Given the suppression of viral load in AIDS patients that is being achieved by highly active antiretroviral therapy (HAART), attention is turning to stimulation of the immune system to restore immune function and reduce the latent viral reservoir in these patients. One possibility is Chiron Corp.'s Proleukin aldesleukin recombinant human interleukin-2 (IL-2), an immune stimulant that has shown positive Phase II data in increasing CD4 T cell counts while sustaining viral load reduction.

Proleukin is in two ongoing Phase III trials in combination with HAART - CHIR's 1400-patient SILCAAT trial and the NIH's 4000-patient ESPRIT trial. A BLA for the AIDS indication is not expected until CHIR has final results from its trial, which are due in 2006. Given that Proleukin is already marketed for metastatic renal carcinoma and metastatic melanoma, the product may receive off-label use before then. However physicians may have concerns about side effects with IL-2 therapy in AIDS patients.