Examination of Antiretrovirals Abacavir, Didanosine’s Potential Link to Increased Risk of Heart Attack ContinuesGlaxoSmithKline's antiretroviral drug abacavir could nearly double the risk of heart attack, according to a study released at a meeting in February and published on Tuesday in the online version of the Lancet, the San Francisco Chronicle reports (Russell, San Francisco Chronicle, 4/2).The study also found that Bristol-Myers Squibb's antiretroviral didanosine might be associated with a 50% increased risk of heart attack, the AP/International Herald Tribune reports (AP/International Herald Tribune, 4/2). According to the researchers, the increased risk of heart attack could be the result of a cardiovascular inflammatory response to the drugs, but they added that more research is needed. GSK in a letter published alongside the study said its own analysis of 54 pooled studies did not suggest an increased risk of heart attack associated with abacavir (Berton, Dow Jones/CNNMoney.com, 4/1).
For the study, Jens Lundgren of the University of Copenhagen and colleagues examined more than 33,000 HIV-positive people who had been followed from 1999 to 2005 at clinics in Australia, Europe and North America. The researchers looked for heart issues that occurred until February 2007 (AP/International Herald Tribune, 4/2). The researchers analyzed the risk of heart attack among those who had used or were using abacavir, didanosine and lamivudine. The researchers found that an increased risk of heart attack was only found in participants currently receiving abacavir and didanosine. Abacavir was associated with a 90% increased risk of heart attack, and didanosine use was associated with a 49% increased risk, the study found. An increased risk was not found among past users of the drugs. According to the study authors, the findings suggest that the risk of heart attack associated with the two drugs is reversible if use is stopped (Kaiser Daily HIV/AIDS Report, 2/6). The study found that the people most likely to experience heart problems with abacavir were those with underlying medical conditions, such as high blood pressure and diabetes, that also place them at an increased risk of heart attack (San Francisco Chronicle, 4/2). The company said that an analysis of its database of about 14,600 HIV-positive people did not support the conclusions of the Lancet study.
"We were unable to show any increased risk in heart attacks," Gwenan White, a GSK spokesperson, said, adding that the Lancet study results are "inconclusive" (AP/International Herald Tribune, 4/2). In a linked comment to both the study and GSK's response, James Stein of the University of Wisconsin School of Medicine and Public Health and Judith Currier of the University of California-Los Angeles David Geffen School of Medicine disagreed with GSK's analysis. They wrote that although findings from observational studies should not lead to changes in clinical practices, the increased risk of heart attack cannot be ignored. "Alternatives to abacavir and didanosine in high-risk patients should be considered," they said (Dow Jones/CNNMoney.com, 4/1).
Steven Deeks, a professor at the University of California-San Francisco, said the study was thorough and large-scale but not definitive. He added that although the study shows an increased risk of heart attack, it does not show why. "The concerns it raises are legitimate," he said, adding that until a plausible biological explanation can be ascertained and the findings are confirmed, he would be reluctant to recommend that patients switch to another antiretroviral. John Pottage, vice president for GSK, said the company is taking the results seriously. He added that although the risk of heart attack appears to double with abacavir, such risk is relatively low to begin with. "Obviously, the study is provocative, and people are trying to dig into it and understand it," Pottage said (San Francisco Chronicle, 4/2).
According to the AP/Herald Tribune, the study's findings could affect how people living with HIV/AIDS are treated worldwide. Charlie Gilks, director of AIDS treatment and prevention at the World Health Organization, said, "These antiretrovirals are wonderful and lifesaving, but they do have toxicity problems." He added, "It may be that we can continue to use them, but we need to be aware of their long-term problems." According to Gilks, physicians in wealthy nations have "24 different antiretrovirals to choose from if one isn't appropriate. But if that happens in resource-poor countries, it's not so simple." He added that WHO will "have to review what the likely implications of using these drugs is on a large scale and if we should consider alternatives." Lundgren said, "No drug is risk-free." He added, "For all patients, it's a matter of finding the right balance" (AP/International Herald Tribune, 4/2).
The European Medicines Agency on Wednesday said it is seeking further information about abacavir's safety. The announcement follows a similar one from FDA last week. "At present, no changes to the prescribing information for abacavir-containing medicines are required, but further information is needed to determine the risk of" heart attack with the drugs, the agency said (Reuters, 4/2).
The study is available online.