Second Quarter 2024

Alnylam explicitly disclaims any obligation, except to the extent required by law, to update any forward- looking statements. This presentation references non-GAAP financial measures. These measures are not in accordance with, or an alternative to, GAAP, and may be different from non-GAAP financial measures used by other companies. Percentage changes in revenue growth at Constant Exchange Rates, [...] For growth at CER = constant exchange rate – see the Financial Summary slide for more information Note: The safety and efficacy of AMVUTTRA (vutrisiran) for the treatment of ATTR amyloidosis with cardiomyopathy have not been established or evaluated by the FDA, EMA or any other health authority. [...] Positive HELIOS-B Topline Results • Potential for standard of care • Well positioned to address significant unmet need in ATTR-CM • Anchor commercial franchise Increased Financial Guidance • 11% increase in net product revenue guidance at midpoint Strong Revenue Growth • $410 million net product revenues • 34% YoY growth16 Patients: Over 0.5 million on Alnylam RNAi therapeutics globally Pro [...] For growth at CER = constant exchange rate – see the Financial Summary slide for more information Rare Franchise Overall Portfolio $410M Combined Net Product Revenue 34% YoY growth1 vs. Q2’23 12% QoQ growth1 vs. Q1’24 TTR Franchise10 TTR Franchise Update: Q2 2024 1 CER = constant exchange rate, which is a non-GAAP financial measure that represents growth calculated as if exchange rates had remain [...] • Targeted RNAi mechanism enables rapid knockdown of pathogenic protein at the source • Works upstream of approved medicine Unique MOA • Significant reduction in mortality and CV hospitalizations • Substantial impact on measures of disease progression • Consistent effects across all key trial subgroups • Encouraging safety, consistent with established profile Data Support Potential First-Line [...] (+79%): driven by strong demand growth – ROW (+61%): driven by strong demand growth across both EU and partner markets • Modest FX impact (YoY CER1 growth = 26%) $103M Total Rare Global Q2 2024 Net Product Revenues15 Pushkal Garg, M.D. [...] A reconciliation of these non-GAAP financial measures to the comparable GAAP measures, as well as additional information regarding our use of non-GAAP financial measures, are included in the Appendix to this presentation and in our press release dated August 1, 2024, which is accessible in the Investors section of our website at www.alnylam.com. [...] Information regarding our use of non-GAAP financial measures is available in our press release dated August 1, 2024, which is accessible in the Investors section of our website at www.alnylam.com. [...] 3 2024 Non-GAAP Combined R&D and SG&A Expenses guidance are non-GAAP financial measures that exclude from the corresponding GAAP measures stock-based compensation expense estimated at $225M - $275M. [...] Information regarding our use of non-GAAP financial measures is available in our press release dated May 2, 2024, which is accessible in the Investors section of our website at www.alnylam.com.