This randomized, double-blind, parallel-group, Phase 2b trial determined the efficacy and safety of different dose combinations of an aromatase inhibitor (Anastrozole) and progestin (Levonorgestrel) in an intravaginal ring versus placebo and Leuprorelin/Leuprolide acetate as a new treatment option for patients with endometriosis-associated pelvic pain. This evidence concerns the gene CYP19A1 and endometriosis.