SOURCE : allAfrica
Read the original article on The Conversation Africa.
ANALYSIS
By Thesla
Palanee-Phillips, University of the Witwatersrand
The results of the two
studies showing that a vaginal ring can help reduce the risk HIV infection
among women is being hailed as an important HIV prevention breakthrough.
Launched four years ago, the two clinical trials, known
as ASPIRE and The Ring Study, set out to determine how safe and effective
the ring was in prevention of HIV infection in women. The ring, which is used
for a month at a time, contains an antiretroviral drug called dapivirine that
acts by blocking HIV from multiplying.
The studies enrolled close to 4500 women aged 18 to 45 in
South Africa, Uganda, Malawi and Zimbabwe. Each study found that the ring helps
reduce the risk of HIV infection in women. In ASPIRE, the ring reduced the risk
of HIV infection by 27% overall. In The Ring Study, infections were reduced by
31% overall.
But there were differences in how effective the ring was
based on how consistently the women used it. Both studies showed that the more
consistently the ring is used, the more effective it is in protecting women.
For women aged 18 to 21 in both studies there was no
significant protection because they did not use the ring consistently. ASPIRE
found that HIV protection was greater in groups with evidence of better ring
use. Incidence of HIV was cut by more than half - 56% - among women 21 and
older, who, as a group, appeared also to use the ring most consistently.
The studies show that the ring has the potential to help
make a difference in reducing the burden of HIV by at least one third in women
overall. This has significant implications for reducing the burden of disease
in women in Africa.
Women
can have another option
It is the first time two phase-three clinical trials have
confirmed statistically significant efficacy for a microbicide to prevent HIV. The dapivirine ring was
designed to offer potentially long-acting protection against HIV through slow,
continuous delivery of dapivirine into the vaginal tissues over the course of
four weeks.
Women account for nearly 60% of adults with HIV. Unprotected heterosexual sex drives this
figure. Despite tremendous advances in preventing and treating HIV, women still
face a disproportionate risk of infection because there are insufficient
practical HIV prevention options available to them.
If the ring becomes available for commercial use it will
add to the tools in the HIV prevention toolbox for women alongside female
condoms and Truvada, an antiretroviral tablet taken by HIV negative people as
daily pre-exposure prophylaxis.
In 2015, South Africa and Kenya joined the US in approving Truvada. Pre-exposure prophylaxis has been proven
to be very effective for people at risk of HIV.
Studies
have shown that Truvada provides users with up to 90% protection provided it is
taken consistently. In earlier studies it was shown to be less successful in
women who did not take the drug daily.
Hurdles that need to be cleared
There are still
several more steps that need to be followed before the ring becomes available
to women.
Dapivirine was originally developed as an oral
antiretroviral compound. This was tested in phase- one and two clinical trials with more than 200 participants.
Although it was first conceived as an oral therapeutic,
dapivirine became a promising topical microbicide candidate because it was
effective both in vitro and in vivo, had a favourable safety profile, and the
right physical and chemical properties.
To licence the product, the ring must be approved for
public use by global and national regulatory authorities. Because at least two
phase three efficacy trials are needed for regulators to approve a licence for
the product, the two phase-three trials were conducted in parallel to speed up
the process to potentially approve the ring.
Licensure is an important but complex and timeous
process. The authorities will review the comprehensive dossier of scientific
evidence when deciding to licence the ring. The ring's developer, International
Partnership for Microbicides, a global health non-profit enterprise, will
follow this process.
Next round of studies
In the meanwhile, as the ring is under regulatory review,
there are several more studies planned. Two of the studies are open-label
extension (OLE) studies called DREAM and HOPE.
These
OLE studies aim to provide all women who participated in the phase-three trials
access to the dapivirine ring. This will help understand how the ring is used
in a real world setting now that the level of effectiveness is known and also
inform its future roll out. These studies are currently being reviewed by local
regulators.
A third study, MTN-034, that is also under review, will
offer women both the dapivirine ring and oral Truvada. Targeted at adolescent
girls and young women between the ages of 16 and 21, this study will help
understand what young women want and how they respond to the active products
once they know their levels of effectiveness.
This study is important because across both efficacy
trials, women aged 18 to 21 showed no significant protection because they did
not use the ring consistently. Young women aged 15 to 24 are at the highest risk of HIV infection
globally and so this is clearly an age group where research is needed.
But poor adherence may not be the only reason for the
lack of protection among these women. Further research is needed to understand
if there are biological or physiological factors that may affect how dapivirine
is taken up in vaginal tissue, or whether the trial design itself is especially
intimidating to young women.
Not knowing whether they are using an active product or a
placebo, or how safe and effective it is, may have influenced their use.
Disclosure statement
Thesla Palanee-Phillips receives funding from the
National Institutes of Health, DFID and USAID
Read the original article on The Conversation Africa.
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