NEW YORK -- AIDS activist Spencer Cox, who helped form an organization to boost treatment research and recently appeared in a documentary about an AIDS coalition, has died.

Cox, who was 44, died Tuesday at Allen Hospital in Manhattan of AIDS-related causes, according to his brother, Nick Cox.

Journalist and director David France said Spencer Cox can be seen in a documentary released this year about the activist group AIDS Coalition to Unleash Power called "How to Survive a Plague."

Cox joined the ACT UP group, known for its demonstrations and sit-ins and aggressive tactics seeking more resources for AIDS treatment and prevention, in 1989. He and other ACT UP members formed the Treatment Action Group, known as TAG, to focus on accelerating treatment research, in 1992.

France said Friday that Cox was "fiercely intelligent from the time he was a teenager."

"He wound up consulting with Nobel Prize winners on novel approaches to attacking viruses, rebuilding immune systems and designing drug trials," France said.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told The New York Times that Cox was always "very meticulous about getting good data rather than just screaming for getting something approved."

"It's a great loss," Fauci said. "He was part of a historic group of people."

A memorial will be held for Cox, who is survived by his brother and his mother, on Jan. 20 in New York.

Also on HuffPost: