15 December 2022

Check Up #10 - Clinical Trials

Clinical Trials have phases. What distinguishes them from one another?

Check Up #10 - Clinical Trials have phases. What distinguishes them from one another?

In the case of cancer (as in other diseases) any research study involving human volunteers that is intended to acquire medical knowledge about a potential new drug, vaccine or biological substance against a specific type of cancer – in which these are administered to a group of participants – is called a clinical trial.

Before any clinical trial can be approved by the competent health authorities (the Food and Drug Administration in the US, the INFARMED and the CEIC - Comissão de Ética para a Investigação Clínica in Portugal, for instance), preclinical research on the effect of the potential cancer drug must be performed on animal models and yield promising results. This research stage typically takes three to five years to complete.

But there is no guarantee that the experimental substance will work, let alone be safe, to use in humans. That’s what clinical trials are precisely for: to assess the cancer drug’s safety and efficacy in human beings.  

A clinical trial is characterised by its “phase”, which determines things like their goal, the number of participants enrolled in it, etc. Typically, there are four phases to a clinical trial: Phase 1, Phase 2, Phase 3, and Phase 4. To be ultimately approved, a candidate drug must go through all these phases, in that order. Sometimes, there is even a more preliminary phase, called Early Phase 1 (or, formerly, Phase 0). This clinical development stage normally takes three to ten years to complete.

A phase 1 clinical trial focuses on the safety of an experimental cancer drug. It involves a small number of healthy volunteers (20 to 100) and aims to determine the drug's dosage and its most frequent and serious side effects. 

A phase 2 clinical trial gathers preliminary data on whether the drug works (is effective) in people who have the type of cancer the drug is supposed to treat (100 to 500 patients). Here, participants receiving the drug may be compared to similar participants receiving an inactive substance (called a placebo) or a more conventional therapy. Safety and adverse side effects continue to be monitored.

A phase 3 clinical trial, which involves more participants (3,000 to 5,000 patients), aims to gather more data about the cancer drug's safety and effectiveness, in particular by studying different populations and different dosages, and by using the experimental drug in combination with other drugs.

A phase 4 clinical trial is a trial that takes place after the cancer drug has been approved, in order to monitor its correct use following the drug’s commercial launch. Its aim is to gather still more data about the drug's safety, effectiveness, optimal use, etc. 

Lastly, an Early Phase 1 clinical trial is an exploratory trial conducted before the traditional phase 1 trial. It aims to study how a cancer drug affects the body. It involves a very small group and minimal exposure to the drug.

There have been thousands of clinical trials conducted in the European Union alone, and many more worldwide. A recent search on the EU Clinical Trials Register (https://www.clinicaltrialsregister.eu) , which lists EU clinical trials, yielded 10,214 results for the keyword “cancer”, 1,792 results found for “breast cancer”, and 1,585 result found for “lung cancer”. And an equally recent search in US Clinical Trials Register (https://clinicaltrials.gov/), which lists clinical trials by country at all their stages (from “not yet recruiting” to “completed”), returned 140 clinical trials with Portuguese participation for the keyword “breast cancer”: 1 of which – by the Champalimaud Foundation – “not yet recruiting”;  24 “recruiting”; 31 “active, not recruiting” (i.e. ongoing); and 64 “completed”.



By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.
Reviewed by: Professor António Parreira, Clinical Director of the Champalimaud Clinical Center.
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