Exhibit 4.1


 


SIXTH SUPPLEMENTAL INDENTURE


 


This Sixth Supplemental Indenture, dated as
of March 23, 2012 (this “Supplemental Indenture”), among RJ Palmer Partners LLC, a Delaware limited liability
company (the “New Note Guarantor”) and MDC Partners Inc., a corporation continued under the laws of Canada (together
with its successors and assigns, the “Company”), each other Note Guarantor under the Indenture referred to below,
and The Bank of New York Mellon, a New York banking corporation, as Trustee under the Indenture referred to below.


 


WITNESSETH:


 


WHEREAS, the Company, the Note Guarantors
and the Trustee have heretofore executed and delivered an Indenture, dated as of October 23, 2009 (as amended by that certain First
Supplemental Indenture dated as of May 14, 2010, Second Supplemental Indenture dated as of October 23, 2010, Third Supplemental
Indenture dated as of April 19, 2011, Fourth Supplemental Indenture dated as of May 2, 2011 and Fifth Supplemental Indenture dated
as of September 19, 2011, and as may be further amended, supplemented, waived or otherwise modified, the “Indenture”),
providing for the issuance of 11% Senior Notes due 2016 of the Company (the “Notes”);


 


WHEREAS, pursuant to Section 10.7 of the Indenture,
the Company is required to cause each Wholly Owned Subsidiary created or acquired by the Company to execute and deliver to the
Trustee an Additional Note Guarantee; and


 


WHEREAS, pursuant to Section 9.1 of the
Indenture, the Trustee, the Company and existing Note Guarantors are authorized to execute and deliver this Supplemental Indenture
to supplement the Indenture, without the consent of any Holder;


 


NOW, THEREFORE, in consideration of the foregoing
and for other good and valuable consideration, the receipt of which is hereby acknowledged, the New Note Guarantor, the Company,
each other Note Guarantor and the Trustee mutually covenant and agree for the equal and ratable benefit of the holders of
the Notes as follows:


 


ARTICLE
I

DEFINITIONS


 


Section 1.1. Defined Terms. Unless
otherwise defined in this Supplemental Indenture, terms defined in the Indenture are used herein as therein defined.


 


ARTICLE
II

AGREEMENT TO BE BOUND; GUARANTEE


 


Section 2.1. Agreement to be Bound.
The New Note Guarantor hereby becomes a party to the Indenture as a Note Guarantor and as such will have all of the rights and
be subject to all of the obligations and agreements of a Note Guarantor under the Indenture. The New Note Guarantor hereby agrees
to be bound by all of the provisions of the Indenture applicable to a Note Guarantor and to perform all of the obligations and
agreements of a Note Guarantor under the Indenture.


 



    	 



    	 



    

 


Section 2.2. Guarantee. The New Note
Guarantor hereby fully, unconditionally and irrevocably guarantees, as primary obligor and not merely as surety, jointly and severally
with each other Note Guarantor, to each Holder of the Notes and the Trustee, the full and punctual payment when due, whether at
maturity, by acceleration, by redemption or otherwise, of the Obligations, all as more fully set forth in Article X of the
Indenture.


 


ARTICLE
III

MISCELLANEOUS


 


Section 3.1. Notices. Any notice or
communication delivered to the Company under the provisions of the Indenture shall constitute notice to the New Note Guarantor.


 


Section 3.2. Parties. Nothing expressed
or mentioned herein is intended or shall be construed to give any Person, firm or corporation, other than the Holders and the Trustee,
any legal or equitable right, remedy or claim under or in respect of this Supplemental Indenture or the Indenture or any provision
herein or therein contained.


 


Section 3.3. Governing Law etc. This
Supplemental Indenture shall be governed by the provisions set forth in Section 11.7 of the Indenture.


 


Section 3.4. Severability. In case
any provision in this Supplemental Indenture shall be invalid, illegal or unenforceable, the validity, legality and enforceability
of the remaining provisions shall not in any way be affected or impaired thereby and such provision shall be ineffective only to
the extent of such invalidity, illegality or unenforceability.


 


Section 3.5. Ratification of Indenture;
Supplemental Indenture Part of Indenture. Except as expressly amended hereby, the Indenture is in all respects ratified and
confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect. This Supplemental Indenture
shall form a part of the Indenture for all purposes, and every Holder of Notes heretofore or hereafter authenticated and delivered
shall be bound hereby. The Trustee makes no representation or warranty as to the validity or sufficiency of this Supplemental Indenture.
The recitals contained herein shall be taken as statements of the Company, and the Trustee assumes no responsibility for their
correctness.


 


Section 3.6. Duplicate and Counterpart
Originals. The parties may sign any number of copies of this Supplemental Indenture. One signed copy is enough to prove this
Supplemental Indenture. This Supplemental Indenture may be executed in any number of counterparts, each of which so executed shall
be an original, but all of them together represent the same agreement.


 


Section 3.7. Headings. The headings
of the Articles and Sections in this Supplemental Indenture have been inserted for convenience of reference only, are not intended
to be considered as a part hereof and shall not modify or restrict any of the terms or provisions hereof.


 


[Signature Pages Follow]


 



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IN WITNESS WHEREOF, the parties hereto have
caused this Supplemental Indenture to be duly executed as of the date first above written.


 


	 	MDC PARTNERS INC.
	 	 	 	 
	 	By:	 
	 	 	Name:	Michael Sabatino
	 	 	Title:	Authorized Signatory
	 	 	 	 
	 	RJ PALMER PARTNERS LLC,
	 	as New Note Guarantor
	 	 	 	 
	 	By:	 
	 	 	Name:	Michael Sabatino
	 	 	Title:	Authorized Signatory


 





	 	ACCENT MARKETING SERVICES, LLC
	 	ASHTON POTTER CANADA INC.
	 	COMPUTER COMPOSITION OF CANADA LP
	 	BY MDC CANADA GP INC.
	 	CRISPIN PORTER + BOGUSKY CANADA LP
	 	BY MDC CANADA GP INC.
	 	CRISPIN PORTER & BOGUSKY LLC
	 	DOTGLU LLC
	 	KBP HOLDINGS LLC
	 	KBS+P CANADA LP
	 	BY MDC CANADA GP INC.
	 	KIRSHENBAUM BOND SENECAL & PARTNERS LLC
	 	MAXXCOM (USA) HOLDINGS INC.
	 	MAXXCOM INC. (US)
	 	MDC ACQUISITION INC.
	 	MDC CORPORATE (US) INC.
	 	MDC/KBP ACQUISITION INC.
	 	MF+P ACQUISITION CO.
	 	REDSCOUT LLC
	 	TARGETCOM LLC
	 	TC ACQUISITION INC.
	 	VARICK MEDIA MANAGEMENT LLC
	 	YAMAMOTO MOSS MACKENZIE, INC.
	 	ZG ACQUISITION INC.,
	 	each as Note Guarantor




 



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	 	By:	 
	 	 	Name: Michael Sabatino
	 	 	Title: Authorized Signatory


 



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	 	THE BANK OF NEW YORK MELLON,
	 	as Trustee
	 	 	 
	 	By:	 
	 	 	Name: Latoya Elvin
	 	 	Title: Associate


 



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