AT AIDS 2016
DURBAN, SOUTH AFRICA (FRONTLINE MEDICAL NEWS) – Oral emtricitabine/tenofovir for pre-exposure prophylaxis against HIV acquisition in high-risk 15- to 17-year-old males proved safe and effective in the first clinical trial looking at the drug’s effects in a population so young, Sybil Hosek, PhD, reported at the 21st International AIDS Conference.
Based upon these encouraging findings, the drug’s manufacturer, Gilead Sciences, plans to file a request for the Food and Drug Administration to grant an expanded indication for emtricitabine/tenofovir (Truvada) for pre-exposure prophylaxis (PrEP) against HIV infection in teens as young as 15 years. The drug is currently approved for use only in patients aged 18 and up because there were no data in younger patients, said Dr. Hosek of John H. Stroger, Jr. Hospital , Chicago.
The prospect of an expanded indication in younger adolescents is most welcome news, she added.
“I really want to strongly, strongly, strongly say that adolescents need access to PrEP,” Dr. Hosek declared. “This is one of the best prevention options we’ve had in a long time.”
Co-investigator Craig M. Wilson, MD, concurred. “The epicenter of the HIV/AIDS epidemic in the U.S. is in 13- to 24-year-old males who have sex with males, particular MSM of color,” noted Dr. Wilson , professor of epidemiology, pediatrics, and director of the Sparkman Center for Global Health at the University of Alabama, Birmingham.
Dr. Hosek reported on 77 male teens ages 15-17 at high self-reported risk for HIV infection because of behaviors such as condomless anal intercourse with an HIV-positive or unknown-status partner. All 77 were negative for HIV at enrollment, which didn’t require parental permission. Prior to embarking on 48 months of once-daily, open-label emtricitabine/tenofovir for PrEP in this multicenter U.S. trial , they received personalized risk reduction, adherence, and behavior counseling. As part of the study protocol they had clinic visits monthly for the first 12 weeks. At that point the visits, which included testing for HIV and other STIs as well as measurement of blood drug levels as an indicator of adherence, were scaled back to once every 3 months.
The PrEP was safe and well tolerated. No one discontinued treatment because of side effects. The only adverse event of note was weight loss of 10%-19% in two patients. New STIs were diagnosed and treated in 12.3% of participants in the first 24 weeks of the study and in 10.6% in the next 24 weeks.
Three patients seroconverted during the 48-week study, for a hefty HIV infection rate of 6.41% per year. One of these patients never took the PrEP medication, the other two did so on and off but had no or very low blood levels of the drug at the time of seroconversion.
Adherence was a major issue, according to Dr. Hosek. She deemed adherence to be “really good” during the first 12 weeks of the study. During that period, the majority of participants had blood levels indicating they were taking their medication at least 4 days per week, providing high-level protection. More than 95% of subjects had detectable levels of drug, indicating they were at least trying to keep up with their medication schedule. However, once the clinic visits were scaled back from monthly to quarterly, adherence fell off drastically.
Audience member Carlos del Rio, MD , commented that he found the poor adherence over time to be really discouraging.
“The adolescent challenge is tremendous. All the studies show us that this group isn’t getting any protection. Are we trying to fit a square peg in a round hole? Is this something that’s just not going to happen, so we should look at alternatives such as long-acting injectables? It looks to me like we’re not going to get the adherence we need in adolescents with any of the things that are out there at this moment,” said Dr. del Rio, professor and chair of the department of global health and codirector of the center for AIDS research at Emory University in Atlanta.
Dr. Hosek replied that she found heartening the “outstanding” treatment adherence rate when patients were being seen monthly.
“Young people need more time,” Dr. Hosek observed. “And if they need that time from us, we have to give it to them. If they need to see us more frequently, if they need to text with us, if they need interim phone calls, a peer support group, an adherence club – whatever they need, if they want PrEP and they want to make it work, then we need to help them make it work. That’s our responsibility, to give them the time and attention they need.”
Loss of bone mineral density with PrEP
Dr. Wilson said an issue that bears watching, assuming a large increase in the use of emtricitabine/tenofovir for HIV PrEP in adolescents is in store in the near future, is drug-related loss in bone mineral density.
He presented data on changes in bone mineral density (BMD) as measured by dual-energy x-ray absorptiometry with results assessed at a core laboratory every 6 months in a companion study to the one presented by Dr. Hosek, this one involving 72 high-HIV-risk patients aged 18-22 years on 48 weeks of open-label emtricitabine/tenofovir followed by 48 weeks off PrEP.
Consistent with what’s been seen in studies of adults on emtricitabine/tenofovir, statistically significant decreases in mean Z-scores adjusted for age, sex, and race were seen at the hip and lumbar spine in this younger population between baseline and week 48 of PrEP. The reductions in BMD were in the range of 0.1-0.2 standard deviation. That’s noteworthy because up until age 20, people are supposed to be accruing bone mineralization, he observed.
During the subsequent 48 weeks off-PrEP patients showed evidence of partial but not full remineralization.
“There’s nothing here to indicate we should stop using PrEP in this age group, but given that we’d like to see high-risk young patients remain on therapy for longer than in this 48-week study, I think it would be smart to get longer-term exposure data to ensure that we still believe it’s safe,” the pediatrician commented.
Reassuringly, there is no evidence of an increase in fractures or complaints of bone pain in any studies of HIV-positive patients on tenofovir, he observed.
Because it’s unrealistic to expect to be able to routinely do serial DEXA scans in young patients on emtricitabine/tenofovir once PrEP is ramped up to the scale HIV specialists are hoping for, Dr. Wilson said he and his coinvestigators are now looking at potential biomarkers of clinically significant bone loss in young patients on chemoprophylaxis.
Dr. Wilson drew attention to the disturbingly high HIV seroconversion rate of 7.2% per year following discontinuation of PrEP after 48 weeks.
“Remember, this is a population that had already gone through extensive counseling, behavioral interventions, and personalized prevention and adherence support during the 48 weeks they were on the study drug, so they had been informed as to what the risks were. Yet we still end up with one of the highest seroconversion rates observed in any PrEP study. That tells us we still have a lot of work to do in these particular young populations,” according to Dr. Wilson.
These clinical trials of PrEP in 15- to 17- and 18- to 22-year-olds were carried out by the Adolescent Medicine Trials Network for HIV/AIDS Interventions with funding from the National Institutes of Health. Dr. Husek and Dr. Wilson reported having no financial conflicts.
