In the treatment of pain due to endometriosis, use of elagolix 150-mg tablets demonstrates comparable efficacy to dienogest 2-mg tablets, as assessed via numeric rating scale (NRS) score from baseline to day 85 and 169, according to a study presented at RCOG 2024. Additionally, both drugs are well tolerated.

"Hence, elagolix can be considered as a valuable treatment option in the management of pain associated with endometriosis,” said lead author Dr Neena Gupta from GVSM Medical College in Kanpur, India.

Gupta and her team conducted this phase III, randomized, multicentric, double-blind trial to assess the efficacy and safety of elagolix relative to dienogest in easing endometriosis-related pain. They identified 340 premenopausal women with documented endometriosis who had their pain assessed via NRS ≥4, dysmenorrhoea scale (DYS) ≥2, and nonmenstrual pelvic pain (NMPP) ≥2.

Of the screened patients, 230 were randomly allocated 1:1 to receive either elagolix 150 mg (test; n=115) or dienogest 2 mg (comparator; n=115) and matching placebos for 24 weeks.

To test the efficacy of these agents, Gupta and colleagues evaluated the NRS, DYS, NMPP, proportion of patients requiring rescue medication, and proportion of overall responders on Patient Global Impression of Change (PGI-C). They also examined the treatment-emergent adverse events (TEAEs) for safety.

Both treatment arms had similar baseline demographic characteristics. The reductions in NRS score from baseline to day 85 (the primary outcome) did not significantly differ between the test and comparator arms (elagolix vs dienogest: ?2.43 vs ?2.47; treatment difference, 0.04, 95 percent confidence interval [CI], ?0.3 to 0.37), establishing the noninferiority of elagolix. [RCOG 2024, abstract OP-01]

Moreover, the decreases in NRS score from baseline to day 169 were comparable between the test and comparator arms (?4.33 vs ?4.37; treatment difference, 0.04, 95 percent CI, ?0.32 to 0.4). Likewise, the reductions of DYS and NMPP scores from baseline to day 85 and day 169 were similar between elagolix and dienogest.

Rescue medication

The proportion of patients requiring rescue medication at day 169 was 17.7 percent in the test arm, and this percentage is similar to that of the comparator arm at 17.0 percent (p>0.9999). In addition, the proportion of overall responders in PGI-C scale at day 169 did not significantly differ between the two treatment groups (92.9 percent vs 94.6 percent; p=0.5928).

In terms of safety, the incidence of TEAEs were comparable between elagolix and dienogest, with no occurrence of serious adverse events recorded.

In subgroup analysis (S1: test [n=43] and comparator [n=42]; S2: test [n=72] and comparator [n=73]), the decrease in NRS score from baseline to day 85 in the test arm was noninferior to that in the comparator arm for both subgroups (S1: ?2.17 vs ?2.33; treatment difference, 0.15, 95 percent CI, ?0.48 to 0.79; S2: ?2.58 vs ?2.55; treatment difference, ?0.03, 95 percent CI, ?0.42 to 0.35). [RCOG 2024, abstract eP-075]

The same trend persisted until day 169. For DYS and NMPP scores, the reductions from baseline to days 85 and 169 were also similar between elagolix and dienogest for both subgroups.

“This study demonstrated that elagolix 150 mg was effective and well tolerated compared to dienogest 2 mg in treating moderate to severe pain associated with endometriosis as assessed via NRS score from baseline to day 85 and day 169, irrespective of duration of disease,” Gupta said.