Researchers have unveiled the results of the first ever human trial of what could be a game-changing HIV prevention tool.
At this week’s International Aids Society conference in Mexico City researchers presented the preliminary results of a trial of a pre-exposure prophylaxis (PrEP) implant that could prevent someone from contracting HIV for up to a year.
PrEP is currently available as a pill and has been shown to reduce the chances of picking up HIV through unprotected sex by about 90 per cent. It is seen as a key weapon in the global fight against the disease.
However, the pill needs to be taken daily and sticking to a regular drug regime is hard. A review of 18 studies looking at adherence to PrEP found widely differing rates - with one reporting that just 24 per cent of participants stuck to the regime.
An implant that only needs to be replaced every 12 months could be a powerful prevention tool, particularly in sub Saharan Africa where the rate of new HIV infections is still high and PrEP take-up has been low.
The study trialled the implant in 16 healthy volunteers over a course of 12 weeks - 12 people were fitted with a stent the size of a match which slowly released a dose of islatravir, a new HIV drug formulation developed by the pharmaceutical company MSD, a UK division of Merck. Four people were fitted with a placebo.
Initial results show that the implant was generally well tolerated and that it could deliver a dose at the right level over a 12-month period.
The company is looking at several options for islatravir as a prevention tool - including as a once-monthly pill and will begin trials in September.
Brenda Crabtree-Ramirez, co-chair of the International Aids Society and assistant professor at the National Autonomous University in Mexico, said there was an urgent need for new tools to increase adherence to PrEP.
She added: "These early findings suggest promise and should encourage continuous trials to assess longer term results. A PrEP implant could change the face of HIV prevention."
Dr Mark Lawton, an HIV and sexual health consultant in Liverpool and a spokesperson for the British Association of Sexual Health and HIV, said that a PrEP implant could be a powerful tool in the fight against Aids and HIV.
“PrEP has been a game changer in the prevention of HIV. For the first time we are seeing a reduction in diagnoses of HIV - certainly in the UK - and that is related to PrEP,” he said.
But he added that PrEP in its current pill form had drawbacks.
“It’s reliant on people taking the medication. The oral contraceptive pill came along in the 1950s and it was a big success but a victim of stigma. Compliance with the oral contraceptive pill is an issue and sexual health clinics will encourage young women to have long-acting reversible contraception such as an injection, an intrauterine device or an implant,” he said.
Dr Lawton said that a year-long implant would have a big impact on cost as it would mean that people taking the drug would not have to come in every three months as UK guidelines state currently.
“And in parts of Africa where access to healthcare is poor this could be beneficial,” he said.
But the introduction of PrEP has been linked to a rise in sexually transmitted infections. A recent report into the increase in syphilis in Europe said that the reduced fear of contracting HIV - in part driven by PrEP - was behind an increase in risky sexual behaviour.
Yusuf Azad, director of strategy at the National Aids Trust, said that there was little hard evidence that the introduction of PrEP was to blame for an increase in STIs.
“There had been a very steep increase in STIs across the world well before and separate to the introduction of PrEP. The challenge of how we address STI transmission in a world where HIV is less acute as an issue is one we have to face. But for too long we have relied on the fear of HIV as a way of controlling the spread of STIs,” he said.
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