Extension to Study on Efficacy and Safety of Linzagolix for the Treatment of Endometriosis-associated Pain

This is a prospective, randomized, double-blind study. Subjects who have completed the 6-month Treatment Period in 18-OBE2109-002 - Edelweiss 2 study (herein referred to as main study) will be invited to enter the present extension study. Month 6 visit of the main study is a decision point for Subjects to either end treatment and enter a post-treatment follow up (part of the main study), or to opt for a 6-month treatment extension. All subjects will receive once daily either linzagolix 75 mg alone (with ABT placebo) or 200 mg combined with ABT for 6 months. Subjects who received placebo during the main study will be randomized to either linzagolix 75 mg alone (with ABT placebo) or linzagolix 200 mg with ABT. Subjects who received active treatment during the main study will continue with the same treatment. Double-dummy design will be used in order to maintain the blinding of the study. After end of treatment in the extension study (6-month treatment period: from Month 6 to Month 12), subjects will enter a post-treatment Follow-Up Period of 6 months with no investigational medicinal product (IMP) or - for subjects willing to continue treatment - a second extension study will be proposed.