How is PML treated or prevented?

Unfortunately, there are no treatments that have been proven to be effective for PML. A handful of drug treatments have been studied in clinical trials, but results have been disappointing. Examples of treatments tested in clinical trials include cytosine arabinoside (Cytosar-U, DepoCyt), topotecan (Hycamtin), cidofovir (Vistide), and high-dose intravenous zidovudine (Retrovir). Some proved to be too toxic to use, while others failed to improve symptoms or survival.

The medications cyproheptadine (Periactin) and mirtazapine (Remeron), typically used to control psychotic symptoms such as hallucinations and delusions, have been studied with encouraging results in test-tube studies (clinical trials are necessary to evaluate their effectiveness and safety in humans with PML). There have also been encouraging results using interferon-alfa, an injectable medication frequently used to treat various viral infections.

Even without the availability of approved treatments for PML, there are still encouraging options available. Combination ARV therapy has been shown to be extremely beneficial for HIV-positive patients with PML. Because PML is most likely to occur in patients with suppressed immune systems—and ARV therapy has been shown to significantly increase CD4 cell counts and the general health of the immune system—HIV-positive patients with PML are more likely to live longer and to see their symptoms improve, sometimes dramatically. A significant number of people on ARV therapy may still develop PML and have disease progression, however, but emerging evidence suggests that such individuals may benefit from "intensifying" their ARV therapy by adding other drugs to which their virus is sensitive.

Many researchers agree that HIV-positive patients with PML should use HIV drugs that are known to cross the "blood-brain barrier"—a protective coat that lines blood vessels in the brain to prevent toxins from passing through. Many of the nucleoside analogues, especially zidovudine (Retrovir) and abacavir (Ziagen), and the non-nucleoside analogues, particularly nevirapine (Viramune), easily pass through the blood-brain barrier, and are often used to treat patients with other HIV-related brain diseases. If zidovudine is used to help treat PML, some experts suggest that a daily dose of 1,000 to 1,200 mg (twice the regular zidovudine dose) be used.

A syndrome—called immune reconstitution inflammatory syndrome (IRIS)—where antiretroviral treatment can actually exacerbate the symptoms of an opportunistic infection due to a strengthened immune response, has been commonly reported with PML. Some providers use corticosteroids preventatively for a short period when starting ARV therapy in people who've been diagnosed with PML.

Can PML be prevented?

No, not at the present time. But because immune suppression plays a major role in the development of PML, the best possible way to prevent this disease is to keep the immune system healthy. This includes starting ARV therapy before the immune system becomes impaired. If a person has gone into remission after starting ARV therapy, the chance is quite low that they will have a recurrence of the disease.

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