IL-7 Trial Begins Recruiting

After a prolonged planning phase, the phase I/IIa trial of the immune-based therapy interleukin-7 (IL-7) has begun enrolling at multiple sites in the US, Canada and France (see the updated clinicaltrials.gov entry for details, including inclusion/exclusion criteria). IL-7 is a cytokine (immune system messenger protein) that plays a key role in maintaining naive and memory T cell numbers. The study is evaluating a new form of IL-7 designed to allow less frequent (once-a-week) dosing. Two prior phase I trials of IL-7 have been completed in people with HIV, results were presented at the CROI conference in 2007 and the presentations can be viewed via webcast. A follow-up poster from one of the trials was also presented at CROI in 2008. Overall, the results indicated that IL-7 was safe - in the relatively short-term - and led to significant increases in both naive and memory CD4 T cell numbers. The 2008 poster also reported some unexpected evidence of improved functionality of HIV-specific CD4 T cell responses. Because the new trial is primarily evaluating safety, people with low CD4 T cells despite viral suppression - the population most in need of immunological interventions - are not being included. 

Recent results from two large trials of a different cytokine, IL-2, showed that the CD4 T cell count increases produced by the approach did not confer benefit in terms of reducing the incidence of illness compared to people taking only antiretroviral therapy (ART). IL-7 works by a different mechanism than IL-2, but it remains unknown if CD4 T cell increased prompted by IL-7 treatment can benefit health. If the new form of IL-7 increases CD4 T cell counts to the same extent as seen in the prior phase I trials, and is found to be safe, additional studies will be required to evaluate the clinical impact of the approach.