What is an investigational drug?
An investigational drug is one that is under study and is not approved by the U.S. Food and Drug Administration (FDA) for sale in the United States. Medical research studies are conducted to evaluate the safety and effectiveness of an investigational drug. These research studies are also called clinical trials. Once an investigational drug has been proven safe and effective in clinical trials, FDA may approve the drug for sale in the United States.
What is lersivirine?
Lersivirine is an investigational drug that is being studied for the treatment of HIV infection.
Lersivirine belongs to a class (group) of HIV drugs called non-nucleoside reverse transcriptase inhibitors (NNRTIs).2
NNRTIs attach to and block an HIV enzyme called reverse transcriptase. (An enzyme is a protein that starts or increases the speed of a chemical reaction.) By blocking reverse transcriptase, NNRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body.
Lersivirine appears to work on certain HIV strains against which other NNRTIs no longer work.4
How are clinical trials of investigational drugs conducted?
Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.5
- Phase I trials: Researchers test an investigational drug in a small group of people (20–80) for the first time. The purpose is to evaluate its safety and identify side effects.
- Phase II trials: The investigational drug is administered to a larger group of people (100–300) to determine its effectiveness and to further evaluate its safety.
- Phase III trials: The investigational drug is administered to large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatments, and collect information that will allow the investigational drug to be used safely.5
In most cases, an investigational drug must be proven safe and effective in a Phase III clinical trial to be considered for approval by the FDA for sale in the United States. Some drugs go through the FDA’s accelerated approval process and are approved before a Phase III clinical trial is complete. After a drug is approved by the FDA and made available to the public, researchers track its safety in Phase IV trials to seek more information about the drug’s risks, benefits, and optimal use.5
In what phase of testing is lersivirine?
Lersivirine has been studied in several Phase II clinical trials.2
The clinical development of lersivirine for the treatment of HIV infection was discontinued in February 2013.3
What have recent studies shown about lersivirine?
In a Phase IIb study, two different doses of lersivirine taken once daily were compared with the FDA-approved NNRTI efavirenz (brand name: Sustiva) taken once daily in HIV-infected participants. The participants had never taken HIV medicines before entering the study (treatment-naive). Study participants, whether given lersivirine or efavirenz, also received other HIV medicines as part of their background regimens. (A background regimen is a combination of drugs that are not being studied as the investigational drug[s] in the clinical trial, but are being given to help control a participant’s HIV infection.)6
In this study, both doses of lersivirine proved as effective as efavirenz. In terms of safety, lersivirine and efavirenz had differences. Fewer severe side effects and fewer incidents of rash occurred with the use of lersivirine than with the use of efavirenz. The most common side effects that occurred in patients taking lersivirine were nausea and headache.6
What side effects might lersivirine cause?
In the Phase IIb study discussed under the previous question, the most common side effects associated with lersivirine use after 48 weeks of treatment were nausea and headache. Rash was also reported, but it was not a common occurrence associated with lersivirine.6
Because lersivirine is still being studied, information on possible side effects of the drug is not complete. As testing of lersivirine continues, additional information on possible side effects will be gathered.
Where can I get more information about clinical trials studying lersivirine?
More information about lersivirine-related research studies
is available from the AIDSinfo
database of ClinicalTrials.gov
study summaries. Click on the title of any trial in the list to see the ClinicalTrials.gov
trial summary and more information about the study.
I am interested in participating in a clinical trial of lersivirine. How can I find more information about participating in a clinical trial?
Participating in a clinical trial can provide benefits. For example, a volunteer participant can benefit from new research treatments before they are widely available. Participants also receive regular and careful medical attention from a research team that includes doctors and other health professionals. However, clinical trials may also involve risks of varying degrees, such as unpleasant, serious, or even life-threatening side effects from the treatment being studied.5
Your health care provider can help you decide whether participating in a clinical trial is right for you. For more information, visit NIH Clinical Research Trials and You
. United States National Library of Medicine. ChemIDplus Advanced
. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development
. ViiV Healthcare website. February 2013: Lersivirine update
. Accessed April 22, 2013.
. Corbau R, Mori J, Phillips C, et al. Lersivirine, a nonnucleoside reverse transcriptase inhibitor with activity against drug-resistant human immunodeficiency virus type 1
. Antimicrob Agents Chemother. 2010 Oct;54(10):4451-63.
. National Institutes of Health (NIH). NIH Clinical Research Trials and You
. Vernazza P, Wang C, Pozniak A, et al. Efficacy and safety of lersivirine (UK-453,061) vs. efavirenz in antiretroviral treatment-naïve HIV-1-infected patients: week 48 primary analysis results from an ongoing, multicentre, randomised, double-blind, phase IIb trial (study A5271015)
. Abstract presented at: 6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention; July 17-20, 2011; Rome, Italy. Abstract TUAB0101.
Last Reviewed: May 29, 2013
Last Updated: May 29, 2013