UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 13D

[Rule 13d-101]

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(a)

AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2(a)

REATA PHARMACEUTICALS, INC.

(Name of Issuer)

CLASS A COMMON STOCK, $.001 PAR VALUE

(Title of Class of Securities)

75615P 103

(CUSIP Number)

J. WARREN HUFF, PRESIDENT AND CHIEF EXECUTIVE OFFICER

REATA PHARMACEUTICALS, INC.

2801 GATEWAY DRIVE, SUITE 150

IRVING, TEXAS 75063

(972) 865-2219

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

May 25, 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 240.13d-1(g), check the following box.  ¨

Note. Schedules filed in paper format shall include a signed original and five copes 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 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 relates to the Class A common stock, par value $0.001 per share (the “Class A Common Stock”), of Reata Pharmaceuticals, Inc., a Delaware corporation (the “Issuer”). The principal executive offices of the Issuer are located at 2801 Gateway Drive, Suite 150, Irving, Texas 75063.

ITEM 2. IDENTITY AND BACKGROUND.

The reporting person filing this Schedule 13D is J. Warren Huff. Mr. Huff and his spouse, Winifred Huff, may be deemed to share voting and dispositive power over the shares of common stock held by the Huff 2010 Descendants’ Trust (the “Trust”) as members of the Trust’s Investment Committee.

The business address of Mr. Huff, Mrs. Huff and the Trust is 2801 Gateway Drive, Suite 150, Irving, Texas 75063.

Mr. Huff’s principal occupation is President and Chief Executive Officer of the Issuer, a clinical stage biopharmaceutical company. Mrs. Huff’s principal occupation is as an attorney. The principal business of the Trust is holding investments for the trust beneficiaries.

Mr. Huff and Mrs. Huff are citizens of the United States, and the Trust is a Delaware trust.

Neither Mr. Huff, Mrs. Huff nor the Trust have, during the last five years, been convicted in a criminal proceeding or 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.

ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

The information set forth in Item 2, Item 5 and Item 6 is hereby incorporated by reference in its entirety.

Prior to the Issuer’s initial public offering of Class A Common Stock (the “IPO”), each of Mr. Huff and the Trust held 760,079 and 38,400 outstanding shares of Class B common stock of the Issuer, par value $0.001 per share (“Class B Common Stock”), , which were acquired over several years through various means, including (i) shares issued to Mr. Huff in connection with the founding of the Issuer, (ii) shares purchased by Mr. Huff in private placements using his personal funds; and (iii) shares (including restricted stock) granted to Mr. Huff in connection with his service as the Issuer’s Chief Executive Officer. Shares of Class B Common Stock are convertible into shares of Class A Common Stock on a one-for-one basis (a) at the holder’s election at any time after the date that is six months following the date of the closing of the initial public offering of the Shares, (b) at the holder’s election prior to that time subject to certain conditions, or (c) at the option of the Issuer’s board of directors, in its sole discretion, at any time or multiple times from time to time on or before the closing of the IPO.

Upon effectiveness of the Issuer’s Registration Statement on Form 8-A on May 25, 2016, filed in connection with the IPO, Mr. Huff became the deemed beneficial owner of 801,863 shares of Class A Common Stock. Upon the closing of the IPO, approximately 8% of the shares of Class B Common Stock of each of Mr. Huff and the Trust automatically converted into shares of Class A Common Stock for no additional consideration. Additionally, Mr. Huff acquired 114,000 shares of the Issuer’s Class A Common Stock at a purchase price of $11.00 per share from the underwriters in the IPO with personal funds.

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ITEM 4. PURPOSE OF TRANSACTION.

The shares of Class A Common Stock and Class B Common Stock described herein were acquired by Mr. Huff for investment purposes. Mr. Huff has no present plans or proposals for disposition of the shares beneficially owned by him or for acquisition of additional shares. Mr. Huff, however, expects to evaluate on a continuing basis his goals and objectives, other business opportunities available to him, and general economic and equity market conditions, as well as the Issuer’s business operations and prospects. Based on such evaluations, Mr. Huff may change his plans and intentions and may determine to sell or otherwise dispose of some or all of the shares beneficially owned by him or to acquire additional shares. In addition, Mr. Huff may, from time to time, transfer shares beneficially owned by him for tax or other economic planning purposes.

Except as set forth above, Mr. Huff has no present plans or intentions which would result in or relate to any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D.

ITEM 5. INTEREST IN SECURITIES OF ISSUER.

The information set forth in Item 2, Item 3 and Item 6 is hereby incorporated by reference in its entirety.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER.

The information set forth in Item 2, Item 3 and Item 5 is hereby incorporated by reference in its entirety.

Mr. Huff and the Trust are subject to a Lock-Up Agreement, dated October 15, 2015, as extended by that certain Lock-up Extension dated March 28, 2016, 2016 (the “Lock-Up Agreement”), pursuant to which Mr. Huff agreed with the underwriters in the IPO, on behalf of himself and his affiliates, for a period of 180 days following May 25, 2016, subject to certain exceptions, that he and his affiliates will not, directly or indirectly, offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale, or otherwise dispose of or hedge any of the Issuer’s shares of common stock, any options or warrants

Page 4 of 6 Pages

to purchase any shares of the Issuer’s common stock, or any securities convertible into, or exchangeable for or that represent the right to receive shares of the Issuer’s common stock. Citigroup Global Markets Inc. and Cowen and Company, LLC, on behalf of the underwriters, may, in their sole discretion, at any time without prior notice, release all or any portion of the shares from the restrictions in any such agreement.

Mr. Huff is a party to that certain Seventh Amended and Restated Registration Rights Agreement dated as of November 10, 2010 (the “Registration Rights Agreement”), pursuant to which holders of more than 67% of the registrable shares of the Issuer, at any time at least six months after the completion of the IPO, may twice request that the Issuer effect the registration of at least 50% of the registrable shares held by all holders of registration rights, or a lesser number of shares if the aggregate price to the public of the offering (net of underwriter discounts) will be at least $5 million. Furthermore, if Form S-3 is available for an offering by the initiating holders, the initiating holders may request that the Issuer effect an unlimited number of registrations on Form S-3 at an aggregate offering price of at least $1,000,000 per registration on Form S-3. In addition, the holders of registrable securities have piggyback registration rights if the Issuer determines to register any equity securities for its own account or the account of another security holder (other than in the IPO). The Issuer will pay the registration expenses, other than underwriting fees, discounts or commissions, of the shares registered pursuant to the registrations described above, but limited to four registrations on Form S-3. The Registration Rights Agreement terminates with respect to any holder who is permitted to sell, within a 90-day period, all of such holder’s registrable shares in compliance with Rule 144.

Mr. Huff us a party to an Employment Agreement with the Issuer dated September 23, 2015 (the “Employment Agreement”). Among other things, the Employment Agreement provides for accelerated vesting of certain equity awards of Mr. Huff under certain circumstances.

To Mr. Huff’s knowledge, there are no other contracts, arrangements, understandings or relationships (legal or otherwise) among the persons named in Item 2 and between such him and any person with respect to any securities of the Issuer.

The descriptions contained in this Statement on Schedule 13D of the Lock-Up Agreement, the Registration Rights Agreement and the Employment Agreement are summaries only and are qualified in their entireties by the actual terms of each such agreement, which are incorporated herein by this reference. See Item 7 “Material to be Filed as Exhibits.”

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.

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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.

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Exhibit 7.1

Lock-up Agreement

Reata Pharmaceuticals, Inc.

Public Offering of Common Stock

October 16, 2015

Citigroup Global Markets Inc.

Cowen and Company, LLC

As Representatives of the several Underwriters,

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

Ladies and Gentlemen:

This letter is being delivered to you in connection with the proposed Underwriting Agreement (the “Underwriting Agreement”) between Reata Pharmaceuticals, Inc., a Delaware corporation (the “Company”), Citigroup Global Markets Inc. and Cowen and Company, LLC (together, the “Representatives”) as representatives of a group of Underwriters named therein, relating to an underwritten public offering of Class A Common Stock, $0.001 par value per share (the “Common Stock”), of the Company (the “Offering”).

In order to induce you and the other Underwriters to enter into the Underwriting Agreement, the undersigned will not, without the prior written consent of the Representatives, offer, sell, contract to sell, pledge or otherwise dispose of (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the undersigned or any affiliate of the undersigned or any person in privity with the undersigned or any affiliate of the undersigned), directly or indirectly, including the filing (or participation in the filing) of a registration statement (other than the registration statement relating to the Offering) with the Securities and Exchange Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations of the Securities and Exchange Commission promulgated thereunder with respect to, any shares of capital stock of the Company or any securities convertible into, or exercisable or exchangeable for such capital stock, or publicly announce an intention to effect any such transaction, for a period from the date hereof until 180 days after the date of the Underwriting Agreement (the “Lock-Up Period”). If the undersigned is an officer or director of the Company, the undersigned further agrees that the foregoing restrictions shall be equally applicable to any issuer-directed shares of Common Stock the undersigned may purchase in the Offering.

The provisions of the immediately preceding paragraph shall not apply to or prohibit any of the following: (i) transfers, dispositions, or distributions of shares of capital stock of the Company by the undersigned (or any security convertible into or exercisable or exchangeable for shares of common stock) (a) as a bona fide gift, (b) to limited partners, members, stockholders or trust beneficiaries of the undersigned or to any investment fund or other entity controlled or managed by the undersigned, (c) by will or other testamentary document or by intestacy, and (d) to any trust for the direct or indirect benefit of the undersigned or the immediate family of the undersigned (for the purposes of this letter, “immediate family” shall mean any relationship by blood, current or former marriage or adoption, not more remote than first cousin) in a transaction not involving a disposition for value, provided that, in the case of any transfer, disposition or distribution pursuant to the above four subclauses, each donee, transferee or distributee shall sign and deliver a lock-up letter in the form of this letter, and with respect to (a), (b) and (d) above, no filing under Section 16(a) of the Exchange Act, or other public announcement, reporting a reduction in beneficial ownership of shares of capital stock of the Company, shall be required or shall be voluntarily made by the undersigned or any other person in connection therewith during the Lock-Up Period; (ii) the exercise of options to purchase shares of capital stock of the Company granted under any stock incentive plan or stock purchase plan described in the prospectus filed in connection with the Offering, provided that the underlying shares issuable upon exercise thereof shall continue to be subject to the restrictions on transfer set forth in this letter; (iii) transfers of shares of capital stock of the Company to the Company in connection with the termination of the undersigned’s employment with the Company; (iv) establishment of a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of capital stock of the Company, provided that such plan does not provide for the transfer of such capital stock during the Lock-Up Period and no filing with the SEC or other public announcement shall be required or shall be voluntarily made by the undersigned or any other person in connection therewith during the Lock-Up Period; (v) transfers or dispositions of shares of Common Stock purchased in the Offering from the Underwriters (other than issuer-directed shares of Common Stock purchase in the Offering by an officer or director of the Company) or on the open market following the Offering; or (vi) transfers of shares of capital stock of the Company pursuant to a bona fide third-party tender offer for all outstanding shares of the Company, merger, consolidation or other similar transaction made to all holders of the Company’s securities involving a change of control of the Company that has been approved by the board of directors of the Company, provided that (a) the shares of capital stock of the Company held by the undersigned that are not transferred pursuant to such tender offer, merger, consolidation or other similar transaction shall remain subject to all of the restrictions set forth in this letter, (b) if such transaction is not completed, all shares of capital stock of the Company held by the undersigned shall remain subject to the provisions of this letter, and (c) for purposes of this paragraph, “change of control” shall mean the consummation of any bona fide third party tender offer for any and all of the Company’s share capital or any merger, consolidation or other similar transaction the result of which is that any “person” (as defined in Section 13(d)(3) of the Exchange Act), or group of persons, other than the Company, becomes the beneficial owner (as defined in Rules 13d-3 and 13d-5 of the Exchange Act) of 50% of the total voting power of the voting securities of the Company.

If the undersigned is an officer or director of the Company, (i) the Representatives agree that, at least three business days before the effective date of any release or waiver of the foregoing restrictions in connection with a transfer of any shares of capital stock of the Company, the Representatives will notify the Company of the impending release or waiver, and (ii) the Company has agreed in the Underwriting Agreement to announce the impending release or waiver by press release through a major news service at least two business days before the effective date of the release or waiver. Any release or waiver granted by the Representatives hereunder to any such officer or director shall only be effective two business days after the publication date of such press release. The provisions of this paragraph will not apply if (a) the release or waiver is effected solely to permit a transfer not for consideration and (b) the transferee has agreed in writing to be bound by the same terms described in this letter to the extent and for the duration that such terms remain in effect at the time of the transfer.

If for any reason the Underwriting Agreement shall be terminated prior to the Closing Date (as defined in the Underwriting Agreement), the agreement set forth above shall likewise be terminated, and the agreement set forth above shall automatically terminate if the Underwriting Agreement has not been entered into between the Representatives and the Company prior to May 1, 2016.

Exhibit 7.2

March 28, 2016

Citigroup Global Markets Inc.

Cowen and Company, LLC

As Representatives of the several Underwriters,

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

Ladies and Gentleman:

Reference is made to that certain lock-up agreement, the Lock-Up Agreement, by and among the undersigned and Citigroup Global Markets Inc. and Cowen and Company, LLC (together, the “Representatives”), in connection with the proposed public offering of Class A Common Stock, $0.001 par value per share, of the Reata Pharmaceuticals, Inc. The undersigned hereby agrees that the last paragraph of the Lock-Up Agreement shall be replaced with the clause below, such that the Lock-Up Agreement shall not expire until December 15, 2016:

“If for any reason the Underwriting Agreement shall be terminated prior to the Closing Date (as defined in the Underwriting Agreement), the agreement set forth above shall likewise be terminated, and the agreement set forth above shall automatically terminate if the Underwriting Agreement has not been entered into between the Representatives and the Company prior to December 15, 2016.”

This letter agreement will not change or supersede any other terms of the Lock-Up Agreement and all other terms and conditions set forth therein shall remain in full effect.

Exhibit 7.5

POWER OF ATTORNEY

FOR EXECUTING FORMS 3, FORMS 4, FORMS 5,

FORM 144 AND SCHEDULE 13D AND 13G

The undersigned hereby constitutes and appoints Michael D. Wortley or Anne T. Yager, or any of them acting without the other, with full power of substitution, as the undersigned’s true and lawful attorney-in-fact to:

The undersigned hereby grants to the attorney-in-fact full power and authority to do and perform all and every act 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 the attorney-in-fact shall lawfully do or cause to be done by virtue of this Power of Attorney and the rights and powers granted herein. The undersigned acknowledges that the attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming (nor is Reata Pharmaceuticals, Inc. assuming) any of the undersigned’s responsibilities to comply with Section 16 of the Exchange Act.

The undersigned agrees that the attorney-in-fact may rely entirely on information furnished orally or in writing by or at the direction of the undersigned to the attorney-in-fact. The undersigned also agrees to indemnify and hold harmless Reata Pharmaceuticals, Inc. and the attorney-in-fact against any losses, claims, damages or liabilities (or actions in these respects)

that arise out of or are based upon any untrue statements or omissions of necessary facts in the information provided by or at the direction of the undersigned, or upon the lack of timeliness in the delivery of information by or at the direction of the undersigned, to the attorney-in fact for purposes of executing, acknowledging, delivering or filing a Form 3, Form 4, Form 5, Form 144, Schedule 13D or Schedule 13G (including any amendments, corrections, supplements or other changes thereto) with respect to the undersigned’s holdings of and transactions in securities issued by Reata Pharmaceuticals, Inc., and agrees to reimburse Reata Pharmaceuticals, Inc. and the attorney-in-fact on demand for any legal or other expenses reasonably incurred in connection with investigating or defending against any such loss, claim, damage, liability or action.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Form 3, Form 4, Form 5, Form 144, Schedule 13D and Schedule 13G (including any amendments, corrections, supplements or other changes thereto) with respect to the undersigned’s holdings of and transactions in securities issued by Reata Pharmaceuticals, Inc., unless earlier revoked by the undersigned in a signed writing delivered to the attorney-in-fact. This Power of Attorney does not revoke any other power of attorney that the undersigned has previously granted.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of the date written below.