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Clinical trials

Clinical Trials

A clinical trial is a research study, where a new drug or treatment is tested on people to assess its benefits and risks.

All new treatments have to go through trials to ensure they are safe and tolerable, and to test whether they are better than existing treatments.

People choose to take part in a clinical trial because they want to contribute to finding new ways of treating health problems, or because they may benefit from a new treatment themselves.

There are pros and cons to being involved in a clinical trial. Think about your options carefully and discuss them with others.

What is a clinical trial?

A clinical trial is a research study, testing a new drug or treatment on people to find out about its benefits and risks.

A trial will try to find out if the new treatment is:

  • safe
  • free from major side-effects
  • better than any existing treatments.

Developed in partnership with NAM

  1. Background
  2. Research
  3. Joining
  4. Pros and cons


In the UK, research and clinical trials are part of the work of the NHS. The people who do research are often the same doctors and other health professionals who provide treatment.

This research will often take place in hospitals or clinics. Research also takes place in universities and research institutes, in social care services, or in the private sector (for example if it is undertaken by a pharmaceutical company).

There are legal requirements on how a trial should be run.

An organisation called the Medicines and Healthcare Products Regulatory Agency (MHRA) needs to review and approve every trial, which must also be approved by local ethics committees.

There are different types of trials, depending on the research methods used, and different stages, or ‘phases’, depending on how far research has gone into a new treatment or drug.

All trials have what is called a protocol. This sets out the trial's aims and objectives.

Trials also have rules about who can and cannot join. These are called inclusion and exclusion criteria. Often, for example, women who are pregnant or who want to become pregnant cannot join a clinical trial.

You can find more information on clinical trials, and on making the decision whether or not to join one, on the NHS Choices website. The UK Clinical Research Collaboration can also provide you with more information about taking part in a clinical trial.


What sort of clinical trials look at HIV treatment and prevention?

Current clinical trials for people with HIV are looking at some key areas of HIV treatment and prevention:

  • Attacking HIV at different stages of its lifecycle in order to stop or delay it damaging the immune system. This is how anti-HIV drugs in different classes are explored and developed.
  • Lessening side-effects.
  • Studying drug interactions.
  • Curing other conditions often seen in people with HIV, such as diabetes, hepatitis or tuberculosis.
  • Managing treatment and healthy living.
  • Preventing HIV - for example the development of pre-exposure prophylaxis (PrEP) and the ongoing attempt to develop a vaccine.

What have we learnt from HIV clinical trials?

Major advances in HIV therapy have been made as a result of clinical trials. For example, we know more about choosing anti-HIV drugs and how and when treatment should be taken from the findings of trials:

  • The PARTNER study found that people who are taking treatment and have an undetectable viral load cannot pass on HIV.
  • The Partners PrEP study found that there remains a transmission risk within the first six months of treatment as the HIV positive partner's viral load takes time to come down.
  • HIV treatment is generally most effective if it consists of three anti-HIV drugs. Clinical trials can help guide the choice of which combination of anti-HIV drugs will work best.
  • The current recommendation that everyone with HIV should start treatment regardless of their CD4 count is based on the results of a clinical trial. The START study found that people who waited to start treatment until their CD4 count dropped to 350 (which is when people were previously advised to start) had a much higher chance of developing AIDS-related illnesses such as cancers.
  • Having a break from HIV treatment makes people more likely to become unwell, compared to people who stay on treatment all the time (the SMART trial).
  • A 1994 trial called ACTG 076 found that Zidovudine treatment during pregnancy, labour and the baby’s first weeks of life can reduce the risk of HIV transmission from mother to child by two-thirds. This was groundbreaking at the time.  

Clinical trials have also shown how to best manage other conditions that are common in patients with HIV, such as hepatitis.


How can I join an HIV clinical trial?

Staff at your clinic may know about trials that are being carried out. You could ask your doctor or nurse about any research happening that might be appropriate for you to join.

There are also several registers, or lists, of trials going on at any time. You could ask at your clinic about how to find these.

UK CAB, an HIV advocacy organisation, also has information on how to find clinical trials and has listings of current trials.

If you hear of or read about a trial that interests you, the first step is to talk to the trial's contact person. They should give you some information about it.

The staff at the trial centre will usually ask you some questions to check that you meet the basic entry requirements for the trial, and you may have a physical examination and a blood test.

After the results of all the tests are available, the trial staff will let you know whether or not you are eligible to take part.

It does not necessarily matter if you are currently receiving treatment at a different clinic or hospital to where the trial is being carried out. But you should be sure to tell your regular doctor if you do join a trial at a different centre. You may also want to discuss whether or not to join a trial with your doctor or another member of your clinic team.

What should I consider before joining a trial?

New research cannot lead to reliable findings unless people agree to take part and, by joining a trial, you can contribute to important medical research. But it’s important to think carefully before deciding.

You can find out more about recent research into HIV prevention, treatment and care on www.aidsmap.com

You can find more information on clinical trials, and on deciding whether or not to join one, at the NHS Choices website and from the UK Clinical Research Network.

Pros and cons

There is no right or wrong time to join a trial. Decide if you want to join in close consultation with your healthcare team and give yourself time to ask questions.

Reasons to join a trial:

  • Access to new drugs, or to new forms of treatment, which may be more effective than existing ones.
  • More frequent monitoring and access to the most advanced tests.
  • The findings of the research may benefit other people with HIV.
  • You may receive a small payment, although this is not very common – sometimes patients receive cash compensation or travel expenses for participating in a study.

Reasons not to join a trial:

  • The outcome or effectiveness is not yet known.
  • You already know which treatment you want to take.
  • You don't want to take the chance of being given a placebo (‘dummy’ pill, usually made of sugar).
  • It often involves many hospital or clinic appointments.
  • The pill-taking timetable, or restrictions on your daily life, don’t feel manageable.
  • Possible unknown side-effects.
  • You are pregnant, or want to be, or don't want to use contraception (if required by the study).

You will also need to consider your own motivation for taking part in a trial, and what you will need to take into account.

  • Can you commit to taking the treatment as required?
  • Can you commit to attending all the appointments involved?
  • Can you meet any other requirements of the trial?
  • Do you have support from friends or family if needed?
  • Do you agree with the trial’s design and requirements?

You can find more information on clinical trials, and on deciding whether or not to join one, at UK CAB, on the NHS Choices website, and in resources provided by the UK Clinical Research Collaboration.

‹‹ Back to: Generic HIV therapy



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The Information Standard: Certified member

This article was last reviewed on 20/11/2015 by Anna Peters

Date due for the next review: 20/11/2018

Content Author: Kerri Virani

Current Owner: Kerri Virani

More information:

HIV Transmission Risk Persists During the First 6 Months of Antiretroviral Therapy, Mujugira A1, Celum C, Coombs RW, Campbell JD, Ndase P, Ronald A, Were E, Bukusi EA, Mugo N, Kiarie J, Baeten JM; Partners PrEP Study Team
National Center for Biotechnology Information
US National Library of Medicine
2016 Aug 15;72(5):579-84. doi: 10.1097/QAI.0000000000001019

HIV treatment as prevention and HPTN 052, Cohen MS1, McCauley M, Gamble TR
National Center for Boiotechnology Information
US National Library of Medicine

Sexual Activity Without Condoms and Risk of HIV Transmission in Serodifferent Couples When the HIV-Positive Partner Is Using Suppressive Antiretroviral Therapy, Journal of the American Medical Association: Alison J. Rodger, MD; Valentina Cambiano, PhD; Tina Bruun, RN; Pietro Vernazza, MD; Simon Collins; Jan van Lunzen, PhD; Giulio Maria Corbelli; Vicente Estrada, MD; Anna Maria Geretti, MD; Apostolos Beloukas, PhD; David Asboe, FRCP; Pompeyo Viciana, MD1; Félix Gutiérrez, MD; Bonaventura Clotet, PhD; Christian Pradier, MD; Jan Gerstoft, MD; Rainer Weber, MD; Katarina Westling, MD; Gilles Wandeler, MD; Jan M. Prins, PhD; Armin Rieger, MD; Marcel Stoeckle, MD; Tim Kümmerle, PhD; Teresa Bini, MD; Adriana Ammassari, MD; Richard Gilson, MD; Ivanka Krznaric, PhD; Matti Ristola, PhD; Robert Zangerle, MD; Pia Handberg, RN; Antonio Antela, PhD; Sris Allan, FRCP; Andrew N. Phillips, PhD; Jens Lundgren, MD
JAMA. 2016;316(2):171-181. doi:10.1001/jama.2016.5148

START trial finds that early treatment improves outcomes for people with HIV, Gus Cairns, NAM, 27 May 2015

The HPTN 052 Study, NAM

NHS Choices Clinical trials and medical research - Joining a trial 14 January 2013


National Institute for Health Research Understanding clinical trials October 2010


NHS Choices Clinical trials for HIV


UK-CAB Is a clinical trial right for me? 20 January 2011