Trial to Impact

The Latest Insights on CAB for PrEP

November 22, 2024

The Biomedical Prevention Implementation Collaborative (BioPIC) is leading an integrated and adaptable strategy to deliver new long-acting HIV prevention products, including injectable cabotegravir (CAB) for PrEP. The HIV prevention products that exist today hold the potential to curb incidence, but their impact relies on stronger coordination to ensure they reach those who need them most. BioPIC unites a group of over 100 diverse stakeholders—civil society, donors, researchers, policymakers, implementers, and normative agencies like WHO and UNAIDS—across more than 20 countries to address these challenges. To support this, BioPIC introduced the Adaptable Product Introduction Framework, emphasizing the need to conduct early-stage activities alongside phase III clinical trials, and conducts Think Tanks to pinpoint evidence gaps and share insights from modeling and implementation studies. This work is driving more effective, people-centered product delivery, and is described in this article with colleagues at WHO: Shaping and coordinating the implementation science agenda for injectable cabotegravir for PrEP: the role of the Biomedical Prevention Implementation Collaborative (BioPIC).

To ensure lessons around early CAB for PrEP implementation are consolidated and captured, AVAC developed the CAB for PrEP Priority Evidence Gap Tracker, which tracks progress against addressing the highest priority CAB for PrEP evidence gaps identified in BioPIC Think Tanks. As data from the open label extension studies of the two CAB for PrEP Phase III trials, HPTN 083 and 084, as well as early implementation studies and modelling studies, has begun to emerge, AVAC has continued to update the tracker, with some of the latest major insights summarised below.

Rapid testing is the right choice for CAB for PrEP initiation and continuation

CAB is from a class of antiretrovirals called integrase strand transfer inhibitors (INSTIs), the same class as dolutegravir (DTG), a common first-line HIV treatment. There is a risk that people using CAB for prevention could develop resistance to INSTIs, which could compromise the effectiveness of DTG as treatment. Preventing the development of INSTI resistance is, therefore, a high priority for CAB for PrEP implementers. Resistance may develop if a person living with HIV (but unaware of their status) initiates CAB for PrEP or continues to use it after a breakthrough infection, so implementers need to feel confident in the results of HIV tests used at initiation and continuation visits. During the initial stages of programmatic rollout of CAB, there were questions as to whether rapid HIV tests were sensitive enough to be used for this purpose, or if more expensive, lab-based RNA testing would be required. After reviewing emerging evidence, WHO confirmed that rapid diagnostic tests can be used for CAB for PrEP initiation and continuation. Moreover, the HPTN 083 study team concluded that RNA testing performed poorly as a screening tool for CAB for PrEP continuation, as it led to false positives.

CAB for PrEP is safe to use during pregnanc

The HPTN 084 trial of CAB for PrEP amongst cisgender women included a requirement for participants to use contraception while enrolled in the trial, and participants who did become pregnant were immediately discontinued from CAB for PrEP. This meant that at the end of the trial, researchers were unable to conclude whether CAB for PrEP was safe and effective to use during pregnancy. The open label extension phase of the trial removed these restrictions, and with this new data, the HPTN 084 team has been able to confirm that CAB for PrEP is safe and well-tolerated in pregnancy. Delay in confirming this has led to confusion amongst implementers and variation across countries in whether CAB for PrEP is permitted for use in pregnancy, highlighting the importance of including pregnant and lactating people in clinical trials from the start, as has been done in the PURPOSE 1 trial of lenacapavir.

Offering choice increases PrEP uptake

For the first time, PrEP users in an increasing number of countries have the ability to choose from an array of options, including oral PrEP, CAB for PrEP, and the dapivirine vaginal ring.  The SEARCH study, in Kenya and Uganda, looked at the impact of choice on PrEP coverage, by comparing two groups of PrEP users: one offered the choice of oral PrEP or post-exposure prophylaxis (PEP), and the second offered oral PrEP, PEP, or CAB for PrEP.  Researchers found a highly significant impact, with PrEP coverage reaching 70% in the group whose options included CAB for PrEP, compared to 13% in the group offered only oral PrEP or PEP. 56% of users in the group offered CAB for PrEP took it up, and 42% of those who chose CAB for PrEP were not using any HIV prevention method at the time, demonstrating that adding more options can bring in more users as people are able to find products that better suit their preferences. Even more importantly, HIV incidence in the group offered CAB for PrEP was 0, compared to 1.8% in the other group. In addition to demonstrating the impact of choice in product, the SEARCH study demonstrated the impact of choice in delivery channel, by successfully offering a variety of HIV prevention options via outpatient facilities, antenatal clinics, and community health workers going door-to-door.

What’s next?

There are currently 31 ongoing CAB for PrEP implementation studies, all looking at different aspects of CAB for PrEP delivery among different populations across geographies. As interim insights continue to emerge from these studies, AVAC will continue to track them.  Check back regularly on the PrEPWatch Events page for webinars where these insights will be shared.

Resources

Think Tanks