Research underscores Truvada's potency in preventing the transmission of HIV

September 12, 2012

New research from an international team of HIV/AIDS experts has reaffirmed the effectiveness of Truvada—the first and only medication approved by the FDA for HIV prevention. Led by Gladstone Investigator Robert Grant, MD, MPH and Peter Anderson, PharmD, at the University of Colorado, the research provides the first estimate of the drug concentration levels needed for Truvada to prevent the spread of HIV/AIDS—expanding our understanding of Truvada's potency and opening the door to new dosing strategies.

The new study, available online today in Science Translational Medicine, builds on the 2010 "iPrEx" clinical study in which Dr. Grant and his colleagues found that Truvada—which had been used for years to treat HIV-positive patients—could also prevent new infections in people likely to come in contact with the virus. But questions about the 's real-world effectiveness at preventing remained—particularly concerning the issue of adherence to a regimen of taking a pill every day.

"After the initial iPrEx study, there was concern that the protective effect of Truvada was fragile, and that individuals taking the drug would need to adhere perfectly to daily regimen for it to work," said Dr. Grant, who is also a professor at the University of California, San Francisco (UCSF), with which Gladstone is affiliated. "This new study suggests that Truvada can help block the virus even if the person on a daily regimen doesn't always adhere perfectly."

Perfect adherence to is notoriously difficult for people to accomplish. But finding out whether patients are taking medications as prescribed is also challenging—they tend to over-report their adherence because they think that is what the want to hear. So the research team had to find a better way to calculate Truvada's effectiveness while taking into account differing adherence levels.

The team developed a clinical trial in which they gave different amounts of the drug (two, four or seven doses per week) to a cohort of 24 people without HIV. This resulted in different drug concentrations in blood drawn from each participant, thereby mimicking different levels of adherence. They then used a model to compare the drug concentrations in the blood of these participants to the concentrations of original iPrEx study participants in order to determine how well iPrEx participants adhered to the daily regimen, and how well they were protected against HIV at different levels of adherence.

"Surprisingly, we found that the iPrEx participants didn't have to adhere perfectly to the drug regimen to reap Truvada's benefits," said Dr. Grant. "Even in those patients who didn't adhere perfectly, their risk of contracting HIV still dropped by more than 90%—offering a high level of protection against the virus."

Traditionally, adherence to preventative drugs such as Truvada has been measured in qualitative terms, such as "adequate" or "perfect." But this study is the first to establish an objective, quantitative method that estimates levels and then correlates those levels with the drug's effectiveness at preventing transmission. These results could open the door to the exploration of ways to optimize dosing—which would make it less costly, more convenient and more adaptable to people's habits.

"Our immediate next step, however, is to take the methods we've developed and create simple yet powerful tools that can measure drug adherence to help doctors monitor how well Truvada is working in their patients," said Dr. Anderson. "Yet until these and other efficacy studies of alternative dosing strategies have been completed, the only regimen that that should be used in clinical practice is the FDA-approved one each day."

"Patients should still take one pill a day to achieve the best results, and we encourage people to explore multiple methods to prevent HIV—such as regular condom use, early treatment of HIV infection in partners, good communication and male circumcision," Dr. Grant said. "We hope that our findings lead to more effective use of prevention tools that finally squash the / epidemic."

Explore further: US delays decision on first drug to prevent HIV

Related Stories

US delays decision on first drug to prevent HIV

June 9, 2012
(AP) — Drugmaker Gilead Sciences Inc. says federal health regulators have delayed a decision on whether to approve its drug Truvada as the first pill that prevents HIV infection.

FDA review favors first drug for HIV prevention (Update)

May 8, 2012
(AP) -- A pill that has long been used to treat HIV has moved one step closer to becoming the first drug approved to prevent healthy people from becoming infected with the virus that causes AIDS.

High-risk heterosexuals should take HIV prevention pill, too

August 10, 2012
(HealthDay) -- Doctors should consider prescribing the HIV prevention pill Truvada to their heterosexual patients who are at high risk for the virus, not just high-risk gay and bisexual men, experts from the U.S. Centers ...

HIV prevention measures must include behavioral strategies to work, says APA

May 14, 2012
A drug that has been shown to prevent HIV infection in a significant number of cases must be combined with behavioral approaches if the U.S. health care establishment is to succeed in reducing the spread of the virus, according ...

UNAIDS welcomes US approval of drug to stop HIV

July 17, 2012
The UN agency tasked with fighting AIDS on Tuesday welcomed the decision by the United States to allow the use of an HIV prevention pill for the first time.

FDA panel backs first pill to block HIV infection

May 11, 2012
The first drug shown to prevent HIV infection won the endorsement of a panel of federal advisers Thursday, clearing the way for a landmark approval in the 30-year fight against the virus that causes AIDS.

Recommended for you

Study suggests a way to stop HIV in its tracks

December 1, 2017
When HIV-1 infects an immune cell, the virus travels to the nucleus so quickly there's not enough time to set off the cell's alarm system.

Discovery puts the brakes on HIV's ability to infect

November 30, 2017
Viewed with a microscope, the virus faintly resembles a pineapple—the universal symbol of welcome. But HIV, the virus that causes AIDS, is anything but that. It has claimed the lives of more than 35 million people so far.

Rising levels of HIV drug resistance

November 30, 2017
HIV drug resistance is approaching and exceeding 10% in people living with HIV who are about to initiate or reinitiate first-line antiretroviral therapy, according to the largest meta-analysis to date on HIV drug resistance, ...

Male circumcision and antiviral drugs appear to sharply reduce HIV infection rate

November 29, 2017
A steep drop in the local incidence of new HIV infections accompanied the rollout of a U.S.-funded anti-HIV program in a large East-African population, according to a study led by researchers at Johns Hopkins Bloomberg School ...

Combination HIV prevention reduces new infections by 42 percent in Ugandan district

November 29, 2017
A study published today in the New England Journal of Medicine provides real-world evidence that implementing a combination of proven HIV prevention measures across communities can substantially reduce new HIV infections ...

Research on HIV viral load urges updates to WHO therapy guidelines

November 24, 2017
A large cohort study in South Africa has revealed that that low-level viraemia (LLV) in HIV-positive patients who are receiving antiretroviral treatment (ART) is an important risk factor for treatment failure.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.