At a meeting of the Compensation Committee (the "Committee") of the Board of Directors (the "Board") of Alnylam Pharmaceuticals, Inc. (the "Company") held on February 8, 2013, the Committee approved the 2013 Annual Incentive Program (the "Plan").

Under the Plan, all regular employees, including the Company's executive officers (collectively, the "Plan Participants"), are eligible to receive an annual cash bonus (a "Bonus Award") based upon the achievement of corporate goals and individual objectives for 2013 that have been specified in writing. The corporate goals for 2013 were proposed by the Company's executive officers and approved by the Board. Bonus Awards for the Company's executive officers will be based entirely upon achievement of the corporate goals. Individual objectives for Plan Participants who are non-executive officers were approved by the Committee. Individual objectives for all other Plan Participants were approved by the employees' direct supervisor and the appropriate officer of the Company.

Under the Plan, each Plan Participant has an established target award , as set forth in the table below, representing a percentage of the Plan Participant's annual base salary for 2013 (a "Target Award").

2013 Annual Incentive Program Target Awards

                                                      Target Award
           Title/Level                             (% of Base  Salary)
           Chief Executive Officer                         60%
           President and Chief Operating Officer           50%
           Executive Vice President                        50%
           Senior Vice President                           40%
           Vice President                                  30%
           Senior Director/Director                        20%
           Associate Director                              15%
           All Other Regular Employees                    7.5%

Bonus Awards under the Plan, if any, will be determined by first establishing a bonus pool (the "Bonus Pool"). The Bonus Pool will be calculated by
(1) aggregating each Plan Participant's Target Award and then (2) multiplying that sum by a modifier established by the Committee that is based on the Company's performance as measured against the 2013 corporate goals (the "Corporate Performance Level"). The Corporate Performance Level for 2013 will range from 0% to 115%; provided, however, that the Corporate Performance Level can only exceed 100% upon the achievement of specified clinical development goals and further provided that, if the Corporate Performance Level for 2013 falls below a threshold of 50%, no Bonus Awards will be paid under the Plan.

The Bonus Pool will then be allocated by the Committee among the Plan Participants based upon a consideration of each Plan Participant's title/level and salary (as reflected by their Target Award percentage) and (i) with respect to Plan Participants who are executive officers, the Corporate Performance Level, as well as each executive officer's contributions to achievement of the 2013 corporate goals, and (ii) with respect to all other Plan Participants, their 2013 year-end performance ratings, which shall be determined by their performance against their individual objectives for 2013, overall job performance and support of the Company's core values. The Committee retains discretion under the Plan to adjust upward or downward any Bonus Award and/or the Bonus Pool as it deems appropriate.