A large clinical trial in South Africa and Uganda has shown that a twice-yearly injection of a new pre-exposure prophylaxis drug gives young women total protection from HIV infection.

The trial tested whether the six-month injection of lenacapavir would provide better protection against HIV infection than two other drugs, both daily pills. All three medications are pre-exposure prophylaxis (or PrEP) drugs.

Physician-scientist Linda-Gail Bekker, principal investigator for the South African part of the study, tells Nadine Dreyer what makes this breakthough so significant and what to expect next.

The Purpose 1 trial with 5,000 participants took place at three sites in Uganda and 25 sites in South Africa to test the efficacy of lenacapavir and two other drugs.

Lenacapavir (Len LA) is a fusion capside inhibitor. It interferes with the HIV capsid, a protein shell that protects HIV’s genetic material and enzymes needed for replication. It is administered just under the skin, once every six months.

The randomised controlled trial, sponsored by the drug developers Gilead Sciences, tested several things.

The first was whether a six-monthly injection of lenacapavir was safe and would provide better protection against HIV infection as PrEP for women between the ages of 16 and 25 years than Truvada F/TDF, a daily PrEP pill in wide use that has been available for more than a decade.

Secondly, the trial also tested whether Descovy F/TAF, a newer daily pill, was as effective as F/TDF. The newer F/TAF has superior pharmacokinetic properties to F/TDF. Pharmacokinetic refers to the movement of a drug into, through, and out of the body. F/TAF is a smaller pill and is in use among men and transgender women in high-income countries.

The trial had three arms. Young women were randomly assigned to one of the arms in a 2:2:1 ratio (Len LA: F/TAF oral: F/TDF oral) in a double blinded fashion. This means neither the participants nor the researchers knew which treatment participants were receiving until the clinical trial was over.

In eastern and southern Africa, young women are the population who bear the brunt of new HIV infections. They also find a daily PrEP regimen challenging to maintain, for a number of social and structural reasons.

...continued