First Supplemental Indenture, dated as of June 14, 2018, to the Indenture, dated as of March 11, 2010, among Time Warner Inc., Historic TW Inc., Home Box Office, Inc., Turner Broadcasting System, Inc., West Merger Sub II, LLC and The Bank of New York Mellon, as trustee

Exhibit 4.5

FIRST SUPPLEMENTAL INDENTURE (this “First Supplemental Indenture”) dated as of June 14, 2018, among TIME WARNER INC., a Delaware corporation (the “Company”), HISTORIC TW INC., a Delaware corporation (“HTW”), HOME BOX OFFICE, INC., a Delaware corporation (“HBO”), TURNER BROADCASTING SYSTEM, INC., a Georgia corporation (“TBS”), WEST MERGER SUB II, LLC, a Delaware limited liability company (“Merger Sub LLC”), and THE BANK OF NEW YORK MELLON, a New York banking corporation, as trustee (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Company, HTW, HBO and TBS have executed and delivered to the Trustee an Indenture (the “Indenture”), dated as of March 11, 2010, providing for the issuance and sale by the Company from time to time of its senior debt securities (the “Securities”, which term shall include any Securities issued under the Indenture after the date hereof);

WHEREAS, HTW has, by way of the Indenture, unconditionally and irrevocably guaranteed the obligations of the Company under the Indenture (the “HTW Guarantee”) and extended to the Holders of Securities certain rights and privileges in connection with the HTW Guarantee;

WHEREAS, HBO has, by way of the Indenture, unconditionally and irrevocably guaranteed the obligations of HTW under the HTW Guarantee (the “HBO Guarantee”) and extended to the Holders of Securities certain rights and privileges in connection with the HBO Guarantee;

WHEREAS, TBS has, by way of the Indenture, unconditionally and irrevocably guaranteed the obligations of HTW under the HTW Guarantee (the “TBS Guarantee”) and extended to the Holders of Securities certain rights and privileges in connection with the TBS Guarantee;

WHEREAS, pursuant to the Agreement and Plan of Merger dated as of October 22, 2016 (as it may be amended or otherwise modified from time to time, the “Merger Agreement”), among the Company, AT&T Inc., a Delaware corporation (“AT&T”), West Merger Sub, Inc., a Delaware corporation (“Merger Sub Corp”), and Merger Sub LLC, Merger Sub Corp will merge with and into the Company (the “Initial Merger”), and at the effective time of the Initial Merger (the “First Effective Time”) the separate corporate existence of Merger Sub Corp will cease and the Company will continue as the surviving corporation in the Initial Merger and a wholly-owned subsidiary of AT&T;

WHEREAS, pursuant to the Merger Agreement, immediately following the First Effective Time, the Company, as the surviving corporation in the Initial Merger, will merge with and into Merger Sub LLC (the “Subsequent Merger”), and at the effective time of the Subsequent Merger (the “Second Effective Time”) the separate corporate existence of the Company will cease and Merger Sub LLC will continue as the surviving company in the Subsequent Merger and a wholly-owned subsidiary of AT&T;

WHEREAS, Section 8.01(1)(a) of the Indenture provides that in the case of a merger of the Company into any other Person, the Person into which the Company is merged shall expressly assume by supplemental indenture the due and punctual payment of the principal of (and premium, if any) and interest on all the Securities and the performance of every covenant of the Indenture on the part of the Company to be performed or observed;

WHEREAS, pursuant to Section 8.02 of the Indenture, upon completion of the Subsequent Merger and the execution and delivery of this First Supplemental Indenture, Merger Sub LLC shall succeed to, and be substituted for, and may exercise every right and power of, the Company under the Indenture with the same effect as if Merger Sub LLC had been named as the Company in the Indenture;

WHEREAS, Section 9.01(1) of the Indenture permits the Company, when authorized by a Board Resolution, and the Trustee, at any time and from time to time and without the consent of the Holders of any Securities, to enter into one or more indentures supplemental to the Indenture, in form satisfactory to the Trustee, for the purpose of evidencing the succession of another corporation or Person to the Company, and the assumption by such successor of the covenants of the Company contained in the Indenture and in the Securities;

WHEREAS, the Company is authorized by a Board Resolution to enter into this First Supplemental Indenture; and

WHEREAS, the Company has requested that the Trustee execute and deliver this First Supplemental Indenture, and all requirements necessary to make this First Supplemental Indenture a valid instrument in accordance with its terms, to make the assumption of the obligations of the Company under the Indenture a valid act of Merger Sub LLC and the execution and delivery of this First Supplemental Indenture have been duly authorized in all respects.

NOW, THEREFORE, the Company, HTW, HBO, TBS, Merger Sub LLC and the Trustee hereby agree that this First Supplemental Indenture supplements the Indenture with respect to Securities issued thereunder:

SECTION 1. Definitions. Unless otherwise provided herein, the capitalized terms used and not defined herein have the meanings ascribed to such terms in the Indenture.

SECTION 2. Assumption by Merger Sub LLC. As of the Second Effective Time, Merger Sub LLC, as the surviving company in the Subsequent Merger, hereby assumes the due and punctual payment of the principal of (and premium, if any) and interest on all the Securities and the performance of every covenant of the Indenture (as supplemented from time to time) on the part of the Company to be performed or observed. As of the Second Effective Time, Merger Sub LLC hereby succeeds to, is

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substituted for, and may exercise every right and power of, the Company under the Indenture with the same effect as if Merger Sub LLC had been named as the Company in the Indenture.

SECTION 3. Effectiveness. In the event that the Second Effective Time does not occur on or prior to the Termination Date (as defined in the Merger Agreement), this First Supplemental Indenture shall not become operative and shall be null and void immediately following the Termination Date (as defined in the Merger Agreement).

SECTION 4. This First Supplemental Indenture. This First Supplemental Indenture shall be construed as supplemental to the Indenture and shall form a part of it, and the Indenture is hereby incorporated by reference herein and each is hereby ratified, approved and confirmed.

SECTION 5. GOVERNING LAW. THIS FIRST SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

SECTION 6. Counterparts. This First Supplemental Indenture may be executed in two or more counterparts, each of which shall constitute an original, but all of which when taken together shall constitute but one instrument.

SECTION 7. Headings. The headings of this First Supplemental Indenture are for reference only and shall not limit or otherwise affect the meaning hereof.

SECTION 8. Trustee Not Responsible for Recitals. The recitals herein contained are made by the Company, HTW, HBO, TBS and Merger Sub LLC and not by the Trustee, and the Trustee assumes no responsibility for the correctness thereof. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this First Supplemental Indenture.

SECTION 9. Separability. In case any one or more of the provisions contained in this First Supplemental Indenture or in the Securities shall for any reason be held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect any other provisions of this First Supplemental Indenture or of the Securities, but this First Supplemental Indenture and the Securities shall be construed as if such invalid or illegal or unenforceable provision had never been contained herein or therein.

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IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental Indenture to be duly executed by their respective authorized officers as of the date first written above.

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