Exhibit 10.19

FOURTH AMENDMENT TO LEASE

This Fourth Amendment to Lease (this “Fourth Amendment”), made as of the 4th day
of November, 2011, by and between ARE-MA REGION NO. 28, LLC, a Delaware limited
liability company (“Landlord”) and ALNYLAM PHARMACEUTICALS, INC., a Delaware
corporation (“Tenant”).

W I T N E S S E T H:

WHEREAS, Landlord and Tenant are parties to a Lease dated as of September 26,
2003 (the “Original Lease”), as amended by a First Amendment to Lease dated
March 16, 2006 between Landlord (as successor to Three Hundred Third Street
LLC), and Tenant (as successor to Alnylam U.S., Inc., a Delaware corporation
that is a subsidiary of Tenant and was formerly known as Alnylam
Pharmaceuticals, Inc. (the “Original Tenant”), pursuant to an Assignment of
Lease dated February 28, 2006 between Original Tenant and Tenant), by a Second
Amendment to Lease between Landlord and Tenant dated June 26, 2009 and by a
Third Amendment to Lease between Landlord and Tenant (“Third Amendment”) dated
May 11, 2010 (as so amended, the “Lease”); and

WHEREAS, pursuant to the Lease, Landlord leases to Tenant certain premises
within the building known and numbered as 300 Third Street, Cambridge,
Massachusetts (the “Building”), which premises include but are not limited to
space on the first, second, third and fourth floors of the Building and are more
particularly described in the Lease; and

WHEREAS, pursuant to that certain Sublease between Tenant and sanofi-aventis
U.S. Inc., a Delaware corporation (“Sanofi”) dated August 3, 2010, as amended by
a First Amendment to Sublease (the “Sanofi First Amendment”) dated November 4,
2011 (as such Sublease is so amended, the “Sanofi Sublease”), with respect to
which Landlord, Tenant and Sanofi have executed that certain Consent to Sublease
dated August 3, 2010 and Consent to First Amendment to Sublease dated
November 4, 2011 (the “Consent to Sanofi First Amendment”), respectively, Tenant
currently subleases to Sanofi certain space on Level 01, the acid neutralization
room on Level P-2 and the chemical storage room on Level P-1, all as more
particularly described in the Sanofi Sublease (collectively, the “Subleased
Premises”); and

WHEREAS, Landlord and Tenant desire to amend the Lease with respect to Excess
Income (as defined in the Lease) so that the provisions set forth in Section 5
of the Third Amendment will no longer apply and the terms and conditions of the
Original Lease pertaining to Excess Income will apply to all assignment and
subletting, including without limitation, to the Excess Income from the Sanofi
Sublease, as set forth in this Fourth Amendment; and

WHEREAS, Landlord and Tenant have agreed to amend the Lease to, among other
things, change the allocation of Excess Income with respect to assignment and
subletting, including without limitation the Sanofi Sublease, all as more
particularly provided below.

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NOW, THEREFORE, in consideration of the foregoing and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto hereby covenant and agree as follows:

1. Defined Terms. All capitalized terms used and not otherwise defined herein
shall have the respective meanings ascribed to them in the Lease. In the event
of any inconsistency between the Lease and this Fourth Amendment, the provisions
of this Fourth Amendment shall control, and all other provisions of the Lease
shall remain in full force and effect.

2. Excess Income. The Lease is hereby amended so that, from and after January 1,
2012, the second grammatical paragraph of Section 5 of the Third Amendment
(which begins with the words “Tenant and Landlord agree that 100% …”) shall no
longer apply to Excess Income, and the terms and conditions of the Original
Lease pertaining to Excess Income, including without limitation the terms and
conditions of Section 16(D) of the Original Lease, shall apply to all assignment
and subletting, including without limitation the Excess Income from the Sanofi
Sublease.

(a) Tenant is receiving from Sanofi, as partial consideration for the execution
and delivery of the Sanofi First Amendment, a one-time payment of One Million
Five Hundred Thousand Dollars ($1,500,000) (the “One-Time Payment”).
Notwithstanding anything to the contrary contained in the Third Amendment or
this Fourth Amendment, upon receipt by Tenant of such One-Time Payment, Tenant
shall promptly pay Landlord in immediately available funds the amount of Six
Hundred Thousand Dollars ($600,000) as Additional Rent under the Lease.

(b) The provisions of Section 5 of the Third Amendment and Section 16(D) of the
Original Lease shall govern for their respective applicable time periods with
respect to Excess Income from rent and other sums payable by Sanofi pursuant to
the Sanofi Sublease, except as follows:

(i) The One-Time Payment shall not be included in the calculation of Excess
Income, and payment to Landlord of the portion of the One-Time Payment described
in Section 2(a) above shall be in lieu of payment of any Excess Income with
respect to the One-Time Payment; and

(ii) If Sanofi terminates the Sublease early in accordance with Section 4(b) of
the Sanofi First Amendment such that the effective date of such termination is
December 31, 2013, then Landlord and Tenant agree that, with respect to the
payment by Sanofi to Tenant of
One-Million-One-Hundred-Twenty-Thousand-Seven-Hundred-Sixty-One Dollars and
Thirty Cents ($1,120,761.30) (the “Termination Fee”), the Excess Income under
Section 16(D) of the Lease will continue to be calculated and paid by Tenant for
each of the months of January through June 2014 as if the portion of the
Termination Fee equal to six months of Base Rent for each of such months (i.e.,
One-Hundred-Fifty-Eight-Thousand-Seven-Hundred-Thirty-Two-Dollars ($158,732) per
month) were Base Rent paid by Sanofi under the Sanofi First Amendment for the
months

 

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of January through June 2014, notwithstanding such early termination by Sanofi
(to the extent that the Termination Fee includes the repayment of unamortized
brokerage fees and other transaction costs, such repaid brokerage fees and
transaction costs shall not be included as Tenant’s Transfer Expenses under
Section 16(D) of the Lease); and

(iii) If, and only if, following such termination in accordance with
Section 4(b) of the First Amendment to Sublease, the Subleased Premises under
the Sanofi Sublease (the “Vacant Space”) is vacant or not used or occupied by
Tenant or any party exercising rights by, through or under Tenant for any month
or part of a month after June 30, 2014, then in the calculation of Excess Income
with respect to a future sublease of the Vacant Space, the portion of Base Rent
paid by Tenant under the Lease with respect to the Vacant Space for each month
in the period of such vacancy or nonuse (each, a “Vacancy Month”) will be deemed
to be added and applied to the amount of Tenant’s Transfer Expenses in clause
(b) in the calculation of Excess Income for each month of the term of such
future sublease as set forth in Section 16(D) of the Lease until each such
Vacancy Month has been so applied, or if earlier, until the expiration or
earlier termination of such future sublease. No early termination rights granted
by Tenant to Sanofi in the Sanofi Sublease or the exercise thereof by Sanofi
shall affect the Term of the Lease or Tenant’s monthly rental obligations
pursuant to the Lease.

3. Ratification of Lease; Effect of Fourth Amendment. The Lease, as amended by
this Fourth Amendment, is hereby ratified and confirmed, and each and every
provision, covenant, condition, obligation, right and power contained in and
under, or existing in connection with, the Lease, as amended by this Fourth
Amendment, shall continue in full force and effect from and after the date
hereof and throughout the Term. This Fourth Amendment is not intended to, and
shall not be construed to, effect a novation, and, except as expressly provided
in this Fourth Amendment, the Lease has not been modified, amended, canceled,
terminated, surrendered, superseded or otherwise rendered of no force and
effect. Tenant acknowledges and agrees that the Lease, as amended by this Fourth
Amendment, is enforceable against Tenant in accordance with its terms. The Lease
and this Fourth Amendment shall be construed together as a single instrument.
This Fourth Amendment is the entire agreement between the parties with respect
to the subject matter hereof and supersedes all prior and contemporaneous oral
and written agreements and discussions. This Fourth Amendment may be amended
only by an agreement in writing signed by the parties hereto.

4. No Defaults, Counterclaims or Rights of Offset; Release of Landlord. Tenant
hereby warrants and represents that, to its knowledge, as of the date of the
execution of this Fourth Amendment by Tenant, there are no defaults under the
Lease in respect of Landlord’s performance thereunder and there exist no
defenses, counterclaims or rights of offset with respect thereto. Tenant, for
itself, its officers, directors, members, shareholders and their respective
legal representatives, successors and assigns, does hereby absolutely and
irrevocably waive, remise, release and forever discharge Landlord,

 

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its successors, assigns, partners, employees, affiliates, attorneys and agents,
of and from any and all manner of action and actions, cause and causes of
actions, suits, debts, dues, sums of money, accounts, reckoning, bonds, bills,
specialties, covenants, contracts, controversies, agreements, promises,
variances, trespasses, damages, judgments, extents, executions, claims and
demands whatsoever, in law or in equity, for items or matters that Tenant could
have been aware of or known about, through and including the date of execution
and delivery of this Fourth Amendment in connection with or relating to the
Lease or the transactions contemplated hereby. Nothing contained in this
paragraph shall be construed to release Tenant from its obligations under the
Lease throughout the Term of the Lease (including the Extended Term, if any).

5. Brokers. Landlord and Tenant represent and warrant to each other that neither
has dealt with any broker, finder or agent in procuring this Fourth Amendment
except for Richards Barry Joyce & Partners (the “Broker”). Tenant and Landlord
represent and warrant to each other that, except with respect to the Broker, who
represented Tenant, no broker, agent, commission salesperson, or other person
has represented it in the negotiations for and procurement of this Fourth
Amendment and that with respect to this Fourth Amendment no commissions, fees,
or compensation of any kind are due and payable in connection herewith to any
broker, agent, commission salesperson, or other person. Tenant and Landlord
agree to indemnify and hold harmless each other, its agents, members, partners,
representatives, officers, affiliates, shareholders, employees, successors and
assigns from and against any and all loss, liabilities, claims, suits, or
judgments (including, without limitation, reasonable attorneys’ fees and court
costs incurred in connection with any such claims, suits, or judgments, or in
connection with the enforcement of this indemnity) for any fees, commissions, or
compensation of any kind which arise out of or are in any way connected with any
claimed agency relationship not referenced in this paragraph.

6. Successors and Assigns. This Fourth Amendment shall bind and inure to the
benefit of the parties hereto and their respective permitted successors and
assigns.

7. Counterparts. This Fourth Amendment may be executed in a number of identical
counterparts, each of which for all purposes shall be deemed to be an original,
and all of which shall collectively constitute but one agreement, fully binding
upon, and enforceable against the parties hereto.

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IN WITNESS WHEREOF, the parties hereto have executed this Fourth Amendment as of
the day and year first written above.

 

TENANT: ALNYLAM PHARMACEUTICALS, INC. By:  

/s/ Michael Mason

Name:  

     Michael Mason

Title:  

     VP of Finance

 

LANDLORD: ARE-MA REGION NO. 28, LLC, a Delaware limited liability company By:  
Alexandria Real Estate Equities, L.P.,  
a Delaware limited liability company, its member   By:   ARE-QRS Corp., a
Maryland corporation,     its general partner     By:  

/s/ Eric S. Johnson

    Name:  

     Eric S. Johnson

    Title:  

     Vice President

           Real Estate Legal Affairs

 

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