Merck (NYSE: MRK) closes multi-year debt issuance with new notes due 2029-2065

Rhea-AI Filing Summary

Merck & Co., Inc. reported that on December 4, 2025 it closed an underwritten public offering of multiple series of senior notes under its automatic shelf registration. The offering includes $500,000,000 aggregate principal amount of Floating Rate Notes due 2029, $750,000,000 of 3.850% Notes due 2029, $1,000,000,000 of 4.150% Notes due 2031 and $1,000,000,000 of 4.450% Notes due 2032.

Merck also issued $1,500,000,000 of 4.750% Notes due 2035, $750,000,000 of 5.500% Notes due 2046, $1,500,000,000 of 5.550% Notes due 2055 and $1,000,000,000 of 5.700% Notes due 2065. The notes were issued under an existing indenture dated January 6, 2010 with U.S. Bank Trust National Association as trustee, and related officers’ certificates and a legal opinion were filed as exhibits.

Insights

Corporate finance analyst

Merck adds long-dated debt across several tranches with fixed and floating rates.

Merck & Co., Inc. has closed an underwritten public offering of multiple note series maturing between 2029 and 2065, with coupons ranging from a floating rate to 5.700%. The tranches include sizeable issuances such as the 4.750% Notes due 2035 and 5.550% Notes due 2055, each at $1,500,000,000 aggregate principal amount, and several billion-dollar tranches in the 2029–2032 range.

The notes are issued under an existing indenture dated January 6, 2010 with U.S. Bank Trust National Association as trustee, suggesting Merck is using a well-established debt framework rather than introducing new structural features. The variety of maturities and coupons indicates a laddered approach to debt, spreading refinancing points over several decades.

This transaction represents a significant addition to Merck’s debt stack but the excerpt does not link it to specific uses such as refinancing, acquisitions or general corporate purposes. Future periodic reports may clarify how these proceeds affect leverage metrics, interest expense and capital allocation priorities.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of

the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) December 4, 2025

Merck & Co., Inc.

(Exact name of registrant as specified in its charter)

New Jersey			1-6571			22-1918501
(State or other jurisdiction			(Commission			(I.R.S Employer
of incorporation)			File Number)			Identification No.)

126 East Lincoln Avenue, Rahway, New Jersey			07065
(Address of principal executive offices)			(Zip Code)

(Registrant’s telephone number, including area code) (908) 740-4000

Not Applicable

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Stock ($0.50 par value)

MRK

New York Stock Exchange

1.875% Notes due 2026

MRK/26

New York Stock Exchange

3.250% Notes due 2032

MRK/32

New York Stock Exchange

2.500% Notes due 2034

MRK/34

New York Stock Exchange

1.375% Notes due 2036

MRK 36A

New York Stock Exchange

3.500% Notes due 2037

MRK/37

New York Stock Exchange

3.700% Notes due 2044

MRK/44

New York Stock Exchange

3.750% Notes due 2054

MRK/54

New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

On December 4, 2025, Merck & Co., Inc. (the “Company”) closed an underwritten public offering of $500,000,000 aggregate principal amount of Floating Rate Notes due 2029 (the “Floating Rate Notes”), $750,000,000 aggregate principal amount of 3.850% Notes due 2029 (the “2029 Notes”), $1,000,000,000 aggregate principal amount of 4.150% Notes due 2031 (the “2031 Notes”), $1,000,000,000 aggregate principal amount of 4.450% Notes due 2032 (the “2032 Notes”), $1,500,000,000 aggregate principal amount of 4.750% Notes due 2035 (the “2035 Notes”), $750,000,000 aggregate principal amount of 5.500% Notes due 2046 (the “2046 Notes”), $1,500,000,000 aggregate principal amount of 5.550% Notes due 2055 (the “2055 Notes”) and $1,000,000,000 aggregate principal amount of 5.700% Notes due 2065 (the “2065 Notes” and, together with the Floating Rate Notes, the 2029 Notes, the 2031 Notes, the 2032 Notes, the 2035 Notes, the 2046 notes and the 2055 Notes, collectively, the “Notes”) under the Company’s Registration Statement on Form S-3ASR (Registration No. 333-278066), originally filed with the Securities and Exchange Commission (the “Commission”) on March 19, 2024, as amended by Post-Effective Amendment No. 1, filed with the Commission on May 14, 2024.

The Notes are being issued under an indenture dated as of January 6, 2010, between the Company and U.S. Bank Trust National Association, as trustee, a copy of which was attached as Exhibit 4.1 to the Company’s Current Report on Form 8-K previously filed with the Securities and Exchange Commission on December 10, 2010 and is incorporated herein by reference. Copies of the officers’ certificate for each series of the Notes (including forms of each of the respective Notes attached thereto) pursuant to Section 301 of the indenture governing the Notes are attached hereto as Exhibits 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 and 4.8 and are incorporated herein by reference. The legal opinion related to these Notes is attached hereto as Exhibit 5.1 and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits 

Exhibit 4.1						Floating Rate Notes due 2029 Officers’ Certificate of the Company dated December 4, 2025, including form of the Floating Rate Notes.
Exhibit 4.2						3.850% Notes due 2029 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2029 Notes.
Exhibit 4.3						4.150% Notes due 2031 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2031 Notes.
Exhibit 4.4						4.450% Notes due 2032 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2032 Notes.
Exhibit 4.5						4.750% Notes due 2035 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2035 Notes.
Exhibit 4.6						5.500% Notes due 2046 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2046 Notes.
Exhibit 4.7						5.550% Notes due 2055 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2055 Notes.
Exhibit 4.8						5.700% Notes due 2065 Officers’ Certificate of the Company dated December 4, 2025, including form of the 2065 Notes.
Exhibit 5.1						Opinion and Consent of Jennifer Zachary, Esq., Executive Vice President and General Counsel of the Company.
Exhibit 23.1						Consent of Jennifer Zachary, Esq., Executive Vice President and General Counsel of the Company (contained in Exhibit 5.1 to this Current Report on Form 8-K).
Exhibit 104						Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: December 4, 2025

Merck & Co., Inc.
By:			/s/ Kelly E. W. Grez
			Kelly E. W. Grez
			Corporate Secretary

FAQ

What did Merck (MRK) announce in this 8-K filing?

Merck & Co., Inc. disclosed that on December 4, 2025 it closed an underwritten public offering of several series of senior notes, with maturities ranging from 2029 to 2065 and a mix of floating and fixed interest rates.

What new notes due 2029 did Merck (MRK) issue?

Merck issued $500,000,000 aggregate principal amount of Floating Rate Notes due 2029 and $750,000,000 aggregate principal amount of 3.850% Notes due 2029.

What longer-dated notes did Merck (MRK) issue out to 2055 and 2065?

Merck issued $1,500,000,000 of 5.550% Notes due 2055 and $1,000,000,000 of 5.700% Notes due 2065, along with $750,000,000 of 5.500% Notes due 2046.

Under what registration statement were Mercks new notes offered?

The notes were offered under Mercks Registration Statement on Form S-3ASR (Registration No. 333-278066), originally filed on March 19, 2024 and amended by Post-Effective Amendment No. 1 filed on May 14, 2024.

Which document governs the new Merck (MRK) notes and who is the trustee?

The notes are governed by an indenture dated January 6, 2010 between Merck & Co., Inc. and U.S. Bank Trust National Association, which serves as trustee.

What exhibits related to the new Merck (MRK) notes were filed?

Merck filed officers certificates for each series of notes as Exhibits 4.1 through 4.8, a legal opinion of Executive Vice President and General Counsel Jennifer Zachary as Exhibit 5.1, a related consent as Exhibit 23.1, and the cover page Inline XBRL data as Exhibit 104.