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Emtricitabine/tenofovir disoproxil fumarate combo durable, safe in MSM
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BOSTON — Follow-up data from the Pre-exposure Prophylaxis Initiative suggest no additional cases of drug-resistance with pre-exposure prophylaxis combination therapy at 144 weeks. Thus indicating the therapy is durable, safe and effective in men and transgender women who have sex with men, according to Robert Grant, MD.
Data from the primary analysis on pre-exposure prophylaxis with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) combination therapy in single tablet form in 2,499 HIV-seronegative men and transgender women who have sex with men were previously reported in Infectious Disease News.
Protective effect durable
Grant, associate professor of medicine at the University of California, presented follow-up data from the study during a presentation here. “After publication, there were questions on how durable the efficacy would be over time and so at this time we are reporting on a total of 144 weeks follow-up showing that the protective effect was durable and effective.”
Compared with 64 emergent infections that occurred in those assigned placebo, only 36 infections occurred in the treatment arm — a 44% decreased incidence for HIV (95% CI, 15-63). Emergent infections that occurred within the active treatment arm of the study were due to undetectable (91%) or low drug levels (9%) in the blood, according to Grant.
“We have 31 total infections that occurred, with about one-third in the active arm of the study, and there was no evidence of drug-resistance in those who became infected after starting pre-exposure prophylaxis,” he said. “Therefore indicating that when pre-exposure prophylaxis fails, it’s really failing because the drug isn’t present in the body and its lack of presence in the body means no protection.”
“Now that we have this information, we can move forward into an open-label phase of the same study which will offer people one pill per day, but this time we will be able to tell them this is a pill that has been associated with protection and there will no longer be a placebo involved, so we think this will improve adherence.”
Effect on bone mineral density
In a separate presentation, Kathleen Mulligan, PhD, of the University of California, discussed the effects of FTC–TDF therapy on bone mineral density in a subset of seronegative men across four continents.
“We know that in studies of antiretroviral initiation in HIV-negative populations that there is a rather rapid decrease in bone mineral density after ART initiation,” Mulligan said. “This decrease tends to be greater in people also taking tenofovir. We were interested to see if pre-exposure prophylaxis containing tenofovir would have the same effect on bone mineral density in the absence of HIV infection and also in the absence of other classes of ART.”
In the DEXA sub-analysis, Mulligan and colleagues assessed 503 participants included in the Pre-exposure Prophylaxis Initiative.
Baseline data indicated 36% of the population had low bone mineral density in the spine and 18% in the hip. Further, the researchers observed a small, but statistically significant decrease in bone mineral density in the treatment arm after 24 weeks.
“We saw a higher than expected proportion of healthy HIV-negative participants who had what might be considered lower than expected bone mineral density for reasons we hope to learn from further analysis of the data,” she said. “We hope to have longer follow-up data available to see what happens after 24 weeks and to further explore the relationship between drug exposure, age and other factors with changes in bone density.” – by Jennifer Henry
For more information:
- Grant R. #92.
- Mulligan K. #94LB. Both presented at: 18th Conference on Retroviruses and Opportunistic Infections; Feb. 27-March 2, 2011; Boston.
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