Document:

EX-10.1

EXHIBIT 10.1

3.28.07

SUBLEASE

THIS SUBLEASE AGREEMENT (“Sublease”) is made as of the 2nd day of April, 2007, by and
between Millennium Pharmaceuticals, Inc., a Delaware corporation (“Sublandlord”), and Altus
Pharmaceuticals, Inc., a Delaware corporation (“Subtenant”).

RECITALS:

A. Pursuant to a Lease dated as of August 26, 1993, as amended by a First Amendment to Lease
dated as of May 18, 1994; by a Second Amendment to Lease dated as of January 9, 1996; by a Third
Amendment to Lease dated as of June 12, 1996; by a Fourth Amendment to Lease dated as of March 1,
1997; by a Fifth Amendment to Lease dated as of June 19,1997; by a Sixth Amendment to Lease dated
as of January 29, 1999; by a Seventh Amendment to Lease dated as of February 5, 1999; by an Eighth
Amendment to Lease dated as of February 7, 2000; and by a Lease Extension Agreement dated December
1, 2000 (the “Extension Agreement”) (hereinafter collectively, as amended and extended, the
“Prime Lease”), Sublandlord, as tenant, leased from Massachusetts Institute of Technology,
as landlord (hereinafter called “Prime Landlord”), certain premises consisting of
approximately 181,022 rentable square feet (approximately 159,995 rentable square feet on the
first, second, third and fifth floors of the Building and approximately 21,027 rentable square feet
in the basement of the Building), together with all rights appurtenant thereto (hereinafter, the
“Leased Premises”), in the Building located at 640 Memorial Drive, Cambridge, Middlesex
County, Massachusetts (the “Building”), all as more particularly described in the Prime Lease and
the amendments thereto.

B. Sublandlord and Subtenant have agreed that Sublandlord will sublet to Subtenant
approximately 72,935 rentable square feet of space, comprising the entire second (2nd) and third
(3rd) floors of the Building as shown on Exhibit A attached hereto (hereinafter collectively, the
“Subleased Premises”).

C. Sublandlord and Subtenant hereby execute and deliver this Sublease subject to the condition
precedent of Sublandlord’s obtaining the Prime Landlord’s written consent hereto.

D. Capitalized terms used herein and not otherwise defined herein shall have the same meanings
as defined in the Prime Lease.

AGREEMENTS:

For good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged and for the mutual covenants contained herein, the parties agree as follows:

1. Term. Sublandlord hereby leases to Subtenant, and Subtenant hereby leases from
Sublandlord, the Subleased Premises, for a “Term” commencing upon the later of (i) delivery
of the Premises with Sublandlord’s Work, as hereinafter defined, substantially complete, as
certified by Sublandlord; and (ii) the date this Sublease has been fully executed by Sublandlord
and Subtenant and the Prime Landlord has consented to this Sublease (the “Commencement
Date”), and expiring on March 31, 2008 (the “Initial Expiration Date”).

2. Tenancy at Will. Following the Initial Expiration Date, this Sublease shall remain in
full force and effect, but shall be converted into a tenancy-at-will on a month-to-month basis for
the period (the “At-Will Period”) commencing on April 1, 2008 and expiring on December 31,
2008 (the “Prime Expiration Date”). During the At-Will Period, this Sublease may be
terminated by either Subtenant or Sublandlord upon sixty (60) days’ prior written notice to the
other party hereto; provided, however, that Sublandlord may terminate this Sublease during the
At-Will Period only in the event that Sublandlord and Prime Landlord agree, at Prime Landlord’s
request, to an early termination of the Prime Lease. Such notice may be given prior to April 1,
2008, and the tenancy-at-will may be thereby terminated within the first sixty (60) days
thereafter, but in no event prior to March 31, 2008. On the Prime Expiration Date, such
tenancy-at-will shall automatically terminate without any requirement of notice from either party.
Any period during which such tenancy-at-will exists shall be governed by the terms of this
Sublease. The “Expiration Date” shall be the later of (i) April 1, 2008 or (ii) such later
date before the Prime Expiration Date on which the At-Will Period is terminated as provided in this
Section 2.

3. Condition of the Subleased Premises. The Subleased Premises are leased to Subtenant in
their “as is” condition as of the date hereof, subject to the work to be performed by Sublandlord,
as set forth in Exhibit B attached hereto (“Sublandlord’s Work”). Sublandlord makes no
representations, warranties or promises, except as otherwise provided in Exhibit B, Section 30 and
this Section 3, with respect to the Subleased Premises, the condition of any equipment therein or
the suitability of the Sublease Premises for the uses contemplated by this Sublease. Subtenant
agrees to accept possession of the Subleased Premises on the Commencement Date “as is,” in their
same condition on the date hereof, subject to the performance by Sublandlord of Sublandlord’s
Work. 

4. Fixtures; Laboratory Equipment; Furniture. To the extent that there are any fixtures or
equipment attached to the Subleased Premises, the same may be used by Subtenant during the Term of
this Sublease, and shall remain with the Subleased Premises at the end of the Term. To the extent
that any personal property is in the Subleased Premises as of the date of this Sublease, Subtenant
accepts possession of all such personal property, without warranty or representation as to the
condition thereof, or its fitness for any particular purpose, and such personal property shall be
deemed transferred to Subtenant as of the Commencement Date, and Subtenant shall remove the same
from the Subleased Premises by the Expiration Date or earlier date of termination of this Sublease.
Subtenant shall insure such personal property for its full replacement value during the Term.

5. Subtenant’s Work. Subject to Sublandlord’s prior written consent and approval, which
shall not be unreasonably withheld, conditioned or delayed, and Prime Landlord’s prior written
consent and approval in accordance with the Prime Lease, Subtenant shall have the right to
construct, at Subtenant’s sole cost and expense, alterations to the Subleased Premises to
accommodate Subtenant’s occupancy thereof. All alterations shall be performed in accordance with
the terms of the Prime Lease. Subtenant shall be solely responsible for removing any alterations
installed by Subtenant upon the expiration or termination of this Sublease, to the extent that such
removal is required by the Prime Lease. Sublandlord shall permit such reasonable access to the
Subleased Premises after the execution of this Sublease and before the Commencement Date as
Subtenant may require to construct permitted alterations in the Subleased Premises, provided that
the same do not interfere with the performance of Sublandlord’s Work.

6. Rent. The annual base rent per year, drawn on a U.S. bank, payable in advance in equal
monthly installments, commencing on the Commencement Date, and thereafter on the first day of each
calendar month of the Term in advance, prorated for any partial month at the beginning or end of
the Term, shall be One Million Four Hundred Fifty-Eight Thousand Seven Hundred Dollars
($1,458,700.00) annually, or One Hundred Twenty-One Thousand Five Hundred Fifty-Eight and 33/100
Dollars ($121,558.33) monthly. The Rent is intended to be gross rent and includes, without
limitation, the following: (i) all charges for utilities furnished to the Subleased Premises,
except as set forth in Section 7 below; and (ii) all Additional Rent due under the Prime Lease with
respect to the Subleased Premises including, without limitation, Taxes and Operating Expenses
(except any Additional Rent occasioned by the default of Subtenant hereunder).

Rent and all other charges due hereunder shall be payable without set-off, offset, deduction or
counterclaim at Sublandlord’s address set forth below or at such other place as may be set forth by
notice from Sublandlord to Subtenant. Any installment of rent due or accruing hereunder and any
other sum, whether termed rent or otherwise, and payable hereunder by Subtenant to Sublandlord, not
paid within five (5) business days after written notice that such payment is overdue, shall bear
interest from the due date at a rate equal to the prime rate published by the Wall Street
Journal from time to time plus three percent (3%).

7. Services. The Subleased Premises shall have available hot water, cold water, tempered
water, compressed air, standby power and ventilation, and the removal of lab waste from the
Subleased Premises. From and after the Commencement Date, Subtenant shall be solely responsible
for their operation, including all utility costs associated therewith and governmental permits
required therefor. Subtenant agrees to perform the obligations set forth on Exhibit B with respect
to the equipment servicing the Subleased Premises, as described therein.

8. Security System. The Subleased Premises currently contains security card readers and
security panels dedicated to the Subleased Premises, which equipment Sublandlord shall leave in
place and permit Subtenant to use during the Term, provided Subtenant shall contract directly for
any services necessary to operate such facilities. Subtenant shall provide, at its sole cost and
expense, any additional security equipment or services that it requires, subject to Sections 4 and
5 of this Sublease and the terms of the Prime Lease.

9. Lab Systems. Subtenant shall have the right during the Term to use the Reverse Osmosis
System (“RO System”) and pH neutralization system located at the Building (the “pH System,” and
collectively, the “Lab Systems”), as set forth in Exhibit B hereto. Subtenant shall be
responsible during the Term, at Subtenant’s sole expense, for all maintenance and repairs to the
Lab Systems, except as provided herein. Subtenant shall promptly apply for, obtain and maintain in
good standing all governmental permits and approvals required for the operation of the Lab Systems,
at Subtenant’s sole expense, except as provided herein.

In the event that Sublandlord occupies any space in the Building during the Term, Sublandlord
and Subtenant shall each have a non-exclusive right to use the Lab Systems during such occupancy
(the “Shared Use Period”), and each party shall permit such reasonable access by the other party as
is necessary for the reasonable use, maintenance and repair of the Lab Systems, provided Subtenant
shall comply with Sublandlord’s reasonable rules and regulations regarding the use and operation of
the Lab Systems. During the Shared Use Period, Sublandlord shall be responsible, at its sole cost
and expense, for all maintenance and repairs to the Lab Systems, and Subtenant shall pay to
Sublandlord as Additional Rent Subtenant’s proportionate share of the costs of maintenance and
repair to the Lab Systems, which proportionate share shall be fifty percent (50%). During the
Shared Use Period, Sublandlord shall apply for and obtain governmental permits and approvals for
the operation of the pH System (“Permits”). In the event Sublandlord obtains such Permits,
Subtenant shall terminate and abandon any Permits that it has obtained relating to the pH System,
and Subtenant’s use of the pH System shall thereafter be subject to Permits obtained by
Sublandlord, and Subtenant shall not take any action that would violate the terms and provisions of
such Permits.

10. Maintenance and Repairs. Except as otherwise expressly provided herein, Subtenant
shall be responsible, commencing on the Commencement Date, for all maintenance and repairs to
equipment solely serving the Subleased Premises and located within the Subleased Premises.
Subtenant shall also be responsible during the Term, at Subtenant’s sole expense, for the
maintenance and repair of the generator located in the parking lot adjacent to the Subleased
Premises. Notwithstanding the foregoing, Subtenant shall be responsible for the Subtenant’s
Proportionate Share of all costs related to any shared building systems repaired by the Sublandlord
or Landlord, excluding any capital expenditures. “Subtenant’s Proportionate Share” shall
be a fraction, the numerator of which shall be the number of net rentable square feet within the
Subleased Premises, and the denominator of which shall be the number of net rentable square feet
within the Building.

11. Parking. Subtenant shall have the right to use during the Term one hundred eight (108)
parking spaces in the Building parking lot leased by Sublandlord from Prime Landlord pursuant to
Section 9 of the Extension Agreement. Prior to the Initial Expiration Date, Subtenant may use such
parking spaces at no additional cost. During the At-Will Period, Subtenant shall pay to
Sublandlord, as Additional Rent, Eighteen Thousand Three Hundred Sixty Dollars ($18,360.00) monthly
for the use of said parking spaces.

12. Personal Property Taxes. Subtenant agrees to pay to local tax authorities and other
governmental agencies throughout the term of this Sublease all personal property taxes which may be
levied against Subtenant’s merchandise, trade fixtures and other personal property in and about the
Subleased Premises.

13. Use. Subtenant shall use the Subleased Premises solely for the uses permitted under
the Prime Lease.

14. Prime Lease Terms and Conditions. Except as may be inconsistent with the other
provisions hereof, the terms and conditions of the Prime Lease as applicable to the Subleased
Premises, other than the payment of rent, are hereby incorporated by reference and made a part
hereof, meaning that, as applicable, references to “Lessee” or “Tenant” therein shall be deemed to
be “Subtenant” hereunder, references to “Lessor” or “Landlord” therein shall be deemed to be
“Sublandlord” hereunder, and such other terms shall be deemed modified as may be appropriate in the
given context, provided (i) Prime Landlord shall continue to have all rights set forth in the Prime
Lease (notwithstanding the fact that Sublandlord shall also have the same rights under this
Sublease), and (ii) Sublandlord shall not be deemed to have assumed any of the obligations of Prime
Landlord as a result of the incorporation of the Prime Lease. This Sublease and all of its terms,
covenants, representations, warranties, agreements and conditions are in all respects subject and
subordinate to the Prime Lease. Subtenant agrees that in no event shall Prime Landlord be (a)
liable for any act or omission of Sublandlord; (b) liable for the return of any security deposit
unless Prime Landlord is holding the same; (c) subject to any offsets or defenses which Subtenant
may have against Sublandlord; or (d) bound by any rent or additional rent which Subtenant may have
prepaid for more than the current month. Sublandlord shall use reasonable efforts to enforce the
obligations of the Prime Landlord under the Prime Lease, provided that Sublandlord shall not be
obligated to commence litigation to do so.

15. Subtenant Obligations Under Prime Lease. Subtenant agrees to perform, fulfill, and
observe all of the covenants, agreements, obligations, conditions, representations, warranties,
terms and provisions imposed upon Sublandlord as Tenant of the Subleased Premises under the Prime
Lease as applicable to the Subleased Premises arising from and after the Commencement Date, except
for rent allocable to the Subleased Premises, which shall be governed by this Sublease. Subtenant
agrees to indemnify and hold Sublandlord harmless from and against any and all claims, liabilities,
losses and damages of any kind whatsoever (including, without limitation, reasonable attorneys’
fees and expenses) which Sublandlord may incur by reason of Subtenant’s failure to perform, fulfill
or observe any of the covenants or agreements set forth herein or the applicable provisions set
forth in the Prime Lease. Notwithstanding the foregoing, Subtenant shall have no obligation to (i)
cure any default of Sublandlord under the Prime Lease, (ii) perform any obligation of Sublandlord
under the Prime Lease which arose prior to the Commencement Date and Sublandlord failed to perform,
(iii) repair any damage to the Subleased Premises caused by Sublandlord, (iv) remove any
alterations or additions installed within the Subleased Premises by Sublandlord, (v) indemnify
Sublandlord or Prime Landlord with respect to any negligence or willful misconduct of Sublandlord,
its agents, invitees, employees or contractors or other subtenants of the Building other than
Subtenant, (vi) discharge any liens on the Subleased Premises or the Building which arise out of
any work performed by or at the direction of Sublandlord or (vii) remediate any Hazardous Materials
in, on or about the Subleased Premises caused by any party other than Subtenant, its agents,
invitees, employees or contractors. Sublandlord agrees to indemnify and hold Subtenant harmless
from and against any and all claims, liabilities, losses and damages of any kind whatsoever
(including, without limitation, reasonable attorneys fees and expenses) which Subtenant may incur
by reason of Sublandlord’s failure to pay rent when due under the Prime Lease, or any other default
by Sublandlord under the Prime Lease, provided that Subtenant has timely paid to Sublandlord rent
when due hereunder. The indemnification obligations of each party shall survive the termination or
expiration of this Sublease.

16. Termination. This Sublease shall terminate upon the termination of the Prime Lease for
any reason whatsoever, without any liability therefor on the part of Sublandlord to Subtenant
(except as expressly set forth in Section 15 above), with the same force and effect as if the date
of such termination had been provided expressly in this Sublease as the Expiration Date.
Sublandlord covenants and agrees that prior to the Initial Expiration Date Sublandlord will not
voluntarily surrender or terminate the Prime Lease except in the event of a taking or casualty in
accordance with the Prime Lease, nor shall it agree to modify or amend the Prime Lease in any way
that will reduce the rights or increase the obligations of Subtenant under this Sublease in any
material respect.

17. Compliance with Law. Subtenant shall comply with all statutes, ordinances, rules,
orders, regulations or requirements relating to its specific use of the Subleased Premises,
including environmental regulations applicable to its particular manner of use of the Subleased
Premises, as opposed to the Permitted Uses under the Prime Lease, and in no event shall Sublessee
ever be responsible for making any capital expenditures hereunder, and Subtenant shall obtain and
comply with all government permits and approvals required in connection with Subtenant’s research
and other activities in the Subleased Premises. Notwithstanding anything to the contrary contained
herein, in no event shall Subtenant be liable for any existing violations of applicable law with
respect to the Subleased Premises existing on the Commencement Date of the Sublease. Subtenant
agrees to provide reasonable cooperation to Sublandlord and Prime Landlord to secure any necessary
permits or approvals related to the operation of the Building. Subtenant also agrees to provide
reasonable cooperation to Sublandlord and Prime Landlord in responding to any inquires from
regulatory authorities regarding the use or operation of the Building or Subtenant’s operations
therein.

18. Surrender. Prior to the Expiration Date or earlier termination of this Sublease,
Subtenant shall, at Subtenant’s sole cost and expense, (i) decommission all regulated equipment and
materials and (ii) deliver certifications reasonably satisfactory to Sublandlord that all
radioactive, biological and hazardous materials have been removed from the Subleased Premises.

19. Insurance. Prior to the Commencement Date, and at least twenty (20) days prior to the
expiration thereof during the Sublease Term, Subtenant shall provide to Sublandlord certificates
which evidence the insurance coverages required under the Prime Lease, which insurance shall name
both Prime Landlord and Sublandlord as additional insureds thereunder.

20. Holding Over. If Subtenant remains on the Subleased Premises after the Expiration Date
or after earlier termination of this Sublease, then such holding over shall not be deemed to extend
or renew the term of this Sublease or to create any tenancy at will (except as expressly provided
herein), but such holding over shall be as a tenancy-at-sufferance only subject to all the terms
and provisions of this Sublease; provided, however, Subtenant shall be liable for two hundred
percent (200%) of all rent and other charges related to occupancy of the Subleased Premises. In
addition, Subtenant shall indemnify and hold harmless Sublandlord from and against all liability,
damages, losses and claims (including, without limitation, reasonable attorneys’ fees and expenses)
incurred by Sublandlord in connection with the holding over of Subtenant including, without
limitation, any liability of Sublandlord to Prime Landlord. Notwithstanding the foregoing,
Sublandlord may, at its option, regain possession of the Subleased Premises or any part thereof by
any and all means available to Sublandlord under this Sublease, the Prime Lease, or at law. The
provisions of this Section 20 shall be superseded by any separate agreement between Prime Landlord
and Subtenant under which Subtenant retains occupancy of the Subleased Premises from and after the
Prime Expiration Date, provided that Sublandlord shall have no liability with respect to the
Subleased Premises from and after the Prime Expiration Date.

21. Brokerage Representations. Sublandlord and Subtenant each represents that it has not
dealt with any broker in connection with this Sublease except CB Richard Ellis and CRESA Partners,
LLC (the “Brokers”). Each party hereby agrees to defend, indemnify and hold harmless the other
party from and against any loss, cost or expense (including reasonable attorneys’ fees) incurred as
a result of its breach of the foregoing representation. Sublandlord shall pay the Brokers the
brokerage commission fee or other compensation due the Brokers in connection with this Sublease
under separate agreements between and among Sublandlord and Brokers and shall indemnify and hold
Subtenant harmless from and against any and all liability, claims, suits, demands, judgments,
costs, interest and expenses (including, without being limited to, reasonable attorneys’ fees and
expenses) which Subtenant may be subject to or suffer by reason of any claim made by the Brokers
for any commission, fee or other compensation as a result of the execution and delivery of this
Sublease.

22. Assignment and Subletting. Subtenant shall not assign or sublease this Sublease
without the prior written consent of Sublandlord, which consent may be withheld in Sublandlord’s
sole discretion, and the prior written consent of Prime Landlord, as provided in the Prime Lease.
Notwithstanding anything to the contrary contained herein, Sublandlord’s consent shall not be
required for a proposed assignment of this Sublease or subletting of the Subleased Premises to an
entity (1) that controls, is controlled by or is under common control with Subtenant, or (2)
provided that the net worth of the successor entity is no less than the net worth of Subtenant as
of the date of this Sublease, that (i) acquires all or substantially all of Subtenant’s assets,
stock or membership interests or (ii) that merges or consolidates with Subtenant.

23. Prime Landlord’s Consent Contingency. This Sublease is conditioned upon obtaining
Prime Landlord’s written consent to this Sublease, which Sublandlord agrees to use all reasonable
efforts to obtain.

24. Notices. Any notice required hereunder shall be deemed to have been given when
deposited with the U.S. Mail (certified mail, postage prepaid, return receipt requested), when
deposited with a recognized overnight courier, or when delivered in hand by a direct courier who
obtains a receipt for such delivery. Such notices shall be sent to the following addresses:

If to Sublandlord:

Millennium Pharmaceuticals, Inc.

40 Landsdowne Street

Cambridge, Massachusetts 02139

Attention: Mr. Kenneth Doyle, Senior Manager of Real Estate Facilities Planning

With a copy to:

Katharine E. Bachman, Esq.

Wilmer Cutler Pickering Hale and Dorr LLP

60 State Street

Boston, Massachusetts 02109

If to Subtenant:

Prior to occupancy:

Altus Pharmaceuticals, Inc.

125 Sidney Street

Cambridge, MA 02139-4807

Attention: Jonathan Lieber, Vice President and Chief Financial Officer and Bruce Leicher,
General Counsel

After occupancy:

Altus Pharmaceuticals, Inc.

640 Memorial Drive

Cambridge, MA 02139

Attention: Jonathan Lieber, Vice President and Chief Financial Officer and Bruce Leicher,
General Counsel

Any party may change its address for notice by notifying the other parties as aforesaid.

25. No Partnership. Sublandlord shall not be held to be a partner, joint venturer, or
associate of Subtenant in the conduct of its business, it being expressly understood and agreed
that the relationship between the parties hereto is and at all times shall remain that of
Sublandlord and Subtenant.

26. Entire Agreement. All prior understandings and agreements between the parties are
merged within this Sublease, which alone fully and completely sets forth the understanding of the
parties, and this Sublease may not be changed or terminated orally or in any manner other than by
an agreement in writing and signed by the party against whom enforcement of the change or
termination is sought.

27. Binding Effect. The covenants and agreements herein contained shall bind and inure to
the benefit of Sublandlord and Subtenant and their permitted successors and assigns.

28. Governing Law. The Sublease and all rights and remedies thereunder shall be governed
by the law of the Commonwealth of Massachusetts.

29. Limitation of Liability. No director, officer, shareholder, employee, adviser or agent
of Sublandlord or Subtenant shall be personally liable in any manner or to any extent under or in
connection with this Sublease. In no event shall Sublandlord, Subtenant or any of their
directors, officers, shareholders, employees, advisers or agents be responsible for any
consequential, indirect or special damages or interruption or loss of business, income or profits.

30. Sublandlord Representations. Sublandlord represents and warrants: (i) that it is the
holder of the interest of the “Tenant” under the Prime Lease and said interest is not the subject
of any lien, assignment, sublease, or other hypothecation or pledge, (ii) that the Prime Lease is
in full force and effect unmodified, except as set forth above, and constitutes the entire
agreement between the Prime Landlord and Sublandlord in respect of the Subleased Premises, (iii)
that no notices of default have been served on Sublandlord under the Prime Lease which have not
been cured, and (iv) to the best of Sublandlord’s knowledge, neither Sublandlord nor Prime Landlord
is in default under the Prime Lease. Sublandlord represents that, to the best of Sublandlord’s
knowledge, there are no Hazardous Materials within the Subleased Premises as of the date of this
Sublease.

[Remainder of page intentionally left blank]

1

IN WITNESS WHEREOF the parties hereto set their hands and seals as of the day and year first above
written.

	 	 	 
	SUBLANDLORD:

	 	

	 
	 	 
	MILLENNIUM PHARMACEUTICALS, INC.

	 
	 	 
	By: /s/ Marsha Fanucci

Name:

Title:

	 	

Marsha Fanucci

Senior Vice President and Chief Financial Officer

SUBTENANT:

	 	 	ALTUS PHARMACEUTICALS, INC.

	 	 	 
	By: /s/ Jonathan I. Lieber

	Name:

Title:

	 	Jonathan I. Lieber

Vice President, Chief Financial Officer and Treasurer
	 
	 	 

2

EXHIBIT A

SUBLEASED PREMISES

(Diagrams omitted)

3

EXHIBIT B

SUBLANDLORD’S WORK; SUBTENANT’S OBLIGATIONS

	1.	 	Sublandlord shall demise the first and second floors by putting up temporary partitions
around the interconnecting stairway.

	2.	 	All mechanical, electrical and plumbing systems shall be in good working order and adequate
to service the space as currently built.

	3.	 	All non-plug-in lab equipment shall remain in the space and shall be delivered for
Subtenant’s use “as-is.” Sublandlord makes no representation that the equipment in its
current condition is fully operational.

	4.	 	Compressed air and vacuum units currently located on the third floor shall be turned over as
fully functional units for Subtenant’s use. Subtenant shall be responsible during the Term,
at Subtenant’s sole expense, for all maintenance and repairs to such equipment. Subtenant
shall promptly apply for, obtain and maintain in good standing all governmental permits and
approvals required for the operation of the foregoing, at Subtenant’s sole expense.

	5.	 	Subject to the provisions of Section 9 of this Sublease, the reverse osmosis system (“RO
System”) at the Building shall be turned over as a fully functional unit for Subtenant’s use.
The RO System is located on the first floor, outside of the Subleased Premises. An employee
of Sublandlord shall escort any vendor who is to perform maintenance and repair on behalf of
Subtenant on the RO System.

	6.	 	Sublandlord shall turn over one generator as a fully functional unit for Subtenant’s use,
located in the parking lot adjacent to the Subleased Premises. Subtenant shall be responsible
during the Term, at Subtenant’s sole expense, for all maintenance and repairs to such
equipment. Subtenant shall promptly apply for, obtain and maintain in good standing all
governmental permits and approvals required for the operation of the foregoing, at Subtenant’s
sole expense.

	7.	 	Subject to the provisions of Section 9 of this Sublease, the pH neutralization system at the
Building shall be turned over as a fully functional unit for Subtenant’s use during the Term.

	8.	 	All other modifications are the responsibility of Subtenant, subject to the terms of this
Sublease.

4

LANDLORD CONSENT TO SUBLEASE

For $1.00 and other good and valuable consideration, the undersigned, Massachusetts Institute of
Technology, as Landlord (the “Landlord”) under a certain Lease dated as of August 26, 1993, as
amended by a First Amendment to Lease dated as of May 18, 1994; by a Second Amendment to Lease
dated as of January 9, 1996; by a Third Amendment to Lease dated as of June 12, 1996; by a Fourth
Amendment to Lease dated as of March 1, 1997; by a Fifth Amendment to Lease dated as of June
19,1997; by a Sixth Amendment to Lease dated as of January 29, 1999; by a Seventh Amendment to
Lease dated as of February 5, 1999; by an Eighth Amendment to Lease dated as of February 7, 2000;
and by a Lease Extension Agreement dated December 1, 2000 (the “Extension Agreement”) (hereinafter
collectively, as amended and extended, the “Prime Lease”), with Millennium Pharmaceuticals, Inc.,
as Tenant (the “Tenant”), with respect to the Premises consisting of approximately 181,022 square
feet of space located at 640 Memorial Drive, Cambridge, Massachusetts (the “Leased Premises”)
hereby consents, pursuant to Section 8 of the Extension Agreement, to the sublease by Tenant to
Altus Pharmaceuticals, Inc., as subtenant (the “Subtenant”) for approximately 72,935 rentable
square feet of space located on the second and third floors of the building located at 640 Memorial
Drive commencing upon Sublease execution, and terminating on or before December 31, 2008, provided
that Tenant shall remain liable to Landlord for the payment of all rent under the Lease and for the
full performance of the covenants and conditions of the Lease.

LANDLORD:

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

By:      

Its:      

Name:      

5EX-10.1

Exhibit 10.1

EXECUTION VERSION

AMENDMENT NO. 8

TO SECOND AMENDED AND RESTATED MASTER REPURCHASE AGREEMENT

Amendment No. 8, dated as of March 30, 2007 (this “Amendment”), among CREDIT SUISSE
FIRST BOSTON MORTGAGE CAPITAL LLC (the “Buyer”), FIELDSTONE MORTGAGE COMPANY (a
“Seller”) and FIELDSTONE INVESTMENT CORPORATION (a “Seller” and, together with
Fieldstone Mortgage Company, the “Sellers”).

RECITALS

The Buyer and the Sellers are parties to that certain Second Amended and Restated Master
Repurchase Agreement, dated as of March 31, 2005, as amended by that certain Amendment No. 1 to
Second Amended and Restated Master Repurchase Agreement, dated as of October 19, 2005, Amendment
No. 2 to Second Amended and Restated Master Repurchase Agreement, dated as of February 22, 2006,
Amendment No. 3 to Second Amended and Restated Master Repurchase Agreement, dated as of April 27,
2006, Amendment No. 4 to Second Amended and Restated Master Repurchase Agreement, dated as of
November 30, 2006, Amendment No. 5 to Second Amended and Restated Master Repurchase Agreement,
dated as of December 20, 2006, Amendment No. 6 to Second Amended and Restated Master Repurchase
Agreement, dated as of December 29, 2006, and Amendment No. 7 to Second Amended and Restated
Master Repurchase Agreement, dated as of January 31, 2007 (as the same may have been amended and
supplemented from time to time, the “Existing Repurchase Agreement” and as amended by this
Amendment, the “Repurchase Agreement”). Capitalized terms used but not otherwise defined
herein shall have the meanings given to them in the Existing Repurchase Agreement.

The Buyer and the Sellers have agreed, subject to the terms and conditions of this Amendment,
that the Existing Repurchase Agreement be amended to reflect certain agreed upon revisions to the
terms of the Existing Repurchase Agreement.

Accordingly, the Buyer and the Sellers hereby agree, in consideration of the mutual premises
and mutual obligations set forth herein, that the Existing Repurchase Agreement is hereby amended
as follows:

SECTION 1. First Amendment Period. For purposes of this Amendment, this Section
1 will be effective only for the period from and including March 30, 2007 through and including
the Termination Date (the “First Amendment Period”).

(i) Section 2 of the Existing Repurchase Agreement is hereby amended by
deleting the definitions of “Alt-A Mortgage Loan,” “Market Value” and “Maximum
Aggregate Purchase Price” in their entirety and replacing the same with the
following language, which amendment shall be effective solely during the First
Amendment Period:

““Alt-A Mortgage Loan” means a Mortgage Loan originated in
accordance with the criteria established by Buyer for Alt-A Mortgage Loans,
as determined by Buyer in its sole discretion and which has a FICO score of
at least 660.”

““Market Value” means, with respect to any Purchased Mortgage Loan as
of any date, the whole-loan servicing released fair market value of such Purchased
Mortgage Loan on such date as determined by Buyer (or an Affiliate thereof) in its
good faith discretion. Without limiting the generality of the foregoing, each
Seller acknowledges that the Market Value of a Purchased Mortgage Loan may be
reduced to zero by Buyer if:

(i) a material breach of a representation, warranty or covenant made by
any Seller in this Agreement with respect to such Purchased Mortgage Loan
has occurred and is continuing except, with respect to Repurchased Mortgage
Loans, those disclosed by such Seller and accepted by the Buyer pursuant to
clause (b) of the definition of Repurchased Mortgage Loan;

(ii) a First Payment Default occurs with respect to such Purchased
Mortgage Loan;

(iii) such Purchased Mortgage Loan has been released from the
possession of the Custodian under the Custodial Agreement (other than to a
Take-out Investor pursuant to a Bailee Letter) for a period in excess of ten
(10) calendar days;

(iv) such Purchased Mortgage Loan has been released from the possession
of the Custodian under the Custodial Agreement to a Take-out Investor
pursuant to a Bailee Letter for a period in excess of 45 calendar days;

(v) such Purchased Mortgage Loan has been subject to a Transaction for
a period of greater than (a) 90 days (unless the Mortgage Loan is an Aged
Loan or Repurchased Mortgage Loan) or (b) 120 days with respect to each Aged
90 Day Loan or Repurchased Mortgage Loan or (c) 180 days with respect to
each Aged 120 Day Loan or (c) 364 days with respect to each Aged 180 Day
Loan;

(vi) such Purchased Mortgage Loan is a Wet-Ink Mortgage Loan for which
the Wet-Ink Mortgage File has not been delivered to the Custodian on or
prior to the eighth Business Day after the related Purchase Date;

(vii) when the Purchase Price for such Purchased Mortgage Loan is added
to other Purchased Mortgage Loans, the aggregate Purchase Price of all
Wet-Ink Mortgage Loans that are Purchased Mortgage Loans exceeds (i) 40% of
the Maximum Aggregate Purchase Price for the first five Business Days and
the last five Business Days of each month or (ii) 30% of the Maximum
Aggregate Purchase Price for the remainder of the month;

(viii) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Sub-Prime Mortgage Loans that are Purchased Mortgage
Loans exceeds $280 million dollars;

(ix) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Second Lien Mortgage Loans and HELOCs that are
Purchased Mortgage Loans (other than Portfolio Second Lien Mortgage Loans)
exceeds $60 million dollars;

(x) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Aged 90 Day Loans and Aged 120 Day Loans, combined,
that are Purchased Mortgage Loans exceeds $200 million dollars;

(xi) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Negative Amortizations Loans exceeds $4 million;

(xii) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Portfolio Second Lien Mortgage Loans exceeds $150
million (the “Portfolio Second Lien Mortgage Loan Sublimit”);

(xiii) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Portfolio Second Lien Mortgage Loans that are
Delinquent Mortgage Loans exceeds 15% of the Portfolio Second Lien Mortgage
Loan Sublimit;

(xiv) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Delinquent Mortgage Loans (other than Portfolio Second
Lien Mortgage Loans and including Delinquent Mortgage Loans which may be
Repurchased Mortgage Loans) exceeds $20 million;

(xv) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Non-Performing Mortgage Loans (including
Non-Performing Mortgage Loans which may be Repurchased Mortgage Loans)
exceeds $15 million;

(xvi) when added to other Purchased Mortgage Loans, the aggregate
Purchase Price of all Aged 180 Day Loans, Repurchased Mortgage Loans,
Reperforming Mortgage Loans, Delinquent Mortgage Loans and Non-Performing
Mortgage Loans, combined, exceeds $35 million;

(xvii) such Purchased Mortgage Loan is no longer acceptable for
purchase by Buyer (or an Affiliate thereof) under any of the flow purchase
or conduit programs for which Sellers then have been approved due to a
Requirement of Law relating to consumer credit laws or otherwise.”

““Maximum Aggregate Purchase Price” means FOUR HUNDRED MILLION DOLLARS
($400,000,000).”

SECTION 2. For purposes of this Amendment, this Section 2 will be effective only for
the period from and including March 1, 2007 through and including the Termination Date (the
“Second Amendment Period,” and together with the First Amendment Period, the “Amendment
Periods”).

(i) Section 14(a) of the Existing Repurchase Agreement is hereby amended by
deleting it in its entirety and replacing it with the following language, which
amendment shall be effective solely during the Second Amendment Period:

“(a) Minimum Consolidated Adjusted Tangible Net Worth. The Sellers
shall maintain a Consolidated Adjusted Tangible Net Worth of at least
$275 million.”

(ii) Section 14(b) of the Existing Repurchase Agreement is hereby amended by
deleting it in its entirety and replacing it with the following language, which
amendment shall be effective solely during the Second Amendment Period:

“(b) Indebtedness to Consolidated Adjusted Tangible Net Worth Ratio.
The Sellers’ ratio of consolidated Indebtedness to Consolidated Adjusted
Tangible Net Worth shall not exceed 18:1.”

(iii) Section 14(f) of the Existing Repurchase Agreement is hereby amended by
deleting it in its entirety and replacing it with the following language, which
amendment shall be effective solely during the Second Amendment Period:

“(f) Maintenance of Profitability. [Reserved.]”

(iv) Section 14(ee) of the Existing Repurchase Agreement is hereby amended by
deleting it in its entirety and replacing it with the following language, which
amendment shall be effective solely during the Second Amendment Period:

“(ee) Non-Structured Securities Indebtedness to Consolidated Adjusted
Tangible Net Worth Ratio. The Sellers’ ratio of consolidated
Indebtedness less Structured Securities Debt to Consolidated Adjusted
Tangible Net Worth shall not exceed 7:1.”

(v) Section 14(ff) of the Existing Repurchase Agreement is hereby amended by
deleting it in its entirety and replacing it with the following language, which
amendment shall be effective solely during the Second Amendment Period:

“(ff) Maintenance of Liquidity. The Sellers shall maintain cash,
Cash Equivalents as well as unencumbered Mortgage Loans held for sale or
securitization of at least $20 million; provided, that for the purposes of
this requirement, unencumbered Mortgage Loans held for sale or
securitization shall represent an amount of not greater than $5 million (of
such $20 million).”

SECTION 3. Conditions Precedent. This Amendment shall become effective on, with
respect to Section 1, March 30, 2007 and, with respect to Section 2, March 1, 2007 (the
“Amendment Effective Dates”), subject to the satisfaction of the following conditions
precedent:

3.1 Delivered Documents. On the Amendment Effective Date, the Buyer shall have
received the following documents, each of which shall be satisfactory to the Buyer in form and
substance:

(a) this Amendment, executed and delivered by a duly authorized officer of the Buyer
and Sellers; and

(b) such other documents as the Buyer or counsel to the Buyer may reasonably request.

SECTION 4. Representations and Warranties. Each of the Sellers hereby represents and
warrants to the Buyer that they are in compliance with all the terms and provisions set forth in
the Repurchase Agreement on their part to be observed or performed, and that no Event of Default
has occurred or is continuing, and hereby confirm and reaffirm the representations and warranties
contained in Section 13 of the Existing Repurchase Agreement.

SECTION 5. Limited Effect. Except as expressly amended and modified by this
Amendment, the Repurchase Agreement shall continue to be, and shall remain, in full force and
effect in accordance with its terms. The amendments set forth in Section 1 and Section 2 of this
Amendment shall expire upon the expiration of the applicable Amendment Period at which time the
terms of the Existing Repurchase Agreement shall revert to that set forth in the Existing
Repurchase Agreement and be applied on a prospective basis thereafter. Other than as expressly set
forth herein, the execution of this Amendment by the Buyer shall not operate as a waiver of any of
its rights, powers or privileges under the Repurchase Agreement or any other Program Agreement,
including without limitation, any rights, powers or privileges relating to other existing or future
breaches of, or Defaults or Events of Default under, the Repurchase Agreement or any other Program
Agreement (whether the same or of a similar nature as the breaches identified herein or otherwise)
except as expressly set forth herein.

SECTION 6. Counterparts. This Amendment may be executed by each of the parties hereto
on any number of separate counterparts, each of which shall be an original and all of which taken
together shall constitute one and the same instrument.

SECTION 7. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REFERENCE TO THE CHOICE OF LAW
PROVISIONS THEREOF.

[SIGNATURE PAGE FOLLOWS]

1

IN WITNESS WHEREOF, the parties have caused their names to be signed hereto by their
respective officers thereunto duly authorized as of the day and year first above written.

Buyer: CREDIT SUISSE FIRST BOSTON MORTGAGE CAPITAL LLC,
as Buyer

By: /s/ A. Adam Loskove

Name: A. Adam Loskove

Title: Vice President

Seller: FIELDSTONE MORTGAGE COMPANY, as Seller

By: /s/ Mark C. Krebs

Name: Mark C. Krebs

Title: Sr. Vice President & Treasurer

Seller: FIELDSTONE INVESTMENT CORPORATION, as Seller

By: /s/ Mark C. Krebs

Name: Mark C. Krebs

Title: Sr. Vice President & Treasurer

2

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