Adherence, anatomy, resistance
The key theories for the lack of a prevention of infections in cisgender women surround the issues of resistances, as well as anatomy and adherence, said Dr. Stewart.
In terms of bacterial resistances, while initial testing in a limited number of samples the study found no evidence of markers of resistance for chlamydia, all of the gonorrhea samples did show tetracycline-resistant N gonorrhea at baseline and follow-up in both groups.
Regarding anatomic differences, doxycycline may not prevent STIs in endocervical tissue among cisgender women, Dr. Stewart noted. Women are known to be at higher risk of infection because the lining of the vagina is thinner than the skin of the penis, allowing for easier penetration of bacteria and viruses.
The study was designed to optimize adherence to Doxy PEP. Measures included monitoring with weekly text message surveys, in which the women reported a high rate of adherence.
The overall retention rate in the study was high; as many as 97% of the quarterly follow-up visits were completed, including 95% in the Doxy PEP group and 98% of the standard care group. The response rate for the weekly surveys was 81%.
Of note, women reported the use of the treatment to be “imperfect,” suggesting social problems, such as biases toward the use of the prophylaxis.
The results underscore the need for ongoing efforts to make sure no groups of patients are left behind as interventions advance, Dr. Stewart said.
“The burden of STIs on cisgender women is large and growing,” she concluded. “STI prevention interventions are needed.”
Commenting on the study, Renee A. Heffron, PhD, MPH, said the findings “are somewhat surprising because results from trials in other populations have been positive.
“But cisgender women are exposed through the cervix, and this tissue is different from rectal or urethral tissue,” Dr. Heffron, a professor at the department of medicine and director of the Center for AIDS Research at the University of Alabama, Birmingham, told this news organization.
Further findings from the research should help shed light on key issues of adherence and drug concentration levels in cervical tissue, she added.
“For cisgender women, these data are the first and the beginning of understanding whether this is a viable strategy,” Dr. Heffron said.
“We have more to learn to better understand the results from the trial main outcomes, and if there are tweaks to this strategy that would improve efficacy.”
The authors and Dr. Heffron have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.