Benefits of Il-2 Interleukin-2
Mar 5, 2005
Congratulations on a study that can contribute to the immune health of HIV patients.
Your paper at CROI showed that after a median follow-up time of 78 weeks during a treatment interruption, CD4+ cell counts were higher in those who received IL-2 for the first 72 weeks.
I am confused by the summary that thebody ran however.
Prior to week 72, the benefit of IL-2 appeared to prolong the success of this strategy (i.e., time off antivirals) by about 20 weeks. However, after week 72, the groups appeared to have similar outcomes in terms of counts going below 350 cells/mm3.
Is this saying that prior to week 72 more people not on IL-2 had to go on back on HAART, but after week 72 the people on IL-2 had to go back on HAART in so much larger numbers that they "caught up" and so by say week 78 equal numbers of Il-2 and non IL-2 patients were back on therapy? Or is it saying that up to week 72 the IL-2 patients did better at staying off therapy and between say week 72 and week 78 or week 90 equal numbers went back on therapy?
Either way, Dr Cohen's interpretation seems misleading. He concluded that "the majority of people in this study had no obvious benefit reported at this timepoint".
Clearly if people on IL-2 last longer ON AVERAGE off therapy up to week 72 that is a benefit of increased time off therapy, even if the people on IL-2 also have to go back on therapy after week 72.
Also, as 70% of the people were still off therapy at week 72, the study obviously did not last long enough to show larger differences As your median follow-up time was 78 weeks why didn't you say what percentage were off therapy at 78 weeks?
The study seems obviously more encouraging to thosewho have hope for IL-2 than the summary suggests.
Response from Dr. Henry
Even at 72 weeks the group receiving IL-2 had a higher CD4 count but it was not statistically significant. The good news was that a high percentage of participants in both arms (IL-2 or control) were doing well off therapy after 72 weeks. The more important result from our study was that the CD4 nadir (how low did it go before starting HIV therapy) influenced the time off therapy (the lower the CD4 count then the more rapidly the CD4 count fell and reached 350) as did how high the viral load went after stopping (the higher the viral load after stopping went the more rapid the patient had to go back on treatment). Take home messages include that treatment interruptions strategies would likely work better if HAART started with highert CD4 counts (> 350) and if an intervention (such as therapeutic vaccine) could blunt the viral rebound off therapy---topics worthy of further study. KH
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