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An Overview of Ibalizumab

May 29, 2013

Other Names: Hu5A8, TMB-355, TNX-355
Drug Class: Entry and Fusion Inhibitors
Registry Number: 680188-33-4 (CAS)
Chemical Name: Immunoglobulin G4, anti-(human CD4 (antigen)) (human-mouse monoclonal 5A8 γ4-chain), disulfide with human-mouse monoclonal 5A8 κ-chain, dimer
Company: TaiMed Biologics
Phase of Development: II
(Compound details obtained from ChemIDplus Advanced1 and NIAID Therapeutics Database2)

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 ibalizumab?

Ibalizumab is an investigational drug that is being studied for the treatment of HIV infection.

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.3

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.4

  • 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.4

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.4

In what phase of testing is ibalizumab?

Ibalizumab is currently being studied in Phase II clinical trials.2

What have recent studies shown about ibalizumab?

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.5

In this study, ibalizumab was shown to have significant antiviral activity in the treatment-experienced adults. In terms of safety, ibalizumab was well tolerated. The most common side effects were rash, diarrhea, headache, and nausea.5

A Phase I study of ibalizumab given by subcutaneous (SC) injection to healthy volunteers has been completed. (An SC injection is placed under the skin.)6

What side effects might ibalizumab cause?

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.5

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.

Where can I get more information about clinical trials studying ibalizumab?

More information about ibalizumab-related research studies is available from the AIDSinfo database of study summaries. Click on the title of any trial in the list to see the 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?

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.4

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.


  1. United States National Library of Medicine. ChemIDplus Advanced.
  2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development.
  3. Song R, Franco D, Kao CY, Yu F, Huang Y, Ho DD. Epitope mapping of ibalizumab, a humanized anti-CD4 monoclonal antibody with anti-HIV-1 activity in infected patients. J Virol. 2010 Jul;84(14):6935-42.
  4. National Institutes of Health (NIH). NIH Clinical Research Trials and You.
  5. Khanlou H, Gathe J Jr, Schrader S, Towner W, Weinheimer S, Lewis S. Safety, Efficacy, and Pharmacokinetics of Ibalizumab in Treatment-Experienced HIV-1 Infected Patients: a Phase 2b Study. Abstract presented at: 51st Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); September 17-20, 2011; Chicago, IL. Abstract H2-794b.
  6. TaiMed Biologics Inc. A Phase 1, Randomized, Double-Blinded, Placebo-Controlled, Sequential Dose-Escalation Study of the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of Subcutaneously Administered Ibalizumab in HIV-Negative, At-Risk Volunteers. In: Bethesda (MD): National Library of Medicine (US). Registered on Feb 7, 2011. NLM Identifier: NCT01292174. Last accessed April 11, 2013.

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This article was provided by AIDSinfo. Visit the AIDSinfo website to find out more about their activities and publications.
See Also
More on HIV Medications
More on Entry Inhibitors in Development

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