• Extended Therapy with Subcutaneous Interleukin-2 (scIL-2) in HIV-Infection: Long-Term Follow-Up of 3 Trials (Poster 347)
  Authored by D. Chaitt, J. Metcalf, J. Kovacs, J. Falloon, M. Polis, J. Tavel, H. Masur, C. Lane, and R. Davey
  View the original abstract

Interleukin-2 (IL-2) has been shown to be beneficial in increasing CD4+ cell counts in HIV-infected patients. Given the marked problems with short-term tolerability, questions have remained regarding the long-term tolerability of IL-2. Further, whether the effects of IL-2 are durable in maintaining CD4+ cell counts has also remained an open question.

This study was an attempt by these investigators to answer the issues of long-term tolerability and durability of subcutaneous interleukin-2 (scIL-2) given in cycles and at relatively high-doses. The study evaluated 63 patients enrolled in three separate, prospective trials of scIL-2 plus antiretroviral therapy in patients with CD4+ cell counts in the moderate (200 cells/mL or greater) or high (500 cells/mL or greater) range. Follow-up treatment was being continued in all three of these trials with intermittent five-day cycles of scIL-2 at whatever doses and frequencies were required to maintain the CD4+ cell counts above baseline.

The enrolled patients have been treated with scIL-2 for a mean duration of 4.6 years. During that time, their mean CD4 cell counts had risen from 532 cells/mL to their current level of 1,030 cells/mL and their viral loads had declined from a baseline of 3.4 log10 copies/mL to a current level of 1.69 log10 copies/mL. The mean number of scIL-2 cycles received by these patients was 10 (range 3 to 28) and the patients had tolerated a mean dose of 11.9 million IU during their most recent cycle. The mean interval time since that cycle was 31 (range 7 to 60) months. As expected from their high CD4+ cell counts, no AIDS-defining events occurred in these patients.

The conclusions of the authors of this paper are that long-term scIL-2 is well tolerated and effective. To a limited extent, this data supports that conclusion; however, it is unclear whether the results hinged more on effective antiretroviral therapy or IL-2 administration. Further, the long-term tolerability remains unclear given the average interval of dosing in these patients was a little less than every four months, with the last dose given on average almost 2 and 1/2 years ago. This is an encouraging study, but is far from definitive regarding the issues raised. More research on the necessity and tolerability of this therapy would be helpful before it becomes routine clinical practice.