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An Overview of PRO-140

May 29, 2013

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Other Names: PA14
Drug Class: Entry and Fusion Inhibitors
Company: CytoDyn Inc
Phase of Development: Phase II
(Compound details obtained from ChemIDplus Advanced1, NIAID Therapeutics Database2, and CytoDyn website3)

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 PRO-140?

PRO-140 is an investigational drug that is being studied for the treatment of HIV infection.


PRO-140 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.

PRO-140 works by attaching to one of two proteins on the surface of the immune cells. These proteins are called the CCR5 and CXCR4 coreceptors. PRO-140 attaches to the CCR5 coreceptor. When PRO-140 attaches to the CCR5 coreceptor, certain strains of HIV -- called R5-tropic virus -- cannot attach to, enter, or infect the cell.4

Research may prove that PRO-140 is a safe and effective option for treating people with R5-tropic virus, including those for whom other entry and fusion inhibitors, such as maraviroc (brand name: Selzentry), are not working.5

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.6

  • 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.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 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.6

In what phase of testing is PRO-140?

PRO-140 is currently being studied in Phase II clinical trials.2

What have recent studies shown about PRO-140?

In a Phase IIa study, PRO-140 was compared with placebo in HIV-infected participants who had R5-tropic virus. (A placebo is an inactive drug that is identical in appearance to the active drug being studied.) In this study, PRO-140 was given by subcutaneous (SC) infusion and at different strengths and dosing frequencies (every week or every other week). (An SC infusion is an injection placed under the skin to deliver a drug or other fluids over a period of time.) Some of the participants had never taken HIV medicines before entering the study (treatment-naive), and others had taken HIV medicines previously (treatment-experienced). The treatment-experienced participants were required to be off HIV medicines for at least 12 weeks before starting the study.7,8

In this study, PRO-140 at all of the dosages studied was shown to have significant antiviral activity. In terms of safety, PRO-140 was generally well tolerated. No drug-related serious side effects occurred.7,8

An additional Phase II study of long-acting PRO-140 given by SC infusion is under way in HIV-infected injection drug users who have viral rebound (detectable levels of HIV after a period of undetectable levels) and who had poor adherence to prior HIV medicine treatment.9

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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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