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CROI 2016: Bone Density Recovers Quickly After Stopping Truvada PrEP

Bone mineral density recovers within 6 months after stopping pre-exposure prophylaxis (PrEP) containing tenofovir, Robert Grant from the University of California at San Francisco reported on behalf of the iPrEx study at Conference on Retroviruses and Opportunistic Infections (CROI 2016) this week in Boston.

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The study investigators reported further results from a sub-study of the iPrEx trial, which measured bone mineral density in 498 people enrolled in the international study of PrEP using tenofovir/emtricitabine (Truvada) in men who have sex with men and transgender women.

Tenofovir is known to affect bone mineral density in people who take the drug as part of antiretroviral treatment. The drug also had a modest effect on bone mineral density in men who took the drug for PrEP in the iPrEx study.

Bone development is most rapid during adolescence and usually continues in young adults up to the age of 25. Beyond this age, bone is subject to a continual process of renewal and repair. There is concern among researchers that the use of PrEP among young people may impair normal bone development, leaving them vulnerable to early-onset osteoporosis later in life.

The iPrEx study randomized men who have sex with men and transgender women who have sex with men to receive tenofovir/emtricitabine PrEP or placebo. A sub-study to evaluate changes in bone mineral density using dual X-ray absorptiometry (DXA) scans aimed to recruit 500 consecutive participants at 7 study sites in 5 cities in North and South America, Thailand, and South Africa.

Participants were exposed to tenofovir for a median of 1.2 years during the randomized phase of the study, during which they underwent DXA scans of the spine and hip at baseline and every 24 weeks until they stopped PrEP at the end of the study. They were then followed for a median of 1.5 years, during which time they had a follow up DXA scan 6 months after stopping PrEP. 289 participants received a further DXA screen on entry to the iPrEx OLE (open-label extension) study a median of 1.5 years after stopping PrEP.

The median age of participants was 25 years, 43% were smokers, and 81% drank alcohol; 11% identified as transgender.

The study compared changes in bone mineral density between the placebo group and study participants with blood levels of tenofovir diphosphate associated with 90% efficacy and use of 2-3 tablets per week (>16 fmol/m) at week 24 and those with lower drug concentrations indicating lower PrEP efficacy and lower drug exposure at week 24.

There was no significant difference in bone mineral density between the placebo group and those with suboptimal levels of tenofovir diphosphate throughout the study and follow-up period.

In contrast, bone mineral density declined by 1% in the hip and 1.8% in the spine by the end-of-study visit in those with optimal tenofovir diphosphate levels, before recovering to the same level in the spine as the placebo group at the 6-month follow up visit. Bone density in the hip took longer to recover: it had returned to baseline levels by the time participants entered iPrEx OLE, 1.5 years after stopping PrEP.

When recovery was analyzed by age as well as by drug concentration, people under age 25 demonstrated faster recovery in bone mineral density than those aged 25 and over, recovering to baseline levels in both spine and hip by 6 months after the time they had stopped PrEP.

2/23/16

Reference

R Grant, K Mulligan, V McMahan, et al. Recovery of Bone Mineral Density After Stopping Oral HIV Preexposure Prophylaxis
Robert Grant. Conference on Retroviruses and Opportunistic Infections. Boston, February 22-25, 2016. Abstract 48LB.

Other Source

National Institutes of Health. NIH-Funded Study Finds Effect of PrEP on Bone Density is Reversible. Press release. February 23, 2016.