Doctors on Tuesday at the 23rd International AIDS Conference reported on a Sao Paulo man who has been in HIV remission for more than 15 months following an experimental drug therapy.

Scientists cautioned it was way too early to discuss a possible cure.

The 35-year-old man took part in a clinical trial with four other people who were HIV positive. Only he achieved HIV remission. A similar 30-person trial based on related approaches also did not succeed.

“This happened to one person, and one person only,” said Dr. Monica Gandhi, who specializes in AIDS at the University of California, San Francisco.

The Brazilian man joined the clinical trial in September 2015. Added to his standard three-drug cocktail were dolutegravir, maraviroc, and nicotinamide, a form of vitamin B3 that is believed to reactivate dormant HIV.

After nearly a year, he returned to his standard drug combination for two years. In March 2019, he stopped taking all HIV medicines. His virus load has been undetectable since then.

Two men are believed to be cured of HIV. The London Patient and the Berlin Patient went into long-term remission after each received a bone marrow transplant to treat leukemia or lymphoma from a donor with a rare genetic mutation. This procedure is expensive and dangerous.

Dr. Ricardo Diaz of the University of Sao Paulo said that he believes the Brazilian man “might be cured” but warned it was too early to tell.

Similar stories about viral suppression have ended in disappointment. An example would be the Mississippi baby who was “cured” for more than two years before her virus rebounded.