The defendants believe that the Plumley, Sahan, Giacobbe, Ravi,
Garity, Kashavena, Waters, Gardner, Kopczynski and Lapi complaints are without merit.
See
The MergerLitigation Relating to the Merger beginning on page 90 of this proxy statement/prospectus for more information about litigation relating to the Merger that has been commenced prior to the date of this proxy
statement/prospectus. There can be no assurance that additional complaints will not be filed with respect to the Merger.
One of the
conditions to completion of the Merger is the absence of any applicable law (including any order) being in effect that prohibits completion of the Merger. Accordingly, if a plaintiff is successful in obtaining an order prohibiting completion of the
Merger, then such order may prevent the Merger from being completed, or from being completed within the expected timeframe.
The disclosure under the
heading The MergerLitigation Relating to the Merger is hereby supplemented by replacing the paragraphs in that section, beginning with the first full paragraph on page 90 of the proxy statement/prospectus, with
the following:
On April 9, 2020, a putative class action complaint was filed against Tetraphase, each of its directors, AcelRx
and Merger Sub in the United States District Court for the District of Delaware. The lawsuit, captioned Plumley v. Tetraphase Pharmaceuticals, Inc., et al., Case No.
1:20-cv-00496 and purportedly brought on behalf of a class of stockholders, alleges that Tetraphase and its directors violated Section 14(a) of the Exchange Act and
Rule 14a-9 promulgated thereunder, and that Tetraphases directors, AcelRx and Merger Sub violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading
registration statement in connection with the Merger. On April 16, 2020, a complaint was filed against Tetraphase and certain of its directors in the United States District Court for the Southern District of New York. The lawsuit, captioned
Sahan v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-03069, alleges that the defendants violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act and breached their fiduciary duty of candor/disclosure, by allegedly disseminating a materially
incomplete and misleading registration statement in connection with the Merger. On April 20, 2020, a complaint was filed against Tetraphase and its directors in the United States District Court for the District of Massachusetts. The lawsuit,
captioned Giacobbe v. Tetraphase Pharmaceuticals, Inc. et al., Case No. 1:20-cv-10762, alleges that the defendants violated Section 14(a) of the Exchange Act
and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading registration
statement in connection with the Merger. On April 20, 2020, a complaint was filed against Tetraphase and certain of its directors in the United States District Court for the Southern District of New York. The lawsuit, captioned Ravi v.
Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-03142, alleges that the defendants violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading registration statement in
connection with the Merger. On April 22, 2020, a putative class action complaint was filed against Tetraphase, each of its directors, AcelRx, and Merger Sub in the United States District Court for the District of Delaware. The lawsuit,
captioned Garity v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-00542, alleges that the defendants violated Section 14(a) of the Exchange Act
and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading registration
statement in connection with the Merger. On April 23, 2020, a putative class action complaint was filed against Tetraphase, certain of its directors, AcelRx and Merger Sub in the Middlesex County Superior Court. The lawsuit, captioned
Kashavena v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 2081-cv-01005, alleges that the individual defendants breached their fiduciary duties of care,
loyalty/good faith and candor/disclosure by allegedly entering into the Merger through a flawed and unfair process and disseminating a materially incomplete and misleading registration statement in connection with the Merger. The Kashavena
complaint alleges that Tetraphase, AcelRx and Merger Sub aided and abetted in the alleged breach of fiduciary duties. On April 24, 2020, a complaint was filed against Tetraphase and its directors in the United States District Court for the
Eastern District of New York. The lawsuit, captioned Waters v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-01896, alleges that the defendants
violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a
materially incomplete and misleading registration statement in connection with the Merger. On April 29, 2020, a complaint was filed against Tetraphase and certain of its directors in the United States District Court for the Southern District of
New York. The lawsuit, captioned Gardner v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-03352, alleges that the defendants violated
Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially
incomplete and misleading registration statement in connection with the Merger. On May 1, 2020, a complaint was filed against Tetraphase and certain of its directors in the United States District Court for the Southern District of New York. The
lawsuit, captioned Kopczynski v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-03426, alleges that the defendants violated Section 14(a) of the
Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading
registration statement in connection with the Merger. On May 4, 2020, a complaint was filed against Tetraphase and certain of its directors in the United States District Court for the Southern District of New York. The lawsuit, captioned
Lapi v. Tetraphase Pharmaceuticals, Inc., et al., Case No. 1:20-cv-03452, alleges that the defendants violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and that the individual defendants violated Section 20(a) of the Exchange Act, by allegedly disseminating a materially incomplete and misleading registration statement in
connection with the Merger.