Tenofovir-infused topical gel has protected non-human primates and successfully combats HIV in laboratory tests. Previous research has found that a vaginal formulation of 1 percent tenofovir was neither safe nor acceptable in the rectum. So the gel in this study was one that had been reformulated into a reduced glycerin formation of 1 percent tenofovir gel.
The participants for this study, all of whom reported receptive anal intercourse, were randomized so that each went through three phases of the trial, but in different orders. These phases included eight weeks each of the following (with a one-week “wash-out” period between each phase): the rectal 1 percent tenofovir gel with instructions to insert it into the rectum daily; the gel with instructions to use it rectally before and after anal intercourse, or at least twice weekly in the event of no receptive anal intercourse; or Truvada (tenofovir/emtricitabine) with instructions to take the tablet orally once daily. The study lasted for 27 weeks.
The participants, 12 percent of whom identified as women or transgender, made study visits every four weeks. The researchers measured the participants’ adherence to the various forms of PrEP through daily SMS texts as well as through returns of the product at each study visit (to see how much unused PrEP remained). They also tested study members’ plasma tenofovir levels at each study visit and gave them the results of that test at the subsequent visit. High adherence was defined as taking greater than 80 percent of expected doses.
There were no differences between the three versions of PrEP in terms of grade 2 adverse health problems. The researchers concluded that the rectal gel was safe in either of the dosing protocols.
Overall, the participants preferred the oral regimen to the two rectal application protocols, in particular the daily regimen. Ninety percent of individuals said they like liked the oral regimen, 80 percent liked the dosing protocol associated with sexual activity, and 70 percent liked the daily rectal gel protocol.
Adherence was generally high, and participants adhered similarly to administering the gel at least twice weekly and taking Truvada daily.
The researchers concluded that the trial supported further study of rectal microbicides in MSM and trans women, and that research should focus on convenient dosing regimens.
To read the conference abstract, click here.