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AIDSinfo Drug Database

AIDSinfo Drug Database

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Tucaresol  Audio icon

Other Names: 589C80
Drug Class: Immune Modulators
Molecular Formula: C15 H12 O5
Registry Number: 84290-27-7 (CAS)
Chemical Name: 4-[(2-formyl-3-hydroxy-phenoxy)methyl]benzoic acid
Chemical Class: Benzoic Acids
Company: GlaxoSmithKline
Phase of Development: Phase II
Chemical Image:
Click image to enlarge
Molecular Weight: 272.2548

(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 tucaresol?

Tucaresol is an investigational drug that is categorized as an immune modulator.2 Immune modulators (also called immunomodulators) are substances that modify (activate, enhance, or suppress) the immune response or the functioning of the immune system.

Tucaresol was studied for its ability to help restore or boost the immune systems of HIV-infected individuals. The drug may help to repair damage that HIV has done to the immune system and to protect the long-term health of HIV-infected individuals.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 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.4

In what phase of testing is tucaresol?

Tucaresol is being studied in Phase II clinical trials.2

What are some studies on tucaresol?

Study Name: Not available
Phase: I/II
Location: Italy
Participants: Four groups of HIV-infected participants were studied. 

  • Two groups of participants had never taken HIV medicines before entering the study (treatment-naive), while two other groups of participants had taken HIV medicines before entering the study (treatment-experienced). 
  • The groups also differed according to the participants’ CD4 counts and viral load levels. (Viral load is a measure of the amount of HIV in the blood. A CD4 count is a laboratory test that measures the number of CD4 cells in a sample of blood and is an important indicator of immune function.)

Purpose: The purpose of this study was to look at the safety and immune-modulating effects of tucaresol in different groups of HIV-infected participants.

Study Design

  • Participants in the two treatment-experienced groups continued on their antiretroviral therapy (ART) while also taking tucaresol. 
  • Participants in a third group, which was one of the treatment-naïve groups, started on both ART plus tucaresol once the study began. 
  • Participants in a fourth group, which was the other treatment-naïve group, did not start ART and took only tucaresol throughout the study.

All participants took increasing doses of tucaresol over a 12-week period. They took the medicine one time during week 1 of the study, and then once daily for 4 days at weeks 4, 8, and 12. Participants were then followed for at least 40 weeks so that the long-term effects of tucaresol could be determined.


  • In this study, tucaresol showed some immune-modulating effects. These effects were greatest in the participants who were taking ART (as well as tucaresol), and who had their viral load levels controlled at levels less than 80 copies/mL at study entry.
  • Tucaresol appeared to help restore the immune system in certain individuals by increasing the number and/or activity of certain cells of the immune system. For example, tucaresol appeared to increase HIV-specific CD8 T lymphocyte activity in some participants. (HIV-specific CD8 T lymphocytes are a type of immune cell that recognizes and destroys cells infected with HIV.)
  • Investigators note that this study was very preliminary and that it is still not known whether the immune-modulating effects of tucaresol will have any clear health benefits for HIV-infected individuals. More clinical trials will be needed to determine the benefits of adding tucaresol to ART.
  • In terms of safety, serious side effects occurred in the first week of the study in two participants, both of whom were treatment-naive before entering the study. (One participant was taking only tucaresol and was not on ART during the study; the other participant started ART for the first time along with tucaresol.) No serious side effects occurred in the treatment-experienced participants taking both ART and tucaresol throughout the study.3,5,6

What side effects might tucaresol cause?

In the Phase I/II study discussed under the previous question, the most common side effects that occurred in the treatment-experienced participants who were taking ART and tucaresol were low-grade fever and other mild constitutional symptoms. (Constitutional symptoms are symptoms affecting the whole body, such as fever and weight loss.)3

Because tucaresol is still being studied, information on possible side effects of the drug is not complete. As testing of tucaresol continues, additional information on possible side effects will be gathered.

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

More information about tucaresol-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 tucaresol. 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. Available at: Last accessed on July 15, 2015.
  2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Available at: Last accessed on July 15, 2015.
  3. Gori A, Trabattoni D, Bandera A, et al. Immunomodulation induced by tucaresol in HIV infection: results of a 16 week pilot Phase I/II trial.Antivir Ther. 2004 Aug;9(4):603-14. Available at: Last accessed on July 15, 2015.
  4. National Institutes of Health (NIH). NIH Clinical Research Trials and You. Available at: Last accessed on July 15, 2015.
  5. Bandera A, Gori A, Trabattoni D, et al. Positive Immunomodulatory Effects of Tucaresol in HIV-infected Patients: Results from a Phase I/II Trial after 40 Weeks of Follow-up. Abstract presented at: 10th Conference on Retroviruses and Opportunistic Infections (CROI); February 10-14, 2003; Boston, MA. Abstract 654. Available at: Last accessed on April 23, 2014.
  6. Gazzola L, Marchetti G, Bandera A, et al. Dynamics of T Cells Homeostasis Induced by Tucaresol. Abstract presented at: 11th Conference on Retroviruses and Opportunistic Infections (CROI); February 8-11, 2004; San Francisco, CA. Abstract 523. Available at: Last accessed on April 23, 2014.

Last Reviewed: July 15, 2015

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