Investors and security holders are urged to read the definitive proxy statement/prospectus and other
relevant documents filed with the SEC carefully and in their entirety because they contain important information.
Investors and security holders can
obtain free copies of the proxy statement/prospectus and other documents filed with the SEC by Tetraphase, AcelRx and/or Melinta through the web site maintained by the SEC at www.sec.gov. In addition, investors and security holders can obtain free
copies of the proxy statement/prospectus from Tetraphase by written request to Tetraphase Pharmaceuticals, Inc., 480 Arsenal Way, Watertown, Massachusetts 02472, Attn: Secretary or by calling (617) 715-3600.
No Offer or Solicitation
This communication does
not constitute an offer to sell, or the solicitation of an offer to buy, any securities, nor a solicitation of any vote or approval, with respect to the proposed transaction or otherwise. No offering of securities shall be made except by means of a
prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended, and otherwise in accordance with applicable law. If a negotiated transaction between Tetraphase and Melinta is agreed, Tetraphase and Melinta will
prepare filing(s) related to the proposed transaction (including a tender offer statement on Schedule TO, including an offer to purchase, a related letter of transmittal and other tender offer documents related to the transaction and any amendments
thereto, and Tetraphase would file a recommendation statement on Schedule 14D-9 with the SEC and any amendments thereto), and Tetraphase will provide the filing(s) to its stockholders. Tetraphase, and possibly
Melinta, may also file other documents with the SEC regarding the proposed transaction. This document is not a substitute for any tender offer document or any other document which Tetraphase or Melinta may file with the SEC in connection with the
proposed transaction. If a negotiated transaction between Tetraphase and Melinta is agreed, investors and security holders are urged to read the filing(s) and the other relevant materials with respect to the proposed
transaction with Melinta carefully in their entirety when they become available before making any voting or investment decision with respect to any proposed transaction with Melinta, because they will contain important
information about any proposed transaction with Melinta.
Participants in the Solicitation
Tetraphase and its directors and executive officers may be deemed to be participants in the solicitation of proxies from Tetraphase stockholders in respect of
the transactions contemplated by the AcelRx Merger Agreement or the proposed transactions contemplated by the Revised Melinta Proposal or the La Jolla proposal. Information about Tetraphases directors and executive officers is included in
Tetraphases Annual Report on Form 10-K for the year ended December 31, 2019, which was filed with the SEC on March 12, 2020. Other information regarding the participants in the solicitation of
proxies in respect of the transactions contemplated by the AcelRx Merger Agreement, or the transactions contemplated by the Revised Melinta Proposal or the La Jolla proposal, as applicable, and a description of their direct and indirect interests,
by security holdings or otherwise, will be contained in any registration statement, prospectus, proxy statement and other relevant materials to be filed with the SEC if and when they become available.
Forward-Looking Statements
Statements in this Form 8-K contain various forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements include, but are not limited to, those regarding the
transactions contemplated by the AcelRx Merger Agreement and any proposed transaction contemplated by the Revised Melinta Proposal or the La Jolla proposal, the expected timetable for completing any such transactions, future financial and operating
results, benefits and synergies of the transactions, future opportunities for the combined company and any other statements about future expectations, plans and prospects for Tetraphase. The words anticipate, believe,
continue, could, estimate, expect, intend, may, plan, potential, predict, project, should, target,
would and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.
The following factors, among others, could cause actual results to differ materially from those described in these forward-looking statements: the
determinations made by the Tetraphase Board following its evaluation of the Revised Melinta Proposal and the proposal from La Jolla; actions of AcelRx in response to any discussions with