One of the stories coming out of this year?s Conference on Retroviruses and Opportunistic Infections (CROI), is the long awaited results from SILCAT and ESPRIT- the two large, long term studies of the immune based therapy IL-2. The basic findings were that, while IL-2 predictably increased CD4 counts, it did not improve outcomes.

IL-2 was long seen as the best chance for an immune based therapy for HIV. It has long been known to increase CD4 counts, but questions remained about whether those CD4s would translate to better health outcomes.

These studies fairly clearly show no real benefit to taking IL-2. People taking IL-2 had higher CD4 counts, but no significant differences were seen in rates of illness or death.

So, is IL-2 dead? Probably. The company that own IL-2- or Proleukin, Novartis, has been indicating for some time that they were very unlikely to file with the FDA for an HIV indication, even if the results were favorable. Now that they aren?t, it will make their decision easier.

I still think there might be a role for IL-2 in HIV, or maybe roles. First, I think it might be useful for people able to control HIV replication, but who do not experience good increases in CD4 count. There have also been some intriguing studies of IL-2 as part of early treatment and treatment interruptions.

Chances are that little new research will be done- at least not of the type needed to really understand the potential of this drug.

More importantly, this is yet another body-blow to the prospects for immune based therapies in HIV. It is really difficult to get pharmaceutical companies interested in these interventions, and now I fear it will be next to impossible.