EX-4.1



 Exhibit 4.1 

Aratana Therapeutics, Inc. 
 1901
Olathe Boulevard 
 Kansas City, KS 66103 

October 15, 2013 
 Vet Therapeutics, Inc. 

Attention: Geneviève Hansen 
 2683 Via De La Valle, Ste
G-235 
 Del Mar, California 92014 
 Jeffrey Miles 

P.O. Box 1001 
 Ojai, California 93024 

 

	 	Re:	Registration Rights for Company Holders 

 Ladies and Gentlemen: 

Reference is made to (1) that certain Agreement and Plan of Merger, dated as of the date hereof (the “Merger Agreement”), by and among
Aratana Therapeutics, Inc., a Delaware corporation (“Parent”), Jayhawk Acquisition Corporation, a Delaware corporation and direct wholly-owned subsidiary of Parent, Vet Therapeutics, Inc., a Delaware corporation (the
“Company”), and, with respect to Article VIII only of the Merger Agreement, Jeffrey Miles, as Stockholders’ Representative and (2) that certain Share Purchase Agreement, dated on or about the date hereof (the
“Share Purchase Agreement”), by and among Parent and each of those persons and entities listed on the Schedule of Purchasers attached as Exhibit A thereto. Capitalized terms not otherwise defined herein shall have the meaning
ascribed such terms in the Merger Agreement. 
 In consideration of the mutual covenants and agreements herein contained and in the Merger Agreement, and
intending to be legally bound, the parties hereto agree that the Company Holders shall have the resale registration rights and obligations with respect to the Initial Stock Merger Consideration that are set forth in Section 8 of the Share
Purchase Agreement as if the Company Holders were “Purchasers” (as such term is defined in the Share Purchase Agreement) and the Initial Stock Merger Consideration were “Registrable Securities” (as such term is defined in the
Share Purchase Agreement) and shall have the indemnification rights and obligations that are set forth in Section 10 of the Share Purchase Agreement in connection with such resale registration rights and obligations. The undersigned hereby
agree that the Company Holders shall be third-party beneficiaries with respect to this letter agreement, entitled to enforce this letter agreement and such rights and obligations as though each such Company Holder were a party hereto. 







 This letter agreement constitutes the entire agreement of the parties to this letter agreement with respect to
the subject matter contained herein, and supersedes all prior and contemporaneous representations, warranties, understandings and agreements, both written and oral, with respect to such subject matter, except that the following sections of the
Merger Agreement are incorporated herein by reference, with all references therein to the “Agreement” deemed to be references to this letter agreement and not the Merger Agreement: 10.01 (Notices), 10.03 (Counterparts), 10.05
(Severability), 10.07 (Governing Law), 10.08 (Consent to Jurisdiction), 10.09 (Waiver of Jury Trial), 10.12 (Rules of Construction), 10.13 (Assignment), and 10.14 (No Waiver). 

[Signatures Follow] 







 Please sign below to indicate your agreement to the terms and conditions hereof. 

 

									
		 		 		 	Sincerely,
				
		 		 		 	ARATANA THERAPEUTICS, INC.
					
		 		 		 	By:	 	 /s/ Steven St. Peter

		 		 		 	Name:	 	Steven St. Peter
		 		 		 	Title:	 	President & CEO
				
	Accepted and agreed to:	 		 		 	
	
	VET THERAPEUTICS, INC.
					
	By:	 	 /s/ Geneviève Hansen
	 		 		 	
	Name:	 	Geneviève Hansen	 		 		 	
	Title:	 	President	 		 		 	
	
	STOCKHOLDERS’ REPRESENTATIVE
					
	By:	 	 /s/ Jeffrey Miles
	 		 		 	
	Jeffrey Miles