Antivirals for Addressing XMRV Virus

With a recent study suggesting that two-thirds of people with chronic fatigue syndrome may test positive for a retrovirus called XMRV, a critical question arises. If this infection is indeed playing an important role in causing CFS symptoms, what can we do about it?

This new study is an important first step in answering this question. The researchers took the 10 most common AIDS drugs (AIDS and the XMRV virus are both retroviruses) and tested their effectiveness against XMRV. I found that I was holding my breath while waiting to get the answer to the question of what might work against XMRV. The result?

Of the 10 antivirals, the only one that showed any effectiveness against XMRV was an old antiviral called AZT ("Retrovir" being the brand name and the generic name being "zidovudine"). This medication has been around long enough that it is no longer under patent protection. This has the benefit of making the medication less expensive but also has the downside of making it less attractive for drug companies to spend research dollars on.

I would not recommend trying this medication at this time. Although it may become worth using if shown to be effective in chronic fatigue syndrome, without evidence of its effectiveness for this disease the medication is too toxic. To give you an idea of the concerns, here's the FDA-required black box warning in the Physician's Desk Reference under AZT (Retrovir/zidovudine):

WARNING

Retrovir (zidovudine) has been associated with hematologic toxicity including neutropenia and severe anemia particularly in patients with advanced human immunodeficiency virus (HIV) disease.

Prolonged use of Retrovir has been associated with symptomatic myopathy.

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination, including Retrovir and other antiretrovirals.

To put it in perspective though, AZT has been used safely in an enormous number of AIDS patients.

The bottom line? Although it may be helpful, and I consider this research study to be very important as a first step, I would not recommend being the first CFS patient on your block to try it. I would wait and let other people volunteer to be the guinea pigs. If we find that many people report it to be helpful, we will move this discussion to the next level.

Below is the abstract of the study.

Xenotropic Murine Leukemia Virus-Related Virus is Susceptible to AZT

Virology. December 1, 2009
Department of Molecular Medicine, Mayo Clinic, 200
First Street SW, Rochester, MN 55906, USA.
Sakuma R, Sakuma T, Ohmine S, Silverman RH, Ikeda Y

The xenotropic murine leukemia virus-related virus (XMRV) is a human retrovirus, recently isolated from tissues of prostate cancer patients with impaired RNase L activity.

In this study, we evaluated 10 licensed anti-HIV-1compounds for their activity against XMRV, including protease inhibitors (PI), nucleoside reverse transcriptase (RT) inhibitors (NRTI), non-nucleoside RT inhibitors (NNRTI) and an integrase inhibitor.

No PI affected XMRV production; even high concentrations of Ritonavir failed to inhibit the maturation of XMRV Gag polyproteins.

Among the NRTI, NNRTI and integrase inhibitors used in this study, only AZT blocked XMRV infection and replication through inhibition of viral reverse transcription.

This sensitivity of XMRV to AZT may be explained by the modest homology in the motif D sequences of HIV-1 and XMRV reverse transcriptases.

If XMRV becomes established as an etiological agent for prostate cancer or other diseases, AZT may be useful for preventing or addressing XMRV infections in humans.

PMID: 19959199 [PubMed — as supplied by publisher]. Reference: PubMed.gov.