HIV-prevention drug Truvada fails for Toronto man
Truvada is used to block the transmission of the virus, but one man contracted it anyhow.
By:
Michael Robinson
June 12, 2016 - A Toronto man is apparently the first documented person to contract a rare, drug-resistant strain of HIV, despite taking a “miracle” drug every day that is used by tens of thousands of people across North America to prevent the spread of the virus.
Researchers say the 43-year-old contracted the virus after engaging in unprotected anal sex with multiple sexual partners. They claim his case is the first reported failure of Truvada — a medication that blocks the transmission of HIV — where a patient took the antiretroviral drug daily but still became infected.
“Even though the patient was taking the drug every day, the HIV virus overpowered the medication and infected him,” said the man's doctor, Dr. David Knox, an HIV-specialist and primary care physician at Toronto's Maple Leaf Medical Clinic.
Knox reported his finding at the Conference on Retroviruses and Opportunistic Infection in Boston this past February. He explained the case serves as stark reminder for gay or bisexual men to continue wearing condoms instead of relying solely on Truvada.
A spokesperson for the biopharmaceutical company who manufactures the drug said the Toronto case is the first Truvada failure they are aware of. Still, they emphasized that “several large-scale clinical trials” have shown the medication is safe and effective.
“It is important to note, however, that no single intervention is 100 per cent effective in preventing HIV,” wrote Gilead Sciences Inc.'s Ryan McKeel in an emailed statement to the Star. McKeel explained that the individual in this case “contracted the virus after he was exposed to a rare strain of HIV that is resistant to both of the drugs included in Truvada.”
However, little is known about the person who the mutated virus came from.
“It could be someone in Toronto, it could have been someone who was travelling through,” said Knox. “We don't know for sure but yes, this resistant strain could be in Toronto.”
Public Health Ontario's chief of infection prevention and control Dr. Gary Garber said this case is also a reminder that “nothing in this world is 100 per cent” and “taking medication as a preventive measure may not give you the protection that you think.”
Dr. Darrell Tan, a clinical scientist and infectious disease expert at St. Michael's Hospital who co-authored the presentation, said the drug remains a “fantastic new tool” to be used alongside condoms.
“This was a demonstration of what could happen in extremely rare circumstances if we aren't careful so let's continue to be careful,” he said.
A Health Canada spokesperson told the Star health care providers must prescribe the drug as “part of a comprehensive prevention strategy, including safer sex practices, as Truvada is not always effective in preventing the acquisition of HIV-1 infection.”
Truvada — a chemical cocktail containing emtricitabine and tenofovir disoproxil fumarate — was traditionally a first-line treatment option for HIV-positive people before being approved for daily preventive use in the U.S. in 2012. Health Canada gave it the go-ahead for preventive use in late February of this year.
The drug has so far proven itself to be a hot seller in the U.S. Truvada brought Gilead some $2 billion worth of sales south of the border last year.
In Ontario, Truvada is not listed under the province's drug benefit program as a prescription for HIV prevention, only for HIV treatment. (Knox's patient had been taking the drug, acquired via off-label prescrition, for two years when he got infected.) Each tablet costs $28.57.
Similar to birth control, the small, oval-shaped blue pill is most effective when taken consistently, not just before sex. This approach is known as pre-exposure prophylaxis, or PrEP and refers to the use of Truvada by healthy, non-infected people as a pseudo-biochemical condom to prevent contracting HIV.
An ongoing study at the HIV Prevention Clinic at St. Michael's Hospital aims to measure the effect the prevention pill has on safe sex practices. According to the CBC, early results from the study suggest condomless sex between HIV-positive and HIV-negative men on the drug is increasing.
Public health experts have previously warned the medication could provide users with a false sense of security, promote riskier sex and erode condom use. Knox said his patient's case illustrates why physicians “should still be reinforcing condom use,” widely considered to be a cornerstone of HIV prevention strategy.
However, Chris Thomas, a spokesperson for the AIDS Committee of Toronto, stressed that just because the pill didn't do its job in this case does not mean it's not beneficial.
“Yes, this was an unfortunate exemption that occurred in our community,” he said. “But science has also suggested this is a highly effective method of preventing HIV, so it's important to keep that in mind.”
Ongoing HIV transmission remains “an issue of concern” to the Public Health Agency of Canada. Government data suggests there were over 2,500 total new infections in 2014 alone — more than half of which stemmed from male-to-male sexual encounters.
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Source: Toronto Star
"Reproduced with permission - Torstar Syndication Services"
Toronto Star
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