The FDA recently approved Prezista (darunavir), a new drug for adults whose infection with the human immunodeficiency virus (HIV) has not responded to treatment with other antiretroviral drugs. Prezista, a new HIV protease inhibitor, is approved to be co-administered with a low-dose of ritonavir and other active anti-HIV agents. Ritonavir, a protease inhibitor approved in 1996, slows the breakdown of Prezista in the body thereby increasing the concentration of Prezista in the patient’s system.

Infection with HIV causes AIDS, which results in more than 15,000 premature deaths each year in the United States and more than 2.8 million deaths each year worldwide.

“This approval offers new hope to HIV patients who too often urgently need new therapies in order to maintain their health,” said Andrew C. von Eschenbach, MD, Acting Commissioner of Food and Drugs. “This drug is not a cure, but when combined with other standard therapies, it presents one more major step in our effort to help patients combat the effects of the disease.”

The accelerated approval is based on evidence from two randomized, controlled studies comparing the safety and effectiveness of a Prezista-ritonavir combination with other ritonavir-boosted protease inhibitor combinations. Patients in both arms of these trials also used other anti-HIV agents (nucleoside reverse transcriptase inhibitors) with or without enfuvirtide, a fusion inhibitor that inhibits the virus from entering the cell. In these studies, patients on a Prezista-ritonavir combination experienced higher rates of reduction of their HIV viral load than patients on other ritonavir-boosted protease inhibitor combinations. Seventy percent of treatment-experienced patients achieved a virologic response, improving the treatment outcome, with Prezista-ritonavir in combination therapy compared to 21 percent in control group at week 24.

The most common side effects reported by patients on the Prezista-ritonavir regimen included diarrhea, nausea, and headache. About seven percent of patients on this combination therapy experienced skin rashes ranging from mild to serious.

The risks and benefits of Prezista have not been established for adults who have not been previously treated for HIV, or for children.

As a condition of the accelerated approval, the manufacturer is required to conduct post-marketing trials to verify and describe the clinical benefits of Prezista. Other postmarketing studies that the manufacturer has committed to conduct include studies in pediatric populations, studies to better define certain drug-drug interactions, and to evaluate the drug in patients with varying degrees of liver impairment to identify appropriate dosing for this patient population.

Patients are advised to take Prezista and ritonavir with food, and not to use the combination therapy together with St. John’s wort or various other drugs, including certain anticonvulsants, antihistamines, sedatives and a few of the protease inhibitors.