Engaged Capital SC 13D Aratana Therapeutics, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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)

(Amendment No. )¹

Aratana Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

03874P101

(CUSIP Number)

glenn w. welling

engaged capital, llc

610 Newport Center Drive, Suite 250

Newport Beach, California 92660

(949) 734-7900

STEVE WOLOSKY, ESQ.

OLSHAN FROME WOLOSKY LLP

1325 Avenue of the Americas

New York, New York 10019

(212) 451-2300

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

April 4, 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.

1 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 theNotes).

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Engaged Capital Flagship Master Fund, LP
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			WC
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			CAYMAN ISLANDS
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,189,101
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,189,101
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,189,101
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			4.8%
	14	TYPE OF REPORTING PERSON

			PN

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Engaged Capital Flagship Fund, LP
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			OO
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			DELAWARE
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,189,101
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,189,101
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,189,101
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			4.8%
	14	TYPE OF REPORTING PERSON

			PN

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Engaged Capital Flagship Fund, Ltd.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			OO
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			CAYMAN ISLANDS
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,189,101
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,189,101
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,189,101
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			4.8%
	14	TYPE OF REPORTING PERSON

			CO

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Engaged Capital, LLC
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			OO
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			DELAWARE
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,400,000
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,400,000
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,400,000
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			5.2%
	14	TYPE OF REPORTING PERSON

			OO

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Engaged Capital Holdings, LLC
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			OO
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			DELAWARE
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,400,000
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,400,000
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,400,000
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			5.2%
	14	TYPE OF REPORTING PERSON

			OO

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Glenn W. Welling
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS

			OO
	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			USA
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					2,400,000
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					2,400,000
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			2,400,000
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			5.2%
	14	TYPE OF REPORTING PERSON

			IN

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Craig A. Barbarosh
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS


	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			USA
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					- 0 -
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			0%
	14	TYPE OF REPORTING PERSON

			IN

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Eric J. Ende
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS


	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			USA
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					- 0 -
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			0%
	14	TYPE OF REPORTING PERSON

			IN

CUSIP No. 03874P101


	1	NAME OF REPORTING PERSON

			Lowell W. Robinson
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	SOURCE OF FUNDS


	5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)				☐


	6	CITIZENSHIP OR PLACE OF ORGANIZATION

			USA
NUMBER OF			7	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			8	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			9	SOLE DISPOSITIVE POWER

					- 0 -
			10	SHARED DISPOSITIVE POWER

					- 0 -
	11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES				☐


	13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

			0%
	14	TYPE OF REPORTING PERSON

			IN

CUSIP No. 03874P101

The following constitutes the Schedule 13D filed by the undersigned (the “Schedule 13D”).

Item 1.

Security and Issuer.

This statement relates to the common stock, $0.001 par value per share (the “Shares”), of Aratana Therapeutics, Inc., a Delaware corporation (the “Issuer”). The address of the principal executive offices of the Issuer is 11400 Tomahawk Creek Parkway, Suite 340, Leawood, Kansas 66211.

Item 2.

Identity and Background.

(a)

This statement is filed by:

(i)

Engaged Capital Flagship Master Fund, LP (“Engaged Capital Flagship Master”), a Cayman Islands exempted limited partnership, with respect to the Shares directly and beneficially owned by it;

(ii)

Engaged Capital Flagship Fund, LP (“Engaged Capital Fund”), a Delaware limited partnership, as a feeder fund of Engaged Capital Flagship Master;

(iii)

Engaged Capital Flagship Fund, Ltd. (“Engaged Capital Offshore”), a Cayman Islands exempted company, as a feeder fund of Engaged Capital Flagship Master;

(iv)

Engaged Capital, LLC, a Delaware limited liability company (“Engaged Capital”), as the general partner and investment adviser of Engaged Capital Flagship Master and the investment adviser of a certain managed account (the “Engaged Capital Account”);

(v)

Engaged Capital Holdings, LLC, a Delaware limited liability company (“Engaged Holdings”), as the managing member of Engaged Capital;

(vi)

Glenn W. Welling, as the Founder and Chief Investment Officer (“CIO”) of Engaged Capital and the sole member of Engaged Holdings;

(vii)

Craig A. Barbarosh;

(viii)

Eric J. Ende; and

(ix)

Lowell W. Robinson.

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.” Each of the Reporting Persons is party to that certain Joint Filing and Solicitation Agreement, as further described in Item 6. Accordingly, the Reporting Persons are hereby filing a joint Schedule 13D.

(b) The address of the principal office of each of Engaged Capital Flagship Master and Engaged Capital Offshore is c/o Conyers Trust Company (Cayman) Limited, Cricket Square, Hutchins Drive, P.O. Box 2681, Grand Cayman KY1-1111, Cayman Islands. The address of the principal office of each of Engaged Capital Fund, Engaged Capital, Engaged Holdings and Mr. Welling is 610 Newport Center Drive, Suite 250, Newport Beach, California 92660. The officers and directors of Engaged Capital Offshore and their principal occupations and business addresses are set forth on Schedule A and are incorporated by reference in this Item 2. The principal business address of Mr. Barbarosh is 100 Spectrum Center Drive, Suite 1050, Irvine, California 92618. The principal business address of Dr. Ende is 6231 PGA Blvd., Suite 104-168, Palm Beach Gardens, Florida 33418. The principal business address of Mr. Robinson is 470 West End Avenue, New York, New York 10024.

CUSIP No. 03874P101

(c) The principal business of Engaged Capital Flagship Master is investing in securities. Each of Engaged Capital Fund and Engaged Capital Offshore is a private investment partnership that serves as a feeder fund of Engaged Capital Flagship Master. Engaged Capital is a registered investment advisor and serves as the investment adviser to each of Engaged Capital Flagship Master, Engaged Capital Fund, Engaged Capital Offshore and the Engaged Capital Account. Engaged Capital is also the general partner of each of Engaged Capital Flagship Master and Engaged Capital Fund. Engaged Holdings serves as the managing member of Engaged Capital. Mr. Welling is the Founder and CIO of Engaged Capital, the sole member of Engaged Holdings and a director of Engaged Capital Offshore. Mr. Barbarosh is a partner at the international law firm of Katten Muchin Rosenman LLP. Dr. Ende is President of Ende BioMedical Consulting Group, Inc., a firm focused on helping life sciences companies raise capital, identify licensing partners and optimize corporate structure as well as analyzing both private and public investment opportunities for clients within the life sciences industry. Mr. Robinson is an experienced executive and currently serves as a director of EVINE Live Inc. (f/k/a ShopHQ), a digital omnichannel home shopping network.

(d) No Reporting Person, nor any person listed on Schedule A, annexed hereto, has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

(e) No Reporting Person, nor any person listed on Schedule A, annexed hereto, has during the last five years, been 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) Engaged Capital Flagship Master and Engaged Capital Offshore are organized under the laws of the Cayman Islands. Engaged Capital Fund, Engaged Capital and Engaged Holdings are organized under the laws of the State of Delaware. Messrs. Welling, Barbarosh, Ende and Robinson are citizens of the United States of America. The citizenship of the persons listed on Schedule A is set forth therein.

Item 3.

Source and Amount of Funds or Other Consideration.

The Shares purchased by Engaged Capital Flagship Master and held in the Engaged Capital Account were purchased with working capital (which may, at any given time, include margin loans made by brokerage firms in the ordinary course of business). The aggregate purchase price of the 2,189,101 Shares beneficially owned by Engaged Capital Flagship Master is approximately $10,952,990, including brokerage commissions. The aggregate purchase price of the 210,899 Shares held in the Engaged Capital Account is approximately $1,052,292, including brokerage commissions.

CUSIP No. 03874P101

Item 4.

Purpose of Transaction.

The Reporting Persons purchased the Shares based on the Reporting Persons’ belief that the Shares, when purchased, were undervalued and represented an attractive investment opportunity. Depending upon overall market conditions, other investment opportunities available to the Reporting Persons, and the availability of Shares at prices that would make the purchase or sale of Shares desirable, the Reporting Persons may endeavor to increase or decrease their position in the Issuer through, among other things, the purchase or sale of Shares on the open market or in private transactions or otherwise, on such terms and at such times as the Reporting Persons may deem advisable.

Engaged Capital (together with its affiliates, “Engaged”) has engaged, and intends to continue to engage, in communications with the Issuer’s Board of Directors (the “Board”) and management team regarding means to create stockholder value.

On March 23, 2018, Engaged delivered a letter (the “Nomination Letter”) to the Issuer nominating Craig A. Barbarosh, Eric J. Ende and Lowell W. Robinson (the “Nominees”) for election to the Board at the 2018 annual meeting of stockholders (the “Annual Meeting”).

No Reporting Person has any present plan or proposal which would relate to or result in any of the matters set forth in subparagraphs (a) - (j) of Item 4 of Schedule 13D except as set forth herein or such as would occur upon or in connection with completion of, or following, any of the actions discussed herein. The Reporting Persons intend to review their investment in the Issuer on a continuing basis. Depending on various factors including, without limitation, the Issuer’s financial position and investment strategy, the price levels of the Shares, conditions in the securities markets and general economic and industry conditions, the Reporting Persons may in the future take such actions with respect to their investment in the Issuer as they deem appropriate including, without limitation, engaging in additional communications with management and the Board of the Issuer, engaging in discussions with stockholders of the Issuer and others about the Issuer and the Reporting Persons’ investment in the Issuer and Engaged��s nomination of the Nominees, making proposals to the Issuer concerning changes to the capital allocation strategy, capitalization, ownership structure, a sale of the Issuer, Board structure (including Board composition) or operations of the Issuer, purchasing additional Shares, selling some or all of their Shares, engaging in short selling of or any hedging or similar transaction with respect to the Shares, or changing their intention with respect to any and all matters referred to in Item 4.

Item 5.

Interest in Securities of the Issuer.

(a) The aggregate percentage of Shares reported owned by each person named herein is based upon 45,854,403 Shares outstanding as of March 9, 2018, which is the total number of Shares outstanding as reported in the Issuer’s annual report on Form 10-K filed with the Securities and Exchange Commission on March 14, 2018.

As of the close of business on April 4, 2018, Engaged Capital Flagship Master beneficially owned 2,189,101 Shares, constituting approximately 4.8% of the Shares outstanding. Each of Engaged Capital Fund and Engaged Capital Offshore, as feeder funds of Engaged Capital Flagship Master, may be deemed to beneficially own the 2,189,101 Shares owned by Engaged Capital Flagship Master, constituting approximately 4.8% of the Shares outstanding.

As of the close of business on April 4, 2018, 210,899 Shares were held in the Engaged Capital Account, constituting less than 1% of the Shares outstanding.

Engaged Capital, as the general partner and investment adviser of Engaged Capital Flagship Master and the investment adviser of the Engaged Capital Account, may be deemed to beneficially own the 2,400,000 Shares owned in the aggregate by Engaged Capital Flagship Master and held in the Engaged Capital Account, constituting approximately 5.2% of the Shares outstanding. Engaged Holdings, as the managing member of Engaged Capital, may be deemed to beneficially own the 2,400,000 Shares owned in the aggregate by Engaged Capital Flagship Master and held in the Engaged Capital Account, constituting approximately 5.2% of the Shares outstanding. Mr. Welling, as the Founder and CIO of Engaged Capital and sole member of Engaged Holdings, may be deemed to beneficially own the 2,400,000 Shares owned in the aggregate by Engaged Capital Flagship Master and held in the Engaged Capital Account, constituting approximately 5.2% of the Shares outstanding.

CUSIP No. 03874P101

As of the close of business on April 4, 2018, Messrs. Barbarosh, Ende and Robinson did not beneficially own any Shares, constituting 0% of the Shares outstanding.

Each Reporting Person, as a member of a “group” with the other Reporting Persons for the purposes of Section 13(d)(3) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), may be deemed the beneficial owner of the Shares directly owned by the other Reporting Persons. The filing of this Schedule 13D shall not be deemed an admission that the Reporting Persons are, for purposes of Section 13(d) of the Exchange Act, the beneficial owners of any securities of the Issuer he or it does not directly own. Each of the Reporting Persons specifically disclaims beneficial ownership of the securities reported herein that he or it does not directly own.

(b) By virtue of their respective positions with Engaged Capital Flagship Master, each of Engaged Capital Fund, Engaged Capital Offshore, Engaged Capital, Engaged Holdings and Mr. Welling may be deemed to have sole power to vote and dispose of the Shares reported owned by Engaged Capital Flagship Master.

By virtue of their respective positions with the Engaged Capital Account, each of Engaged Capital, Engaged Holdings and Mr. Welling may be deemed to have sole power to vote and dispose of the Shares held in the Engaged Capital Account.

(c) Schedule B annexed hereto lists all transactions in securities of the Issuer by the Reporting Persons during the past 60 days. All of such transactions were effected in the open market.

(d) No person other than the Reporting Persons is known to have the right to receive, or the power to direct the receipt of dividends from, or proceeds from the sale of, the Shares.

(e) Not applicable.

Item 6.

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

On April 4, 2017, the Reporting Persons entered into a Joint Filing and Solicitation Agreement pursuant to which, among other things, the parties agreed to (a) the joint filing on behalf of each of them of statements on Schedule 13D, and any amendments thereto, with respect to the securities of the Issuer and (b) solicit proxies for the election of the Nominees at the Annual Meeting. A copy of the Joint Filing and Solicitation Agreement is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Engaged Capital Flagship Master has entered into letter agreements pursuant to which it and its affiliates agreed to indemnify Messrs. Barbarosh, Ende and Robinson against claims arising from the solicitation of proxies from the Issuer’s stockholders in connection with the Annual Meeting and any related transactions. A form of the indemnification letter agreement is attached hereto as Exhibit 99.2 and is incorporated herein by reference.

CUSIP No. 03874P101

Other than as described herein, there are no contracts, arrangements, understandings or relationships among the Reporting Persons, or between the Reporting Persons and any other person, with respect to the securities of the Issuer.

Item 7.

Material to be Filed as Exhibits.

99.1

Joint Filing and Solicitation Agreement, dated April 4, 2018.

99.2

Form of Indemnification Letter Agreement.

99.3

Powers of Attorney.

CUSIP No. 03874P101

SIGNATURES

After reasonable inquiry and to the best of his knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: April 5, 2018

Engaged Capital Flagship Master Fund, LP

By:	Engaged Capital, LLC General Partner

By:	/s/ Glenn W. Welling
	Name:	Glenn W. Welling
	Title:	Founder and Chief Investment Officer

Engaged Capital Flagship Fund, LP

By:	Engaged Capital, LLC General Partner

By:	/s/ Glenn W. Welling
	Name:	Glenn W. Welling
	Title:	Founder and Chief Investment Officer

Engaged Capital Flagship Fund, Ltd.

By:	/s/ Glenn W. Welling
	Name:	Glenn W. Welling
	Title:	Director

Engaged Capital, LLC

By:	/s/ Glenn W. Welling
	Name:	Glenn W. Welling
	Title:	Founder and Chief Investment Officer

Engaged Capital Holdings, LLC

By:	/s/ Glenn W. Welling
	Name:	Glenn W. Welling
	Title:	Sole Member

/s/ Glenn W. Welling

Glenn W. Welling

Individually and as attorney-in-fact for Craig A. Barbarosh, Eric J. Ende and Lowell W. Robinson

CUSIP No. 03874P101

SCHEDULE A

Directors and Officers of Engaged Capital Flagship Fund, Ltd.

Name and Position	Principal Occupation	Principal Business Address	Citizenship

Glenn W. Welling Director^*

Mark John Cook Director	Company Director	3rd Floor, Harbour Centre George Town, Grand Cayman Cayman Islands	Australia

Mark Victor Murray Director	Company Director	2F Landmark Square 64 Earth Close Seven Mile Beach Grand Cayman Cayman Islands	United Kingdom & British Overseas Territory Citizen (Cayman Islands)

*Mr. Welling is a Reporting Person and, as such, the information with respect to Mr. Welling called for by Item 2 of Schedule 13D is set forth therein.

CUSIP No. 03874P101

SCHEDULE B

Transactions in Securities of the Issuer During the Past 60 Days

Nature of the Transaction

Securities

Purchased/(Sold)

Price Per

Share($)

Date of

Purchase / Sale

Engaged Capital Flagship Master Fund, LP

Purchase of Common Stock	23,200	4.3692	04/02/2018
Purchase of Common Stock	6,688	4.5064	04/03/2018
Purchase of Common Stock	331,200	4.8726	04/04/2018

Engaged Capital, LLC

(Through the Engaged Capital Account)

Purchase of Common Stock	6,000	4.3692	04/02/2018
Purchase of Common Stock	1,731	4.5064	04/03/2018
Purchase of Common Stock	31,181	4.8726	04/04/2018

Engaged Capital SC 13DAratana Therapeutics, Inc.