Sage Therapeutics Announces First Quarter 2017 Financial Results and Provides Pipeline Update Phase 3 STATUS Trial of brexanolone in SRSE nearing completion of enrollment expects top-line results in Q3 2017 Advancing SAG

Sage Therapeutics Announces First Quarter 2017 Financial Results and Provides Pipeline Update

Phase 3 STATUS Trial of brexanolone in SRSE nearing completion of enrollment expects top-line results in Q3 2017

Advancing SAGE-217 into Part B open-label Phase 2 trial in Parkinson s disease based on initial activity signal

First patient dosed in placebo-controlled Phase 2 clinical trial of SAGE-217 in major depressive disorder

Conference call today at 4:30 PM ET

CAMBRIDGE, Mass., May 9, 2017 Sage Therapeutics, Inc. (NASDAQ: SAGE), a clinical-stage biopharmaceutical company developing novel

medicines to treat life-altering central nervous system (CNS) disorders, today reported business highlights and financial results for the first quarter ended March 31, 2017.

We continue to make good progress in building Sage into a leading CNS company with the potential to deliver differentiated medicines for a variety of

central nervous system disorders. We are focused on closing the innovation gap in areas of brain disorders where more breakthroughs for patients are needed, said Jeff Jonas, M.D., Chief Executive Officer of Sage. We are now nearing

completion of enrollment in our lead Phase 3 program in super-refractory status epilepticus (SRSE), and remain focused on completing Phase 3 clinical development of brexanolone in both SRSE and postpartum depression (PPD) in 2017. Further, we

continue to advance our growing pipeline of novel product candidates, including our lead oral compound, SAGE-217, in four clinical programs in both mood and movement disorders.

Brexanolone in SRSE Phase 3 STATUS Trial Update

Sage is nearing completion of enrollment in the Phase 3 STATUS Trial, the first ever global, randomized, double-blind, placebo-controlled trial in SRSE. The

Company expects to report top-line results from the STATUS Trial in the third quarter of 2017 after enrollment of an anticipated 126 evaluable patients and completion of all study follow-up periods and data analysis. Sage expects top-line results to

include the primary endpoint, safety and tolerability, and select secondary endpoints, including open-label retreatment arm response and the Clinical Global Impression scale.

Top-Line Results from Part A of SAGE-217 Phase 2 in Parkinson s Disease

Sage today announced top-line results from the Part A open-label portion of a Phase 2 clinical trial of SAGE-217 in Parkinson s disease:

Sage is advancing a portfolio of

novel central nervous system (CNS) product candidates targeting the GABA and NMDA receptor systems. Dysfunction in these systems is known to be at the core of numerous psychiatric and neurological disorders. Sage is pursuing a data-driven approach

to CNS drug development by employing efficient human proof-of-concept studies both to uncover activity signals and to help understand future trial methodology, before investing in larger clinical programs.

Expected Near-Term Clinical Milestones

Financial Results for the First Quarter of 2017

Conference Call Information

Sage will host a conference call and webcast today at 4:30 PM ET to discuss its first quarter financial results and recent corporate updates. The

live webcast can be accessed on the investor page of Sage s website at investor.sagerx.com. The conference call can be accessed by dialing 1-866-450-8683 (toll-free domestic) or 1-281-542-4847 (international) and using the conference ID

12287678. A replay of the webcast will be available on Sage s website approximately two hours after the completion of the event and will be archived for up to 30 days.

About Sage Therapeutics

Sage Therapeutics is a

clinical-stage biopharmaceutical company committed to developing novel medicines to transform the lives of patients with life-altering central nervous system (CNS) disorders. Sage has a portfolio of novel product candidates targeting critical CNS

receptor systems, GABA and NMDA. Sage s lead program, brexanolone (SAGE-547), is in Phase 3 clinical development for super-refractory status epilepticus, a rare and severe seizure disorder,

and for postpartum depression. Sage is developing its next generation modulators, including SAGE-217 and SAGE-718, in various CNS disorders. For more information, please visit

Forward-Looking Statements

Various statements in this release concern Sage s future expectations, plans and prospects, including without limitation: our expectations regarding

development of our product candidates and their potential in the treatment of various CNS disorders; the expected timing of initiation and completion of clinical trials; the anticipated availability and announcement of data and results from clinical

trials of our product candidates; our plans for evaluation of new indications and new compounds; our expectations regarding the regulatory pathway for brexanolone (SAGE-547) in the treatment of SRSE in the EU, and our belief that the results of the

current development program for brexanolone in SRSE, if successful, will be sufficient for an MAA filing in the EU; our expectations regarding a potential future new drug application and MAA filing and commercial launch of brexanolone, if

successfully developed and approved; and our expectations with respect to future cash use and cash needs. These forward-looking statements are neither promises nor guarantees of future performance, and are subject to a variety of risks and

uncertainties, many of which are beyond our control, which could cause actual results to differ materially from those contemplated in these forward-looking statements, including the risks that: we may continue to experience slower than expected

enrollment and randomization of evaluable patients in the STATUS trial or slower than expected clinical site initiation and enrollment in our other clinical trials, or the potential need for additional analysis or data or the need to enroll

additional patients, leading to possible delays in completion of trials or in the availability of data; we may not be able to generate supportive non-clinical data or to successfully demonstrate the efficacy and safety of our product candidates at

each stage of clinical development; success in our non-clinical studies or in earlier stage clinical trials may not be repeated or observed in ongoing or future studies involving the same compound or other product candidates, and ongoing and

future pre-clinical and clinical results may not support further development of product candidates or be sufficient to gain regulatory approval to launch and commercialize any product; decisions or actions of regulatory agencies may affect the

initiation, timing, progress and cost of clinical trials, and our ability to proceed with further clinical studies of a product candidate or to obtain marketing approval or may result in restrictions in an approved indication or the need for

additional clinical trials, including the risk that the EMA may, despite scientific advice, decide that the data from our Phase 3 trial in SRSE are not sufficient to support approval; the internal and external costs required for our activities, and

to build our organization in connection with such activities, and the resulting use of cash, may be higher than expected, or we may conduct additional clinical trials or pre-clinical studies, or engage in new activities, requiring additional

expenditures and using cash more quickly than anticipated; and we may encounter technical and other unexpected hurdles in the development and manufacture of our products which may delay our timing or increase our expenses and use of cash, as

well as those risks more fully discussed in the section entitled Risk Factors in our most recent Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in our subsequent filings

with the Securities and Exchange Commission. In addition, any forward-looking statements represent our views only as of today, and should not be relied upon as representing our views as of any subsequent date. We explicitly disclaim any

obligation to update any forward-looking statements.

Paul Cox, Sage Therapeutics

Maureen L. Suda, Suda Communications LLC

Sage Therapeutics, Inc. and Subsidiaries

Condensed Consolidated Balance Sheets

Sage Therapeutics, Inc. and Subsidiaries

Condensed Consolidated Statements of Operations

(in thousands, except share and per share data)