shall be deemed to be furnished, and not filed: 99.1 Press Release dated July 30, 2026 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: July 30, 2026 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Finan…

Director — Benjamin F. Cravatt, Ph.D.: Dr. Benjamin F. Cravatt was elected to the Board of Directors and will serve as a Class III director.

shall be deemed to be furnished, and not filed: 99.1 Press Release dated April 30, 2026 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: April 30, 2026 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Fin…

Yvonne Greenstreet, M.D., M.B.A.: Grant of a special equity award to the CEO for continued leadership and incentivization.

shall be deemed to be furnished, and not filed: 99.1 Press Release dated February 12, 2026 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: February 12, 2026 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chi…

Results of Operations and Financial Condition. On January 11, 2026, Alnylam Pharmaceuticals, Inc. (the “Company”) announced its new five-year strategy, “ Alnylam 2030, ” as well as its preliminary fourth quarter and full year 2025 global net product revenues of approximately $995 million and $2,987 million, respectively, for AMVUTTRA® (vutrisiran), ONPATTRO® (patisiran), GIVLAARI® (givosiran) and OXLUMO® (lumasiran), and provided the Company’s 2026 product and pipeline goals. The Company also…

Other Events. On December 10, 2025, Alnylam Pharmaceuticals, Inc. (the “Company”) entered into separate, privately negotiated repurchase agreements with certain holders of its 1.00% convertible senior notes due 2027 (the “Notes”) to repurchase for cash (the “Repurchases”) approximately $34.4 million aggregate principal amount of the Notes for a total repurchase cost (including accrued and unpaid interest) of approximately $51.9 million. The final aggregate cash repurchase price is subject to…

Director — Michael W. Bonney, Carolyn Bertozzi, Ph.D.: Two directors resigned and a new director was elected to succeed them.

shall be deemed to be furnished, and not filed: 99.1 Press Release dated October 30, 2025 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: October 30, 2025 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief…

Entry into a Material Definitive Agreement. On September 30, 2025 (the “Closing Date”), Alnylam Pharmaceuticals, Inc. (the “Company”) entered into a Credit Agreement (the “Credit Agreement”) among the lenders party thereto, Bank of America, N.A., as Administrative Agent, and the other parties named therein. The Credit Agreement provides for a $500.0 million revolving line of credit (the “Revolving Credit Facility”), including a $150.0 million letter of credit sublimit. The Credit Agreement pr…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information contained in

Entry Into or Amendment of a Material Definitive Agreement. Indenture and Notes On September 12, 2025, Alnylam Pharmaceuticals, Inc. (the “Company”) completed its previously announced offering of $575.0 million in aggregate principal amount of 0.00% Convertible Senior Notes due 2028 (the “Initial Notes”). On September 10, 2025, the initial purchasers in such offering exercised their option to purchase an additional $86.25 million in aggregate principal amount of the Company’s 0.00% Convertibl…

Unregistered Sales of Equity Securities. The information set forth under

Creation of a Direct Financial Obligation or an Off-Balance Sheet Arrangement. The information set forth under

Other Events. Concurrently with the pricing of the Notes, the Company entered into privately negotiated transactions (the “note repurchase transactions”) with certain holders of the Company’s 1.00% convertible senior notes due 2027 (the “existing notes”) to repurchase for cash approximately $637.8 million aggregate principal amount of the existing notes for a total repurchase cost (including accrued and unpaid interest) of approximately $1,105.8 million. The terms of each note repurchase tran…

Other Events. On September 8, 2025, Alnylam Pharmaceuticals, Inc. (the “Company”) issued a press release relating to the commencement of its proposed offering of convertible senior notes due 2028 to persons reasonably believed to be qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the “Convertible Note Offering”). On September 9, 2025, the Company issued a press release relating to the pricing of the Convertible Note Offering. Copies of the pr…

shall be deemed to be furnished, and not filed: 99.1 Press Release dated July 31 , 2025 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: July 31, 2025 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Fina…

Executive Vice President, Chief Research and Development Officer / Executive Vice President, Chief Scientific Officer — Pushkal Garg, M.D. / Kevin Fitzgerald, Ph.D.: The R&D Combination and expansion of responsibilities for Drs. Garg and Fitzgerald, along with changes in their compensation.

shall be deemed to be furnished, and not filed: 99.1 Press Release dated May 1, 2025 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: May 1, 2025 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Financial…

Director — Phillip A. Sharp, Ph.D.: Dr. Sharp retired from the Board but will continue to serve on the Scientific Advisory Board.

shall be deemed to be furnished, and not filed: 99.1 Press Release dated February 13, 2025 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: February 13, 2025 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chi…

Results of Operations and Financial Condition On January 12, 2025, Alnylam Pharmaceuticals, Inc. (the “Company”) announced its preliminary fourth quarter and full year 2024 global net product revenues of approximately $451 million and $1,646 million, respectively, for ONPATTRO® (patisiran), AMVUTTRA® (vutrisiran), GIVLAARI® (givosiran) and OXLUMO® (lumasiran), and provided the Company’s 2025 product and pipeline goals. The Company also announced full year 2025 combined net product revenue gui…

shall be deemed to be furnished, and not filed: 99.1 Press Release dated October 3 1, 2024 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: October 31, 2024 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chie…

shall be deemed to be furnished, and not filed: 99.1 Press Release dated August 1 , 2024 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: August 1, 2024 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Fi…

shall be deemed to be furnished, and not filed: 99.1 Press Release dated M ay 2, 2024 . 104 Cover Page Interactive Data File (embedded within the Inline XBRL document). SIGNATURE 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: May 2, 2024 ALNYLAM PHARMACEUTICALS, INC. By: /s/ Jeffrey V. Poulton Jeffrey V. Poulton Executive Vice President, Chief Financia…