Exhibit 10.29


 


[SERVIER IP UK LIMITED LETTERHEAD]


 


January 30, 2019


 


 


Enzon Pharmaceuticals, Inc.


685 Route 202/206


Bridgewater, NJ 08807


Attn: Legal Department


Fax: (908) 541-8838


 


 


 


Ladies and Gentlemen:


 


Reference is made to that certain
Asset Purchase Agreement, dated as of November 9, 2009, by and between Klee Pharmaceuticals, Inc.
(“Klee”), Defiante Farmaceutica, S.A. (“Defiante”), and Sigma-Tan Finanziaria S.p.A.
(solely for the purpose of Section 6.4, Section 7.8(a), Section 7.8(e) and Section 12.17 thereof), on the one hand, and Enzon
Pharmaceuticals, Inc. (“Enzon”), on the other hand (the “APA”). Capitalized terms used
in this letter agreement without definition shall have the meanings given to them in the APA.


 


1.                  
Satisfaction of Milestone Payment. Pursuant to Section 3.3(a)(ii) of the APA, Enzon
is entitled to and Servier IP UK shall pay to Enzon US$7,000,000. This payment shall be made by Servier IP UK by wire transfer
within three (3) business days of the date of the reception by Servier IP UK of a copy of the required and completed claim form
sent by Enzon in order to benefit from the provisions of the Double Tax Treaty between the United States and the United Kingdom
regarding the limitation of withholding tax. More precisely for this purpose, the parties of this letter agreement must follow
the following procedure:


 


		a)	Enzon completes the Her Majesty's Revenue and Customs (HRMC) claim form available on the following link: https://www.gov.uk/government/publications/international-tax-uk-usa-double-taxation
convention-form-us-company;



		b)	Enzon sends the completed HMRC claim form together with a copy of the license agreement with the US form 8802 to the Internal
Revenue Service (IRS);



		c)	The claim form is signed/stamped by the IRS which sends it to HMRC together with a US Form 6166 issued by the IRS;



		d)	Enzon sends a copy of the claim form duly signed/stamped by the IRS to Servier IP UK;



		e)	Servier IP UK pays the Milestone to Enzon within three (3) business days of the reception of the claim form duly signed and
completed as indicated above.



The following provisions of this letter agreement shall take
effect once such payment is made.


 


2.                  
Waiver. Pursuant to Section 7.24(a) of the APA, Servier IP UK Limited, as successor-in-interest
to Defiante (“Servier IP UK”), must use, and must cause its Affiliates to use, Applicable Efforts to (a) pursue,
in a reasonably timely manner, the development and approval of SS Oncaspar and SC Oncaspar and (b) implement and conduct all research,
development and clinical manufacturing activities for, and regulatory activities with respect to, SS Oncaspar and SC Oncaspar that
are components of or directly related to or required for the achievement of the milestone payments contemplated by Section 3.3
of the APA. Servier IP UK and Enzon have agreed that Servier IP UK shall not be required to pursue the development of SC Oncaspar
in Europe. As a result, Enzon hereby waives compliance by Servier IP UK with its obligations under Section 7.24(a) of the APA to
use Applicable Efforts to (i) pursue the development of SC Oncaspar in Europe and the approval of SC Oncaspar by the EMEA and (ii)
implement and conduct all research, development and clinical manufacturing activities for, and regulatory activities with respect
to, SC Oncaspar that are components of or directly related to or required for the achievement of the milestone payments contemplated
by Section 3.3(a)(iii) of the APA. Nothing in this paragraph shall be deemed a waiver by Enzon of Servier IP UK’s compliance
with its obligations under Section 3.3(a)(iii) of the APA. 


 






     


     


    

 


3.                  
Consent to Acquisition. Pursuant to Section 3.3(c) of the APA, until the last payment
contemplated by Section 3.3 of the APA has been made to Enzon, Defiante, Klee and their Affiliates shall not sell, assign, transfer,
dispose of or convey any of the Products, including Oncaspar® (and any successor product thereof) or the Business (including
the manufacture, marketing and sale of Oncsapar®) to a third party unless such third party has agreed, in manner reasonably
satisfactory to Enzon, to be bound by the terms and conditions of Section 3.3 of the APA and to assume all of the obligations of
Defiante and Klee contemplated by the APA. The Servier group acquired Shire’s oncology business, including Oncaspar®,
on August 31, 2018 (the “Acquisition”). In connection with the Acquisition, the Servier group acquired 100%
of the equity of Servier IP UK (known at the time of the Acquisition as Sigma-Tau Pharma Limited). Servier IP UK retained all of
its rights and obligations under the APA and remained bound by the terms and conditions of Section 3.3 of the APA. Enzon hereby
(a) consents to the Acquisition, (b) acknowledges and agrees that the Acquisition does not constitute a breach of, default under
or violation of the APA, and (c) waives any rights of prior approval of the Acquisition pursuant to Section 3.3(c) of the APA.


 


4.                  
Provision of Materials. As promptly as reasonably practicable after the date hereof, Enzon shall provide to Servier
IP UK (a) copies of all material written communications between Enzon and Servier IP UK (or any predecessor-in-interest thereto)
relating to the achievement of milestones or the assignment of obligations under the APA, that are reasonably available to Enzon,
including notices, meeting minutes, and other correspondence, (b) copies of all material written communications between Enzon and
Servier IP UK (or any predecessor-in-interest thereto) relating to the APA, that are reasonably available to Enzon, including notices,
notices of breach, and meeting minutes, and (c) copies of all exhibits to the APA.


 


5.                  
Effect of Waivers. The APA is and shall continue to be in full force and effect in accordance with its terms and,
except as expressly set forth in this letter agreement, no other waiver under or modification of the APA is agreed to or implied.


 


6.                  
Governing Law and Forum. This letter agreement shall be governed by, and construed in accordance with, the laws of
the State of Delaware. Section 12.8 of the APA shall also apply to this letter agreement.


 


7.                  
Counterparts. This letter agreement may be executed in any number of counterparts (including by facsimile and .pdf
file), each of which shall be deemed to be an original and all of which together shall be deemed to be one and the same instrument.
The parties to this letter agreement need not execute the same counterpart.


 


 


[Signature Page Follows]






     


     


    







 


If this letter agreement reflects Enzon’s
agreement and understanding, please acknowledge and sign on the next page.


 


 


	 	Sincerely,	 
	 	 	 
	 	Servier
    IP UK Limited	 
	 	 	 
	 	 	 
	 	 	 
	 	By:  	/s/ Claude Bertrand	 
	 	Name: Claude Bertrand	 
	 	Title: Director	 




 


 





[Signature Page to Letter Agreement]









     


     


    

 


Acknowledged and agreed to as of the date first written above:


 


 


	Enzon Pharmaceuticals, Inc.
	 	 
	 	 
	 	 
	By:	/s/ Andrew Rackear	 
	Name: Andrew Rackear	 
	Title: CEO	 
	 	 




 





[Signature Page to Letter Agreement]