April 22, 2016
This week, we got our first published glimpse of how the new tenofovir stacks up against the old tenofovir after two full years of first-line therapy. We were also given a first look at what a long-acting form of pre-exposure prophylaxis (PrEP) might do for rates of HIV infection and mortality among high-risk populations -- and what it might cost. Plus, we were given a critical new resource to help improve HIV testing and outreach among trans people. To beat HIV, you have to follow the science!
At 96 weeks, tenofovir alafenamide (TAF) continues to keep pace virologically with tenofovir disoproxil fumarate (TDF, Viread) in treatment-naive people with HIV, while exhibiting a superior toxicity profile, according to study results published in the May 1 issue of the Journal of Acquired Immune Deficiency Syndromes.
The study summarizes the findings of two Phase 3, double-blind, placebo-controlled trials that randomized 1,733 antiretroviral-naive volunteers to receive elvitegravir/cobicistat/emtricitabine coformulated with either TAF or TDF. After two years on the study drugs, there was no significant difference between the percentage of people with a viral load below 50 copies/mL who received TAF (86.6%) and those who received TDF (85.2%), with virtually no emergence of resistance among those whose therapy failed in either arm. However, marked differences were noted between the two drugs on the toxicity front.
"With TAF, there are smaller declines in bone mineral density and more favorable changes in proteinuria, albuminuria, and tubular proteinuria, and no cases of proximal tubulopathy compared with 2 for TDF," the study authors noted. In fact, differences in bone mineral density widened between weeks 48 and 96 despite increased usage of drugs to improve bone density among TDF recipients, they stated. The authors also commented on a continuation of more favorable renal markers among TAF recipients relative to TDF recipients in the span between week 48 and week 96.
"Together, these longer-term safety data support the hypothesis that circulating levels of TFV [tenofovir] are responsible for the bone and renal toxicity of TDF and that the markedly reduced TFV level delivered by TAF minimizes such exposure and is protective against renal and bone effects," the researchers conclude.
The eventual use of long-acting antiretrovirals for PrEP will probably prevent more HIV infections among high-risk South African women than the current PrEP standard regimen, but at greater financial cost, according to the results of an extensive computer simulation by researchers in the U.S. and South Africa.
Appearing in the Journal of Infectious Diseases, the study, led by Rochelle Walensky, M.D., M.P.H., of Massachusetts General Hospital, calculated the comparative cost and effectiveness of three PrEP strategies implemented among a simulated cohort of young South African women (mean age 18). Using an extensive array of existing study data to inform their models, the researchers sought to generate reasonable estimates of the impact of no PrEP, standard PrEP (using existing oral formulations) and long-acting injectable PrEP on lifetime HIV risk and five-year mortality, as well as the cost-effectiveness of each approach.
The simulation found that, after an average of eight years of PrEP use, reasonably effective (75%) long-acting PrEP reduced lifetime HIV incidence among the virtual cohort by 19% compared to no PrEP (510 cases per 1,000 high-risk women, compared to 630); by comparison, reasonably effective (62%) standard PrEP reduced lifetime HIV incidence by 14% over eight years compared to no PrEP (540 cases per 1,000 high-risk women). Within five years, long-acting PrEP would avert 156 new HIV infections and 16 deaths, while standard PrEP would avert 127 new HIV infections and 15 deaths, the model predicted.
Although both PrEP approaches were deemed to be cost-saving relative to the use of no PrEP at all, standard PrEP was found to be the least expensive over the course of a cohort member's lifetime, at US$5,270 total (compared to the slightly higher $5,300 for long-acting PrEP, and the sharply higher $5,730 for no PrEP, which included the costs of HIV care and antiretroviral therapy for the greater number of women who would become infected). Long-acting PrEP program implementation was found to have a much higher ramp-up cost than standard PrEP implementation, but a lower cost afterward.
"The delivery of existing oral PrEP formulations, which are very cost-effective, should be expanded and optimized for young, high-risk South African women," the researchers concluded. In addition, they urge that "the research and development effort should be expanded to bring a viable [long-acting] PrEP formulation to market."
In support of the first National Transgender HIV Testing Day (NTHTD) in the U.S. on April 18, the Center of Excellence for Transgender Health at the University of California-San Francisco (UCSF) released a set of training materials aimed at helping community-based HIV organizations and HIV prevention programs create more effective services for trans people.
The toolkit, which is available as a PDF, focuses on succinct provision of "best practice" guidelines and overview information based on available research. It is divided into five overarching modules:
Myles Helfand is the editorial director of TheBody.com and TheBodyPRO.com.
Follow Myles on Twitter: @MylesatTheBody.
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