[2] In 2001, he founded the "PharmAccess Foundation", a non-profit organisation based in Amsterdam which aims to improve access to HIV/AIDS therapy in developing countries, and he served as chairman until his death.

He argued that it is an "illusion to think that monotherapy with any antiretroviral agent will have a major and lasting impact on this disease" because the development of drug resistance significantly lowers the efficacy of treatment.

[9] In 1996, Lange defended the work of controversial HIV/AIDS researcher David Ho, who treated infected patients by having them swallow 20 pills a day as part of a multidrug "cocktail" regimen.

[10] Although this experiment was heavily criticised, Lange explained to The Wall Street Journal that "David's work in the past few years has helped to completely transform our understanding of HIV".

[10] Lange was also an important advocate for providing affordable AIDS medication to African countries, stating at one point that "(i)f we can get cold Coca-Cola and beer to every remote corner of Africa, it should not be impossible to do the same with drugs".

[11] During the 10th Conference on Retroviruses and Opportunistic Infections in Boston, Lange announced the results of a large multicenter clinical trial with the involvement of 1,216 patients in 17 countries.

[13] However, Lange was criticised for neglecting the needs of sex workers in the trials,[14] and other researchers asserted that the concerns raised by activists are "entirely legitimate" since the known toxic effects of so-called 'pre-exposure' drugs will lead to liver failure and kidney disease, thereby killing people rather than protecting them.

To mark the announcement of the institute, former US President Bill Clinton has shared a video message in which he honours Joep Lange's work and emphasises the importance of carrying forward his legacy.