Exhibit (a)(1)(B)​

Letter of Transmittal to Tender Shares of Common Stock
of
SAGE THERAPEUTICS, INC.
at
$8.50 per share, net to the seller in cash, plus one non-transferable and non-tradable contingent value right per share, which represents the right to receive
up to $3.50 per Share, net to the seller in cash, subject to any withholding of taxes and without interest upon the achievement of specified milestones
Pursuant to the Offer to Purchase dated July 2, 2025
by
SAPHIRE, INC.
a wholly owned subsidiary of

SUPERNUS PHARMACEUTICALS, INC.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE FOLLOWING 11:59 P.M., EASTERN TIME, ON JULY 30, 2025, UNLESS THE OFFER IS EXTENDED OR EARLIER TERMINATED

The Depositary for the Offer is:

Equiniti Trust Company, LLC

Method of delivery of the certificate(s) is at the option and risk of the owner thereof. See Instruction 2. Mail or deliver this Letter of Transmittal, together with the certificate(s) representing your shares, to:

If delivering by hand, express mail, courier, or other expedited service:	By mail:
Equiniti Trust Company, LLC 55 Challenger Road, Suite # 200 Ridgefield Park, New Jersey 07660 Attn: Reorganization Department	Equiniti Trust Company, LLC Operations Center Attn: Reorganization Department P.O. Box 525 Ridgefield Park, New Jersey 07660

Pursuant to the offer of Saphire, Inc. to purchase all outstanding Shares of Sage Therapeutics, Inc. (the “Shares”), the undersigned encloses herewith and tenders the following Shares:

DESCRIPTION OF SHARES SURRENDERED
Name(s) and Address(es) of Registered Owner(s) (If blank, please fill in exactly as name(s) appear(s) on share certificate(s))	Shares Surrendered (attached additional list if necessary)
​	Certificated Shares**			​	​
	Certificate Number(s)*	Total Number of Shares Represented by Certificate(s)*	Number of Shares Surrendered**	Book Entry Shares Surrendered	DRIP shares to be tendered
	Total Shares	​	​	​	​
* Need not be completed by book-entry stockholders.
** Unless otherwise indicated, it will be assumed that all shares of common stock represented by certificates described above are being surrendered hereby.

THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH ABOVE FOR THE DEPOSITARY WILL NOT CONSTITUTE VALID DELIVERY. YOU MUST SIGN THIS LETTER OF TRANSMITTAL IN THE APPROPRIATE SPACE PROVIDED BELOW, WITH SIGNATURE GUARANTEE, IF REQUIRED, AND COMPLETE THE IRS FORM W-9 SET FORTH BELOW, IF REQUIRED. PLEASE READ THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL CAREFULLY BEFORE COMPLETING THIS LETTER OF TRANSMITTAL.

ALL QUESTIONS REGARDING THE OFFER SHOULD BE DIRECTED TO THE INFORMATION AGENT, D.F. KING & CO., INC., AT (877) 361-7972 OR THE ADDRESS SET FORTH ON THE BACK PAGE OF THE OFFER TO PURCHASE.

IF YOU WOULD LIKE ADDITIONAL COPIES OF THIS LETTER OF TRANSMITTAL OR ANY OF THE OTHER OFFERING DOCUMENTS, YOU SHOULD CONTACT THE INFORMATION AGENT, D.F. KING & CO., INC., AT (877) 361-7972.

THE OFFER IS BEING MADE TO ALL HOLDERS OF SHARES. WE ARE NOT AWARE OF ANY JURISDICTION IN WHICH THE MAKING OF THE OFFER OR THE ACCEPTANCE THEREOF WOULD BE PROHIBITED BY SECURITIES, “BLUE SKY” OR OTHER LAW OR REGULATION OF SUCH JURISDICTION. IF WE BECOME AWARE OF ANY U.S. STATE IN WHICH THE MAKING OF THE OFFER OR THE ACCEPTANCE OF SHARES PURSUANT THERETO WOULD NOT BE IN COMPLIANCE WITH LAW OR REGULATION, WE WILL MAKE A GOOD FAITH EFFORT TO COMPLY WITH ANY SUCH LAW OR REGULATION. IF, AFTER SUCH GOOD FAITH EFFORT, WE CANNOT COMPLY WITH ANY SUCH LAW OR REGULATION, THE OFFER WILL NOT BE MADE TO (NOR WILL TENDERS BE ACCEPTED FROM OR ON BEHALF OF HOLDERS OF) THE HOLDERS OF SHARES IN SUCH STATE. IN THOSE JURISDICTIONS WHERE APPLICABLE LAWS OR REGULATIONS REQUIRE THE OFFER TO BE MADE BY A LICENSED BROKER OR DEALER, THE OFFER SHALL BE DEEMED TO BE MADE ON BEHALF OF PURCHASER BY ONE OR MORE REGISTERED BROKERS OR DEALERS LICENSED UNDER THE LAWS OF SUCH JURISDICTION TO BE DESIGNATED BY PURCHASER.

This Letter of Transmittal is being delivered to you in connection with the offer by Saphire, Inc., a Delaware corporation (“Purchaser”) and wholly owned subsidiary of Supernus Pharmaceuticals, Inc., a Delaware corporation (“Supernus”), to purchase all of the outstanding shares of common stock, par value $0.0001 per share (the “Shares”), of Sage Therapeutics, Inc., a Delaware corporation (“Sage”), in exchange for (a) $8.50 per Share, net to the seller in cash, subject to any withholding of taxes and without interest (the “Closing Amount”), plus (b) one non-transferable and non-tradable contingent value right per Share (a “CVR”), which represents the right to receive up to $3.50 per Share, net to the seller in cash, subject to any withholding of taxes and without interest, upon the satisfaction of specified milestones (as described in the Offer to Purchase), in accordance with the terms of the Merger Agreement, which amounts will become payable, if at all, if specified milestones are achieved prior to the applicable Milestone Deadline Date (as defined in the Offer to Purchase) (the Closing Amount plus one CVR collectively, the “Offer Price”), upon the terms and subject to the conditions set forth in this Letter of Transmittal (the “Letter of Transmittal”) and the related Offer to Purchase by Purchaser, dated July 2, 2025 (the “Offer to Purchase,”) and the other exhibits to the Tender Offer Statement on Schedule TO dated July 2, 2025 (which, together with this Letter of Transmittal and other related materials, as each may be amended, supplemented or modified from time to time, collectively constitute the “Offer”). The Offer expires on the Expiration Date. “Expiration Date” means one minute following 11:59 p.m., Eastern Time, on July 30, 2025, unless the expiration of the Offer is extended to a subsequent date and time in accordance with the terms of the Agreement and Plan of Merger, dated June 13, 2025, by and among Supernus, Sage and Purchaser (the “Merger Agreement”), in which event the term “Expiration Date” means such subsequent date and time.

You should use this Letter of Transmittal to deliver to Equiniti Trust Company, LLC (the “Depositary”) Shares represented by stock certificates or held in book-entry form on the books of Sage, or its stock transfer agent, for tender. If you are delivering your Shares by book-entry transfer to an account maintained by the

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Depositary at The Depository Trust Company (“DTC”), you must use an Agent’s Message (as defined in Instruction 2 below). In this Letter of Transmittal, stockholders who deliver certificates representing their Shares are referred to as “Certificate Stockholders.” Delivery of documents to DTC will not constitute delivery to the Depositary.

If any certificate representing any Shares you are tendering with this Letter of Transmittal has been lost, stolen, destroyed or mutilated, you should contact Sage’s stock transfer agent, Equiniti Trust Company, LLC (the “Transfer Agent”) by telephone (718) 921-8317, fax (718) 765-8758, or toll-free at (877) 248-6417 (toll free in the United States) regarding the requirements for replacement. You may be required to post a bond to secure against the risk that such certificates may be subsequently recirculated. You are urged to contact the Transfer Agent immediately in order to receive further instructions, for a determination of whether you will need to post a bond and to permit timely processing of this documentation. See Instruction 10.

IF TENDERED SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER TO THE ACCOUNT MAINTAINED BY THE DEPOSITARY WITH DTC, COMPLETE THE FOLLOWING (ONLY FINANCIAL INSTITUTIONS THAT ARE PARTICIPANTS IN DTC MAY DELIVER SHARES BY BOOK- ENTRY TRANSFER):

Name of Tendering Institution:
DTC Participant Number:
Transaction Code Number:

NOTE: SIGNATURES MUST BE PROVIDED BELOW.
PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY.

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Ladies and Gentlemen:

The undersigned hereby tenders to Saphire, Inc., a Delaware corporation (“Purchaser”) and wholly owned subsidiary of Supernus Pharmaceuticals, Inc., a Delaware corporation (“Supernus”), the above-described shares of common stock, par value $0.001 per share (the “Shares”), of Sage Therapeutics, Inc., a Delaware corporation (“Sage”), in exchange for (a) $8.50 per Share, net to the seller in cash, subject to any withholding of taxes and without interest (the “Closing Amount”), plus (b) one non-transferable and non-tradable contingent value right per Share (a “CVR”), which represents the right to receive the Milestone Payments (as defined in the Offer to Purchase), which amounts will become payable, if at all, if specified milestones are achieved prior to the applicable Milestone Deadline Date (as defined in the Offer to Purchase) (the “Offer Price”), upon the terms and subject to the conditions set forth in this Letter of Transmittal and the related Offer to Purchase by Purchaser, dated July 2, 2025 (the “Offer to Purchase,” which, together with this Letter of Transmittal and other related materials, as each may be amended, supplemented or modified from time to time, collectively constitute the “Offer”). The undersigned hereby acknowledges the undersigned has received the Offer to Purchase. The Offer expires on the Expiration Date. “Expiration Date” means one minute following 11:59 p.m., Eastern Time, on July 30, 2025, unless the expiration of the Offer is extended to a subsequent date and time in accordance with the terms of the Agreement and Plan of Merger, dated June 13, 2025, by and among Supernus, Sage and Purchaser (the “Merger Agreement”), in which event the term “Expiration Date” means such subsequent date and time.

Upon the terms and subject to the conditions of the Offer (including, if the Offer is extended or amended, the terms and conditions of such extension or amendment), subject to, and effective upon, acceptance for payment of the Shares validly tendered herewith, and not properly withdrawn, prior to the Expiration Date in accordance with the terms of the Offer, the undersigned hereby sells, assigns and transfers to, or upon the order of, Purchaser, all right, title and interest in and to all of the Shares being tendered hereby and any and all dividends, distributions, rights, other Shares or other securities issued or issuable in respect of such Shares on or after the date hereof (collectively, “Distributions”). In addition, the undersigned hereby irrevocably appoints Equiniti Trust Company, LLC (the “Depositary”) the attorney-in-fact and proxy of the undersigned with respect to such Shares and any and all Distributions with full power of substitution (such proxies and power of attorney being deemed to be an irrevocable power coupled with an interest in the tendered Shares and any Distributions) to the full extent of such stockholder’s rights with respect to such Shares and any Distributions (a) to deliver certificates representing such Shares (the “Share Certificates”) and any and all Distributions, or transfer of ownership of such Shares and any and all Distributions on the account books maintained by The Depository Trust Company (“DTC”), together, in either such case, with all accompanying evidence of transfer and authenticity, to or upon the order of Purchaser, (b) to present such Shares and any and all Distributions for transfer on the books of Sage, and (c) to receive all benefits and otherwise exercise all rights of beneficial ownership of such Shares and any Distributions, all upon the terms and subject to the conditions of the Offer.

Purchaser reserves the right to require that, in order for Shares to be deemed validly tendered, immediately upon Purchaser’s acceptance for payment of such Shares, Purchaser must be able to exercise full voting, consent and other rights, to the extent permitted under applicable law, with respect to such Shares and any and all Distributions, including voting at any meeting of stockholders or executing a written consent concerning any matter.

The undersigned hereby represents and warrants that the undersigned has full power and authority to tender, sell, assign and transfer any and all of the Shares tendered hereby and any and all Distributions and, when the same are accepted for payment by Purchaser, Purchaser will acquire good, marketable and unencumbered title thereto, free and clear of all liens, restrictions, charges and encumbrances, and that the same will not be subject to any adverse claim. The undersigned hereby represents and warrants that the undersigned is the registered owner of the Shares, or the Share Certificate(s) have been endorsed to the undersigned in blank, or the undersigned is a participant in DTC whose name appears on a security position listing as the owner of the Shares. The undersigned will, upon request, execute and deliver any additional documents deemed by the Depositary or Purchaser to be necessary or desirable to complete the sale, assignment and transfer of any and all of the Shares tendered hereby and any and all Distributions. In addition, the undersigned shall promptly remit and transfer to the Depositary for the account of Purchaser any and all Distributions in respect of any and all of the Shares tendered hereby, accompanied by

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appropriate documentation of transfer and, pending such remittance and transfer or appropriate assurance thereof, Purchaser shall be entitled to all rights and privileges as owner of any such Distributions and may withhold the entire Offer Price or deduct from such Offer Price the amount or value thereof, as determined by Purchaser in its sole discretion.

It is understood that the undersigned will not receive payment for the Shares unless and until the Shares are accepted for payment and until the Share Certificate(s) owned by the undersigned are received by the Depositary at the address set forth above, together with such additional documents as the Depositary may require, or, in the case of Shares held in book-entry form, ownership of Shares is validly transferred on the account books maintained by DTC, and until the same are processed for payment by the Depositary.

IT IS UNDERSTOOD THAT THE METHOD OF DELIVERY OF THE SHARES, THE SHARE CERTIFICATE(S) AND ALL OTHER REQUIRED DOCUMENTS (INCLUDING DELIVERY THROUGH DTC) IS AT THE OPTION AND RISK OF THE UNDERSIGNED AND THAT THE RISK OF LOSS OF SUCH SHARES, SHARE CERTIFICATE(S) AND OTHER DOCUMENTS SHALL PASS ONLY AFTER THE DEPOSITARY HAS ACTUALLY RECEIVED THE SHARES OR SHARE CERTIFICATE(S) (INCLUDING, IN THE CASE OF A BOOK-ENTRY TRANSFER, BY BOOK-ENTRY CONFIRMATION (AS DEFINED BELOW)). IF DELIVERY IS BY MAIL, IT IS RECOMMENDED THAT ALL SUCH DOCUMENTS BE SENT BY PROPERLY INSURED REGISTERED MAIL WITH RETURN RECEIPT REQUESTED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

All authority conferred or agreed to be conferred pursuant to this Letter of Transmittal shall not be affected by, and shall survive, the death or incapacity of the undersigned and any obligation of the undersigned hereunder shall be binding upon the heirs, executors, administrators, trustees in bankruptcy, personal representatives, successors and assigns of the undersigned. Except upon the terms and subject to the conditions of the Offer, this tender is irrevocable.

The undersigned understands that the acceptance for payment by Purchaser of Shares tendered pursuant to one of the procedures described in Section 3 of the Offer to Purchase and in the instructions hereto will constitute a binding agreement between the undersigned and Purchaser upon the terms and subject to the conditions of the Offer. The undersigned recognizes that under certain circumstances, upon the terms and subject to the conditions of the Offer, Purchaser may not be required to accept for payment any of the Shares tendered hereby.

The undersigned understands that the CVRs will not be transferable except (i) upon death of a holder by will or intestacy; (ii) pursuant to a court order; (iii) by operation of law (including by consolidation or merger) or without consideration in connection with the dissolution, liquidation or termination of any corporation, limited liability company, partnership or other entity; (iv) in the case of a CVR held in book-entry or other similar nominee form, from a nominee to a beneficial owner and, if applicable, through an intermediary, to the extent allowable by DTC; or (v) a holder’s abandonment of a CVR to Supernus or any of its affiliates. The undersigned further understands that the CVRs will not have any voting or dividend rights or accrue interest and will not represent any equity or ownership interest in Supernus, Purchaser or Sage. The undersigned understands that the CVRs will be registered in the name of the undersigned.

Unless otherwise indicated herein under “Special Payment Instructions,” please issue the check for the Closing Amount in the name(s) of, and/or return any Share Certificates representing Shares not validly tendered or accepted for payment to, the registered owner(s) appearing under “Description of Shares Tendered.” Similarly, unless otherwise indicated under “Special Delivery Instructions,” please mail the check for the Closing Amount and/or return any Share Certificates representing Shares not validly tendered or accepted for payment (and accompanying documents, as appropriate) to the address(es) of the registered owner(s) appearing under “Description of Shares Tendered.” Subject to the terms of the CVR Agreement (as defined in the Offer to Purchase), please make all payments regarding the CVRs as directed herein for payment of the cash consideration and enter in the CVR register to be maintained by the rights agent pursuant to the CVR Agreement the name(s) and address(es) appearing on the cover page of this Letter of Transmittal for each registered holder. The undersigned recognizes that Purchaser has no obligation, pursuant to the Special Payment Instructions, to transfer any Shares from the name(s) of the registered holder(s) thereof if Purchaser does not accept for payment any of the Shares so tendered.

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In the event that both the Special Delivery Instructions and the Special Payment Instructions are completed, please issue the check for the Closing Amount and/or issue any Share Certificates representing Shares not validly tendered or accepted for payment (and any accompanying documents, as appropriate) in the name of, and deliver such check and/or return such Share Certificates (and any accompanying documents, as appropriate) to, the person or persons so indicated. Unless otherwise indicated herein in the box titled “Special Payment Instructions,” please credit any Shares validly tendered hereby or by an Agent’s Message and delivered by book-entry transfer, but which are not purchased, by crediting the account at DTC designated above. The undersigned recognizes that Purchaser has no obligation pursuant to the Special Payment Instructions to transfer any Shares from the name of the registered owner thereof if Purchaser does not accept for payment any of the Shares so validly tendered.

SPECIAL PAYMENT INSTRUCTIONS (See Instructions 1, 4, 5 and 7)
To be completed ONLY if Share Certificates not validly tendered or not accepted for payment and/or the check for the Closing Amount in consideration of Shares validly tendered and accepted for payment are to be issued in the name of someone other than the undersigned:
Issue: ☐ Check and/or ☐ Share Certificates to:
Name:	(Please Print)
Address
(Include Zip Code)
(Tax Identification or Social Security Number)

SPECIAL DELIVERY INSTRUCTIONS (See Instructions 1, 4, 5 and 7)
To be completed ONLY if Share Certificate(s) not validly tendered or not acceptable for payment and/or the check for the Closing Amount of Shares validly tendered and accepted for payment are to be sent to someone other than the undersigned or to the undersigned at an address other than that shown in the box titled “Description of Shares Tendered” above
Issue: ☐ Check and/or ☐ Share Certificates to:
Name:	(Please Print)
Address
(Include Zip Code)

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IMPORTANT — SIGN HERE
(U.S. Holders Please Also Complete the Enclosed IRS Form W-9)
(Non-U.S. Holders Please Obtain and Complete IRS Form W-8BEN or W-8BEN-E or Other Applicable
IRS Form W-8)

(Signature(s) of Stockholder(s))

Dated:           , 20  

(Must be signed by registered owner(s) exactly as name(s) appear(s) on Share Certificate(s) or on a security position listing or by person(s) authorized to become registered owner(s) by certificates and documents transmitted herewith. If signature is by trustees, executors, administrators, guardians, attorneys-in-fact, officers of corporations or others acting in a fiduciary or representative capacity, please set forth full title and see Instruction 5. For information concerning signature guarantees, see Instruction 1.)

Name(s): 

(Please Print)

Capacity (full title): 

Address: 

(Include Zip Code)

Area Code and Telephone Number:  

Tax Identification or Social Security No.:  

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GUARANTEE OF SIGNATURE(S)
(For use by Eligible Institutions only;
see Instructions 1 and 5)

Name of Firm: 

(Include Zip Code)

Authorized Signature: 

(Please Type or Print)

Name: 

Area Code and Telephone Number: 

Dated:           , 20  

Place medallion guarantee in space below:

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INSTRUCTIONS
Forming Part of the Terms and Conditions of the Offer

1.   Guarantee of Signatures for Shares.   No signature guarantee is required on this Letter of Transmittal (a) if this Letter of Transmittal is signed by the registered holder(s) (which term, for purposes of this Section 1, includes any participant in DTC’s systems whose name appears on a security position listing as the owner of the Shares) of the Shares tendered therewith, unless such holder or holders have completed either the box entitled “Special Delivery Instructions” or the box entitled “Special Payment Instructions” on the cover of this Letter of Transmittal or (b) if the Shares are tendered for the account of a financial institution (including most commercial banks, savings and loan associations and brokerage houses) that is a member in good standing of the Security Transfer Agents Medallion Program or any other “eligible guarantor institution,” as such term is defined in Rule 17Ad-15 of the Securities Exchange Act of 1934, as amended (each an “Eligible Institution” and collectively “Eligible Institutions”) (for example, the Security Transfer Agents Medallion Program, the New York Stock Exchange Medallion Signature Program and the Stock Exchanges Medallion Program). In all other cases, all signatures on this Letter of Transmittal must be guaranteed by an Eligible Institution. See Instruction 5.

2.   Delivery of Letter of Transmittal and Certificates or Book-Entry Confirmations.   This Letter of Transmittal is to be completed by stockholders if Share Certificates are to be forwarded herewith. If Shares represented by Share Certificates are being tendered, such Share Certificates, as well as this Letter of Transmittal properly completed and duly executed with any required signature guarantees, and any other documents required by this Letter of Transmittal, must be received by the Depositary at its address set forth herein on or prior to the Expiration Date. If Shares are to be tendered by book-entry transfer, the procedures for tender by book-entry transfer set forth in Section 3 of the Offer to Purchase must be followed, and an Agent’s Message and confirmation of a book-entry transfer into the Depositary’s account at DTC of Shares tendered by book-entry transfer (such a confirmation, a “Book-Entry Confirmation”) must be received by the Depositary on or prior to the Expiration Date.

The term “Agent’s Message” means a message, transmitted through electronic means by DTC in accordance with the normal procedures of DTC to, and received by, the Depositary and forming part of a Book-Entry Confirmation, that states that DTC has received an express acknowledgment from the participant in DTC tendering the Shares that are the subject of such Book-Entry Confirmation that such participant has received and agrees to be bound by the terms of, this Letter of Transmittal, and that Purchaser may enforce such agreement against such participant. The term “Agent’s Message” also includes any hard copy printout evidencing such message generated by a computer terminal maintained at the Depositary’s office.

THE METHOD OF DELIVERY OF THE SHARES (OR SHARE CERTIFICATES), THIS LETTER OF TRANSMITTAL AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH DTC, IS AT THE ELECTION AND RISK OF THE TENDERING STOCKHOLDER. DELIVERY OF THE SHARES (OR SHARE CERTIFICATES), THIS LETTER OF TRANSMITTAL AND ALL OTHER REQUIRED DOCUMENTS WILL BE DEEMED MADE, AND RISK OF LOSS THEREOF SHALL PASS, ONLY WHEN THEY ARE ACTUALLY RECEIVED BY THE DEPOSITARY (INCLUDING, IN THE CASE OF A BOOK-ENTRY TRANSFER OF SHARES, BY BOOK-ENTRY CONFIRMATION WITH RESPECT TO SUCH SHARES). IF SUCH DELIVERY IS BY MAIL, IT IS RECOMMENDED THAT THE SHARES (OR SHARE CERTIFICATES), THIS LETTER OF TRANSMITTAL AND ALL OTHER REQUIRED DOCUMENTS BE SENT BY PROPERLY INSURED REGISTERED MAIL WITH RETURN RECEIPT REQUESTED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

No alternative, conditional or contingent tenders will be accepted and no fractional Shares will be purchased. All tendering stockholders, by execution of this Letter of Transmittal, waive any right to receive any notice of the acceptance of their Shares for payment.

All questions as to validity, form, eligibility (including time of receipt) and acceptance for payment of any tender of Shares, will be determined by Purchaser in its sole discretion, which determination shall be final and binding on all parties, subject to the rights of holders of Shares to challenge such determination with respect to their Shares in a court of competent jurisdiction and any subsequent judgment of any such court. Purchaser reserves the absolute right to reject any and all tenders determined by it not to be in proper

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form or the acceptance for payment of which may, in our opinion, be unlawful. Purchaser also reserves the absolute right to waive any defect or irregularity in the tender of any Shares of any particular stockholder whether or not similar defects or irregularities are waived in the case of other stockholders. No tender of shares will be deemed to have been validly made until all defects and irregularities have been cured or waived to Purchaser’s satisfaction.

3.   Inadequate Space.   If the space provided on the cover page to this Letter of Transmittal is inadequate, the certificate numbers and/or the number of Shares should be listed on a separate schedule attached hereto and separately signed on each page thereof in the same manner as this Letter of Transmittal is signed.

4.   Partial Tenders   (Applicable to Certificate Stockholders Only). If fewer than all the Shares evidenced by any Share Certificate delivered to the Depositary are to be tendered, stockholders should contact Sage’s stock transfer agent, Equiniti Trust Company, LLC (the “Transfer Agent”) by telephone (718) 921-8317, fax (718) 765-8758, or toll-free at (877) 248-6417 (toll free in the United States) to arrange to have such Share Certificate divided into separate Share Certificates representing the number of shares to be tendered and the number of shares to not be tendered. The stockholder should then tender the Share Certificate representing the number of Shares to be tendered as set forth in this Letter of Transmittal. All Shares represented by Share Certificates delivered to the Depositary will be deemed to have been tendered.

5.   Signatures on Letter of Transmittal; Stock Powers and Endorsements.   If this Letter of Transmittal is signed by the registered owner(s) of the Shares tendered hereby, the signature(s) must correspond with the name(s) as written on the face of the Share Certificate(s) without alteration or any other change whatsoever.

If any Shares tendered hereby are owned of record by two or more joint owners, all such owners must sign this Letter of Transmittal.

If any tendered Shares are registered in the names of different holder(s), it will be necessary to complete, sign and submit as many separate Letters of Transmittal as there are different registrations of such Shares.

If this Letter of Transmittal or any certificates or stock powers are signed by trustees, executors, administrators, guardians, attorneys-in-fact, officers of corporations or others acting in a fiduciary or representative capacity, such persons should so indicate when signing, and proper evidence satisfactory to Purchaser of their authority so to act must be submitted.

If this Letter of Transmittal is signed by the registered owner(s) of the Shares listed and transmitted hereby, no endorsements of Share Certificates or separate stock powers are required unless payment is to be made to, or Share Certificates representing Shares not tendered or accepted for payment are to be issued in the name of, a person other than the registered owner(s), in which case the Share Certificates representing the Shares tendered by this Letter of Transmittal must be endorsed or accompanied by appropriate stock powers, in either case, signed exactly as the name(s) of the registered owner(s) or holder(s) appear(s) on the Share Certificates. Signatures on such Share Certificates or stock powers must be guaranteed by an Eligible Institution.

If this Letter of Transmittal is signed by a person other than the registered owner(s) of the Share(s) listed, the Share Certificate(s) must be endorsed or accompanied by the appropriate stock powers, in either case, signed exactly as the name or names of the registered owner(s) or holder(s) appear(s) on the Share Certificate(s). Signatures on such Share Certificates or stock powers must be guaranteed by an Eligible Institution.

6.   Transfer Taxes.   Except as otherwise provided in this Instruction 6, all transfer taxes with respect to the transfer and sale of Shares contemplated hereby shall be paid or caused to be paid by Purchaser. If payment of the Offer Price is to be made to, or (in the circumstances permitted hereby) if Share Certificates not validly tendered or accepted for payment are to be registered in the name of, any person other than the registered owner(s), or if tendered Share Certificates are registered in the name of any person other than the person signing this Letter of Transmittal, the amount of any transfer taxes (whether imposed on the registered owner(s) or such person) payable on account of the transfer to such person, will need to be paid by such holder.

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7.   Special Payment and Delivery Instructions.   If a check for the Closing Amount is to be issued, and/or Share Certificates representing Shares not validly tendered or accepted for payment are to be issued or returned to, a person other than the signer(s) of this Letter of Transmittal or to an address other than that shown in the box titled “Description of Shares Tendered” above, the appropriate boxes on this Letter of Transmittal should be completed.

8.   Requests for Assistance or Additional Copies.   Questions or requests for assistance may be directed to D.F. King & Co., Inc. (the “Information Agent”) at its address and telephone number set forth below or to your broker, dealer, commercial bank or trust company. Additional copies of the Offer to Purchase, this Letter of Transmittal and other tender offer materials may be obtained from the Information Agent as set forth below, and will be furnished at Purchaser’s expense.

9.   U.S. Federal Backup Withholding.   Under U.S. federal income tax law, a tendering stockholder that is a United States person (as defined for U.S. federal income tax purposes, a “United States person”), and, if applicable, each other U.S. payee, is required to provide the Depository with a correct Taxpayer Identification Number (“TIN”) on IRS Form W-9, which is included herein, and to certify, under penalties of perjury, that such number is correct and that such stockholder or payee is not subject to backup withholding of U.S. federal income tax or otherwise establish a basis for exemption from backup withholding. Failure to provide the information on the IRS Form W-9 may subject the tendering stockholder or payee to backup withholding at the applicable rate (currently 24%), and such stockholder or payee may be subject to a penalty imposed by the IRS. The tendering stockholder or payee should write “Applied For” in the space for the TIN if a TIN has not been issued and the stockholder or payee has applied for a number or intends to apply for a number in the near future. If a TIN has been applied for and the Depository is not provided with a TIN before payment is made, the tendering stockholder or payee will be subject to backup withholding at the applicable rate (currently 24%). See the enclosed IRS Form W-9 and the instructions thereto for additional information.

Certain stockholders or payees (including, among others, corporations and certain non-U.S. persons) may not be subject to backup withholding. Exempt stockholders or payees that are United States persons should furnish their TIN, check the appropriate box on the IRS Form W-9 and sign, date and return the IRS Form W-9 to the Depository to avoid backup withholding. A stockholder or other payee that is not a United States person may qualify as an exempt recipient by providing the Depository with a properly completed IRS Form W-8BEN or IRS Form W-8BEN-E, as applicable, or other appropriate IRS Form W-8, signed under penalties of perjury, attesting to such stockholder or payee’s foreign status or by otherwise establishing an exemption. An appropriate IRS Form W-8 may be obtained from the Depository or the IRS website (www.irs.gov).

Backup withholding is not an additional tax. Rather, the U.S. federal income tax liability of a person subject to backup withholding will be reduced by the amount of tax withheld. If backup withholding results in an overpayment of taxes, a refund or credit may be obtained from the IRS, provided that the required information is timely provided to the IRS.

NOTE:   FAILURE TO COMPLETE AND RETURN THE IRS FORM W-9 (OR APPROPRIATE IRS FORM W-8, AS APPLICABLE) MAY RESULT IN BACKUP WITHHOLDING OF A PORTION OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE OFFER.

10.   Lost, Destroyed, Mutilated or Stolen Share Certificates.   If any Share Certificate has been lost, destroyed, mutilated or stolen, the stockholder should promptly notify Equiniti Trust Company, LLC (the “Transfer Agent”) by telephone (718) 921-8317, fax (718) 765-8758, or toll-free at (877) 248-6417 (toll free in the United States). The stockholder will then be instructed as to the steps that must be taken in order to replace the Share Certificate. This Letter of Transmittal and related documents cannot be processed until the procedures for replacing lost, mutilated, destroyed or stolen Share Certificates have been followed.

11.   Waiver of Conditions.   Purchaser expressly reserves the right, in its sole discretion, to, upon the terms and subject to the conditions of the Offer, increase the Offer Price, waive any Offer Condition (as defined in the Offer to Purchase) or make any other changes to the terms and conditions of the Offer not inconsistent with the terms of the Merger Agreement, provided, however, that without the prior written consent

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of Sage, Supernus and Purchaser will not:

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decrease the Closing Amount or amend the terms of the CVR or the CVR Agreement;

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change the form of consideration payable in the Offer;

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decrease the maximum number of Shares sought to be purchased in the Offer;

•

impose conditions or requirements to the Offer in addition to the Offer Conditions;

•

amend, modify or waive the Minimum Condition, the Termination Condition (each as defined in Annex I to the Merger Agreement) or the conditions set forth in clause (e) or (g) of Annex I to the Merger Agreement;

•

amend or modify any of the other terms of the Offer in a manner that adversely affects, or reasonably could adversely affect, individually or in the aggregate, any holder of Shares in its capacity as such or the ability of Supernus or Purchaser to consummate timely the Offer, the Merger or any of the other Transactions;

•

except as provided in Sections 1.1(c) or 1.1(d) of the Merger Agreement, terminate the Offer or accelerate, extend or otherwise change the Expiration Date; or

•

provide any “subsequent offering period” ​(or any extension thereof) within the meaning of Rule 14d-11 promulgated under the Exchange Act.

Purchaser may not withdraw the Offer prior to any scheduled Expiration Date (or any rescheduled Expiration Date), unless the Merger Agreement is terminated in accordance with its terms.

IMPORTANT:   THIS LETTER OF TRANSMITTAL OR AN AGENT’S MESSAGE, TOGETHER WITH SHARE CERTIFICATE(S) OR BOOK-ENTRY CONFIRMATION AND ALL OTHER REQUIRED DOCUMENTS, MUST BE RECEIVED BY THE DEPOSITARY PRIOR TO THE EXPIRATION DATE.

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