The addition of Vistide (cidofovir) to antiretroviral (ARV) therapy did not slow disease progression or prevent death in HIV-positive people with progressive multifocal leukoencephalopathy (PML), according to a study published in the September 1 issue of AIDS.

PML, caused by the JC virus (JCV), is a rare disease that causes brain lesions. In the years before effective ARV therapy became widely available, PML eventually developed in 3 to 7 percent of HIV-positive people and almost always led to a rapid loss of mental and physical functioning and ultimately death. While strengthening the immune system through ARV treatment is the most effective treatment for PML, some scientists hoped that Vistide—an antiviral medication used to treat cytomegalovirus (CMV) infection—may also help.

Andrea De Luca, MD, from the Institute of Clinical Infectious Diseases at the Catholic University of Sacred Heart in Rome, and her colleagues compared the medical records of 370 people with HIV who had been diagnosed with PML since 1996 and treated with ARV therapy. Half of the patients also received Vistide, and half did not. Most of the patients treated with Vistide received five total intravenous infusions given once every two weeks.

Dr. De Luca’s team found that the proportion of people still living one year after the initial PML diagnosis was actually somewhat lower in the group treated with Vistide (51 percent), than the group not treated with Vistide (56 percent). This difference, however, was not statistically significant, meaning that it was small enough to have occurred by chance.  

When the team looked at Vistide’s impact on degree of disability in people still living at one year after diagnosis, they found that as with survival, Vistide conferred no benefit. In fact, people receiving Vistide were somewhat more likely to be moderately to severely disabled one year after diagnosis than people not receiving Vistide.

The authors acknowledge the possibility that Vistide may have preferentially been given to people who were sicker with PML, which would skew the data in such a way that it would have been much harder to show a benefit from Vistide treatment. They also point out, however, that their study is much larger than any other performed to date with Vistide and PML and that the results are in agreement with another smaller study that failed to find any benefit from Vistide treatment.