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Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

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Results of Operations and Financial Condition

Financial Statements and Exhibits.

Exhibit

No.

Description

Anne Marie Cook

Senior Vice President, General Counsel

The FDA has conditionally accepted the proprietary name ZULRESSO for Sage’s intravenous (IV) formulation of brexanolone;

Sage’s New Drug Application for ZULRESSO for the treatment of PPD was accepted for Priority Review by the FDA. The FDA has assigned a Prescription Drug User Fee Act (PDUFA) target date of December 19, 2018, and is planning to hold an Advisory Committee meeting to discuss the ZULRESSO application on November 2, 2018, consistent with FDA’s policy to seek advice on new medicines with a new mechanism of action for a new indication;

Sage continues with preparations for a potential 1H 2019 commercial launch of ZULRESSO for the treatment of PPD, if the NDA is approved, including:

Advancing development of a family-centric site of care strategy for PPD patients with potential options ranging from the in-patient hospital setting, supervised home care, and alternate sites of care, subject to FDA approval of each option and agreement on the final ZULRESSO label;

Partnering with Lash Group, a part of AmerisourceBergen, to establish a robust patient support model leveraging innovative technologies coupled with Sage-led case management support for PPD patients, and completing preparations for the opening of Sage’s National Patient Support Center in Raleigh, North Carolina this fall;

Continuing expansion of the commercial organization, including considerable progress in the build of the field team;

Engaging in permitted discussions with payers to raise awareness of PPD and on the value proposition of the ZULRESSO product profile, conducting over 100 customer meetings and having met with all National Payer Accounts.

Sage presented a systematic literature review on the humanistic burden of PPD at the 23^rd Annual International Society for Pharmacoeconomics and Outcomes Research (ISPOR) Meeting. The review concluded that there is a considerable body of literature suggesting that PPD has a substantial humanistic burden on affected mothers as well as their children and families, including impaired mother-infant bonding, lower rates of breastfeeding, and the potential for significant long-term impact on the physical and mental development of children. To further understand real-world burdens of PPD, Sage has partnered with the PatientsLikeMe patient network;

Sage is also working with top U.S. health economists on the value assessment of ZULRESSO as part of broader health economics and outcomes research initiatives.

SAGE-217 in Major Depressive Disorder (MDD) and PPD:

In June, Sage received support from the FDA on an expedited pivotal development plan evaluating the novel concept of episodic dosing using a short course treatment of SAGE-217 in both MDD and PPD.

Sage plans to initiate a Phase 3 placebo-controlled trial of SAGE-217 in MDD in 4Q 2018. The trial will evaluate two weeks of 20mg or 30mg SAGE-217 treatment compared to placebo in 450 patients with MDD, with four weeks of additional follow-up.

Sage is also evaluating SAGE-217 in a Phase 3 placebo-controlled trial in 140 patients with PPD, and plans to announce top-line results in 4Q 2018.

Additional data regarding patient safety and potential treatment of recurrent or new major depressive episodes will be acquired through a long-term open-label study program in which approximately 300 patients will be followed for six months and 100 patients will be followed for a year after initial SAGE-217 treatment and episodic retreatment as needed.

In June, Sage entered into a strategic collaboration with Shionogi & Co., Ltd. for the clinical development and commercialization of SAGE-217 for the treatment of MDD and other indications in Japan, Taiwan and South Korea.

SAGE-217 in Other Psychiatric Indications:

Bipolar depression: Sage plans to initiate a two-part Phase 2 trial initially evaluating four weeks of open-label SAGE-217 treatment in up to 30 patients with bipolar I/II disorder with a current major depressive episode. If warranted, the study will progress to a randomized, placebo-controlled study. The trial is intended to evaluate the safety and tolerability of SAGE-217 (primary endpoint) and secondary endpoints, including efficacy in improving depressive symptoms and sleep. Sage plans to initiate this study in 4Q 2018.

Sleep disorders: Sage recently announced additional data on key secondary endpoints from a placebo-controlled trial in a model of insomnia demonstrating an encouraging impact of SAGE-217 on sleep architecture and that treatment did not impact next-day cognitive performance. These data are being planned for presentation at an upcoming medical meeting. Sage plans to initiate a Phase 3 placebo-controlled polysomnography trial in MDD patients with co-morbid insomnia in 4Q 2018, and also plans to seek feedback later this year from the FDA on potential development plans for SAGE-217 for the treatment of sleep disorders.

SAGE-324 in Neurological Indications:

Sage recently received IND clearance to initiate a Phase 1 single-ascending dose trial of SAGE-324 in healthy volunteers. Based on its pre-clinical pharmacokinetic/pharmacodynamic profile, SAGE-324 may be suitable for chronic oral dosing, and is being developed as a potential treatment for patients impacted by neurological conditions, such as epileptiform disorders, essential tremor, and Parkinson’s disease. Sage plans to release top-line results from the study, which is intended to evaluate the safety, tolerability, pharmacokinetic and pharmacodynamic profile of SAGE-324, in 4Q 2018.

GABA Discovery Programs:

Sage continues to evaluate additional novel GABA_A receptor modulators that are currently in pre-clinical development, including SAGE-689, SAGE-105 and others.

NMDA Programs:

SAGE-718: Sage recently initiated a Phase 1 multiple ascending dose trial of SAGE-718 in healthy volunteers. Sage plans to release top-line results from the study, which is intended to further evaluate the safety, tolerability, pharmacokinetic and pharmacodynamic profile of SAGE-718, in 4Q 2018. If the Phase 1 program is successful, Sage expects to advance SAGE-718 into clinical trials of certain CNS disorders characterized by NMDA receptor hypofunction.

SAGE-904: Sage’s second NMDA positive allosteric modulator candidate, SAGE-904, is in IND-enabling studies.

Sage is continuing to advance multiple PPD disease awareness and screening efforts, through initiatives led by Sage’s Medical Affairs organization. Sage is seeing tangible signs of progress on these efforts to improve the urgency to manage PPD, including the American Congress of Obstetricians and Gynecologists’ (ACOG) Committee Opinion on Redefining the Postpartum Visit and recommendation on comprehensive maternal mental care support by Obstetricians/Gynecologists throughout the fourth trimester of pregnancy. The following initiatives were led by the Sage Medical Affairs team in the second quarter:

Launched broad digital disease awareness campaign and knowppd.com website for healthcare providers to improve screening and care for PPD patients.

Conducted live PPD educational symposia at ACOG, American Psychiatric Association (APA), and Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN) Annual Meetings to increase physician and nurse understanding of PPD.

Supported development and launch of independent digital medical education programs on screening and current management of PPD via Medscape and WebMD.

Continued collaboration with national and local patient advocacy groups during maternal mental health month to help reduce stigma of PPD and help patients and families navigate to care.

Ongoing, permitted engagement with a broad number of maternal and psychiatric health centers across the U.S. to develop in-depth profiles on their respective PPD healthcare providers, unique management pathways, and unmet needs.

Medical Meeting Presentations:

24^th Congress of the European Sleep Research Society (ESRS), September 25 – September 28, 2018 in Basel, Switzerland

International Marce Society for Perinatal Health Biennial Scientific Meeting 2018, September 26 – September 28, 2018 in Bangalore, India

31^st European College of Neuropsychopharmacology Congress (ECNP), October 6 – October 9, 2018 in Barcelona, Spain

48^th Annual Meeting of the Society for Neuroscience (SfN), November 3 – November 7, 2018 in San Diego, CA

Trial Initiations:

SAGE-217 Phase 3 placebo-controlled trial in MDD (4Q 2018)

SAGE-217 Phase 3 placebo-controlled polysomnography trial in MDD patients with co-morbid insomnia (4Q 2018)

SAGE-217 Phase 2 trial in bipolar depression (4Q 2018)

Data Readouts:

SAGE-217 Phase 3 placebo-controlled trial in PPD (4Q 2018)

SAGE-718 Phase 1 multiple ascending dose trial (4Q 2018)

SAGE-324 Phase 1 single ascending dose trial (4Q 2018)

Regulatory and Commercial:

EMA Scientific Advice for brexanolone in PPD (4Q 2018)

FDA planned Advisory Committee Meeting for ZULRESSO in PPD (November 2, 2018)

ZULRESSO in PPD PDUFA target date (December 19, 2018)

ZULRESSO in PPD commercial launch, if approved (1H 2019)

Revenues: Collaboration revenues were $90.0 million in the second quarter of 2018, compared with no revenues for the same period of 2017. All revenues for the second quarter of 2018 are attributable to an upfront payment from Sage’s strategic collaboration with Shionogi & Co., Ltd.

R&D Expenses: Research and development expenses were $69.0 million, including $12.1 million of non-cash stock-based compensation expense, in the second quarter of 2018, compared to $55.9 million, including $5.2 million of non-cash stock-based compensation expense, for the same period of 2017. The increase in R&D expenses year-over-year was primarily due to increases in ongoing R&D programs and discovery efforts focused on identifying new clinical

candidates and additional indications of interest and investments in R&D headcount to support the growth in Sage’s pipeline and operations, offset by decreases in expenses due to the completion of Phase 3 clinical development of ZULRESSO.

G&A Expenses: General and administrative expenses were $43.2 million, including $16.9 million of non-cash stock-based compensation expense, in the second quarter of 2018, compared to $15.0 million, including $4.1 million of non-cash stock-based compensation expense, for the same period of 2017. The increase in G&A expenses was primarily due to the increase in personnel-related expenses, professional fees to support expanding operations, costs related to continued preparations for a potential commercial launch, and facilities-related costs to support expanding operations.

Net Loss: Net loss was $17.0 million for the second quarter of 2018 compared to a net loss of $70.2 million for the comparable period of 2017.

Cash Position: Cash, cash equivalents, and marketable securities as of June 30, 2018 were $1.1 billion, compared with $518.8 million at December 31, 2017. The increase was primarily due to net proceeds of $631.2 million from Sage’s follow-on public offering completed in February 2018.

Based on its current operating plan, Sage anticipates that its existing cash, cash equivalents and marketable securities will enable Sage to fund its operating expenses and capital expenditure requirements into 2020.

Sage expects that its operating expenses will increase year-over-year in 2018 to support continued pipeline advancement, including ongoing Phase 3 development of SAGE-217, and preparations for potential commercialization of ZULRESSO in PPD, if approved.

Investor Contact:

Paul Cox, 617-299-8377

paul.cox@sagerx.com

Media Contact:

Maureen L. Suda, 585-355-1134

maureen.suda@sagerx.com

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