UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

Tobira Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

88883P101

(CUSIP Number)

Steve R. Bailey

c/o Frazier Healthcare Partners

601 Union Street, Suite 3200

Seattle, WA 98101

(206) 621-7200

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

November 1, 2016

(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 249.13d-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 §240.13d-7 for other parties to whom copies are to be sent.

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).

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Item 1. Security and Issuer

This Amendment No. 1 (“Amendment No. 1”) to Schedule 13D amends and restates the statement on Schedule 13D originally filed on May 15, 2015 relating to the common stock, $0.001 par value (the “Common Stock”) of Tobira Therapeutics, Inc. (formerly known as Regado Biosciences, Inc.) (the “Issuer” or “Tobira”) having its principal executive office at 701 Gateway Boulevard,
Suite 300, South San Francisco, CA 94080.

Item 2. Identity and Background

(a) Frazier Healthcare V, L.P. (“FH V”);

(b) FHM V, L.P. (“FHM L.P.”), which is the sole general partner of FH V; and FHM V, L.L.C. (“FHM L.L.C.”), which is the sole general partner of FHM L.P.; and

(c) Alan Frazier (“Frazier”), Nader Naini (“Naini”), Patrick Heron (“Heron”), James Topper (“Topper”), Nathan Every (“Every”) (collectively, the “Members”). The Members are all of the members of FHM L.L.C.

The persons named in this Item 2 are referred to individually herein as a “Reporting Person” and collectively as the “Reporting Persons.”

The address of the principal business office of each Reporting Person is:

c/o Frazier Healthcare Partners

601 Union Street, Suite 3200

Seattle, WA 98101

FH V is a venture capital and private equity fund concentrating in healthcare and related fields. The sole business of FHM L.P. and FHM L.L.C. is to serve as general partner entities for FH V. The principal business of each of the Members is to manage FH V, FHM L.P., FHM L.L.C. and a number of affiliated partnerships with similar businesses.

(d) During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in 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.

(e) FH V and FHM L.P. are limited partnerships organized under the laws of the State of Delaware. FHM L.L.C. is a limited liability company organized under the laws of the State of Delaware. Each of the Members is a United States citizen.

Item 3. Source and Amount of Funds or Other Consideration

Not applicable.

Item 4. Purpose of Transaction

Not applicable.

Item 5. Interest in Securities of the Issuer

The Issuer is no longer registered under Section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). As such, each of the Reporting Persons has ceased to beneficially own more than 5% of a voting class of equity securities of the Issuer registered under Section 12 of the Exchange Act.

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

Not applicable.

Item 7. Material to Be Filed as Exhibits

Exhibit 1 – Agreement regarding filing of joint Schedule 13D.

Exhibit 2 – Power of Attorney regarding filings under the Securities Exchange Act of 1934, as amended.

2

SIGNATURE

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.

This Schedule 13D was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 2.

EXHIBIT 1

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need to be filed with respect to the ownership by each of the undersigned of shares of Common Stock of Tobira Therapeutics, Inc.

This Schedule 13D was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 2.

EXHIBIT 2

POWER OF ATTORNEY

KNOW ALL BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Steve R. Bailey with full power to act singly, his true and lawful attorney-in-fact, with full power of substitution, to: (i) sign any and all instruments, certificates and documents that may be necessary, desirable or appropriate to be executed on behalf of himself as an individual or in his capacity as a general partner of any partnership or limited liability company, pursuant to Section 13 or 16 of the Securities Exchange Act of 1934, as amended, and any and all regulations promulgated thereunder, (ii) file the same (including any amendments thereto), with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and any stock exchange or similar authority and (iii) take any other action of any type whatsoever in connection with the foregoing which, in the opinion of such attorney-in-fact, may be of benefit to, in the best interest of, or legally required by, the undersigned, it being understood that the documents executed by such attorney-in-fact on behalf of the undersigned pursuant to this power of attorney shall be in such form and shall contain such terms and conditions as such attorney-in-fact may approve in such attorney-in-fact’s discretion, granting unto said attorney-in-fact full power and authority to do and perform each and every act and thing necessary, desirable or appropriate.

Each of the undersigned hereby grant to the attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact or such attorney-in-fact’s substitute or substitutes, shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted.

This power of attorney shall remain in full force and effect until revoked by the undersigned in a signed writing delivered to the attorney-in-fact.

IN WITNESS WHEREOF, this Power of Attorney has been signed as of the 12^th day of February, 2016.