The Sunday Times yesterday reported that HIV had become undetectable in the blood of one man taking part in the RIVER study, a trial of an intensive treatment regimen designed to test whether it is possible to reduce levels of HIV-infected cells in the bodies of people recently infected with HIV. The researchers hope that the treatment may eradicate HIV infection altogether.

The Sunday Times reported that British scientists are on the “brink of an HIV cure”. In fact, the study is still in its early stages and will not be able to describe participants as “cured” until extensive follow-up has taken place. Investigator Professor Sarah Fidler of Imperial College, London, told The Sunday Times that participants in the study will be followed for five years.

The RIVER study stands for ‘Research in Viral Eradication of HIV Reservoirs’. The trial is being conducted by the CHERUB Collaboration, a consortium of research teams at Imperial College and King’s College, London, Oxford University and Cambridge University, funded by the NHS National Institute for Health Research.

The study is recruiting people who were infected with HIV within the previous six months – so-called ‘primary infection’. HIV may have infected fewer cells in the body at this time, so in theory it might be easier to eradicate HIV in this group of people, or to stop antiretroviral therapy without causing a rebound in HIV levels.

Participants in the study receive a four-drug combination of antiretrovirals that includes raltegravir, which is included because it can reduce HIV levels in the blood more quickly than other antiretrovirals. Aggressive antiretroviral treatment started during primary infection has been shown to permit treatment to be stopped altogether, without viral rebound, in around 15% of people in a French cohort study called VISCONTI.

After 22 weeks of antiretroviral treatment, participants in the study are randomly assigned to continue receiving the four-drug antiretroviral regimen alone, or to receive the antiretroviral regimen plus a vaccination designed to improve immune responses to HIV-infected cells. Participants in this study arm also receive ten doses of vorinostat, a drug which activates cells infected with HIV.

If the experimental regimen is effective, vorinostat should ‘kick’ cells latently infected with HIV to produce HIV. The surge in virus production as a result of activation will be suppressed by the highly effective antiretroviral drug combination. The infected cells should be spotted by the immune system and the vaccination should improve the ability of the immune system to seek out and kill the infected cells. This “kick and kill” strategy – ten rounds of vorinostat over 28 days – is designed to flush out the infected cells and kill them, leaving little or no HIV DNA left in the body.

The study is designed to test whether the approach does indeed reduce levels of HIV DNA in cells, or even eradicates the infection altogether. The study is measuring HIV DNA levels 40 and 42 weeks after treatment begins, but is not testing whether treatment can be stopped altogether after 42 weeks.

The RIVER study aims to recruit 52 people diagnosed with primary HIV infection. Recruitment is taking place at clinics in London and Brighton.

The Sunday Times reported that one participant in the study has no detectable HIV after completing the study regimen. This participant continues to take antiretroviral therapy (ART). This participant has not been cured of HIV infection at this point: prolonged follow-up will be needed to determine whether the virus has been eradicated entirely by the experimental treatment.

Professor Sarah Fidler of Imperial College, London, told The Sunday Times: “We will continue with medical tests for the next five years and at the moment we are not recommending stopping ART but in the future depending on the test results we may explore this.”

The RIVER study is not due to complete tests on all participants until December 2017, so the earliest that any results from the study will be available is likely to be the first half of 2018. At that stage the researchers will be able to say whether or not the experimental regimen eliminated all traces of HIV DNA in study participants. But the real test of an eradication regimen will be to see what happens when treatment is stopped.

To date, the only person who appears to have been cured of HIV infection is Timothy Ray Brown, the so-called ‘Berlin patient’ who lost all evidence of HIV infection after a bone marrow transplant. A more recent study of similar bone marrow transplant recipients with HIV identified people who had undetectable viral load, and no detectable HIV DNA in their cells, who have nevertheless experienced viral rebound after treatment was stopped – sometimes after a long interval. Long-term follow-up will be essential for anyone who stops treatment, in order to determine whether HIV has been truly eradicated from the body.

Whether participants stop treatment after the end of the study, assuming that the regimen is successful in making HIV DNA undetectable, will be a matter for discussion between investigators and study participants, and will depend on the best available information at the time about the consequences of stopping treatment. In other words, it is very premature to report a cure breakthrough.