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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.

A trial will try to find out:

  • if the treatment is safe
  • if the treatment has any side-effects
  • if the new treatment is better than any existing treatments.

Developed in partnership with NAM

  1. Background
  2. Research
  3. Joining
  4. Things to consider


People choose to take part in clinical trials because this research helps doctors understand more about a disease or condition, which may benefit them or others like them in the future.

In the UK, research and clinical trials are part of the NHS’s work. 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 (such as 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 how far research has got 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 and in Understanding Clinical Trials. The UK Clinical Research Collaboration can also provide you with more information about taking part in a clinical trial.


Clinical trials for people with HIV currently taking place are looking at six key areas of HIV treatment and prevention:

  • Treatments to attack HIV at different stages of its lifecycle in order to stop or delay it damaging the immune system. This is how drugs in different classes of anti-HIV drugs are explored and developed.
  • Treatments intended to strengthen the immune system.
  • Treatments for side-effects, such as lipodystrophy.
  • Treatments for other conditions often seen in people with HIV, such as hepatitis or tuberculosis.
  • Prevention, screening and treatment for sexually transmitted infections and anal and cervical cancer.
  • Methods of preventing HIV, such as a vaccine.

Major advances in HIV therapy have been made as the 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:

  • 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.
  • Having a break from HIV treatment makes people more likely to become unwell, compared to people who stay on treatment all the time.
  • AZT 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.
  • The current recommendation that people should start HIV treatment when their CD4 cell count is around 350 is based on the results of a clinical trial. A large study (called START) is currently underway to get a more detailed understanding of the best time to start HIV treatment.

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

Research is also looking at ways of preventing sexual HIV transmission, through the use of anti-HIV drugs as pre-exposure prophylaxis (PrEP) and in microbicides. The HPTN 052 study showed that being on effective HIV treatment makes it 96% less likely someone will pass HIV on to their sexual partner.


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 the trial.

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.

Deciding to join 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 about joining a trial.

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 making the decision whether or not to join one, at the NHS Choices website and in Understanding Clinical Trials, from the UK Clinical Research Collaboration.

Things to consider

There is no right or wrong time to join a trial. People join trials at different times and for different reasons. It is something that is best decided in close consultation with your healthcare team and it is worth taking plenty of time to think carefully about your treatment options, and to ask questions, before deciding whether joining a trial is the best option for you.

Reasons to join a trial

  • You may have access to new drugs, or to new forms of treatment, which may be more effective than existing ones.
  • You will receive more frequent monitoring and have 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 for participating in a study or travel expenses.

Reasons not to join a trial

  • You are concerned about being on a treatment where 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).
  • It would involve too many hospital or clinic appointments for you.
  • The pill-taking timetable, or restrictions on your daily life, don’t feel manageable.
  • You are worried about possible unknown side-effects.
  • You are pregnant, or want to be, or don't want to use the form of contraception 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 making the decision whether or not to join one, at UK CAB ; on the NHS Choices website ; and in resources provided by the UK Clinical Research Collaboration.


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The Information Standard: Certified member

This article was last reviewed on 30/9/2012 by T. Kelaart

Date due for the next review: 30/9/2014

Content Author: S. Corkery, NAM

Current Owner: S. Corkery, NAM

More information:

Delta Coordinating Committee Delta: a randomised double-blind placebo-controlled trial comparing combinations of zidovudine plus didanosine or zalcitabine with zidovudine alone in HIV-infected individuals. Lancet 348: 283-291, 1996

Hammer S et al. A trial comparing nucleoside monotherapy with combination therapy in HIV-infected adults with CD4 cell counts from 200 - 500 per cubic millimeter. AIDS Clinical Trials Group Study 175 Study Team. N Engl J Med 335: 1081-1090, 1996

Strategies for Management of Antiretroviral Therapy (SMART) Study Group. CD4+ count-guided interruption of antiretroviral treatment. N Engl J Med. 355: 2283-2296, 2006

ACTG 320 trial halted as three-drug arm proves superior. AIDS Patient Care STDS. 1997 Jun;11(3):194.

Connor EM et al. Reduction of maternal-infant transmission of human immunodeficiency virus type 1 with zidovudine treatment. N Engl J Med 331: 1173-1180, 1994

Cohen M et al. Antiretroviral treatment to prevent the sexual transmission of HIV-1: results from the HPTN 052 multinational randomized controlled ART. Sixth International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, Rome, abstract MOAX0102, 2011. View abstract on conference website here: http://pag.ias2011.org/abstracts.aspx?aid=4735

NHS Choices website at http://www.nhs.uk/Conditions/Clinical-trials/Pages/Takingpart.aspx

UK Clinical Research Collaboration

MHRA website – guidance on clinical trials for medicinal products: http://www.mhra.gov.uk/Howweregulate/Medicines/Licensingofmedicines/Clinicaltrials/index.htm

NIHR: Understanding clinical trials: http://www.crncc.nihr.ac.uk/NR/rdonlyres/05551C09-441F-4C16-B180-8B39F3E62612/0/UnderstandingClinicalTrialsBookletcrystalmark.pdf

UK CAB http://www.ukcab.net/resources/clinical-trials/trial-right-for-me/