13D Filing: Engaged Capital and Aratana Therapeutics Inc. (PETX)

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.