May 9, 2025

Gisele Dion
Chief Accounting Officer
Alnylam Pharmaceuticals, Inc.
675 West Kendall Street
Henri A. Termeer Square
Cambridge, MA 02142

       Re: Alnylam Pharmaceuticals, Inc.
           Form 10-K for the fiscal year ended December 31, 2024
           Filed February 13, 2025
           File No. 001-36407
Dear Gisele Dion:

       We have limited our review of your filing to the financial statements
and related
disclosures and have the following comment.

       Please respond to this letter within ten business days by providing the
requested
information or advise us as soon as possible when you will respond. If you do
not believe a
comment applies to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to this letter, we may have additional
comments.

Form 10-K for the fiscal year ended December 31, 2024
Notes to Consolidated Financial Statements
4. Net Revenues from Collaborations
Regeneron Pharmaceuticals, Inc., page 105

1.     Please link revenue recognized under the Regeneron collaboration and
associated
       deferred revenue on page 108 to corresponding amounts reported in the
financial
       statements for each period presented. Revise your disclosure
accordingly. In addition,
       provide the following information related to your accounting treatment
for the June
       2024 Amendment.
           Explain why the transaction price allocated to the new C5
Monotherapy
           Obligation was recognized at a point in time, while the transaction
price allocated
           to the legacy C5 License Obligation is recognized over time, given
your apparent
           continuing obligations to support these two licenses.
           Describe and quantify key assumptions underlying your determination
of
 May 9, 2025
Page 2

           standalone selling price of $322,000 for the C5 Monotherapy
Obligation,
           including discount rates, forecasted earnings, duration of the
commercial
           period and adjustments for probability of success.
             Explain how you determined revenue recognized in 2024 for the
Research
           Services Obligation and C5 License Obligation, particularly expected
           performance periods, and why no revenue was recognized for the
Regeneron
           Technology Transfer Obligation.
             Demonstrate that the cumulative catch up adjustment for the
remaining Research
           Services Obligation and C5 License Obligation was not significant.

        In closing, we remind you that the company and its management are
responsible for
the accuracy and adequacy of their disclosures, notwithstanding any review,
comments,
action or absence of action by the staff.

       Please contact Frank Wyman at 202-551-3660 or Daniel Gordon at
202-551-3486
with any questions.



                                                          Sincerely,

                                                          Division of
Corporation Finance
                                                          Office of Life
Sciences