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.
Ibalizumab is an investigational drug that is being studied for the treatment and prevention of HIV infection.4
Ibalizumab belongs to a class (group) of HIV drugs called entry and fusion inhibitors.2 Entry and fusion inhibitors block HIV from getting into and infecting certain cells of the immune system. This prevents HIV from multiplying and can reduce the amount of HIV in the body.
Ibalizumab works by attaching to a protein on the surface of the immune cells. The protein is called the CD4 receptor. When ibalizumab attaches to the CD4 receptor, HIV cannot attach to, enter, or infect the cell.5
Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.6
In most cases, an investigational drug must be proven safe and effective in a Phase III clinical trial to be considered for approval by FDA for sale in the United States. Some drugs go through FDA’s accelerated approval process and are approved before a Phase III clinical trial is complete. After a drug is approved by 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.6
Ibalizumab is currently being studied in a Phase IIb clinical trial.2
Expanded access to ibalizumab may be available to patients who qualify for compassionate use treatment. (More details can be found on ClinicalTrials.gov [NCT02028819].)3
In a 24-week Phase IIb study, ibalizumab’s safety and efficacy were investigated at two different strengths in HIV-infected participants who had taken HIV medicines before entering the study (treatment-experienced). Intravenous (IV) ibalizumab was given to the treatment-experienced patients either every 2 weeks or every 4 weeks, depending on the strength of the drug. (An IV injection is placed directly into a vein.) 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 study.7
In this study, ibalizumab was shown to have significant antiviral activity in the treatment-experienced adults. In terms of safety, there were no serious adverse events among participants, none of the participants stopped the study because of side effects, and there were no clinically relevant effects on participants' vital signs or laboratory values. The most common side effects were rash, diarrhea, headache, and nausea.7
Ibalizumab has also been studied as a medicine for HIV prevention. A Phase I study looking at the safety of ibalizumab given by subcutaneous (SC) injection to at-risk, HIV-uninfected adults has been completed. (An SC injection is placed under the skin.)8
In the 24-week Phase IIb study discussed under the previous question, the most common side effects reported were the following: rash, diarrhea, headache, and nausea. Most side effects were considered mild to moderate.7
Because ibalizumab is still being studied, information on possible side effects of the drug is not complete. As testing of ibalizumab continues, additional information on possible side effects will be gathered.
More information about ibalizumab-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.
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.6
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.
Last Reviewed: July 28, 2014