerning the perspective of the investigator. All experimental research by nature is prospective.

Designing Clinical Trials and Its Phases
Fig: Classification of Clinical or Analytical Study Designs

Regardless of study design, results can only be inferred to the population if they are internally valid and bias, confounding, and chance can be reasonably minimized. Clinical research involves analyzing the association between two or more variables. Variables are classified as dependent (outcome) variables and independent (predictor) variables. Chance is the likelihood that the studied observation is the result of random variation. The role of chance in research is quantified through statistical tests (inferential statistics). Blouses are generally classified as selection bias and information bias Selection biases occur when subjects are selected for a study in a way that creates a false association. Information bias occurs when the method of data collection is systematically different between study groups. Confounding occurs when the study association is partially or entirely mediated by a third factor. Confounding is classically depicted as the interplay among three variables as A. B and C Where A is the exposure of interest. B is the outcome and is the potential confounder. Control of confounding is important in observational research, but it may also be problematic in non-randomized, experimental research. It can be analytically managed and adjusted for using different design strategies. The most useful method for controlling confounding in experimental research is randomization.

Clinical trials are essential to test the safety and efficacy of new treatments in any population. Well-designed randomized controlled trials (RCTs) are the most important for testing the efficacy and safety of any new formulation. All clinical trials investigating a new drug or formulation require approval from the CDSCO (Central Drugs Standard Control Organisation). The CDSCO is headed by the Drugs Controller General of India (DCGI). The clinical trials process for gaining regulatory approval of a new molecule has been described in four phases. Each phase seeks to answer a different set of questions. Every phase added more volunteers to prove that experimental molecule or treatment is safe and effective against a particular disease.

Phase I Trials: The researcher test the new drugs in a small group of people (20-80) for the first time to evaluate a safe dosage range and identify side effects.

Phase II Trials: These trials are carried out in a larger group of people (100-300) to determine whether a drug is effective and further evaluate its safety. These trials are specifically designed to assess dosing requirements, therapeutic dose range, and any adverse effects.

Phase III Trials: These trials are conducted on larger populations (1.000-3,000) and in different regions and countries. Phase III trials are designed to study the risk-benefit profile of an experimental drug or formulation. Such trials may perform by using the different routes of administration and different doses of the standard drug against the standard regimen. These trials are the last phase in the preapproval process and it is called pivotal trials.

Phase IV or Post-Marketing Trials: These trials are conducted after approval of the drug by the appropriate agency. It provides additional evidence on the risks and benefits of the new drug molecules or obtains more information on its side effects and safety.

All these trials are carried out in different locations, hospitals, clinics, university health centers, or community health centers. Every clinical trial has a strictly defined protocol that is approved by the Institutional Review Board (RB) consisting of physicians, statisticians, patient advocates, researchers, etc. The main function of IRB is to ensure that the trial is ethical, legal and that the rights of those participating are fully protected.

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