Sage Therapeutics' brexanolone hits main goal of two late-stage studies in postpartum depression

Sage Therapeutics announced Thursday that two Phase III studies of its intravenous formulation of brexanolone in patients with moderate or severe postpartum depression met their main goals. The company indicated that it plans to seek FDA approval of the drug, formerly known as SAGE-547, in the first half of next year. Shares in the drugmaker jumped as much as nearly 55 percent on the news.

According to Sage, in both Study 202B, which included patients with severe postpartum depression, and Study 202C, which enrolled patients with moderate postpartum depression, brexanolone achieved a significant mean reduction from baseline in the Hamilton Rating Scale for Depression (HAM-D) total score compared to placebo at 60 hours. Additionally, the change in the Clinical Global Impression – Improvement scale at 60 hours was consistent with the primary endpoint in both trials.

In Study 202B, 122 patients with severe postpartum depression were assigned to treatment with brexanolone, at a dose of 60 mcg/kg/hour or 90 mcg/kg/hour, or placebo. For both doses, a significant change in the HAM-D score was observed at 48 hours, and the effect at 60 hours was maintained through 30 days of follow-up. Specifically, those on the lower dose of brexanolone saw their HAM-D scores fall an average of 19.9 points 60 hours after treatment, compared to a 17.7-point reduction for those on the higher dose and a 14 point change for placebo.

Meanwhile, Study 202C consisted of 104 patients with moderate postpartum depression who were randomised to treatment with 90 mcg/kg/hour brexanolone or placebo. The HAM-D score was significantly improved at 48 hours in the active treatment group, and this effect persisted through day seven but not day 30. Specifically, patients taking brexanolone saw their HAM-D scores fall 14.2 points, compared to a 12-point decline for those on placebo. In addition, the effect recorded at 60 hours persisted through day 30 of follow-up.

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Study leader Samantha Meltzer-Brody said "brexanolone provided a profound and durable effect over the study period that could be an important step in potentially changing the way health care providers think about treating this disorder." Sage indicated that detailed study results will be submitted for presentation at a future research meeting and for publication.

Commenting on the news, Leerink Partners analyst Paul Matteis noted that while the late-stage results don't match the "too good to be true" results of a Phase II study in which HAM-D scores for brexanolone were close to 12 points better than placebo, the findings represent "a technology validating event" that should likely result in FDA approval. Meanwhile, Edward Nash of SunTrust Robinson Humphrey estimated that the intravenous version of brexanolone could amass peak sales of $400 million in 2026, while the oral formulation, which is currently under development, could add an additional $668 million in revenue.

In September, Sage reported that a Phase III study of brexanolone for the treatment super-refractory status epilepticus failed to meet its primary endpoint. For related analysis, read ViewPoints: Sage keeping the focus on depression after late-stage miss in epilepsy.

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