Endometriosis is a common condition that leads to pain and infertility, but treatment options are limited. The disease is associated with chronic inflammation, and several inflammatory chemokines have been implicated in its progression. Here, the authors examined the expression of inflammatory genes in endometriotic tissue samples and identified the chemokine CXCL8 (also known as IL-8) and its receptors CXCR1 and CXCR2 as being highly upregulated in women with endometriosis. CXCL8 was also highly expressed in cynomolgus monkeys that spontaneously developed endometriosis, and preliminary experiments suggested that targeting CXCL8 reduced fibrotic disease in these animals. The authors engineered a long-lasting antibody against CXCL8 (AMY109) and showed that therapeutic delivery of this agent reduced disease in a surgically induced model of endometriosis in cynomolgus monkeys. AMY109 seemed to reduce the fibrotic disease associated with endometriosis, at least in part by blocking neutrophil recruitment and activation. The authors report that trials of AMY109 in humans are now underway.