13D Filing: Avego Healthcare Capital, LLC and Acer Therapeutics Inc. (ACER)

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

ACER THERAPEUTICS INC.

(Name of Issuer)

common stock
(Title of Class of Securities)

00444P108
(CUSIP Number)

Thomas Vandervort
Avego Healthcare Capital LLC

1055B Powers Place
Alpharetta, GA 30009

(Name, Address and Telephone Number of Person Authorized to

Receive Notices and Communications)

September 19, 2017
(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 (“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).

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Item 1. Security and Issuer

     This Schedule 13D (this Statement) is filed with
respect to the common stock, par value $0.01 per share (Common Stock), of Acer
Therapeutics Inc., a Texas corporation (the Issuer). The address of the
principal executive offices of the Issuer is 222 Third Street, Suite 2240,
Cambridge, MA 02142.

            On
September 19, 2017, the Issuer, formerly known as Opexa Therapeutics, Inc.,
completed its business combination with what was then known as Acer
Therapeutics Inc. (Private Acer) in accordance with the terms of an Agreement
and Plan of Merger and Reorganization, dated as of June 30, 2017, by and among
the Issuer, Opexa Merger Sub, Inc. (Merger Sub) and Private Acer (the Merger
Agreement), pursuant to which Merger Sub merged with and into Private Acer,
with Private Acer surviving as a wholly owned subsidiary of the Issuer (the
Merger). Also on September 19, 2017, in connection with, and prior to the
completion of, the Merger, the Issuer effected a 1-for-10.355527 reverse stock
split of its then outstanding common stock (the Reverse Split).

Item 2. Identity and Background

            (a)        This
Statement is being filed on behalf of entities Avego Healthcare Capital LLC
(Avego) and Avegos controlling Member, Mayura Trust B (Mayura Trust) and
the trustee of Mayura Trust, Mayura One LLC (Mayura One and with each of Avego
and Mayura Trust, a Reporting Entity), and individuals Bala Venkataraman
(BV), Yelena Epova (YE), and Christopher R. Manning (CM) (each a
Reporting Individual, and each Reporting Entity or Reporting Individual, a
Reporting Person). The agreement among the Reporting Persons to file jointly
in accordance with the provisions of Rule 13-d1(k)(l) under the Securities
Exchange Act of 1934, as amended, is attached hereto as Exhibit 1. Each
Reporting Person disclaims beneficial ownership of all securities reported in
this Statement except to the extent of such Reporting Persons pecuniary
interest therein, other than those securities reported herein as being held
directly by such Reporting Person.

            (b)        The
address of the principal offices of Avego, Mayura Trust, Mayura One and the
business address of Bala Venkataraman is 1055B Powers Place, Alpharetta, GA
30009. The business address of Yelena Epova is Five Concourse Parkway, Suite
1000, Atlanta, GA 30328. The business address of Christopher R. Manning is 330
N. Wabash Avenue, Suite 2100, Chicago, IL 60611.

            (c)
Avego is principally involved in the business of finding and investing in
business opportunities. Bala Venkataraman is the sole Manager of Avego and was
appointed as such by the controlling Member of Avego, the Mayura Trust. The
principal business of the Mayura Trust is to hold investment interests for the
beneficiaries of the Mayura Trust. Mayura One serves as the sole trustee of the
Mayura Trust. The Members of Mayura One are Bala Venkataraman, Yelena Epova, and
Christopher R. Manning. Mr. Venkataraman is a private investor and a beneficiary
of the Mayura Trust. Ms. Epova is a partner in the accounting firm of Aprio
located at Five Concourse Parkway, Suite 1000, Atlanta, GA 30328, and Mr.
Manning is partner in the law firm of Burke, Warren, MacKay &Serritella,
P.C. located at 330 N. Wabash Avenue, Suite 2100, Chicago, IL 60611.

            (d)        During
the past five years, none of the Reporting Persons have been convicted in a
criminal proceeding (excluding traffic violations or similar misdemeanors).

            (e)        None
of the Reporting Persons are, nor during the last five years have been, a party
to a civil proceeding of a judicial or administrative body of competent
jurisdiction and as a result of such proceeding 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.

            (f)        Avego
is a limited liability company organized under the laws of the State of
Delaware. Mayura Trust B is a Nevada Trust and Mayura One is a Nevada limited
liability company. Each of the Reporting Individuals is a citizen of the United
States of America.

Item 3. Source and Amount of Funds or Other Consideration

            On
September 19, 2017, Avego purchased 527,983 shares of Private Acer at a price of
$9.47 per share. Thereafter, but again on September 19, 2017, in accordance with
terms of the Merger, the Issuer issued shares of its Common Stock to Private
Acers stockholders, including Avego, at an exchange rate of one share of Common
Stock (after giving effect to the Reverse Split and the conversion of Private
Acers Series A and Series B preferred stock and convertible debt), in exchange
for each share of Private Acers common stock outstanding immediately prior to
the Merger, resulting in Avego receiving 527,983 shares of the Issuers Common
Stock.

            The
source of funds for the purchase by Avego of the Shares reported here was cash
on hand and general working capital.

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Item 4. Purpose of Transaction

            The
information set forth in Item 3 of this Statement is incorporated herein by
reference.

            The
Reporting Persons hold the securities of the Issuer for general investment
purposes. The Reporting Persons may, from time to time, depending on prevailing
market, economic and other conditions, acquire additional shares of Common Stock
or other securities of the Issuer or engage in discussions with the Issuer
concerning further acquisitions of shares of Common Stock or other securities of
the Issuer or further investments in the Issuer. The Reporting Persons intend to
review their investment in the Issuer on a continuing basis and, depending upon
the price and availability of shares of Common Stock or other securities of the
Issuer, subsequent developments affecting the Issuer, the Issuers business and
prospects, other investment and business opportunities available to the
Reporting Persons, general stock market and economic conditions, tax
considerations and other factors considered relevant, may decide at any time to
increase or to decrease the size of their investment in the Issuer.

Item 5. Interest in Securities of the Issuer

            (a)
Amount beneficially owned and percentage of class:

            Avego
is the direct record owner of 527,983 shares of Common Stock. The aggregate
number of shares of Common Stock beneficially owned by Avego is 527,983,
representing approximately 8.18% of the Common Stock outstanding as of September
19, 2017.

            Voting
and investment power with respect to the shares of beneficial interest of the
Issuer owned by Avego may be deemed to be shared by Mayura Trust, Mayura One,
BV, YE and CM. The controlling Member of Avego is Mayura Trust which has the
right to appoint BV as Avegos Manager. The sole Trustee of Mayura Trust is
Mayura One, the members of which, each of whom has the ability to act
independently of the others, are BV, YE and CM. None of Mayura Trust, Mayura
One, BV, YE or CM directly own any shares of Common Stock. Each of Mayura Trust,
Mayura One, BV, YE or CM is the beneficial owner of 527,983 shares of Common
Stock, representing approximately 8.18% of the Common Stock outstanding as of
September 19, 2017.

            Voting
and investment power with respect to the shares of beneficial interest of the
Issuer owned by Avego may be deemed shared by Mayura Trust as the controlling
Member of Avego with the right to appoint the Manager. Mayura Trust does not
directly own any shares of Common Stock. Mayura Trust may be deemed to
beneficially own the 527,983 shares of Common Stock held by Avego, representing
8.18% of the Common Stock outstanding as of September 19,2017.

            Voting
and investment power with respect to the shares of beneficial interest of the
Issuer owned by Avego may be deemed shared by Mayura One as the Trustee of
Mayura Trust. Mayura One does not directly own any shares of Common Stock.
Mayura One may be deemed to beneficially own the 527,983 shares of Common Stock
held by Avego, representing 8.18% of the Common Stock outstanding as of
September 19, 2017.

            Voting
and investment power with respect to the shares of beneficial interest of the
Issuer owned by Avego may be deemed to be shared by BV as the Manager, a
beneficiary of Mayura Trust, and a member of Mayura One. BV does not directly
own any shares of Common Stock. BV may be deemed to beneficially own the 527,983
shares of Common Stock held by Avego, representing approximately 8.18% of the
Common Stock outstanding as of September 19, 2017.

            Voting
and investment power with respect to the shares of capital stock of the Issuer
owned by Avego may be deemed to be shared by each of BV, YE and CM each of whom
is a member of Maura One, which is the trustee of Mayura Trust, which is
entitled to appoint the Manager of Avego. Neither BV, YE nor CM owns any shares
of Common Stock. Each of BV, YE and CM may be deemed to beneficially own the
527,983 shares of Common Stock held by Avego representing approximately 8.18% of
the Common Stock outstanding as of September 19, 2017.

            (b)        Number
of shares of Common Stock as to which such person has:

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            The
percentages of beneficial ownership reported in this Schedule 13D are based on
6,453,260 Common Shares of beneficial interest of the Issuer outstanding as of
September 19, 2017, following the completion of the Issuers Merger, such number
of shares being based on information made publicly available by the Issuer.

            To
the Reporting Persons knowledge, as of September 28, 2017, none of the other
individuals named in Item 2 of this Schedule 13D beneficially own any Common
Shares.

            (c)
Transactions effected in the past sixty days.

            There
have been no reportable transactions with respect to the Common Shares within
the last 60 days by the Reporting Persons, except as described in this Schedule
13D.

            (d)        No
other person is known to have the right to receive, or the power to direct the
receipt of dividends from, or the proceeds from the sale of, the securities
covered by this Schedule 13D.

            (e)        Not
applicable.

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

            Except
as set forth herein, there are no contracts, arrangements, understandings or
relationships among the persons named in Item 2 or between such persons and any
other person with respect to the shares reported.

Item 7. Material to Be Filed as Exhibits

            Exhibit
1: Joint Filing Agreement, dated September 28, 2017 by and among the Reporting
Persons.

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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.

Dated: September 28, 2017

MAYURA TRUST B

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Exhibit 1

JOINT FILING AGREEMENT

The undersigned hereby agree that the foregoing statement on
Schedule 13D is filed on behalf of each of the undersigned, and any amendments
thereto executed by the undersigned shall be filed on behalf of each of the
undersigned without the necessity of filing any additional joint filing
agreement. The undersigned acknowledge that each is responsible for the timely
filing of such statement on Schedule 13D and any amendments thereto, and for the
completeness and accuracy of the information concerning the others of the
undersigned, except to the extent that it knows or has reason to believe that
such information is inaccurate or incomplete. This Joint Filing Agreement may be
executed in any number of counterparts, all of which taken together shall
constitute one and the same instrument.

Date: September 28, 2017

MAYURA TRUST B