Study Objectives. To assess the pharmacokinetics and pharmacodynamics of subcutaneously administered interleukin‐2 (IL‐2) in patients infected with the human immunodeficiency virus (HIV).

Design. Open, dose‐escalating phase I clinical trial.

Setting. Government research hospital.

Patients. Eighteen patients infected with HIV.

Interventions. Recombinant IL‐2 at dosages of 12, 15, or 18 MIU/day was administered subcutaneously once or twice/day for 5 consecutive days every 2 months. A total of 28 cycles of therapy were included in the analysis.

Measurements and Main Results. Concentrations of IL‐2 in serum were determined by a commercial enzyme‐linked immunosorbent assay. Interleukin‐2 was well absorbed, with peak concentrations from 21.9–112.9 IU/ml. Absorption was slow, with mean (± SD) time to maximum of 4.4 ± 1.8 hours and a lag time of 26.9 ± 13.7 minutes. Elimination half‐life was 3.3 ± 0.9 hours. The concentrations had wide variability both within and among patients. Levels of tumor necrosis factor‐α were increased. Maximum body temperature and systemic side effects were associated with peak serum levels.

Conclusion. Interleukin‐2 is well absorbed after subcutaneous injection in HIV‐infected patients, and that route of administration is an alternative to intravenous infusions.