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).4 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.5 (In vitro studies are studies done in test tubes or other laboratory equipment and not on animals or humans.)
Studies have also suggested that elvucitabine may be effective against hepatitis B virus (HBV).5-7
Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.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
Elvucitabine has been studied in Phase II clinical trials.2 (The company developing elvucitabine has reported that it is out-licensing elvucitabine and looking to work with partner companies to focus elvucitabine’s development in regions outside the United States.)3
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 (also called 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.)9,10
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 viral load (the amount of HIV in a blood sample) 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. All serious side effects that occurred during the study were unrelated to the study drugs. One participant discontinued elvucitabine because of a drug-related side effect.9,10
An additional Phase II elvucitabine study was completed. The study compared elvucitabine with lamivudine in HIV-infected adults who had the M184V HIV resistance mutation. The participants in this study had been taking HIV medicines before entering the study (also called treatment-experienced).11
In the 96-week Phase II study discussed under the previous question, the number, types, and severity of side effects that occurred were similar between the elvucitabine and lamivudine groups. Some drug-related side effects that were reported included the following: nausea, dizziness, fatigue, diarrhea, vomiting, indigestion, and weakness.9,10
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.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.
Last Reviewed: October 22, 2014