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Since 2017, a joint study between the Centers for Disease Control Prevention and the University of North Carolina has worked to develop an injectable implant that can release pre-exposure prophylaxis (PrEP) medications into the body for an extended period of time.

The latest research, published in Nature Communications, shows that the most recent formulation can provide up to six months of full protection against HIV in non-human primates.

“This is the first time we showed 100% protection against multiple virus challenges in a macaque model of PrEP over an extended period of time,” said Rahima Benhabbour, PhD, MSc, associate professor at the UNC/NCSU Joint Department of Biomedical Engineering in a statement. “Our goal with this technology is a once or twice-yearly injection that could be self-administered.”

Benhabbour and team have focused on refining the material contained in the injection, using cabotegravir, which is currently available as an injection every two months, as the main focus.

The formulation changes resulted in a significantly lower burst released of the drug, which Benabbour says “allows the drug to last longer in the body, provided that initial drug levels are enough to achieve protection.”

The results from the macaques, who have similar immune systems to humans, were “the cherry on top” for Benabbour and team. The macaques were challenged with simian HIV (SHIV) rectally, as rectal exposure is one of the most common means of HIV infection.

Six macaques were exposed to SHIV 38 times over several months, but none contracted it.

With the dosage determined effective in macaques, the next step is to see if the same dosage given to the macaques would also stay in the human body for at least 5.6 months.

The researchers and the CDC team currently await funding to move forward with the trial.