The fight against HIV has some new ammunition, thanks to the results of a recent study led by associate professor of medicine Sharon Walmsley, and published in the New England Journal of Medicine. In a head-to-head trial between two drugs, Walmsley and her co-researchers found that a combination of anti-retroviral agents that included lopinavir and ritonavir proved more effective than a combination with nelfinavir, the treatment most commonly used in Canada. Nelfinavir and lopinavir-ritonavir belong to a class of drugs known as protease inhibitors, which help prevent the HIV virus from maturing and replicating. “This is the first time one protease inhibitor has been found to work better than another in patients who haven’t received treatment before,” says Walmsley, a senior scientist at Toronto General Hospital. In the new drug, a small dose of ritonavir is included to inhibit the metabolization of lopinavir in the body, thereby “boosting” the levels of lopinavir in the bloodstream and improving and prolonging its effectiveness. “It’s a whole new concept in HIV therapy,” says Walmsley. Not only was the new drug combination more potent, but it was also easier for patients to take and did not lead to drug resistance. However, Walmsley cautions that patients using lopinavir-ritonavir had more abnormal lipids or fats in the blood – a potential risk factor for heart disease.