A trial with 17 HIV-positive patients yielded a "statistically significant decrease" in the virus, biotech firm Bionor announced.
"This is a major achievement on the path to a functional cure for HIV," Bionor spokesman Jorgen Fischer Ravn told news agency AFP.
There is no cure for the disease AIDS, caused by HIV. but anti-retroviral treatments help people live longer, healthier lives by delaying and subduing symptoms.
In some who undergo treatment, however, the virus takes cover in cells and hides away, only to reemerge once therapy is stopped.
This latency has been one of the biggest hurdles in developing a cure.
"Waking up" the virus and then destroying it -- the so-called "kick-and-kill" approach -- is a promising strategy for ridding patients of HIV.
Bionor's approach involves an anti-cancer drug called romidepsin to wake up the dormant HIV, and a vaccine called Vacc-4x to prime the body's own immune T-cells to recognise and destroy the virus.
"After an activation of the virus, which would normally lead to detectable virus in the blood, Vacc-4x ensured killing of the virus-producing cells to maintain non-detectable or very low levels of virus in the blood in 15 out of 17 patients," said Fischer Ravn.
No-one has yet been cured of AIDS.
Thirty-nine million people have died of AIDS, according to UN estimates, and about 35 million are living with the immune system-destroying virus today, overwhelmingly in poor countries.