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AIDSinfo Drug Database

AIDSinfo Drug Database

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Amdoxovir  Audio icon

Other Names: AMDX, DAPD, prodrug of DXG
Drug Class: Nucleoside Reverse Transcriptase Inhibitors
Molecular Formula: C9 H12 N6 O3
Registry Number: 145514-04-1 (CAS)
Chemical Name: [(2R,4R)-4-(2,6-diaminopurin-9-yl)-1,3-dioxolan-2-yl]methanol
Chemical Class: Purine Nucleosides
Company: RFS Pharma
Phase of Development: IIa (discontinued)

Chemical Image:
Click image to enlarge
Molecular Weight: 252.2328
(Compound details obtained from ChemIDplus Advanced,1 NIAID Therapeutics Database,2,3 and HIV i-BASE/Treatment Action Group 2013 Pipeline Report4)

NOTE: The development of amdoxovir for HIV treatment has been discontinued.

Amdoxovir is no longer being studied for use as an HIV medicine. The last time that amdoxovir had an active clinical trial appears to have been in 2010.4

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.

To learn more about investigational drugs, read the AIDSinfo What is an Investigational HIV Drug? fact sheet.

What is amdoxovir?

Amdoxovir is an investigational drug that was studied for the treatment of HIV infection.

Amdoxovir belongs to a class (group) of HIV drugs called nucleoside reverse transcriptase inhibitors (NRTIs).2 NRTIs block an HIV enzyme called reverse transcriptase. (An enzyme is a protein that starts or increases the speed of a chemical reaction.) By blocking reverse transcriptase, NRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body.

In vitro
studies suggested that amdoxovir could effectively treat people whose HIV could not be controlled by the NRTIs lamivudine, emtricitabine, zidovudine, and stavudine. (In vitro studies are studies done in test tubes or other laboratory equipment and not on animals or humans.) 5,6,7 

In vitro studies have also shown that amdoxovir may help treat hepatitis b virus (HBV) infection.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.8

  • 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.8

In most cases, an investigational drug must be proven effective and must show continued safety 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.8 (Some clinical trials are categorized as “a” or “b,” such as “Phase Ia” or “Phase IIb.” These different subphases typically mean that a study is researching certain types of information or using a certain type of participant population.)

In what phase of testing is amdoxovir?

Amdoxovir has been studied in a Phase IIa clinical trial.2,3

What are some studies on amdoxovir?

Study Names: RFS-AMDX-203; NCT00432016
Sponsor: RFS Pharma, LLC
Phase: Ib/IIa
Location: Argentina

  • Participants were HIV-infected adults who had either never taken HIV medicines before entering the study or who had taken HIV medicines previously. Participants who had previously taken HIV medicines were required to be off treatment for at least 3 months before starting the study.
  • Participants had viral load levels of at least 5,000 copies/mL. (Viral load is the amount of HIV in a blood sample.)
  • Participants had CD4 counts of at least 200 cells/mm3. (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 effectiveness of amdoxovir used alone and amdoxovir combined with 2 different doses of the FDA-approved HIV medicine zidovudine (brand name: Retrovir).7,9

A Phase IIa study (RFSP-AMDX-2010; NCT01737359) that was designed to compare 2 different doses of twice-daily amdoxovir to the FDA-approved NRTI tenofovir disoproxil fumarate (brand name: Viread) was terminated. The study included adults who had taken HIV medicines previously but whose HIV wasn’t being controlled by their HIV medicines. Participants had HIV that contained mutations known to cause NRTIs to not work well.3

For more details on the studies listed above, see the Health Professional version.

What side effects might amdoxovir cause?

In the RFS-AMDX-203 study (NCT00432016) discussed above, amdoxovir alone and amdoxovir in combination with zidovudine appeared to be safe. Side effects were temporary and mild to moderate in severity. The most common side effects in the groups receiving amdoxovir combined with zidovudine were headache and nausea.10

If testing of amdoxovir continues, additional information on possible side effects will be gathered.


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

More information about amdoxovir-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.

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.8

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 February 3, 2017.
  2. National Institute of Allergy and Infectious Diseases (NIAID). NIAID ChemDB, HIV Drugs in Development. Available at: Last accessed on February 3, 2017.
  3. RFS Pharma, LLC. A Phase IIa, Randomized, Double-blind, Active-controlled, 12-week Study of Amdoxovir (Two Doses) Versus Tenofovir DF, in Combination With Zidovudine in HIV-1 Treatment-experienced Subjects With M184I/V Mutation in Addition to 0-2 Confirmed Thymidine Analog Mutations. In: Bethesda (MD): National Library of Medicine (US). Registered on November 27, 2012. NLM Identifier: NCT01737359. Available at: Last accessed on February 3, 2017.
  4. Clayden P, Collins S, Daniels C, et al. HIV i-BASE/Treatment Action Group. 2013 Pipeline Report. Benzacar A, ed. June 2013. Available at: Last accessed on February 3, 2017.
  5. Hurwitz SJ, Asif G, Fromentin E, Tharnish PM, Schinazi RF. Lack of Pharmacokinetic Interaction between Amdoxovir and Reduced- and Standard-Dose Zidovudine in HIV-1-Infected Individuals. Antimicrob Agents Chemother. 2010 Mar;54(3):1248-55. Available at: Last accessed on February 3, 2017.
  6. Pozniak AL. Investigational agents for salvage. Curr Opin HIV AIDS. 2009 Nov;4(6):524-30. National AIDS Treatment Advocacy Project (NATAP): HIV Articles; Investigational HIV agents for salvage. Available at: Last accessed on February 3, 2017.
  7. Murphy RL, Kivel NM, Zala C, et al. Antiviral activity and tolerability of amdoxovir with zidovudine in a randomized double-blind placebo-controlled study in HIV-1-infected individuals. Antivir Ther. 2010;15(2):185-92. Available at: Last accessed on February 3, 2017.
  8. National Institutes of Health (NIH). NIH Clinical Research Trials and You. Available at: Last accessed on February 3, 2017.
  9. RFS Pharma, LLC. A Randomized, Placebo-Controlled Study to Evaluate Safety, Tolerance, Pharmacokinetics and Antiviral Activity of Amdoxovir and Zidovudine in Untreated HIV-1 Infected Subjects Currently Untreated. In: Bethesda (MD): National Library of Medicine (US). Registered on February 5, 2007. NLM Identifier: NCT00432016. Available at: Last accessed on February 3, 2017.
  10. Murphy R, Zala C, Ochoa C, et al. Pharmacokinetics and Potent Anti-HIV-1 Activity of Amdoxovir Plus Zidovudine in a Randomized Double-blind Placebo-controlled Study. 15th Conference on Retroviruses and Opportunistic Infections (CROI); February 3-6, 2008; Boston, MA. Levin: Conference reports for National AIDS Treatment Advocacy Project (NATAP); 2008. Available at: Last accessed on February 3, 2017.

Last Reviewed: February 3, 2017

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