SC 13D

UNITED STATESSECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. __)*

Tetraphase Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.001

(Title of Class of Securities)

88165N204

(CUSIP Number)

Michael Hearne
La Jolla Pharmaceutical Company
4550 Towne Centre Court
San Diego, CA 92121
(858) 207-4264

Copies to:

Ryan A. Murr
Gibson, Dunn & Crutcher LLP
555 Mission Street, Suite 3000
San Francisco, CA 94105
(415) 393-8200 James J. Moloney
Gibson, Dunn & Crutcher LLP
3161 Michelson Drive, Suite 1200
Irvine, CA 92612
(949) 451-3800

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

June 15, 2020

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to be sent.

* 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.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(Continued on following pages)

CUSIP NO. 88165N204
1. Names of Reporting Persons.
La Jolla Pharmaceutical Company
2. Check the Appropriate Box if a Member of a Group (a) ☐ (b) ☐
3. SEC Use Only
4. Source of Funds WC
5. Check If Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6. Citizenship or Place of Organization California
Number of Shares Beneficially Owned by Each Reporting Person With	7. Sole Voting Power 1,085,000
	8. Shared Voting Power 0
	9. Sole Dispositive Power 1,085,000
	10. Shared Dispositive Power 0
11. Aggregate Amount Beneficially Owned by Each Reporting Person 1,085,000
12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares £
13. Percent of Class Represented by Amount in Row (11) 14.9%
14 Type of Reporting Person CO

Item 1. Security and Issuer

This Statement on Schedule 13D (the “Statement” or “Schedule 13D”) relates to the common stock, par value $0.001 (the “Common Stock”), of Tetraphase Pharmaceuticals, Inc., a Delaware corporation (the “Issuer”). The principal executive office of the Issuer is located at 480 Arsenal Way, Watertown, Massachusetts 02472.

Item 2. Identity and Background

This Statement is being filed by La Jolla Pharmaceutical Company (the “Reporting Person”).

Information Regarding Each Reporting Person

La Jolla Pharmaceutical Company

The business address of La Jolla Pharmaceutical Company is:

4550 Towne Centre Court

San Diego, CA 92121

La Jolla Pharmaceutical Company is a corporation dedicated to the development and commercialization of innovative therapies that improve outcomes in patients suffering from life-threatening diseases.

Information Regarding Legal Proceedings

To the knowledge of the Reporting Person, it has not been convicted in a criminal proceeding or been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which such party was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Citizenship

La Jolla Pharmaceutical Company is a California corporation.

Item 3. Source and Amount of Funds or Other Consideration

The Reporting Person has expended an aggregate of approximately $2.7 million to purchase 1,085,000shares of the Issuer’s Common Stock. Such purchases were effected through the open-market. The Reporting Person used its own funds for the purchases, none of which were borrowed or otherwise obtained from any other source for the purpose of acquiring, holding, trading or voting the securities.

Item 4. Purpose of Transaction

The Reporting Person is engaged in the pharmaceutical business. The Issuer, a biopharmaceutical company, has received multiple bids in support of an acquisition of the Issuer. On each of May 6, 2020 and May 11, 2020, the Reporting Person sent the Issuer a letter offering to purchase the Issuer at a premium to the purchase price the Issuer had accepted from another prospective purchaser. Before the Reporting Person was able to fully engage with the Issuer on the Reporting Person’s offer, the Issuer entered into an acquisition agreement with another prospective purchaser at a purchase price higher than that offered by the Reporting Person. The Reporting Person sent the Issuer another bid letter on June 19, 2020, once more offering to acquire the Issuer at a premium to the then-current purchase price. The Reporting Person has purchased shares of Common Stock of the Issuer for the purpose of advancing the acquisition proposal it delivered to the Issuer on June 19, 2020. At this time, the Reporting Person does not intend to obtain control of the Issuer through a hostile tender offer or proxy process; instead, the Reporting Person continues to offer and pursue a competing bid for the acquisition of the Issuer.

The Reporting Person may take such actions in the future with respect to its investment in the Issuer’s Common Stock as it deems advisable, including, without limitation, purchasing additional shares, selling shares, entering into hedging transactions with respect to the shares and/or otherwise changing its intention with respect to the matters referred to in Item 4 of Schedule 13D. Such actions will depend on various factors including, without limitation, the Issuer’s response to the Reporting Person’s bids, the Issuer’s financial and strategic direction and position, the price performance of the Issuer’s Common Stock, general conditions in the Issuer’s industry, the economy and securities markets, and the availability of other investment opportunities.

Item 5. Interest in Securities of the Issuer

(a)    Amount beneficially owned and percentage of class:

La Jolla Pharmaceutical Company            1,085,000 shares, representing 14.9% of the class

La Jolla Pharmaceutical Company is the beneficial owner of 1,085,000 shares of the Issuer’s Common Stock. La Jolla Pharmaceutical Company has sole voting and dispositive power over such shares of Common Stock.

The percentage ownership used herein is based upon 7,263,236 shares of Common Stock of the Issuer issued and outstanding as of the close of business on June 2, 2020, as set forth in the Solicitation/Recommendation Statement on Schedule 14D-9 filed by the Issuer with the United States Securities and Exchange Commission on June 12, 2020.

(b)    Voting and disposition powers:

Sole power to vote or direct the vote:

La Jolla Pharmaceutical Company                                1,085,000 shares

Shared power to vote or direct the vote:

La Jolla Pharmaceutical Company                                0 shares

Sole power to dispose or direct the disposition:

La Jolla Pharmaceutical Company                                1,085,000 shares

Shared power to dispose or direct the disposition:

La Jolla Pharmaceutical Company                                0 shares

(c)

The Reporting Persons have engaged in the following transactions in the Issuer’s Common Stock during the last 60 days:

Entity	Transaction	Trade Date	Shares	Price/Share
La Jolla Pharmaceutical Company	Purchase	6/10/2020	13,129	$2.2002
La Jolla Pharmaceutical Company	Purchase	6/11/2020	86,871	$2.1836
La Jolla Pharmaceutical Company	Purchase	6/11/2020	250,000	$2.3271
La Jolla Pharmaceutical Company	Purchase	6/12/2020	10,000	$2.3387
La Jolla Pharmaceutical Company	Purchase	6/15/2020	66,445	$2.3785
La Jolla Pharmaceutical Company	Purchase	6/16/2020	83,555	$2.4864
La Jolla Pharmaceutical Company	Purchase	6/16/2020	109,841	$2.4642
La Jolla Pharmaceutical Company	Purchase	6/17/2020	100,159	$2.4951
La Jolla Pharmaceutical Company	Purchase	6/18/2020	130,302	$2.4495
La Jolla Pharmaceutical Company	Purchase	6/19/2020	234,698	$2.6161

(d)

No person other than a Reporting Person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, Shares beneficially owned by the Reporting Persons.

(e)

Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer

None.

Item 7. Materials to Be Filed as Exhibits

Exhibit	Description
1	Letter from La Jolla Pharmaceutical Company, dated May 6, 2020, to Tetraphase Pharmaceuticals, Inc.
2	Letter from La Jolla Pharmaceutical Company, dated May 11, 2020, to Tetraphase Pharmaceuticals, Inc.
3	Letter from La Jolla Pharmaceutical Company, dated June 19, 2020, to Tetraphase Pharmaceuticals, Inc.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

June 22, 2020

LA JOLLA PHARMACEUTICAL COMPANY
By:	/s/ Michael Hearne
	Michael Hearne
	Chief Financial Officer

EX-1

4550 Towne Centre Court | San Diego, California 92121

May 6, 2020

Board of Directors

Tetraphase Pharmaceuticals, Inc.

480 Arsenal Way, Suite 100

Watertown, MA 02472

Dear Members of the Board:

On behalf of La Jolla Pharmaceutical Company, I am pleased to submit this non-binding proposal to acquire 100% of the equity of Tetraphase Pharmaceuticals, Inc. for $22 million in cash plus an additional $12.5 million potentially payable under CVRs to be issued in the transaction. The $22 million upfront consideration would include amounts payable under the Black-Scholes put provisions in Tetraphase’s outstanding warrants and be subject to a minimum, to-be-agreed-upon closing net cash balance. The terms of the CVRs would match those set forth in Tetraphase’s merger agreement with AcelRx Pharmaceuticals, Inc., except that payments pursuant to the CVRs would be made in cash instead of cash or stock at the acquiror’s option.

We are impressed with the growth potential of XERAVA and excited about the potential benefits of combining two companies focused on delivering important therapies to patients in the ICU. Like Tetraphase, La Jolla is dedicated to the development and commercialization of therapies that improve outcomes in critically ill patients. In 2017, La Jolla’s first product, GIAPREZA (angiotensin II), was approved by the FDA as a treatment for septic or other distributive shock. In 2019, GIAPREZA was approved by the European Commission. GIAPREZA net sales were $23.1 million in 2019, up 129% from $10.1 million in 2018. La Jolla’s second product, LJPC‑0118 (artesunate), is under FDA review as a potential treatment for severe malaria.

As of March 31, 2020, La Jolla had $77.2 million of cash and no debt. La Jolla would fund 100% of the purchase price with cash on hand. Accordingly, this offer is not subject to any financing contingencies and would not require a vote by the La Jolla shareholders.

This proposal is subject to due diligence, which we believe we can complete by May 11, 2020. Following completion of our diligence review, we would expect to deliver an execution-ready version of a definitive merger agreement on the same day.

We look forward to discussing our proposal with you further.

Sincerely,

Kevin Tang

Chairman

EX-2

4550 Towne Centre Court | San Diego, California 92121

May 11, 2020

Board of Directors

Tetraphase Pharmaceuticals, Inc. 480 Arsenal Way, Suite 100

Watertown, MA 02472

Dear Members of the Board:

On behalf of La Jolla Pharmaceutical Company (“La Jolla”), I am pleased to submit the enclosed execution-ready version of a definitive Merger Agreement (the “Merger Agreement”) to acquire 100% of the equity of Tetraphase Pharmaceuticals, Inc. (“Tetraphase”) for $22.3 million in cash, plus an additional $12.5 million potentially payable under CVRs to be issued in the transaction.

The upfront cash consideration will be paid as follows: (i) $1.00 per share of Tetraphase common stock (including common stock underlying RSUs, PSUs and pre-funded warrants),

(ii)$1.41 per share underlying the 2019 Black-Scholes Warrants, and (iii) $1.45 per share underlying the 2020 Black-Scholes Warrants. As contemplated in your current merger agreement with AcelRx Pharmaceuticals, Inc. (“AcelRx” and such merger agreement, the “AcelRx Merger Agreement”), the consideration payable to the holders of the Black-Scholes Warrants would be fixed in a Support Agreement to be executed concurrent with execution of the Merger Agreement.

We believe that our offer constitutes a “Superior Offer” as defined under the AcelRx Merger Agreement. In particular, we note the following:

• The La Jolla Board of Directors has approved the transaction and authorized our execution of the Merger Agreement, subject to your termination of the AcelRx Merger Agreement.

• Our proposal is not subject to any financing contingencies. We stand ready to fund 100% of the purchase price with cash on hand (as of March 31, 2020, La Jolla had $77.2 million of cash and no debt).

• We have reduced the $5 million Company Net Cash condition and Target Net Cash level in the AcelRx Merger Agreement to $4.19 million to offset the termination fee payable by Tetraphase to AcelRx.

• Our offer is structured as a tender offer rather than a merger, which means that no stockholder vote is needed nor is a Registration Statement on Form S-4 required. As a result, our transaction can be completed on an accelerated timeline.

Board of Directors

Tetraphase Pharmaceuticals, Inc. May 11, 2020

Page 2

• In an effort to put the parties in a position to move quickly, we have agreed to use the form of the AcelRx Merger Agreement with revisions to implement the enhancements described above. We have also enclosed a redline of the Merger Agreement, marked to show changes from the AcelRx Merger Agreement.

We would like to thank you for your consideration, and we remain excited about the prospect of working together towards the successful and expeditious consummation of our proposal, which we believe will deliver enhanced value to Tetraphase’s stockholders.

Sincerely,

Kevin Tang

Chairman

Enclosures:

Merger Agreement (with exhibits)

Form of Support Agreement

2

EX-3

4550 Towne Centre Court | San Diego, California 92121

June 19, 2020

Board of Directors

Tetraphase Pharmaceuticals, Inc. 480 Arsenal Way, Suite 100

Watertown, MA 02472

Dear Members of the Board:

On behalf of La Jolla Pharmaceutical Company (“La Jolla”), I am pleased to submit the enclosed execution-ready version of a definitive Merger Agreement (the “Merger Agreement”) to acquire 100% of the equity of Tetraphase Pharmaceuticals, Inc. (“Tetraphase”) for $43.0 million in cash, plus an additional $16.0 million potentially payable under CVRs to be issued in the transaction.

The upfront cash consideration will be paid as follows: (i) $2.00 per share of Tetraphase common stock (including common stock underlying RSUs and PSUs and pre-funded warrants), $2.68 per share underlying the 2019 Black-Scholes Warrants, and (iii) $2.69 per share underlying the 2020 Black-Scholes Warrants. As contemplated in your current merger agreement with Melinta Therapeutics, Inc. (“Melinta” and such merger agreement, the “Melinta Merger Agreement”), the consideration payable to certain holders of the Black-Scholes Warrants would be fixed in either a Support Agreement or Exchange Agreement to be executed concurrent with execution of the Merger Agreement.

We believe that our offer constitutes a “Superior Offer” as defined under the Melinta Merger Agreement. In addition, we note the following:

• The La Jolla Board of Directors has approved the transaction and authorized our execution of the Merger Agreement, subject to your termination of the Melinta Merger Agreement.

• Our proposal is not subject to any financing contingencies. We stand ready to fund 100% of the purchase price with cash on hand (as of March 31, 2020, La Jolla had $77.2 million of cash and no debt).

• In an effort to put the parties in a position to move quickly, we have agreed to use the form of the Melinta Merger Agreement. We have enclosed a redline of the Merger Agreement, marked to show changes from the Melinta Merger Agreement.

Board of Directors

Tetraphase Pharmaceuticals, Inc. June 19, 2020

Page 2

We remain excited about the prospect of working together towards the successful and expeditious consummation of our proposal, which we believe will deliver enhanced value to Tetraphase’s stockholders, and we would like to thank you for your continued consideration.

Sincerely,

Kevin Tang Chairman

Enclosure:

Merger Agreement (with exhibits)