Cell Genesys is an American company developing a gene therapy treatment for HIV. It involves genetically modifying cells so that once returned to the body they recognise and destroy HIV-infected cells.

An initial trial conducted at the US National Institute of Allergy and Infectious Diseases recruited identical twins, one of whom was infected with HIV. Cells from the uninfected twin were modified by gene therapy and used to treat the infected twin. Initial results found no treatment-related safety problems, and the transfused cells appeared to persist in the body.

In a second trial, participants own CD4 cells will be collected, genetically modified and returned to them. Participants will also receive anti-HIV drugs.