Prevention of STIs: effective post-exposure doxycycline |

Prevention of STIs: effective post-exposure doxycycline |

The results of the DOXYPEP study confirm the benefit of taking doxycycline after sexual intercourse (PEP for post-exposure) in reducing the risk of bacterial sexually transmitted infections (STIs).

Annie Luetkemeyer, from Zuckerberg San Francisco General Hospital, UCSF, presented these encouraging results at the 2022 Montreal International Conference on HIV Human immunodeficiency virus. In English: HIV (Human Immunodeficiency Virus). Isolated in 1983 at the Pasteur Institute in Paris; recently discovered (2008) rewarded with the Nobel Prize in Medicine awarded to Luc Montagnier and Françoise Barré-Sinoussi./AIDS Acquired immune deficiency syndrome. In English, AIDS, acquired immuno-deficiency syndrome.. The DOXYPEP trial studied the benefit of taking antibiotics post-exposure against sexually transmitted infections. The previous data, from the IPERGAY trial, already underlined the interest and Proof of concept post-exposure Doxycycline, for syphilis and chlamydia, but unfortunately not for gonorrhea (an expected result given the levels of resistance). The results of quarterly reviews of DOXYPEP show a reduction of about two thirds in the risk of contracting a STI Sexually transmitted infections. bacterial. Most of the STIs detected were asymptomatic.

Efficacy of doxycycline in PEP, IPERGAY data. Source: A. Luetkemeyer, AIDS 2022.

The DOXYPEP trial evaluated the benefit of taking 200 mg of the antibiotic doxycycline within 72 hours of having sex without a condom (not more than once every 24 hours). The study was open to men who have sex with men and trans women. These people are particularly exposed to STIs and had to have experienced an episode of sexually transmitted infection during the last year to join the cohorts.

Design of the DOXYPEP study. Source: A. Luetkemeyer, AIDS 2022.

DOXYPEP included a group for HIV-negative people on pre-exposure prophylaxis (Prep Pre-Exposure Prophylaxis. PrEP is a strategy that enables an HIV-negative person exposed to HIV to eliminate the risk of infection by taking, continuously or “on demand”, an anti-retroviral treatment based on Truvada®. ) and another for people living with HIV, and participants were supposed to be followed for 12 months at sexual health clinics in Seattle and San Francisco. Every 3 months an STI search was planned. Two-thirds of each arm received doxycycline in PEP, and the last thirds a classic follow-up for STI research.

Profile of DOXYPEP participants. Source: A. Luetkemeyer, AIDS 2022.

These very positive results prompted the researchers to interrupt the trial a year before the planned end: Faced with the significant difference in effectiveness between the two arms, the monitoring committee recommended in May 2022 to stop recruiting new people. Everyone in the study had access to doxycycline. The initial design planned to recruit 780 people in total, but enrollment stopped at 554 participants (360 in the PrEP arm, 194 in the living with HIV arm).

Reduction in the incidence of STIs per trimester. Source: A. Luetkemeyer, AIDS 2022.

High efficacy against several STIs

In the randomization arm of HIV-negative people, the efficacy was 66%, with 65 infections in the control arm and 47 in the doxycycline arm, which had twice as many people, giving a quarterly incidence of 29.5% in the control arm and 9.6% in the doxycycline arm. Among HIV-positive participants, efficacy was somewhat lower, with 62% efficacy. Thirty STIs were counted in the control arm, and 31 in the doxycycline arm, ie quarterly incidence rates of 27.8% and 11.7% respectively in the control arm.

Reduction in the incidence of each STI per trimester. Source: A. Luetkemeyer, AIDS 2022.

Efficacy was highest against chlamydia, with 79% in HIV-negative people and 70% in people living with HIV. Against gonorrhea, it was 59% in people without HIV and 57% in people with HIV.

The slightly higher number of cases observed in people taking doxycycline does not suggest that these doses aggravate tetracycline resistance in gonorrhea, but that doxycycline is less effective in treating gonorrhea, because of the expected resistance. Concerning gonorrhea, only 30% of them could be studied within the framework of the study: 20% turned out to be forms resistant to tetracycline, the treatment of choice, which corresponds to the known American figures. (A figure lower than what IPERGAY had estimated, with 56%.)

Simple prevention

In this trial, post-exposure doxycycline was shown to be safe and tolerable (only 1.5% of participants discontinued due to adverse effects), andobservance Therapeutic compliance corresponds to strict compliance with the prescriptions and recommendations formulated by the prescribing doctor throughout a treatment, which is essential in the case of anti-HIV treatment. (Also referred to as adhesion or adherence.) was high (87% of sexual acts were covered by taking doxycycline)

However, Annie Luetkemeyer underlined the major need for additional bacteriological data, which is lacking in this type of study, with regard to the risks of resistance (including S. aureus, Commensal Neisseria, and more generally on the intestinal microbiome). The assessment of the impact on sexual behavior is also in progress, and the DoxyVac sub-study of the ANRS Prevenir study should also provide additional data, particularly on gonorrhea.

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