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This past spring,
Dr. Ila Singh at the
University of Utah conducted one of three recent studies testing HIV
antiretrovirals against XMRV
in vitro
(in the test tube). Singh
discovered that two drugs—tenofovir and raltegravir—killed the XMRV retrovirus,
and corroborated an earlier study by the Mayo Clinic
that concluded that AZT is also effective against XMRV. In addition, Singh found any two
combinations of these three drugs were synergistic. She didn’t test all three drugs together, so it’s not known
if a triple cocktail would be even more effective. It’s also possible that the triple cocktail could be less effective than a two-drug combo.
Nucleoside
Analogue Reverse Transcriptase Inhibitors
Zidovudine (brand name AZT). FDA-approved in 1987, AZT was the first drug used to treat
HIV/AIDS, though it was developed in the 1960s as a cancer drug. In 1974, German scientist Max Planck
discovered that AZT was active against a mouse retrovirus called Friend murine
leukemia virus, a close cousin of XMRV.
In HIV, AZT works by stopping the enzyme reverse transcriptase
from converting the retrovirus’s RNA into DNA, which is then integrated into
the genetic material of the host’s cells. Normally DNA transcribes (converts)
RNA. Reverse transcription is the
reverse: RNA transcribes DNA. Nucleoside
analogue reserve transcriptase inhibitors are often abbreviated NRTIs.
Common side effects of AZT
include: nausea, loss of appetite, headache, tiredness, vomiting,
constipation, asthenia (weakness).
Less common side effects: anemia, bone-marrow suppression,
bruising, muscle pain and myopathy (muscle weakness), mitochondrial toxicity
and lactic acidosis, body-fat redistribution, elevated liver enzymes and liver
damage, a bluish discoloration of fingernails and toenails, and allergic
reactions. Nausea is the most
common side effect from AZT and can be minimized by taking the drug with
food. However, high-fat meals tend
to exacerbate the nausea.
Nucleotide
Analogue Reverse Transcriptase Inhibitors
Tenofovir (brand name Viread). Nucleoside analogs are converted into nucleotide analogs by the body. If you take nucleotide analog
reverse transcriptase inhibitors (often abbreviated NtRTIs), you bypass that
step. FDA-approved in 2008,
Tenofovir, like AZT, blocks the retroviral attack on the host’s healthy cells
by preventing the reverse transcriptase enzyme from doing its job of transcribing single-stranded viral RNA
into double-stranded viral DNA.
Common side effects of tenofovir
include: diarrhea, headache, pain,
depression, rash, asthenia (weakness), nausea. Less common side effects: vomiting,
gas, loss of appetite, weight loss, insomnia, dizziness, sweating, muscle pain
and myopathy (muscle weakness), mitochondrial toxicity and lactic acidosis,
kidney and liver damage, Fanconi
syndrome, exacerbation of hepatitis, decrease in bone density, elevated
blood sugar, fast or irregular heartbeat, and allergic reactions. Kidney toxicity can occur within the
first few months of taking Tenofovir, so kidney function must be
monitored. Dehydration contributes
to kidney toxicity and can be minimized by drinking more water.
Integrase
Inhibitors
Raltegravir (brand name Isentress): FDA-Approval in 2007, it’s the first and only approved
integrase inhibitor, though others are in the pipeline. Integrase inhibitors block a later
phase of retroviral integration than NtRTIs or NRTIs do. Raltegravir prevents the enzyme called integrase
from inserting double-stranded viral DNA into the host cells’
DNA.
Common side effects of
raltegravir include: rash, headache,
nausea, asthenia (weakness) and fatigue.
Less common side effects: gastritis, abdominal pain, insomnia,
dizziness, fever, anemia, diarrhea, insomnia, rash, kidney damage, kidney
failure, high blood sugar, depression, and allergic reactions.
With HIV patients, one drug is
started and a second drug in added one to two weeks later, and a third drug is
added one to two weeks after that.
Dr. Ila Singh discussing XMRV and the HIV drugs being tested in animals inoculated with XMRV:
This post should not be
construed as medical advice. Nor
is this post an endorsement of the use of antiretrovirals for ME/CFS patients
and an XMRV diagnosis. I am a
science writer, not a physician or a researcher. Consult your health-care professional before beginning any
treatment plan.
Coming up: Drugs that may help clear XMRV reservoirs. Plus an interview with the CDC's Dr. Steve Monroe, director of the CDC’s division of High Consequence Pathogens and Pathology.
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