Tue Jul 1

We have drugs to manage HIV. So why are we spending millions looking for cures?

Written by Bridget Haire, Associate Professor, Public Health Ethics, School of Population Health, UNSW Sydney

Over the past three decades there have been amazing advances in treating and preventing HIV.

It’s now a manageable infection. A person with HIV who takes HIV medicine consistently, before their immune system declines, can expect to live almost as long as someone without HIV ^[1].

The same drugs prevent transmission ^[2] of the virus to sexual partners.

There is still no effective HIV vaccine ^[3]. But there are highly effective drugs ^[4] to prevent HIV infection for people without HIV who are at higher risk of acquiring it.

These drugs are known as as “pre-exposure prophylaxis” or PrEP ^[5]. These come as a pill, which needs to be taken either daily, or “on demand ^[6]” before and after risky sex. An injection ^[7] that protects against HIV for six months has recently been approved in the United States ^[8].

So with such effective HIV treatment and PrEP, why are we still spending millions ^[9] looking for HIV cures?

Not everyone has access to these drugs

Access to HIV drugs and PrEP depends on the availability of health clinics, health professionals, and the means to supply and distribute the drugs. In some countries, this infrastructure may not be secure.

For instance, earlier this year, US President Donald Trump’s dissolution of the USAID foreign aid program ^[10] has threatened the delivery of HIV drugs to many low-income countries.

This demonstrates the fragility of current approaches to treatment and prevention. A secure, uninterrupted supply of HIV medicine is required, and without this, lives will be lost and the number of new cases of HIV ^[11] will rise.

Another example is the six-monthly PrEP injection just approved in the US. This drug has great potential for controlling HIV if it is made available and affordable in countries with the greatest HIV burden.

But the prospect for lower-income countries accessing this expensive drug looks uncertain, even if it can be made at a fraction of its current cost, as some researchers say ^[12].

So despite the success of HIV drugs and PrEP, precarious health-care systems and high drug costs mean we can’t rely on them to bring an end to the ongoing global HIV pandemic. That’s why we also still need to look at other options.

Haven’t people already been ‘cured’?

Worldwide, at least ^[13] seven people ^[14] have been “cured” of HIV – or at least have had long-term sustained remission. This means that after stopping HIV drugs, they did not have any replicating HIV in their blood for months or years.

In each case, the person with HIV also had a life-threatening cancer needing a bone marrow transplant. They were each matched with a donor who had a specific genetic variation that resulted in not having HIV receptors in key bone marrow cells.

After the bone marrow transplant, recipients stopped HIV drugs, without detectable levels of the virus returning. The new immune cells made in the transplanted bone marrow lacked the HIV receptors. This stopped the virus from infecting cells and replicating.

But this genetic variation is very rare ^[15]. Bone marrow transplantation is also risky and extremely resource-intensive ^[16]. So while this strategy has worked for a few people, it is not a scalable prospect for curing HIV more widely.

So we need to keep looking for other options for a cure, including basic laboratory research to get us there.

How about the ‘breakthrough’ I’ve heard about?

HIV treatment stops the HIV replication that causes immune damage. But there are places in the body where the virus “hides” and drugs cannot reach. If the drugs are stopped, the “latent” HIV comes out of hiding and replicates again. So it can damage the immune system, leading to HIV-related disease.

One approach is to try to force the hidden or latent HIV out into the open, so drugs can target it. This is a strategy called “shock and kill”. And an example of such Australian research was recently reported in the media as a “breakthrough ^[17]” in the search for an HIV cure.

Researchers in Melbourne have developed a lipid nanoparticle – a tiny ball of fat – that encapsulates messenger RNA (or mRNA) and delivers a “message” to infected white blood cells. This prompts the cells to reveal ^[18] the “hiding” HIV.

In theory, this will allow the immune system or HIV drugs to target the virus.

This discovery is an important step. However, it is still in the laboratory phase of testing, and is just one piece of the puzzle.

We could say the same about many other results ^[19] heralded as moving closer to a cure for HIV ^[20].

Further research on safety and efficacy is needed before testing in human clinical trials. Such trials start with small numbers and the trialling process takes many years. This and other steps towards a cure are slow and expensive, but necessary.

Importantly, any cure would ultimately need to be fairly low-tech to deliver for it to be feasible and affordable in low-income countries globally ^[21].

So where does that leave us?

A cure for HIV ^[22] that is affordable and scalable would have a profound impact on human heath globally, particularly for people living with HIV ^[23]. To get there is a long and arduous path that involves solving a range of scientific puzzles, followed by addressing implementation challenges.

In the meantime, ensuring people at risk of HIV have access to testing and prevention interventions – such as PrEP and safe injecting equipment – remains crucial. People living with HIV also need sustained access to effective treatment – regardless of where they live.