NSW health minister Jillian Skinner announced 3700 places would be made available for gay men in a new trial of the drug, which is currently not listed on the federal government's pharmaceutical benefits scheme.

The trial, which is set to begin in early 2016, will dramatically increase the number of gay men who currently have access to pre-exposure prophylaxis (PrEP), and is expected to dramatically reduce the number of new HIV diagnoses in NSW.

The move has been hailed as a "game changer" by Nicolas Parkhill, CEO of ACON, the HIV prevention, HIV support and LGBTI health organisation.

"Here in NSW, the project will play a vital role in helping us realise our goal of eliminating HIV transmission by 2020. As a result of this initiative, 3700 people at high risk of HIV transmission will soon be much better protected from acquiring HIV," he said.

"When we combine this with our increasing rates of HIV testing among gay men and stronger uptake of treatment among people with HIV, we have the potential to deliver the biggest reduction in HIV transmission rates in NSW for more than 20 years. This is an incredibly exciting development in terms of the HIV prevention landscape."