Filing Details

Daniel Radden

c/o Armistice Capital, LLC

510 Madison Avenue

7^th Floor

New York, NY 10022

Telephone Number: (212) 231-4930

(Name, Address and Telephone Number of Person Authorized to Receive

Notices and Communications)

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

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The name of the issuer is Tetraphase Pharmaceuticals, Inc., a Delaware corporation (the "Issuer"). The address of the Issuer's principal executive offices is 480 Arsenal Way, Watertown, Massachusetts 02472. This Amendment No. 1 to Schedule 13D relates to the Issuer's Common Stock, $0.001 par value (collectively, the "Shares").

Armistice Capital is an investment adviser registered with the Securities and Exchange Commission (the “SEC”) that is principally engaged in the business of providing investment management services to private investment vehicles, including the Master Fund. The principal business address of Armistice Capital is 510 Madison Avenue, 7^th Floor, New York, New York 10022.

The Master Fund is principally engaged in the business of investing in securities. The principal business address of the Master Fund is c/o dms Corporate Services Ltd., 20 Genesis Close, P.O. Box 314, Grand Cayman KY1-1104, Cayman Islands. The board of directors of the Master Fund consists of Steven Boyd, Kevin A. Phillip and Gregory S. Bennett.

Steven Boyd is the managing member of Armistice Capital and a director of the Master Fund. Mr. Boyd’s business address is 510 Madison Avenue, 7^th Floor, New York, New York 10022.

In connection with the announced proposed merger (the “Merger”) of the Issuer and AcelRx Pharmaceuticals, Inc. (“AcelRx”), on March 15, 2020, the Master Fund entered into a voting agreement (the “Voting Agreement”) with: (i) AcelRx; and (ii) Consolidation Merger Sub, Inc. (the “Merger Sub”), a wholly-owned subsidiary of AcelRx. Pursuant to the Voting Agreement, the Master Fund agreed to, among other things: (i) vote all of its Shares and warrants of the Issuer entitled to be voted in favor of (A) adopting the Agreement and Plan of Merger dated March 15, 2020 by and among the Issuer, AcelRx and the Merger Sub (the “Merger Agreement”), and (B) any matter that would reasonably be expected to facilitate the Merger; (ii) certain restrictions on its ability to take actions with respect to the Issuer and its Shares; and (iii) the amount of shares of AcelRx’s common stock and other consideration it will receive in exchange for its warrants of the Issuer upon consummation of the Merger. The Voting Agreement will terminate upon the first to occur of: (i) the termination of the Merger Agreement; (ii) the effective time of the Merger; (iii) any amendment to the Merger Agreement that reduces the amount, or changes the form, of consideration payable to the Master Fund in the transactions contemplated by the Merger and related agreements; (iv) a Company Adverse Change in Recommendation (as such term is defined in the Merger Agreement); or (v) the mutual written consent of the Master Fund and AcelRx.

The foregoing was a summary of certain material terms of the Voting Agreement. The foregoing description is not, and does not purport to be, complete and is qualified in its entirety by reference to the full text of the form of Voting Agreement, which has been filed as Exhibit B hereto and is incorporated herein by reference.

Mr. Boyd and Keith Maher, a Managing Director at Armistice Capital, currently serve as members of the Issuer’s board of directors (the “Board”).

The Reporting Persons purchased the Shares for investment in the ordinary course of their investment activities based on the Reporting Persons’ belief that the Shares, when purchased, were undervalued and represented an attractive investment opportunity. The Reporting Persons intend to review their investment in the Issuer on a continuing basis. Depending on various factors including, without limitation, the Issuer’s financial position, the price levels of the Shares, conditions in the securities markets and general economic and industry conditions, the Reporting Persons may in the future take such actions with respect to their investment in the Issuer as they deem appropriate including, without limitation, engaging in communications with management and/or the Board, engaging in discussions with stockholders of the Issuer and others about the Issuer and the Reporting Persons’ investment, reshaping the Issuer's corporate strategy, revitalizing the Issuer’s promising Research and Development pipeline, restructuring the Issuer’s expense base, recommending business development transactions including mergers and acquisitions, proposing changes to management, operations and the structure of the Board (including the composition of the Board), purchasing additional Shares, selling some or all of their Shares, engaging in short selling of or any hedging or similar transaction with respect to the Shares, or changing their intention with respect to any and all matters referred to in subparagraphs (a) - (j) of Item 4 of Schedule 13D.

Except as otherwise set forth herein, the Reporting Persons do not have any present plans or proposals which would relate to, or result in, the matters set forth in subparagraphs (a) – (j) of Item 4 of Schedule 13D. However, subject to market conditions and in compliance with applicable securities laws, the Reporting Persons reserve the right, at a later date, to effect one or more of such changes or transactions in the number of Shares they may be deemed to beneficially own in open-market or privately negotiated transactions, on such terms and at such times as the Reporting Persons may deem advisable.

As of the date hereof, each of the Reporting Persons may be deemed to be the beneficial owner of 1,419,507 Shares, constituting 19.6% of the Shares, based upon 7,259,236 Shares outstanding as of the date hereof. Each of the Reporting Persons has the sole power to vote or direct the vote of 0 Shares and the shared power to vote or direct the vote of 1,419,507 Shares. Each of the Reporting Persons has the sole power to dispose or direct the disposition of 0 Shares and the shared power to dispose or direct the disposition of 1,419,507Shares.

There have been no transactions in the Shares by the Reporting Persons since the last Schedule 13D filed by the Reporting Persons in respect of the Issuer.

(e)

N/A

The information set forth in Item 4 above is incorporated by reference in its entirety in this Item 6. The Reporting Persons do not have any contract, arrangement, understanding or relationship with any person with respect to securities of the Issuer that is not described herein or in the initial Schedule 13D filed by the Reporting Persons in respect of the Issuer.

Exhibit A: Joint Filing Agreement

Exhibit B: Form of Voting Agreement (incorporated by reference to Exhibit 10.3 to the Form 8-K filed with the SEC by the Issuer on March 16, 2020)

Name: Steven Boyd

Title: Managing Member

Name: Steven Boyd

Title: Director

Name: Steven Boyd

Title: Managing Member

Name: Steven Boyd

Title: Director