Sec Form 4 Filing - FARALLON PARTNERS L L C/CA @ Lantheus Holdings, Inc. - 2025-08-19

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person FARALLON PARTNERS L L C/CA 2. Issuer Name and Ticker or Trading Symbol Lantheus Holdings, Inc. [ LNTH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) X __ Other (specify below) Member of a Group Owning 10% (Last) (First) (Middle) ONE MARITIME PLAZA, SUITE 2100, 3. Date of Earliest Transaction (MM/DD/YY) 08/19/2025 (Street) SAN FRANCISCO, CA94111 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 08/19/2025 S 41,000 D $ 55.34 6,842,227 I See Footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 ) Common Stock 08/20/2025 S 3,365,000 D $ 56.15 ( 6 ) 3,477,227 I See Footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other FARALLON PARTNERS L L C/CA ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Member of a Group Owning 10% Dapice Joshua J. C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Dreyfuss Philip D C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Dunn Hannah E. C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% FRIED RICHARD B C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Gehani Varun N C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Giauque Nicolas C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Kim David T C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Linn Michael G C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Luo Patrick (Cheng) C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 Member of a Group Owning 10% Signatures /s/ Hannah E. Dunn, Managing Member 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date /s/ Hannah E. Dunn, as attorney-in-fact 08/21/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The entities and individuals identified in the footnotes of this Form 4 may be deemed members of a group holding equity securities of Lantheus Holdings, Inc. (the "Issuer"). The filing of this Form 4 and any statements included herein shall not be deemed to be an admission that such entities and individuals are members of such a group. ( 2 )Since the number of reporting persons that may be listed on a Form 4 is limited, the entities and individuals listed in these footnotes that are not reporting persons on this Form 4 are filing an additional Form 4 on the date hereof as reporting persons with respect to the securities described herein (the "Parallel Form 4"). Information regarding these entities and individuals is included in this Form 4 for purposes of clarification and convenience only, and is duplicative of the information reported in the Parallel Form 4. ( 3 )The amount of securities shown in this row is held directly by certain investment funds affiliated with the reporting persons (the "Farallon Funds"). ( 4 )Farallon Partners, L.L.C. and certain affiliated entities (the "Farallon General Partners"), as general partner or sole member of the general partner, as the case may be, of each of the Farallon Funds, may be deemed to be a beneficial owner of the Issuer's securities held by the Farallon Funds. The Farallon General Partners disclaim any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (the "'34 Act"), or otherwise, except to the extent of their pecuniary interest, if any. ( 5 )Each of Joshua J. Dapice, Philip D. Dreyfuss, Hannah E. Dunn, Richard B. Fried, Varun N. Gehani, Nicolas Giauque, David T. Kim, Michael G. Linn, Patrick (Cheng) Luo, Rajiv A. Patel, Thomas G. Roberts, Jr., Edric C. Saito, William Seybold, Daniel S. Short, Andrew J. M. Spokes, John R. Warren, and Mark C. Wehrly (collectively, the "Managing Members"), as a managing member or manager, or senior managing member or senior manager, as the case may be, of each of the Farallon General Partners, in each case with the power to exercise investment discretion, may be deemed to be a beneficial owner of the Issuer's securities held by the Farallon Funds. Each of the Managing Members disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the '34 Act or otherwise, except to the extent of his or her pecuniary interest, if any. ( 6 )The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $56.14 to $56.55, inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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