AIDS activist Spencer Cox died on Tuesday. He was 44 years old.

According to GLAAD, Cox died at Columbia Presbyterian Hospital in New York City of causes related to AIDS.

Cox had been involved in AIDS-related activism for over 20 years. He was involved in AIDS Coalition To Unleash Power (ACT UP) and was a co-founder of the Treatment Action Group (TAG).

David France, who produced and directed the documentary How To Survive A Plague, a film which looks at the rise and success of HIV/AIDS advocacy groups ACT UP and TAG and features Cox, spoke of Cox's role in the fight against the disease.

“As a very young man fresh from Bennington, where he studied Theater and English Literature, he arrived in NYC after finishing just 3 years,” France told BuzzFeed.com. “He was diagnosed with HIV soon thereafter. By 1989, at age 20, he had become spokesman for ACT UP during its zenith through the early 90s. A member of its renowned Treatment & Data committee, and later co-founder of TAG (the Treatment Action Group), he schooled himself in the basic science of AIDS and became something of an expert, a 'citizen scientist' whose ideas were sought by working scientists. In the end, Spencer wrote the drug trial protocol which TAG proposed for testing the promising protease inhibitor drugs in 1995. Adopted by industry, it helped develop rapid and reliable answers about the power of those drugs, and led to their quick approval by the FDA.”

“You live your life as meaningful as you can make it,” Cox said in an outtake from France's film which the director posted on Tuesday. “You live it and don't be afraid of who is going to like you or are you being appropriate. You worry about being kind. You worry about being generous. And if it's not about that, what the hell's it about?” (The video is embedded on this page. Visit our video library for more videos.)