UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Amendment No. 1)

Under the Securities Exchange Act of 1934

AVENUE THERAPEUTICS, INC.

(Name of Issuer)

Common Stock, $0.0001 Par Value

(Title of Class of Securities)

05360L205

(CUSIP Number)

Fortress Biotech, Inc.

c/o Lindsay A. Rosenwald, M.D.

2 Gansevoort Street, 9^th Floor

New York, New York 10014

(212) 554-4366

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

February 17, 2018

(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 §240.13d-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 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).

This amendment to a statement on Schedule 13D relates to the common stock of Avenue Therapeutics, Inc. (the “Issuer”). The Issuer’s principal executive office is located at 2 Gansevoort Street, 9^th Floor, New York, New York 10014.

The Reporting Person is filing this amendment to a Schedule 13D as a result of the acquisition of 273,837 shares of Issuer’s common stock on February 17, 2018 as an issuance under the Founders Agreement (defined below) and to report, in Item 4, the potential sale of the Reporting Person’s interest in the Issuer.

The Reporting Person entered into a Founders Agreement with the Issuer in February 2015, which was amended and restated on September 13, 2016 (the “Founders Agreement”), pursuant to which the Reporting Person assigned to the Issuer all of its rights and interest under its license agreement with Revogenex for IV Tramadol. As consideration for the Founders Agreement, the Issuer assumed $3.0 million in debt that the Reporting Person accumulated for expenses and costs of forming the Issuer and obtaining the IV Tramadol license. As additional consideration for the transfer of rights under the Founders Agreement, the Issuer also: (i) issues annually to the Reporting Person, on the anniversary date of the Founders Agreement, shares of common stock equal to two and one-half percent (2.5%) of the fully-diluted outstanding equity of the Issuer at the time of issuance; and (ii) pays an equity fee in shares of the Issuer common stock, payable within five (5) business days of the closing of any equity or debt financing for the Issuer or any of its respective subsidiaries that occurs after the effective date of the Founders Agreement equal to two and one-half percent (2.5%) of the gross amount of any such equity or debt financing. The Reporting Person waived these rights under the Founders Agreement in the Waiver Agreement executed on November 12, 2018 (described in Item 4 below).

Item 4 of the Schedule 13D is hereby amended and restated in its entirety as follows:

The following describes plans or proposals that the Reporting Person may have with respect to the matters set forth in Item 4(a)-(j) of Schedule 13D:

On November 12, 2018, Issuer, a subsidiary of Reporting Person, entered into a Stock Purchase and Merger Agreement (the “SPMA”) with InvaGen Pharmaceuticals Inc. and its subsidiaries (together, “Buyer”), pursuant to which the Buyer will purchase, for $35 million, common shares representing 33.3% of the fully diluted capitalization of the Issuer (the “Stock Purchase Transaction”) and subsequently acquire the remaining issued and outstanding capital stock of the Issuer for $180 million, subject to certain reductions, in a reverse subsidiary merger transaction (the “Merger Transaction”). Pursuant to the terms and subject to the conditions set forth in the SPMA, the Buyer will, at second closing, hold 100% of the issued and outstanding equity interests of the Issuer. On February 8, 2019, InvaGen acquired 5,833,333 shares of the Company’s common stock at $6.00 (“the Stock Purchase Transaction”) per share for net proceeds of $31.5 million after deducting commission fees and other offering costs, representing a 33.3% stake in the Company’s capital stock on a fully diluted basis.

The aggregate consideration to be paid by the Buyer under the SPMA is $215 million in cash, subject to certain potential reductions, which Buyer intends to have sufficient immediately available funds to pay. In addition, the Issuer is subject to certain lock-up restrictions and agreed not to (subject to customary exceptions), during the period commencing at the signing of the SPMA until the Merger Transaction, issue, buy, sell, or otherwise subject to a security interest, pledge, hypothecation, mortgage or lien, any securities of the Issuer.  

Consummation of the Merger Transaction is conditioned, among other things, upon U.S. Food and Drug Administration (“FDA”) approval of IV Tramadol, its labeling and scheduling and the absence of any Risk Evaluation and Mitigation Strategy restrictions in effect with respect to IV Tramadol, as well as the expiration of any waiting period applicable to the acquisition under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

The SPMA contains customary representations, warranties, covenants and termination rights as well as certain customary closing conditions, including the Issuer’s stockholders approval of the Stock Purchase Transaction and the Merger Transaction.

Stockholders Agreement

Concurrently with the execution and delivery of the SPMA, the Issuer, certain stockholders of the Issuer, including the Reporting Person (the “Stockholders”), and the Buyer entered into a stockholders agreement (the “Stockholders Agreement”), pursuant to which, among other things, the Buyer obtained the right to appoint three directors to the Issuer’s seven member Board of Directors, one of whom must qualify as an independent director, upon the closing of the Stock Purchase Transaction. The Stockholders Agreement also entitles the Buyer to veto rights over certain Issuer actions in the event the Merger Transaction fails to close.

Voting and Support Agreement

Concurrently with the execution and delivery of the SPMA, the Issuer, the Stockholders and the Buyer entered into a voting and support agreement (the “Voting Agreement”), pursuant to which, among other things, the Stockholders will (i) be present at any meeting of the Issuer’s stockholders, in person or represented by proxy, or otherwise cause all of their voting securities to be counted as present for purposes of calculating a quorum, and (ii) vote or cause to be voted (including by proxy or written consent, if applicable) all of their securities in favor of the Proposals (as defined in the SPMA), adjourning or postponing the stockholders meeting to a later date if there are not sufficient votes for the requisite stockholder approval, electing the Buyer Directors (as defined in the Stockholders Agreement) as members of the board of directors of the Issuer or any other matter necessary for the consummation of the Stock Purchase Transaction, Merger Transaction and any other transactions contemplated by the SPMA or the ancillary agreements. Further, pursuant to the Voting Agreement, the Stockholders will vote against any Takeover Proposal (as defined in the SPMA), any other action made in opposition to adoption of the SPMA or the ancillary agreements, any action reasonably expected to materially impede any of the transactions contemplated by the SPMA or the ancillary agreements or any action reasonably expected to result in a breach in any respect of any covenant, representation or warranty or any other obligation or agreement of the Issuer contained in the SPMA, or of the Stockholders contained in the Voting Agreement. In addition, the Stockholders agreed not to transfer any Issuer securities held by them until the earlier of the Merger Transaction and the termination of the SPMA.

Waiver Agreement

Concurrently with the execution and delivery of the SPMA, the Issuer, the Reporting Person and the Buyer entered into a waiver agreement (the “Waiver Agreement”), pursuant to which the Reporting Person irrevocably waived its right to receive the annual dividend of the Issuer’s common shares under the terms of the Class A preferred stock and any fees, payments, reimbursements or other distributions under a certain management services agreement between the Reporting Person and the Issuer and the Founders Agreement, for the period from the effective date of the Waiver Agreement to the termination of the Buyer’s rights under Section 4 of the Stockholders Agreement. Pursuant to the Waiver Agreement, immediately prior to the closing of the Merger Transaction, the Reporting Person will convert all of its preferred shares into common shares pursuant to the terms of the certificate of incorporation of the Issuer, as amended from time to time.

If the Merger Transaction is effected, it would result in one or more of the actions specified in clauses (a) through (j) of Item 4 of the Schedule 13D, including, without limitation, a merger or other extraordinary transaction involving the Issuer, the delisting of the Common Stock from the Nasdaq Global Select Market and the Common Stock becoming eligible for termination from registration pursuant to Section 12(b) of the Act.

(a) – (c) The Reporting Person is the beneficial owner of 3,840,096 shares of the Issuer’s common stock (including 250,000 shares of the Issuer’s Class A preferred stock, which are convertible into common stock). The Reporting Person’s shares of the Issuer’s common stock represent beneficial ownership of 23.3% of the Issuer’s outstanding common stock, based upon 16,502,310 outstanding shares of the Issuer’s common stock as reported by the Issuer on its Form 10-K, filed with the Securities and Exchange Commission on March 12, 2019, and the assumed conversion of the Class A preferred stock.

(d) Except with respect to the Warrants described in Footnote 1, no person has the power to direct the receipt of dividends on or the proceeds of sales of, the shares of common stock owned by the Reporting Person.

(e) Not Applicable.

Reference is made to the Founders Agreement and the Waiver Agreement in Item 3, the SPMA, the Stockholders Agreement, the Voting Agreement and the Waiver Agreement in Item 4, and the Warrants in Footnote 1 above.

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.