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Division of Infectious Diseases
University of Toronto
Division of Infectious Diseases
St. Michael's Hospital
Darrell H. S. Tan, MD, FRCPC, PhD, has disclosed that he has received funds for research support from AbbVie, Gilead Sciences, and GlaxoSmithKline.
Several studies of long-acting (LA) antiviral therapies were presented at the 11th International AIDS Society Conference on HIV Science (IAS 2021) and included new data on their use in the setting of pre-exposure prophylaxis (PrEP). Accordingly, in this commentary, I describe 2 IAS 2021 presentations that are especially relevant to the future of HIV prevention in Canada.
Patient Preferences Regarding PrEP Use and Prevention Considerations in Canada
The findings from an Internet-based survey among American men who have sex with men regarding LA injectable PrEP were very interesting. Beckham and colleagues conducted a discrete choice experiment—which is a methodology that I am particularly fond of for eliciting and quantifying patient preferences regarding the various attributes of a health intervention—and latent class analysis to try to identify patterns in the survey responses. They found that concerns regarding the potential for severe adverse events with LA PrEP were by far the most important potential barrier to its use, followed by the potential for out-of-pocket costs. The authors subsequently made thoughtful suggestions regarding how these findings could be used to tailor PrEP-related messaging to different audiences. For instance, potential users who are wary of adverse events should receive clear counseling that mild injection-site reactions are to be expected and they should be reassured regarding common misconceptions related to adverse events. In addition, messaging for those who are cost-conscious should focus on available drug coverage options in the relevant jurisdiction.
There are many cultural similarities between Canada and the United States. Therefore, we might be tempted to apply these survey findings when considering how to plan for the PrEP rollout with LA injectable cabotegravir in sexual minority men at risk for HIV in Canada. However, it is important to remember that this sample was largely White (63%) and university educated (78%). In much of Canada, those who stand to gain the most from LA PrEP formulations are the underserved populations that we have not been as successful at reaching with existing PrEP options. These underrepresented populations include people of color, Indigenous people, and other historically disadvantaged subsets of queer men. It will be important to specifically seek out the preferences and opinions of underserved communities in Canada in future studies. However, we might predict that concerns regarding potential adverse events and cost would also be important considerations to explore.
Another exciting study for me was the phase II trial of oral monthly islatravir as PrEP. This trial randomized 242 adults to islatravir 60 mg, islatravir 120 mg, or placebo as a monthly tablet over 6 months. Islatravir was well tolerated overall, and headache, nausea, and diarrhea were the most common adverse events with frequencies of less than 10%. Comparable to placebo, most adverse events were mild, and almost none was considered to be drug related. There were no concerning safety signals. Pharmacokinetic data on a subset of participants were also presented, demonstrating that islatravir triphosphate trough concentrations were well above the prespecified threshold for PrEP through to 8 weeks after the last study dose. As someone who is a frequent prescriber of PrEP, this PrEP trial caught my attention for a few reasons. First, although drug costs remain a challenge in most parts of the country, a very common barrier to PrEP that we encounter in Canada is the fear of adverse events among many who could otherwise benefit from PrEP. So far, the tolerability and toxicity profiles of oral islatravir look encouraging. If this pattern continues in phase III trials, many community members could be reassured, in keeping with the findings from the American men’s Internet study. Second, we know that only a tiny minority of PrEP use in Canada is among cisgender and transgender women, and there is sometimes a perception that PrEP is “only for gay men.” Although we need more implementation research on how PrEP can be used to prevent HIV in Canadian women, I was impressed to see that two thirds of this study sample were female, and I look forward to efficacy data in all sexes and genders to inform those next steps.
Will the results of these studies influence your practice and how you discuss emerging data on LA PrEP with your patients? Join the discussion by posting a comment.