In 2017, Reinecke et al. (26) used population PK-PD modeling to guide the development of an intravaginal ring (IVR), delivering the aromatase inhibitor anastrozole (ATZ) and the progestin levonorgestrel (LNG) for long-term, localized treatment of endometriosis and associated pain (26). The gene discussed is CYP19A1; the disease is endometriosis.