Supported by our in vitro and in vivo primaquine anti-tumor efficacy and safety findings in PEL cells and mouse models, and also by the fact that primaquine has been used worldwide since the 1950s with remarkable tolerance among glucose 6-phosphate dehydrogenase (G6PD)-normal patients [41], an exploratory proof of concept clinical trial on Kaposi’s sarcoma was conducted. Here, G6PD is linked to Kaposi's sarcoma.