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.
Elvucitabine is an investigational drug that is being studied for the treatment of HIV infection.
Elvucitabine 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.
Elvucitabine is similar in chemical structure to the FDA-approved NRTIs lamivudine (brand name: Epivir) and emtricitabine (brand name: Emtriva).3 However, in vitro studies have suggested that elvucitabine may work on certain HIV strains against which other NRTIs, such as lamivudine and emtricitabine, no longer work.4
In vitro studies have also suggested that elvucitabine may be effective against hepatitis B virus (HBV).5 (In vitro studies are studies done in test tubes or other laboratory equipment and not on animals or humans.)
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 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
Elvucitabine has been studied in Phase II clinical trials.2
In a 96-week Phase II study, elvucitabine taken once daily was compared to the HIV medicine lamivudine in HIV-infected participants who had never taken HIV medicines before entering the study (treatment-naive). All study participants also received the HIV medicines tenofovir disoproxil fumarate (brand name: Viread) and efavirenz (brand name: Sustiva) as part of their background regimens. (A background regimen is a combination of drugs that are not being studied as the investigational drug[s] in the clinical trial, but are being given to help control a participant’s HIV infection.)7
In this study, using an as-treated analysis (looking at data from the participants who completed the full length of the study), elvucitabine proved as effective as lamivudine, with similar numbers of patients in both treatment groups having reductions in the amount of HIV in the blood (viral load) after 96 weeks. However, using an intention-to-treat anaylsis (looking at data from all study participants, including those who discontinued the study), fewer participants in the elvucitabine treatment group had a virologic response than in the lamivudine group. This difference is because the elvucitabine group had a higher proportion of study drop-outs than the lamivudine group did. In terms of safety, elvucitabine was comparable to lamivudine. One participant discontinued elvucitabine because of a drug-related side effect.7
An additional Phase II study of elvucitabine in HIV-infected adults with the M184V HIV resistance mutation was completed. The participants in this study had been taking HIV medicines before entering the study (treatment-experienced).8
In the 96-week Phase II study discussed under the previous question, some side effects that were reported included the following: nausea, dizziness, fatigue, diarrhea, vomiting, indigestion, and weakness.7
Because elvucitabine is still being studied, information on possible side effects of the drug is not complete. As testing of elvucitabine continues, additional information on possible side effects will be gathered.
More information about elvucitabine-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.
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. Shi J, Mathew JS, Tharnish PM, et al. N4-acyl-modified D-2',3'-dideoxy-5-fluorocytidine nucleoside analogues with improved antiviral activity. Antivir Chem Chemother. 2003 Mar;14(2):81-90.
4. Colucci P, Pottage JC, Robison H, Turgeon J, Ducharme MP. Effect of a single dose of ritonavir on the pharmacokinetic behavior of elvucitabine, a nucleoside reverse transcriptase inhibitor, administered in healthy volunteers. Antimicrob Agents Chemother. 2009 Feb;53(2):646-50.
5. Zhu YL, Dutschman DE, Liu SH, Bridges EG, Cheng YC. Anti-hepatitis B virus activity and metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine. Antimicrob Agents Chemother. 1998 Jul;42(7):1805-10.
6. National Institutes of Health (NIH). NIH Clinical Research Trials and You.
7. DeJesus E, Saple D, Morales-Ramirez J, et al. Elvucitabine vs Lamivudine with Tenofovir and Efavirenz in Antiretroviral-Treatment-Naïve HIV-1 Infected Patients: 96 Week Final Results. Poster presented at: 17th Conference on Retroviruses and Opportunistic Infections (CROI); February 16-19, 2010; San Francisco, CA. Paper 511.
8. Achillion Pharmaceuticals. A 14 Day Randomized, Double Blind, Study of Once Daily Elvucitabine Versus Lamivudine in Subjects With a Documented M184V Mutation. In: ClinicalTrials.gov. Bethesda (MD): National Library of Medicine (US). Registered on April 5, 2006. NLM Identifier: NCT00312039. Last accessed May 26, 2013.
Last Reviewed: May 29, 2013
Last Updated: May 29, 2013