Exhibit 10.36

FIFTH
AMENDMENT TO LEASE

THIS
FIFTH AMENDMENT TO LEASE (this "Fifth Amendment") is made as of the 18th day of December, 2007 (the "Fifth Amendment Date"), by and between THE REALTY
ASSOCIATES FUND VI, L.P., a Delaware limited partnership ("Landlord") and CUBIST PHARMACEUTICALS, INC., a Delaware corporation ("Tenant").

RECITALS:

WHEREAS,
by a lease (the "Original Lease") dated as of January, 2004, California State Teachers' Retirement System ("Calsters") leased to Tenant approximately 15,475 rentable square feet
of space, consisting of a portion of the second (Suite 2201-55) and fourth (Suite 4201-55) floors in the building known as 45-55 Hayden Avenue,
Lexington, Massachusetts (the "Building"); and

WHEREAS,
Landlord has succeeded to the interests of Calsters as landlord under the Lease; and

WHEREAS,
the Original Lease has been amended by a First Amendment to Lease between Landlord and Tenant, dated as of September 29, 2005 (the "First Amendment"), and by a Second
Amendment to Lease between Landlord and Tenant dated as of November 18, 2005 (the "Second Amendment"), and by a Third Amendment to Lease between Landlord and Tenant dated as of June 20,
2007 (the "Third Amendment"), and by a Fourth Amendment to Lease dated as of October 25, 2007, (the Original Lease, as so amended, being referred to as the "Lease"), pursuant to which the size
of the premises demised under the Original Lease was increased to 108,502 rentable square feet (the "Existing Premises"). The Existing Premises consist of Suites 2201-55,
2200-55, 3000-55, 4201-55, 4200-55 and 4600-45; and

WHEREAS,
by letter dated as of April 27, 2006, and pursuant to the Second Amendment, Tenant elected to include Suite 2200-55 (also known as the Comet Space) in
the Existing Premises for the remainder of the Lease Term; and

WHEREAS,
Landlord and Tenant now desire to further amend the Lease to, among other things, expand the size of the Existing Premises by adding thereto approximately 12,146 rentable square
feet of space in Suite 1000-55 on the first floor of the Building (the "First Floor Space"), and to adjust the rent and certain provisions, all on the terms and conditions set forth
below.

NOW,
THEREFORE, in consideration of the mutual covenants herein contained, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged,
and intending to be legally bound hereby, Landlord and Tenant hereby agree as follows:



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PREMISES:

The following areas in the 55 Hayden Avenue portion of the Building: (i) Suite 2201-55 on the second floor and Suite 4201-55 on the fourth floor, (ii) Suite 4200-55 on the fourth floor of the
Building, (iii) Suite 2200-55 on the second floor of the Building, and (iv) Suite 3000-55 on the third floor of the Building; and (v) Suite 4600-45 on the fourth floor of the 45 Hayden Avenue portion of the Building; and
(vi) Suite 1000-55 on the first floor of the 55 Hayden Avenue portion of the Building. All such spaces are shown onExhibit A-5,attached hereto and incorporated herein.RENTABLE FLOOR AREA OF THE PREMISES:

Approximately 120,648 square feet of the 55 Hayden Avenue portion of the Building as follows (i) 6,755 rentable square feet on the second floor contained in Suite 2201-55, (ii) 8,720 rentable square feet on the fourth floor contained
in Suite 4201-55 and 31,453 rentable square feet on the fourth floor of the Building contained in Suite 4200-55, (iii) 6,150 rentable square feet on the second floor of the Building contained in Suite 2200-55, (iv) 30,019
rentable square feet on the third floor of the Building contained in Suite 3000-55; (v) 25,405 rentable square feet on the fourth floor of the 45 Hayden Avenue portion of the Building contained in Suite 4600-45, and (vi) 12,146
rentable square feet on the first floor of the Building contained in Suite 1000-55;.




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IN
WITNESS WHEREOF, the undersigned have hereunto set their hands and seals as of the date first above written.

| | LANDLORD:                                                          
| | -------------------------------------------------------------------
| | The Realty Associates Fund VI, L.P.,
a Delaware limited partnership
| | By:                                                                
| |                                                                    
| |                                                                    
| |                                                                    
| | By:                                                                
| | By:                                                                
| | TENANT:                                                            
| | CUBIST PHARMACEUTICALS, INC.                                       
| | By:                                                                
| |                                                                    

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Exhibit A-5

Plans
of Premises

[Floor
Plans]

|SECOND FLOOR
45-55 HAYDEN AVENUE
LEXINGTON, MA |  | CUBIST SUITE 2200
6,150 RSF
|---------------------------------------------- |  | ---------------------------

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[Floor
Plans]

|SECOND FLOOR
45-55 HAYDEN AVENUE
LEXINGTON, MA |  | CUBIST SUITE 2201
6,755 RSF
|---------------------------------------------- |  | ---------------------------

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[Floor
Plans]

|THIRD FLOOR
45-55 HAYDEN AVENUE
LEXINGTON, MA |  | MOTOROLA SUITE 3000
30,019 RSF
|--------------------------------------------- |  | ------------------------------

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[Floor
Plans]

|FOURTH FLOOR
45-55 HAYDEN AVENUE
LEXINGTON, MA |  | CUBIST SUITE 4200
31,453 RSF
|---------------------------------------------- |  | ----------------------------

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[Floor
Plans]

|FOURTH FLOOR
45-55 HAYDEN AVENUE
LEXINGTON, MA |  | CUBIST SUITE 4201
8,720 RSF
|---------------------------------------------- |  | ---------------------------

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[Floor
Plans]

|FOURTH FLOOR
45 HAYDEN AVENUE
LEXINGTON, MA |  |           
|------------------------------------------- |  | ----------
|CUBIST SUITE 4600-45                        |  | 25,405 RSF

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[Floor
Plans]

|CUBIST SUITE 1000-55 |  | 12,146 RSF
|-------------------- |  | ----------

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SCHEDULE I TO FIFTH AMENDMENT

Annual
Rent

Annual
Rent for the Premises shall be the sum of the rents shown below for each portion of the Premises, determined as of the date in question.

As to Suites 2201-55, 4201-55 and 4200-55:

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SF5/1/061/31/07

$
371,400.00

$
30,950.00

$
24.002/1/071/31/08

$
386,875.00

$
32,238.58

$
25.002/1/087/31/09

$
402,350.00

$
33,529.17

$
26.00


plus
(ii) as to Suite 4200-55:

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SF7/1/064/30/07

$
723,419.00

$
60,284.92

$
23.005/1/074/30/08

$
739,145.50

$
61,595.46

$
23.505/1/084/30/09

$
754,872.00

$
62,906.00

$
24.005/1/097/31/09

$
794,188.25

$
66,182.35

$
25.25


RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SF8/1/094/30/10

$
1,184,932.00

$
98,744.33

$
25.255/1/104/30/11

$
1,208,396.00

$
100,699.67

$
25.755/1/114/30/12

$
1,231,860.00

$
102,655.00

$
26.255/1/124/30/13

$
1,267,056.00

$
105,588.00

$
27.005/1/134/30/14

$
1,325,716.00

$
110,476.33

$
28.255/1/144/30/15

$
1,384,376.00

$
115,364.67

$
29.505/1/154/30/16

$
1,419,572.00

$
118,297.67

$
30.25


As to Suite 2200-55:

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SF6/1/064/30/07

$
140,415.00

$
11,787.50

$
23.005/1/074/30/08

$
144,525.00

$
12,043.75

$
23.505/1/084/30/09

$
147,600.00

$
12,300.00

$
24.005/1/094/30/10

$
155,287.50

$
12,940.63

$
25.255/1/104/30/11

$
158,362.50

$
13,196.88

$
25.755/1/114/30/12

$
161,437.50

$
13,453.13

$
26.255/1/124/30/13

$
166,050.00

$
13,837.50

$
27.005/1/134/30/14

$
173,737.50

$
14,478.13

$
28.255/1/144/30/15

$
181,425.00

$
15,118.75

$
29.505/1/154/30/16

$
186,037.50

$
15,503.13

$
30.25


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As to Suite 3000-55:

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SFThrough 4/30/08

$
780,494.00

$
65,041.17

$
26.005/1/084/30/09

$
810,513.00

$
67,542.75

$
27.005/1/094/30/10

$
825,522.50

$
68,793.54

$
27.505/1/104/30/11

$
840,532.00

$
70,044.33

$
28.005/1/114/30/12

$
900,570.00

$
75,047.50

$
30.005/1/124/30/13

$
945,598.50

$
78,799.88

$
31.505/1/134/30/14

$
975,617.50

$
81,301.46

$
32.505/1/144/30/15

$
1,035,655.50

$
83,304.63

$
34.505/1/154/30/16

$
1,065,674.50

$
88,806.21

$
35.50


As to Suite 4600-45

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SFThrough 4/30/09

$
819,311.25

$
68,275.94

$
32.255/1/094/30/10

$
844,716.25

$
70,393.02

$
33.255/1/104/30/11

$
870,121.25

$
72,510.10

$
34.255/1/114/30/12

$
895,526.25

$
74,627.19

$
35.255/1/124/30/13

$
920,931.25

$
76,744.27

$
36.255/1/134/30/14

$
946,336.25

$
78,861.35

$
37.255/1/144/30/15

$
971,741.25

$
80,978.44

$
38.255/1/154/30/16

$
997,146.25

$
83,095.52

$
39.25


As to Suite 1000-55

RENTAL PERIOD

TOTAL ANNUAL RENT

MONTHLY PAYMENT

RENTAL RATE/SFThrough 4/30/08

$
266,024.16

$
22,168.68


N/A5/1/084/30/09

$
346,161.00

$
28,846.75

$
28.505/1/094/30/10

$
352,234.00

$
29,352.83

$
29.005/1/104/30/11

$
358,307.00

$
29,858.92

$
29.505/1/114/30/12

$
364,380.00

$
30,365.00

$
30.005/1/124/30/13

$
370,453.00

$
30,871.08

$
30.505/1/134/30/14

$
376,526.00

$
31,377.17

$
31.005/1/144/30/15

$
382,599.00

$
31,883.25

$
31.505/1/154/30/16

$
388,672.00

$
32,389.33

$
32.00


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SCHEDULE
2

RIGHTS
OF EXISTING BUILDING TENANTS

|                                          |  |                                                                                                                                                                                                                       
|----------------------------------------- |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Celerant                                  |  | Option to Extend                                                                                                                                                                                                      
|8,017 sf2nd Fl (45)
Expiration 8/31/12   |  | One 5 year term (thru August 31, 2017); Notice of exercise must be prior to 11/30/2011.                                                                                                                               
|NitroMed                                  |  | Option to Extend                                                                                                                                                                                                      
|19,815 sf3rd Fl (45)
Expiration 9/30/12  |  | One 5 year term (thru September 30, 2017); Notice prior to September 30, 2011 required                                                                                                                                
|Goodrich, LLC                             |  | Option to Extend                                                                                                                                                                                                      
|10,495 sf3rd Fl (55)
Expiration 11/30/09 |  | One 7 year term (thru November 30, 2016); 12 mos. notice prior to expiration of current term required                                                                                                                 
|Aon Consulting                            |  | Option to Extend                                                                                                                                                                                                      
|5,528 sf2nd Fl (45)
Expiration 7/31/2011 |  | One 5 year term (thru July 31, 2016); 12 mos. notice prior to expiration of current term required                                                                                                                     
|Spaulding and Slye                        |  | Option to Extend                                                                                                                                                                                                      
|14,092 sf2nd Fl (55)
Expiration 3/31/15  |  | Two extension of 5 year terms (thru March 31, 2020 and March 31, 2025, respectively); each on 9 mos. notice prior to expiration of current term required                                                              
|Spaulding and Slye                        |  | First Right to Lease                                                                                                                                                                                                  
|                                          |  | During the term of Spaulding and Slye's lease to the 14,092 sf on the 2nd floor of the 55 Hayden Avenue portion of the Building, Spaulding and Slye holds a first right to lease the following spaces in the
Building:
|                                          |  |  8,017 sf2nd Fl (45) (Celerant space)                                                                                                                                                                               
|                                          |  |  5,528 sf2nd Fl (45) (Aon Consulting space)                                                                                                                                                                         
|                                          |  |  3,089 sf2nd Fl (45) (FCG spaceexpires 1/31/09)                                                                                                                                                                    
|                                          |  | Spaulding and Slye must respond to the Landlord's notice of any such space becoming available within 14 days of such notice.                                                                                          

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