This Amendment No. 1 (this Amendment) amends and supplements the Tender
Offer Statement on Schedule TO (together with any amendment and supplement thereto, this Schedule TO), filed with the Securities and Exchange Commission (the SEC) on June 12, 2020, which relates to the offer by Toronto
Transaction Corp., a Delaware corporation (Purchaser), a wholly owned subsidiary of Melinta Therapeutics, Inc., a Delaware corporation (Melinta), to purchase all outstanding shares of common stock, $0.001 par value per share
(Shares), of Tetraphase Pharmaceuticals, Inc., a Delaware corporation (Tetraphase), at a price of $1.79 per Share, net to the holder in cash, without interest, plus one non-transferable
contractual contingent value right (CVR) per Share, which represents the right to receive one or more payments in cash, currently estimated to be up to $1.48 per CVR, assuming the anticipated maximum number of CVRs are issued and
contingent upon the achievement of certain specified milestones, calculated as described in the Offer to Purchase dated June 12, 2020 (together with any amendments or supplements thereto, the Offer to Purchase) and in the accompanying
Letter of Transmittal (together with any amendments or supplements thereto and with the Offer to Purchase, the Offer), which are annexed to and filed with this Schedule TO as Exhibits (a)(1)(A) and (a)(1)(B), respectively. Melinta is
controlled by Deerfield Private Design Fund III, L.P., a Delaware limited partnership (DP III), and Deerfield Private Design Fund IV, L.P., a Delaware limited partnership (DP IV and, together with DP III, the Deerfield
Funds), which are managed by Deerfield Management Company, L.P., a Delaware series limited partnership (Series C) (Deerfield Management and, together with the Deerfield Funds, Deerfield). This Schedule TO is being filed
on behalf of Melinta and Purchaser. Unless otherwise indicated, references to sections in this Schedule TO are references to sections of the Offer to Purchase. A copy of the Agreement and Plan of Merger, dated as of June 4, 2020, among
Tetraphase, Melinta and Purchaser is attached as Exhibit (d)(1) hereto and incorporated herein by reference with respect to Items 4 through 11 of this Schedule TO.
This Amendment is being filed solely to amend and supplement items to the extent specifically provided herein. Except as otherwise set forth
in this Amendment, the information set forth in the Schedule TO, including all exhibits thereto, remains unchanged and is incorporated herein by reference to the extent relevant to the items in this Amendment. This Amendment should be read together
with the Schedule TO.
ITEMS 1 THROUGH 9 AND ITEM 11.
Items 1 through 9 and Item 11 of the Schedule TO, and Section 10 of the Offer to Purchase entitled Background of the Offer; Contacts
with Tetraphase, are hereby amended and supplemented as follows:
On June 19, 2020, Tetraphase gave written notice to
Melinta and Purchaser that it received a proposed offer from La Jolla Pharmaceutical Company (La Jolla) to acquire Tetraphase for $43.0 million in cash, plus an additional $16.0 million in cash potentially payable under
contingent value rights to be issued in the transaction (the La Jolla Proposal). Under the La Jolla Proposal, the upfront cash consideration would be paid as follows: (i) $2.00 per share of Tetraphase common stock (including common stock
underlying restricted stock units, performance-based stock units and pre-funded warrants), (ii) $2.68 per share of Tetraphase common stock underlying the common stock warrants issued by Tetraphase in November
2019, and (iii) $2.69 per share of Tetraphase common stock underlying the common stock warrants issued by Tetraphase in January 2020. On June 21, 2020, the Tetraphase Board of Directors determined that the proposal constituted a Superior Offer.
Tetraphase publicly announced the La Jolla Proposal on June 22, 2020.
Pursuant to the Merger Agreement, Melinta and Purchaser had
four business days to propose any revisions to the terms of the Offer or make any other proposals that would cause the proposed offer from La Jolla to no longer constitute a Superior Offer. On June 22, 2020, Melintas legal advisors
notified Tetraphases legal advisors that Melinta had reviewed the determination notice sent by Tetraphase notifying Melinta that the Tetraphase Board had determined that the La Jolla Proposal was a Superior Offer, and that Melinta was willing
to willing to waive its four business day match rights under the Melinta merger agreement to permit Tetraphase to, prior to the expiration of the otherwise applicable four business day match period, terminate the Merger
Agreement, make a Company Adverse Change in Recommendation and pay to Melinta the required termination fee of $1,150,000 under the Merger Agreement. After receiving such correspondence, Tetraphases financial advisors at Janney Montgomery Scott
LLC spoke with representatives of Deerfield and Melinta, and such representatives from Deerfield and Melinta confirmed that Melinta did not intend to propose any revisions to the terms of the Offer or make any other proposals such that the La Jolla
Proposal would no longer constitute a Superior Offer
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