Phase I clinical trial of experimental gene therapy to treat HIV shows encouraging results

Nov 8 2006

The results of a Phase I clinical trial of an experimental gene therapy aimed at treating HIV indicate that the therapy is safe and effective and also might sustain viral loads, according to a study published on Monday in the online edition of the Proceedings of the National Academy of Sciences, the AP/Washington Post reports.

According to the researchers, the Phase I trial results are encouraging enough for them to proceed with a more extensive Phase II trial, the AP/Post reports (Schmid, Washington Post, 11/6).

Carl June and Bruce Levine of the University of Pennsylvania's Abramson Family Cancer Research Institute and colleagues from the Gaithersburg, Md.-based Virxsys -- which is helping to develop the gene therapy treatment and fund the study -- over a nine-month period conducted the study among five HIV-positive people who had developed drug resistance, BBC News reports.

The study participants each received a single infusion of their immune system's CD4+ T cells.

The infusions contained about 10 billion T cells, which is between 2% and 10% of the total number of T cells in an average person's immune system.

The T cells were genetically modified to carry a manipulated version of HIV.

This modified version of the virus carried an antisense RNA molecule, which manipulates the process of reading genetic data so that the method HIV uses to reproduce itself inside infected cells is disrupted, according to BBC News (BBC News, 11/6).

The introduction of the RNA molecule in laboratory settings also has been shown to be an effective HIV therapy in treatment-naive cells, according to June.

The researchers found that the treatment stabilized or decreased viral loads in study participants over the course of the trial.

In addition, T-cell counts remained steady or increased in four of the five participants, according to the study.

The researchers also recorded a significant, continuous drop in HIV viral load in one study participant (AP/Washington Post, 11/6).

The researchers also were able to detect the modified cells in patients for several months following treatment, and in some cases they detected the modified cells several years after treatment (BBC News, 11/6).

The upcoming Phase II trial will involve 25 participants who will receive higher doses of the therapy, according to the Philadelphia Inquirer (McCullough, Philadelphia Inquirer, 11/7).

Some of the Phase II participants also will be receiving antiretroviral treatment, the AP/Post reports.

Following the infusion, the participants on standard antiretrovirals will be required to interrupt temporarily their treatment regiments to determine if the virus resurges. NIH's National Institutes of Allergy and Infectious Disease also is helping finance the study (AP/Washington Post, 11/6).

Reaction

"The goal of this Phase I trial was safety and feasibility, and the results established that," June said, adding, "But the results also hint at something much more."

According to Levine, although the study's findings indicate that the therapy "produced encouraging results in one or two patients doesn't mean it will work for everyone.

We have much more work to do" (BBC News, 11/6). According to Martin Haas -- a professor at the University of California-San Diego's School of Medicine who was not involved with the study -- the findings "should make quite some noise. ... I think they have really significant prospects to develop this into serious anti-HIV approaches for those patients in whom HIV cannot be kept under control by chemical means" (AP/Washington Post, 11/6).

Edwin Bernard, editor of the journal AIDS Treatment Update, said gene therapy likely will be a labor-intensive, costly treatment that might not be accessible to people living with HIV/AIDS in developing countries. He added that new drug treatments under development might provide an alternative (BBC News, 11/6).