An Overview of Lersivirine

Other Names: UK-453,061
Drug Class: Non-nucleoside Reverse Transcriptase Inhibitors

What is lersivirine?

Lersivirine is an investigational drug for the treatment of HIV infection.

• Lersivirine is an investigational anti-HIV drug included in the non-nucleoside reverse transcriptase inhibitor (NNRTI) drug class.
• NNRTIs prevent HIV from replicating by blocking reverse transcriptase, an HIV enzyme. By preventing HIV from replicating, NNRTIs reduce the amount of HIV in the blood.
• Lersivirine is a second-generation NNRTI and appears to have activity against certain NNRTI-resistant viruses.

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.

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.

• 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.

An investigational drug must be proven safe and effective in a Phase III clinical trial to be considered for traditional 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.

In what phase of testing is lersivirine?

Lersivirine is currently being studied in several Phase II clinical trials.

What have recent studies shown about lersivirine?

In a Phase II study, two different doses of lersivirine taken once daily were compared with efavirenz (brand name: Sustiva), an FDA-approved NNRTI, taken once daily in treatment-naive participants. Study participants also received additional anti-HIV drugs as part of their background regimen. (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.) 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.

Additional Phase II studies of lersivirine in both HIV treatment-naive and treatment-experienced adults are under way.

More information on Phase II testing of lersivirine is available from these sources:

• Lersivirine study results presented at the 6th IAS Conference on HIV Pathogenesis, Treatment and Prevention, July 17-20, 2011:
  • 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)
  • Craig C, Wang C, Cusack N, et al. Minority species resistance present at screening does not affect outcomes at week 48 in lersivirine (UK-453,061) phase IIb study A5271015 in treatment-naive patients

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 of an investigational drug?

Clinical trials involve benefits and risks. Before deciding to participate in a clinical trial, talk to your health care provider. For more information on participating in clinical trials, visit NIH Clinical Research Trials and You.