People taking the entry inhibitor Selzentry (maraviroc) were no more likely to develop cancer than people taking either Sustiva (efavirenz) or a placebo, according to a study presented Tuesday, July 20, at the XVIII International AIDS Conference (IAC), taking place July 18 to 23 in Vienna.

Concerns based on both actual and theoretical scenarios have been raised since the development of CCR5-blocking entry inhibitors, such as Selzentry. From a factual standpoint, a small cluster of malignancies was seen in an early trial of a Schering entry inhibitor that never made it to market. From a theoretical perspective, researchers have speculated that drugs such as Selzentry, which block the CCR5 coreceptor on CD4 cells, could change the way a person's immune system seeks out cancerous cells. For this reason, the U.S. Food and Drug Administration (FDA) required Selzentry's maker to conduct long-term surveillance of people on the drug.

To assess the rate of malignancies in people who'd been in Selzentry clinical trials, Sharon Walmsley, MD, from the University of Toronto and her colleagues examined data from four Selzentry studies, MOTIVATE 1 and 2, MERIT and A4001029. The studies included both treatment experienced individuals and those who hadn't used antiretroviral (ARV) drugs in the past (treatment naive). In total, Walmsley and her colleagues analyzed data on 1,499 people who took Selzentry, 361 who used Sustiva and 270 who received a placebo.

Walmsley's team found no evidence that Selzentry increased the risk of developing a malignancy. Numerically, there were no more malignancy cases among those taking Selzentry than those who took either Sustiva or a placebo. In fact, among treatment experienced individuals there were actually fewer malignancies of any type among those who took Selzentry than in those who took a placebo. Similarly, there were fewer cases of non-AIDS-related cancers among treatment naive individuals taking Selzentry than in those taking Sustiva.

“Malignancy rates were generally numerically lower on [Selzentry] than [either Sustiva or placebo],” Walmsley concluded. “This analysis showed no associated increased risk of malignancies with [Selzentry] and, in fact, a decrease in some malignancy types.”