Exhibit 10.5

SECOND AMENDMENT
TO
ALNYLAM PHARMACEUTICALS, INC.
2018 STOCK INCENTIVE PLAN
A. The Alnylam Pharmaceuticals, Inc. 2018 Stock Incentive Plan (the “Plan”) is
hereby amended by the Board of Directors of Alnylam Pharmaceuticals, Inc. (the
“Company”), subject to approval of the Company’s stockholders, to, among other
things, increase the aggregate number of shares authorized for issuance under
the Plan by 7,000,000 shares of common stock, par value $0.01 per share, of the
Company, and to amend the director grant limits, as follows:
1. Section 4(a)(1) of the Plan is hereby amended and restated in its entirety as
follows:
“(1) Authorized Number of Shares. Subject to adjustment under Section 10, Awards
may be made under the Plan for up to the sum of (i) 13,790,000 shares of common
stock, $0.01 par value per share, of the Company (the “Common Stock”), (ii) the
number of shares that remain available for grants under the Company’s Second
Amended and Restated 2009 Stock Incentive Plan (the “2009 Plan”) immediately
prior to the Effective Date and (iii) shares of Common Stock underlying any
awards granted under the 2009 Plan that expire, or are terminated, surrendered
or canceled without having been fully exercised or are forfeited in whole or in
part after the Effective Date and become available for issuance under the Plan
in accordance with Section 4(a)(3). No more than 29,270,000 shares may be issued
in the form of Incentive Stock Options (as hereinafter defined). Shares issued
under the Plan may consist in whole or in part of authorized but unissued shares
or treasury shares.”
2. Section 4(a)(2) of the Plan is hereby amended by deleting “and 4(b)(1)” in
each place where it appears.
3. Section 4(a)(3) of the Plan is hereby amended by deleting the phrase “and
under the sub limits contained in Section 4(b)(1)”.
4. Section 4(b) of the Plan is hereby amended and restated in its entirety as
follows:

“(b) Limits on Awards to Non-Employee Directors. The maximum value of all
compensation, including Awards hereunder, granted or paid to an individual in
connection with such individual’s initial appointment or election as a
Non-employee Director shall be $1,500,000. The maximum value of all
compensation, including Awards hereunder, granted or paid to a Non-employee
Director in any calendar year in connection with such individual’s service on
the Board (excluding for this purpose the value of any compensation, including
Awards hereunder, granted under the preceding sentence) shall be $1,000,000. For
the purpose of these limitations, the value of any Award shall be its grant date
fair value, as determined in accordance with ASC 718 or successor provision but
excluding the impact of estimated forfeitures related to service-based vesting
provisions.”

5. Section 6(a) of the Plan is hereby amended and restated in its entirety as
follows:
“(a) Board Discretion. The Board retains the specific authority to, from time to
time, determine the number of shares subject to Options granted to Non-employee
Directors under this Section 6, subject to the limitations contained in Section
4(b). All Options granted to Non-employee Directors shall be Nonstatutory Stock
Options. The Board also retains the specific authority to
ACTIVE/104190476.1

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issue SARs, Restricted Stock Awards or Other Stock-Based Awards in lieu of
Options, subject to the limitations contained in Section 4(b).”
6. Section 10(a) of the Plan is hereby amended by deleting “and 4(b)”.
B. Except as amended herein, the Plan is confirmed in all other respects.
Approved by the Board of Directors on March 1, 2020.