What is ibalizumab?
Ibalizumab is an investigational drug for the treatment of HIV infection.
- Ibalizumab is an investigational anti-HIV drug included in the entry inhibitor drug class.
- Entry inhibitors interfere with the first step in the HIV life cycle—binding and fusion to target cells. By preventing HIV from entering target immune cells, entry inhibitors stop HIV from replicating and reduce the amount of HIV in the blood.
- Ibalizumab is a monoclonal antibody that specifically binds to the CD4 receptor located on the surface of certain immune cells, such as CD4 cells. When ibalizumab binds to the CD4 receptor, HIV cannot bind to, enter, or infect the immune cell.
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 ibalizumab?
Ibalizumab is currently being studied in Phase II clinical trials.
What have recent studies shown about ibalizumab?
In a Phase II study, ibalizumab’s safety and efficacy were investigated at two different strengths in treatment-experienced HIV-infected participants. Intravenous (IV) ibalizumab was given to treatment-experienced patients every 2 weeks or every 4 weeks (depending on the strength of the drug). Study participants also received optimized background therapy. (An optimized background regimen is a combination of drugs, chosen on the basis of a person’s resistance test results and treatment history, that are not being studied as the investigational drug[s] in the clinical trial, but are given to help control a participant’s HIV infection.) No control arm was used in this trial.
In HIV treatment-experienced adults, ibalizumab was shown to have significant antiviral activity. In terms of safety, ibalizumab was well tolerated. The most common side effects were rash, diarrhea, headache, and nausea.
A Phase I study of ibalizumab given by subcutaneous injection to healthy volunteers is ongoing.
More information on Phase II testing of ibalizumab is available from these sources:
- Ibalizumab study results presented at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), September 17–20, 2011:
- PubMed abstract:
Where can I get more information about clinical trials studying ibalizumab?
More information about ibalizumab-related
research studies is available from the AIDS
info 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 ibalizumab. 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.
Last Reviewed: October 22, 2012
Last Updated: October 22, 2012